Axiom Home Page Forums General Discussion Technical Questions Bi-amp question

When biamping as in the picture, for example where you are using the SL to drive the woofer section of the speaker and using the FL to drive the tweeter section (all channels driven, 200W into 8Ohms) are you actually driving the speaker with 400W?

Thanks.

Nope. Partially because if you were putting 400 watts of signal to a speaker, it would be really, really, really loud. But mostly because it doesn't work that way electrically. I'm sure someone who actually understands that bit will be along to explain shortly...

You are not able to add the power of both channels together to achieve 400 watts, you are simply driving each section of the speaker with 200watts, this makes it better for the low frequncies, as you have a full 200W available to the woofers instead of a portion of the 200Watts when single amped, other than that there is no advantage.

Conversely, wouldn't you be wasting almost all of the 200 watts going solely to the tweeter? I can't even imagine what level of volume would possibly ever require that much power solely when driving a tweeter... (but this isn't my area of expertise either).

Jason

Thing is, that kind of power isn't used if it's not used, ya know? If you're playing something that requires .5 watts of power, it's putting out .5 watts of power, whether the amp's rated at 20 watts or 2000. And, at least according to certain people around here, .5-1W of power puts out about 70-80dB (he says, pulling numbers out of his ear...)

Without an electronic crossover to separate the woofy parts of the signal from the tweety parts I don't think you get any real benefit at all (other than lots of cool points). Since both the woofy and tweety amplifier channels are getting the same signal as before they are going to clip at roughly the same volume setting as before.

Now, if you were running 4 ohm speakers and the amp hit current limits before voltage limits (which is not unusual AFAIK) then (a) you could run at slightly higher volume levels before clipping and (b) you could, to a certain extent, clip without guilt because the harmonics from clipping would only go into the woofer not the tweeter, so not only would you not hear them as much but they wouldn't be able to damage your tweeter since it would be the woofy side of the amp clipping.

Back when I used to play with professional sound systems (and I stress the word "play" ;)) I remember the nice thing about bi-amped systems was that you could drive them hard into clipping and they didn't sound so bad 'cause the midrange and tweeter were still getting clean signals. You could also get more effective power but that was thanks to the electronic crossover before the amps. Also, the amps tended to be different sizes, usually with a big honkin' bass amp and a much smaller mid/high amp.


Eww !! Did you wipe those numbers before posting ?

This is not true Biamping, even if the AVR manufacturer says it is...

Bobby, there's no "biamping as in the picture" going on; there's only one amplifier shown there, with several channels of output transistors(which have no power of their own)to meter out the power from the one main power supply section to the connected speakers. The maximum power output(200 watts or whatever)that the amplifier is capable of isn't doubled or increased by any amount. Biamping requires separate amplifiers with external crossovers preceding them so that the amplifiers only have to amplify a limited frequency range.

Almost nobody goes through the expense and complication of true biamplification for home use, and there's no need to. Axiom, for example rates the sensitivity of their various speakers at around 90dB(quite loud)for 1 watt of input. 1 watt is all the power that's used for that sound level even if a 1000 watt amplifier is connected. Brief peaks on highly dynamic material, such as some classical recordings that I have, can use much more, of course, but the typical modern receiver with a rating somewhere in the 100 watt area is entirely satisfactory for nearly all home audio requirements. Relax.

That illustration is straight from the Sunfire TGA-5200 manual.