Biamping with Jolida/McCormack/Proceed

Hi,

To truly bi-amp you will have to defeat the speakers internal crossover. You need to use one amp for the mid-hi and one for the speakers low end. If you do it as you stated you will be sending the full range of frequency to the speakers low end, this will result in a very muddied midrange. You need an external crossover of some sort to direct the proper frequencies to each set of drivers.

Cheers,

Ivan

With respect, Ivan, you are only partially correct. If the speakers in question have "bi-wire" inputs, then the high and low sections may be driven separately, and the speaker's own internal crossover will do the same job it always did (whether or not this is ideal is another matter). So it is possible to do just what Les3547 is proposing, and he can decide if the result is worth the effort. The input impedances do *not* have to match, assuming that the Proceed has a low enough output impedance to drive both amps in parallel (a safe bet in this case). In addition, the input sensitivities do not have to match *so long as* you have a way to control the level of the more sensitive amp. Again, this is the case with the amps that are being used. So, Les3547, go ahead and give it a try. You will need to adjust the level of your Jolida amp carefully with material you know well to get the high and low sections matched properly. This is critical, and it may take a few days to get it just right. It should be an interesting experiment at least, so have fun.

Finally, I will add one more thing: this sort of bi-amping is fun to experiment with, but it rarely works to complete satisfaction. A really good speaker design is a very subtle thing, and small changes in the behavior of the upper or lower sections can upset the coherence of the design. Different amplifiers (let alone different types of amps) sound different (surprise!) and introducing these differences across a crossover point often set somewhere in the midrange does not always work well. But you never know - that's why you've gotta try it!

Best regards,

Steve McCormack
www.SMcAudio.com

Thanks Ivan for your comment, I should have made it clear my speakers (Legacy Classic) are biwireable. Everything I've read says to biamp properly requires an active crossover and to disconnect my speakers' crossovers, but I don't want to go that far at this time.

Steve, I was pleasantly surprised to get a response from you, but grateful since I've not been able to find a specific answer to my question. I hesitate to try what I proposed because your amp already seems tube-like in the midrange and sweet on the highs. If someone weren't selling the Jolida locally and offering to let me try it out (and if I didn't have a little spare cash right now), I wouldn't do it. My biggest fear is that the tubes will cost me in high frequency extension and resolution, but of course now that you point it out, the loss of coherence too.

If I do try this I'll report back here. Thanks again for the advice.

Steve,

I'm sure you are right. You are the expert, after all. But now I'm really confused. Is the method that you suggest considered bi-wiring or bi-amping? I bi-amp my own speakers with an external crossover, the links are removed at the binding posts, so each amp drives a particular set of frequencies discretely. What is the potential benefit of bi-amping without removing the speakers crossover from the picture? Is it the hope that there will be some magical synergy between two different sounding amps?

Regards,

Ivan

Hi Ivan -

You're right - it does get confusing. I think the problem stems from the fact that the term "bi-amping" is pretty generic, since all it means is using 2 amps, and there are quite a few options for how it can be done. In its original form, bi-amping (or tri-amping, etc.) involved the use of an electronic crossover to split the signal before the amplifiers, and the amps were connected directly to the drivers. More recently, speakers have begun to offer multiple inputs to the built-in crossovers to allow for bi-wiring, but this also opens the possibility of using multiple amps. This is still technically "bi-amping," even though no external, low-level electronic crossover is used. Both amps are driven full-range, and the speaker's own internal crossover does the job of shaping the signal sent to the drivers. There can still be a real advantage because multiple amplifiers can deliver more power with lower distortion, etc. However, you open a major can of worms at the same time if you use different amps, cable, etc.

I have experimented with various forms of bi-amping, and I can offer a few observations:

1) "Passive" bi-amping (which does not use an external crossover) can work very well if it is done with identical amplifiers and speaker cable. It *may* work well with different amps, but this is an extremely complex issue.

2) Passive bi-amping may be arranged either "vertically" or "horizontally." I believe the vertical arrangement works best, with one matched stereo amp per speaker and matching speaker cable. Each amplifier is driven with one channel's full-range signal, sent to both inputs (using a "Y" splitter across the inputs), and each output drives a separate section of the speaker. This means you are not only bi-amping, you are effectively running the amps as 2-channel mono, so you've got a bi-amped, bi-wired, dual-mono arrangement. The horizontal arrangement assigns one stereo amp to the high-end of *both* speakers, and another stereo amp to the low end of both. Each stereo amplifier receives the usual L-R full-range stereo feed from the preamp, but one amp is connected to only the high-pass section of both speakiers, and the other amp is connected to the low-pass sections. This will certainly work, but it defeats one of the main advantages of the vertical option: when both channels of a stereo amp are driven with the same signal, the amp is effectively used in mono, and there is no difference signal (or crosstalk) across the power supply and ground system.

3) In my experience, the main reason people choose to try any of these methods is because they think they can combine the best characteristics of *different* amplifiers (and often different cable) for improved overall performance. While this may seem like a reasonable idea, in practice it is extremely complicated and rarely works as well as simply driving the speaker full range with a single good amp. The reason is because speaker design has become very sophisticated, with the drivers, crossover, wiring, and cabinet tightly integrated into a seamless whole. Furthermore, many bi-wireable, full-range speakers have the low-to-mid/high crossover point somewhere in what is effectively the midrange, where our hearing is most sensitive. It doesn't take much change to upset the coherence of these designs. So, whether or not this sort of bi-amping works and, possibly, works well depends a lot on the speaker design and where its crossover points lie. I know a number of speaker designers who have chosen to sidestep the whole issue by eliminating bi-wire inputs. That way, it can't be screwed-up.

4) Using an external, electronic crossover does not necessarily help. Unless the speaker in question allows you to bypass its internal crossover and connect directly to the drivers, you are still using the internal crossover no matter what you do to the signal being fed to the speaker. Removing the "strap" or jumper connection across the bi-wire inputs does not bypass the internal crossover. Furthermore, if a speaker has been designed as an integrated whole including its crossover, an external electronic crossover would have to be designed to mimic the exact behavior of the internal crossover in order to achieve similar performance during bi-amping.

5) I like passive bi-amping a lot, especially the "vertical" arrangement, but I find it usually works best with matched stereo amps and cables.

As with all things audio, Your Mileage May Vary ;-)

Have fun!

Best regards,

Steve McCormack
www.SMcAudio.com