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4-pi box size !!! [message #60602] Sat, 15 August 2009 02:49 Go to next message
Wayne-o is currently offline  Wayne-o
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Registered: May 2009
Master
If you did not want to use subs ,would you advise to make the 4-pi box size larger if you wanted it to have the same bass extension like the 2-pi tower?? Or is there other reasons to keep it around 3.2 cu. ft. ? thanks.
Re: 4-pi box size !!! [message #60604 is a reply to message #60602] Sat, 15 August 2009 09:06 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Sure, you could go up to five cubic feet or so for increased bass extension.

Re: 4-pi box size !!! [message #60608 is a reply to message #60604] Sat, 15 August 2009 18:42 Go to previous messageGo to next message
Wayne-o is currently offline  Wayne-o
Messages: 225
Registered: May 2009
Master
would 5 cu. ft. go down as low as the 2-pi towers??
Re: 4-pi box size !!! [message #60609 is a reply to message #60608] Sat, 15 August 2009 20:10 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Yes, just about the same on the bottom end.

Re: 4-pi box size !!! [message #60619 is a reply to message #60609] Tue, 18 August 2009 01:46 Go to previous messageGo to next message
feket663 is currently offline  feket663
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Registered: August 2009
Location: Hungary
Chancellor
And a bass-reflex port? same as the original?
Re: 4-pi box size !!! [message #60624 is a reply to message #60619] Tue, 18 August 2009 10:14 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

No, you'll need to size it to tune the box to 38Hz.

Re: 4-pi box size !!! [message #60625 is a reply to message #60624] Tue, 18 August 2009 10:15 Go to previous messageGo to next message
feket663 is currently offline  feket663
Messages: 28
Registered: August 2009
Location: Hungary
Chancellor
Thanks Wayne!
Re: 4-pi box size !!! [message #60632 is a reply to message #60625] Wed, 19 August 2009 08:30 Go to previous messageGo to next message
Wayne-o is currently offline  Wayne-o
Messages: 225
Registered: May 2009
Master
How much extra space in cu. ft. should you add to box volume for area taken up by woofer,horn and bracing ? THANKS
Using CSG to calculate displacement volume [message #60633 is a reply to message #60632] Wed, 19 August 2009 10:30 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

You can calculate displacement volume using a CSG estimate. CSG is constructive solid geometry and it's a term I borrowed from computer graphics that describes what I'm talking about. As an aside, I was a contributor in the POV-Ray ray tracing project, providing the support for the Inmos line of multi-processors. That's where my ray-tracing terminology comes from, but I was actually using this same process long before ever calling it "CSG" - There is a program called "volume.exe" in the original PiAlign distribution archive, and it was written in the 1970's. I used it as a simple calculator, allowing me to estimate volume offsets using a CSG approach.

Using a combination of primitive shapes (cylinder, wedge, cone, etc.), describe the parts inside the box. For example, a brace is a simple box so that one is easy - just calculate its volume using HxWxD. Write that down. To calculate a loudspeaker, simplify its shape as a cylinder (the magnet) and a cone (the basket and cone assembly). The formula to calculate the volume of the magnet (cylinder) is πR2H and the formula for the cone is πR2H/3. Simply make some measurements of your parts and calculate the volume offsets. You can go to whatever level of detal you want when estimating shapes, for example, you can use a single cylinder to estimate the magnet or if it has a bulge in the center, maybe you'll calculate as three cylinders. A horn may make be modeled as a wedge or a pyramid or a cone, or perhaps as a combination of several primitive shapes.

icon5.gif  Re: 4-pi box size !!! [message #60669 is a reply to message #60602] Tue, 25 August 2009 17:02 Go to previous messageGo to previous message
feket663 is currently offline  feket663
Messages: 28
Registered: August 2009
Location: Hungary
Chancellor
Dear Wayne! I found this website:http://www.jblpro.com/pub/manuals/enclgde.pdf a factory recommended size for JBL 2226 woofer(4 cubic feet enclosure vol., 40 Hz tuned frequency).
Can I use this dimensions for a little better bass response with original 4PI crossover?
Thanks!
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