• Welcome to The Audio Annex! If you have any trouble logging in or signing up, please contact 'admin - at - theaudioannex.com'. Enjoy!
  • HTTPS (secure web browser connection) has been enabled - just add "https://" to the start of the URL in your address bar, e.g. "https://theaudioannex.com/forum/"
  • Congratulations! If you're seeing this notice, it means you're connected to the new server. Go ahead and post as usual, enjoy!
  • I've just upgraded the forum software to Xenforo 2.0. Please let me know if you have any problems with it. I'm still working on installing styles... coming soon.

Multiple Subs Article in S&V

D

Deleted member 133

Guest
In case most of you missed it, Brent Butterworth (one of the very few audio journalists / writers that I have any respect for nowadays) wrote a pretty good feature article on multiple subs in the current edition of S&V. He does a very good job of setting up a credible "experiment" comparing 4, 2, and 1 sub configurations, and identifies all of the needed caveats involved for such a comparison. The overall lessons learned / conclusions are not particularly surprising - at least not to me - but worthwhile reading nevertheless.

Jeff Mackwood
 

MatthewB

Grandmaster Pimp Daddy
Famous
Jeff it should be mentioned that Brent used similar parameters to each sub. he used one expensive 15" sub (retail 1500) two 12" subs (retail 1500 for both) and four 8" subs (retail 1500 for all four) all were constructed by Brent with similar mdf and amp power. It was a good read and funny how he got good and bad for all subs used, hence why when you all tease me about my multiple subs (remember I am using one 8" mid bass sub, three 10" mid bass subs and one dual 12" SVS just for the lower frequencies, and I get what in essence the best of multiple subs and all the goods that Brent experienced with none of the bad. )
 
D

Deleted member 133

Guest
Alien said:
I'd just put one on top of the other. No harm no foul.

Wow! Hard to believe that the most important subject of subwoofers has gone a full month with no posts. So I thought I'd pick on Alien's comment to generate some additional discussion.

Let's assume that Alien was talking about stacking identical subs. To my point of view, that has the benefit of increasing output across all frequencies served by those subs; or another way of looking at it is that at any given level of total bass output in the subs' range, each sub is having to work less hard. Stacking also preserves floor space.

But I doubt that it does anything with respect to one benefit of multiple (again in this case, to simplify discussion, identical) subs: smoothing out of bass response throughout the room.

I do suppose that stacking could lead to bass extension - but only if some form of room correction / EQ were used. (Reason: more output across the entire range means more output at lowest frequencies reproduced. Where output might be down by say 6dB at a given low frequency, it may now be down by only 3dB. But since output is also up at higher frequencies, EQ/correction would come in handy to knock those back to achieve a flatter response across the entire range. At least the way I see it.)

I think that if space permits, the much better approach would be to distribute the subs around the room to find an arrangement that yields the best comibination of extension, level, and smoothness (to cite what I think are the three objectives of the exercise.)

These comments are to be taken in the context of the Butterworth S&V article an his findings stated therein.

But of course there's also a ton a variations (and variables) when you start talking about non-identical multiple subs - like Matt and I use.

Jeff Mackwood
 

Randy

Well-Known Member
Famous
From the article they said 4 identical subs located in the centers of the 4 walls was optimal fro smoothing out response. Then, 4 identical subs in the 4 corners was next.

I have a white paper somewhere from Harmon Kardon (I think) that states the same thing. I may try to find it when I get home from work tomorrow.
 

MatthewB

Grandmaster Pimp Daddy
Famous
I belive so. When at both Flints place and Bats last gtg they both used dual subs and with both they're rooms being treated I heard no reason for the need for any more subs in either room. The subs in both rooms sounded very smooth and well controlled and in Flints case overwhelming in certain scenes. Maybe cause we were blasting those IB's
 

Razz

Well-Known Member
MatthewB said:
I belive so. When at both Flints place and Bats last gtg they both used dual subs and with both they're rooms being treated I heard no reason for the need for any more subs in either room. The subs in both rooms sounded very smooth and well controlled and in Flints case overwhelming in certain scenes. Maybe cause we were blasting those IB's

I also remember the two medium size Dynaudio 500 subs could not keep up with the single SVS ultra 13. There was a significant difference in LFE volume produced by the SVS. They were all positioned up front too so I think quality and design of subs will have a big effect just like the number of subs and placement..... so many factors.
 

Randy

Well-Known Member
Famous
Absolutely Razz,
That has been one of Flint's big things for years. Two lesser subs will not necessarily outperform one good sub. Buy the best sub you can afford, unless you are filthy stinkin rich and then buy 4 of the best subs you can afford. LOL

Or build a wicked IB.
 

Flint

Dog Faced Pony Soldier
Superstar
I love to see a spectral analysis of the thd+noise from the output of four subs placed for smoothest response next to the same measurement of a single sub costing same as the four subs placed most ideally in the same room. Considering the potential for four unique arrival times with four subs (the primary cause of the flat response), the noise and harmonic distortion is very likely to be much higher. Heck, add a phase measurement too.

I've heard dozens of multi-sub setups with a measurably flat amplitude response which sounded dull and lifeless when compared similar priced single sub setups. The bass should be subtle, detailed, and tactile not big, smooth and flat.

Matt - When sitting in the sweet spot I have effectively one sub and only one sub. I don't like it when you refer to it as two.
 
D

Deleted member 133

Guest
Flint said:
I love to see a spectral analysis of the thd+noise from the output of four subs placed for smoothest response next to the same measurement of a single sub costing same as the four subs placed most ideally in the same room. Considering the potential for four unique arrival times with four subs (the primary cause of the flat response), the noise and harmonic distortion is very likely to be much higher. Heck, add a phase measurement too.

I've heard dozens of multi-sub setups with a measurably flat amplitude response which sounded dull and lifeless when compared similar priced single sub setups. The bass should be subtle, detailed, and tactile not big, smooth and flat.

Matt - When sitting in the sweet spot I have effectively one sub and only one sub. I don't like it when you refer to it as two.

Me too. The S&V article's findings were based exclusively on listening tests, and as I said above, any conclusions came with lots of caveats.

With respect to your own set-up and the comment directed at Matt above, is that something unique to it, or is it potentially more broadly applicable to "in the sweet spot" listening for other multiple sub set-ups (not to say yours is - unless you want me to say so)? Is it a characteristic of your IB set-up (and how and why)? Do you have a single IB sub - with two ports/vents into your room? Or two IB subs operating in tandem such that they behave like one? I'm only asking because I honestly don't understand. (Please don't smite me like you would Matt; he's imminently smitable - unlike me.)

Jeff
 

TitaniumTroy

Well-Known Member
I believe Flint has mentioned this before, but one problem for the average home theatre buff. How do you calibrate, 4 subs in different locations? Plus that might give your Audyessy room correction software a fit.

But then again MattB says the more Subs the Merrier!
 
D

Deleted member 133

Guest
TitaniumTroy said:
I believe Flint has mentioned this before, but one problem for the average home theatre buff. How do you calibrate, 4 subs in different locations? Plus that might give your Audyessy room correction software a fit.

But then again MattB says the more Subs the Merrier!

Good question.

I'm happy to share how I went about it - but because my set-up is atypical (which I suppose most multiple sub set-ups are) you should probably first read up on my system description in that other section of the Annex.

First off placement was a combination of calculation, trial and error, and convenience. The front two Velos were placed symmetrically on the front wall at distances that broke the span of the front wall into segments of distances that corresponded to prime numbers. The theory being that you would not have as great a chance setting up standing waves / reflections. (Plus as I've mentionned before, the room is not sealed and the whole backend allows sound, especially bass, to escape to the rest of the house - which acts like a big bass trap.) The other two subs are stacked in a rear corner (that's the "convenient" location.) (The fifth sub's in another corner, put as my other thread mentions, its erves a completely different purpose than these four.)

Actually the two Velos and the B&W are wired to behave like a single sub. What I did was to calibrate each one's level alone to match the rest of the system. Then with them all on together (treating them as one) they were again calibrated to the other speakers (which involves dialing back the signal that's sent to them.) A further step (and this is iterative) is to use a Velo ICBM-1's display function to, in real time, adjust / fine tune the Velo's crossover frequency, and all three levels, to yield the smoothest response - which in my case turned out to give essentially a flat line from 15-100 HZ. (From published reviews / measurements I had learned that, with the Velos, changing the crossover frequency has more of an effect that just changing that frequency. The whole curve changes somewhat - and selecting the highest frequency for example does not yield the deepest potential bass response. The ICBM-1 shows how much.) I'd had the three dialed in pretty well by ear but the ICBM-1 really helped with the last step. So those three run in unison - handling all bass-managed frequencies below 40Hz from the mains.

The PB-13 which handles LFE only was then a simple calibration against the rest of the system (mains and three subs - which are now treated as if they were single speakers). I obtained "correction" information for the RS analogue meter which ended up causing me to bump up the signal to it by a few dB.

If someone were to walk into the room and chnage every setting randomly, and assuming I did had not written values etc. down, I could probably set the whole thing back up again in less than an hour. Given the number of combinations and permutations possible it would almost certainly not be exactly the same. But darn close.

I would imagine that doing the calibration for four identical subs in the set-up that the S&V article used would be a piece of cake in comparison. Assume that all you have is level control for each. (If more control than that just set them all to the same - whatever that might be - and by "same" I mean whatever worked best for a single sub.) Once location is picked calibrate the level of each one individually against the mains. Then run them all together again as "one" and calibrate against the mains.

As for the use of Audyssey, maybe that's why I found I did not like what it did and why I don't use it. My guess is that the multiple subs do give it problems. Although it's really not in the bass range that I find fault. But that's a whole different topic.

Jeff
 

milpool

Active Member
Jeff, how did you address phase for each sub? Should I assume that each one has it's own phase control? I imagine that it could be a nightmare to time align subs located all over the room, from some global control (like a pre/pro). I would think that alone would render Audyessy (or any algorithm) useless, since the mic cannot detect which sub is out of phase when all subs are running. (Not that I'd ever recommend using an algorithm, when pain-staking measurements are far more fun!)

Then the follow up question would be to ask, if phase is calibrated individually, is there an impact on the overall phase relationship when the full system is running? I guess I'm referring to phase cancellation, as a byproduct of multiple subs. Thanks.
 
D

Deleted member 133

Guest
milpool said:
Jeff, how did you address phase for each sub? Should I assume that each one has it's own phase control? I imagine that it could be a nightmare to time align subs located all over the room, from some global control (like a pre/pro). I would think that alone would render Audyessy (or any algorithm) useless, since the mic cannot detect which sub is out of phase when all subs are running. (Not that I'd ever recommend using an algorithm, when pain-staking measurements are far more fun!)

Then the follow up question would be to ask, if phase is calibrated individually, is there an impact on the overall phase relationship when the full system is running? I guess I'm referring to phase cancellation, as a byproduct of multiple subs. Thanks.

Phase is set to zero for every sub - where a control is available. It turns out that they are all equidistant from my listening position.

For the Velos/B&W combination, the first time I set them up I spent some time listening with one, two, and three subs running - to see if I could hear any adverse effects. None were heard. I can walk around the room and hear / feel how evenly the bass is distributed when all are running. It's very smooth with no significant spikes or dips. The sweet spot still is: but it's now grown to be just about anywhere in the room that you would ever want to sit.

One thing that I should add, and as I mentionned in the other thread about my system, having the SVS PB13 Ultra dedicated to the LFE signal alone is a real plus. It gets to do the heaviest grunt work and easily handles the ultra-lows thrown at it. My guess is that it would always be better, for the LFE, to stick with a single very capable sub, rather than multiple less capable subs. But for bass-managed signals (again in my case sub-40Hz) I'm sold on the benefits of multiple subs. And of course having mains (10 speakers in total) that are flat to below 30Hz handling bass from 40Hz on up makes for, in combination with the subs, a very impressive and capable system overall. For the most part each segment is simply loafing along at all but the highest listening levels.

It's not an approach for everyone. It's probably not even for many. I like it (and am able to pull it off) - and that's what matters the most. And there's a standing offer to anyone who's ever in the Ottawa area to drop by for a listen.
 

MatthewB

Grandmaster Pimp Daddy
Famous
Please Don't smote me Flint. :teasing-tease: I saw two drivers Flint hence two different subs (how I look at it) as for my many subs, I use only one in my main system, the others are used as Mid Bass subs, and each one is easily controlled since they run independant of each other hooked up to just one channel each. So they never cross over to the main sub at all. Each channel with a Mid bass sub is only handling 40-80hz while anything below 40hz goes to the sub. I find the more audible bass is handled by the mid bass subs, while the bass you can really feel is handled by the SVS. the few members I did have over seemed to "get the rift" of what I was doing. Flints teasing me not withstanding.
 

soundhound

Well-Known Member
Flint said:
I love to see a spectral analysis of the thd+noise from the output of four subs placed for smoothest response next to the same measurement of a single sub costing same as the four subs placed most ideally in the same room. Considering the potential for four unique arrival times with four subs (the primary cause of the flat response), the noise and harmonic distortion is very likely to be much higher. Heck, add a phase measurement too.

Then why not do it and post the results in this thread?
 
Top