Multiple Small Subs - Geddes Approach

[markus76]

How should multiple subs decrease the decay time? They don't change a room's modal field and they don't dissipate energy. They only work as active absorption as long as they radiate energy.

And it's correct to talk about reverberation time because resonances are always part of the reverberation time. If reverberation time says anything useful is another question but reverberation time includes room resonances.

I don't know what others have achieved with 4 subs but the 3 subs setup I use now is lightyears better than what I've achieved with 4 subs.

[Pan]

Originally posted by markus76


Now I know where your misunderstanding comes from. A loudspeaker is not an instrument! It can't recreate the original soundfield at your ears. If you want that, then look for dummy head recordings or wave field synthesis. A speaker for stereo or multichannel sound reproduction in a home listening room just needs to reproduce the original, which is NOT the original venue but what was heard in the control room where the recording was created.

Best, Markus

And if the listening room is the control room, what is the original then?

It's true that a stero set up has its limitations but the frontal wave, the direct sound of a recording is not the weakest point. What I'm saying is that the direct sound from a source can be captured and played back with great accuracy even if the ambience is missing or is distorted.

I'm not surprised that soongsc objects to linear distortion on taiko or timpani since the reproduction of those have shown to have demand high performance in the upper bass. Excessive GD of the speaker and excessive room modes will decrease the fidelity greatly.. even though a lot of the energy is in the midrange. A drum transient is a wide bandwith signal.

And the speakers can not and should not only reproduce what was heard in a control room (stictly speaking they can not reproduce a side chain), they should reproduce the captured signals from the mic's, with or without spices (and sometimes electronic non-acoustical sounds of course) added post recording.

Sure there are recordings that can be said to be created in the studio, but many are created live in a hall or some other venue.


/Peter

[markus76]

And if the listening room is the control room, what is the original then?

Then you're lucky and you hear the original.

Sure there are recordings that can be said to be created in the studio, but many are created live in a hall or some other venue.

That doesn't change the fact that 99% of all recordings, broadcasts and movies available today were created in a studio. And it doesn't change the fact that live recordings are never mixed and mastered at the location of the original venues (use of headphones excluded - but then again the original would be what was heard with the headphones).

When you look at loudspeakers as instruments then sound reproduction becomes arbitrary.

[Pan]

Originally posted by markus76
How should multiple subs decrease the decay time? They don't change a room's modal field and they don't dissipate energy. They only work as active absorption as long as they radiate energy.

By avoiding the excitation of the resonance the time/transient behaviour is improved. In a minimum phase system frequency and phase goes hand in hand.

And it's correct to talk about reverberation time because resonances are always part of the reverberation time. If reverberation time says anything useful is another question but reverberation time includes room resonances.

I seem to remember that measuring and calculating reverberation time demands/assumes diffuse field and a discrete resonance/standing wave is not a diffuse field phenomena. Only above the Schroeder frequency we can talk about reverberation time. I may remember wrong though and the important thing is of course not what it is called (though it makes conversation easier :-) but to understand the underlaying phenomena.

I don't know what others have achieved with 4 subs but the 3 subs setup I use now is lightyears better than what I've achieved with 4 subs.

I have achieved better subjective and measured results with four subs. The more subs the better you can fight the excitation of the room resonances. The people at Harman and also people here in Sweden have ended up at four as a good compromise.


/Peter

[markus76]

Originally posted by Pan
I have achieved better subjective and measured results with four subs. The more subs the better you can fight the excitation of the room resonances. The people at Harman and also people here in Sweden have ended up at four as a good compromise.

Without showing any data your comment again is useless.

[markus76]

Originally posted by Pan
By avoiding the excitation of the resonance the time/transient behaviour is improved. In a minimum phase system frequency and phase goes hand in hand.

You can't and you don't want to avoid the excitation. The decay time itself stays the same.

[Wayne Parham]

Originally posted by markus76
I don't know what others have achieved with 4 subs but the 3 subs setup I use now is lightyears better than what I've achieved with 4 subs.

Is this a misprint? Did you mean to say what you've done with three subs is light-years better than what you've done with one sub?

I wouldn't expect a huge improvement going from three to four, but I wouldn't expect performance to go down either. If nothing else, you could put two subs in the same place and you should expect parity with the three-sub setup. Move it around, in the right spot, it just about can't help but smooth the sound field further. The question of adding subs isn't whether it will smooth the field, it is by how much. There comes a point of diminishing returns.

[markus76]

Originally posted by Pan
I seem to remember that measuring and calculating reverberation time demands/assumes diffuse field and a discrete resonance/standing wave is not a diffuse field phenomena. Only above the Schroeder frequency we can talk about reverberation time. I may remember wrong though and the important thing is of course not what it is called (though it makes conversation easier :-) but to understand the underlaying phenomena.

If you're talking about RT60 then a diffuse field is assumed. A real diffuse field (isotropic and homogeneous) exists only in theory. But it works accurate enough for large spaces. In small spaces reverberation time can only be a measure to do comparative studies because the sound field is highly directional.

[markus76]

Originally posted by Wayne Parham

Is this a misprint? Did you mean to say what you've done with three subs is light-years better than what you've done with one sub?

No, I said that what I've done with three subs is light-years better than what I've done with four subs.

[Pan]

Originally posted by markus76


Without showing any data your comment again is useless.

And you're as charming as usual.

I don't have to show data as physics dictates these things.

I have shared lots of information and experience that has helped many people, wihtout showing data. I know you think everything I say and do is useless you don't have to say it. I'm not here for you but for people willing to learn and who appreciate when people take the time to explain things.

You know, an alternative to your rudeness would be something that a person with normal social skills might have said instead, like "oh interesting, did you save some graphs that you'd like to share?"


It's not like your pisspoor attitude inspires to go search for information and post it here for your benefit.

You are wrong and you make yourself look bad.

Know what, where's YOUR data?? Are you allowed to do things that other are not allowed to do?

Grow up will you!

You can't and you don't want to avoid the excitation. The decay time itself stays the same.

If you do not realize that you can place several sources that avoids excitation of a standing wave you need to be a little more humble and go study basics.


/Peter