where do you cross over your ht setup

hello. i am just wondering where everybody else crosses over there ht system at. thx says 80hz with speakers set to small. some speaker co. say set front mains at 60hz the rest set at 80hz set to small. i even read one speaker co. in a reveiw say 20-30hz and set speakers to large. if you are driving a full range speaker system with a stand alone powered sub what do you fellow audiogoners find best. also when using a spl meter do you set up your system at 75? thanks.
I'm using stand mounted monitors, but I find that in the 60-65 range to be the best. 80 is too high.

I have come to the conclusion that SW/Main crossover should be set based on what your particular SW can do rather than what your Mains can do. Any decent Main speaker ought to get down to 40 Hz or so, but doing so may adversely affect the Mid bass range, 70Hz up to about 200 Hz. Give the Mains a break, and set the X/O to 80-100 Hz. Try it that way first. If you don't think the SW can hack it, then go lower.
My mains are good to 22Hz so I have them set to large and only use the sub for the LFE channel. If I set the mains to small (XO @ 80Hz), and have the sub handle both the front and LFE duties, the upper bass/lower mid sounds kind of anemic.
Alright, in all humbleness and humility here, I'm going to pipe in here, adressing many of the views expressed here on the subject. I've built many-a-high-end custom theater over the last 10 years, and have probably hooked up more systems than 99.99% of the people ever to post on this sight. I do consider myself quite accomplished and dedicated regarding making systems sound even to world class standards, and have just plain been an HT junkie for many years, as well as high end guy all around. Needless to say, i like to think I'm somewhat the expert on making things sound better than anyone I've meet when it comes to putting systems together correctly.
Anyway, my input on the whole "which crossover setting is best" issue is that, yes unfortunately, it does often depend on a lot of varriables you have to work with!
I'll start with some considerations that are really mandatory, and which in a round about way get to the issue here none-the-less.
First, You really need enough subwoofer(s) or ACTIVE bass woofers for the room/system you're putting together! This will have a lot to do with what bass is going where, in regards to proper bass output. That being said, I find most people "under-sub" in modest sized rooms, or they have their(likely) "underpowered/undersized" sub playing higher than it comfortably can! The answer there is either to get more sub(s)(and learn how to place and set them up to be coherent and balanced in the system their in), or place the smaller sub towards/in the corner to get more boost and efficiency from it by letting the room boundaries help(considering EQ'ing in that situation is a big plus indeed!).
Now, let's say you have that issue adressed, and have enough(very necessary) sub(s) for your room, there are other concerns that are magnified by the fact that most people out there are at the very least using lower powered receivers driving passive speakers! But even when considering separates driving even larger FULL RANGE monitors in most peoples systems, still, the inefficiency in most any amp to drive most lower efficiency/sensitivity home speaker makes it even that much more critical to do some BASS MANAGEMENT AND PROPER ALLOCATION!
To simplify, I find that it becomes mostly mandatory to take the bass and dirrect it where a more capable ACTIVE SUBWOOFER(S) can better handle the very demanding bass that's recorded on these digital movies!
There are many many many people out there who are running there FULL RANGE SPEAKERS as LARGE on their pre/pro's, quite contrary to what THX dictates. Yes, it's loosened up a bit over the years, but WHAT WORKS WORKS! (See: "if it ain't broke, don't fix it!"). THX spent hundreds of thousands of hours finding out what works best, and there's a reason for their 80hz crossover! Even with very high sensitivity passive speakers (like horn jobbies), getting proper control over the bass driver is better handled by an ACTIVE SPEAKER!(OR WOOFER RATHER)! letting your passive monitors(no matter the size) play only a the top bass portion for speed and ease of handling by your amp/receiver/whatever, and letting the subs handle bellow 80hz, makes for a much more dynamic potential in a sound system!(note: they even use this setting in large commercial theater!). So, in short, if you do run most domestic home speakers full range passivly, and just have the sub "filling in the bottom octave", you're most likely encountering mushy, slow, distorted, bloated, rather "less dynamic" bass response, all things being equal...that's what I tend to find. And I've dealt with just about everything you can imagine, in every setting!
Now the exceptions to this would be where just don't have dedicated woof's, and need to do full range from your speakers, or you are running much more efficient ACTIVE SPEAKERS!(I.E, powered subs built in already, and they're big enough to fill the room with the bass it can handle).
I think if people will just take the time (or hire someone) to properly set up their systems, crossover at 80hz, get the speakers in the right spot for coupling with the room at that 80hz crossover(including subs), and have enough sub to hanle the bass in the room it's going into, they would have some of the most amazingly fast, dynamic, powerefull, hardhitting, coherent, and solid bass they could imagine!!!
Again, I find most people problems stem from first, poor set up, room, and tweeking/calibrating, and second ill conceived equip!
Now, to adress many peoples findings(especially in smaller rooms with lower ceilings, or even very very tall ceilings) where they get a rather weeker bass problem at the "crossover" setting from their subs and satalites, what that problem is a "poor coupling" with the speakers (including sub) at that frequency in the room!!!(This is very often the problem many people get with smaller THX SEALED BOX MONITORS, that need to be carefully placed to play down to 80hz in a room) If you just get those speakers COUPLING WELL at the CRUCIAL CROSSOVER POINT, you will have no such problem!(note: this is easier for most people to get in extremely large acoustic spaces, such as commercial theaters and giant rooms!). Still, if you just play your test tones and/or fiddle around with speaker placement and listening, you can solve this issue! At first try, many poeple will stick their speakers in ANY OLD SPOT, and find they don't sound good crossed over in certain settings! So, they lower the crossover till they get more bass. Again, if you just get the speakers to couple to the room correctly at 80hz, you'll have no such issues!(i.e, "the hole in the bass syndrom"!) Of course the sub needs to play strongly right up near 80hz as well.
The last point brings another issue, and that's that your subs should play strongly up to 80hz efficienltly, and blend well! However, I find most subs, when set up carefully, can blend up that high, as long as you can blend em coherently with your speakers.
Thankfully, most powered subs are efficient enough, and fast enough up at 80hz to do the trick. Blending the sub with the mains(at the very least, all though not the last word on perfect blend with ALL THE SPEAKERS) up front can handle any of the coherence, localization issues most might encounter as well(then you gotta balance, equalize and tweek!)
Still, in a round about way, as you can tell, I gleen towards tHX's recommendations when it comes to bass managment! I think this set up gets too bad of a rap with most novices because they know NOTHING ABOUT PROPER SPEAKER SET UP IN A ROOM!!!! They stick speakers where they THINK THEY SHOULD GO, instead of where they sound the best!(bass is the single most placement critical element for speaker and seating placment!) I've played way way too long with many other set-up's, and however it does sometimes vary depending on gear/room/system, etc. Still, not deviating from this in a proper set up system(sadly, most peoples system never is) is the best way to go with most all combinations of gear and room settings most people will ever deal with!
Receiver/sub/sat systems, floor standing speakers/receiver/sub systems, even separates/full range/sub systems will all have the best potential dynamic range most offten if you set em up right in the room, and have enough ACTIVE SUBS to hanle the bass chores! Trying to get more bass being handled by passive speakers playing full range from each channel, will yeild a less controlled, fast, and authoritative bass sound to your sytem...overall, weaker! That's what I find anyway...too each is own however.
I, as an audiophile also, know far too many people who still insist on running their audiphile full range speakers, well, full range for movies with no sub!!! It's never as good, trust me. Yeah, your sub may not be as fast for less dynamically demanding music material as is the bass woofers in your expensive audiophile main speakers, but then those can't handle the EXTREMELY demanding dynamic digital bass recorded in such movies as THE HULK, Lord of Rings, Matrix, Dare Devil, whatever!
Try what THX recommends, and do what I recommended, and I think there's reall no way you can't like what you hear!..especially all you people running receivers with full range speakers!...really gotta cross over...your system will become that much more efficient and dynamic
I was going to skip your thread and thought you were full of hot air until I read your whole post.How cool it was...let me add,
I think what needs to be addressed is a sub which is managing LFE and the bass from five to six other channels needs to be a bear.It needs to be seven subs in one.So where do we go from there.If you are interested in getting true deep down bass you better be willing to build your own or spend huge bucks on manufactured particleboard boxes with crappy plate amps and drivers that are so taxed out at modest levels the whole system suffers.
Building your own sub is the only way to go.First pick a world class driver from Adire.Brahma,Tumult ect.Then get yourself mono amps like Adcom GFA 555mkII's (one for each driver)Then get a good parametric eq like a Behringer 1124p . Now you need a cabinet maker that can build you some two inch thick MDF cabinets to your specs.Stuff those bad boys with some pink owens corning and sit down and listen.
Bass is expensive and there are no if,ands or buts.I have tryed every combination and it all lead to DIY in the sub dept.
You will need to get a test disc or better yet a signal generator.A sound pressure meter and a big pad of scrap paper.I don't care what size your room is and who gave you the numbers but it has at least two room modes and a bunch of harmonics that go along with them.Start to sweep the freq. up and down, up and down,back and forth, until you could hear those damn humps in your sleep.One by one you will start to kill those damn humps(roommodes) until the sweeps yeild a +3db/-3db freq. response.If you can get better go for it.Oh yeh people have gotten better freq. response but that works for me.
Exertfluffer is right on and I had to add to his reply.I'm sorry if my post insults your sub but I sold manufacture subs and one or two stepped up to the plate And for that price I built two that crush them all.
It took me twenty years to find all the parts but what I learned along the way was worth it all.Good luck Goners!!
Theaterhome, I think what exertfluffer is saying in his thread is what I have been telling you to do. Stop reading those Audio Magazines.
I use the THX 80htz. I don not want to blow up my $4000 Vienna Acoustics speakers. The sub. can take all the punishmint the Hulk can dish out. Set the speakers for small and use the spl meter to set up the room. I have found the the big bass slam actually gets a little old after a while and listen to movies at a lower volume than when the HT was new.
Have fun
Like all things in life ,listen to all and do what makes sense.Audio mags have a wealth of info.Try not to get all caught up in the tech race for new gear.The guide to hometheater has great articles.Learning involves first putting a lock on your wallet and start reading all you can.This forum is a perfect example.Good luck gonners
First I must say everything im writing here assumes one has proper amplification for each channel in his system. It also assumes sustained SPL levels no greater than what each channel is capable of.

Crossing over at standards designed around large cinema's seating 100's of people simply has no place in HT. Crossing over at 80hz or higher when you have speakers capable of useful output much lower than this is a complete waste. You lose any stereo or surround low bass imaging mixed into the soundtrack and likely overwork your subwoofer. Forget all the THX/Dolby mumbo jumbo right now. Dont let people tell you that you low bass is non-directional. Its complete nonsense for many reasons. Sure, perhaps a 20hz note is near impossible to localize but 30hz and up this isn't completely true. Without getting into a huge discussion regarding low bass I will just offer some advice based on my experience.

Maximize the low bass output of each of your HT channels. This requires a processor that was not lazily designed around cinema standards and allows low enough settings for even full range loudspeakers. In my case I crossover my mains at 25hz, my center at 35hz, and my surrounds at 40hz. This allows each channel to operate to its potential while maintaining the channel integrity of the mix. This also protects the speakers with the processors built in high-slope crossovers by relieving them from bass duties they aren't equipped to handle.

My ideal system is 5 - 7 honest full range channels plus a dedicated LFE sub (or two) in a room designed around the system. This is simply not practical. Another way would be to integrate subwoofers into each channel and run full range. This requires a setup method like Vandersteen recommends with filters to roll off the signal before it gets to the amp (protects the speakers) and a subwoofer that compensates precisely for the filter. Although the results can be excellent, having 6 subwoofers and the wiring/filters needed for this would present spaghetti nightmares in my room.

Where does that leave us? Leaves me smiling. Leaves some of you wishing you had a processor that allows you to maximize the low bass potential of each your HT channels.

Crossing over at 80hz in all ch. allows you to EQ one sub and avoid running EQ's in the mains.I have heard many people try the full range game and the only time it worked was in a room close to 20feet by thirty feet with a twelve foot ceiling.With that said,full range for two ch.and everything to the sub in HT.
Forget all the THX/Dolby mumbo jumbo right now?
Crossing over at all those levels would be a pain in the...
If you need to EQ a single sub because of room response or poor speaker selection and placement then go for it. You totally destroy the DD or DTS mix in the process.

I can understand crossing over surrounds at 80 - 120 if the surrounds aren't designed for near or on wall operation. In that case the bloated bass could be a problem. I guess the same applies with poor placement and selection for mains. If you cant let the speakers breath like they need to for linear response then cut em off!

Flemke, setting the crossover settings in a HT processor is hard for you? Sorry to hear that. The interface on my processor is quite simple.

I will not submit to specs based on compression horns surrounding a 200 seat cinema where loudness and shock value are the primary criteria. 80 - 120 hz works for cheap cinema speakers. 80 - 120 hz works for the small HT in a box type systems. It's nothing more than an "easy way out" if placement options are limited, or if one doesnt wish to take the time to properly select and setup speakers for the room.

My HT mains are also my 2ch. mains. They are flat to 30hz (IRR) and tail down 9db at 20hz. Why on earth would I want to cut them off at 80hz??? This is crazy THX cinema mumbo jumbo. Hook line and sinker..
Like I said before.ALL rooms have modes.If you don't do something about them with some type of parametric in the bass all you hear is the mode because it is 15-20db higher than the rest of the signal.If you choose to ignore this basic principle than fine, go ahead and listen to 32hz 15db higher than the rest of the movie sound track.Why are there so many blackboxes coming out to cure such problems.All i'm saying is to sum the bass to a capable sub @80hz you eleminate the problematic room mode effect by only EQing one sub.The empierical thinking that eq's are ruining your sound is as old fashion as two ch. stereo.Holding on to old idea's due to a lack of education is purely that.In the perfect world fullrange surround with a dedicated LFE sub is what would be somewhat the holy grail.This experiment has been done by better than you and I with more problems than they could count.Go back to your two ch. dinosour and 1950's EQ fear and let people learn and enjoy the knowledge they learn here.I love this forum!
You're kidding right? I have no problems with EQ's. Not sure where you gathered that from. I'm also not sure what "old ideas" you think I'm holding on to.

If you can get linear response to 20hz with your mains why cut them off at 80hz? If you can get linear response to 35hz with your surrounds why cut them off at 80hz? Can you answer this in any reasonable way?
Vedric...Take off the grill and look at what your woofer is doing while it reproduces 20 Hz (or even 30 Hz). Do you want that going on while it is trying to reproduce the critical 80-800 Hz range? Same goes for the power amp.
no room is linear.no room is linear.period.your gear might be linear , but your room is not and i would be willing to bet dollars to dougnuts that your room modes are there and you have yet to address them or are willing to do anything about them.what we are trying to say is that if your perfect room is indeed perfect keep on keepin'on.i doubt it is because they don't exist my friend.it is easier to eq a single sub than put up with the room modes from five separate locations.do the math, it is impossible and denial is your worst enemy.i would love to go back and forth but this will be my last post and as Bruce Williams says,"I wish you well"
You guys are nuts! :)

Eldartford first.. I dont think you have followed what ive said very closely. I do crossover my speakers just not at THX cinema standard 80hz or higher. Its a waste if you have useful linear output below that point.

Kgveteran I can tell you a thousand times I have fairly flat response to 30hz (-2db'ish) with my mains. Im down 4-5db'ish at 25hz. I have a 2-3db peak around 60hz but this is a voicing issue. What a waste to cut them off! I also am most certainly NOT sitting in the middle of a room mode. If you wish snub your nose and call me a liar its no skin off my back. Keep on keeping on and I will as well, enjoying proper placement of 5 channel mixes all the way.

Vedric...I read your earlier post. Sorry, but I believe that a 25Hz crossover (mains) is just about the same as no crossover. 35 Hz (center) and 40 Hz rears barely qualify as a X/O (IMHO). Remember that no crossover is a complete cutoff, and there is significant signal below the nominal X/O frequency.

You argue that LF capability of the mains should not be "wasted". OK. Why waste the HF capability of your SW?(if you can call 80 Hz HF). If your SW can't run up to 150 Hz or so without difficulty you need a different SW.
Eldartford, simple answer. Proper directionality (localization) of low frequency information mixed into the 5 channel soundtrack. Throwing everything to a sub located in a corner ruins the mix. If there is a 70hz buzz in right rear channel I want it to come from the right rear channel!
OK,so you do cross over but not all at 80hz.You have a small issue at 60hz.What size is your room ? What are your mains ? What is your center ? What are your surrounds ? What sub are you using ? Just wondering.
In quickly glancing through these Kgveteran/Vedric responses, I must say I more agree with Kgveteran. However, from a CRITICAL flat/even frequecy response standpoint, I understand Vedric's point of simply getting your speakers set up properly in the first place, thus assumedly eliminating much of the need EQ in the first place, possilbly ading some negatives to the sonic purity. However, in all practicallity, and since 99.999% of the people can't get their speakers set up properly from lack of knowledge(or worse, the room is too small to find adequate placement for flat response) makes Kgveteran's standpoint more valid and practical motly! It's easier, simply refering to balancing the speakers frequency response-wise, to EQ one sub, and not have to worry as much about flat response from all your satalites/speakers!...thus allowing you to balance the bass bellow 80hz out with placement and EQ alone! Still, you'll need to focus on speaker placment, but it give you much more options this way! Case in point:
You've got a small room acoustically, like most, and placing full range speakers in a small to medium room,un-EQ'd, will make for boomy, bloated, one note, lack of pitch and dynamic range sounding bass every time inthese rooms!...unless you introduce unpractical(often) placment options out in the middle of that small room, and/or EQ'ing extensively for the seating possitions! This is a major common problem in most all small/medium acoustic spaces! Now, in Vedcric's deffense, LARGE ROOMS (like, yes, 20x30x9 or better) you can get away with more flexibilt of placement usin full range speakers even!!! However most people don't have such luxury.
Case in point, my last custom theater room I set up for a client, involved a room that was 17(21 at some points)x14.5x9. I was using all 2 way sealed DiApplito HT monitors for mains/center, plus smaller Bipoles and a sub rounding the 5.1 system out. THERE WERE SOOOOOOO many room mode challenges in that smallish room, that I ended up having to EQ the whole system out(this is better in a digital system using internal Digital EQ's if you can mind you, unless you spend big bucks on many higher expense EQ's!!!, like Rives EQ), since the seating options where limited in this case, not to mention speaker placement limitations.
So, responding to Vedric's assumption regarding peoples need to simply set the speakers up right in the first place, I find it doesn't MOSTLY end up being an option for most, for many reasons!!! In this case, being able to set speakers up closer to walls/boundaries, in cabinets, near big TV's, whatever, becomes much more practical when setting speakers to only play above 80hz or so, and EQing out a single(or better, multiple subs) instead!!!!
Case in point again: If anyone went to this past year's Hifi expo in San Francisco, There were at least 6 or more rooms in the hotel that were using Rives Audio's Parametric EQ in them! The sound difference was tremendous! Granted, this EQ cost's thousands for a high end system, but you need to do something to get the modes down in these smaller acoustic spaces, like THE VAST MAJORITY of smaller domestic rooms we mostly see consumers having to use at home!!!
In large acoustic spaces like commercial theaters, placment isn't a problem at all!...as you can put speakers most anywhere and mostly be garanted flat response because of the tight modal distribution in such large spaces...you don't have that luxury in small house rooms, which is what we mostly live in. Thus, in small rooms, speaker placement and, often, EQing become necessary for optimal sound!
Now, back to the issue regarding bass distribution for efficiency, coherency, dynamic potential, speed, and transparncy, and practicality from an "option" standpoint fo distribution, there are other considerations here.
Second, regarding Vedric's statement that your WASTING USEFUL BASS OUTPUT FROM YOUR OTHERWISE CAPABLE FULL RANGE SPEAKERS by setting 80hz cross for your speakers, this doesn't work mostly!!! AGain, THX figured this out because passive speakers can't properly deal with the 5-10x's as demanding bass mixed into these soundracks!(music is much less dynamic mostly, as music doensn't have explosions mixed in)
I've seen/heared it time and time and time again!...people using their full range speakers (passive types going through a rather inefficient passive crossover built in) full range for movies! Blown woofers and fried tweeters, distorted mushed out bass from the speakers, and generally muddy and non-dynamic inpactfull bass is largely the results this gets!...sorry to say, but I've worked in 2 large audio chain stores, and 4 high end audio stores over the last 10 years now, and unless your using speakers with large powered subs built in or MARGINALLY high efficiency Klipsch type horn speakers, playing full range through all your tower speakers for movies SUCKS!!! You think you're wasting the bass potential by playing them as "small", but your not! And, yes, all the bass is being mixed down into your sub when you do this, but it's still much better do to the limitation of your speakers!
I've played full range dynamic movies, at all volume levels and intensities, with evey kind of speaker you can immagine! And, by far, taking the rather inefficient bass load of of these passive speaker set-up's is the way to go for sure! If you're worried about lossing bass in teh room, get MORE ACTIVE SUBS!!!! Those passive, even full range speakers need to only be trying to reproduce the rather EASY 80hz and above info dynamically!...YES!
The reason people get distortion and blown speakrs running these action movies on DVD through their towers full range is largely do to a poor distribution of power through their passively crossed over speaker designs, and in-efficient amps in their recievers and underpowered poweramps! So, from a less dynamically demanding bass standpoint when playing most music through your main speakers full range, this problem isn't as bad for most people. yes, you can get fast, cohrerent, dynamic enough sounding bass from full range speakers for this application, I conceed for the most part. But, play techno, hard rock, rap, heavy R&B/Hip-hop, whatever through this same set up and listen to your speakers bass go all to hell!..they'll scream for relief and more power! In short, you'll either distort your woofers, get washed out mush, or hear slopy washed out bass! My worst fear is blowing drivers! If you don't think so, just put on some of this heavy techno, or rap and hear your systems inefficiency! If you've got powered speakers with big woofers, or much more efficient horn speakers(even pro audio types), this is much less of an issue. Still, for all practicality, if you can get a crossover at 80hz between a speaker and passive sub, the systems dynamic potential will come alive with that effectively "bi-amped" set up!!!(i.e, sub's amp and main amp combined).
Yes, I find that only in the speakers that are using active bass woofers of large enough size, can you get USEFUL bass that's controled enough not to blow woofers for DD/DTS movies! ACtually, I've heard Linn's active speakrs played full range for movies on occasions. And, even though the sound was more dynamic by far than any other passive speakers(mostly home audio) sounded full range, the bass was still distoring quite a bit when pushed at THX level! Definitely sounded better crossed over to a larger powered 1000 watt sub!(infact, commercial set up's use 1000 watt/ch amps to drive the bass woofers for a reason1!!!...just like Russ Herschelmann of HT/STereophile/AVInteriors uses in all his full blow theaters!).
It all comes down to efficiency, flexibility, control, dynamics, and accuracy of sound when it comes to bass distribution. I've played around with all the processors(in board and out) that offer flexibility from 20hz to 250hz for crossover setting for HT purposes. And, I like the 80hz setting, because I know how it works and how to work with it! I'm not saying you can't get good results by not using this, but it all becomes a trade-off. And for movies, the trade-off of potential dynamics and efficiency is not one that should be given up!...at any volume level!. I say this, and I'm a two channel audio guy as well.
I've argued with many audiophile who use their large Dunlavy's, Wilson's, JM Utopia's Even Avantgards or whatever, and even less expensive PSB's, NHT's, B&w's, whatever, about running full range for HT! I've tried all those scenarios, with all kinds of amps and set-up's. Infact, if you call all the high end speaker makers and tell em you're going to run HT at anywhere near THX levels through THEIR SPEAKERS, they'll tell ya you might consider a powered sub and the "SMALL" SETTING ON YOUR PRE PRO! Justr Ask Thiel, Wilson, Martin logan, B&W, whoever! I know, I've not only sold all these people products, but I've talked with their people extensively!
Now, there are those companies who set up speakers to be played full range for movies, and I think Def Tech and the powered NHT's and such are two of them! Yes, Klipsch makes some very large passive horn speakers that will do much better here than most standard non-powered passives full range for movies. But The likes of the active woofered speakers like Def Tech's and NHT VT3 system have advantages of having active woofers on their large bass drivers! IN these cases, bass distribution from an efficiency stand point becomes less of an issue. I've even owned the INfinity Prelude composition and MTS full range ACTIVE-woofered speakers, and so I know this is the case, including
Def TEch BP2000's! So, I know what I'm talking here. In large rooms, those powered speakers can handle the bass for sure!..and they do it well. This isn't the case with large passive audiphile designs for the most. You NEED A POWERED SUB!..OR MORE!!!
So, again, M&K whith their powered sub/sat systems are doing it righ for movies in homes! I like their stuff as well. You can use, yes, your audiphile speakers and a sub, but you gotta cross em over at 80 and set up right! Large rooms get more freedom of speaker placement, for that option. For most people however, I'd stick with running full range for passive music, and crossover for rock/HT dubites every time! Yes, higherend horn speakers with active woofers like AVantgard's can play full range if need be for movies, but most other high ender's can't handle the truth for movies!
It's all good. But THX didn't spend a small fortune trying to sort all this out for nothing! Many audiophile think their old 2 channel full range stereo approach to DD/DTS/THX movies can be adressed by thier outdated approach/set-up's! But this isn't the case. Just go slap in "The Hulk" on DVD and play it about 5 db bellow THX level, try full range through your speakers vs. "small" with a powered sub(s), and see what your ears/speakers think??? If you havn't blown your speakers up playing em full range, and you like the sound, then there you are!....
I think you'll rethink after you've done it just once.
Have fun
I'd like to add more Caviats here, and that's that, as far as domestic home theater speakers offerings go, choices of speakers that I find you can use "lower crossover settings" for on your pre/pro or receivers, include those that have more efficiency and control in the bass reigion, but that don't have big enough woofers to handle the WHOLE LOWER BASS SPECTRUM on their own. Speakers like smaller "powered towers", like Def Tech's smaller BP2004/2006's and such are good candidates, in big enough rooms, to have the crossover setting at possibly 40-65hz, rather than 80hz! The reason for this is that the powered amp in the speakers that's responsible for handling the bass is capable of exerting better control than passive designs in the lower bass! Yet, the small woofers these speaker have can use some assistance from larger woofers down lower! Still, like the Linn speakers, these active choices offer some more flexibilty options.
Now, again, you can get better/more adequate results if you use lower crossover points in your HT processor with much much more efficient sensitive passive speakers, like Pro Audio market offers, but that doesn't equate to most peoples home audio chioces. Case in point, you can go over to Sam Ash and pick up some JBL or EV speaekrs that are over 100db sensitive at 1db/watt! These horn speakers will hit hard down lower playing full range, but even those still sound better for movies if you cross em over(effectively bi-amping your system) at 80hz and introduce dedicated active woofers into the system, like THX recommends. Still, getting more active woofers into the system greatly extends the dynamic range of the system. But trying to accomplish that by utilizing the bass into the mains has trade-off and negetive effects that aren't practical in the end for a full blown hT set up.
Yet, for the record, pro audio speakers aren't as refined if you need to listen to a lot of casual music. Home market offeres more refinement of sound, if sacrificing dynamic range. This is where sub/sat combo's become more viable for the home market as a solution.
Vedric...Agreed that LF from a SW has directional aspects which should be preserved. (Unless you are playing an LP where the LF has already been mixed to mono). I think that every speaker should have its own SW: at least 2, and I have 3. However, I thought that this post was about crossover frequency.
OK.I give.This has been the most fun yet.I guess my small room is a problem and or has multiple problems and all the other rooms have or had problems and the only house calls are from clients with problematic rooms.Cross over freq. is room dependent and not speaker dependent.Problem rooms are easier solved with a higher cross over freq.Thus allowing one to adjust one channel.So.....we are all right!
I'd like to add that in addition to the importance of room acoustics/speaker placement discussed above, it is also extremely important to avoid "double filtering" the audio signals to your active sub. The results can be very unpredictable if you feed a sub's filtered line-level input from a processor's filtered LFE output. (Nearly ALL receivers/processor's LFE outputs are filtered). This can either cause the dreaded bass "suckout" or "boom" even if the sub is positioned properly in the room. This is especially problematic when you set the active sub's crossover frequency close to the frequency setting in the processor. The interaction of the two filters, which may have very different characteristics (different slope, etc.), in the signal path can wreak havoc with the sound.

Many higher-quality subs offer an unfiltered line-level input for exactly this reason. It's usually labeled something like "LFE-in" or similar. Or there may be a "bypass" toggle switch you can set to bypass the sub's built-in crossover.

If your sub lacks the unfiltered input and you are going to use your processor to set the crossover point for LFE, you should turn the sub's crossover as high as it will go.

My $.02 ;)
John Z, I do exactly what you say not to, and I am not 100% satisfied with how my Sub sounds. Although 100% satisfied with audio is an oxymoron, especially with Subs. Anywho, can you or someone else, explain the technical reason the two filters will interact poorly.

I am going to tinker with cabling tonight and I intend to try your recommendations, but I would like a technical foundation on which to ponder. Thanks in advance.
Yeah you can run into problems if you stack crossovers or interstect them. It's often best to set the crossover on the sub as high as possible if you don't have a bypass, and are using the processors internal crossover. If you like the sound you are hearing "distortion", then there you are!
If it ain't broke, don't fix it!
Still, there are numberous articles by industry professionals that say you shouldn't do what you're doing in general. Still, tinkering and tweeking is ultimatly where it's at, as system set ups and equipment matching will have a great deal to do with all this. Still, what I find is that the single greatest areas or down falls for most is both speaker placment, seating placment, and system set up paramaters and tweeking!...not to mention other room acoustics problems. All that is followed by poor gear selection for appropriate needs being a distant last!
Good luck
For lack of a better word, I fiddled around with the setup last night. Changing around the settings for large and small, Xovers (5hz increments), and the Sub Xover bypass.

The jury is out on HT, but, the bass did improve with multi-channel music when I, set only the rear speakers to "small," selected 80hz as the Xover point, and bypassed the Subs internal Xover.

I am still curious about the technicalities. I would imagine that like most everything else in audio, less is more. A signal running through two Xovers is unnecessary and doubles the potential to degrade the sound quality. Not to mention slope differential (db per octave) or overlap.

Thanks for the tips.
Distortion...Every crossover except 6 dB/octive is a cascade of several filters. The common 24dB/octive slope used with electronic crossovers is four stages. Guess how you make a 48 dB/octive X/O.

There is nothing evil about "stacking" two crossovers, however the very steep crossover may not be desirable, and if the two X/O are set to different frequencies things could get messy.
Eldartford, that makes sense. I can see were two Xovers set at different points with different slopes would interact and possibly get messy. Thanks much for the explanation of Xovers, I didnt know that.
Distortion- I'm glad to hear you heard a difference trying it this way. It never hurts to experiment!

It's just good advice I wanted to pass along that I came across on Polk Audio's website. Although I do not use Polk speakers or a Polk Sub, the information provided there applies to any speaker setup. In fact, Polk asserts that connecting your active sub via line-level cables can often sound worse than a speaker-level connection unless you do it right. This may sound counterintuitive, but his reasoning is that the speaker-level connection will avoid the filtered LFE output of most pre/pros and that any cable effects introduced are much less of a degradation to the audio signal than the double filtering of multiple crossovers in the signal path. Getting a good "blend" between your sub and mains is only made more difficult if the crossover point for LFE output is fixed at something like 80 or 100hz, as in many mid-level A/V receivers.

You can find the info at www.polkaudio.com, click on "Home Audio" then "Setting up a home theater system" under the FAQ's & Advice section. You can find a fairly detailed explanation of why it's bad to "stack" filters there as well. Check it out.. it's a good read even for seasoned audiophiles.
In responding to "john Z's" comments regarding Polks info, and the general opinion on running "line level" vs. "speaker level" needs some more explanation I think, as it's a very important consideration.
First, I think that connecting your active sub via "speaker level connection" in a purely music system(probably mostly 2 channel), can often work quite well and, I think, is often a viable consideration for best results! You can often avoid some of the "POTENTIAL" trouble situations you may encounter this way, some of which where discussed previously by John Z. I ran my high end 2 channel monitor set up that way for a very long time, using my SF Minima Amators driven full range (only play down to about 45 hz+/-) with a 2 channel set up, while using a powered sub connected "speaker level", thus using the subs own internal cross over to blend the sat' with the sub....and the results were tremendous for my AVERAGE music listening needs! The blend sounded excellent, no phase issues, or weird anomolies, etc.
The only down side to that system set up, was that very dynamically challenging music material, like Techno, rap(if you listen), heavy percussion, some new-world, hard rock, giant scale orchestral, etc, will distort the woofers in your small speakers this way!...as the mains are being driven full range, and most can't handle(as I mentioned in all the other posts I had) truely deep demanding bass info so well!(refering to even most full range passive speaker monitors). REally, ALL THE DEEP BASS INFO needs to be handled by the POWERED BASS WOOFER! That's been my extensive experience anyway. Heck, even the older NHT VT2 towerers, bigger Klipsch, and higher end Dunlavy's that were known for excellent bass on their own can't handle some stuff, MOST ESPECIALLY DD/DTS movie stuff on their own!...you gottta get the powered subs involved somehow.
Anyway, without going "there" to much, back to my point...
..So really, the "speaker level connection" to your powered sub, letting the mains run full range, and crossing over the sub internally can often work in many situations that some might encounter. STILL, seing that were talking about most people here who are using 5.1/7.1 surround sound systems, involving "summing the bass" into the sub(for one issue), and/or letting the mains handle the bass, and or with the sub, this "passive speaker connnection" posses some problems.
For instance, when you're "summing your 5.1(or better) bass info, in one case, into your "main L/R speakers", and connecting a sub via "speaker level" (connected to your main speakers, or amp's binding posts), thus making the sub play the same bass info that's being mixed into your main L/R's, you're making your mains play FULL RANGE BASS INFO which they really can't properly handle!..even if the powered sub is assisting with the demanding bass dubties for DD/DTS movie applications! Which I stated earlier, becomes a much more appropriately apt job for the POWERED SUB WOOFER! So, in this situation, the mains are really straining(also straining most peoples amps, especially receiver's amp sections, causing dynamic lose throughout the system) trying to reproduce very demanding bass info, not to mention distorting! So in this set up, where the mains are driving full range "in paralell" with the powered sub(even though crossed over in the sub), you will encounter rather slow, muddy, mushy, distorted, less dynamic, unrefined, sloppy, and just plain "Flatt sounding" bass response from your other wise "over taxed" bass woofers in your main speakers most often!(this would be "less worse" with monster main speakers with high efficiency and large large woofers built in however). In most peoples standard audiophile speaker rigs, again, taking the more demanding and challenging bass info OFF OF YOUR MAIN SPEAKERS has far too many benefits to your entire system!...not just sonically from your mains, but also dyanamically freeing up your main multi channel amp to more aptly reproduce what it does best, and that's reproduce less taxing upper bass on up!!!
Case in point, I can remember running many many 5.1 systems with the mains being run "full range" (sub via line level filling in the bottom), letting a receiver handle the amplification for the mains. with some of the more demanding bass soundtracs from some of thes movies out there, as well as "strong driving bass heavy music", like techno, the receivers amps will not only sound "flat" and "strained" throughout the system, but will get so hot and overworked that you can "shut down the system" or, at the very least have heavily compressed dynamics from the speakers! In this case, if you must run your mains "full range", you have to AT THE VERY LEAST run separates! Receivers simply can't handle this so well in general!..even the big flag ships! I know, I've experimented with the Big Denon's, Yamaha's, even Marantz's, etc(Actually, the B&K handled this the best).
So, back on track here...for PROPER DYNAMIC DISTRIBUTION, dynamics of sound, lack of strain and distortion, and maximum efficiency, you really need to get the bass off your main speakers(and center/rear sat's), and let the bass woofer(s) handle the bass and deep bass! That means running the sub "line level", which mean through the LFE mostly!(in the case of a 5.1 or better system, using a receiver or pre/pro).
Breifly bouncing back to my point about 2 channel set up driving main speakers and a powerd sub in paralell via "speaker level" connection, again when you play demanding dynamiic music through this set up, you really can't get the dyanmic potential in this "passive system" like you can when you're either doing a filtered sub/sat set up or, better, an "active" speaker system!(having all active speakers, with active sub possibly!). So there are trade offs, and each persons needs are different. For me, I sometimes like to listen to the "harder/heavier stuff"!
But for most peoples 5.1/7.1 sytem, the best way is still going to be utilizing PROPER BASS MANAGEMENT and a powered sub(s) connected via "line level" or LFE connection! The dynanmic range potential here is not going to be bested any other way. The only exceptions to this as being the best way, is when your using much more efficient main speakers(or center/rears even) like "powered towers"(i.e, Def Tech's, etc), truely active large full range speakers(like Avlar's, maybe even ATC's, and similar), or very high senstivity large pro audio/horn speakers that play over 100db/watt sensitivity with 15" woofers! OTher than that, most people using standard home audio passive floor standing and mini monitors are getting infinitely better dynamic capabilities and range by effectively "bi-amping" their system, using a crossed over sub/sat set up!!!..that's just the way it is. THX knows this, and all the top HT guy's know this! The audiophile purists might argue against these comments, but then they most all have rather "limited dynamic", weaker sounding sytems that won't hange with the better more apt dynamic systems set up for proper HT playback! I know, I've heard hundreds, maybe even over 1000 of the systems most audiophiles have running in 2 channel over the years! They watch movies connected via analog through their 2 channel high end rigs, and they like it that way just fine! And that's great I think. But those sysetms will never match the dynamic range of a truely proper HT set up!
Exertfluffer- I agree with your points above and I have very much enjoyed your posts. I just mentioned the speaker-level connection scenario in my post to illustrate a point that Polk makes that there are often several options available for working around "double filtering" and connecting an active sub to a system and the LFE-OUT is not ALWAYS the best choice in certain situations. Certain connection options (like speaker-level) that are seldom considered by many people can often work very well depending on your particular type of speakers, etc. I agree that it's not necessarily the BEST choice for HT in the assumed 5.1 system, but as we both have both stated above (either literally or inferred), it can pay BIG dividends if you take the time to experiment and learn exactly what you are dealing with within your own system.

I fully agree with your recommendations as they pertain specifically to 5.1 discreet HT. However, the Polk recommendations I paraphrased above were taken somewhat out of context and were a bit generalized. The Polk website covers many scenarios including using a sub just for 2-channel music, sub-sat systems vs. full range mains+sub, etc. but I did not want to repeat the whole article word-for-word in my post.

But I do think it's important for people to be aware of the problems that cascading filters can cause(that hard-to-nail-down "hump" or "hole" in the mid-bass, for example) and that often people aren't even aware that this MAY be the culprit (or a contibuting factor) in their HT setups.. And it was not being mentioned prior to my post.

Cheers! JZ
I would like to add a few responses to exertfluffer. Some of what I said you responded to out of context. No worries and Im not going to troll through what you've said to quote, your posts are huge! :)

I somewhat resent your comments about 2ch. audiophile setup being somehow outdated. Acoustics is acoustics. Building a HT around quality 2ch. setups has produced the finest results in three rooms ive been involved in (one being my own). In fact I believe its the only way for true high performance HT. That is, performance closest to the source (origonal mix). Sure this can be difficult but its not impossible. My point is: people with a quality 2ch setup are already ahead of the game and likely dont need to crossover their mains so damn high!

With a good room, a little work, and proper surround speaker selection you might be suprised at how much lower you can cross your surrounds to! Again, its ALL dependant on SO many factors. However, trying to utilize every last little bit of linear response out of each speaker is worth the effort in my experience. This effort will also teach one much about his own system and acoustics in general.

Dont forget why surround sound is so fun to begin with. Instead of directional imaging taking place more or less within the boundaries of 2 speakers, with surround this directionality can now wrap around us and even hover above our heads. It can be outstanding but every octave cutoff from each channel is sound that no longer contributes properly to this illusion.

I would remind you also that THX standards were NOT designed with HT in mind. These standards were "adapted" to HT as a foolproof way to setup a system. Nothing more, nothing less. Does it work? Sure it does. Is it the best way to setup a HT? Not to these ears.
Vedric...I have cited my reason for a "high" (80-90 Hz)crossover...(to keep the LF that requires large cone excursions out of the mains so that they can better reproduce the rest of the sound). You have recommended 25-35 Hz, suggesting that there is directional information down there. (OK, but that argument does not apply if multiple SW are used).

Question to you...Why do you think that a cone driver mounted in the main enclosure is superior to a similar (perhaps identical) cone driver mounted in a different box?
Six of one: half a dozen of the other.

In my case, where the mains are planar MG1.6, there might be an argument that spatial effects would be different if the higher range of LF eminates from the SW. I have addressed this issue by building three multi driver SW systems into the wall behind the three MG 1.6, so that the SWs "play through" the screens. Believe me, 80-90 Hz works best, even though the MG1.6 measures flat in my room to about 40 Hz.
Dont put words in my mouth Eldartford. I haven't recommended any specific crossover point. I mentioned where MY system is crossed at. I have in fact stated its VERY system and room specific several times. I have also stated that preserving as much linear low frequency extention from each channel is critical to hearing the soundtrack AS IT WAS MIXED. What part of "hearing a 70hz buzz from the right-rear actually COME from the right-rear channel" do you not understand?

All of this within reason obviously. If your speakers and amp cant handle 105 - 110db dynamic peaks at XXhz and you often listen at that level then DONT run them that low. If your're sitting in a mode you cant get rid of then by all means cut them off and redirect it all to LFE and work with the sub.

Also what argument "doesn't apply" when running multiple subs? You do understand the difference between discrete channels and multiple speakers hooked up to a single channel correct? It does not matter how many subs you use for the LFE channel its still a single channel with each sub playing the same signal. This is not stereo, nor is it surround, the channels are not discrete. This is a mono channel and it will ONLY image at the acoustical center located somewhere between the boxes depending on where you place them.

There is a TON of discrete and panned directional information mixed into soundtracks below 80hz. Throwing it to LFE for any reason other than system capability or room interaction issues is a complete waste of not only your speakers but also destroys the mix below 80hz.
I would like to respond a bit more here. But first I want to comment to Eldartford's situation with his 1.6 Maggies. Eldartford, you NEED TO BE CROSSING THOSE MAGGIES AT 80 or so, indeed!!! Especially given the delicate nature of those speakers (I know, I've sold them on a retail level for several years!!) The 1.6's need to focus on what they do best, and that's world class clarity, transparancy, midrange, and speed, etc! Bass, most all of it, in an HT context only really works adequately with those speakers deligated to the sub! Plain and simple. If you want to have squashed dynamics with these dynamics, strainted sounding bass, and just plain dammage to your speakers with these Maggies, then just play em full range for HT and see!(I'm talking in general to the masses here.
P.s., for the record, even though I'm not a "planar" speaker fan per se, I think you can't get better sound for the money for gorgeous sound than the 1.6!...very pretty speakers sonically. They do things most others can't anywhere near the price, conceeded. I like what they DO DO WELL!..which is offer a tremendous sonic value to the audiphile...you just can't sit off axis with em, or rock hard on em...that's all..no biggie. But I like 'em!
...Anyway regarding Vedric's stance that he likes his HT system(I think I read that right) to just be his 2 channel system, playing full range, I have tons of experience with that approach. And my comments are these...
...First, my last HT set up in my home has been a 2 cnannel music/HT system for the past several years! I've not gotten around to building a dedicated full blown HT system as of yet, since I'm in the process of a new home where it will reside.
I must say that I've heard WAY WAY WAY too many 2 channel high end systems in my years, and the reality is that there are few and far between stricktly passive 2 channel systems that can really handle a full range DD/DTS signals properly!!!(I say that, assuming one's using an outboard pre/pro to process DD/DTS material, rather than stricktly going through the analog outs of a DVD player, whatever, into the analog in's of a 2 channel preamp!...as using soley the processing in one's DVD player, WILL NOT YEILD YOUR PROPER DYNAMICS AND SOUND FROM YOUR DD/DTS SOURCES!...AND MANY AUDIPHILES DON'T REALIZE THIS!..YOU GOTTA GET A PRE/PRO IN THE CHAIN!). The problems, again,(and you're fooling yourselves if you think your dynamics are "ALL THAT!", AND OR ACCEPTALBE TO PROPERLY PLAY BACK WHAT THE MIXING ENGINEERS INTENDED YOU TO HEAR!) lye in the inability of your standard passive home audiophile speakers, full range or otherwise, to handle the bass information accurately, and without dynamic compression and lack of control!..this is a MAJOR PROBLEM AND SHORTCOMMING OF STANDARD PASSIVE SPEAKER DESIGNS TODAY!
Bass, wich is the hardests thing to control in an audio system, has MAJOR HURDLES TO OVERCOME being reproduced through PASSIVE CROSSOVER NEWORKS that most speakers posses! This is where the ACTIVE POWERED SUB HAS A HUGE ADVANTAGE, IN DAMPING FACTOR, CONTROL, AND DYNAMIC OUTPUT AND RANGE! Infact, I came back from the Hi-fi expo in San Fran this past year, and must have heard several hundred 2 channel only set up's for music. These systems, playing full range dynamic music simply can't hang!..that's the way it is. Infact, achieving true dyanmic transparancy isn't really so possible from passive speakers mostly, especially in the bass reigion! This is where active speakers have a HUGE ADVANTAGE!
Now, back to bass, just take a pair of Def Tech BP2000's, or NHT VT3's, or even ultra high end Avantgard horn speakers with ACTIVE POWERED BASS WOOFERS, and play em full range for movies versus ANY...I REPEAT, ANY standard passive home audio speaker for heavy dynamic, especially HT digital material, and you tell me which one's handle the bass properly!!!!....HANDS DOWN!..IT'S NO CONTEST! The standard home audio passive full range speakers out there can't handle the dynamics and the impact, that's capable from these current DD/DTS soundtracks, nor really demanding bass heavy music material!!!!
I beg to differ (it's all good..no worries..to each his own) with Vedric's stance that he believes that running your full range 2 channel music speaker set up for HT is just as good! I don't think so... And I've done maybe a 1000 home theater set up's in my last 15 years in this business. Infact, as I mentioned, I even pressently use a 2 channel set up for my HT!
Still, let me qualify that you CAN INDEED MAKE A 2 CHANNEL SET work well for HT! Infact, I'll take a quality 2 channel (added, you need a sub to do the bass though) system over a poor sounding 5.1 or better system any day! I prefer quality over quantity for certain. However, STill, as you've gathered, I've found out a few things the hard way over the years. And that's that you need to cross over your mains in a PASSIVE SPEAKER SYSTEM(wich most of us use), and let the active woofer handle the bass! Again, the bass dynamic range, output, and extenstion can't be handled properly by most all the passive speaker designs out there, for truely effective playback. yes, the bass will play down deep full range through a speaker, but it will be squashed, softer, less impactfull, less authoritative, and DEFINITELY less dynamically transparent! THX got this part very very right, and it works! Heck, they won industry awards from the Academy and such for their work....I think they know what they're doing when it comes to movie playback, as well as mixing! But hey, that's just my opinion/experience. To each his own.
And, like I mentioned, those of you(me included)who are doing your DD/DTS HT playback through your 2 channel preamp, without a dedicated outboard DD/DTS processor of some sort, your shorting yourself sonically! The dynamics and pressence, when you bypass the outboard processing just doesn't sound good!...sorry, that's the way it is.
I use an outboard DD/dts/pro-logic pre/pro looped into my 2 channel audio pre-amp's "BYPASS"(you can use Auxilary/dirrect, whateve) for best results in my two channel system. I then cross over the speakers as "small", or "80hz", (even though I can, and have tried different settings like 65hz, 50hz, 40hz, etc, etc), and kick in the powered sub for movies and heavy dyanamic music and such! There's really no comparison. Playing movies with the speakers full range doesn't cut it for movies...not even close.
But, I'm not saying I think everyone is don't it wrong using just their mains full range. But they will blow woofers, get shorted on the dynamic potential, impact, and accuracy of the sound in general for movie playback. But that's what it is. I've done it that way myself many many times, when I had no woofer. But it's not the best way. I'm sorry.
All you out there doing a 5.1 or 7.1 need a sub or two, or more...and you need to do bass managment to get the efficiency, dynamics, and control out of your system! You're effectively biamping your entire system, maximizing each portion of your sound spectrum from a "control" and "efficiency" stand point, and getting the sound you are supposed to by-enlarge! Only full active, high efficiency systems have it better in terms of total dynamic potential. And with movies out there like "The Hulk", "LOTR's", "Star Wars", action flicks in genral, whatever, proper bass distribution and control over the bass is a must if you want to hear more of what's capable from such demanding source material!
Again, as a comparison, go see any of these block buster, highly dynamic movies in the theaters, and then listen to em at home through your full range speakrs at home without proper bass MGMT! You'll be dissapointed I think. "The Hulk" just won't sound like it did in the movie theater...and it should!
Vedric...I normally don't use the LFE channel to drive my subs. If and when I get into movies I can switch the center SW to use the LFE signal.
I have watched a couple of movies since I made the changes mentioned above. It seiously improved the impact and extension of the lows in both DTS/DD. I may try bypassing the outboard controller(NHT SubTwoi) altogether, running the LFE directly from the Processor to the Sub. I'll lose Phase control and the LFE gain, but....I have phase at 0 degrees and I can easily compensate the gain with the Processor itself. I will repost after experimenting. Thanks again guys.
"Distortion"...without going back through all your threads, I just wanted to mention, not for just you but all reading, that when considering crossover frequencies/placement, for best sound, and correct sound even, you must make sure that all the speakers that are crossed over are coupling WELL AT THE CROSSOVER FREQUENCY! For example, if you are crossing all your speakers over at 80hz, or some of them even, those speakers MUST BE PLAYING CLOSE TO FLAT DOWN TO 80 HZ WHERE THEY'RE SET UP AND/OR WHERE YOUR LISTENING POSSITIONS ARE CORESPONDINGLY!!!
People most often get poor results with sub/sat systems, and even systems where they're using more full range speazkers but crossing them over to a sub, by not making sure their getting adequate frequency extension and balanced response at that frequency especially!!! The often result is that "hole in the middle/bass" sound that sounds incomplete!!! This is what most audiphile's who use full range speakers complain about with sub/sat systems, or otherwise against "not" running anything other than 2 channels full range for music/movies/whatever!!!...and to that, I can understand. Another issue becomes incorrect phase between speakers and sub vs. seating possition!!! another cause of problems in crossed over or sub/sat systems. And to which, I concure, you need to consider some other steps/issues when placing a sub/sat system up properly. But then you need to set up any speaker system up for flat/even frequency response anyway!...it's just a bit different proceedure when considering separate elements, such as a sub/sat combo, or even full range/crossed over to a sub set-up.
So, I just wanted to mention, that anyone crossing over speaekrs/satalites/whatever to a powered sub/bass module, that you need to consider making sure, first that have your speakers placed in possition that allows them to extend evely all the way to the crossover setting(i.e, 80hz, whatver). In general, I find a lot of sealed box satalite speakers need to be closer to the room boundaries often (not always, as room modes are scattered, but maximize near walls) to couple strongly down to 80hz(depending on design of course...some go deeper) to sound the best at 80hz. Also, placing smaller monitors on stands no higher than 24" is often a good way to ensure good bass resonse at 80hz, considering a standard 8' ceiling. IF you have a higher 9' or better ceiling, the stand height can go up!..this has been my "general" finding with most set up's. People often have trouble getting flat frequency response from their satalites who's bass woofer(s) and port are too high off the ground(unless up higher toward ceiling placemnt)! The problem there is that at 8' ceiling heights, the 74hz mode is in the middle of the ceiling to floor distance. And the close the speakers bass woofer/port is to the middle, the weaker the bass response in that reigion, which is close to teh 80hz cross point!..in general, I just find the bass response is stronger and better coupled to the speaker/room when the bass woofer is down lower on a stand. Of course, floor standing speakrs have the other problem, especialy in smaller rooms, and that's that the bass woofer/port are closer to the floor, which reinforces the bass who's 1/4 wavelength is not greater than the distance between woofer/port and floor! So floor stander often have no problem with crossing over to a sub, because they already couple well in the bass in most all settings! Of course, there are other room dimmension and size considerations. but still, the important thing is making sure your speakers sound full and extended down(flat is also the best) to the CRITICAL CROSSOVER FREQUENCY(In most cases, 80hz w/small setting).
If people would take time to properly set up EACH SPEAKER for flat, extended, and even a fruency resonse as possible (much easier the larger the room, but more critcal in smaller troublesome rooms!), especially down at the critical crossover point, they would get TREMENDOUSLY DYNAMIC, EXTENDED, FULL, COMPLETE, FAST(MUST HAVE PROPER PHASE BOY'S N GIRLS!), HARD HITTING, AND COHERENT/ACCURATE BASS overall!...and you'd be thrilled!
Again, as I posted earlier, dynamic transparancy and weight/speed is also largely a factor of efficiency. IN this case, you get more efficiency from passive speaker systems(i.e, B&W speakers, popular Paradigm studio's, and similar, etc) when you cross over those relatively inefficient speakers(considering the passive hard to control damping-wise passive networks in those speakrs, as opposed to ACTIVE PRO MONITORS AND SUCH) to an active sub, effectively bi-amping your system for maximum dynamic potential!(even more so considering most use less able receivers to drive their speakrs...separates are usually much stronger)
But still, after maximizing that part of the set up, getting proper frequency response, phase, proper crossover blending, and attaining overall coherence from ALL YOUR SPEAKERS, including and especially in relation to your sub from all speakrss, your system will rock!!! It'll be so dynamic, coherent, weighty(make sure you have enough sub and also amp for your room/volume needs!), and powerful..not to mention seamlessly transparent!
Most people never end up with a proplery set up/calibrated system/room, and they never end up even gettiing one speaker set up correctly, let alone 6 or more!!!!
Take one speaker at a time...first the mains, then the sub to the mains, then the center to the mains/sub, then the rears to the sub!..all for perfect frequency response, coupling, and phase alignment. YOu'll then have a system so complete, hard hitting, coherent, and dynamic you won't no what do do with yourself!
Of coure, there's lots more to acoustics and set up, regarding imaging, soundstange, inteligibility, and tonality and such, among others. But you'll be WAY AHEAD OF THE GAME, if you can just get the speakers set up right, and the crossover mazimized, and the phase right!
enough said.
Ok..not "enough said"!..my bad.
Actually, I forgot...for those consdidering larger tower speakers stuffed into smaller, even medium sized rooms, and are playing them full range, you are going to have to deal with the problems with bass boost and boom! IN general, the bass will be heavy, thick, and too dominant and boomy! In short, you'll have more bass mode problems and un-accurate bass playing those big speakers full range!..which is another benefit of crossing em over as "small"(or just using smaller speakers in smaller room environements), and concentrating on balancing a more flexibly place subwoofer(or more), and possibly "EQ'ing" out the bass just to the sub maybe!!!
Especially in the average "smallish" rooms that most people have to deal with, proper bass managment and balancing becomes even more critical for "flattest"(wich means best dynamic range between softest to hardest dynamic extremes by the way) bass response in a system. Larger rooms have more evenly distirbuted bass modes, and finding more flexible plaments for speakers becomes easier in such spaces. So you have more flexibility and likely hood of a novice getting "flatter" "more natural", and accurate "frequency response" from the system.
I just find that doing the "small" crossover setting already gives too many advantages towards getting a more accurate, dynamic, and easy to work with sound from most peoples scenarios they're likely dealing with.
Good luck
"Number one","set all speakers to large"."Eye,eye captain"."All speakers are set to large"."Number one,how do the nulls and peaks look"? "Captain, it's a miracle,no peaks or nulls"."Number one,set a course to use the sub only for LFE"."But Captain, no one uses full range and the sub set to LFE only"......to be continued
Exertfluffer, thanks so much for the info. Today I tried running the LFE straight from the processor to the Sub. Which, in effect, bypassed the external controls/crossover. It didnt make any difference. But, when I choose, and I usually dont, to run my Sub when I listen to 2 channel bypass, I will need the Xover since my Processor only outputs a full range Subout (in that mode).
Sheesh. You guys thought i was long-winded ???

Personally, i disagree with a LOT of what Exertfluffer has stated concerning full range mains, surrounds and powered subs. "Most" commercially built powered subs perform less than optimally for multiple reasons and should be avoided. They are nothing more than a compromise and a convenience for those that aren't willing to do things "right" and / or want to keep things simple / are on a budget. There are exceptions to this rule, but for what these "exceptional" powered subwoofers cost, you could easily buy a passive sub, active crossover and a better quality amp. Most manufacturers charge a LOT for that "convenience factor", especially when maintaining high levels of quality through-out the entire design.

As to some of the other conversations here, my theory is that one should buy speakers that are suited for the task at hand. That is, IF one wants to do things "most correct" or "optimally". While i realize that most folks don't have the space for this and have to compromise / blend their 2 channel & HT systems together, I didn't do that and don't recommend it if at all possible.

I think that Vedric and i are on the same page. That is, my mains are down about 3 dB's in the low 20 Hz range. My surrounds make it down to the high 20 Hz range due to slightly smaller woofers and a slightly smaller cabinet. I mention this because El brings up a very valid point, but one that doesn't apply to my system. That is, since much of what we are hearing is voice reproduction in movies, the most important part of sound reproduction for an HT system would be the midrange. If the woofer is doing double duty as the lower and / or upper midrange, having it try to reproduce deep bass will surely "muddle things up". That is why i bought and run four-way speakers i.e. woofers, lower midrange, upper midrange, tweeter for the mains and surrounds.

In a design such as what i'm using, all the bass that requires any type of excursion is handled by dual woofers. Using this approach, the other drivers can do their thing over a narrower bandwidth. Not only does this reduce the required excursion from each of the other drivers, it lowers distortion, increases power handling, improves transient response and raises the max spl of the system. It is a "win-win" situation and there is no loss of resolution due to having the mains cover the full bandwidth.

Then again, every situation is different and you have to build / design for that installation and / or work with what you already have. Given that most people think of HT as being BIG "booms" and high spl tire screeching, the market has been flooded with highly efficient, low cost products that measure and perform poorly but sound "exciting". If that is what one is looking for, a cheap but effective system can be easily built for not that much money. Personally, i wouldn't take that approach, but there are tons of people out there that are doing just that. Sean
LOL, but as I was reading that post I was thinking it was you (i didn't look at the header). I've always believed you should set the cross a full octave above the -3dB point of your speakers, to avoid just such a 'hole' in the LF response. Of course, this is still just a crude rule of thumb, and more precise (actual) measurement of the in-room response and tweaking would be better. And also, of course, this esults in the sub operating up in a fairly elevated (and localizable) frequency range. Which makes another argument for mains and sats that can go flat to 40Hz or better (as you've done).
I run full range mains (F3 30Hz, F6 20Hz, Q=.5) with an 80 Hz second order high-pass for excursion control, but plan on switching to 40 Hz 4th order.

Sealed box excursion increases 4X with each octave lower, dipoles 8X - so although my (half-space, semi-anechoic) excursion limited main speaker output is 118dB @ 80Hz and 100dB @ 40Hz it's just 82dB @ 20Hz.

Reference level home theater playback calls for 105dB regardless of frequency.
Drew when you make the switch from 80hz 2nd order to 40hz 4th order you will absolutely notice a difference in directionality of your mains. Any panned image utilizing each channel from 80hz and lower will create a more palpable image. A horse riding in soft soil from R to L for example.

Depending on your previous subwoofer setup you may or may not be able to recognize this right away. If for example you had a pair of subwoofers in each front corner both working off the single LFE channel you would be used to a more frontal diffuse sound in this region. The actual change will be more difficult to locate.

If you were using a single subwoofer operating in a corner the difference will be obvious if your mains are up to the task. You are moving in the right direction providing your room doesnt freak out on you!

Eq'ing a sub properly between mains and surrounds remains a challenge in all but the most perfect rooms/systems but it seems most manufacturers are "getting it". Velodyne's digital drive subs as yet another eq'able example.

If its mixed from the right rear any attempt to reconstruct the signal from the right rear is one more step toward sonic perfection. This cannot disputed.

PS: Im glad that Sean guy somewhat agreed with some of what I've said! I would hate to have one as long winded as him as an enemy! Just kidding Sean! :)
In responding to "sean's" comments, i must say that I even used to believe what he recommends about "crossing over speakers, subwoofer's bass quality in general, and general approach to setting up a system properly...but my extensive(much more than his likely..as an edjucated guess) experience, and over 1000 systems, and 1000's of man hours under my belt, I EASILY DISAGREE!!!!!!
tHE REALITY IS, is that playing passive home audiophile speakers full range WILL GIVE YOU A WEAKER DYNAMIC PRESSENTATION, more bass mode challenges to overcome(especially in smaller/medium rooms!), distorted bass woofers(which are underdamped and controlled), lack of extension, weight, authority, impact, and effectiveness, as compared to what the mixing engineers of these block buster movies intened you to hear!!!!!..infact "sean's" recommendation wouldn't hold water for playing back through a speaker system in a large venue either!
People Like Lucas Film, THX, and other mixing authorities have set up the 80hz THX certified paramaters for a reason!.they work! I'm sure some people here(including all the "wanna-be" HT expert/2 ch audiophile "sales-people" I've worked with over the years in 6 stores) would like to think they've got it right, and the REAL AUTHORITIES/EXPERTS HAVE IT WRONG!!!!....YEAR RIGHT!
I'm not saying people can't run their speakers, or shouldn't do thier passive home audio speakers full range for HT!...you of course can. But don't fool yourself into thinking it's better for movies and heavy dyanmic dubties...IT AIN'T!!!
You'll indeed be blowing woofers, getting weaker dynamics, distorted high dynamic bass info, weaker pressence, lack of weight, extension, authority, and a generally lack luster HT playback system!!!!...that's the deal. Not to mention that most people are using very limited, and "iffy" power output from their receivers to driver many speakers full range!!!!!...they're starving their speakers for control!!!...and running into clipping problems!!!
I've seen/heard/done it all before, time and time and time again!
The list of high end and mid-fi speaker gear I've EXTENSIVELY PLAYED AROUND WITH (from my own custom/hobby experience, including 6 audio store I've worked at, and 1000's of hours of custom experience and 100's of clients)
Have included tryinig to run full range speakers of the like's of Willson WATT Puppie's, Large Dunlavy SCV's on down, All the Thiels, Martin Logan Prodigies,Monoliths, etc..., B&W's high end stuff(to 801's), NHT's gear,Mirage's, Snell's, Celestions, Audio Physics, you name it , and more!...and lots of other passive high end gear! I've also played extensively around with most mid-fi gear, including NHT, Paradigm, Def Tech's, Klipsch's, Polk's,M&K PSB's, etc!..and everything you can imagine!!!!
I've tried so many times at making these speaker offerings, using both receivers and separates, play ful range for HT!..it's not as good. YOu GOTTA GET THE SUB TO DO THE BASS!
eXCEPTIONS are, like I said, large full range speakers that have powered subs, like Def TEch's VT3's, Infinity Prelude MTS's(wich I've owned), Avantgarde horn speakers with powered subs', and similar!...also large passive horn pro audio and cinema speakers!
Now, adressing "sean's" recommendation that people simply buy an active crossover, and some passive woofers, and put it together,...well that' just not practical for 99.9% of everyone out there!!...So who's going to do that?..very few!
AS for clains that subwoofers offer generally slow, boomy, slopy, unacurate, "low-fi" bass, well that's also not so accurate!! The reality is that powered sub's do get a bad wrap becasue of larely USER ERROR!!!!!! MOST people don't ever get their sub(or speakers for that matter) set up correctly!...thus affecting the fidelity and quality of the bass they hear! They almost always have the bass turned up too high in level, placed in a bass mode in the room, in a corner, and out of "absolute phase" with their other speakers!!!...it makes getting anything more than cruddy bass mostly impossible! STILL, THE RESULTS THEY GET ARE STILL BETTER AND MORE EFFECTIVE FORE MOVIES USING THE SUB CROSSED OVER TO THE MAINS AT 80HZ!!!!
Again, movies are mixed with explosions, and gunshots, natural dissasters, monster footsteps, and other synthesized sound effects, and other very dynamic overall info! passive home audio speakers can't deal in the bass with this properly! I nkow, I've tried it all before, again and again!..year after year! That's what it is.
Also, yes, many subwoofer manufacturers out there are designing sub's with a built in low "Q factor". This makes for a more "loose", but extended, dynamic, and better power capable design for what movies are dishing out indeed. Still, using this option is still better, IMO, and THX's I think, than the alternative!...it does for movies what they need to!
Now there are companies out there which makes sub's that are more "audiophile" in their sonic qualities, and that pretty much negates all arguments once proper care is taken in setting them up for music/or HT. You can easily pic up subs that have good Q factor, as well as output capability!
M&K's larger MX series, Paradigms excellent, PS1000 to their world class Servo 15, NHT Sub 1, Veldyn'es higher end, Infinity's MTS subs's, Earthquake's dynamite MK1V 12 and 15" digital sub's, and many many others out there, provide not only tight control, but dynamite extension and output!!! Set these up correctly, for proper bass resonse and coupling with the room/speakers, proper phase and coherence with the other speakers, and you can have an extremely high end HT set up that's pretty hard to fault/surpass without getting too custom!!!!
But, to each his own. Still, give me the meat and potatoes over "pipe-dream" audiophile ambitions for proper HT set up, every time!!!!
I'll still put 99/100 people on my side in a set up comparison for a proper HT effort! I know what works...I've lived it, breathed it, and tried it all a bagillion times!!!!!!
I agree with the advantages of running, even "full-range" speakers, as small, easier placement, better dynamics, better bass, etc...

But I find 80hz too high, there is too much info around 80hz that even good subwoofers cant play as well as speakers, and, regardless of what THX and Dolby say, 80hz is still directional, (I have two subs wich minimize that problem), so I use 60hz for all speakers...