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#### raynist

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About a year ago I found a calculator that you could plug in the distance from your speaker baffle distance to the front wall and I think the distance to your seating position and it would tell you what frequencies would be canceled.

I lost the link, does anyone know of an online calculator like this?

Thanks
Ray

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#### tuxedocivic

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80 / distance from baffle to back wall in meters = Cancellation frequency. ie. 80 / 0.75m = 106 hz

That's pretty crude and doesn't tell you the multiples though. That formula is speed of sound divided by distance divided by 4, as the 1/4 wavelength from a reflection will cause the null. 1/2 wavelength is out of phase, so 1/4 + 1/4 travel length gives 1/2 wavelength.

#### goonstopher

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So doea this mean we want speakers either in wall or way out into the room?

#### tuxedocivic

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At least 1m for an 80hz cross over. Or my preference is in wall. Very awesome in my experience.

Put the screen up and people don't even know I have a full blown system.

#### Bill Fitzmaurice

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So doea this mean we want speakers either in wall or way out into the room?
It does with respect to mains. Subs are fine if the cone is placed less than 3 feet or so from the wall.

#### goonstopher

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It does with respect to mains. Subs are fine if the cone is placed less than 3 feet or so from the wall.
Yikes... I'm screwed then ha...

#### Bill Fitzmaurice

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Yikes... I'm screwed then ha...
Most of us are. This issue was identified by Roy Allison over 40 years ago, but the loudspeaker industry as a whole is loath to tell their customers that to eliminate it they must either flush mount or stand mount mains with an 80Hz high pass at least 4 feet out from the wall. Then consider a full range floor stander that runs to 40Hz, which would have to be at least 8 feet out. Rather than admit that there's a pretty much insurmountable problem for most users the industry simply ignores it.

#### raynist

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Would it still be beneficial to create a baffle wall with an opening a few inches bigger than the actual speaker so you can play around with toe in?

#### Bill Fitzmaurice

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Would it still be beneficial to create a baffle wall with an opening a few inches bigger than the actual speaker so you can play around with toe in?
It would, because the affected wavelengths are long enough to be minimally affected by a small gap between the wall and speaker.

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