Hello everybody, I have a question - what are possible advantages (if any) of using amplifiers in bi-amping configuration? Some brands (REGA) claims that there is no perceived difference in sound......I have Spendors S5e (87dB , 8 Ohms with 3.2 minimum) driven with Creek Classic 5350SE (85W. @ 8 Ohms). Would adding Classic A53 Power amp (and driving speakers in bi-amping mode ) helped as I have a feeling the integrated struggles a little with load (Spendors)
There are numerous articles on the web explaining bi-amping in advantageous and disadvantageous manner. One of the most egregious disadvantages is in the cost of the total system. If you are bi-amping because your speakers are diffcult to drive, then you will be looking at a fairly expensive amplifier in order to find anything capable of actually driving a very difficult load and still remaining poised at al times while facing potential disaster at any moment.
The most logical way to go about this would be to use outboard active crossovers in front of the amplifiers. This would reduce the stress on the amplifier driving what would have been the low impedance/high phase angle passive crossover circuit. By taking the passive crossover out of the amplifier/speaker circuit the amplifier will see nothing more than the load of the driver which will remain fairly stable unless you do something unreasonably stupid.
Of course, finding active crossovers that are transparent enough for home audio use is difficult and expensive. More importantly, too many passive crossovers today are designed with the "watts are cheap" approach to system building. This results in the low impedance/high phase angle designs that are all too common in home audio. Most of these crossover circuits include notch filters, baffle step and other correction type circuits meant to tailor the driver's response to what the designer desires. Unless you have active crossovers with numerous small filter adjustments or have circuits purpose built for your speakers, you won't be able to duplicate the high Q 1.75dB dip at 1.2kHz that the original passive crossover contains. Without that filter action, you no longer have a Spendor as Spendor intended it to be heard.
IMO, rather than try to drive ten pounds of potatoes into a five gallon bucket, you would be better off buying speakers your present amplifier can drive with ease.
or alternatively buy a more capable amplifier - more capable in the sense that it can cope with the adverse load. It may still develop 'only' 85wpc, but it's more a question of how stiff its power supply is and therefore how much juice it can deliver into adverse loads.
Of course, if you have a genuinely nice amplifier and simply want it to be more powerful so it can drive your speakers, biamping is certainly a way around the problem. Biamping can introduce phase issues which the active solution spoken about above circumvents (if done properly). This is because the signal is arriving through one amplifier slightly later than the other, courtesy of the extra wiring and distance. However, if you keep the interlinking cables as short as possible and the speaker cables the same lengths and brand, then this should mitigate the worst of it. I use this method because my speakers are far worse to drive than yours. The results in my case are, as you'd expect, a compromise. The extra power has taken a hold of and controlled the speakers far better than when I was running them off the same multichannel amplifier in single amp mode. This has given the bass some definition and control, the speakers are less 'stressed' due to lower distortion and the whole thing is less muddled. However, the leading edge attack suffers a bit by comparison and this is an obvious reflection of the phase problem caused by biamping even though I'm using short runs between the channels.
"Biamping can introduce phase issues which the active solution spoken about above circumvents (if done properly). This is because the signal is arriving through one amplifier slightly later than the other, courtesy of the extra wiring and distance."
Actually, Frank may be right, but for the wrong reason. For the sake of the arguement, let's say the ear can hear 1 milisecond differences. That is .001 second. At the speed of light that is nearly 200 miles worth of wire....clearly a non-starter.
However, it is vaguely possible that latency of a signal within an amp will produce some time delay effect...not as bad as an echo, but perceptable at some level. The same signal can take a different amount of time to go thru 2 different amps. Using a pair of same-amps should mitigate this effect, if it exists at all.
You would need a gigahertz o-scope to stand even a small chance of observing this effect.
I can see where the effect of pasing the signal through numerous capacitors and inductors within an active crossover (or two) or a different amplifier can result in phase and timing errors. But I can't see how a few feet of interconnect can add phase errors of an audible nature. IMO, this is similar to why so many contemporary recordings sound so bad. Passing the signal through multiple effects devices - none of which might even attempt to preserve absolute phase integrity - can result in the type of sound that passes for saleable in today's market. But, Frank, at the speed the signal moves through the cables, I just can't see how the length of interconnect in a typical installation can affect the phase to the point of audibility.
Jan, we are pretty much on the same page here. It might be added that moving a speaker will produce more effect than even adding a mile of wire.....sound travels about 1100 or so ft/set so 1milisecond works out to over 13 inches....clearly moving a speaker that much does produce an audible effect. The rest I agree with........In general, messing with a signal LEAST produces better results: The mythical 'straight wire with gain'
The Marchand site has a layout for their XO's, starting with the exisrting Frequencies, of course. For a few grand, those are a one shot deal. Behringer supplies cheap active XO's for setup. Balanced and everything.
The results in my case are, as you'd expect, a compromise. The extra power has taken a hold of and controlled the speakers far better than when I was running them off the same multichannel amplifier in single amp mode. This has given the bass some definition and control, the speakers are less 'stressed' due to lower distortion and the whole thing is less muddled. However, the leading edge attack suffers a bit by comparison and this is an obvious reflection of the phase problem caused by biamping even though I'm using short runs between the channels.