Gain help with different front and rear speaker RMS

[Mad Max 10+ year member]

Hi all I'm still trying to learn all this stuff and would appreciate some help on this question that I couldn't find by searching.

I'm powering my front and rear speakers with and alpine 40Wx4 amp at 4 ohms. My front speakers are rated at 110 RMS at 4 ohm and my rear speakers are rated at 65RMS at 4 ohm. Now I was reading the gain setting tutorial but didn't know how to calculate the desired voltage to get the full power out of my amp with lower rated rear speakers. If I just go by the lower rated RMS speakers(the rear ones) am I compromising the output of my front speakers(which I care more about)?

Also can I use a non-digital multimeter? Any reason why not?

Thanks for your help!

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[jmoney579]

Most amps have two gain settings for the front and rear, so you can just set them accordingly. You'll most likely get more output(volume) from the front which isn't undesirable. Also, the formula is sqrt(power x resistance) and you can use an analog multimeter, but it wont be as accurate.

 

[Mad Max 10+ year member]

Ah yeah thank you. Stupid question I remember there being 2 gains now when I was messing with them before.

 

[squeak9798 5,000+ posts]

Hi all I'm still trying to learn all this stuff and would appreciate some help on this question that I couldn't find by searching.
I'm powering my front and rear speakers with and alpine 40Wx4 amp at 4 ohms. My front speakers are rated at 110 RMS at 4 ohm and my rear speakers are rated at 65RMS at 4 ohm. Now I was reading the gain setting tutorial but didn't know how to calculate the desired voltage to get the full power out of my amp with lower rated rear speakers. If I just go by the lower rated RMS speakers(the rear ones) am I compromising the output of my front speakers(which I care more about)?

Also can I use a non-digital multimeter? Any reason why not?

Thanks for your help!

The rear speakers having a lower rated power handling is irrelevant given you "input" the amplifier's rated power output into the formula, and the amplifier can only produce 40w per channel.

sqrt(40*40) = 12.65V

The only time you would use the speaker's rated power in this formula is if you were wanting to limit the power output of the amplifier because it was capable of considerably more power output than the speakers could safely handle. This is obviously not the case in your particular scenario.

The other option here is to set the gain by ear. Though for novices I feel the DMM method gives a decent starting point.