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Old 22nd March 2013, 06:48 AM   #1
diyAudio Member
Join Date: Jan 2011
Default volume displacement vs room size

this question is bit of subjective! i have a room of 10x12 feet approx. how much min. volume displacement would be needed for acceptable low bass of 20hz at 90db SPL. is there any calculator for this?
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Old 22nd March 2013, 09:36 AM   #2
diyAudio Member
Join Date: May 2009
Location: New Zealand
The SPL is simply the ratio between the volume displacement of the speaker and the volume of the room. If you have Excel, I have attached a small spreadsheet. It'll help you determine if your intended speaker will get near the figure you want. This assumes a sealed room with rigid walls, and real rooms are anything but. It also assumes that the frequency of interest is below the lowest room resonance.
Attached Files
File Type: zip Room_SPL.zip (1.8 KB, 20 views)
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Old 22nd March 2013, 09:54 AM   #3
diyAudio Member
Join Date: Jan 2011
hi Don, thanks for the simple tool. according to this, with just two 12" sub having Xmax of 6mm, SPL can reach to 100dB. but at what frequency?
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Old 24th March 2013, 09:59 AM   #4
diyAudio Member
Join Date: May 2009
Location: New Zealand
At all frequencies(*). SPL due to "room pressurisation" is frequency independent.

(*) "All frequencies" is theoretically correct but in practice only makes sense below the lowest room resonant frequency. I suggest the following thread for further reading:

modeling room gain
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Old 24th March 2013, 10:55 AM   #5
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
I downloaded and saved the post2 xls.
For a room of 131cub m, it predicts that I cannot get 100dB of SPL at any frequency from 4 off 18" speakers when I limit Xmax to 4mm and Sd=1100

Is that right?

Are your units correct?
18" has Sd=1300mm²
That should be 1300cm²
regards Andrew T.
Sent from my desktop computer using a keyboard
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