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-   -   Possible PRV 12", wild burro combo OB? (http://www.diyaudio.com/forums/full-range/219030-possible-prv-12-wild-burro-combo-ob.html)

TicoLizard 3rd September 2012 11:37 PM

Possible PRV 12", wild burro combo OB?
 
Hi Guys,

I know "there ain't no substitute for cubic inches" for an Open Baffle woofer, but I can probably get these locally, and I have a WAF issue as far as space is concerned in our den. I am thinking of a 15" baffle with 8" 90% wings at the bottom, tapering to about 4" where the Wild Burro Betsy would be mounted following the golden ratio of .6 from one side to 1 on the other to 1.6 from the top. (Haven't calculated exact dimensions yet.)

Here is a link to the woofer:

http://prvaudio.com/images/12W600_Datasheet.pdf

Probably best to use a plate amp and my home theater receiver to cross at around 100 hz. (Seems easier than trying to do it passively)

Questions.

1. Would there be any advantage, using only one per side? I am thinking cleaner midrange and more volume before excessive distortion.

2. Would mounting it near the floor give me a little more "oooompf"

siruis815 4th September 2012 01:24 AM

From my experience, the 12" has a much too low of an xmax to be used for OB. A high excursion woofer - anywhere between 10 to 20mm would be much better. Most I've seen use either 1 15" woofer or 2 12s - per side.

To answer your two questions - I'd use two 12's per side mounted in a W-frame, much like Gainphile's newest build (Gainphile: S19 4-Way Dipole Radiator) and even the newest incarnation of the Orion uses 2 12" woofers in a W-frame. Also - mounting near the floor is a must if you're limited on excursion/diameter capabilities.

Andrew Eckhardt 4th September 2012 01:47 AM

I doubt the efficiency claimed below 100Hz with a nearly 70 gram <10" diameter moving assembly, but that isn't so important with an extra amplifier, and you'll never get the 2.5" coil hot before running out of excursion open baffle. Looks like a good OB candidate T/S wise. Adding a pair per side only gets you another 3dB.

norman bates 4th September 2012 02:37 AM

with that small of a baffle, the betsy will roll off far above what you need for a 100hz crossover point.

TicoLizard 4th September 2012 01:29 PM

OK, guys, thanks for the help. What I think I am getting here:

Sirius815: need at least 2 for sufficient xmax.

Andrew: May work because of extra amp.

Norman: Baffle is too small for 100hz crossover. Looks like I need to use a spreadsheet to see where to cross and maybe rethink the design depending on the highest crossover point available on my JVC receiver.

Will it matter how far away the woofer is from the full range? There is a point where center-to-center spacing becomes too great and you can hear individual drivers instead of a coherent whole, but I am not sure how to calculate that.

Thanks again. Any more thoughts would be very welcome.

siruis815 4th September 2012 11:19 PM

**By two, I didn't mean the two you had picked out. I think you'd need closer to 4 per side of the PRVs.

For the distance center to center - I think it was no more than a 1/4 wavelength apart.


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