DMM method not working

[blackink 10+ year member]

Hey guys I recently put in 2 15' dc xls dual 2 powered by an audiopipe 30001d which gives 3000 watts rms at 2 ohms. I did the dmm voltage calculation and ended up with 77.475 volts.

I left the car on and disconnected the subs from the amp and put the dmm wires into the speaker terminals. On the HU (alpine 9887) I put sub level on 15/15 and I had the bass knob all the way up which is different than the bass boost on the amp. I left the bass boost at 0 and put the master volume at 26/35 while playing a 50hz test tone at 0 db. It ****** since my door speakers were blaring this awful tone (don't know how to disconnect them) while I was trying to get the correct voltage.

When I put the gain to about 3/5 I hit 72 volts and from then on it didn't change at all even with the gain maxed out. I am off by several points and I have no idea what to do. I got frustrated and tried detecting it by ear playing music but the amp went into protect for a couple seconds when I put the gain up really high.

What am I doing wrong here? Prior to this my friend set the gains by having the max volume on the HU as 20/35 with the sub volume 5/15 and the bass knob up 1/2 and bass boost up 3 dbs with the gain about halfway. It sounded good but I wanted to set the gains "properly" and now there's a bunch of stuff going on that I don't know how to interpret.

Help please!

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[helotaxi 5,000+ posts]

You have found the capability of your amp. It will only do 2500ish watts. Back the gain down until the voltage drops, then turn it back up to the lowest setting that gives you the max voltage. You are using an RMS multimeter, correct?

 

[blackink 10+ year member]

Is the max output voltage determined also by the cars electrical capability? Would adding another battery help it?

 

[stangman67 10+ year member]

I've had issues with this method too. Not completely accurate. Setting my amp to deliver 2k at .5 ohm leads to almost no power whatsoever. I just do it by ear/o scope at this point

 

[n2caraudio 10+ year member]

Set it by ear, cause to set it with a dmm and no o-scope, is a guess at best anyway. I would also recommend that you filter the low's out of your mids and highs.

 

[Haunz 10+ year member]

Hey guys I recently put in 2 15' dc xls dual 2 powered by an audiopipe 30001d which gives 3000 watts rms at 2 ohms. I did the dmm voltage calculation and ended up with 77.475 volts.
I left the car on and disconnected the subs from the amp and put the dmm wires into the speaker terminals.

Son, your testing methodology is way out of wack... unfortunatly there is a lot of misinformation/stupidity on the web when it comes to setting gains with a DMM which is probably where your faully began...

Preferably, you should be using a true RMS meter.. but if you don't have one its still more or less OK... second, you should be using a test tone, not music, which I presume is what you were using... 60Hz sine wave should be perfect, especially if you don't have a true RMS meter...

Last... YOU WANT A LOAD CONNECTED TO THE AMP... I'm not sure what idiot first suggested you should disconnect the subs, but they did not know what they were talking about.. ideally you should use a dummy load.. otherwise at least leave the subs hooked up..

This is all neither here nor there as to how a sub stage should be setup if SQ is the goal....

 

[stangman67 10+ year member]

Obviously sq isn't the goal with 2 15's and 3k

 

[blackink 10+ year member]

Son, your testing methodology is way out of wack... unfortunatly there is a lot of misinformation/stupidity on the web when it comes to setting gains with a DMM which is probably where your faully began...
Preferably, you should be using a true RMS meter.. but if you don't have one its still more or less OK... second, you should be using a test tone, not music, which I presume is what you were using... 60Hz sine wave should be perfect, especially if you don't have a true RMS meter...

Last... YOU WANT A LOAD CONNECTED TO THE AMP... I'm not sure what idiot first suggested you should disconnect the subs, but they did not know what they were talking about.. ideally you should use a dummy load.. otherwise at least leave the subs hooked up..

This is all neither here nor there as to how a sub stage should be setup if SQ is the goal....

This is not the proper way to set gains? I read the gain settings tutorial that is stickied and this seems to be the default and accepted method for gain setting. I don't have an rms meter but I have a 50hz test tone 0 db on my ipod that I can use. Do I just keep turning the gain up until I hear "distortion?" I did this but with music and the amp went into protect mode.

 

[SpeedEuphoria 10+ year member]

well you could be dropping voltage or your ear is not very good

 

[smoka 10+ year member]

Is the max output voltage determined also by the cars electrical capability? Would adding another battery help it?

Yes, most car amps use an unregulated power supply. That means the lower the volts in = lower volts out.

Your voltage is probably dropping too low, its not a good idea trying to run 3kw without at least adding a second batt (maybe even a bigger alt).

Also that amp can't get near 3kw.

 

[hatedonmostly 5,000+ posts]

in a nutshell:

-dmm to set gain fails

-set all eq options to 0

-turn gain on amp all the way down

-set hu volume to 75% of maximum

-turn gain up until you reach distortion, then turn the gain down

-in your case, i would measure your voltage at the amp and only turn the gain up to a point where your voltage stays about 12.5v

also, are you really trying to use a 3k amp with no electrical upgrades and you have a stock front stage? i'm assuming, since your amp is going into protect constantly. fucking fail...