Best setup for two subwoofers.

I would like to run 2 subwoofers in my home theater setup. Currently i have one Klipsch RT-12d, which sounds great, but I would like the depth of bass to be "over the top". Will it sound good to mix and match types and brands of subs? I was looking into a Velodyne 18dd or sig 1812, but am unsure how well it will work. Should i just add another Klipsch or can I use something different altogether? Im kinda new to all of this and just wondered if anyone else can share any ideas.
In my opinion it is okay to use different subs. I'm also an advocate of asymmetrical placement, so that the two subs are interacting with the room modes differently. The result is each sub will give you a different peak-and-dip pattern at any given listening position, and the sum of these two dissimilar peak-and-dip patterns will be smoother than either one alone.

Since you want very deep bass, you might put the sub that goes the deepest in a corner, and then put the other sub along one of the opposite walls perhaps 1/3 of the wall dimension away from a corner. This would give you good asymmetry in the horizontal plane.

If you want a very informed opinions, go to Scott Wilkenson's Home Theatre Geeks podcast. Home Theatre Magazine reviewer. A few weeks ago he had an episode with Dr. Floyd Toole and this guy KNOWS SPEAKERS AND SPEAKER DESIGNS! and much of the podcast was on sub woofer and sub woofer placement and design along with general speaker design.

That said TWO subs will provide for you the best compromise in bass for the most listeners in a room if each sub is equal distant down front and/or back walls or side walls. IE: Put each sub down the front wall the same distance away from each side walls. Or you can put one sub midway down the front wall or near to it and the other sub reversed down the back wall. Or try putting each sub mid way down each side wall of your room. Doing any of these will balance out bass and suppress room anomalies for more than one listener.

Again check out Home Theatre Geeks podcast and listen to the Floyd Toole episode.
Les creative edge, to the best of my knowledge none of the subwoofer studies published by Harmon researcher Todd Welti (presumably Toole's source) investigated asymmetrical placement, simply because that introduces too many variables. Another researcher, Earl Geddes, demonstrated improved smoothness from asymmetrical placement in a paper that is unfortunately no longer up on his website, possibly because it gave away too much to potential competitors. Todd's consumer-oriented paper is no longer up on the Harmon site either.

Based on conversations I've had with both Earl and Todd, the main thing is to have multiple bass sources spread fairly far apart, as that is where the greatest benefit accrues. The exact positioning of the subs is generally less critical than with a single sub.

It is interesting that Earl and Todd arrived at using distributed multiple subs as a solution to room modal behavior completely independent of one another. Neither was aware of the other's work until Todd published the first of his papers.

From what I understand the only concern one truly has to worry about with two or more subs is that they are not placed in a way where one is out of phase with the other. By setting up multiple subs in ways where they generally mirror each other or sit along side/front walls equal distance from corners will generally have each sub work in tandem reinforcing the bass signal and keeping boom and nulls to less effect. Now of course if you have subs with a variable phase control you can with effort tweak the subs to work more in phase and thus positioning errors will not be quite as much an issue in terms of phasing.

Now of course two subs if not sitting in a best compromise situation for what may be determined as the best sitting locations for listeners can still aggravate boom and tubbiness of bass along with nulls in bass.

Dr. Toole suggests the best choice if budget allows (and factoring extra electricity useage) is FOUR subs each in a corner. They will cancel out well over 85% of the room effect of boom, tubbiness and nulls. They will provide the smoothest bass for the most listeners in room. On top of that they will work more efficiently as the corners reinforce their output causing the sub amps to work less hard. He suggests you may be able to settle for even smaller subs say 4-10's rather, than 4-12's or 4-15's. In such a case where you use FOUR subs one in each corner it no longer matters what your room is shaped like. It could be square, long rectangle, short rectangle, L shaped, or whatever.

If you want the easiest placement for multiple listeners with only TWO subs again setting each up down a wall and out of a corner and where each is relative to each other similar in the room placement you will get a better compromise for more listeners in room.

If you only have ONE sub the best thing to do is to put it as close to a mid placement on a wall, front, side or back to give the best compromise for multiple listeners in room. If only one listener will likely ever listen then put the single sub in a corner but understand once another listener or more then sits he/she/they will get a compromise in sound that may not be too pleasant for them.
If this is indeed Dr. Toole's position, then I disagree with him:

"...the best choice if budget allows... is FOUR subs each in a corner.... They will provide the smoothest bass for the most listeners in room."

I question whether that's really what he said, because Todd Welti's investigation showed that four subs with one at the midpoint of each wall in a rectangular room was smoother than one in each corner.

In the paper mentioned in my second post above, Dr. Geddes compared four subs each in a corner against three subs in a specific asymmetrical configuration (one in a corner, one along an opposite wall, and one closer to the ceiling than to the floor). The three subs asymmetrical were not only smoother, they also had less frequency response variation from one listening location to another.

I have been manufacturing four-piece multisub systems since 2006, and my experience plus my customers' supports the argument for asymmetrical positioning even if it's confined to the horizontal plane. I am unaware how many of my customers tried a symmetrical configuration, but to the best of my knowledge all of them have chosen to use an asymmetrical one.

Regarding the relative phase of widely-spaced subs, it is far less critical than intuition would lead us to believe. The reason is, we cannot even detect the pitch of a bass note before several cycles have reached our ears. By then the room's effects have totally swamped the first-arrival sound. For all practical purposes, in the size rooms we listen in at home there is no such thing as "direct sound" in the bass region. By the time we hear it, it's all reverberant sound. This is precisely why a distributed multisub system offers such a significant improvement in perceived bass clarity and smoothness, instead of sounding like mud: The only place a multisub system offers improvement is in the reverberant field, but from a perceptual standpoint that's all there is in our rooms anyway.


The best thing I can suggest to you is to log on to Scott's Home Theatre Geeks. Look up the Episode with Dr. Toole and enjoy listening to one of the most respected men audio reproduction of sound, how humans perceive sound and speaker R&D.

You will find his assertion that 4 subs placed in each corner of the room will give the most efficient and likely best sound of sub bass for multiple listeners in room. Four subs placed mid way on the 4 walls may give better general fidelity but are not as efficient in bass output to power input.

Dr. Toole is also fine with two subs placed generally midway on walls if costs are an issue.

Thank you very much for the link, Les creative edge.

In the first half of the interview, I didn't hear anything on the subject of speakers, rooms, subwoofers, subwoofer placement, or psychoacoustics that I didn't already know. Not trying to be a smartass, but those are topics I have studied. Now I did learn some of the "why" behind limitations at the microphone end of the chain, and behind the fallacy of pursuing "ideal" room dimensions.

Much of the surround-sound discussion in the second half was EXTREMELY educational to me, as historically I've been a two-channel guy. Toole obviously can teach me a great deal about multichannel, so a few minutes ago I ordered his book. I have you to thank, Les creative edge, for making me aware that Toole's book contains a lot of valuable information I am not familiar with.

Back to the first half of the interview. Fascinating that Todd Welti, whose work I'm familiar with, was actually commissioned by Toole to investigate multisubs. I hadn't appreciated that it was Toole's idea first.

As far as subwoofer configuration goals, Toole apparently places top priority on bass efficiency rather than smoothness, as he prefers four in the corners over four at the wall midpoints. My top priority is smoothness, which comes at the expense of efficiency because destructive interference is the mechanism by which maximum smoothness is achieved.

The comparison I would like to see, but which I don't think anyone has made, is four subs at the midwall locations vs four subs in a thought-out asymmetrical configuration. I bet they both would sound pretty darn good.

Again thank you very much for this discussion and the link, without which I would have continued in my mistaken belief that there probably wasn't much in the book that would be new to me. At some point I wish to become competitive in the home theater sound system marketplace, and Toole's book will be a primary resource.


Thanks and I'm glad posts like we've put here can be informative for each of us and others here. This is to be a fun hobby for us audio/video geeks as Scott Wilkenson would likely say. Too often, too many of us fret needlessly over things that can just take the fun out of the hobby.

I remember first hearing and reading about Dr. Toole back when I was a young kid in the early 80's. We had a KICK A$$ audio magazine here in Canada back then called Sound Canada and it was quite simply one of the finest audio magazines at the time and guys like Ian Masters, Dr. Toole and others wrote cool stuff in it often. Even though much of Dr. Toole's stuff was over my head then, today as a hobbiest and one who tries to keep an open mind I've learned things from him and other respected persons in the field.

If I may, I was very much anti-multi channel for music until recently. I got my Oppo BDP-83 with the AIR Record sampler Blu-ray and that was an aural revelation for me in how good properly engineered multi-channel sound can be. Mark Waldrep was also on Scott's podcast a while back, check it out to get his ideology on AIX Records and their efforts at making superior quality, hi rez multi-channel sound.

For me when listening by myself with a stereo LP, CD or tape, well I think that sounds the best if you can sit in the stereo sweet spot and you play back a good stereo recording. But a proper, hi rez multi-channel recording on good consumer gear that is properly setup and calibrated KICKS REGULAR STEREO'S A$$! 1-2-3 years ago I'd never admit to that. But having heard hi rez multi-channel sound on an AIX Blu-ray sampler disc with my modest but well setup system BLEW ME AWAY!

Well I sided tracked things bad enough, back to your regularly scheduled programming, LOL!
Thankyou all for the help. You really helped me understand the question I had and took me to a level beyond what I knew existed. I will try my best to experiment with the methods mentioned. Ill post results as to what other sub I pickup and how well everything is working together, as well as my placements. Thx again.
Gozren, I tip my hat to you for wading through all that and finding something useful. We kinda went off on a tangent or three there.

Very best of luck with your project... and if you get a chance to listen to the interview with Dr. Toole (episode 14 at the link Les creative edge posted), it's great stuff.

Bottom line here is you have so many variables in play here, it's gunna be nearly impossible for anyone to discern practical application here. I mean,it's all relative here, and any setup needs to balance out, with all issues addressed, and all variables qualified and considered, relative to "truth".
How big is this space? Can 2 subs even work in his room? I haven't seen it. How's the construction? What's the layout? How many seating positions in play? What's the lifestyle of the listener(s)?
Not considering all of the above -even knowing none of the variables - my simple answer is that you're likely going to run into fewer issues (phase, frequency response, comb-filtering, localization,etc ), and get the best integration and bass/sound quality running multiple subs (ok, in this case, two) if you try and keep a set of subs up near the front/center of the room or setup, near the center channel speaker. I would set them side by side in the middle of the front of the room (or stack 'em just off room center axis), along front wall, for a likley rock solid integration with a multi-channel system, and you'll have great off-axis phase integration with the main speakers, (if adjusted properly relative to mains/center), good integration, blending, etc, and you'll properly deal with modes 1 & 2 in the bass response (smoothing out the bottom). Anything else, and today's superb digital EQ's/DSP integrated into many AV recievers and pre-pro's is taking care of smoothing out things even further, fixing phase, level matching, response, yada, yada.
While you can put subs all around the room, in various places - with benefits one way or another - you'll be dealing with phase issues from seat to seating position and sub to speakers, challenging speaker to subwoofer integration from all seatting positions, distracting localization of upper freq's, obtrusive subwoofer speakers cluttering your space, etc.
Bottom line, keep it simple. And, of course, I know nothing of your room and associated equip.
Stick with what I'm advocating, and it'll likely fit very well, regardless of what your seutp is, and all the variables of which I know nothing of.
When all is said and done, your goals here should encompase these important points - if performance is at the forefront of your target: even base response from the woofers- with no major holes (peaks avoided and knocked down, if EQ'd), proper phase and near seemless integration between speakers and subwoofers from all your seating positions (there's always going to be some level of compromise, all things considered - but, obviously, you're striving for the least amount of compromises), proper level matching between woofers and speakers, and try and avoid frequency filtering by placing subs distances where you'll be canceling a frequency that's in a critically covered spot by the subs (1/4 wavelength of the distance betweeen them)
After that, you're only concern is the lifestyle choices with having gear all over your floor! Subs can look awefully unsightly stacked all over the house. Er at least so my girl says...
I can give you a more practical response. I did what you were asking. I used to run a RT 10d with a Rel sub. To me it was not sound I was looking for. I went with a pair of JL 112's which sound great. A pair of good subs really did it for me. My advise is to get a better sub see how you like it. Then get another matching sub if you are not completely satisfied. Setup is important but a good quality sub is going to make a huge difference. There are a lot of great subs out there. Once you hear them you will see where the klipsch comes up short.
"Setup is important but a good quality sub is going to make a huge difference" (Docrobbi)

My experience professionally, and decades at this, is just the opposite, actually. Just to consider. I would put this comment as "A good quality sub is important, but SETUP is going to make a huge difference!"
I've simply heard way way too systems over the years, that used some otherwise pretty exotic high end subs/gear in them, that sounded not only aweful, but performed disasterously, because they weren't set up properlyAnd I've sold some of the most expensive subs in the world over the years! - so I feel qualified to say this.
So, yes, I put proper setup, room acoustics, equipment matching, engineering, and calibration - even BALANCE - over quality of gear in this case. And with subs, it probabaly even more true here. Setup and integration is everything when it comes to subs/bass
If you have one sub to fill in deep bass for front speakers and one for LFE it can be okey to run different brands. But if you want to run both subs for LFE they should be of same brand and ideally also exact same model.
My system is 2 channel with OB main speakers and two subwoofers. The room has one stud/plasterboard wall, quite a long way behind the listening position, all other walls are plastered brick and the floor is solid concrete, not suspended. I had managed reasonable bass integration with the main speakers and the main sub but there were always issues around the crossover point and interaction with certain room modes

After trying numerous types of passive acoustic treatment, none of which were ideal, I decided to jump into digital correction, adding a DEQX processor in 2012. This required a large learning curve but the system is now optimized to a level which is way beyond my original expectations

I am by no means an expert on digital room correction but I do have quite a lot of hands on experience in this area. There is much more to setting up one or more subs - more than just room placement or phase, as I have learned (please forgive the length of this post and I welcome comment from those more technically knowledgeable than me)…

The main sub is a M&K MX-200 which has served me well for a long time. When first purchased, positioning involved placing the subwoofer at the seating position and moving myself around the room listening for the best sounding spot for the sub (and then moving it there and me to the chair !). It has been in that position ever since. I am lucky that I have a dedicated music room with just one chair so placement was not an issue. As it happens, the MX-200 is slightly behind the LH main speaker, facing the LH wall, angled slightly forward but not particularly close to either the side or rear walls, or the corner

Things got a lot more challenging when I added a second sub (B&W PV1D because I liked the fast transients) and that's when I decided to go digital because with 2 subs the room was sometimes getting unmanageable. The B&W is slightly behind the listening position, similarly angled to the M&K & closer to a wall but has drivers diametrically opposed rather than front-down (M&K). Subs with different properties definitely complement one another when you can individually correct and align them

Using subwoofers in a room, the situation becomes very complex because of the interaction between several interrelated factors…..

1) Room / position
2) Crossover point / slope to main speakers
3) Phase
4) Time alignment

All these areas affect each other and in particular good time alignment becomes really critical . Most ‘solutions’ address phase first and then ‘basic’ time alignment but few I could find also allowed steep crossover slopes between sub-mains and a method to blend these seamlessly. DEQX does that.

The biggest revelation has been discovering that all frequencies have differing wavelengths and there is no ‘perfect’ time alignment, just a compromise spot where it actually ‘sounds’ perfect in that particular room

Let me explain….

I can give an example of this last comment from experience – my speakers are anecholically optimised for an almost flat measured in room response 16hz upwards. Rather meaningless I know because it is important how a system sounds playing music and not how frequency response looks on a computer screen. It’s a good start however

So, the speakers are digitally calibrated ‘flat’, the subs are in the optimum position based on room listening, the DEQX has ensured a phase aligned crossover to the subs and I have set the time alignment between both subs and then to the main speakers by using a mic at the listening position. So far so good but it wasn’t ‘quite’ perfect…still a few occasional bass issues. However, I have found that getting the optimum time alignment is actually much more complex because of the wavelength issue

The universally accepted method is based on impulse response, either aligning with the first peaks on all speakers or on the initial impulse rise (slowing those closer to the listener back to the timing of the furthest, in my case the M&K sub). I have found that this in itself is fraught with potential errors

Time alignment with what?

The impulse response plot of a main speaker and a sub is the sum of all frequencies from that speaker and as they all travel at different wavelengths, what are the peaks and rises actually showing? They give a good start point but further tweaking is needed to finally hit the sweet spot where that particular system in that particular room sounds as near as dammit perfect. It’s like focusing a camera lens and when you get there it’s very clear - I now have no frequency issues whatever I throw at it. Bass is fast, dynamic and clean and the room has completely disappeared. Believe me, I play a lot of music and this comment is based on experience for hours per day over many months. Although DEQX is expensive and fiendishly difficult to perfect, the end result has to be heard to believe

Now, this is interesting…

Just by changing time alignment on this ‘perfect’ setup, suddenly peaks and dips in bass response reappear, I guess because now some of the crossover frequencies or those interacting with the room have become out of sync .

Here are a couple of ‘real’ examples…

Changing timing i.e on the main speakers by an additional 2.7ms to the subs creates a noticeable boomy peak around 85hz. No change to equalisation to cause this either. It is because the timing at that frequency is now out of step with the rest of the range and it just doesn’t sound right. Equalisation doesn’t cure that because all it does is increase or reduce the volume around 85hz to make the hump more or less noticeable and the music no longer sounds as real

If I move alignment to, say 5.3ms then the audible change appears elsewhere in the low frequency response. In this case bass appears to decrease, probably because the room or crossover interaction is now cancelling a particular frequency which is out of step time wise. Return to the correct time alignment and it jumps back into real performers sounding just as if they are in front of you with ‘space’ around each one. Amazing really that such minute differences can be so noticeable. Therefore, with subwoofers, I believe room equalisation or passive treatment alone are insufficient, as is just setting impulse response in simplistic terms

The end result can be stunningly realistic. This is a way to stop a poor room ruining the enjoyment & I like to listen to music, not ‘hi-fi’ or noticing abberations in the sound. It still surprises me how much difference I obtained the very first time I (properly time aligned) corrected my room from its original incarnation, using the same sources, amps, cabling and speakers. ‘Night and Day’ is an overused term but in this case pretty accurate

Anyone reading this is quite entitled to be sceptical and I do not claim to understand everything about the subject but subwoofer integration once it’s implemented correctly is stunning. It just takes a lot of effort and a reasonable financial outlay to get there

All of this may not be particularly scientific and I am not saying that DEQX is the only solution, however it works for me and I now feel I am getting the best out of it

My wife regards me as obsessive with my music, almost to the point of OCD over the past 30 years & I used to be one of those people who always felt my system should sound better. That is no longer the case
Interesting post. I assume since you've got one DEQX you're not running your subs in stereo? Is this something you've considered doing? Just curious.
Drewan+1 There's no free lunch. I'm a two channel two Velodyne DD-12+ user. The Velodyne Manual Room Optimization program contains many parameters of adjustment. While the instructions are clear the actual trial and error listening can be a lengthy process.

In my case the end result is the most seamless crossover between the main speakers and the subs I've ever experienced which includes the previous DD program. From there altering the flat response to five other presets to taste is quick and simple.
Did Drewan77 tell us what crossover frequency he was using? If so, I missed it. Presumably that's the answer to the question posed by Soix.

In answer to Soix, I am running a LH and RH sub but I believe the signal is basically mono. I don't think this is important because at these sort of frequencies the bass notes are not directional
Answering Dbphd, my setub is as follows:

2 subs, crossing to Open baffles containing four aluminium/magnesium midrange drivers per speaker and a ribbon tweeter (d'appolito array)

0-100Hz both subs, 48db LR crossover on subs, 60db LR crossover on mains (this gives symmetrical slopes on the filter)

100hz-3100hz 48db Linear crossover to ribbon tweeters

Calibrated, corrected, aligned, eq'd measure basically flat 16hz to 20khz in room

For most recordings this blend of crossover slopes gives a 'faultlessly' smooth performance and I never notice the slightest hint of a dip or boom in the sound, even in the bass region. Music is extremely realistic sounding, has great timing and the most dynamic response I could possibly want. Transients are simply stunning, fast, tight and deep which I guess comes from the speed of the open midrange (uncoloured by cabinets 100hz up) and the fact that all drivers only receive the optimum frequencies they are calibrated for

As the DEQX has four profiles, switchable by remote, two also use 72db LR crossovers between subs and mains with the benefit that bass is even tighter and faster when certain recordings benefit. The flip side is that this is also slightly leaner in the mid bass area of the crossover, very pleasing on a slightly muddy recording. Steeper slopes mean speakers only receive the specific frequencies specified and DEQX is smart enough to handle the time delays and phasing in the crossover seamlessly.

I tried crossovers to the ribbons with slopes from 48db all the way up to 'brick wall' 300db but the steepest required phase inversion at the crossover to avoid very slight ringing. I have settled on a 48db slope as being the most natural sounding and chose 3100hz as the point where both frequency plots were completely in phase and both driver types had similarly flat responses either side of the crossover.

I would say that achieving exactly what I wanted has taken about 5 months of continuous tweaking. I finally arrived at this back in early June and have changed nothing since. I genuinely have nothing more to change, it's as close to live music as I have heard (better than the majority because it is so clean)- I spend a lot of time at gigs and concerts.

Is my understanding that the speakers are mounted on a baffle of sufficient size that front-rear cancellation is handled without an enclosure correct?

The answer I was alluding to in my previous post was the answer you gave to Soix, i.e., very LF are essentially not directional. Two subs are used to smooth LF sound field, not to provide stereo information.

Yes that is correct, the baffle is made from 25mm thick zebrano bamboo, a very dense material which seems acoustically dead. The subs are not directional, as you say

My own experience would suggest a few things, all of which have already been mentioned, but none of which may be clear from the debate:

If you lack bass management software in your system, an array of four optimally placed subs is likely to provide significantly smoother bass response at your listening position than an optimally placed single or dual subwoofer set-up. If you DO use bass management, the delta in performance between more subs and fewer subs at your primary listening position is likely to be smaller. IME (and I did try a decidedly poorly controlled A/B comparison at one point), a single (or pair of) bass managed sub(s) may well provide smoother response than a quad array of non-managed subs at the primary listening position.

However, you may still have smoother response over a large listening area with a "non-managed" quad subwoofer array vs a pair of managed subs - since bass management software IME optimizes response in a smallish window. As to optimal placement of such a quad array, you're on your own. Expert opinion seems to vary, so - if you end up with four subs - you should probably experiment with both in-corner and non-corner subwoofer placement to determine which sounds better.

As a practical matter, for a 2 channel, music only system, bass management software is still rare. In this case a quad array is likely to be the better choice. Once you introduce bass management software, the incremental value of additional subs is less dramatic. Of course, everyone has their own particular sweet spot on the curve of diminishing returns.

Since you're using an HT system, it's likely that you already have bass management software. If that is the case, the primary advantage of adding additional subs is the incremental gain in clean output capability at any given frequency. Even the best subwoofers' distortion increases dramatically with SPL at very low frequencies (tho the best models offer mighty impressive performance in this regard). A single monster - like the 1812 - may provide more than enough output for you. Still, two 1812s will get you more. So, in this respect, (assuming the use of identical subwoofers) more subs are better than fewer subs. But IMO, the real question here is.... overkill. How much clean output capability do you really need?


How loud do you listen?
How big is your room?
How deep is the is the lowest frequency you care about reproducing cleanly?

IME, I'd say that a pair of high quality, high output 12" subs (SVS, Rythmik, HSU, etc) probably does the trick for most listeners in most HT rooms that have bass management systems. However, it's just not possible to say with certainty that it will be enough for you. You can always start there and add more if the need arises.

Good Luck,

Don't know if this is off-topic but what opinions might the posters' have about a set up like the Paradigm SUB-1 or SUB-2 instead of multiple subs in separate enclosures; that is, multiple drivers facing different directions in the same cabinet? The Paradigm subs have 2 ea drivers on three surfaces (facing different directions by 120 degrees). Would this arrangement provide some small measure of an effect similar to two (or more) subs oriented differently (as described in this thread)?


Full disclosure - I have a SUB-1, Maggies, and a Meridian g61r; the Maggies and SUB run "full range" with the sub's crossover at about 50Hz. I ran the Meridian room correction without the sub, then added the sub and ran the Paradigm PBK SW. The net result in my room as confirmed by over a half-dozen "golden ears" is that my room has a very, very uniform bass response. ghl
You're dealing there with a matter of likely increased efficiency, with more drivers or volume, power, etc. And, since the woofers are in pretty much the same acoustic location, it acts acoustically like a normal large subwoofer, in space. So, whether the output, freq depth, and ability to fill volume in a space is right with any given sub, in any given space, is a key there. OTher than that, how quality is the actual product and sub performance on it's it accurate and fast enough as a music sub to integrate with the system...does it hold together and make an effective home theater dynamic subwoofer, capable of reproducing explosions and heavy dynamic loads, etc?? These things are obvious considerations.
If all of the above are covered well with single subs in a system/room, then the question of multiple individual subwofers is more relevant for addressing issues like more needed bass volume/energy/output in a given space, getting more efficiency from the system (more muscle from the bass), and helping the systems bass acoustics, by trying to more evenly smooth out he bass modes, which are inevitable in most any practical size home theater environment. In case of the last issue, I think it's been proven that carefully place multiple subwoofers in a room, has some key acoustical benefits/advantages, that are worth noting.
My problem with multiple subs placed anywhere other than in either one location up near the front of the system, or flanking as stereo subs near main speakers, is that of PHASE ISSUES, from multiple seating locations, in relation to mono subwoofers at different distances from the listeners ears!!! And I've proven that this can be a BIG challenge to set up right, particularly in multiple seating arrangement setups! (once had a client who had two mega buck subs setup in different locations in a room, and the subs weren't making any noticible bass impact across the spectrum! The problem?..they were out of phase with each other, and at varying seating location distances, in relation to the speakers and the subs themselves! -an EASY problem to run into, I assure you - relocated the subs up front, fixed the problems, and super depth, impact, coherence, speed and effectiveness! problem solved, thx)
I MUCH favor keeping the subs in an inherent good singular location in the room, preferably up front (where crossover blends are MUCH MUCH easier), and where I can EQ the subs issues out then, and keep the phase and coherence of the system intact, regardless of the planned seating locations chosen. I think the vast majority of audio enthusiests would find this approach a much easier setup approach, with more foolproof results, and less chance for problem - better matching and blending, and so on.
Then again, if anyone wants to tell me how they can avoid having phase cancelation issues between two(or more) mono subwoofers, placed in half spaces of the room boundaries (sides, front, back, etc), with several rows of seating locations (or even sitting right next to one side sub, vs the one in the center front), in relation to other seats, and still not have phase cancelation issues, and lack of coherence between bass crossover and main speakers crossover frequencies, etc, then I'd sure like to know about! Cause I find nothing but problems with the multiple mono subs placed midwalls, all around the room, unless dealing with 1 or two seating locations only. And even then, nothing a good DSP EQ can fix on it's own, what's the point, I've always asked?
Much rather do multiple subs around the room, near each monitor, run in stereo individual channel configuration for each speaker in stead, in that case.