How to use a DMM to set gains?

[99grandprixGT 5,000+ posts]

when you convince JL of that and have them revise their tutorial, I'll consider it applicable.

ya i was about to say JL says to disconnect your subs!

 

[GlocksRock 10+ year member]

i don't know if i want to send the test tone threw my subs. i accidentally left my speaker amp on when i did and the speakers blew lol.

Were you running your main speakers full range? I would think you would want them crossed over higher than 50 hz. anyway, they shouldn't have been playing notes that low anyway right? Just try it again, but be sure to pull the rcas from your speaker amp.

 

[jdc753 10+ year member]

Why not just use the subs you plan on using in your vehicle for the load?

This is what I was thinking to do for it. Then touch the leads of the DMM to the set screws for the speaker leads or whatever and should be able to pick up what is actually going on. Or I guess just give up on the whole idea and keep on setting them by ear lol.

 

[GlocksRock 10+ year member]

So I guess it really doesn't matter if your amp is seeing a load or not when it comes to setting the gain via dmm. So if you are really worried about it, disconnect the subs, if you don't care, leave them hooked up.

 

[Horsemanwill 10+ year member]

speakers tend to not like pink waves and what not sent to them.

 

[CadillacMatt 10+ year member]

So just to clarify this mess because I'm still a little confused... disconnect the speakers? Thanks n2audio

 

[rod_b 10+ year member]

Disconnect the sub. Anyway, from what I can tell if you plug in say 500w at 4ohms in an amp gain settings calculator, you come up with with 44.7V. If you do 1000W at 2 ohms, it's also 44.7V but the amperage goes up. And same for 2000W at 1ohm...44.7V. So in general, it kinda seems that having no load, while not completely accurate, will get you pretty darn close.

 

[beyap 10+ year member]

what should the lpf set to while i do this on the sub amp?

 

[David12460 10+ year member]

Lets just say the RMS of your woofers is 800 watts together. My amp is good for 1200W RMS @ 1ohm.

Can you take the desired wattage and use for the formula? EX: if you only want to run 800W of clean power?

 

[mcsoul 10+ year member]

Lets just say the RMS of your woofers is 800 watts together. My amp is good for 1200W RMS @ 1ohm.
Can you take the desired wattage and use for the formula? EX: if you only want to run 800W of clean power?

That's right. But it is best to clamp after and see your impedance rise, then recalculate.

 

[microhaxo 10+ year member]

I set it with the speakers off and then once set i measure the volts once they are hooked up, i found that on the 50hz 0db tone i get the exact same voltage as when they weren't hooked up. So it worked out fine for me.

 

[David12460 10+ year member]

That's right. But it is best to clamp after and see your impedance rise, then recalculate.

Can you elaborate a bit? Clamp?

 

[n2audio 5,000+ posts]

Can you elaborate a bit? Clamp?

It's a reference to a current meter.

They have a clamp that goes around the wire and measures the magnetic field to calculate the current flowing in the wire. It's the easiest way to measure high current.

 

[bryce-man 10+ year member]

wipe that load off your face

lol

 

[shaneb 10+ year member]

did you just bump a million day old thread? lol, must be bored.

yea that was in my noobx days...as though i'm not still in them //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif