Question about JL 300/4?

[a06144]

I am considering the JL 300/4 and how the following question:

I am planning to install this amp as you illustrate on your website (http://www.jlaudio.com/amps/pdfs/SYS_4.pdf). Both speakers illustrated are 4 ohms (VR650-Cs and VR525-Cx), so if you parallel them, would you still get 75Watts per channel or 38Watts?

I heard that if you have 4 speakers connected in parrallel to 2 channels of the JL 300/4 it would result in a decrease in power from 75Watts to 38Watts. Is this correct? Is this the reason why its illustrated to use an 8 ohm resistor inline with the second speaker in parrallel?

Thanks,

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[helotaxi 5,000+ posts]

The "Slash" series JL amps put out the same power at any load from 1.5-4 ohms. If you parallel two speakers on one channel of the amp, the power produced by the amp does not increase and the two speakers must share the available power. In the system diagram you linked to, the resistor acts as an attenuator on the rear fill speakers and serves to redistribute the power between the front and rear. Without the resistor, the front and rear speakers would each get 37.5 watts. With the resistor, the front speakers are getting 56.25 watts and the rear are getting 6.25 watts and the resistor is turning 12.5 watts into heat. Not the most efficient use of power but it does properly (somewhat anyway) distribute the sound front to rear.

If you are curious I can walk you through the math to derive all this.

 

[a06144]

Thanks, that explains it perfectly.

 

[helotaxi 5,000+ posts]

You're welcome. Glad to be of service.

 

[indosia 10+ year member]

Forget the rear speakers and the resister, just run the 2x 75 watts to your front speakers. and the other use the other 2 channels for bass. You dont want any highs coming from behind you.