No, You Cannot Bi-Amp

01-20-12: Magfan
Relative power needed is almost entirely governed by crossover point.

If you crossed over at 10khz, you could make due with a 30 watt tube amp on top of a 300 watt SS.

Than, other issues would come to the fore.

Right! A major "other issue," if the two amps are being used in a passive biamp arrangement (i.e., without an active crossover ahead of the power amps) being that some number approaching 270 watts of the 300 watt capability of the SS amp could not be utilized, without clipping the 30W amp. Essentially the 300 watt amp would be reduced to not much more than a 30 watt amp in that scenario (the exact value depending on the voltage swing capability of the 30 watt amp). Which was exactly my point.

Best regards,
-- Al

if you are going to use the in-cabinet speaker x-overs as-is then the best way to do passive biamping is the method done by member 'jefferybehr' - he's used 4 identical amps that are driven by his preamp. Take a look at his system pix.

I'm sorry, but the power relative power needed IS governed by the crossover frequency. At least for music with a 'normal' distribution of frequencies.

With the crossover at 10khz, per my example, you really would need more than 90% of the power below crossover, with only 10% above.

http://sound.westhost.com/bi-amp.htm

The 50:50 point is about 350hz. I don't know that active or passive makes much of a difference. The amp will only have to produce power for those frequencies for which the speaker has a need.

The 'other' factors I was thinking about would be amp latency. How long it takes a siganl to pass thru the amp.
Also, gain and how linear the gain is will play a part in freq. balance thruout the volume range.

I have a straightforward question for Elizabeth...

... who has a most strong negative opinion of actively bi-amping, e.g. Magnepans, and seems to have an even stronger negative opinion of the people ("adolescents") who engage in the practice:

Has she ever actually heard a pair of Magnepans, e.g. the 3.5s, 3.6s, or 20.1s, that were bi-amped with two excellent amps and an excellent line-level external active crossover, e.g. a Pass Labs XVR-1?

Has she ever done anything close to an A/B comparison of a pair of Magnepans thusly bi-amped and the same pair single-amped with the stock, or even a "Gunned," passive crossover?

If so, what did she hear to cause her to demean so vehemently active bi-amping?

If not, where does she get her confidence in such an ungrounded opinion?

Respectfully (up to a point),
David Zimmerman

01-21-12: Magfan
I'm sorry, but the power relative power needed IS governed by the crossover frequency.... The amp will only have to produce power for those frequencies for which the speaker has a need....

Hi Magfan,

Somehow my point isn't coming across.

Yes, the amp will only have to produce POWER for those frequencies for which the part of the speaker it is connected to has a need. However, in a passive biamp arrangement, where there is no active crossover ahead of the power amps, both the high frequency amp and the low frequency amp will need to produce the SAME output VOLTAGE, corresponding to ALL of the frequency components of the music.

And therefore if the low frequency amp has a rating of 300W and the high frequency amp has a rating of 30W, corresponding to the maximum power requirements above and below a crossover frequency that is very high, the 300W amp will not be able to produce 300W, or anything close to it (in a passive biamp arrangement), without the 30W amp (which presumably has a far smaller voltage swing capability) being driven into clipping. Therefore how far the volume control can be turned up without severe distortion occurring (and perhaps a blown tweeter as well) will be limited by the output voltage range of the 30W amp, and most of the power capability of the 300W amp will not be usable.

As I said earlier, that is a point that is commonly overlooked. I have often seen questions about passive biamping that refer to the possibility of purchasing amps such that the low frequency amp has a power rating several times greater than the rating of the high frequency amp, which makes no sense.

Best regards,
-- Al

Als right. For me best bi tri amping comes from matching ea amplifier to drivers it will run. This is a pain to pull off but once done worth while. Had a horn system with class d on bass horns, PP on midbass horn,SET on midrange horn,low power class A on horn tweeter worked very well though I had to try many amplifiers ;) Today I mostly biamp using Class D or SS on bass horn and SET on main horns. So 250-500 watts on bass and 12 watts on mains...