Passive and active biamp together

Hi guys, I have a question for those of you with experience in both passive and active biamp.

Preamble 1: I was using passive biamp with 4 identical monoblocks, but, especially after a fine tuning in room acoustics, found out I got no significant advantage, so I reverted to single amp, putting the extra pair of monos for sale.

Preamble 2: my loudspeakers have double inputs (binding posts) for lows and mid-highs (xover freq 350hz@24db/oct), but the xover network, for what I can read in the manufacurer user manual, is pretty complex, making its removal unfeasible for going active.

Question: somebody told me that putting an active xover between pre and power amps, would be of great advantage anyway, even though the passive xover is not removed, because the amps would only take care their part, and especially because there would be much less energy dissipated in the passive xover, of course provided the active one is set at the same freq and slope, and its quality matches the rest of the system.

Haven't sold the monos yet, do you guys think there could be a point in this, worth getting a, say, Marchand XM126 tube xover to try?

Thanks to all,

The outboard crossover made a huge difference for me. I was trying to run relatively inefficient speakers with an 11 watt tube amp. The amplifiers were really struggling to drive my speakers. The outboard crossover took most of the load off the amps, allowing them to focus on the midrange and highs. I used a solid state amp to drive the bass. The result was magnificent. My upper end gained in detail and focus, the soundstage got deeper and better defined, the tone got sweeter, the entire soundscape changed--night and day, really.

That said, I don't know what it would do for your system. I believe your amps can do 50 watts into 8 ohms, which is not inconsiderable in tube terms. Whereas the outboard crossover was almost necessary in my situation, it would be more of an enhancement in yours. Certainly, dedicating an amp to your midrange and tweeter alone will have a positive effect; but, it is hard to say how dramatic the difference will be.
I do believe, however, that the difference between passive and active bi-amping is significant in every circumstance. In the case of tubes, the imperative is a good match with efficient speakers. If you love your speakers, they happen to be inefficient, and want them to play nice with your tube amps, then active bi-amping is a very good solution.

I hope that was helpful.


Eliminating the passive crossovers is as simple as wiring the drivers directly to their respective input terminals. Leaving them(X-overs) in place, wired, and actively biamping(if both were designed/adjusted for 350Hz & 24db/oct) would result in both the active and passive crossovers filtering the same frequencies(even though already attenuated in the signals, when they reach the passive networks). Your resulting slopes would be 48db/oct, and would leave a serious dip in your frequency response(beside probable phase aberrations).
Thanks guys for your informative replies.

Ivan, had a look at your great system, and you happen to use exatly the same Marchand XM126 active X-over I was thinking about, but it's not clear to me if you have removed the passive X-over inside your RBH speakers, have you?

Rodman, the reason why I said that removing the passive X-overs from my speakers is not practical, is that the manufacturer states that it implements a compensation network to correct phase and to linearize impedance, whatever that means, so I figured that wiring the drivers directly would mess up too many parameters, but I may be wrong of course. I'm not sure I understand how the slopes would become 48db/oct though, what I was told is that the passive X-over, presented with a signal already filtered, woudn't have to dissipate the exess energy, hence the advantage.
It's certainly a can of worms, Cptaz. I'm currently actively biamping. Before removing the passives, I implemented both active and passive as you described. It really did not sound right, as Ivan indicated. Removing the passives and going fully active yielded by far the most significant audible change in the system since I began messing with it. So, at the very least, it's interesting. I'm happy with the results but not yet satisfied.

I've been fearless mostly because none of my equipment is all that valuable. Your system? I dunno, man. I'll bet those speakers sound great as is. You might consider shooting an email to Marchand. Other members have reported that he is very helpful and willing to advise. As for myself, I'm currently using a cheapo Behringer CX3400, and I feel pretty good about moving forward eventually, probably Marchand's passive line level (XM-46).

If you end up communicating with Marchand, I do hope you'll share the experience.



No, I did not remove the internal crossover from my speakers. I simply removed the jumper between the binding posts. My situation is very similar to yours. A third set of amps would be required to remove the internal crossover, a separate set for the tweeters. Additionally you would also need to know where the tweeter crosses over with the midrange. Some people do actually tri-amp, but it would have been overly complicated, not to mention expensive, for me to do it. I'm sure, were you to want it, that the fine folk at Marchand would be willing to build you a crossover to manage the task. But, I can't imagine, unless you are feeling wildly experimental, why you would want to try that. I bi-amped out of necessity, not adventure. In my case, bi-amping pushed my speaker's efficiency from 88dB to 92dB, just enough to liberate the potential of my 11 watt amps.

I just recently took the Marchand out of my system. After a couple of years internal debate--uncomfortable with many of the reported problems with high efficiency speakers--I had the good fortune to run into a pair of Zu Audio Essences that I could take home before buying. I ended up liking them enough to keep, so I'm simplifying my system. My decision was both acoustic and economic. The Zu's are only slightly better than the RBH's in my system, a function of synergy rather than quality of design. I decided to keep the Zu's, in the final instance, because i expect a return on my earlier investment. I can now sell my speakers, my autoformers and the crossover. These sales will pay for my new speakers, and leave me with quite a bit of cash left over.

In any case, I stand behind my earlier statement. I know I needed to actively bi-amp, but I believe that your decision should be based on what kind of sound you want. It may be that you would be better off changing speakers. Perhaps a different amp would do the trick. It would help if you told us what you love about your components and what you believe needs improvement. I would consider bi-amping only if I were certain that I did not want to relinquish either amps or speakers.