Two Subwoofers

[Greenway54]

So, I run 2 subs with my genelecs in my office, but they're in the corners and not right under the mains.

I will say that the D108 is not a super great value unless the size constraint is insurmountable. @sweetchaos has put together a pretty comprehensive list of subs and their tested performance here: https://docs.google.com/spreadsheet...6ZL6anVTW2_M/edit?gid=834598950#gid=834598950 - I think you can't really get small, cheap, and high output, but the SVS 3000 Micro is worth a look as an alternative, as they give a deal on a pair of subs, it's slightly smaller than the JL unit, and the output is similar.

I have 2x BIC F12s, I got them used for $250 total, and one of them beats the D108 @ $1K USD. So if you can lose the size constraint somehow, there are deals to be had.

Aside from that, I definitely recommend running EQAPO on your PC, you can EQ the bass to perfection, it's really the best upgrade you can make for small dollars. (EQAPO is free but you'll need a mic.)

Not sure about the 'not a super great value' reference...I paid $1260 + taxes CDN for my JL Audio D108, and the SVS 3000 micro lists at $1500 + taxes, but maybe you were suggesting the D108 is not a great value in terms of relative specs/performance. Anyway, I get the point that there might be a deal on two. That being said, I already have one D108, so any move to two subs would mean a return to the local store that sold me the first one (where I originally went to buy an SVS 3000 Micro but I favored the D108 instead after checking out their stock).

 

[kemmler3D]

Not sure about the 'not a super great value' reference...I paid $1260 + taxes CDN for my JL Audio D108, and the SVS 3000 micro lists at $1500 + taxes, but maybe you were suggesting the D108 is not a great value in terms of relative specs/performance. Anyway, I get the point that there might be a deal on two. That being said, I already have one D108, so any move to two subs would mean a return to the local store that sold me the first one (where I originally went to buy an SVS 3000 Micro but I favored the D108 instead after checking out their stock).

Right, just more generally observing that the bang for buck is not amazing with these small boxes compared to a larger one. The SVS and JL are not far apart in terms of performance and I think the pricing is less favourable for SVS in Canada, but both are pretty much par for the course in the mini DOS sub space.

You get the sub you have space for... My office has those bulky ones I got cheap, but in the living room I ended up with KC62s to maintain marital integrity, even though they are one of the more expensive subs in terms of output.

 

[Miniyouuuu]

even when sub-bass has no directionality, the more subs you implement in your space the better bass covering you get in that area. I have 2 subs behind may sofa, one each side. The amount of bass required at 60dB at the listening position is different when playing at 80dB. If you play the bass closer to the listening position, you create a fake loudness. At 80dB my speakers are able to fill the volume but at 60dB the bass is leaner. Additionally having a specific speaker for that lower frequency range allows you to the sub 30hz.
Obviously setup is difficult. You are required to set delays, volumes, crossovers, phases for each speaker in order to perfectly align each speaker. In order to achieve it MiniDSP Flex, Umik1 and REW or Dirac bass control will be your best friends.

 

[J.M. Noble]

This goes against both common theory and experience unless I'm severely misunderstanding what you're saying. Typically adding more subs will give you a more even frequency response over a wider area of the room.

Common theory and experience in the home audio world is rather like folk tales. Track down some design tools like those used in professional sound reinforcement applications and you'll see the problems come up as the room size increases. I'll be dealing with this very issue tonight while working as a sound engineer at a venue where I don't have any choice but to space the subs out.

 

[sigbergaudio]

Common theory and experience in the home audio world is rather like folk tales. Track down some design tools like those used in professional sound reinforcement applications and you'll see the problems come up as the room size increases. I'll be dealing with this very issue tonight while working as a sound engineer at a venue where I don't have any choice but to space the subs out.

Since I design and manufacture subwoofers, I have a bit of first hand experience, and it doesn't match what you're saying. Is there perhaps a difference in how this works in domestic sized rooms and professional environments?

 

[J.M. Noble]

Since I design and manufacture subwoofers, I have a bit of first hand experience, and it doesn't match what you're saying. Is there perhaps a difference in how this works in domestic sized rooms and professional environments?

I owned LEAP and LMS from the days when the company behind them was LinearX (early 90s, before the company split) and I did a lot of subwoofer design & testing with them. Before that, in the late 80s, I wrote and used a CAD program that was based on Neville Thiele and Richard Small's original AES papers. I also worked with early DSP systems for bass management starting in the same era. I have a bit of firsthand experience too.

You have to consider time domain effects, which start to matter more for low frequencies as the differential in distance from the subs increases beyond a couple of feet. You can optimize for a single listening position with time alignment, sure--which can be appropriate for a domestic hi-fi rig with one dedicated listener--but it falls apart badly for those outside the sweet spot. Toss in some psychoacoustics (Precedence/Haas Effect etc.) and it quickly becomes apparent that adding more subs in various places just increases complexity without providing anything but accidental benefits.

The only differences between a large living room and a small club, for subwoofer purposes, are size (obviously) and SPL. An additional consideration is that anything under 35-40Hz or so is also not usually important at a club/bar except at hip hop or electronic music shows. You might benefit from reading up on the state of the art in bass management in sound reinforcement, and the sorts of problems they are attempting to solve. The engineering is remarkable.

 

[sigbergaudio]

I owned LEAP and LMS from the days when the company behind them was LinearX (early 90s, before the company split) and I did a lot of subwoofer design & testing with them. Before that, in the late 80s, I wrote and used a CAD program that was based on Neville Thiele and Richard Small's original AES papers. I also worked with early DSP systems for bass management starting in the same era. I have a bit of firsthand experience too.

You have to consider time domain effects, which start to matter more for low frequencies as the differential in distance from the subs increases beyond a couple of feet. You can optimize for a single listening position with time alignment, sure--which can be appropriate for a domestic hi-fi rig with one dedicated listener--but it falls apart badly for those outside the sweet spot. Toss in some psychoacoustics (Precedence/Haas Effect etc.) and it quickly becomes apparent that adding more subs in various places just increases complexity without providing anything but accidental benefits.

The only differences between a large living room and a small club, for subwoofer purposes, are size (obviously) and SPL. An additional consideration is that anything under 35-40Hz or so is also not usually important at a club/bar except at hip hop or electronic music shows. You might benefit from reading up on the state of the art in bass management in sound reinforcement, and the sorts of problems they are attempting to solve. The engineering is remarkable.

I am sure you are very knowledgable, it was not my intent to imply that I knew more than you, only that I knew more than what I had heard from "folk tales". My experience is that when you get to four subwoofers placed appropriately, you get very even bass even in a wider area. And the typical placement for best performance isn't stacking all four in one place. But I am open to the possibility that I have been missing something here.

I am relatively up to date on state of the art in bass management in the consumer field, namely things like Trinnov Waveforming for instance. They do not put all the subs in one place. If you have some links and references to state of the art of bass management in your area of expertise, I would be very interested to read up on it.

 

[J.M. Noble]

I am sure you are very knowledgable, it was not my intent to imply that I knew more than you, only that I knew more than what I had heard from "folk tales". My experience is that when you get to four subwoofers placed appropriately, you get very even bass even in a wider area. And the typical placement for best performance isn't stacking all four in one place. But I am open to the possibility that I have been missing something here.

I am relatively up to date on state of the art in bass management in the consumer field, namely things like Trinnov Waveforming for instance. They do not put all the subs in one place. If you have some links and references to state of the art of bass management in your area of expertise, I would be very interested to read up on it.

I'm not sure turning the whole room into a speaker enclosure is under discussion here, and the reports on Trinnov & Dirac's equivalent seem fishy to me. I'll agree that pressurizing the whole room will overpower mode issues, but I more or less said that already.

 

[Keith_W]

I'm not sure turning the whole room into a speaker enclosure is under discussion here, and the reports on Trinnov & Dirac's equivalent seem fishy to me. I'll agree that pressurizing the whole room will overpower mode issues, but I more or less said that already.

Love the respectful and educational exchange. Thank you for your insights. I think it is fair to say that few of us on ASR have experience with larger venues.

I am sceptical of Dirac's ART as well. I think its chance of success would be better if they specified where speakers should be placed, but they don't. At least Trinnov says that the subs should be placed in a DBA configuration, so in my mind there is no reason it shouldn't work in a large venue. Would you be able to explain why you think Trinnov and Dirac's implementation seem fishy to you?

 

[J.M. Noble]

Love the respectful and educational exchange. Thank you for your insights. I think it is fair to say that few of us on ASR have experience with larger venues.

I am sceptical of Dirac's ART as well. I think its chance of success would be better if they specified where speakers should be placed, but they don't. At least Trinnov says that the subs should be placed in a DBA configuration, so in my mind there is no reason it shouldn't work in a large venue. Would you be able to explain why you think Trinnov and Dirac's implementation seem fishy to you?

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:

Too often, the walls are not reflective enough to generate a good planar wave. Also, the wave that reaches the rear wall has changed while traveling the length of the room because the walls are insufficiently stiff or parallel to guide the wave properly… Lastly, the nature of the wave changes as it encounters furniture, risers, tiered seating, etc. As a result, the wave that reaches the rear wall is not the same as the one that left the front wall, and cannot be effectively canceled.

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.

 

[kyuu]

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.

So you disagree with the research done by Earl Geddes?

 

[markstein]

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).

I'd rather use no sub at all than just one sub.

One subs limits you to one listening position only if you prefer even bass, requiring measurement and DSP.

The only way to extend the listening area are multiple subs and a proper DSP solution. Use MSO for optimization. it is worth the effort!

 

[sigbergaudio]

I'm not sure turning the whole room into a speaker enclosure is under discussion here, and the reports on Trinnov & Dirac's equivalent seem fishy to me. I'll agree that pressurizing the whole room will overpower mode issues, but I more or less said that already.

We have a real life case study (in a relatively small and less than perfect room) here:

Perfect bass with Sigberg Audio Inkognito subwoofers and Trinnov WaveForming™

Introduction Bass in domestic rooms Trinnov’s WaveForming technology demands high-end subwoofers that are accurate both with regards to linearity and the time domain. In this case study, we demonstrate how Sigberg Audio’s Inkognito subwoofers — known for their high end performance, low group...

www.sigbergaudio.com

Seat to seat consistency in his relatively large 3-seater sofa was +/-0.8dB. This is with 8 subs.

Some screenshots (also available in the article):

 

[sigbergaudio]

@J.M. Noble

Here are four subs in a relatively large and complicated space. I have not been there myself but the customer reports good bass overall, also when moving around. Two subs are in the front corners, and two are up on an open loft space in the back (see pics). Not certain this is the very last measurements, but at least one measurement. This is four subs + manually applied EQ that I helped with remotely.


(No smoothing)

 

[J.M. Noble]

The first example is what I meant when I said "I'll agree that pressurizing the whole room will overpower mode issues, but I more or less said that already." That tiny room needs a barometer to measure SPL.

The second example has a 5-8dB suckout from the high 30s up to 50Hz. I can achieve this in more straightforward ways.

Nice room, though, and probably quite friendly to bass with all those oddball angles. My former 22' X 24' listening room/home theater loft, which had slanted walls and other nice features like an acoustic drop ceiling, was similarly amenable to boom. A single fairly modest 12" sub was enough to rock any seat in the house as loud as I ever wanted to drive it--and my baseline is 10kW+ PA rigs capable of producing 115dB+ continuous in much larger rooms.

 

[J.M. Noble]

So you disagree with the research done by Earl Geddes?

The word "research" seems to dignify these notions a little more than necessary.

Spamming a bunch of subs around and running them up to 150Hz while not high-passing the mains seems ... idiosyncratic. If the idea is to make a fondue pot of bass and (once again) overpower the room to get frequency domain results that look nice while letting the chips fall where they may in the time domain, then sure.

I won't knock people who enjoy their systems, but from an engineering perspective I don't see anything that recommends itself to me. I also confess to a stereo music bias vs. home theater, so ymmv.

 

[sigbergaudio]

The first example is what I meant when I said "I'll agree that pressurizing the whole room will overpower mode issues, but I more or less said that already." That tiny room needs a barometer to measure SPL.

That's a pretty normal sized room in Europe. The listening area is also part of a larger open space.

The second example has a 5-8dB suckout from the high 30s up to 50Hz. I can achieve this in more straightforward ways.

Nice room, though, and probably quite friendly to bass with all those oddball angles. My former 22' X 24' listening room/home theater loft, which had slanted walls and other nice features like an acoustic drop ceiling, was similarly amenable to boom. A single fairly modest 12" sub was enough to rock any seat in the house as loud as I ever wanted to drive it--and my baseline is 10kW+ PA rigs capable of producing 115dB+ continuous in much larger rooms.

Your ideas and/or approach seem to be contrary to what I'd say is common knowledge within the consumer audio world, so if you have epiphanies that can revolutionize that, it would be interesting to hear the details.

 

[WeekendWarrior]

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:

One sub:

Two subs both at side of main speakers:

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

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.

 

[kyuu]

The word "research" seems to dignify these notions a little more than necessary.

Spamming a bunch of subs around and running them up to 150Hz while not high-passing the mains seems ... idiosyncratic. If the idea is to make a fondue pot of bass and (once again) overpower the room to get frequency domain results that look nice while letting the chips fall where they may in the time domain, then sure.

I won't knock people who enjoy their systems, but from an engineering perspective I don't see anything that recommends itself to me. I also confess to a stereo music bias vs. home theater, so ymmv.

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

 

[NTK]

Apparently Dr. Geddes got his doctor's degree by studying "Low Frequency Sound Field in Small Rooms".