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.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

Okay, I found this link from another post:

https://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

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

that is correct...the DMM setting should be on AC voltage within the tartget voltage range if the DMM is not auto ranging

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.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

i wouldn't set it for 800...you are prolly clipping the amp

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.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

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.

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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.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

I doubt that amp is "suped" up to put out more than twice the rated power...if the the person who "suped" up the amp must have added some more fusing to the amp unless he made the amp 200% efficient

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.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

Oh, and his DMM has 2 settings for ACV; 750 or 20-something. Which should we have it on?

Thanks, dudes.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

OK, so what amp and what speakers DO you have?

It is foolish to try and compare why two different installations sound different based on the amp alone.  Power is only one part of the equation.  The speakers, the way they are mounted, and most importantly the enclosure are more important than the raw amount of power.  Overall system efficiency is what matters.  And then of course there's system phase, cabin gain, cancellations due to cabin interactions, etc.

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also enclosure placement

I know what my amp puts out so I can use the link

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

for setting my gains.

The problem is we don't know what my friends' Crossfire CFA390M puts out so I don't know what to input for setting his gains. What I have been trying to figure out is what this monster is pushing. I will say it's not 390wrms x 1 @2Ohms like the manual says. Like I said before, my 650wrms bass system doesn't even come close to what his CFA390M on 2 CVR 12's (@ 2Ohms) is. We have the same kind of car. My box design is more efficient than his, so my bass should be louder than his(650wrms, 3 drivers, more efficient box compared to his '390wrms', 2 drivers, sealed box).

I guess i'll just input 390wrms @2Ohms then. When it says '28volts' and set I the gain to that, it probably won't be as loud as it is now. So I'm stuck.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

Like I said before, it's not about power, it's about how it's being used.

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Support the12volt.com

Alright,  I'll input 390wrms @2ohms. Thanks, guys.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001