Stereo Subwoofer Pairing

If they are identical there will be no problem using the two!

I'm thinking about using either a used Rel T7 and a new Rel T7i or a used Rel T5i and a new Rel T5i with Magnepan .7's.  I have the T7 and the T5i in different systems right now.

Followup question on Rel's specifically.  Can I use a new i edition of the T series with the old T series?  Or are the model changes major enough that they won't sound similar.

That would be a question best answered by REL.
B

I asked rel.  I'll post their response here.

rjb1101,

     If you set it up just so, you could become the first human in the history of our species to be able to hear deep bass in stereo.  
     Where'd you get the idea that stereo subs would be a good idea? Or even discernable.  
     Sorry, stereo deep bass is a myth so it's probably best to keep your expectations very low to avoid the inevitable disappointment.
It's not too late to save some time and money and abandon this nonsense.

    Tim

I'm not expecting to here bass in stereo.  I just want a dedicated speaker per channel input so that the signal doesn't overlap.  A speaker can only play one analog signal at a time.  If you input two signals the speaker is only playing one of them. Whether it is a digital or analog summation of the two signals, I would rather have a 1:1 input output of the bass signal.  Even if it isn't a huge difference.

Hi rjb1101,

Recording engineers understand that human hearing is very good at perceiving the directionality or where in their environment mid-range and treble sounds are emanating from but very poor in perceiving the directionality of deep bass sounds.
This is why they often combine all the bass at or below a specific frequency and record this combined deep bass only on the left channel. So, even if we could determine the directionality of deep bass frequencies, the vast majority of recordings do not have deep bass on both l+r channels when played back by home stereo systems. Configuring one’s stereo playback system with separate subs for each channel, therefore, is not a very good method of achieving good bass response in a home environment.
The best method I’ve thus far discovered for very good bass response in virtually any room is the distributed bass array method sold commercially as the Audio Kinesis Swarm or Debra systems that sell for about $3,000 for a complete system. These systems are almost identical and consist of 4 (3’Hx1’Wx1’D) subs and a 1,000 watt sub amp. Here is an Absolute Sound review of the Swarm system:
www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
I have no financial interest in either system but I am a very satisfied user of the Debra system.
I suggest you’ll achieve much better bass response in your room with one of these systems than ’stereo subs’ are capable of.
Good luck,
Tim

What you want to do is set up a distributed node subwoofer system using  multiple subwoofers in different locations in the room this will smooth out bass nodes and peaks. You can use any brand to do so no real need to match manufacturers just frequency range phase and match levels.            http://www.gedlee.com/Papers/multiple%20subs.pdf

noble100

Where’d you get the idea that stereo subs would be a good idea? Or even discernable.

Use of multiple subs can minimize rooms nodes so, depending on the room, it can be an excellent solution to achieving flat in-room low frequency response.

... stereo deep bass is a myth ...

Not exactly. Depending on the phase of the LF signals, it is absolutely possible to hear bass in stereo.

" Use of multiple subs can minimize rooms nodes so, depending on the room, it can be an excellent solution to achieving flat in-room low frequency response."

Hi cleeds,
     Strictly speaking, your statement is true and has been scientifically and independently verified and documented by multiple acoustic engineers, including Dr. Geddes and Dr. O'Toole among others.  They've both published white papers on the subject if you're interested.  However, you failed to mention some details about their findings that are important to this discussion and for rjb1101 to know about.

     These scientists, through extensive testing and measuring, discovered that room bass nodes were consistently reduced as the number of subs was increased in a given room.   Yes, 2 subs are technically 'multiple subs' but they found that the use of 2 subs, while resulting in better in-room bass response than just a single sub if properly positioned, had the least affect on reducing room bass nodes. They basically concluded that the more subs in a given room the better the bass response becomes.  Not very surprising, right?
     Of course, they realized there's a practical limit to the number of subs people will accept in their rooms.  So they further stated that 3 to 4 subs, if properly positioned, would result in the elimination of the vast majority of bass room nodes in most rooms. This is the basis for Audio Kinesis utilizing 4 subs in both their distributed bass array systems.
    There is also a precise method of positioning each of the 4 subs for optimum bass response in any room that is based on Geddes and O'Toole's scientific research.  It's detailed in both Audio Kinesis manuals and I'll describe it if anyone is interested.  

    ." stereo deep bass is a myth ...

Not exactly. Depending on the phase of the LF signals, it is absolutely possible to hear bass in stereo."

     I have no knowledge of your statement being true and Dr. Geddes and Dr. O'Toole make no mention in any of their white papers of the ability of humans to perceive bass in stereo.  Most of the research I've read actually concludes the opposite; that humans have great difficulty discerning where LF sound waves are emanating from.
     I know I don't perceive LF sound waves are emanating from any of my 4 subs even though my listening chair sits between the 2 rear subs against opposing l+r walls in my 23 x 16' room and the 2 front subs are along my front wall -one behind each l+r speaker.  I perceive the bass as emanating from appropriate instruments and voices within the sound stage illusion I perceive as in front of me. 

     I willingly concede, however, that what I perceive as bass emanating from specific spots within the sound stage illusion is actually a form of perceiving stereo bass.  So, even though I'm unaware of any scientific proof verifying it, I believe hearing stereo bass is possible with the assistance of our brains because I've experienced it in my own system.  Sorry, thinking out loud.   
     From my experience, I think a more accurate statement is that we hear and feel the bass which our ears/brains perceive and assign or interpret as emanating from the proper instruments, voices and positions within the sound stage illusion our ears/brains are also perceiving and interpreting.

Tim

I have been using (and integrating) sub woofers in my music audio systems for years, 2.1 systems in the past, my current setup is a 2.2 setup, with a pair of identical models (both purchased new at the same time).
Though low bass sounds have a very long wavelength, so long it's difficult if not impossible to sense the direction they are coming from, I have found that having a pair of sub woofers gives the "visceral" experience of directionality to the bass, so I'd recommend installing a pair of subs of the same model.

Hi ejr1953,

     I think we're stating similar but slightly different things.
     You're stating you've been able to perceive 'stereo bass' in your system through the use of only 2 matching subs.
     I'm stating I've been able to perceive 'stereo bass'  in my system through the use of 4 matching subs precisely positioned.
    I don't question your results but I'm curious about and would like to learn a few things about your system compared to mine:

How did you determine the best room position for each of your subs?

Do you have equally good bass response throughout most of your room or is the bass response optimized for your listening position? 

     My thought is that you've optimized the bass response at a single listening position which is a significant accomplishment but bass response at other positions in your room are likely not optimized since the vast majority of room bass nodes are not eliminated with 2 subs in a given room but are with 4 subs strategically positioned.  You may not be concerned about this but I was striving for good bass response at all 7 of my room's seating positions for both music and ht.
       Please don't misunderstand my intentions.  I'm not concerned with claims that my system performs better than yours but rather with providing the OP with useful information about how 2 sub systems are not able to eliminate the vast majority of bass room nodes as 4 sub system are and, therefore, are unable to provide good bass response throughout virtually the entire room.  I think it's best he receives accurate info and let him decide for himself based on his circumstances and preferences.
     I just want to make sure he doesn't get the impression that a 2 sub system will perform equally as well as a 4 sub system.
Enjoy,
 Tim  

If this is a two channel system in a reasonably conventional room and your main speakers are making a soundstage at the listening position two subwoofers effectively placed should provide more than enough node free area at the listening position to begin with. 

I'd suggest using both your existing subwoofers with the .7s in a mono configuration as a starting point. Concentrate on finding their optimum room location which reduces the most room nodes.

If the REL cabling prevents your from locating your subs at most locations in your room you might consider running them using their low level inputs and very long economical interconnects from Blue Jeans or Monoprice cable to aid in their room location.

You should be able to mitigate your concern of what you term as overlap with proper crossover and gain. Frankly, I don't think this will be an issue especially if the subs are irregularly located in the room and running in mono.

When I compared a REL Studio III it worked best sourced from a low level signal processed through a Velodyne DD Optimization program. I am not a fan of REL subwoofers.  

  

Deep bass is not directional, and that has been shown by a lot of research. Yet, as some have argued here, it may sound as if these deep bass notes do indeed emanate from different speakers. The explanation is that the human brain uses the upper harmonics from the main speakers to locate the deep bass tones. You can do two simple tests. The first is to use only one subwoofer. Interestingly, and provided the sub has been integrated properly, even with one mono sub the deep bass will seem to come from the two main speakers. The second test is to use two stereo subs, but turn off the main speakers. You will not hear stereo, because the directional information from the main speakers is lost.

So you can happily connect two subs in mono and not lose anything. However, why not connect them in stereo anywany- is there a disadvantage to connecting two subs in stereo? Indeed there is, because two mono subs will produce the same signal, and will therefore be smoothed more completely by having two subs reproducing the same signal in different locations. This is why most experts and manufacturers suggest to connect two subs in mono.

Two subs are indeed better than one because they reduce room modes. Similarly four are even better, but this is a story of diminishing marginal returns.
In principle you have four ways to deal with room modes in a given room:
1 use dipole subs (Rythmik have a kit for a dipole sub). Dipoles excite far fewer room modes, so you address the problem at source. The disadvantages are that dipoles tend to be larger and require more power.
2 install bass traps. The down side is that they are big and ugly.
3 use multiple subs. Two are a big improvement, and four brings additional improvement.
4 use dsp room equalization like the Antimode 8033. Use this with one sub and the (big) improvement is quite localized. Use it with two and the improvement applies to a much larger area.

Ideally, you may want to use all four methods. In real life, a combination of two or three will already bring vast improvements. If you have a bit of space I would opt for two dipole subs combined with room eq. If the room is small and domestic tolerance limited, I would opt for two really small subs like the SVS SB1000 plus an Antimode. If you have space and the budget, by all means go for four.

Ideally subs should be the same model, but as long as they are not too different there should not be a problem. Two identical ones but with slightly different ages are not an issue at all. Speakers do indeed need to be broken in, but this does not normally take more than a few hours. With subs, you are unlikely to even notice (but wait for a few hours with the Antimode equalization).

willemj,

I'm new to subs and just about to integrate a couple in my system.

A commonly recommended crossover point for subs is 80Hz, which means the sub will also be still putting out sound above 80Hz.

That seems to be getting into the directional territory.  I've read numerous people say they can localize their subs when crossing over at that frequency.

80 Hz is common for HT. For music I prefer to use them below the main speaker's roll off frequency, i.e. rather lower, such as 35-50 Hz. That is also the advice from REL: set the low pass filter quite low, and the volume relatively high.

willemj

Deep bass is not directional, and that has been shown by a lot of research. Yet, as some have argued here, it may sound as if these deep bass notes do indeed emanate from different speakers. The explanation is that the human brain uses the upper harmonics from the main speakers to locate the deep bass tones.

It is absolutely true that harmonics can suggest that the bass you’re hearing is directional and often, when bass sounds directional, that’s the explanation. But it is not absolutely true that all bass is non-directional; differing phase between bass signals can create the impression of direction. That might be obvious if you really think about it, but it’s also been proven through research, including in work done on multichannel audio by Microsoft.

" Deep bass is not directional, and that has been shown by a lot of research. Yet, as some have argued here, it may sound as if these deep bass notes do indeed emanate from different speakers. The explanation is that the human brain uses the upper harmonics from the main speakers to locate the deep bass tones."

Hi willemj,

     Excellent post that really clarifies the forces at work.  I was starting to think that deep bass may be directional because I'm able to perceive the locations of deep bass instruments within my sound stage illusion in a very consistent and convincing manner. 
     Your explanation, that the human brain uses the upper harmonics of the deep bass emanating from my main speakers to locate the deep bass tones within the sound stage illusion, really helped me understand the forces at work and the reasons for my confusion. All 4 of my subs are run as mono signals and mentally making sense of the deep bass localization that I am perceiving was getting difficult.  Our brains may be the most valuable component in all our systems.   It's all clear to me now,  Thank you.
      I'm not aware of the OP's, rjb1101's, room size and budget so I'm not sure if he even has the space or funds for the ideal solution of a 4 sub distributed bass array system but agree that 2 subs are better than 1 as many have already stated.  
     Assuming he wants to use just 2 subs , I think it's more important for good bass response that there are 2 subs instead of 1 than it is that they match. 
     If  he's mainly concerned with good bass response at his listening position,  I'd suggest he run them as mono and position them in the following manner:

1. Position sub#1 at his listening position and play music with good and repetitive bass.
2. Slowly walk across your front wall from right to left and find the exact location that the bass on the music sounds best to you and place sub#1 at this spot. If you prefer accurate and natural bass, avoid placing sub#1 in a corner.
3. Place sub#2 at your listening position and play the music with the good and repetitive bass again
4. Slowly walk along your left wall, from front to back, and find the exact location that the bass on the music sounds best to you.  Place sub#2 at this spot again avoiding corner placement if possible.
5.  Sit at your listening position and play the same music again.  If the bass response is not very good, start again from the beginning.  Remember, even small adjustments in positioning can affect bass performance at your listening position.

    In most rooms, 2 subs perform best with an asymmetrical positioning scheme; that is, with one along the front wall and one along a side wall rather than symmetrically with both placed along the front wall with one placed behind each speaker. 
    If you really prefer both subs along your front wall behind your speakers, however, you could try this by substituting the following for step #4 above: 
   Slowly walk along your front wall, from sub#1 to the left, and find the exact location that the bass on the music sounds best to you. Place sub#2 at this spot again avoiding corner placement if possible.
     The only way you'll discover which positioning scheme sounds best to you in your room is to try them both. 
     I'm almost certain that you'd get better bass response in your room, and certainly better bass response throughout your entire room and not just at your listening position,if you utilized 4 subs in your room rather than 2,  but you may have constraints I'm unaware of.  I hope this post was helpful to you.
  
Best wishes,
   Tim

FWIW
I employ a pair of inexpensive Andrew Jones powered subs with either my Sonus Faber Cremona Auditor M Monitors or Magnepan .7 speakers.

One sub is in the right corner of the front wall, the other in the left corner of the rear wall. I experimented with numerous placement arrangements and after a great expenditure of time I decided that this basic configuration yielded the best results. It works quite well.

Sometimes satisfying home audio is not beholden to the number of angels which theoretically can fit on the head of a pin. Simple is often best.

I use 2 differing REL models from the same era (Q150e, Q108 MKII) wired together getting their signal from the main tube amp. With bass I've found that the tone indicating where a bass is in the mix comes from whatever higher frequency overtones (or simply tones) are there so they're basically mono in their low range duties. 2 subs work better though to smooth out room nodes as perceived from the listening spot, with one sub (the larger Q150) right behind the left speaker, and the other against the right wall so I can stick it in a window for deck listening (with a couple of monitors also stuck in the windows powered by another amp). I agree that keeping the RELs lower (but properly matched to the mains) with higher gain works best. 

The Antimode engineers recommend corner placement for maximum reinforcement and minimal dips/nulls. That position unfortunately also gives the biggest peaks, but you can deal with those with the room eq.

" The Antimode engineers recommend corner placement for maximum reinforcement and minimal dips/nulls. That position unfortunately also gives the biggest peaks, but you can deal with those with the room eq."

Hi willemj,
     
     Yes, I've found that corner placement of subs results in the most bass due to the long bass sound waves reflecting off of both walls in a corner. This often results in bass peaks (exaggerated bass) at spots in the room. That's why I advised against it although some may like it.
     I've found avoiding placing subs in the corner results in more accurate and natural bass response which I prefer.
    I remember you mentioning your Antimode DSP room eq unit before .  I  use zero DSP, eq and bass room treatments in my room since I haven't found a need to since employing the 4 sub system. It's almost magical how this system eliminates bass nodes in the room and just provides accurate, natural and, when the source calls for it, very deep  and powerful bass on both music and ht.  
               

I plant to try one of my subs in the bay window area behind my listening sofa.  On one hand there isn't tons of room back there - a space about 8 feet by 3 feet deep.  On one hand I imagine bass frequencies "building up" in that space.  On the other, the sub would be between the bay windows and a massive custom sofa that spans the whole room width, and I'd think this would also provide some "trapping" as well.  I'm not sure how what to expect, but the other subwoofer will be on my front all behind my speakers, to the right, so the subs will end up on a roughly "diagonal room placement" which apparently is one that can work out well.

I hope.

As promised, here is Rel's response about using the T and the T/i models together:

With careful tuning using the rear panel controls, it's very possible to tune in a T/I with an older T. Just remember that the T/I will sound much faster and more lear/forceful down low so it will be down to careful placement and tuning but, yes, with little good judgement, you should be able to pull them together into a very good result.

Because room acoustics take precedence I can't give you a "turn this knob to this setting" sort of cookbook set-up. Just take it slowly--get the first unit dialed-in to its speaker, then unplug the Speakon and do the same for the other side. Then it will just be down to turning the volume on each REL down util the combined gain is right since the subs will be a little hot once both RELs are plugged back in.

Thanks for the question!

Hi rjb1101,

     Overall, that's good news.  I still think you'll get the best bass response in your room by following the sub locating method I outlined on my 1/28/18 post.  
     Since REL has confirmed what you already knew (that the T/1 is a better performer than your older REL) that means the T/1 will likely be the predominate influence on bass response performance you perceive in your room.  I'd therefore suggest that you consider your T/1 as sub#1 and locate it in your room 1st with all its controls set at midpoint settings.
     Even though your older REL is not as good of a performer, I still think its inclusion as sub#2 (also with all is controls set at midpoint settings) will help reduce bass nodes in your room and result in better bass response overall if you follow the setup procedure faithfully.
     Just in case you're not completely satisfied with overall bass response from your listening position after completing the setup procedure, you may want to try increasing the volume on sub#2 by about 5% and repeating steps 4 and 5. 
     Then keep doing this, increasing sub#2's volume by about 5% until you are completely satisfied wth the overall bass response in your room.
     If you never reach a point of complete satisfaction with the overall bass response. I think you'll only have a few additional options to try:

1. Sell your older REL, upgrade to 2 T/1 subs and start the sub lcating procedure from the beginning.  

2. Add a third REL as sub#3, set all 3 subs at midpoint settings and start the sub locating procedure from the beginning.

3. Sell both your subs, by an Audio Kinesis 4-sub Swarm or Debra system, set it up, sit back and enjoy great bass response in your system(s) for the rest of your life no matter what stereo 2 channel or surround speakers you use and no matter what room you're ever using.

     I completely understand not being able to afford, and then not wanting to spend, $3K for a state of the art bass system.  I actually started out many years ago in my search for better bass by borrowing a 2nd sub from a friend and spent many hours researching about room bass response on-line and experimenting with positioning these subs trying to attain better bass in my system.   
     The best bass I ever attained with 2 subs was with 1 along the front wall and 1 along a side wall 2/3rds of the way from the front wall, fairly close to my listening position.  I was honestly satisfied with the bass response in this setup for awhile for both music and ht.

     I never tried 3 subs but was seriously considering buying 2 new hi-end subs (like JL, Vandersteen or REL) when I became aware of the distributed bass array systems using 3-4 subs. I increasingly became tempted to try one the more I read about them, by the great professional reviews and by James Romeyn at James Romeyn-Music and Audio, LLC  in Utah who offered me a 45 day free in-home trial on the Audio Kinesis Debra 4-sub system he sells.
      I still considered $3K a lot of money for good bass but rationalized it by the fact I would spend that much or more for 2 of the larger traditional hi-end subs I was considering and there was no financial risk.
     I had my friend. Dave, help me faithfully position each sub according to the procedure.  The result was that 2 subs wound up along the front wall (one behind each of my panel front l+r spkrs a few feet away from each corner) and the other 2 along the side walls (one on each wall a few feet away from the rear corners).
      We were both a bit lazy after hours of moving the 4 50lb. subs around my room  and hooking everything up. So we just threw in that Brad Pitt tank movie I had watched the night before in the Bluray player to test things out a bit. It only took listening to one of the first previews, of the movie Whiplash about a drummer, to have us both smiling and gushing about the great bass response.  Bass so 'live in the room' real, sounding so pitch perfect good and solidly physically felt in our chests that we both were left just shaking our heads in disbelief with the dopiest smiles on our faces.
     With this system's performance in the 2 years since, I don't think I can overstate how good the bass response is; I could go on and on but I've done so long enough and will just state that, in my experience in my room, the difference in performance of 2 decent subs and the 4-sub Audio Kinesis Debra system driven by a dedicated 1,000 watt amp is like night and day. 
     I related the above to emphasize how well the distributed bass array 4-sub system actually performs but I realize my words will always fall short of  experiencing one properly setup. I can assure you you'll not have a desire or need to ever consider buying another sub again.
     Sorry about all the superlatives and going on so long,
             Tim   

noble100,

That swarm subwoofer system looks interesting.  I'll have to give it a listen at some point and keep it in mind for the future.  $3k isn't really out of my budget, but I was planning on using that $3k to split my 2ch setup from my HT setup and I don't currently have enough space for 4 subs as I live in a 1 bedroom apartment.  Plus those won't pass the WAF and toddler test with the exposed front facing cones.

One day when I own a home with a dedicated listening room, I will have to circle back to them.

I might be able to swing 4x T5 subs because the Paino Black Gloss finish and compact form factor are WAF approved.

Note that one should try listening with the subs and main speakers placed well out into the room while you wedge yourself into a corner to listen. This might seem ridiculous, but as an audiophile (and hey…aren't we all?) you should try everything possible to hear all sonic options, or, like myself, don't.

I've heard of putting the subs speakers in the listening position and moving around the room to find the ideal spot for each speaker.  (Mostly for subs).

I hate to hijack the tread, but noble's post has me scratching my head.

How do you hook up 3 or more subs to a stereo amp?
I have 2 2wq's and stack spades on the amp, but when you go to 3 subs, how do you connect them? Or, are you using a HT amp?
Bob

" 3k isn't really out of my budget, but I was planning on using that $3k to split my 2ch setup from my HT setup and I don't currently have enough space for 4 subs as I live in a 1 bedroom apartment. Plus those won't pass the WAF and toddler test with the exposed front facing cones."

Hi rjb1101,     
     I completely understand having big system plans, living in a smaller place, being concerned about the WAF and having a little smelly or two running around.  Hang in there, work hard.smart and stay frosty and things just seem to start getting roomier and calmer.
     In the meantime, I have a few questions and suggestions:
Is there a reason you want to split your 2ch setup from your ht setup?  In a small space it may be more advantageous to keep them combined until you have more space.  I still prefer a combo system more out of convenience than lack of space.   

Just an fyi about exposed front facing woofers on the Swarm and Debra subs; the subs have no grilles but are placed facing the wall with only about 1-2 inches of separation.  Weird but it definitely works well.

I have very little doubt you'll be exploring a distributed bass array system in your future but I'm thinking that, given your current circumstances, you may discover a better short term solution by trying my and wolf garcia's alternative configuration suggestions.

     I now think of the concept of the number of subs (1,2,3 or 4) in a good bass system less as performance absolutes and more in terms of good, better, best.  I know through personal experience and scientific verification that room bass response improves as the number of subs in any given room is increased. 
      But, as several others on this thread have attested, very good in-room bass response can be attained through fewer than 4 subs.  The common denominators seems to be more than 1 sub,  experimentation and careful positioning. 
     I'm tending to think your best option may be using 2 good subs in the short term  (such as 2 T/1s or 2 T5s) and experimenting with precise placements of each, especially if you're satisfied with optimizing bass response at a single listening position.

Best wishes,
  Tim