Increasing cabinet volume ??

Flappytango · 5th March 2004, 03:29 AM

Hi,
I am building the Audax 3 way Center channel. i plan on keeping driver placement as planned but want ot make it slightly wider and deeper. It is a ported enclosure and plans can be viewed at madisound.

Anyway as i planned it the internal volume will increase by 25%. Will this be ok? I don't understand well how volume effects ported enclusoures

thanks for any advice

Timn8ter · 5th March 2004, 03:43 AM

I don't think that's a good idea. Increasing the volume of any enclosure by that large an amount is going to have negative results unless you've determined through modeling and crossover testing it'll be an improvement. A slight change in enclosure volume may not hurt. A large increase changes tuning point of the box and provides less back pressure for the woofer. This can cause unwanted peaks and dips, not only in the lower frequencies but possibly in the mid-range too. You may also get less LF output which may be the opposite of what you're trying to accomplish.

Flappytango · 5th March 2004, 03:48 AM

Thanks,

Im not trying to change the sound. i just want ot put my tv on top of it.

if decrease backpressure an issue can i use longer or more narrow ports to compensate?

MarkMcK · 5th March 2004, 03:56 AM

You could make the internal volume less than the outside dimensions of the box. Make the outside of the box large enough to serve as a base for you TV, but make the inside of the box the correct size to tune the enclosure.

Some like to sand fill hollow walls to reduce panel vibration. You could do this and get a better cabinet.

Flappytango · 5th March 2004, 04:13 AM

thanks MarkMck,

i was just considering that. Its going to be one heavy spreaker!

sreten · 5th March 2004, 08:56 AM

JMO but the advice so far is way too cautious.

IMO it will be absolutely fine.

The pink plot shows my estimation using the supplied ports.

If you want to retune the ports, for a plain cylindrical port
reduce its length by 20%, i.e. multiply length by x 0.8.
(i.e. reduce the port lengths by 1")

This will give near the original tuning frequency with
slightly greater bass extension than the original.

sreten.

7V · 5th March 2004, 09:07 AM

You can always reduce the internal volume by putting some blocks of wood into the cabinet.

Flappytango · 6th March 2004, 01:15 AM

sreten,

thanks for your input the plots are interesting. Good to know whichever way i handle it it should not alter greatly the intended response.

5th March 2004, 03:29 AM	#1
Flappytango diyAudio Member Join Date: Jan 2004 Location: Sweden	Increasing cabinet volume ?? Hi, I am building the Audax 3 way Center channel. i plan on keeping driver placement as planned but want ot make it slightly wider and deeper. It is a ported enclosure and plans can be viewed at madisound. Anyway as i planned it the internal volume will increase by 25%. Will this be ok? I don't understand well how volume effects ported enclusoures thanks for any advice

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5th March 2004, 03:43 AM	#2
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	I don't think that's a good idea. Increasing the volume of any enclosure by that large an amount is going to have negative results unless you've determined through modeling and crossover testing it'll be an improvement. A slight change in enclosure volume may not hurt. A large increase changes tuning point of the box and provides less back pressure for the woofer. This can cause unwanted peaks and dips, not only in the lower frequencies but possibly in the mid-range too. You may also get less LF output which may be the opposite of what you're trying to accomplish.

5th March 2004, 03:48 AM	#3
Flappytango diyAudio Member Join Date: Jan 2004 Location: Sweden	Thanks, Im not trying to change the sound. i just want ot put my tv on top of it. if decrease backpressure an issue can i use longer or more narrow ports to compensate?

5th March 2004, 03:56 AM	#4
MarkMcK diyAudio Member Join Date: Aug 2003 Location: Ohio	You could make the internal volume less than the outside dimensions of the box. Make the outside of the box large enough to serve as a base for you TV, but make the inside of the box the correct size to tune the enclosure. Some like to sand fill hollow walls to reduce panel vibration. You could do this and get a better cabinet.

5th March 2004, 04:13 AM	#5
Flappytango diyAudio Member Join Date: Jan 2004 Location: Sweden	thanks MarkMck, i was just considering that. Its going to be one heavy spreaker!

5th March 2004, 09:07 AM	#7
7V diyAudio Member Join Date: Feb 2003 Location: North London	You can always reduce the internal volume by putting some blocks of wood into the cabinet.

6th March 2004, 01:15 AM	#8
Flappytango diyAudio Member Join Date: Jan 2004 Location: Sweden	sreten, thanks for your input the plots are interesting. Good to know whichever way i handle it it should not alter greatly the intended response.