Best type of Sub to consider?


I'm not looking for a brand or model recommendation at this time, but rather the best type of sub to fit my room and system. If you access my System pics, you will see that I have open corners behind my speakers and that my Horning speakers are rear ported. This has caused some energy loss, especially in the bass when compared to my previous setup in my other home.

I am a newbie to subs and see different design types that fire up, down, up and down, and forward. There may be other variations. So, does any of this matter when applying the best design type to a room, my room? My knee-jerk reaction is to go with forward firing in my situation, but that's complete speculation on my part, so why I'm asking.
Kenny
kennythekey
The best subs I've tried are at Firehouse Sub. They've also got some huge variety of sauces that can fire you up, down, up and down and forward.
 
Why do you think you need a subwoofer?  Looking at your system pics, which are very cool, it looks like you've set up your system for the least amount of bass reinforcement.  I have no direct experience with Horning loudspeakers, but I speculate that they will not be an easy match for any subwoofer due to their efficiency and speed.  If you want more bass then either reposition your setup or go with a larger Horning model.
Wow is there way to make loudspeakers horny?
Kenny, you most likely will get as many differing opinions as Carter has pills (as in most audio related subjects). If you can find a dealer for JL Audio, and have a look/listen to them, and try to get a home trial.

That would be my first thought, but there are about as many manufacturers of subs these days as there are of speakers.

Or, you can try the trial-and-error method of buying used, try it out, if it's not your cup of tea, sell it and try a different one. That's a hassle, so a dealer try-out is most likely your best bet. 

You received some good advice regarding speaker placement, placing your Hornings closer to side/rear walls may reinforce the bass enough for you without a sub.

Good luck on your search,
Regards,
Dan
If mainly for two channel I would go with a sealed design ...but I would try it with your speaker ports plugged and unplugged.
onhwy61 - No choice, I do not have two closed corners anywhere in the house, except one tiny bedroom. What you see, is my only option. One advantage to this setup, is that my detail has gone up a couple of notches. Subwoofers were recommended by my Horning dealer, but he does not sell them.

Dan - Thanks, Yes my forward firing option that I had mentioned, was based on the JL Audio subs that I was checking out. However, I'm trying to avoid brand recommendations, and get down to the physics and applications for the different types of subs.So, regardless of brand name, does one firing direction have an advantage over another or not. And, which one would work best in my setup, if any? That's all I want to know.
Kenny


I agree with ricred1.
 A sealed design will provide better bass accuracy than a ported one.
Looking at your room, have you considered adding acoustic treatments?

Kenny my experience with subs is rather limited as well. I am satisfied with my passive 15" Tannoy and Crown amp, and an old Velodyne that I removed the passive radiator, used a new Eminence 12" driver and 500 Watt plate amp.

This does what I need (I think I've brought this up before). Bass is clean and musical, the Tannoy passive being a great match for my Tannoy main speakers. You'll just have find your way the best you can, I'm sure you'll get there in the end. 
It seems to me that the answer may depend on where you would want to place the sub(s), which in turn may depend on how much of the bass region you want to augment. And given that all of the woofers in your speakers apparently fire mainly toward the rear, and that essentially half of the area that they are firing toward is non-reflective open space, I suspect that you would want the augmentation to extend relatively high in frequency (e.g., perhaps even upwards of 100 Hz).

If so, I see only two placement possibilities that might make sense, both requiring two subs.

One would be to place a sub alongside the inner surface of each speaker, firing toward the wall just as the woofers in the speakers do. (I presume placing subs alongside the outer surface of the speakers would be unacceptable because it would impede traffic, and perhaps also for aesthetic reasons). Although I would have some concern about the vibrational effects that placement might have on your turntable and electronics.

The other possibility would be to place the subs against the wall, one at its left end and one at its right end, with them firing forward. Ideally the subs would be chosen to provide a means of introducing a variable delay of a few milliseconds into their outputs, so that their outputs could be time aligned with the wall reflections corresponding to the outputs of the woofers in the main speakers.

For either of those placements, and if my suspicion is correct that you would want to augment up to relatively high frequencies within the bass region, it seems to me that two front-firing subs would be the way to go.

Good luck. Regards,
-- Al

Al,
Thank you for your informative answer, because that's what I was looking for. I did speak to a sub manufacturer, who recommended that I place two subs behind my speakers about four inches from the walls. These subs fired down, and it made me wonder how this would differ and/or be an advantage, or not, over a forward firing design. In my mind, a forward firing design may help to take out the need to rely so much on closed corners. However, I must admit that my study of speaker design and sound wave physics is truly limited. My ears are everything, but as we know you cannot sample everything. I appreciate you wishing me luck, but I will do my best not to rely on that. Thanks again.
Kenny


ricred1 and gdnrbob,
Thanks. I have only been looking at sealed subs, and even in that category, there are all these different types. So, why I posted.

Dan,
Yes, I completely read your comments about your success with your Tannoys and Crown, so thank you. You're right, here I go again finding my way around.
I really love my Hsu Research ULS-15 Mk II sealed subwoofer.  It works very well with my listening, as well as with movies.  Here's  link to my review on the sub:

http://http//www.ayllonmedia.com/1/post/2015/10/does-the-hsu-fit-a-look-at-the-uls-15-mk2-subwoofer.html

Good luck,


Juan 

I greatly prefer the sealed over ported subs in almost all cases. I like the JL audio subs alot, after them the RELs.  The REL hookup procedure is nice if you dont have the outputs on your preamp, or dont want to purchase extra cables. In my experience subs have have improved soundstage presentation in every system I've had them in. Good luck
Juan - Thanks, but the link you provided is not working.

Tom - Good information. I wasn't thinking so much about the hookup. One of the brands I am considering is sealed, and the cable it comes with connects directly to my Horning speaker posts. Then, I read on another brand's website that this is an inferior design flaw. So, another can-of-worms that can be opened up.

I have to think, that if I owned full-range speakers with forward firing built-in woofers, I'd be in good shape. However, many full-range speakers place their woofers in different locations, so on the sides and in the rear, like mine. These different designs must be designed around an ideal room layout. My Hornings want corners because they're rear ported, for example. This makes me want to believe that stand-alone subs are the same, so how they fire should make a difference to how the room is laid out.

In contemplating the right fit for my room, my best guess would be to use forward firing subs, and to try placing them almost up against the inside sides of my Horning speakers. If not a design flaw, it would then be easiest to connect the subs directly to the Hornings. However, in doing this post, I'm trying to extract the science of these different designs, so to take some of the guesswork out and reduce the number of subs to try.

As to adding subs in the first place, I have always been a purist and never cared for them. This is mostly from way back in the day when I could not find coherency in the combination. I realize, that I'm going to have to put out some serious coin to keep up with my Hornings. In these current times, I have been blown over after listening to the likes of the big Cessaro's, for example, with their add-on and powered subs. So, matching becomes critical, and I want to believe today, that a combination can improve my sound quality.

l have also heard, that there are audiophiles out there who are using subs with their Horning speakers. Are there any of you out there?
Kenny
One of the brands I am considering is sealed, and the cable it comes with connects directly to my Horning speaker posts. Then, I read on another brand’s website that this is an inferior design flaw. So, another can-of-worms that can be opened up.
In most cases connecting a sub that provides speaker-level inputs to the terminals on your speakers will work fine. The circumstances I can envision in which it would not be a good idea, and might result in hum, noise, or other issues, would be:

1)If the amp(s) driving the speakers have outputs that are balanced, meaning that both the negative and positive output terminals have signals on them.

2) If the amp(s) driving the speakers have outputs that are bridged, meaning that both the negative and positive output terminals have signals on them.

3)In a few cases, such as certain ARC balanced amplifier designs, where the amp’s circuit ground is connected to its 4 ohm output terminal, rather than to the "common" output terminal.

4)In the case of certain older class D amplifier designs, where both the + and - output terminals of the amp are offset from ground by a large DC voltage.

In all other cases, which comprise the majority of amp designs, I don’t think there would be any problem at all doing that.

Regards,
-- Al

Kenny: I'll share my thoughts, though I don't know your main speaker (which, I gather is a modified Lowther-type driver augmented with woofers and depends on corner reinforcement):
1. If I had to choose between a coherent speaker that was optimized for its full range vs adding on subwoofers to augment the bass, I'd probably do everything I could first to optimize rather than add. I know you said you have no options, but looking at that room, the side facing the system looks like it has "corners" (I assume there are windows behind the blinds, so you might have to deal w/ inserting some kind of rigid panel behind the "corner" blinds when listening). Perhaps with cabling, power outlets and the like, it's too much of a pain.
2. The notion of feeding the woofer amp from your main amp isn't crazy- my Avantgardes are set up that way and though their woofers are driven by their own internal solid state amp, the thinking is that they take on the behavior of the main amp feeding them (in my case, a SET amp).  The cables to do this made a difference- I went through various "jumpers" before I arrived at one that sounded better than the others.
3. The woofer design may be less important than placement and dialing in- read some of the other threads here- about swarm woofers, about dipole kits to match the behavior of panels. 
4. I've been messing with subwoofers for a long time for music and was never happy, having had various Quad loudspeakers (electrostats) and then horns. (I didn't even bother trying to sub-woofer my Avantgardes until quite recently). Right now, I am achieving some improvement using an unmatched pair of subs, crossed low, no roll off of the main woofers, and have been fiddling with DSP. I didn't want the discontinuity typically associated with subs and planars or horns, and didn't want to muddy the midrange. I've managed to get it 'just so'- more foundation without screwing up the mids---
5. Your system looks like it came from Jeff at High Water, who has very good ears, and is a cool guy. Even if he doesn't sell subs, does he have any advice for you?

I know you're not looking for brand recommendations, but few subwoofers are designed intentionally to be placed in corners, as you want to.  I, too, place my two subwoofers in the front two corners of my room.  They are down-firing through a slot.  But you will see that many subwoofer users go through heroic efforts - bass traps, EQ, etc., to get good, somewhat flat bass response from corner-placed subwoofers.


That said, my Vandersteen 2Wq subs are specifically designed to perform best when placed in corners.  And I have found that they need little if any in the way of EQ or room treatments to compensate for corner placement.  I urge you to research this subwoofer and its unique hook-up scheme.  I think it might be a good fit for you.

Al - Again, great information, so thank you.

1) No, not balanced.

2) No, not bridged.

3) No, single-ended.

4) No, 300B SET.

Wow, four out of four!

Whart - Thank you, it sounds like you're having success with careful tweaking. Yes, the driver is a modified Lowther DX65.

1) This back wall that you see only has the one useable corner, so you're only seeing one half of the room. The other corner is 31' from the corner you see.

2) It would be great to know what jumpers you liked best.

3) Interesting, I'll look into those. And, an indication that design may not play such an important role.

4) That's very reassuring.

You got me there, because Jeff is my dealer. And, the best one I've ever had the fortune of meeting. He doesn't sell a subwoofer line, but he has spent a lot of time, setting up his Cessaro subs.

bondmanp - I think you may have misunderstood, because I don't have corners. If I did, I probably would not want subs.

Kenny

Your system suggests you would appreciate the sophistication of an OB/Dipole sub. A very unique one is available as a joint venture between GR Research and Rythmik Audio. The sub is not a normal Open Baffle sub, which are already unique enough, but an OB in an H-Frame, superior to a flat baffle because of it’s greater structural stiffness and non-resonance. And of course it’s open baffle design prevents the often boomy sound of even the best sealed subs.

A dipole sub excites the room modes of it’s front and back output, but not those of the room dimension to it’s sides, where there is a dipole null. There are a few OB/Dipole subs available, but the GR Research/Rythmik is unique in that the two (or three) 12" woofers (facing in opposite directions in the H-Frame) are Servo-controlled by the Rythmik plate amp. The amp also contains a 6dB/octave shelving circuit to offset the dipole front-to-back cancellation at very low frequencies.

The sub is offered as a kit only (one kit includes the amp and two---normally, though you can use three---12" woofers). The H-frame into which the kit is installed is available as an easily-assembled flat pack from a couple of wood workers who frequent the AudioCircle GR Research Forum. A pair of kits (for two subs) runs about $1500 shipped, and the flat pack (CNC cut from 1.5" MDF!) about $600. The highest sound quality, though not quantity, sub available.

Details of the design available on the GR Research and Rythmik Audio websites, and discussion of the sub on the Forum.
IMHO Servo flat plate amps and dedicated Open Baffle drivers naturally offer near flat bass response and do away with with nearly all the problems box subs cause as well as NEVER sound right. NO box sub can compete with a well made servo amp and 2 16 ohm 12" drivers for example. Or bigger or smaller for that matter. I like the 12's. 

I have the luxury of owning several systems and one of which has two Revel Rhythm2 subwoofers in it paired with Salon2's as well as all the goodies it needs to sound great and it's pretty good. Should be for $42K worth of speakers too however my GR RESEARCH Super V's I built (with those dual 12" drivers designed to go with these  by Rhythmic Audio's are sweet and simple as hell. They are the 370 PEQ  flat plate amp per side (I think they are called.  (thats a mere 370 watts vs. Revel's 2000 watts of blah blah blah BS is what it is.) the Super V's sound so much better in fact and without all the fancy dancy room correction LFO blahdie blahdie  blah digital crapola either, not even the onboard EQ switched on and dialed in eithe and it sounds 100 times better in every way with no nothing, no DSP, no room correction no nothin. I mean don't try messing up a room, but the room doesn't matter whereas with all other subs only the room matters. It's got to be darn near perfect and nobodies room is perfect ever.  For what, pennies in comparison too. In fact the sub's are for sale as are the Salon2. Who need this stuff when my kit speakers (on board subs) absolutely cream this other set up. It's kinda embarrassing frankly but live and learn. It's sad when you absolutely dial a super speaker and great subs in with super perfectly matched amps with super duper cables designed to extract the very best out of your room with that Synergistic Research Mojo KOOL AID crap too that works ever so incrementally it's sickening and more expensive the taking wonder trip around the world probably about 20 times or more. Simply all KOOL AID folks like all the other stuff. What a boatload, truck full, desert of KOOL AID. We don't need those ULTRA expensive cables either. What a complete smorgasbord of KOOL AID for the guzzling. I've finally learned. DO NOT DRINK ANY of it and keep your hard earned money. I truly hope I stop drinking that dam KOOL AID is all I can say because as always less is more and always will be. I"m serious about selling off this so called great Revel speakers too if anyone is interested. The Salon2 is a fine speaker actually as are the subs. I'll sell at my cost too. Got a bunch of stuff for sale actually, some super kool stuff too. Whoops I got off track here. So Sorry. I am serious about the sub's however, don't waste your money on much else I can honestly say. No JL, no REL, no Revel if you want absolutely killer sound that is or real sounding sound that actually helps your mains sound the best they'll ever sound. Not the worse, so you just keep struggling and spending and drinking, something, like KOOL AID. Check out Servo amps and nice big drivers and you'll be glad you did. GR Research sells them as does Rhythmic Audio and a whole slew of others too I'm sure. For that matter buy some open baffle speakers while your at too and hear the dam music you've been trying hearing for so dam long. No all OB speakers are created equal but most will have you tapping your toes like never before and stop that frustrating feeling of being had all the time. NO MORE KOOL AID should be every person that wants a simple great life new chant. Thats not a plug either it's just an honest recommendation. I have no reason to give them business except I think the stuff is great and totally underestimated across the board. NO subwoofer is going to sound as musical as these puppies. God's honest truth too. An expert audio engineer could work for 1000 hours trying to EQ, Room Correct, Add Bass traps and you name it and it'll never sound as good as just turning on a pair of dual 12"'s driver by servo amps. Not even close. The amount of frustration saved is worth every cent of the cost and more. You'll actually be able to listen to your music opposed to fussing with the horrendous task of trying to crossover some sub with your mains whereas it's not even really possible in 99% of all rooms no matter what anyone says. Oh you'll get noise or sound but it'll be nothing like those servo amps plates and OB drivers. Is the end all. I don't know but it sure as hell beats beating one's head against the wall buying XLR, Single ended, short long cables bass traps DSP bulloney with no mustard and all that nonsense and software no one car run and special Mic's that are nonsense bluetooth thingamajigs' for what. NOTHING. Mark my words folks and try making your mains sound right. you won't no matter what anyone selling KOOL AID tells you, ever. Sorry for all the typo's and my scatterbrain ADHD blather but for what it's worth there might just be something to what I'm saying here.
bdp24 - Thank you for the recommendation and I did visit both sites, but I'm having some difficulty in identifying the sub kit. Can you help with that?

jwt - Your compassion and enthusiasm about these products is certainly there. And, I'm very happy that you discovered reasonable products that get the job done right for you.

A quick question for both of you, can/will these companies send me sample products to try? Or, do I have to build this myself to find out? I won't buy something like this without hearing it first.
Kenny
Okay, so I found a link on the Rhythmik site for Salkaudio, who builds their subs. They refer to them as sealed, and on the Rhythmik site they offer plans for both sealed and ported. And, back on the Salkaudio site the pics show forward firing subs, but a picture of the baffle design has the sub firing down. What's the recommended fit here? I believe, I understand that the baffle design is open even though in a box, but I need help sorting out the rest of this.
Kenny

Kenny, I understand your confusion. The subs Salk Audio offers are the standard Rythmik sealed (either 12" or 15"). Jim Salk installs the same DIY kit you yourself can buy from Rythmik, and installs it in his own larger (4cu.ft. vs Rythmik’s 3cu.ft for the 15"), better braced, beautifully finished enclosure. The OB/Dipole sub is not offered by Salk, and is a completely different animal.

Before getting to the OB/Dipole though, yes, you can try out any of the Rythmik subs (for 30 days I believe, but don’t quote me), paying only for shipping if you send them back. They offer a bunch of different models, both sealed and ported, with 8", 12", 15", and soon, 18" woofers. Also a number of different plate amps, with different power ratings and control features. What they all have in common is the Rythmik patented Direct Servo Feedback design of owner Brian Ding.

The OB/Dipole sub is a joint venture by Rythmik and Danny Richie of GR Research. Danny was already designing OB speakers, and when he learned of the Rythmik design, he envisioned the mating of it with a dipole sub, and contacted Brian. They put their heads together, and co-designed the OB/Dipole sub.

The sub is not available as a ready-built, try-it-before-you-buy-it product, but only as a DIY kit. Don’t let that scare you away---there is a fairly easy way around that. You can see the kit listed on the Rythmik website, on the DIY/Kit page. It consists of the Rythmik A370 plate amp and a pair of 12" Open Baffle woofers, for one channel---two kits required for a stereo pair obviously.

But Brian does not actively promote the OB sub, Danny does. I have suggested to Danny that he make a listing for the OB/Dipole Sub kit on the GR Research site, but he hasn’t gotten around to it yet. You can find information on it buried in the listing for the 12" woofer in the "Drivers" section of his product listings.

But where you really want to go to read about the sub is on the AudioCircle GR Research Forum, where there are several threads discussing the OB/Dipole sub, with pictures posted by those who have made them. It is also there you will find the makers of the H-Frame that the kit is installed in. The frame is offered as a flat pack, and is not much harder to assemble than Ikea furniture. Anyone not wanting to have to do that could have a cabinet maker assemble it in a couple of hours, then paint or veneer the MDF (1.5" thick!) it is made of.

Check it out, it’s really special. The OB/Dipole sub has been incorporated into several full-range speakers, among them The GR Research Super-V (which was awarded "Best Bass at the Show" for several years at RMAF) and Serenity Acoustics Super 7.

bdp24, Thanks for directing me to more specific information, because things are becoming more clear. At least, I know why I'm having trouble zeroing in on these. I think my best course of action would be to contact these guys directly.

Both websites don't really get to the heart of the matter and it makes one wonder (me), how special can this pairing actually be when here are their other products/kits but where's this one? You're right, they should have a page for the OB/Dipole Kit even if it's just an overview.

Thank you for sharing your thoughts and recommendations.

Kenny

Hi Kenny,

As my said the OB design is without peer IMO unless you enjoy adjusting and moving subs all over the darn place to find out there's no good place for it and integration is impossible. 

I've never heard a box sub integrate properly. Not once. Remember I'm the guy with two $10K subs too. 

Only the OB Servo driven subs are the most room friendly subs there is.




bdp24- that is what I'm talking about. Imagine 3-12" drivers driven by one 370 watt amp per side. WHOA is all I can say and button down the hold downs. 

Best type of Sub to consider?

For the tightest, punchiest, most detailed lows, it would be expensive but the best would be a "Isobaric" designed sub, it will be large also too get the LF down low.

You’ll to have deep pockets and have to search to see if anyone makes a really good one.

This is how they work: http://www.vueaudio.com/isobaric-subwoofer-design/

Cheers George

What's interesting, is that the four woofers per Horning speaker in my system are in push-pull configuration and rear ported. I'm not sure if this is an isobaric design or not, but the bass can be excellent when set up properly. I've heard an almost identical system as mine at another audiophiles home with closed corners and careful setup, and the bass was wonderful.

l'm hoping to retain the extra detail that I've acquired, by the setup of my current system, plus reinforce the bass to the level that I've heard in that other system. That would do it for me.
Kenny

My experience is the best Isobaric setup is a sealed (no port ala Linn Isobaric speaker)), but the box then needs to be bigger to get the lowest frequencies.


Cheers George

Hey bdp24- 

For discussion purposes I'd like to point out if a person was so inclined to run 4 dual 12" servo driven OB subs in the H frames like mentioned. Just how great this set up naturally circumvents the need for room correction or EQ measures and that multiple subs self cancel standing waves quite nicely on top of all the other plus's. A person would have quite a mighty system for music or movies. I'll also mention for the cost of 4 dual 12" with the amps etc. being around what $3600 maybe. (not sure how much flat pack H frames run) but WOW is all I can say. If I were to do this from scratch realizing my room is 23X19'-6" and my IC's are would be well over 10' long, I'd opt for the balanced version in the amps (XLR) inputs and outputs. It's like $20 per XLR too reduce noise. 

Actually jwt, a pair of the OB/Dipole Sub kits is $1500 shipped, and a pair of the H-Frame flat packs is $600 I believe (I got in on the first few sets made at an introductory price). So it’s about $2100 for a pair of the OB/Dipole Subs and really good H-Frames, CNC cut from 1.5" thick MDF! All that’s left is finishing the frames, paint or veneer. Each sub contains a pair of 12" Servo-Feedback controlled woofers facing in opposite directions (they don’t have to be, but doing so creates a couple of benefits), and the Rythmik plate amp with a dipole cancellation compensation shelf to counterbalance the acoustic roll-off inherent in dipole speakers. The amp is available in a couple of different configurations, one being balanced/XLR in and out. One band PEQ is provided, as are high pass and low pass frequency and slope adjustments, three levels of electrical damping, and, most importantly, a 0-15ms Phase Control. Do NOT buy a sub without continuously variable phase adjustment. A 0/180 switch is worthless, and that’s exactly what most subs have. This sub is made specifically for music reproduction, being optimized for sound QUALITY, gladly sacrificing maximum sound quantity to get it. The output of a pair of the OB/Dipole subs is about equal to a single sealed Rythmik. Are you willing to give up 3dB in output to obtain the OB/Dipole sound quality? I was.

In addition to the lack of sealed or ported enclosure resonances, an OB/Dipole sub creates cleaner bass also because it excites only the room mode of the dimension it’s front and back faces. If you fire it down the length of your room, the room modes of the width of the room are NOT engaged---the null created to each side of the sub prevents it. So elegant!

The sub is absolutely and without question the best sub in the world for any and all planar loudspeakers. Not only does it’s Open Baffle design and construction provide the same advantages (and liabilities) as does the non-box design of planar speakers, but it’s dipole acoustical properties and behavior matches that of planars, unlike ANY box sub in the world. The acoustical output of dipoles drops off at only half the rate of boxed speakers; if you balance your speakers and box subs at one listening distance, that balance is different at a different listening distance, and in all other parts of the room. Not so with the OB/Dipole Sub, as it shares with OB and dipole speakers (which is what planars are, of course) the exact same acoustic SPL drop-off with distance rate. Again, elegant!

And I haven’t even brought up the benefits of the Rythmik Direct Servo-Feedback system, designed and patented by Rythmik owner Brian Ding. Not just another servo design, but a new, better one. You think the servo-feedback woofers in the Infinity IRS were clean? Wait until you hear this sub! It’s sound has been described as "stops on a dime". It's the only sub I've found that isn't embarrassed by my Magneplanar Tympani T-IV bass panels. NO overhang, no boom, no bloat. The Rythmik Audio/GR Research OB/Dipole Sub---the only Servo-Feedback OB/Dipole Subwoofer in the world!

Kennythekey, nice setup. I have Casta model C's which are 98 efficient with custom horns(midrange and tweeter) with 15" bass drivers in a sealed cabinet. Crazy sound comes out of these. Then I purchased a Rel G1 and I run it high pass to my Audiozen Noah dual mono amplifier. Simply stunning. I will be adding another in near future. I think two of them In between your left and right would be amazing. I have mine in dead centre between the left/right. The bass nearly knocks my over 15ft away. Tight chest bass, palpable, extremely musical.  I do think your wall behind the speakers should interact well with the sub. Check them out....

bdp24 - You have suggested that my system may benefit from the OB/Dipole Sub, but it seems like most users are driving these with planar loudspeakers. This post also acknowledges the pairing of these subs with planars.

For matching, why do you think these subs would match up so well with my Horning Aristotle speakers?

Thanks,

Kenny

Good catch Kenny---your thought had occurred to me after my last post. One point of stating how well the OB/Dipole Sub works with planars is because they (planars) are so notoriously difficult with which to get a sub to blend seamlessly. If a sub will work with a planar, it will have no trouble doing so with any speaker is the logic. But is it true?

The OB/Dipole Sub has been successfully mated with a pro sound high efficiency 15" coax driver on an open baffle (in the Rythmik Super-V loudspeaker)---read reports on the RMAF from a few years ago to see the reaction at the Show to it's bass capabilities, with NEO 10 and NEO 3 planar-magnetics (in the Serenity Acoustics Super 7), with sealed and ported box speakers, with open baffle/cone monitor speakers having either a 5" or 6.5" midrange driver and dome tweeter, with Eminent Technology magnetic-planars, Quad ESL's, horn-loaded high-efficiency direct radiators, and by Ric Schultz in his own EVS speaker design. Ric is one of the Subs biggest fans and proponents.

If a sub sounds extremely clean and non-boomy, with no overhang, no box resonances, and an ability to excite fewer room modes than a box sub, why WOULDN'T it blend well with any loudspeaker you could name? As to working with your loudspeaker to your satisfaction Kenny, you would probably be the first to try! If the Sub sounds at all promising, I would suggest going to the AudioCircle GR Research Forum and reading the threads dedicated to the discussion of the Sub. There you will find not only the opinion of the Sub by those who have bought it, but also pictures of many different builds, some of them quite interesting to look at. In all the discussion of the Sub, I don't believe there is a single instance of disappointment by an owner.

Gradient designed and built an OB/Dipole H-Frame sub for the Quad 63 in the 80's, and REG at TAS loved it. Loudspeaker/crossover design expert Siegfried Linkwitz offers a DIY loudspeaker incorporating an OB/Dipole bass section in a W-Frame, a frame rather flimsy and under-braced in comparison to the very robust H-Frame offered for the GR Research Sub. And there are several other designers catering to the DIY crowd offering Open Baffle subs (not in a W- or H-Frame, but on a flat baffle) for use with OB speakers. Open Baffle subs have long been known to provide a unique, very different sound from "normal" subs, a sound characterized as "lean". As in no boom, no bloat, no overhang, no box resonances, and less excitation of room modes. And the Direct Servo-Feedback design of Rythmik itself is known for IT'S unique sound, one that prompted loudspeaker designer and manufacturer Jim Salk to incorporate it---the product of another speaker designer!---into his top models. It is the combination of the OB/Dipole design combined with the Servo-Feedback woofer control provided by Rythmik that makes the Sub so special. Really special.

bdp24 - Again, thank you for the enormous amount of quality information that you provided regarding the OB/Dipole design type by Rythmik/GC Research. My next step would be to speak to them directly and take it from there.

I also want to thank everyone for their contributions to my post. I now have hit the limit for what I can absorb and I need to start doing. From the various sub types available, I will start to request try-outs from key brands, and this may help to eliminate some who do not have a lending policy. For me, it's not about price, promises, or proclamations, but proof-of-sound in my system.

Kenny

That sound like a good start, Kenny.
Keep us informed as to what you end up liking.
This 'hobby' can be fun and very educational.
Bacardi, I missed your comments, so thanks.

gdnrbob - This may take awhile. I agree about the educational part, and eventual fun, but I just started thinking about shipping subwoofers multiple times, so where did I put the Teleporter?
Kenny
The guys at Rythmik quickly got back to me, so they checked out my system and room layout relating to integrating the OB/Dipole subs that have been recommended above. Unfortunately, they did not recommend the OB design with my dynamic speakers as they work best with planar speakers.
What is interesting, it was suggested adding a small sub upfront with a larger sub in the back. I'm now working out those details, because with two subs, I was looking for two channels. I'll wait to hear back and let you all know.
Kenny

Interesting. Just for additional background, I bought a 12 inch sealed unit from Brian at Rythmik recently, opted for the paper, rather than metal cone, and for cosmetics, had it finished in that piano ebony gloss (which may not look right with your aesthetic). I got the version of the plate amp with XLRs that allow me to daisy chain (which I'm not doing right now). The other woofer I'm using is a very old Velodyne 15" to which I added a small DSP unit, and cross it over really low. I am running the pair in stereo, adjusted to match the output of the 4 x 10" woofer array in my Avantgarde Duos. I am not rolling off the main speaker system through any external X-over, but running the subwoofers parallel to the main system from additional outputs on the back of my line stage. Although, as described, it is sounds a bit kludged together (and it is), it has worked very effectively. So, the idea of using two different sized subs isn't completely crazy. (I have another old sub, a Velodyne 18", which I didn't bring into the room- it's about the size and weight of a fully loaded coffin and it just seemed to be too much, and unnecessary). I am using the set up described as a stop-gap until I move and rebuild the system, where I'll revisit the whole speaker array. (Bigger horns, please!)  The bigger woofer sits further back into the room, behind the "line" of the main speakers and off in a corner; the Rhythmik is closer to my listening position on the other side of the room at a "jog" in the room so it has some "corner loading" but it is more mid-wall, if that makes any sense. Using some pretty simple tools, including a db meter, some of the basic measurement tools that come with that Studio Six app for iPad as well as my ears, I was able to adjust the volume, crossover and phase in a way that pretty harmoniously adds weight, depth and gives me more of a front to back effect without doing violence to the glorious midrange of the X-overless mid horn and SET amps.
For what it's worth, my dealings with Rhythmik were very pleasant, Brian was responsive to my questions via email and phone, and the fit and finish, as well as the performance of the 12" woofer is pretty impressive for the $. So I guess you could call that an endorsement.
No surprise that Brian and Enrico at Rythmik steered you towards one of their "normal" subs (sealed or ported?), as the OB is more of Danny Richie's (GR Research) baby. No matter, a Rythmik is a Rythmik! I predict you are gonna be pleasantly surprised by how clean, clear, and "quick" their subs are. No boom, no bloat, all muscle, no fat. The Rythmik controls make integration with your mains invisible---no seam to be heard. Brian's servo makes Rythmik's the fastest subs on the market, bar none. Sterling Sound in NYC has multiple F15's in their monitoring systems, the ones George Marino listens through when doing his mastering for Mobile Fidelity and others.
George has passed, but there is probably a good mastering suite in heaven. 
Um, make that "listened".
Whart - I need to take a break from my busy day and call Brian and/or Enrico to get a better sense of the sealed and ported differences. The recommendation of two subs small and large had to do with the reflections advantage of my room's cathedral ceiling (small/up front), and my back wall (large/rear). This makes sense to me, but I also want subs for both channels. So, it makes me think that four subs may be overkill, and I'm looking for an alternative because there are a number of design types available just within Rythmik's line up of subs, for example.

bdp24 - There's a correct fit for me, so I just need to poke and prod until it reveals itself. I can also reach out to Danny. Hopefully, I can reach a consensus based on engineering advantages, from both companies, in support of what works best for me.

Thanks,
Kenny

Kenny, Danny and Brian worked on the OB/Dipole Sub together, Danny instigating the collaboration. Danny is an Open Baffle enthusiast, Brian not so much. When Brian heard the sub, he has said he found it to sound somewhat "lean", without the weight and fullness one expects from a sub. That leanness is one thing that makes it so special, and to work so well with highly transparent loudspeakers, which themselves sound lean (in comparison to the thick, slightly plump sound of so many box speakers).

In the "regular" Rythmik Sub line-up, Danny had input on only one model---the F12G, the "G" signifying GR Research, Danny’s company. The Rythmik F12 comes in two versions: the standard F12 (with a Rythmik 12" aluminum cone driver), and the aforementioned F12G (with a GR Research 12" paper cone driver). Danny feels the paper cone affords the F12G greater low-level resolution than does the F12’s aluminum cone (due to the lower mass of paper versus aluminum), and a more natural tonal balance (due to the resonant signatures of paper and aluminum). He recommends the F12G for a music-only system, the standard F12 only for use in a system in which it will be played at near maximum output, where the aluminum cone’s greater stiffness will be an advantage.

There are other Rythmik models with cones of paper, but they are budget models, not the top line F15 and F25 (dual 15’s). The difference between the F12 and the F15HP is, as you might expect, the 12" driver versus the 15" (greater cone area of course, but also greater maximum voice coil excursion), plus amplifier power---the F12 having a 370w amp, the F15HP a 600w one. The difference in price between the F12 and F15 is nominal; if I were getting a pair of sealed Rythmiks (which are slightly superior to the ported in terms of group delay and deepest frequency response), I would get a pair of F15HP’s.

In fact, I did! In addition to the OB/Dipoles, of course. But I bought mine as DIY kits, designing my own enclosures, buying the sheets of MDF, and having a cabinet maker cut them into flat packs which I then myself assembled. I made the internal volume of the enclosures 4cu.ft. vs. Rythmik’s 3cu.ft. (for greater efficiency and maximum output), and braced the hell out of them---1.5" Baltic Birch braces every 6", top-to-bottom, side-to-side, and from around the driver on the baffle to the rear panel. I also designed the enclosure as a box-within-a-box, leaving 1/2" between the inner and outer (with "ribs" supporting the inner), filling the 1/2" cavity with sand. Oh, they’re very quiet enclosures, almost non-resonant. And they weigh a ton! What price excellence? ;-)

All - There are two parts to this. The first is the quest to best match my room and system layout to a specific type(s) of sub(s). So, the science of it. I really don't care who makes the best sounding sub for me or for anyone else at this point. It would be good for me to make a distinction between sub type as it applies to best filling a room's layout (firing direction(s) and placement), and the subs type as it applies to its sound characteristics (sealed, ported, OB, horn, etc.). Is this possible? This is the second part about the sound, so if it can be separated would be another post.

Bdp24 - Again, you've provided a ton of excellent information, and even though some of it gets past what I'm needing right now, you have also revealed some important information about people and their own sound preferences when designing products. I did describe my system and room layout to Brian and Enrico, plus l let them know that I'm not trying to shake the rafters for a home theater system. Instead, I'm looking for a natural and authentic reproduction. I will reach out to Danny for his opinion.

Great idea, Kenny. Danny comes at subs from a perfectionist audiophile, music-centric point of view. Brian is an unusual sub designer in that his priority is also music reproduction, unlike the home-theater orientation of most sub designers. But GR Research subs are used in music-only systems, Rythmik’s as much in home theater systems as in music ones.

The servo-feedback Rythmiks have a "stop-on-a-dime" cleanness to them that makes ordinary subs sound like they are filling in the empty spaces with "noise"---the drivers don’t stop and come back to rest when the notes stop. Rythmiks have what Peter Moncrieff of IAR calls "inter-transient silence". No matter which Rythmik/GR Research sub model you choose, you will get that sound. When you talk to Danny, tell him Eric sent ya!

Kenny-

look and listen no further than REL.

There are a lot of Audiogon people who either have or have had various REL's. One of them posted a question on the Rythmik AVS Forum yesterday asking for recommendations of models for use with his speakers. He said he been satisfied with his REL's, but that they rolled off in the low 20's, and he wants subs that reach down into the teens. Rythmik sealed do that.

I contacted Danny from GR Research and he was a wealth of information. I wanted to know how an open baffle design would be an advantage in my room's layout. He responded, open baffle woofers don't load the room like a sealed or ported sub. So the OB woofers greatly minimize room boom.

Apparently, the OB Subs should not get placed close to a wall, but rather at least three feet from my back wall, which makes them a great setup if placed to the sides of my speakers.

Kenny

What’d I tell ya Kenny! Being a dipole, the OB sub has a null to each side, creating two benefits: First, it loads the depth dimension of the room, but not the width, exciting the longer, further apart nodes rather than the shorter, closer together one’s. Already you have gotten rid of one source of room boom. Second, the side nulls allow the OB sub to be placed right next to your main speakers should you wish to, or right up against a side wall if you have a narrow room. True, it has to be away from the wall behind it (like any dipole), but most speakers sound better there too. And here’s a bonus: the sub can be laid on it’s side and used as a base for a pair Quad ESL’s or other short speakers. That’s just what the Gradient OB/Dipole Sub made for the Quad 63 was. The difference here is that you have the much higher quality GR Research 12’ woofer, and the Rythmik Direct Servo-Feedback system controlling the dual woofers. As I said, a very special sub, one few people have heard but when do are blown away by.

By the way, you can see a pic of the OB/Dipole Sub in the current thread about Virtual Systems.