Please explain jbl crossover

[jayam000]

I am trying to understand how JBL have designed SRX 725 crossover.
The SRX 725 have two subwoofers & one compression driver
Subwoofer = 4 ohm Compression driver = 8 ohms. crossover frequency 1.2khz.
I tried with butterworth & linkwitz. But getting different results for woofer crossover values. Hence not tried for compression driver.

Kindly explain me this.

[speaker dave]

When you say "I tried with Butterworth and Linkwitz" I assume you mean you've tried some textbook or software derived values based on a crossover frequency and load impedance. This approach never works with real drivers. The drivers will have their own non-flat response and will also be a particular partly inductive load (not resistive). System designers will generally use non text book values that give the system shape they are looking for. If they use a computer for network design it will need to consider all factors of driver impedance, which is the network load, desired response and crossover frequency, and delay between woofer and tweeter.

With a fairly simple network like you show they might have gotten the values purely from trial and error. They are never likely to be textbook values.

Regards,
David

[ZilchLab]

With dual 15" 2265H in parallel and a SOTA 2452H large-format compression driver crossed at 1.2 kHz, and a max continuous average SPL of 134 dB, those be big guns, indeed. Wear hearing protection.

Second order lowpass and third order highpass with a tank filter doing the HF comp, I'm not sure what the final 0.2 mH is doing. Put it in Spice and find out....

http://www.jblproservice.com/pdf/SRX...es/SRX725F.pdf

[jayam000]

Thanks for reply, Speaker Dave & Zilchlab.

So theory doesn't work here. It is practical design as i understand from reply.