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View Full Version : What's the difference in mass between PR15 and PR15C?



Virak
11-14-2011, 03:05 AM
I recently bought a DIY Sovereign/Olympus cabinet with 136A woofers and PR15 passive radiators, and have been informed that the correct radiator for the 136A is the PR15C.
http://www.audioheritage.org/vbulletin/showthread.php?32019-Which-JBL-Sovereign-ish-speaker-have-I-bought

So, does anyone know the difference in mass between the PR15 and PR15C?
I'd like to make the PR15 into a quasi-PR15C (if the C-version is actually the heaviest, of course).

Mr. Widget
11-14-2011, 10:06 AM
I have no idea, but as I mentioned in your other thread, the passive radiator behaves like a tuned bass reflex port. If you don't want to plug the hole and add a port, you can add mass... or lower the mass to achieve the desired results... I imagine there will be non linearities as the power level goes up and the PR15's suspension comes into play, but regardless, if you can take impedance measurements you want to achieve a curve something like these... The minimum point between the two impedance rises is your tuning frequency. Personally I prefer using a close mic on the cone and look for a frequency minimum, but that requires more sophisticated test gear.

Regardless of the method you choose to tune your cabinet, you will want it tuned to between 30Hz and 35Hz.


Widget

Odd
11-14-2011, 02:34 PM
I recently bought a DIY Sovereign/Olympus cabinet with 136A woofers and PR15 passive radiators, and have been informed that the correct radiator for the 136A is the PR15C.
http://www.audioheritage.org/vbulletin/showthread.php?32019-Which-JBL-Sovereign-ish-speaker-have-I-bought

So, does anyone know the difference in mass between the PR15 and PR15C?
I'd like to make the PR15 into a quasi-PR15C (if the C-version is actually the heaviest, of course).

From JBL Instruction Manual pdf

Tuning The Enclosure

http://www.lansingheritage.org/html/jbl/plans/jbl-plans.htm

Virak
11-14-2011, 03:58 PM
From JBL Instruction Manual pdf
Tuning The Enclosure
http://www.lansingheritage.org/html/jbl/plans/jbl-plans.htm
Takk, skal sjekke det ut :)


I have no idea, but as I mentioned in your other thread, the passive radiator behaves like a tuned bass reflex port. If you don't want to plug the hole and add a port, you can add mass... or lower the mass to achieve the desired results...

If it improves the performance, I don't mind using a port instead of the passive radiator. Since it's not a factory build, I don't feel a need to keep it "stock". I just want to make the best out of the speakers. However, I don't have measuring equipment, or the knowledge to do this on my own. How do I figure out the port diameter/lenght for my cabinets? Is there a calculator for woofer caracteristics vs. volume of enclosure? Any pointers on how to do it?

Mr. Widget
11-14-2011, 04:29 PM
How do I figure out the port diameter/lenght for my cabinets? Is there a calculator for woofer caracteristics vs. volume of enclosure? Any pointers on how to do it?If you accurately measure the internal volume of your speakers, there are a number of box tuning calculators that will work. I'll be happy to run the numbers through Bass Box Pro.


Widget