Axiom Home Page Forums General Discussion Home Theater bi-amping with m80s

If this is correct, it makes John's argument merely one of semantics and fairly misleading, at that.

I agree with him that biamping in the receiver makes no sense, but not because it's drawing from a single power supply. No, it makes no sense because biamping with ANYTHING not including an outboard crossover doesn't really do anything.

It's funny, I never read assigned books, or did my home work as a teen (heck, pre-teen). But I was always studying something. All my teachers told my parents the same thing, "Chris could get straight "A"s if he'd just apply himself." The thing was, grades didn't motivate me, an A meant nothing. I'd rather be learning something which interested me. I'd pick up the Math, or English, or whatever as I needed it (to understand my own experiments*, or when writing stories).

*I invented Trigonometry one summer when I was trying to figure out how to programmatically rotate a camera by only using 3D coordinates of it's location, and where it is looking in space.

Lets break it down how well designed, multi-channel amp with a single power supply differs from a well designed, multi-channel amp with multiple power supplies differ when "bi-amping".

An amp with a single PS can provide X number Watts into any one channel, but divides those Watts between all available channels when more than one is active. If your goal is to put more power into a speaker, it isn't going to happen. You get X/2 Watts at most to each channel when driving two outputs at the same time (so X/2*2 or X).

An amp with multiple PSes can provide X/C Watts into each of it's channels, where X*C is the max it can pull from the outlet. If you bi-amp in this case, you can get X*2 Watts into the speaker.

If you're comparing something like the Axioms A1400-8 and Outlaw's 7700, the numbers work out like this:

A1400-8 driving one channel at max, it's getting 1400 Watts.
A1400-8 driving two channels at max, they're each getting 700 Watts for 1400 Watts total.
A1400-8 driving seven channels at max, they're each getting 200 Watts for 1400 Watts total.

7700 driving one channel at max, it's getting 200 Watts.
7700 driving two channels at max, they're each getting 200 Watts for 400 Watts total.
7700 driving seven channels at max, they're each getting 200 Watts for 1400 Watts total.

Is that making sense?

It makes sense, but it still makes John's argument a red herring.

Also, there's no way a tweeter's going to take 200 watts. It would probably catch fire and melt (hell, a midrange might too), which is my understanding of why bi-amping doesn't double the amount of power to a speaker.

But when "passive bi-amping", you're still using 200 Watts into both ends of the speaker. When driving the tweet/mid their high-pass filter is turning the low frequency signal to heat, and woofer side the low-pass filter is turning the highs to heat.

But you're NEVER using 200W!
Of course, we're in agreement here...

I think, as the unofficial, self-proclaimed, fearless leader of the M60's posse......it's time I chimed in here.
You all, are wrong. The term "bi-amping" when used in reference to the M80's, simply means: two amplifiers. One amp for normal use, and the other amp wired in, so when the first amp overheats, or shuts down.....with the flip of an A-B type switch, the second amp takes over, so no listening time is lost.

M60ti's, M60v2's, and M60v3's, all Rule!

In order to drive our M80's to 80 db's we only need about 1 watt of power. This is what has been explained to me on here, I'm not educated in the math that gives us this figure, so I'm just repeating what I've read. So using the 'water' model from the thread in the 'Technical Questions' forum, I'm picturing the faucet turned on just enough to let 1 watt flow down the pipe to my speaker. Which creates 80db's worth of output, so most people won't be opening that faucet (volume knob) much further than that.

However, if you turn the volume knob on your reciever up 100%, then the faucet is wide open, so if it's a 200 watt amp, then wouldn't there be 200 watts worth of power flowing through the pipe to the speaker?

If not then how could they call it a 200 watt amp?

I didn't completely understand his statement either. Most people won't use 200W, but it's possible some will.

The 1 Watt figure, isn't really math, it's a measurement. Axiom puts 1 Watt of power into the speaker, holds a mic 1 meter away, and sees how loud it is. It's known as the speaker's sensitivity. The M80s actually get 91 dB from 1 Watt.

Alan,

Thanks, but I’m still confused. When I referred earlier to the sine wave input signal I was referring to what you are, the pre-amp output to the “amp”. The “amp”, whether it is an actual physical device or component in the receiver (amplifier or transistor) or if it is working sum of all components is where my confusion lies.

John has stated that a receiver has one power supply and one amplifier. He also states (and so does Chris), that these “transistors” act as gates for current flow to each channel and that share a common “pool” of power which is supplied by the power supply.

I need a block diagram. Anyone know where one might reside on the web?