Active crossovers

To add to the post above, most amps are pretty linear in what is called their "gain curve". This means that what you put in is amplified at the same level regardless of how much drive is applied. To put things into generic numbers to make things easy to follow, putting .1 volts into the amp would give you 10 volts out. Putting 1 volt into the amp would give you 10 volts out. Putting 10 volts in would give you 100 volts out. In other words, it SHOULD remain a consistent LINEAR ratio.

If that were not the case, momentary peaks would be REAL loud and quiet passages would be REALLY quiet if you adjusted your listening level by the average output. Obviously, linear amplification can take place so long as the amplifier is not driven beyond its' capacity and there is enough signal to begin with to drive the amp. I have seen situations where there was enough signal to drive the amp, but not enough to drive it to full output. This tends to sound "flat" due to the reduction in dynamic range and "squashed peaks" that occur in such a situation.

With that in mind, setting the drive levels for each amplifier at the crossover SHOULD produce relatively even output through-out the various frequency ranges. This should take place regardless of volume adjustments at the preamp. Obviously, something to check before buying a crossover would be the amount of adjustability in output from band to band that the crossover would allow. It is possible to use amps with varying levels of gain so long as one could gain match them to begin with. The fact that the individual amps may be being driven harder or easier than one another to achieve initial equal output should not come into play so long as they are TRULY "linear" in amplification and have enough headroom to linearly amplify the signal presented to them.

If the amps were NOT linear in amplification, another factor that would need to be factored into the equation is that the impedance that each amp sees at the output would also vary. As such, power potential for each individual amp would change too. It is quite possible that one could be using two identical amps to actively bi-amp with and still have two different wattage potentials. This is due to the differences in impedances that the amp sees in each frequency range.

For instance, a speaker using a single tweeter and dual mid-woofers ( like a D'Appolito or MTM array ) might present an 8 ohm load for the tweeter and a 4 ohm load for the mid-woofers. While some of this would have been addressed in the passive crossover components, one could not make adjustments for this at the amp or active crossover other than to initially make sure that the output levels were balanced. After that, it would simply be a matter of each amp having enough power potential to work within the volume demands that the end user dialed up.

Keep in mind that when multi-amping, it is possible to "clip", "overdrive" or "saturate" one amp and not the other being used in a different frequency range. This explains why one can TYPICALLY get away with using a smaller amp on tweeters than one would use with woofers. Different frequency ranges put different levels of power / current demand with low frequencies requiring the most "juice" to operate properly. While some e-stat's present a VERY TOUGH load at high freq's, there usually isn't enough musical content up that high to make it overtly demanding. That is, unless you expect high volume levels out of such a design. Sean
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KP, i would contact Albert and see what he thinks about active crossovers and see what he recommends in terms of necessary mods to the speakers. Most of the benefit of active multi-amping comes from going "direct drive" from amps to speaker drivers and bypassing the internal passive crossovers. Going active while still retaining the internal crossovers should offer some benefits but not all of going "direct". Sean
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PS.. Even if going to "direct drive" and bypassing the crossover or "dividing" network, it is still quite feasible and recommended to leave impedance compensation ) Zobel ) networks or notch filters in place. Doing so would require removal of the actual crossover network while still retaining some of the parts in the circuitry. That is why i suggest contacting the manufacturer before attempting to do anything. Putting their advive and knowledge to work for you could save you a LOT of time, money and headaches.

KP, it looks as if you were thinking about passive bi-amping. While there can be gains made by doing so, they do not in any way, shape or form compare with the benefits of active bi-amping. That is, if everything is set up right and the speakers do not have a ton of "passive parts" in them to begin with. Sean
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Since the speakers already have their own integral crossover, you would be crossing over electrically BEFORE the amp and then again after the amp inside each speaker section. In effect, the passive crossover parts that divide the lows from the mids would just be "exra junk" in the way of the signal and redundant unless you took them out of the circuit path.

I and others are talking "theoretical best performance" here, so keep that in mind. I guess that we figured if you're going to go to that much trouble to buy the amps and crossover, you might as well get the best results possible. You could actively cross and leave the speakers alone internally. It would be a step up in amplifier efficiency and power handling for the speakers, but i don't think it would compare to the total benefits of "direct drive".

Keep in mind that even if you did actively bi-amp, you would still be relying on the passive crossover components between the mid and tweeter if you simply divided the speaker between highs and lows. As such, you REALLY do need to discuss this with Albert and see what he thinks is best. After all, he should know his product better than anyone else. At least one would hope so.. : ) Sean
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If at all possible, you would want to actively tri-amp. Take into account that this is a LOT of set-up to say the least with a pretty massive amount of cabling, amplifiers and rack space taken up. It can and will change the sound of your system, possibly to a very large extent. My experience is that doing something like this produces FAR more liquid and transparent sound IF you can get everything dialed in. This can be a VERY time consuming "if" and one must have both patience and some help to do this. If it sounds like i'm trying to talk you out of it, i almost am. You REALLY need to think about what is TOTALLY involved in doing something like this.

My one concern about your speakers is that they have an "extra" rear mounted tweater also. Do you know if it crosses over at the same frequency / slope as the front firing tweeter ? Sean
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PS... I am the poster child for "something", but i don't quite know what it is : )

I'm using a Marchand XM9-3 Deluxe to tri-amp one system. I'm pretty pleased with it over all. The biggest drawback to this design is the lack of variable crossover points. You basically have to install very inexpensive "resistor packs" to adjust frequency. While it is not really a big deal, it's nowhere near as convenient as having an adjustable pot on the faceplate. It is probably a LOT more precise though. Other than that, i've only used professional grade crossovers and they did not sound as clean or focused. Nor did they offer the added versatility of the "blend" or "Q" adjustment that the Marchand has.

Mike Bates ( aka "Magnetar" on AA ) has used a Marchand that he built as a kit along with a Behringer model. He said that the Behringer has some nice features and works better on the low frequency range whereas the Marchand is cleaner up top. He also said that the Behringer has some features that he's found to be quite useful that are not available on the Marchand. He's a very experienced "tinkerer" who's judgment i trust and respect.

There was a Pioneer crossover that was made that seems to be relatively sought after. I noticed that while i was looking for one, there were other "wanted" ads posted for it on both A-gon and Audioweb. Can't remember the model right now, but it offered you the choice of four different slopes ( 6, 12, 18, 24 db's per octave ) along with some other nice features.

My brother is currently using one of my older professional grade crossovers that i used to use when doing pro sound reinforcement at concerts. It offers variable slopes ( adjustable from 1.5 to 12 db's per octave ) and variable crossover points for each band. This one comes in very handy as it makes it easy to find optimum crossover points when building speakers from scratch. Once he's got the cash, he's going to go into a Marchand. I hope it's soon, as i've got a large line array ( 54 drivers per cabinet ) that i need to start "fine tuning" in terms of crossover points. Sean
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