Subwoofer Design Review Please

[jonroy]

Hi everyone,

I currently own:

Dayton RSS390HO-4 15" Reference HO Subwoofer 4 Ohm
Dayton RSS390HO-4 15" Reference HO Subwoofer 4 Ohm | Parts-Express.com

Bash 500W Digital Subwoofer Amplifier
Bash 500W Digital Subwoofer Amplifier | Parts-Express.com

I have them in a big box (too big...) and I want to redesign the enclosure. I want to go for a cylinder enclosure because of the good results I had with woofers in cylinders.

However, the design is quite special. I want to make it out of 2 cylinders (inside and outside). Anyways, look at pictures of my CAD and you will understand.

http://dl.dropbox.com/u/13562986/CylinderSub/1.jpg
http://dl.dropbox.com/u/13562986/CylinderSub/2.jpg
http://dl.dropbox.com/u/13562986/CylinderSub/3.jpg
http://dl.dropbox.com/u/13562986/CylinderSub/4.jpg
http://dl.dropbox.com/u/13562986/CylinderSub/5.jpg
http://dl.dropbox.com/u/13562986/CylinderSub/6.jpg

What do you think (resonance, etc.)?

Thank you very much!

 

[MaVo]

in most subwoofer designs and in this case as well, the shape of the volume behind the driver is just aesthetics, so yeah, its fine to do this. i would definitely fill the void between the tubes though, because that would certainly help to make it vibrate less.

 

[riverwolf]

Jonroy, you'll want to run the 390HO through a sag calculator to find out how suitable it is for downfiring, assuming you're going to orient the cylinder vertically as is usually done. I know some of the RSS series get pretty close to the de facto 5% limit. Read up on sag and subwoofer orientation to decide how comfortable you are with the potential long term effects. BTW, WinISD Pro does the calc automatically in the driver editor's "advanced" tab...value is Gloss%.

You'll need to mod the subsonic filter in the BASH500 for sub duty, IMO. As shipped from P-E, the f3 of the filter is around 30Hz and there's a 2ish dB peak up around 37Hz. Not sure why it's so different from the BASH300, which has a much more reasonable f3=18hz, 1ish db peak around 24Hz. P-E has instructions on the BASH500's page for changing the 2 resistors to adjust the filter.

-Brent

 

[rhapsodee]

Are you planning for a ported or sealed design? Is the gap between the inner and outer cylinder supposed to be the 'port'?

Looks good. You might want to check the cross sectional area of the annulus between the inner and outer cylinders, vs the area of the inner cylinder. If they are very close, you might end up with some unexpected short transmission line quarter wavelength-like behaviour.

 

[Collo]

If you're thinking of using the space between the two layers as a port, this page on concentric ports might be of use to you. If those small holes around the endplate are ports, they're too small and will chuff - go for something bigger!

 

[hooligan72]

Great looking design. I love the unique designs on this forum.

 

[revboden]

I made some assumptions as you did not give the diameter of the inner tube. I assumed a sealed box. I guessed 20in sonotube which at 24in deep... gives a volume of 4.36ft^3 or ~4 after amp and driver are added. My charts show a Qtc of .555, -3db at 50hz and -12db at 20hz. good group delay at 20hz of 8ms. excursion limit reached at 250w at 16hz avg. db107 without filters. should be very musical