Two Subwoofers

[markstein]

FWIW, I am adding a second sub. I have done experimenting with REW Room Sim, and got the following. I have no acoustic treatment in my room.

First, no subs:
View attachment 457634

One sub:
View attachment 457636

Two subs both at side of main speakers:
View attachment 457638

Finally, and the option I am going to start with, two subs diagonally opposite:
View attachment 457639

Interestingly, two subs with each at the side of the main speaker appears to add nothing compared to a single sub. Diagonally opposite seems to work best, in theory at least.

I'm going to get two MJ Acoustics subs (from here in the UK), mainly because they have a very good app that helps with phase and gain setting.

You may want to try "optimal" placements as identified by Todd Welti as well (middle of front wall & middle od back wall / middle of left wall & middle of right wall). Imperfections like windows and doors may require other optimum placement and limit the usefulness of simple room mode simulation.

 

[WeekendWarrior]

You may want to try "optimal" placements as identified by Todd Welti as well (middle of front wall & middle od back wall / middle of left wall & middle of right wall). Imperfections like windows and doors may require other optimum placement and limit the usefulness of simple room mode simulation.

Thanks for the suggestions, however the room is multi purpose so I don't have lots of options, although small adjustment will be possible

 

[markstein]

I have such limitations with possible sub placements as well. A diagonal setup (front left corner, back right corner) along with heavy EQ is a good compromise in my room. in any case - I recommend you learn to use MSO to improve bass linearity to more than one single listening spot. Good luck!

 

[Oddball]

I said the "reports" were fishy: it seems like a lot of people like to play with both implementations, but from what I can see it becomes a rabbit hole unto itself. This is a telltale sign of either immature technology or techniques with limited applicability, or both. If I squint, the DBA concept looks like a strange variation on cardioid approaches used to keep stage volume low in larger PA applications.

Having 8 or more subs in a living room environment seems to violate my favorite engineering maxim: "A design isn't perfected when you can't add anything else; it's perfected when you can't take anything away." That money, time, and effort would almost certainly be better spent on room treatment & configuration.

I am also skeptical of Trinnov specifically when I see things like this on their website:


I'd like to see the data to back up any of the many claims in that short passage. The explanation of the propagation of sound in an enclosed space is ... odd.

Back to the original topic, dropping a couple of conventional subs here and there in a living room or home theater seems as likely to add problems as to reduce them. It's bound to complicate analysis, too, probably beyond the means of most hi-fi enthusiasts' skills.

It would be interesting to learn more about your setup and how you managed to solve these issues that are apparently not easily (or at all) solvable?

I must admit that my skills are limited compared to some of the members you were conversing with, and probably yours, but I still, somehow, and barely, managed to find my way around the jungle. Even managed to implement a few twists along the journey.

 

[Greenway54]

All very interesting, but the essence of my original question is what stereo subwoofers might add to my experience of the music, in a single well-defined and narrow seating position (my office desk), compared to my single-sub set-up that I have now.

 

[markstein]

You have not mentioned a stereo sub setup in your initial post....

 

[NTK]

All very interesting, but the essence of my original question is what stereo subwoofers might add to my experience of the music, in a single well-defined and narrow seating position (my office desk), compared to my single-sub set-up that I have now.

This is a rather controversial subject. There is a good bit of discussions in these 2 threads by expert proponents of both sides (mono vs stereo bass). My links are to the middle of the conversations, so you may want to check out the full threads.

Bass and subwoofers

I have been reading this thread with my limited knowledge of the science behind the acoustics, particularly after my recent comparison of a live afternoon orchestral performance in the wonderful acoustics of the Amsterdam Concertgebouw, and the TV broadcast of the exact same concert the very...

www.audiosciencereview.com

A Broad Discussion of Speakers with Major Audio Luminaries

Well, in fact, while you can't 'image' below 90Hz, you can get intense changes in envelopment. This absolutely requires more than one sub. That's way, way below any transition frequency, and you can't claim "bass quality" until you make that listening room sound as "wide" as the church you...

www.audiosciencereview.com

 

[J.M. Noble]

Sounds to me like you're not familiar with Dr. Geddes' work. Seems like you should familiarize yourself with it before you denigrate it.

His PhD research on the subject was completed in 1980. We have learned so much in the meantime, both through better measurement tools that can consider time domain effects and in more recent psychoacoustic research. It doesn't appear that these advances are taken into account in more recent presentations.

I've looked over some of his work and have found a few assertions questionable and/or factually difficult to defend. I don't feel like writing a dissertation of my own, but it's easy enough to do a little sanity check arithmetic.

I'm starting to detect some dogmatic backlash here, so I'll bow out at this point. We're kind of offtopic anyway.

 

[Greenway54]

You have not mentioned a stereo sub setup in your initial post....

Sorry, I assumed that setting up two units meant that they would be used as stereo subs. Of course, they could be mono too, but I was going with the (rather simplistic) notion that one = mono and two = stereo. In my case they would be connected to the LEFT and RIGHT outs from the preamp, with the satellites connected to the other LEFT and RIGHT outs from the same preamp.

 

[markstein]

Thanks for clarifying.

When I hear of multiple subs, I automatically think of a bass managed mono setup with equalization. I propose to google "Todd Welti multi sub" which should lead you to papers explaining the background in detail.

As pointed out by NTK there are also discussions whether a stereo bass is advantageous over multiple mono subs. I personally see more advantages in multiple mono subs, YMMV.

 

[jhaider]

Mo' subs, mo' problems. I'd go with a single sub whenever possible.

Time alignment complexity, room mode interactions, reinforcement/cancellation causing power alleys like we have in sound reinforcement & PA applications, and a bunch of other issues can be avoided by having just one sub (assuming the subs aren't identical and grouped together to effectively create one larger sub through coupling).

You can’t translate experience from large room acoustics to small rooms.

 

[Mort]

REW room sim and my empirical testing suggests that unless I can get a second sub diagonally in my small 3.2 square meters room, it's not worth getting a second sub. Even then it was marginal. I can't keep a second sub diagonally in this space permanently anyway.

 

[J.M. Noble]

You can’t translate experience from large room acoustics to small rooms.

Some of the joints I work in are like the pictures posted upthread, size-wise.

After forty plus years working in and around audio in various capacities, I have a lot of experience to translate.

 

[Mort]

I have a lot of experience to translate.

Oh phew. I was worried an Internet stranger might be overestimating their experience.

Seriously, you can't expect to just throw that down anonymously in your first few dozen posts.

 

[J.M. Noble]

Oh phew. I was worried an Internet stranger might be overestimating their experience.

Seriously, you can't expect to just throw that down anonymously in your first few dozen posts.

I have hundreds of posts under my own name. Please try to remain factual in your personal attacks.

 

[jhaider]

Some of the joints I work in are like the pictures posted upthread, size-wise.

After forty plus years working in and around audio in various capacities, I have a lot of experience to translate.

One dangerous thing about experience is not knowing when the underlying conditions are such that it does not apply.

Small rooms (bass wavelengths larger than room dimensions) are fundamentally different animals from large rooms. Lots of bad advice has been given based on the assumption that the same rules apply in the bass.

 

[J.M. Noble]

One dangerous thing about experience is not knowing when the underlying conditions are such that it does not apply.

Small rooms (bass wavelengths larger than room dimensions) are fundamentally different animals from large rooms. Lots of bad advice has been given based on the assumption that the same rules apply in the bass.

I said I would desist, but that requires some cooperation.

I have pointed out the issues. The rest, as they used to say when we actually learned things (i.e. when I was an engineering major long ago), is left as an exercise for the reader.

I am reminded once again that consumer audio is the place of hopes and dreams. I'll stick to professional circles in the future--the kind of black magic going on there would blow your mind and actually solves real problems.

 

[TimVG]

Here's what 4 subs can do in a smallish space before and after MSO optimalisation measured over 5 seats. MSO is free, so it's really not that complex if you have a measurement microphone and are willing to follow a pretty standard procedure.

 

[Digital_Thor]

Yup... I helped to dial in 2-4 subwoofers in all kinds of homes for the last 10 years or so - in all kinds of systems and configurations.
I like to try and understand the right terms and theories behind it, but people like Earl Geddes very often clearly states in his presentations, that he is talking about small rooms - specifically - very specifically.
In any shaped or oddly designed room, I've been able to manually use 2-4 subwoofers to smooth out the response overall, to a degree I've never heard in a normal setup with 2 speakers.
It has to be said though, mains should preferably play below 100Hz and overlap to sum well with subwoofers - and I've had success with both mono and stereo subwoofers - meaning coupling the subwoofers together as one, but also coupling the subwoofers on the right side, with the right main speakers.... under 100Hz it's mainly mono anyway in the majority of recordings.
When it comes to live sound and huge venues - it's a whole different beast. Very few things that work in bass at a football field, works well in a 50sqm living room - or the other way around.
For example, beam-forming bass with stacked subwoofers, 2 pointing forward and 1 pointing backwards - great for venues - not something you would do in a home.
The right technique for the right job and situation - and wallet for that matter.