gain setting for .5 ohm?? Dont wanna blow this new amp!!

[CoilBurner]

I have a Mb quart 1500 rated for 1500rms @ 1ohm. I want to run it at .5ohm. My subwoofer is a Dual 1 voice coil

Can anyone help me out at what voltage and the math behind it for how I would set my gains for .5 ohm??

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[ltr450racer690 10+ year member]

what electrical do you have?

 

[CoilBurner]

200 amp alt, 3 big batts, electrical is fine

 

[ltr450racer690 10+ year member]

i would think your good. i ran mine gain at half at max when i ran my dsc1500 at .5 ohm

 

[Plottin4success 10+ year member]

Most people here just set the gains by ear.

But here is a tutorial on how to set it with a DMM...

Setting gains with a DMM.. - Car Audio Classifieds

 

[CoilBurner]

Well, I figured someone could teach me the mah and I could actually put a dmm on the terminals and actually make this work instead of always guessing

I just dont get how to set it for .5 as thats not on any of the carts

 

[bubbagumper6 5,000+ posts]

Well, I figured someone could teach me the mah and I could actually put a dmm on the terminals and actually make this work instead of always guessing
I just dont get how to set it for .5 as thats not on any of the carts

Well that's the problem with running equipment below it's rated impedance, you have no numbers to go buy...which is why it's generally reserved for those with advanced knowledge...Without some benchtest data, the best you can do is set it for 1500w because you know it will output at least that. The formula for that is: sqrt(rms*impedance)

So in your case the best you could do would be: sqrt (1500*0.5) = 27.4V

 

[dB-r 10+ year member]

You can't set gains with a DMM. Impedance rise..... Why DMM Gain setting tutorial? it just drives me crazy. If your subwoofer is wired at 1 ohm once it starts moving it goes to anywhere from 2-9 ohms changes with frequency so how can you possible get anywhere close with a DMM to whatever power level you want if the numbers are going to be WAAAY off... Sorry for ranting, this crap drives me crazy. BUY A CLAMP METER AND A DMM, THEN set your gains so you KNOW what actual power is going to the woofer. You cannot possibly even get close without a clamp and a DMM....

 

[CoilBurner]

The formula for that is: sqrt(rms*impedance)
So in your case the best you could do would be: sqrt (1500*0.5) = 27.4V

isnt the formula sqrt (rms/impedance)

Rms divided by impedance.... in which case I get 54.77

I was just doing some research and came across that formula then came back to this thread to your formula, and there obviously a bit different lol

I get 54.77

 

[CoilBurner]

You can't set gains with a DMM. Impedance rise..... Why DMM Gain setting tutorial? it just drives me crazy. If your subwoofer is wired at 1 ohm once it starts moving it goes to anywhere from 2-9 ohms changes with frequency so how can you possible get anywhere close with a DMM to whatever power level you want if the numbers are going to be WAAAY off... Sorry for ranting, this crap drives me crazy. BUY A CLAMP METER AND A DMM, THEN set your gains so you KNOW what actual power is going to the woofer. You cannot possibly even get close without a clamp and a DMM....

Im wired to .5 But expect to rise to 1ohm so Ill set it for that, Close enough for a budget daily setup with no money for anyhting other than this dmm

But Id love some clarification on the formulas, as Im unsure which is correct

 

[skmfkr 5,000+ posts]

You can't set gains with a DMM. Impedance rise..... Why DMM Gain setting tutorial? it just drives me crazy. If your subwoofer is wired at 1 ohm once it starts moving it goes to anywhere from 2-9 ohms changes with frequency so how can you possible get anywhere close with a DMM to whatever power level you want if the numbers are going to be WAAAY off... Sorry for ranting, this crap drives me crazy. BUY A CLAMP METER AND A DMM, THEN set your gains so you KNOW what actual power is going to the woofer. You cannot possibly even get close without a clamp and a DMM....

or just buy an oscope that would be cheaper. but if it were me i would rather get a fluke true rms clamp so i can test actual output. amazon has them for like $210

 

[CoilBurner]

I wont be spending a small fortune on equipment to set gains on an amp worth less than the measuring tool lol.

I just am looking for a proper formula, as we have some confusion

No need to stray away from the topic, its my only question

 

[Brian Owens 10+ year member]

You can't set gains with a DMM. Impedance rise..... Why DMM Gain setting tutorial? it just drives me crazy. If your subwoofer is wired at 1 ohm once it starts moving it goes to anywhere from 2-9 ohms changes with frequency so how can you possible get anywhere close with a DMM to whatever power level you want if the numbers are going to be WAAAY off... Sorry for ranting, this crap drives me crazy. BUY A CLAMP METER AND A DMM, THEN set your gains so you KNOW what actual power is going to the woofer. You cannot possibly even get close without a clamp and a DMM....

But even that can be hard for a newbie, since you have to determine the impedance at the frequency you set at and make sure everything is correct. . .

By this I mean if you set the gain at say 40 Hz and the actual impedance is 3.4 ohms at 40 Hz, you need to set it so the power is what the amp produces at 3.4 ohms. Some people will just clamp, play a tone, and then turn the gain until they have the output at the sub's nominal impedance. Just as bad as setting with only a DMM.

I set by ear, but use a DMM to make sure all amps are very close.

Brian

 

[l7runner 10+ year member]

or just buy an oscope that would be cheaper. but if it were me i would rather get a fluke true rms clamp so i can test actual output. amazon has them for like $210

Oscope cheaper than a clamp meter?

 

[CoilBurner]

So nobody knows the correct forumla??? he 2 posted give WAY different resualts...