I'm a little curious about bridging 4 channel amps, to achieve 2 Mono channels,
in regards to attempting to achieve better stereo separation,

What I'm wondering is, is the stereo separation between the say channels 1/2 and 3/4 Completely separated (IE: is it 100% separation like 2 separate amps would be) or is the sepation between these channels no better than say between Left and right channels.

I guess what I'm getting at, I'm looking at ways to improve my stereo separation,
and trying to decide if I need a million separate amps, or can I get away with a couple of bridged 4 channels.

I've noticed that most amps do not have as good a stereo separation as the input signal, I realise the amps I have do have Extremely good stereo separation but I'm trying to find just that bit more. The downside is my PXA-H701 is only 80db separation.. (where my 9965 would be 90db if i used it's outputs) I'm hoping to tweek out every bit of that 80db separation that i can.

I've run through a test disk with up to Negative 80db test signals which can still be heard in my system..
I'm getting to the point of squeezing every last 0.1% of performance I can out of my system.
so that seemingly unimportant few DB's of separation are important to me.

any ideas on the 4ch vs 2 separate amps thing?

Juls

Depends entirely on the amp design.
You want pure seperation? Run a Mono amp for each channel.
There are however many dual mono amps out there, as well as "dual stereo" amps (4 channel amps with 2 discrete stereo sides).

Can you actually hear any overlap between left.right?

I notice that you're running semi-active so to speak.
Have you considered running 1 amp for left side, and the other amp for the right side?
Each side would then be "seperated".

Regardless, I doubt you could hear the difference when the engine is turned on.
And -80db down when music is playing, unless the music is coming purely out of 1 channel, would not be noticable.

i get good seperation from my amp but it's old and designed to be a good SQ amp, no compremises.
insted of getting 2 x 4 channles wouldent it be easier to get 2 x dual monos?

I've bridged up my 500.4 into my Mid/tweet before, and I'm sure the stereo image is clearer, more precise than when I run a 800.2 into the mid/tweet.

Admittedly it goes from 200W to 500W a side, but the reality is that my mid/tweet is really only using maybe 50W-100W a side max anyway regardless of the available power. So I don't believe the power difference is whats making my stereo imaging clearer.

I was considering using 2 4 channels, bridged, one power side, IE 1 amp for midbass, midtweet per side.
I don't believe using a 2 channel in that manner would work, since the stereo separation could cause bleeding of the separated signals. I guess what I'm wondering is if my Van gogh 4 channels bridged up, and used as 2 channels in this manner would cause me a issue.

Sounds like more trial and error to me.
Figured I'd see what other people think before trying.

Juls




I've got my hands on Good Quality 4 channels already.
if I want to go to Dual monos of equivalent quality/power/performance, I'm looking at $3k each.. dammit.

I guess basically I can't see the point of going to something like a F1 Processor with 90db separation before making sure the rest of the system is keeping up it's end of the bargain also.

Juls

im changing to 4 x 2 channels (all bridged to mono) to run my front stage for the CAASQ finals
ill see how the seperation go's with that

LOL I'm sure that will be awesome,
I can't imagine how good that would be with a input of 95db separation!... that'd be sweet!!

oh well we can dream..

Seperation at such extreme levels wont be directly noticeable. You wont be hearing something out of the left channel and think 'now what a sec, thats in the wrong channel'. It will simply firm up your imaging and staging. The difference between 85dB and 95dB in seperation is 3/5 of fck all. Removing it altogether? The best option. Like Fudd, Im planning on having an amp per side. Though mine wont be bridged, and I wont be running active Im hoping with a Brax/Helix, it should be alright!!

Juls, you have 2x4-channels right? Go for one channel for tweet, one for mid and one bridged for midbass. One amp per side. Heaps better Seperation then relying on amp stats.

And dont forget, bridging will halve your damping factor and increase your THD+noise. Both should be supposedly un-noticeable, but then again so will the seperation!!

EDIT!!

I just did some research and it turns out your right,

this gives me some food for thought.

Juls

I always thought that those are impedence dependent too no?
Therefor, running each channel at 2ohms (4ohms bridged) gives you the damping at 2ohms, not 4ohms?

In terms of 2ch vs 4ch seperation...
How are the amps designed?
If the 2ch is a dual mono design, then it should be better then a 4ch dual stereo design (bridging for 2ch operation) due to higher impedence loads (less thd etc...).
If however the 2ch is a stereo design, the 4ch may give better seperation.

Take for example a DLS A3 Dual Mono (i think that's the model).
It has 2 seperate power supplies, and the amp is essentially divided into 2.

Then take my PPI PC4100.
It has one powersupply for all 4 channels.

In terms of the signal path, you have to look more closely at the amps design.

There's a lot more to it which I am learning as I go along, best bet is to search in google and see what results you come up with.

I use 2x 4channel amps, not bridged, for the fronts, and a monoblock for the sub. works great.