gains using dmm

Hey, there.

First off, I want to make sure DMM means Digital Multi Meter. PLEASE correct if wrong...

I have always set the gains by ear. I have seen in random places here that it's best done using a DMM. My friend just got a cheap one and I would like to know the proper way of going about this. Is it simple? -I'd rather do it the right way.

Also, i've also read here that the voltage display on Crapacitors inflate the actual voltage by .3 - .7 volts - to make them look good. This cheapo Digital Multi Meter reads about the same as the display on the cap, is it right or is it inflating the reading also? BTW, I do have the Big3 done w/ 4g. I only have the cap for the looks as well as the voltage display.

Thanks.

Okay, I found this link from another post:

http://www.subwoofertools.com/forum/setgain.asp

Is this correct? What setting should the DMM be on? Anything else I should be aware of?

Thanks, Javin

Thanks.

-Using the link I found earlier, it requires the wattage at certain load of amp. RMS wattage, correct? So, what if we don't know what the amp puts out (Crossfire CFA390M,  Crossfire claims 390watts RMS @ 2Ohms but feels like 800 on 2 CompVR 12's. Previous owner claimed it was rebuilt and suped-up a little.)? I guess i'll just input 800watts RMS.

Well, my total bass power equals about 650watts RMS (class a/b). My friends' CFA390M is WAY louder than my bass, cheapo battery too. It's gotta be pushing 800, at least. The CVR 12's (400 RMS each) are getting about all they can handle. Sealed box. His gain is only about 1/4th the way up! 390 watts? Yeah, right!

Any other suggestions? Thanks to all.

390 watts is what it's rated at, and with two 25-amp fuses on the power side that's about right for a class A/B amp.  You say your friend "suped it up."  What exactly does that mean?

390 watts into 2-ohms is about 28 volts output.

DYohn

I'm sorry, I was saying how my bass amps are a/b. My friend has the CFA390M, which is a class d, so it's a little more efficient than that.

My total output is about 650watts rms. I have 2 yellowtops, Big3 (4g) done, and a c(r)apacitor. I have my subs in sealed boxes facing down on 4x4's (big improvement BTW).  His CFA390M with cheapo battery and Big3 (4g) in rear-facing sealed box blows mine away. We both have '95 Cavaliers w/ 105amp alts.

His makes hats bounce up and down on my head. His makes his trunk lid dance around even though he's got a big heavy 'double-stacker' import wing, too. Gain about 1/4th way up. That's what this is about anyways, cause I don't know how much his actually puts out so I can't set it w/ DMM.

He didn't rebuild the amp, the person he got it from did so I don't know what they could've done to it. It sure as hell doesn't put out 390 watts!

Thanks for all.

Good point, the fuses would blow if it tried to do more than rated. They must've been full of doodie when they told him it's been suped up. (yep, I wrote doodie, not the explicit word). It has been rebuilt, though. That's for sure.

It's crazy. I can't explain it. We have the exact same car. I have 650 CEA-compliant rms watts with a more efficient box design and his is louder than mine. -I actually have to fold the rear seat down to get the most SPL, he doesn't even need to...

I wish I could upload pics through my work PC (I am at work) cause i'd have him open it up and i'd post a pic of its 'guts'. You guys could then tell me. -But I can't.