setting gains with a dmm (searched)

[sciullo779 10+ year member]

i searched but couldnt find a direct link on how to do this

ok i have 2 powerbass m10's each rated for 300wrms@4ohm, i wired them in parallel for 600wrms@2ohm, and im buying a kicker zx750.1 i want to power these subs to roughly 575-590wrms and i need to know how to figure out what voltage to look for at the speak outputs for that rms wattage, is it like the square root of rms desired?

another question, wouldnt putting no load on an amp fry it?

PS what speaker wire gauge should i be using to hook these subs up?

Click to read more...

 

[Mass Car Audio 10+ year member]

http://www.caraudio.com/forum/showthread.php?t=63933

I found it in 2 seconds.

 

[SPL Blazer 10+ year member]

lol, good luck with that one, there are 44 pages to that thread.

 

[csu87 10+ year member]

have you tried google because last time i looked the first 5 or so pages explain it

 

[BloodyGuts335i 10+ year member]

I know its from another forum but it's very helpful and it works!!! also its not as many pages..

http://www.caraudioclassifieds.org/forum/showthread.php?t=19628&highlight=setting+gains

 

[ngsm13 5,000+ posts]

It's worthless...

nG

 

[BeAlLsTaR13 10+ year member]

setting it by ear is better than DMM... IMO

o-scope is the best, then ear, then DMM... well thats only if you know what distortion sound like.. well.. you know its distorting when it sound like shit

 

[gunz4me2 10+ year member]

The DMM method that everyone on this forum so relies on should only be used secondary to one's ear. Why? Because that amplifier WILL perform differently when you load it down.

If one wants to use electronic gadgetry to properly set the gains, they will need: an oscilloscope, a couple of ammeters, a couple of digital multimeters, various test tones recorded at the appropriate dB level for the headroom desired, and the appropriate resistive loads that can take the power one will throw at them for the load desired. That will get one closer!

The ammeters are optional, BUT, that will give one an accurate representation of current draw and amplifier output at clipping.

 

[Mass Car Audio 10+ year member]

The DMM method that everyone on this forum so relies on should only be used secondary to one's ear. Why? Because that amplifier WILL perform differently when you load it down.
If one wants to use electronic gadgetry to properly set the gains, they will need: an oscilloscope, a couple of ammeters, a couple of digital multimeters, various test tones recorded at the appropriate dB level for the headroom desired, and the appropriate resistive loads that can take the power one will throw at them for the load desired. That will get one closer!

I always use my oscilloscope when I install stuff for friends and customers.

 

[SPL Blazer 10+ year member]

I always use my oscilloscope when I install stuff for friends and customers.

lol, most shops around here either don't have an oscilloscope scope, or have no idea what one is.

 

[Mass Car Audio 10+ year member]

lol, most shops around here either don't have an oscilloscope scope, or have no idea what one is.

shops around here don't know what one is either. When I show people it they are like WTF is that thing ? Most of them don't really understand what is used for even after I explain it to them.

 

[SPL Blazer 10+ year member]

I wanted to learn more about oscilloscopes and reading them, but since nobody near me had a clue what one was, I never had the chance to work with one.

 

[sciullo779 10+ year member]

could i use a "automotive diagnostics scope" , it shows ignition waveforms, and shows ac voltage as a sine wave and you can adjust the timeframe shown on the monitor, 1ms, 10 ms, 25ms, 50ms...etc

 

[DNick454 10+ year member]

could i use a "automotive diagnostics scope" , it shows ignition waveforms, and shows ac voltage as a sine wave and you can adjust the timeframe shown on the monitor, 1ms, 10 ms, 25ms, 50ms...etc

With timeframes like 1 ms, 10 ms, and 25 ms, you probably won't be able to use that. That's meant for car ignitions which fire at a much higher rate probably. If you use 20 ms, you might be able to capture one sine wave. Would be better if you had a slightly larger timeframe so you could capture a couple to make sure you can see all the peaks and make sure they're not being clipped off.

Also, the magnitude (or height of the sign wave) probably won't even show up. You won't be seeing more than 20-60 A/C volts out of the amp and a car ignitions releases a spark with roughly 40,000V.

 

[Stetsom Rep USA 10+ year member]

to find output wrms is very easy. take a dmm set to ac voltage and stab the speaker outputs + & - and put a ac amperage clamp meter on the + speaker output. If you have peak and hold meters set to peak and hold if not get one person to look at each meter and write down the highest values that they see.

Set headunit to frequency and do a burp. 3 sec or better. now take the numbers that you recorded and do below formulas

ac voltage times ac amperage = wrms

ac voltage divided by ac amperage = impedience rise

very simple test and will show what you are getting out of the amp.....any amp.....