Setting Sensitivity with DMM

[billyrohm]

When setting the sensitivity with DMM and playing 60Hz tone should the crossovers on the amp(ZX475Ti) set to Full range or does it matter??

[fordtough1]

I always set them with the crossovers where they were going to be. When I used a zx475, I had the fron channels high pass and the rear lowpass, and set the gains with them like that.

I could be doing it wrong though.

[eyesofra]

i did it that way too ... though i tried out with lower freq test tones
( 40Hz,45Hz,50Hz,55Hz ) for the sub amp with bass boost at lowest and SSF at lowest and left that way.

I was cutting off LP at 75Hz and i thought if i were to use a 60Hz test tone ,then the DMM would certainly depict a smaller output voltage from the amp due to the proximity of the test tone freq to the xover point since the output voltage gradually drops as it reaches a particular xover point.

widening the gab between these 2 freq points i believe gives a more reliable voltage reading for a more accurate output setting with DMM across the wanted freq band.

but as the guys have pointed out earlier, a regular DMM works better at 60Hz since its calibrated to that freq or something ..... unless u can get a true RMS DMM which supposed to work well on all freq, as i did. ..

[stipud]

I always set them with the crossovers where they were going to be. When I used a zx475, I had the fron channels high pass and the rear lowpass, and set the gains with them like that.

I could be doing it wrong though.

If your front channels are high passed above 60Hz, they will remove the 60Hz signal, and your voltage readings will be super low. This will cause your gains to be really high.

You could use lowpass if > 60Hz, or high pass if < 60Hz, but it's easier to just disable the crossover.

[billyrohm]

I always set them with the crossovers where they were going to be. When I used a zx475, I had the fron channels high pass and the rear lowpass, and set the gains with them like that.

I could be doing it wrong though.

If your front channels are high passed above 60Hz, they will remove the 60Hz signal, and your voltage readings will be super low. This will cause your gains to be really high.

You could use lowpass if > 60Hz, or high pass if < 60Hz, but it's easier to just disable the crossover.

So I just do the dmm setting at 60Hz for both front(will be high pass) and rear(will be low pass) with the crossovers disabled and after that I can turn the crossovers on to whatever frequency I desire and the sensitivity should be set correctly?

[stipud]

So I just do the dmm setting at 60Hz for both front(will be high pass) and rear(will be low pass) with the crossovers disabled and after that I can turn the crossovers on to whatever frequency I desire and the sensitivity should be set correctly?

That's right.

[fordtough1]

I always set them with the crossovers where they were going to be. When I used a zx475, I had the fron channels high pass and the rear lowpass, and set the gains with them like that.

I could be doing it wrong though.

If your front channels are high passed above 60Hz, they will remove the 60Hz signal, and your voltage readings will be super low. This will cause your gains to be really high.

You could use lowpass if > 60Hz, or high pass if < 60Hz, but it's easier to just disable the crossover.

Wow, for some reason that never occured to me.

Thanks Tom, I need to go reset my gains....

[billyrohm]

Something else, I'm using the Mtx Re-Q, it has a subsonic filter which has a range of 10-40hz, what should this be set to when setting the sensitivity?

[dedlyjedly]

I would disable the subsonic filter or minimize it's impact (turn it as low as possible) on the audio signal before setting the gains.

If your front channels are high passed above 60Hz, they will remove the 60Hz signal, and your voltage readings will be super low. This will cause your gains to be really high.

You could use lowpass if > 60Hz, or high pass if < 60Hz, but it's easier to just disable the crossover.

I learned to disable all crossovers and processing when using a dmm to set your gains, but I can definitely understand your logic about the LP above 60Hz Tom. Taking that logic one step further though...if you're using a true rms meter for this process you wouldn't want any crossovers enabled as it would affect the rms reading wouldn't it? Just thinking out loud here...

[billyrohm]

The Re-Q has no on/off for the subsonic filter, just an adjustment, and I cant just set it with the full range side and then switch because the sub side of the Re-Q has a higher output voltage.

Any other ideas?

[dedlyjedly]

Like I said if you can't disable it then minimize it's impact. Turn the subsonic to 10Hz or as low as it goes.

[stipud]

Taking that logic one step further though...if you're using a true rms meter for this process you wouldn't want any crossovers enabled as it would affect the rms reading wouldn't it? Just thinking out loud here...

If you had a true RMS meter you could just measure at a different frequency. So if you set your crossover to 100Hz highpass you could still test it at 1kHz with no issues using a true-RMS meter. But if you now measured it at 90Hz you would detect lower voltage.

Basically you just have to measure a frequency above your highpass filters, or below your lowpass filters, in order to get an accurate reading. Anywhere below the highpass or above the lowpass will roll off, thus giving you a lower voltage reading.

[GaryJ]

Edit- sorry, didn't see the howto section. I think I figured out the answers to my questions below.

OK, would someone mind explaining this process in a little more detail to a noob? I have a voltmeter and I think I saw in another thread that you can download a mp3 of a 60Hz tone. But how exactly do you know how much voltage you should have? Do you just put the leads on the speaker outputs? Probably simple enough...but please have patience.

FWIW, the amps are X200.2s