Car Stereos: amp settings, sony xplod, amp settings

Question
ok i have two sony xplod twelves 4ohm bridged together running to a 1200w 1ohm stable mono block amp. i kind of have two questions. why when the speakers are bridged do i not get a stable ohm reading on my mutimeter? it jumps between 1ohm - 2.7ohms @ the amp. also im losing low and gaining distortion on high volume. sounds very good at mid volume. is there a universal way to adjust my settings that should help with this? mabie a good round about operating range for these particular speakers? i really appriciate your time and knowledge. thanks  -nick-

Answer
Hi Nick,

Do you have the subs hooked up in parallel or in series?  If in parallel, 2 4ohm coils will produce 2ohm of impedance.  If they're in series, you're looking at 8ohm.  Either way should be fine with your amp since it's 1ohm stable.  To properly get a read of the speakers, you should have them disconnected from the amp before trying to get a read, or you're going to get weird reads because it'll also test the impedance of the terminals on the amp.

Now, if they're 12" subs, they should be on a low-pass filter and only reproducing frequencies that are low, and not in the 'mid' or 'high' range.  Typically, you would set up a LPF for the subs, and only set the gain as high as it can go without picking up interference off of the inputs (typically not very high at all), and then control the volume at the deck.

Remember, a 1ohm stable amp means it can safely run with 1ohm impedance going out of it, but it will be perfectly OK if you run it at a higher impedance than that, (but will not be OK to run it lower, say .5ohm.)

Hope this helps,
Justin