Setting gain on strapped amps?

[JZeFF]

I have a pair of SAZ 1500d's strapped pushing an 18" nightshade at 2 ohms.

I understand i need to set my gain AC voltage to 77v, but i do not understand where i put the probes from the DMM.

I know i only need to set the master gain since the slave takes all settings from the master.

Like i said, the only thing i dont understand is where i put the Positive and Negative DMM probes.

Do i put the positive probe in the positive master output, and the negative probe in the positive slave output?

Or do i unstrap the amps and then set the gain normally on the master?

Hopefully someone can answer this for me, i dont wanna be clipping anything!

Thanks

Edited April 21, 2011 by JZeFF

[JZeFF]

The answer to this is surprisingly hard to find. Can anyone help?

[Superjay]

positive and negative output terminals

EDIT: let me clarify, since you're having trouble...use the output terminals going to the speaker. so positive will be the wire coming from the master, negative will be the wire coming from the slave...(it's AC so it doesn't matter which DMM probe goes to which terminal)...set your gain with a test tone ONLY. I use 100Hz when bench testing amps, but you should use your resonant frequency, then run a SLOW sweep to make sure you don't jump to clipping at any particular frequency...when you run your sweep put the DMM on MAX HOLD.

Edited April 22, 2011 by Superjay

[JZeFF]

Thanks! I understand how to do all of that, my only issue is that I do not know the resonant frequency of my vehicle, and I do not have access to a TL.

Also, I was using a 50hz tone, is there any reason you recommend using 100?

Also, when unhooking the sub from the amp is it okay to only unhook the positive from the master amp? I know it's not generally necessary to unhook, but I don't wanna let anyone in my neighborhood know that I have a system.

Edited April 22, 2011 by JZeFF

[Superjay]

I always used a 100hz tone because that's what CEA required we rate amplifiers at. RMS ratings are at 100hz or 1000Hz, depending on the class and if they are labelled "subwoofer amplifier" or "full range" or however each company chooses to name them. "Monoblock" amps may be rated at 100Hz, even if they are technically full range (full range go to 20kHz, a sub only amp does not)

[Dj_Scarface]

I know you didn't search the forums cause I foud these videos... But these videos might help:

[JZeFF]

I did come across that second video yesterday when i was attempting to do it, and i wasnt able to get anywhere near my target of 77v without my sub bottoming out.

So i figured i was doing something wrong.

I would rather be safe and ask instead of possibly blowing 2 amp and a sub.

Thanks for helping though.

Edited April 22, 2011 by JZeFF

[Superjay]

maybe your sub can't handle that much power.

at what impedance are you supposed to be getting 77v?

[JZeFF]

The sub is a D1 and i have it run in series, so i was setting the amps for 2 ohms.

Is that correct?

Its a 3" aluminum voice coil, so it should be fine...

But i have actually been thinking that i may change to a lvl 5

[Superjay]

can that sub handle 3000 watts?

77^2 = 5929

5929/2 = 2964.5 watts at measured frequency.