I have a book of Mr. Floyd E. Toole called sound reproduction, and there is a chapter called (Delivering good bass in small rooms) wich I will resume for you in some declaration and observations.
1. The use of multiple subwoofers to manipulate sound fields, controlling the energy delivered to room modes is a recent develpment and the results of this approach are very good.
2. In stereo, it was common to think of a sweet spot, and make all arrangments to have this optimum single listener.
3. However, the existence of standing waves among the roo mensures that other seats experience difference bass.
4. To deliver a good bass to several listeners, the room resonances must be physically manipulated.
5. Acoustic: attacks the problem with absortion
6. Absortion is Always a good idea but it’s difficult.
7. The absortion material has to be placed away from the room boundaries ato ne-quarter the wavelenght (30Hz 2.9meters!)
8. at the corners “bass traps”do not work because there is located the max sound pressure, not particle velocity.
9. There are two ways to vary the amount of energy transfered from loudspeakers tom odes:
a. Locate the subwoofer near a pressure minimum in the offending standing wave
b. Use 2 or more subs to drive the standing waves constructively or destructively. 2 subwoofers connected in parallel, one in each side of a null will destructively drive the mode; positioned two nulls apart, the same subs will amplify the mode
10. The improvement of seat-to-seat bass variations of using multiple subwoofers is vey small when using more than 4.(this was tested buy a Harman guy, using from 1 to 5000 subs in a room)
11. The best subs position using two is one at the middle of the front wall and the other in the opposite back wall; using 4 is one at each corner, or one at the middle of each wall
12. Two midwall subs Works as well as four subs
That’s it.
Now let's hear the GURUS.
1. The use of multiple subwoofers to manipulate sound fields, controlling the energy delivered to room modes is a recent develpment and the results of this approach are very good.
2. In stereo, it was common to think of a sweet spot, and make all arrangments to have this optimum single listener.
3. However, the existence of standing waves among the roo mensures that other seats experience difference bass.
4. To deliver a good bass to several listeners, the room resonances must be physically manipulated.
5. Acoustic: attacks the problem with absortion
6. Absortion is Always a good idea but it’s difficult.
7. The absortion material has to be placed away from the room boundaries ato ne-quarter the wavelenght (30Hz 2.9meters!)
8. at the corners “bass traps”do not work because there is located the max sound pressure, not particle velocity.
9. There are two ways to vary the amount of energy transfered from loudspeakers tom odes:
a. Locate the subwoofer near a pressure minimum in the offending standing wave
b. Use 2 or more subs to drive the standing waves constructively or destructively. 2 subwoofers connected in parallel, one in each side of a null will destructively drive the mode; positioned two nulls apart, the same subs will amplify the mode
10. The improvement of seat-to-seat bass variations of using multiple subwoofers is vey small when using more than 4.(this was tested buy a Harman guy, using from 1 to 5000 subs in a room)
11. The best subs position using two is one at the middle of the front wall and the other in the opposite back wall; using 4 is one at each corner, or one at the middle of each wall
12. Two midwall subs Works as well as four subs
That’s it.
Now let's hear the GURUS.
Well said!
Some people do not realize it is not correct putting the listener out of the equation!
They don't realize the hypothesis for applying a Fourier transform is violated when the listener is fully part of the chain.
In such case they equalize....
In your place I would exclusively treat the room with acoustically passive solutions (i.e. traps and diffusors using felt and other materials with similar properties). Is the only real solution other then having a better room from the start (which will need a treatment anyway).
That is a good review, but Dr. Toole's analysis is already out of date. There really isn't an "optimum" sub placement if EQ is used, as almost any situation can be made equal to any other as long as there are enough subs. The key is how to determine the parameters for the sub controller. That is where the current state-of-the-art is.
No it doesn't. No data means you are guessing and completely at the mercy of your biases.
I wasn't meaning data isn't important.. Data is and the results are heard.
I was inferring that the music signal played through a system and some of the sonic charateristics go beyond what can be shown in a measurements..
Does that conversation really need to start up here? I'm talking to everyone, not just Joel. In principle, it's absurd to suggest there are things heard that can't be measured. The ability to hear is not fully understood, but the input the ear receives is nothing terribly mysterious, and that's what we are working on. In practice, you can suggest that we don't know what to measure or how, but this is not worth discussing unless you have a case where two things sound demonstratively different and measure the same. I'm not aware of that existing when it comes to in-room bass, but few of us have the capability and motivation to measure it properly. If you're interested in hearing subjective reports, just say that. You don't need to justify your interest in hearing what people have to say.
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Full range? Like any distributed sub solution, DBA is for frequencies <100Hz.
For data follow the link I've posted earlier.
How does it sound? Put a subwoofer in the near field and you'll get an idea.
talking of data, can we see some impulse responses from the multi-sub proponents?
Obviously the nature of the problem still isn't well understood.
What would a impulse response tell you? It wouldn't tell me much. Here's a good read:
Bass Integration Guide – Part 1
http://www.hifizine.com/2011/09/bass-integration-guide-part-2/
http://www.hifizine.com/2012/06/bass-integration-guide-part-3/
Anything that flattens frequency response and reduces modal ringing is helpful, passive/active damping and EQ. They are not mutually exclusive.
Here's some time domain data:
Comparison of different near field and far field subwoofer configurations
Yeah thanks, but nothing new there. One data is missing on your paper (nice BTW!). The far field response of two dipoles vs the two monopoles, although I agree near field is usually better.
Who said something is exlusive? It's a package I think we all agree on that.
Another important point is missing, the group delay formed by the crossover and enclosure type. Alhough it does comes through a little bit in your own mesurements if you look carefully.
And directivity, of course, if the room is large..
Who said something is exlusive? It's a package I think we all agree on that.
Another important point is missing, the group delay formed by the crossover and enclosure type. Alhough it does comes through a little bit in your own mesurements if you look carefully.
And directivity, of course, if the room is large..
There is nothing wrong with personal bias and anyway this is a very minor thing in comparison to improper use of acoustics. No measurement can tell what one is going to listen. A microphone is badly "biased" because dosen't work like the brain for which the superposition principle doesn't stand and invariance does not exist to correlate frenquency and time domains. Acoustics, as a branch of physics, cannot deal with musical sounds simply because the musical sound and the physical sound are into different leagues. The latter only exists in an invariant world where laws are always the same; the former doesn't because there is someone associating an emotional state and a meaning to the sound. Physics cannot describe emotions and has never prentended to do so.....
This doesn't mean that acoustics is useless and there is no systematic way of dealing with musical sounds. It just means that acoustics can only give general indications and the final and only language and rules to deal with musical sounds are the same that have always been used for creating and playing music in the associated places. The only reliable instrument for dealing with music is the brain through the ears.
If one keeps the listener into the chain at all stages then it is not possible to use a microphone and frequency responses to deal with a time domain problem. If one excludes the listener until the very last stage then acoustics can be used but it becomes quite an arbitrary procedure, in fact there are quite several opinions regarding measurements, and one is going to be biased by what the microphone tells.....
This doesn't mean that acoustics is useless and there is no systematic way of dealing with musical sounds. It just means that acoustics can only give general indications and the final and only language and rules to deal with musical sounds are the same that have always been used for creating and playing music in the associated places. The only reliable instrument for dealing with music is the brain through the ears.
If one keeps the listener into the chain at all stages then it is not possible to use a microphone and frequency responses to deal with a time domain problem. If one excludes the listener until the very last stage then acoustics can be used but it becomes quite an arbitrary procedure, in fact there are quite several opinions regarding measurements, and one is going to be biased by what the microphone tells.....
I didn't include it because it doesn't add anything new. Here's the data for dual dipoles in the far field:
An externally hosted image should be here but it was not working when we last tested it.
By the way, the near field data is profoundly better than far field regardless of source type (dipole/monopole).
I wish that was true.
Then you see more than I do.
But the room isn't large. We're talking about acoustically small rooms. Directivity is usually moot below 100Hz unless you're in the near field.
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thank you very much, interestingly the response with dipoles is actually better on EVERY situation.
By large I meant more than 5m for the longuest dimension, that's a fairly common situation, even in Europe. So you can get directivity around 60-100hz, which is a perceptually more important zone than 20hz, in my opinion.. Boxless designs do usually offer less GD variations than anything else, at the cost of efficiency, but as you say you can listen closer and get some back.
I myself would not look back, I use dipoles with LF treatment (need some more) and EQ.
By large I meant more than 5m for the longuest dimension, that's a fairly common situation, even in Europe. So you can get directivity around 60-100hz, which is a perceptually more important zone than 20hz, in my opinion.. Boxless designs do usually offer less GD variations than anything else, at the cost of efficiency, but as you say you can listen closer and get some back.
I myself would not look back, I use dipoles with LF treatment (need some more) and EQ.
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