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Port length on multiple ports [message #33904] Mon, 24 September 2001 06:28 Go to next message
AP is currently offline  AP
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What happens to port length when 2 or more ports are used in the same box??

Scott

Re: Port length on multiple ports [message #33905 is a reply to message #33904] Mon, 24 September 2001 10:08 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)
Grab a copy of BoxPlot because it will calculate multiple ports.
Re: Port length on multiple ports [message #33946 is a reply to message #33905] Thu, 27 September 2001 09:52 Go to previous messageGo to next message
AP is currently offline  AP
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Registered: May 2009
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Thinking about a home project related to this.

Vas-151L
Qts-.39

Coffee table size box (yes, it would me my coffee table). Internal dimensions 13"x22.5"x34.5" (assuming 3/4" wood). I figure I'd end up around 155L with internal bracing. 4"x12" port. Tuned to 21 Hz. Driver and port on one end. As near as I can tell, it'll stay flat and 3db down would be around 20Hz. What do you think?

Thanks man!
Scott

Re: BTW, it's a 12..... [message #33947 is a reply to message #33946] Thu, 27 September 2001 09:53 Go to previous messageGo to next message
AP is currently offline  AP
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Box tuning [message #33948 is a reply to message #33947] Thu, 27 September 2001 11:05 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)
To calculate box tuning, you'll need to know a little more. What is the resonant frequency in free air?
Re: Box tuning-Fs=21Hz [message #33957 is a reply to message #33948] Fri, 28 September 2001 05:58 Go to previous messageGo to next message
AP is currently offline  AP
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PiAlign'ed at 2 cu ft tuned to 20Hz [message #33958 is a reply to message #33957] Fri, 28 September 2001 06:27 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)
You have a motor with these specs:

Vas=5.33 cu ft
Fts=21Hz
Qts=0.39

So PiAlign equivalents are:

Vad=5.33
Frd=21Hz
Qd=2.56

PiAlign recommends a 2 cubic foot cabinet tuned to 20Hz using either a cylindrical 5" long, 1 5/8" diameter port or a rectangular 1" x 2" x 5" long port.

You can grab a copy of BoxPlot on the Pi Speakers website to show the response of this cabinet using Thiele/Small analysis. The box you've proposed is about 5 cubic feet, and I suspect that will work just fine. The driver will probably work very well in cabinets from 1.5 cubic feet to 6 cubic feet or so, tuned to 20Hz. You can use BoxPlot to find an alignment that will give acceptable response in this size cabinet.

Re: PiAlign'ed at 2 cu ft tuned to 20Hz [message #33959 is a reply to message #33958] Fri, 28 September 2001 07:39 Go to previous messageGo to next message
AP is currently offline  AP
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Thanks for the help Wayne.

Scott

Re: PiAlign'ed at 2 cu ft tuned to 20Hz [message #33961 is a reply to message #33959] Fri, 28 September 2001 10:53 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)
No problem. Let us know how it works out.
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