Room modes: absortion, bass traps, Eq, speaker position... what really works?

[murillollirum]

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.

[45]

Originally Posted by 1audiohack

Using a frequency domain solution for a time domain problem is at best a bandaid

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....

[45]

Originally Posted by murillollirum

my room is very small for a 15 inch speaker that I use, the 38Hz - 350Hz is really a problem because of the room modes interaction with the speaker, anyone solved this kind of problem with room treatment or eq? I would like to hear some...

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).

[gedlee]

Originally Posted by murillollirum

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.

Now let's hear the GURUS.

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.

[Joel Wesseling]

Can someone point to a Full Range Frequency Response Curve for DBA?
Is the Bass Shelved?

Also How does the Bass Sound with DBA..
Listenening goes beyond measurement.. Does bass sound clean?

[gedlee]

Originally Posted by Joel Wesseling

Listenening goes beyond measurement..

No it doesn't. No data means you are guessing and completely at the mercy of your biases.

[Joel Wesseling]

Originally Posted by gedlee

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..

[dumptruck]

Originally Posted by Joel Wesseling

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.

[markus76]

Originally Posted by Joel Wesseling

Can someone point to a Full Range Frequency Response Curve for DBA?
Is the Bass Shelved?

Also How does the Bass Sound with DBA..
Listenening goes beyond measurement.. Does bass sound clean?

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.

[markus76]

Originally Posted by 45

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....

Care to elaborate?