Setting amp gains with multimeter

[Stingerssx 10+ year member]

Hello all,

I have never been able to set up amp gains with a multimeter.
I've tried many different times, with many different systems, and many different multimeters.

Each time, I can't get above 7 volts. And then sometimes the meter will go into OL (overload).

I'm not sure what I'm doing wrong.

I've followed a bunch of different articles and tutorials and they all say the same thing.
Square root of RMS watts X Ohms.

Earlier today, I went out and tired it again.
I'm using the Rockford Prime 1200.1D and a 2 Ohm load.
800watts X 2 = 1600
the square root of that is 40.

Using a Fluke 88, I've checked the range settings and set for AC volts and in Auto, 300v and 40v I can't get above 7 or so with the gain full up.
So let's pretend that the meter is off by a factor of 10. If I set it at 4 volts, it's like only 1/4 the way up.
This happens every time I try this.
And with every amp, this leaves the gains at only 1/4 way up.

Anybody got any sugestions?



thanks!

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[ThxOne Premium Member]

Hello all,

I have never been able to set up amp gains with a multimeter.
I've tried many different times, with many different systems, and many different multimeters.

Each time, I can't get above 7 volts. And then sometimes the meter will go into OL (overload).

I'm not sure what I'm doing wrong.

I've followed a bunch of different articles and tutorials and they all say the same thing.
Square root of RMS watts X Ohms.

Earlier today, I went out and tired it again.
I'm using the Rockford Prime 1200.1D and a 2 Ohm load.
800watts X 2 = 1600
the square root of that is 40.

Using a Fluke 88, I've checked the range settings and set for AC volts and in Auto, 300v and 40v I can't get above 7 or so with the gain full up.
So let's pretend that the meter is off by a factor of 10. If I set it at 4 volts, it's like only 1/4 the way up.
This happens every time I try this.
And with every amp, this leaves the gains at only 1/4 way up.

Anybody got any sugestions?



thanks!

Try this brother...

Make sure all of your EQ's are flat.
Turn the gain down all the way on that amp.
On that amp turn down the bass boost.
Set the crossover for 80hz or so.
Put some music in your head unit and turn it up as loud as you will listen to it.
Turn up the gain until it sounds good with no distortion.

At 2 ohms that amp does not output 1200w. I am currently using that amp on a single 10" sub at 2 ohms.

Follow this link if you still want to use the Fluke.

Ohms Law Calculator

Ohm's law calculator online: calculates voltage / current / resistance / power. Ohms law calculator

www.rapidtables.com

 

[ThxOne Premium Member]

If you are using a sub crossover in your head unit... make it full range or higher than the one on the amp.

 

[Stingerssx 10+ year member]

Ok, let me give a little more insight, which I probably should have in the first place.

My daily driver is a 2012 Accord, premium sound, both mics disconnected, and stock head unit. I converted the balanced outputs before the stock amp to RCAs and they go to an Audio Control EQS, which is an EQ, but not a crossover. Then the sub channel goes to an epicenter, and to the Rockford. It powers 2 12" K6 Rockvilles in a gigantic Q power ported box.
The mids and highs go from the EQS to a PPI 900.4 and then to 6.5" Infinity Reference coaxials in the rear and 6.5" Reference components in the front.

I'm using the crossovers in both amps. I've only set the crossovers by ear, but I wanted to use the multimeter to do it right.

I have tried to set the gains by ear, and I can with the mids and highs, so then I try to balance the subs with the rest.
Mids and highs are set about 1/4 to 1/3 up. This keeps the distortion down at full volume.

Earlier, I tried a lot of different things. Bass in the HU all the way down, sub in the HU all the way down, bass knob for the Fosgate all the way down, cross over all the way down. Still the same.
Then everything all the way up. Then everything half way.
I've been through this for years. Trying every way possible, and still the same results.
I have 3 other cars right now with systems, and still the same thing happens with all systems. I've tried this on previous systems for the past 20 years! Same results with the DMM.


I've really had a hard time with this system. I can't replace the stock head unit, because it is connected into the car's ECU. It has all the displays and all. I've gone back and forth on what I really need, and how I can just go from my Bluetooth adapter to the EQS, but I haven't pulled the trigger yet.

Mainly, the bass just isn't right. I've had 4 different setups in the car. A 10" Solobaric L7 in both a sealed and ported boxes. 2 10" in a sealed box, (which sounded AWESOME in the two other cars I've put it into) and 2 other 12" Hifonics, in a sealed box.
I first was using a Hifonics Boltar XI, then I went to the Fosgate. I know it doesn't put out 1200 watts at 2 Ohms, but it does put out 800 watts at 2 Ohms.
If I'm sitting in my driveway, with the doors open and the trunk open, it sounds pretty good. But when I close my trunk, the bass just changes. Back seat up or down, makes no difference. And when I'm driving, it gets worse. It's really hard to explain.
Sometimes when the lower bass hits, everything in the car shakes, but the sound is not loud at all. It's really weird.
And some songs, just really don't hit, where others really do.
If I play the same song, either from my phone, or from the same flash drive, it sounds WAY better on another system. In another car, or on different home theater systems. Even headphones!
I'll try to find a song for an example.
Ok, Black Widow from Iggy Azalea has two bass lines an octave apart. The lower one hits really good, the higher one hits good in the 6.5"s, but not the subs. And this is with the crossover on the Fosgate all the way up! other systems both notes hit in the sub.

This is why I go the Epicenter. I thought that it would help out with the bass limiting from the HU. The epicenter, well, that's another story. So I basically only use that for rock that has almost no bass at all.

So I thought I'd check my gains to see if that'll help, and here we are.....

 

[THATpurpleKUSH 5,000+ posts]

Sounds like a weak signal and install related cancellation issues. The signal problems always happen when people have a stock headunit.

If you can't replace the stock headunit then bypass using it for audio and run your audio input to a dsp.