Measuring rms watts.

[jrwalte 10+ year member]

Most DMM gain setting tutorials have you use the desired wattage you want (say your speaker RMS is 500 watts so you go with 500) and the basic final ohm load. You use those two to calculate what the voltage would be and then set your gain with a 40 or 50Hz tone to that voltage. But since music is so dynamic with transients, recording volume, etc, it is argued this isn't the best way to set a gain, which I agree with.

 

[CadillacMatt 10+ year member]

Most DMM gain setting tutorials have you use the desired wattage you want (say your speaker RMS is 500 watts so you go with 500) and the basic final ohm load. You use those two to calculate what the voltage would be and then set your gain with a 40 or 50Hz tone to that voltage. But since music is so dynamic with transients, recording volume, etc, it is argued this isn't the best way to set a gain, which I agree with.

I know, as I posted in another thread I set the "target voltage" for my amp/subs using a DMM, and the output absolutely sucked. I turned the Loudness up on my HU and the sound improved much, and I don't hear any distortion or anything so I'm really skeptical about how accurate the whole DMM thing is.

 

[skittlesRgood 10+ year member]

Most DMM gain setting tutorials have you use the desired wattage you want (say your speaker RMS is 500 watts so you go with 500) and the basic final ohm load. You use those two to calculate what the voltage would be and then set your gain with a 40 or 50Hz tone to that voltage. But since music is so dynamic with transients, recording volume, etc, it is argued this isn't the best way to set a gain, which I agree with.

so what IS the best way? write a tutorial.

 

[jrwalte 10+ year member]

There are tutorials out there. Search. It's limited to an extent, though, because it mostly comes down to 'by ear'. You need to listen to when your sub begins to distort when listening to your most common music and turn the gain down slightly from there. You also need to level the output to what your mid/highs can handle if you want sound quality.

You'll never find 1 good spot, either. Music is dynamic and different songs can handle a different gain. I'm constantly slightly adjusting mine. Thankfully I have a HU that makes it easy and it's within 1 button push on my steering wheel.

 

[mokedaddy 5,000+ posts]

I know, as I posted in another thread I set the "target voltage" for my amp/subs using a DMM, and the output absolutely sucked. I turned the Loudness up on my HU and the sound improved much, and I don't hear any distortion or anything so I'm really skeptical about how accurate the whole DMM thing is.

It depends on definition of 'accurate' is. Yes it will be set it to a certain wattage at a certain frequency but does that mean its going to sound good or be level matched? Not even close. There are many more important factors when tuning a system than 'power' ratings.

so what IS the best way? write a tutorial.

By ear is the only way IMO.

 

[williambrea 10+ year member]

find somebody with a oscilloscope, attach the pos and neg to the speaker outputs, have speaker disconnected. Turn HU volume to 3/4 and set boosts to your liking. Look at the scope start with the gain all the way up and turn it down until your 60 hertz tone ect is not clipped off at the top. Check other frequencies every 10 hertz to make it perfect ie 50, 40,30,20 hertz

 

[I like FI 10+ year member]

You guys are talking about gain setting?

What i need to fing out is ac amps and ac volts at 35 or 40 hz. That way i can find out what it is putting out at that hz. And find out imp rise.

most clamp on meters are 50/60 hz. but there is a way to measure lower hz.

 

[I like FI 10+ year member]

cant afford fluke 336 so im gona have to harass electricians.

 

[edzy 10+ year member]

you need a scope and diffrent load resisters to bench an amp for rms.

A ghetto way is to clamp the power or ground and see what the DC amprage is and the voltage is at the same time, then multiply and subract like 15-20 %

Make sure your DMM can take high DC Amp readings. Usually only $100 models and above that have that feature. Most only do like 6-12 dc amps.

 

[I like FI 10+ year member]

no , i need a quality clamp meter, they cost 250 and up and a dmm to get a 35hz or 40 hz reading. ive done my search already.