Single 12" vs dual 10" subwoofers

[Wayne A. Pflughaupt]

This:

One big, properly placed sub, with proper room treatment is better than multiple small subs. But if you can't place your sub where it needs to be and you can't manage room modes then multiple subs will help while probably being more expensive.

No one ever seems to mention that Harmon’s experiments and theories on multiple subs were derived in shoebox rooms. It’s good and fine if you happen to have your set-up in a room like that, but it’s not of much use for the rest of us.

I personally have never felt the need for anything but a single sub, located in a good corner, and properly equalized (the Tom Nousaine method).

Regards,
Wayne A. Pflughaupt

 

[Kal Rubinson]

No one ever seems to mention that Harmon’s experiments and theories on multiple subs were derived in shoebox rooms. It’s good and fine if you happen to have your set-up in a room like that, but it’s not of much use for the rest of us.

In addition, their goal was the even distribution of bass across a variable number of listener seats as would be employed in a theoretical home theater. For me (and, I think, some others), the goal is smooth FR and non-modal behavior in 1-2 seats on a couch.

 

[NTK]

...
No one ever seems to mention that Harmon’s experiments and theories on multiple subs were derived in shoebox rooms. It’s good and fine if you happen to have your set-up in a room like that, but it’s not of much use for the rest of us. ...

I think you are mistaken. For non-rectangular rooms, the process gets much more complicated. Here is a link to an article by Dr Toole in Audioholics on sound field management.
https://www.audioholics.com/room-ac...i-sub-sfm/the-birth-of-sound-field-management
Here are the first several sentences.

By Dr. Floyd Toole — March 21, 2016 ​

​

But simple rectangular rooms are not everywhere. We needed more flexibility, and besides, my new listening room was not a simple rectangle, and again I was not enthusiastic about filling it with bass traps. This was another case of (personal) necessity mothering an invention. My talented employees Todd Welti and Allan Devantier went to work, and came up with something we call Sound Field Management (SFM). (Welti and Devantier, J. Audio Eng. Soc., vol. 54, 2006). This is much more complicated, involving transfer-function measurements from each subwoofer location to each specified seating location. An optimization algorithm then chews away at the data and comes up with specifications for the signal processing necessary for the signals being delivered to each of the (usually) four subs. Amplitude, delay and one parametric filter will be specified. The goal is to minimize the bass variations among the specified seats so that equalization, if it is necessary, will be equally effective for all listeners. It works superbly. ...​

 

[detlev24]

[...] No one ever seems to mention that Harmon’s experiments and theories on multiple subs were derived in shoebox rooms. It’s good and fine if you happen to have your set-up in a room like that, but it’s not of much use for the rest of us. [...]

This is not completely true, as Harman's research gives a good idea of what is possible in most rooms. They have covered limitations of multiple subwoofer integration, as well.

For instance, I have a ~80 m² cross-gable roof shaped room - far off from Harman's "shoebox rooms". The room is not (yet) treated with bass-traps and unfortunately, I only have 2 fixed subwoofer positions available: right and left of and in-between the main loudspeakers. Those are really suboptimal conditions!

However, using 2 subwoofers instead of one gives me much more flexibility on the application of EQ [besides this, a higher combined SPL at lower THD]. More precisely, Multi-Sub Optimizer (MSO) calculated two filters, one for each subwoofer and additionally a (+)delay block for one, and a (-)gain block for the other subwoofer. Something that clearly cannot be achieved with a single subwoofer. The result is pretty astonishing: With 2 subwoofers which, by the disadvantage of fixed positions in quite close proximity to each other, do excite very similar room modes; MSO was able to smoothen the frequency response significantly over 5 listening positions = an entire couch! The frequency range of my interest was from 15 Hz to 120 Hz for the room corrections, following a slightly modified Harman target response curve. Other calculations showed, that I could smoothen the frequency response down to 10 Hz but this would rise distortion levels; and I prefer less THD in addition to concentrating on the audible range [which would start at ~16 Hz for "younger" people with an undamaged sense of hearing]. Visceral impact is more than enough for my taste; so even in movies, I do not miss the additional -5 Hz; to reach 10 Hz "flat".

Without any doubt, the results - even with a single subwoofer - will be of another level, once proper acoustic room treatment has been put in place!

====
On the following MSO graphs, no smoothing has been applied. The last two graphs, REW distortion measurement, have a fixed 1/24 octave smoothing applied:

..

[ EDIT ]
I added a distortion measurement, which was taken after the calculated MSO tunings had been applied to both the 'dual-opposed 15-inch drivers, sealed' subwoofers. The highest distortion [< 0.7%] shows, where the big 40 Hz room mode had to be corrected for. [Dirac Live room correction will be applied on top of that; for the whole multi-channel setup.]

• miniDSP UMIK-1 (factory calibrated: 10 Hz - 20 kHz)
• ~10 feet [~3 meters] listening distance, at the MLP
• REW; single sweep @ 90 dB SPL / theoretical equivalent of 99.54 dB SPL @ 3.28 feet [= 1 meter]

Enjoy!

 

[FrantzM]

So I am at the point where I can actually start adding a sub or subs to my setup. My room is about 38m2 with a 16m^2 listening area. Currently I have my speakers all the way at one end of the room up against the long wall, but I might be putting them on the short wall instead. Listening distance would be about the same, but I wouldn't have a wall behind my head in that case. Not sure if I can make it all fit (that short wall is slightly sloped, so its a bit of a struggle), but a quick measurement on the short wall showed that the massive 50hz peak was less extreme than on the long wall. The nulls were also less in that setup. I will have to confirm that with a more thorough measurement, because for this one I just moved one speaker a bit forward and turned it 90 degrees.

So my real question is how would one €1000 12" do versus two €500 10" subs? I don't need massive SPL output, but I want it to go low and tight and I have the capability to go for an opposite corner setup with dual subs. My gut says 12", but my brain says to just get 2 cheaper 10" subs. I will be pairing them with Revel M106's and I will probably plug the port on those so more of the low end will have to be played by the subs (does that make sense?).

Attached is a single measurement of one of my speakers (plugged port) at its current long wall position. The other channel shows similar peaks and nulls. Under 300hz I'm lacking so much output. How do I save this

Hi

Let me ask you a few questions before answering:
Are you a patient person or at least, are you willing to try to be?
Are you willing to devote some time to get the best out of your system
Will your neighbors or better half tolerate the rumble, tweets, screeches of test tones?
Can you devote 4 weeks at least of work, to this project of getting the best out of your system?

If the answer to all those questions is "Yes" then:
Dowload REW (free)
Acquire a miniDSP 2 x 4 ($100)
A miniDSP UMIK-1 ($100)
A pair or trio of 8 or 10 " sealed (if possible) subwoofers for the remaining €800 or so. They don't need to be the last word in subwoofer performance. Say they can reach anechoic 35 Hz.
Then it begins. You will have to read, research, learn how bass works in rooms, how to measure, how to interpret those measures.

A few things that are facts and provable.
Best Bass is obtained with EQ.
Under 80 Hz you cannot perceive location.
You can definitely place one subwoofer in a corner, it may actually help...
In the bass symmetry is not required, you could have one subwoofer in the back of the listening position and another in the front corner.

Ask, some people here are immensely knowledgeable.

Repeating: It will take time. 2 smaller subs are better than one... 3 is even better, past 4 the returns may be too small to matter; two is the minimum. Depending on your room, you may even reach lower Hz lower with the 2, lesser subs ... You may find yourself getting usable response under 20 Hz...

Peace

 

[Wayne A. Pflughaupt]

I think you are mistaken. For non-rectangular rooms, the process gets much more complicated. Here is a link to an article by Dr Toole in Audioholics on sound field management.
https://www.audioholics.com/room-ac...i-sub-sfm/the-birth-of-sound-field-management

Not sure how that relates to what I said? I was speaking of a single sub. Mr. Toole is using multiple subs. Obviously in that situation a fix is needed, especially if some are close to seating locations.

Small shoebox rooms (such as are commonly found in residential settings) are abysmal. They have a “bass hole” in the dead center of the room, and perceived bass levels increase from that point as you move towards any wall. So for the people stuck with rooms like that, it’s good that the folks at Harmon have come up with some help for them.

I’ve never seen that problem in rooms that have openings to other rooms. I think I recall Ethan Winer once stating that such openings function as bass traps, I assume because they prevent the build-up of energy you have with closed shoebox rooms.

Regards,
Wayne A. Pflughaupt

 

[Wayne A. Pflughaupt]

I personally don’t get the whole “even distribution of bass” thing, outside of shoebox rooms where it definitely is a big problem that needs to be addressed.

If people fortunate enough to have irregular rooms invite friends over for group music listening, that’s one thing. But for solo music listening, I don’t see any reason not to just optimize for the MLP. Movie bass is all about “boom.” There’s no reason to fine-tune the whole room for “boom.” Who’s going to observe and complain, “Hey, the explosions sound better in your seat than mine!” Again, shoebox rooms notwithstanding.

People overlook the fact that frequency response plots generated by programs like REW merely map the fundamentals. That’s only one part of the “bass picture.” Bass notes from instruments like pianos, synths, cellos, tubas, baritone saxophones, electric and acoustic basses, etc. are extremely complex tones comprised of not just the fundamental, but also harmonics, sub-harmonics, overtones, etc.

Thus, if someone happens to have a null at 80 Hz, it doesn’t mean that playing a song where the bass instrument hits that note, that it is simply going to disappear. (It’s one octave up from the open E of a 4-string bass, to cite one instrument). In fact, a problem may not even be noticed, as the overall complexities of the tone will largely fill in the gap and, mask the missing fundamental.

That’s why with music program you probably aren’t going to hear a big difference in the bass line from one seat on the sofa to the next. Again, shoebox rooms notwithstanding. But if you do hear a difference, then by all means do whatever it takes to fix it.

All that said, I will happily concede the possibility that I’ve always been lucky and had easy rooms.

Regards,
Wayne A. Pflughaupt

 

[Wayne A. Pflughaupt]

This is not completely true, as Harman's research gives a good idea of what is possible in most rooms. They have covered limitations of multiple subwoofer integration, as well.

For instance, I have a ~80 m² cross-gable roof shaped room - far off from Harman's "shoebox rooms". The room is not (yet) treated with bass-traps and unfortunately, I only have 2 fixed subwoofer positions available: right and left of and in-between the main loudspeakers. Those are really suboptimal conditions!

Excellent post, thanks for that! It illustrates something I’ve always felt, that people should take other’s recommendations for subs with a grain of salt, because it’s only good for their room. You experimented and found what works for your room – that’s the way everyone should do it.

Personally I’ve never felt the need for multiple subs / locations, as I’ve been able to get acceptable results at the seating locations I cared about. Maybe I’ve been lucky. The null I got with my most recent situation (a first for me) has, to my surprise, proved to be a non-event. Don’t even hear it with program material.

We have seriously hi-jacked this thread. I’m surprised Amir hasn’t shown up to spank us all!

Regards,
Wayne A. Pflughaupt

 

[Koeitje]

Hi

Let me ask you a few questions before answering:
Are you a patient person or at least, are you willing to try to be?
Are you willing to devote some time to get the best out of your system
Will your neighbors or better half tolerate the rumble, tweets, screeches of test tones?
Can you devote 4 weeks at least of work, to this project of getting the best out of your system?

If the answer to all those questions is "Yes" then:
Dowload REW (free)
Acquire a miniDSP 2 x 4 ($100)
A miniDSP UMIK-1 ($100)
A pair or trio of 8 or 10 " sealed (if possible) subwoofers for the remaining €800 or so. They don't need to be the last word in subwoofer performance. Say they can reach anechoic 35 Hz.
Then it begins. You will have to read, research, learn how bass works in rooms, how to measure, how to interpret those measures.

A few things that are facts and provable.
Best Bass is obtained with EQ.
Under 80 Hz you cannot perceive location.
You can definitely place one subwoofer in a corner, it may actually help...
In the bass symmetry is not required, you could have one subwoofer in the back of the listening position and another in the front corner.

Ask, some people here are immensely knowledgeable.

Repeating: It will take time. 2 smaller subs are better than one... 3 is even better, past 4 the returns may be too small to matter; two is the minimum. Depending on your room, you may even reach lower Hz lower with the 2, lesser subs ... You may find yourself getting usable response under 20 Hz...

Peace

I have some time, its not like I'm going out much with the current situation . I I already have a UMIK and am currently trying to find out how I will place my system. You can find some long vs short wall measurements below. I don't really know what I'm supposed to make of this, because they both have issues. I won't be able to fix that 50hz bump without corrections on my mains.

 

[Koeitje]

I also measured with the ports closed. Looks like that might be the best starting point to add subs.

 

[watchnerd]

I'm inclined to believe this guy

One big, properly placed sub, with proper room treatment is better than multiple small subs. But if you can't place your sub where it needs to be and you can't manage room modes then multiple subs will help while probably being more expensive.

Of course the guy selling room treatments says to put your money into more room treatments instead of subs...

 

[HammerSandwich]

You can find some long vs short wall measurements below. I don't really know what I'm supposed to make of this, because they both have issues. I won't be able to fix that 50hz bump without corrections on my mains.

Remember that it's much easier to pull down a peak than to boost a null.

 

[Koeitje]

Remember that it's much easier to pull down a peak than to boost a null.

I know, that is why I am worried about my 70-200hz range.

 

[jhaider]

I'm inclined to believe this guy

Didn’t watch the video, but let me guess: dude is selling “room treatments.”

One big, properly placed sub, with proper room treatment is better than multiple small subs.

Ignoring the “room treatment” bit, just because most people can’t or won’t do effective bass treatment (lossy double walls, THICK walls of insulation that take large areas of the room out of use, etc.), one sub with lucky placement and skillful EQ may be great for a single listener in a single spot. Add in a second listener or one who might move around, and the single sub will be much worse.

 

[jhaider]

No one ever seems to mention that Harmon’s experiments and theories on multiple subs were derived in shoebox rooms. It’s good and fine if you happen to have your set-up in a room like that, but it’s not of much use for the rest of us.

That does have implications their for placement recommendations. Placement recommendations are dumb anyway: in the real world, subs go where they will fit and wires can be run for the most part.

It does not change the underlying reality

 

[georgeT]

Of course the guy selling room treatments says to put your money into more room treatments instead of subs...

He has a video on multiple sub placement for those that want to go that route. The solution to place multiple subs to excite multiple room modes at once so you can "smooth out response" is not exactly a solution. Though some find it convenient to put subs in the corners of the room then to put a single large one almost in the middle of the room.

 

[Koeitje]

I am one step closer to what I want. I was having a hard time making a choice with regards to my source, with me really wanting a MiniDSP Studio SHD because it does everything. But that thing is so bloody expensive that I said fuck it, and scored a mint IOTAVX 7.1 4K processor on eBay. I don't have much fate in the room correction or measured performance (the DAC chips specs are 100 SINAD...and IOTAVX doesn't even provide specs), but for the money of a single Studio SHD I can buy this with 2 subs (for which I don't have to worry about having high-level connections). It has a built-in parametric equalizer and enough options to set the cross-over properly. So if it can't configure itself, I can use my UMIK and REW to tune it better. Besides, I've listened to crappy DACs such as the Modi Multibit without frustrating myself .

@Xulonn I joined the club

 

[jhaider]

The solution to place multiple subs to excite multiple room modes at once so you can "smooth out response" is not exactly a solution.

I’d like to see the logic that leads to such a conclusion.

 

[watchnerd]

I’d like to see the logic that leads to such a conclusion.

Perhaps some in the thread are not aware of the existing literature and studies on the topic showing the effect of multi subs.

 

[georgeT]

Perhaps some in the thread are not aware of the existing literature and studies on the topic showing the effect of multi subs.

"Most of the experiments were carried out in a 20’ x 24’ x 9’ virtual test room."
perhaps some in the thread have empty virtual rooms.