Interesting biamping power statement. Comments?

Jack from Indo

I got the two extremely interesting paragraphs below from http://sound.westhost.com/bi-amp.htm#power_dist

Now, basically what they are saying (I think) is that when you biamp, you realize a lot more power from your amps, cause...............

"A passive crossover will separate the two signals shown above and feed each to the appropriate loudspeaker in the system. The amplifier must be capable of handling the entire composite waveform, so for our previous example of 100 Watts for each signal individually, must be capable of 400 Watts to reproduce the waveform without distortion.

If we now we separate these signals again - prior to the power amp - and using an electronic crossover, we have an entirely different situation. (Note: It is assumed for the sake of this article that the crossover frequency is near the halfway point between the two discrete frequencies of Figure 2.) Each signal is now supplied to its own 100W amplifier (there will be but a hint of the other frequency still visible on an oscilloscope, since the filters are not "perfect") and thence to the loudspeakers. The amplifiers are not clipping, both signals are reproduced at their original power, and the effective result is that we are emulating a 400 Watt amp with two 100 Watt units"


I am trying to decide how much powerful an amp I wanna buy tomorrow, to biamp my front comps, rated 100rms.

How much to you guys use? Greg? McLeod? Anybody? The article above makes me think I do not need as much as I think.

Jack from Indo

I should have added that the above came from a home audio article, and the biamping it referred to had the woofers on one amp and the mids and tweets on the second. (this the mids +tweets still used a passive crossover). But the principle should still apply, no?

So anyway, how much power per channel do you biamper's use for your rig? 50? 75? 150? Chime in, please.

PoweredByDodge

it's a pile of 'tom-foolery'.

they want to have their cake and eat it too --- why?

when you measure power (measure voltage with respect to a given load) you have to do so with a certain amount of sense about you. so you ask some questions [and hopefully you come up with the right answers]...

1- do i want to measure 'peak' power, 'peak-to-peak power', or 'average (rms) power' ?
[ measure PEAK -- the average/rms can be derived by simply multiplying the peak power by 0.5 --- but why '0.5' when 'rms' is supposed to be some number multiplied by 0.707? -- because average/rms power is the product of rms voltage (0.707 * V) and rms current (0.707 * I = 0.707*V/R) -- and 0.707 * 0.707 = 0.5 -- peak-to-peak is somewhat useless for the topic at hand, and i'll explain why in a bit.]

2- what do i care about most when i observe the waveform?
[ the absolute value -- which means you take the "S" shaped waveform and make it look like a bunch of McDonalds arches all down the line --- boom, that's why you're peak-to-peak means nothing. peak-to-peak just turned into peak. ]

Anyway -- if you look at the PEAK power value, you'll see that it doesn't 'multiply by 4' -- rather, it simply doubles.

If you've a composite signal consisting of two signals -- one at 100 hertz, another at 500 hertz -- and each signal is at 3 volts-ac-peak (6 volts-ac-peak-to-peak), then you'll have a composite signal at 6 volts-ac-peak with the 500 hertz waveform riding on the 100 hertz carrier. Yes, the peak-to-peak voltage will be 12 volts... and this is, i suppose, how amplifier manufacturers can put crazy labels on their products.

--- Any music that comes out of your amplifier and into your speakers is going to have two parts, a 'push' and a 'pull'; one part pulls the speaker into the box, the other part pushes the speaker out of the box. obviously, this is nothing more than constantly flip-flopping polarity, aka an AC signal. all things being equal, it takes the same amount of power to push the speaker out as it does to pull the speaker in. that being said, you're using X amount of 'positive' power and and equal X amount of 'negative' power. That is probably an ugly way of making the point, but it's the best I can think of at the moment. Keep in mind that you are NOT using both the 'push' and 'pull' at the same time -- if you were the NET power would be ZERO.

--- at any given time, you're instantaneous output is something equal to or less than V-ac-peak ... whether it is positive or negative doesn't matter. Power is power... you're just 'directing' it differently when you 'push' as opposed to 'pull' the speaker.

All of that being said, what are these flakey people trying to prove anyway? Yes, you can split two frequencies. So, if you had a SINGLE NOTE playing on your mids and a SINGLE NOTE playing on your tweeters, then (if they're theory was correct, which it is not) then you would have more dynamic range. Well, you don't play only 2 notes on your speakers. You play an infinite number of notes between around 20 and 20 thousand hertz. So are you going to buy an infinite number of amplifiers and use an infinite number of electronic crossovers, each with its own phase lag and ripple due to filtering?

In reality, what you gain by bi-amping is tune-ability.

You do not gain power, you do not magically pull fairy dust from the sky, and you certainly won't be playing anything louder than it was before.

However, you will have the ability to fine tune and perfect your system to the point where it makes you want to fall in love and marry it.

Jack from Indo

Thanks for that, PBDodge. Makes sense. You said the other day that you preferred gobs of power to excessive tuneability. I want to biamp, and am now using 155w per channel. The amp immediately available to me to do this is the same make and series, but only puts out 80w. I'm just wondering if I will notice a difference in SQ if I use it, or should I go for more. My comps rated at 100.

PoweredByDodge

80 x 4 ? -- well, it depends.

if you get this 80 x 4 amp, and you bi amp, then you can see if the benefits of extra tune-ability outweigh the loss in power.

if they do - then leave it at 80 x 4 bi amped. if they do not, and you want to go with more power, bridge that 80 x 4 down to 320 x 2 (obviously keep the gain almost at zero so that you are only throwing say 200 or so x 2 to your speakers -- 200 is about 25% higher than the 155 you're running now)

so, i think either way you would do allright with this new 80 x 4 amp. if you don't like bi-amping then you'll have tons of power to go for the "louder is better" idea.

that's basically what i have too -- the amp i'm using is 75 x 4 --- i used to use it has part of a tri-amp setup and now i just run it bridged to my front speakers.

just be careful with how much power you're running -- i used to do something like 175 - 200 watts on front speakers that were rated for something like 65 watts (the old polk dx-3065). i blew a couple of tweeters and a couple of mids -- i loved the way it sounded, but i beat hte hell out of the speakers. the fronts i run now are rated at 200 rms per speaker.

MacLeod

Im a tweak-a-holic so I want the absoulte most flexibility in tuning and so bi-amping the best way for me.

PBD is right on in that the only real benefit to bi-amping is superior flexibility in tuning.

PoweredByDodge

mac, what are his fronts?

MacLeod

Focal K2P's if I remember right.

Jack from Indo

Well instead of trading my 155w x 2 I ended keeping it for the mids, and then added a 105x2 for the tweets for about the same total cost as going for the 80w x 4, so there we go I'm all set.

They're putting it in today and tomorrow while I sit here in a cafe surfing the net. Funny, where I live components are a slight bit more expensive sometimes, but installation is free, thankfully. They do pretty good installs, too.

I already know that I want to sit there for hours tuning like McLeod does, cause I get fascinated by having that much control, and learning more about sound. I've gotten to where I'm not really listening to music so much as dicking around with it too much. :eek: :mad:

Thanks y'all