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-   -   15" PVC Pipe Dipole Project (http://www.diyaudio.com/forums/subwoofers/109011-15-pvc-pipe-dipole-project.html)

penderaudio 25th September 2007 04:27 AM

15" PVC Pipe Dipole Project
 
Ive been working working on a new Dipole project for the past two months. It will be a two way system design with two 15" XBL subs mounted in 15" PVC pipe for the low end and a Hemp DIY 8 for the top end. The pipe has an ID -'inner-diameter' of 14.875 " and an 'OD' of 15.375 it's pretty heavy duty stuff. This works very well for any sub with a 12 spoke Aluminum Basket. (This is an old car audio SPL comp trick)

I'm thinking about making the tubes 16" long per sub which will should give each driver quite a bit of baffle. The only worries I'm having is that the PVC may resonate at a lower frequency than I'm expecting. Since the low x-max HempAcoustics DIY 8 will be used for the top end im thinking that the subs will have to x-over
at 120-160hz, maybe even higher to get the output im looking for.

The 15" drivers are a short run, limited production Exodus subs from DIY Cable, They are very similar to Adire Tempest but with a Aluminum basket and maybe a larger motor. High Qts .6-.7, Low Fs-24 "I think.

I was wondering if anyone has any ideas or experence with puting large drivers in large PVC pipe. I'm sure there could be bad things that happen depending on how high they play, and how long the tubes are.

I will post pics of the project in the next day or so(Out of town on Biz this week)

penderaudio 25th September 2007 04:17 PM

2 Attachment(s)
here is a pic of the 12" version of the Driver. Ow ya the 15's were a heck of a deal @ $160 per.

penderaudio 25th September 2007 09:50 PM

2 Attachment(s)
Here is a picture of the 15" drivers and one of the PVC pipes cut to 16" long. The pipe is covered in 1/8th inch bendable birch, this makes the gasket on the sub flush with the Pipe.

Any thoughts on Frequency responce compared to a more traditional U-frame baffle.

penderaudio 25th September 2007 09:51 PM

2 Attachment(s)
here is two more of them

tade 26th September 2007 05:31 PM

I would not fret about resonances with the PVC, that stuff has good damping and is really tough. Given that it is cylindrical it ought to withstand pressure even better. not that there is going to be much pressure in a short U frame. As for frequency response that will depend on the design because the materials and contstruction seem very sound.

where did you source such big pipe? I like putting the wood veneer on the tubes. Isn't it great when you find a building material that simplifies things to such a great degree! IE Sonotube

How do they sound?

penderaudio 26th September 2007 06:33 PM

The 15" PVC is technically Sewer pipe, I sourced it from a heavyduty pluming supply. "HD Waterworks in my area" Just a warning the Pipe is costly-$9.00 per foot and the shortest section avaliable was 14 feet long. It's very heavy the whole thing weighed about 200lbs.
I'm planning on finnishing the outside of the PVC with Mahogony for the finnish.
Have only test run 2 of the 4 hooked up with Crown DC-300's @ 300 watts per driver. they seem to roll off around 40hz and seem really strong in the 60-100 hz range. This was just a short test done by ear with a test tone CD.
I try to use different materials in my designs beacause everybody uses MDF and makes square boxes. Fiberglass is one of my favs-If im willing to spend days sanding and finnishing.


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