Speaker Impedance Question.....

HoseHead · Post by **HoseHead** » Mon Jan 08, 2007 11:01 am

What method can be used to accurately measure the impedance of a speaker array? I have qty 3 XMax12 in a single sealed enclosure and would like to know how the builder wired them together to the single L/R binding posts on the cabinet.

I know, I can always pop off an XMax and have a peek, but they work great and if I don't need to dick with 'em.......

Comments? Suggestions? I have meters, both analogue and digital. Thanks.

HH

My ride's garaged for the season. Adding a few components and SQ tweaking the system.

Post by **stipud** » Mon Jan 08, 2007 11:09 am

Just look at the Re of the speaker (DC resistance) in the manual. IIRC the Xmax are really close to 3 ohms if you measure their resistance with a multimeter. This means if your 3 SVCs are in parallel you should be showing 1 ohm mono, or if they are in series it will be ~9 ohms.

HoseHead · Post by **HoseHead** » Mon Jan 08, 2007 11:31 am

OK.

Manual indicates Re of 3.89 ohms per unit.
I measure .9 - 1 ohm across the binding posts using a Fluke DMM.
I'm wired in parallel.

I'm driving these with a bridged MS2125.
PG doesn't rate this amp into a single ohm. (510 WRMS into 2 ohms @ 13.4VDC)
Am I safe?

HH

1moreamp · Post by **1moreamp** » Mon Jan 08, 2007 11:47 am

If your sane it will work fine, BUT if you decide to get way out there, PG built current limit resistor fuses into the amp at the outputs. Unfortunatly they could not do the same at the power supply fets and they will flash very well as I recently saw in SLC's 2125.
Try lowering the main fuses for safety... just a thought, better safe than sorry ya know

Fuses cost alot less than a rebuild / repair...

Post by **stipud** » Mon Jan 08, 2007 11:51 am

Your impedance as I worried is definitely on the low side (1.33 ohm nominal, with 3 4 ohm woofers in parallel). Unfortunately with your woofers, getting an optimal load isn't really possible. You "could" run them all in series at 12 ohms, but that would give you next to no output.

It's been working for so long... so you should be OK as long as you go stupidly easy on the gains and baby your system. Running three subs off of that amp, you should ideally have DVC 4 ohm or SVC 8 ohm woofers, for a 2.66 nominal load.

HoseHead · Post by **HoseHead** » Mon Jan 08, 2007 10:01 pm

Thanks guys. I should be fine. I will drop the internal fusing from 60A to 40A though. Great idea.

After sequential level sets through 5 signal processing devices, the MS2125 gain pot is at 50% rotation.

Alpine HU
AC Four1.i
AC Epicenter
AC ESP2
PG 406A

If I rotate the Master volume on the Four1 beyond 30%, I couldn't sit in the car!! It would be painful listening any louder than that. I'm SQ and I'm old. Powerful and clean across all volumes is the objective. We're really close now......

Thanks again for the responses.

HH

1moreamp · Post by **1moreamp** » Mon Jan 08, 2007 10:12 pm

50.s might work abit better, try 40's first and check for SAG of the element after you do some banging for a week. If it has sagged or shows signs of heat stress then go 50's. But stay away from the full rated fuse size and the biggest expense you should ever see is a pack of fuses.

I like my work, but my best work is when I don't have to repair your amp. Then I have done my best work.