The Bass System Setup, EQ/Correction Thread

[3ll3d00d]

It's certainly a conundrum, I don't think I have got to the bottom of it yet.

my current theory is that this is the effect of rising group delay at the bottom end of the passband of a fairly small sealed speaker

 

The excess phase view suggests the lower frequencies lead the upper frequencies by ~4ms

 

 

Not 100% confident in this analysis mind you

[Kvalsvoll]

Posted this on gs, thinking it may be relevant for this thread:

 

...

Answer to:

"I have seen speaker manufacturers recommend multiple full range sources rather than LF management for 5.1 rigs."

...

 

Because they do not have the knowledge to understand how this really works.

I will try to explain very briefly why this is a bad idea.

To make this (as suggested - 5 full-range speakers) work, each speaker must be full range, and they must have a reasonably similar response.

Since speaker location is already determined in a 5.1, this has to be fixed acoustically, with dsp/room correction, or a combination.

Even then, it will be next to impossible to get a similar sound field from each speaker, because in a small room the properties of the sound field with one small source will be largely determined by the room, and this can not be fixed by any room correction because there is no means of controlling the direction of the sound.

A sound wave can be described as pressure pulsating in periodic motion - this is what we measure, SPL - and a corresponding particle velocity vector. It is this pv part that determines the intensity and direction of the sound wave. And when the wavelengths get large compared to the size of the room, it will be the room boundaries that determines direction and amplitude of the pv vector relative to the pressure.

So even if you have 5 exactly similar full-range speakers, you will not get bass that has a wavefront (direction) coming from each speaker.

To add to this already hopeless situation, all speakers must also sum correctly for bass signals that are mixed together such that the signal comes from several speakers.

If you separate the low frequencies and add them together, you can send this one-channel signal to a bass system set up to provide a reasonably good bass response, where you actually can control all parameters. If the bass system has smooth frequency response, it will have the same smooth response for each single channel, and also for the sum of all channels. If the tactile response is good, it will be good for all channels.

With 2 subwoofer units you can often get a reasonably good response, for a small home studio. With 4 units it will usually be possible to fill all nulls in the response, and you can also - to some degree - control the direction of the sound field. With proper time alignment of the whole speaker system it will sound coherent with good transient reproduction.

This works because direction of low frequency sound is not audible or detectable due to tactile feel.