EXM-702 amp+sub+impedence questions?

[predator]

I've got an older (maybe 4-5 year old) Sony EXM-702 amp. Its been in a couple of my cars, and still living strong, but of course, long since lost the instructions.

Can't find anything on the net about it - kinda the series before the xPlode trash. Its a 2x75RMS or designed to be bridgeable into 1x150RMS.

My main question is what impedence is it stable at? The Alpine 12" sub i have can be run at 8ohm or 2ohm depending on how its wired up.

Running at 2ohm it seems to be missing some kick - will i get more kick at 8ohm? Or will i just be overloading the amp?

Does anybody have one of these Sony EXM series older amps (generally they are blue+silver) or remember much about them?? generally what are the older amps rated at impedence wise?

I think it could have possibly been 4ohm stable (but that could be like for the 2 channels)? Would that mean bridged would it be 2ohm stable?? I forget all the maths behind it

[predator]

Getting back to answering my own question (partially) . Would still like some full specs on the amp please if anybody has an idea??

Ok... If the two channels are 4ohm stable (which i suspect).. bridging them into one will probably mean my amp is only 8ohm stable. This won't be good for the amp fully cranking my sub if I have wired up my sub to be a 2ohm load. Oh well, worse that happens is i toast my old amp (hehe) due to trying to run too low impedence speaker.

Most efficent configuration is to match exactly the sub and amp impedence (2ohm amp running 2ohm load). If you drop the speaker impedence to below that recommended you will increase volume, but overload the amp.

Generally for subs: rigged up in parallel you reduce the impedence, and in series increase the impedence. As mine is a dual voicecoil sub it can be rigged up in either configuration on its own, and suited to multiple chaining of subs (although should run fine just as the one). Does that mean if i only run one coil its only running 4ohm ? Can i do that by just wiring to one of the +ve and -ve terminals?

btw for everybody: this site has some good info on wiring up sub configurations and formulas on optimal sub box volume:

http://www.poweracoustik.com/speakerimpedance.htm

Here is another good one on impedence and the like and many other topics:

http://www.electronixwarehouse.com/educati...wer-ratings.htm

[hippy]

keep going pred .. you're doing a good job ... thanks for the sites i'll read it when i wire up my sub

[Al]

Pred. STOP!!!! b4 you blow your amp or your sub.

I don't now much about that particular amp, but from what you stated, i have gathered the following.

The amp is only stable at 4 ohms mono (bridged). Putting 8 ohms is better/safer for the amp but alot of power will be wasted. ie:4 ohms=150Wrms, 8 ohms=75Wrms. Putting a 2 ohms load is overdriving the amp, which causes clipping of sound. During this 'clipping' the voltage outputted by the amp is effectively DC. DC voltages burn voicecoils! thus blowing sub. There sould be a way to wire up the sub to have a 4ohm impedance, find the instruction manual for the sub. Running one voicecoil is not recommended as it has to push/pull the other one, causing more stress.