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In the Forum: Audio Discussions
In the Thread: Romy The Cat's new Listening Room
Post Subject: Enclosure volume LB channelPosted by jessie.dazzle on: 5/11/2010
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Romy wrote:
"...Jessie went for 23 cub feet, shall I go larger?..."
For the McCauley 6174, I incorrectly remembered the ideal volume to have been around 23 cu ft, and that I had been forced to make a compromise; I was incorrect on both counts.
I just ran the calculations again and came up with a figure of 13.8 cu ft (for a QTC favoring transient response, not lowest F3). Then I measured the boxes and they do in fact come out to just under 14 cu ft, once wall thickness, volume for driver and bracing are subtracted. Plugging in a QTC which favors lowest F3 results in a box about half the size.
Then I ran calculations for the enclosure of an Aura 1808.
No idea what's going on here; all online volume calculators (which make use of the same simple formula) indicate that the Aura 1808 requires a very small sealed enclosure (this could at least in part explain the poor results obtained by msaudio using the 1808 in a 24 cu ft enclosure; see above post).
Vb is enclosure volume.
Above calculation based on a QTC of .707 (for lowest F3 figure).
Using a QTC of .577 results in a Vb of 2.4 cu ft.
F3 = The lowest frequency the driver/enclosure are able to produce while output drops no more than 3dB.
QTC = (from http://diyaudiocorner.tripod.com/def.htm) "...The value for the damping provided for a driver in a sealed enclosure. Denotes the enclosures ability to control the driver response at resonance. Qtc = 0.707 is the optimum value for sealed enclosures, providing flattest response and highest SPL for deep bass extension. Enclosures for this value are often rather large. Lower Qtc can give even better transient response, down to a Qtc of 0.577 for the best damping and transients, but the enclosure is usually huge and SPL's are down..."
Below are specs for the driver:
And some links to online calculators:
Enclosure volume based on a desired QTC:
http://www.carstereo.com/help/Articles.cfm?id=26
http://www.diyaudioandvideo.com/Calculator/Box/
To determine QTC of an existing enclosure/driver:
http://www.carstereo.com/help/Articles.cfm?id=30
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