Speaker Positioning - Again

Posted by: Greg Beatty on 11 July 2003

Question to the wise.

There are equations for calculating resonant frequencies - such as the modes of a room - and presumably the room resonances that would occur if a speaker were placed at position X.

Now...my limited understanding is that, according to these formulas, the closer a speaker is to a boundary the shorter the resonant wavelength to that boundary would be and consequently the higher the reinforced frequency would be.

Does that make sense?

Now...

Why is it, then, that moving a speaker closer to a boundary reinforces lower frequencies rather than higher frequencies? Is there a formula, or explanation, of why bass is reinforced when a speaker is moved closer to a wall?

- GregB

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Posted on: 12 July 2003 by Greg Beatty
James -

Thank you! That was an awesome explanation Smile

Is there an equation or such that would allow one to quantify and understand the affected frequencies? And do the side walls have a play in this or is it only the distance to the back wall? I'm guessing only the back wall unless the speaker is shoved very nearly in the corner.

- GregB

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Posted on: 14 July 2003 by Greg Beatty
James -

Thank you so much - this is *exactly* what I was looking for.

Measuring the Allae's baffle at about 10 inches, I get:

10 inches = .25 meters

f3 = 115 / WB (where WB = width of baffle in metres)

F3 = 115 / .25 = 460 hz

So everything from 400 hz on down could be affected. This is reaching higher than I expected - I believe middle C is about 250 hz.

The website you linked to offers a schematic for a simple baffle step equalizer circuit. Have you given this a go?

- GregB

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