Tri-amping speakers - Which amps

Thus is the entire problem with tri-amping. How much $'s and complexity to achieve sound that often is far, far removed from the "flat" response that the manufacturer's seek.

B&W has the following on their website:

"The term crossover is a little misleading. A multi-way speaker contains a crossover network that not only divides the incoming signal into different frequency ranges, appropriate to the working range of each drive unit, but also equalises each driver's response to be flat (raw driver responses are usually anything but flat)."

They further have a very interesting article (it's short):

http://www.bwspeakers.com/index.cfm/fuseaction/local.faq/ObjectID/F5CA2EE1-3D20-11D4-A67F00D0B7473B37

There is a fair amount of confusion about passive xovers. Most people think their only function is frequency separation. Not true. In many high quality units the manufacturers have "shaped" the frequencies sent to the drivers to correct for non-linear drivers and cabinets.

Further, this huge "power loss" is somewhat a myth as well. Xovers don't really dissipate power (other than the trival internal resistant of the components). What they do is "block" frequencies unwanted for a driver.

In any event, Cnut, one way to insure you maintain the voice of your speaker systems is to passive bi-amp. That is, leave the passive components alone and use two amps. Each amp ends up with a much easier task because the impedance for each amp is just much better behaved/simplier.

My "gut feel" is people, who claim a huge improvement in sound out of tweeters, are simply sending more power to those tweeters. Yes, the sound is brighter/clearer, but the same could be done with EQ's and even tone controls.

Regards,
Jerry

Jerry mentions the 'flat response' being the speaker designer's intention (in some cases). Doesn't flat depend largely on environment. As I understand it, ideally you test a speaker outside to determine how it truly measures. Tri-amping with an outboard active crossover is the recommendation of the designer of the speakers I am considering. He has several designs of 2 way monitors (with passive crossovers) that he can match with his own designed passive sub(s). The builder has indicated to me that for the 'best' sound from his design you need to leave out the passive crossover from the monitor and go the active tri-amp route. You take measurements of the speakers output in your listening room using a Radio Shack meter and aided by pc software use the controls on the crossover to 'tailor' the sound to correct any problems with the room.
While this would take some work and time, it does seem to me to be the best way to get the most out of your equipment. This route would add some expense such as an active crossover, more cables, and more channels of amplification, but if done correctly would appear to have a lot of benefit. Yes, I know I said "if done correctly". It is common now for the more expensive subs, and some of the cheaper ones, to have a built in amp & equalizer to correct for any bass nodes in the room. Bass problems are supposed to be the most common and problematic but why not address problems at higher frequencies as well? Some speaker mfg put controls on the back of their speakers for basic adjustment particularly for the tweeter. Is this merely for personal taste or are they helping to taylor the sound to the particular room?

What speakers or drivers are you using?

BESL. Link below.
http://www.bamberglab.com/index.shtml

Cnut, the "flat" I was referring to is equal output from the speaker system over the entire frequency range with a given constant input.

Raw drivers will output more sound at some frequencies than at others. In many high quality speaker systems, the manufacturer has designed the passive networks to compensate for these non-linearities.

Now, there may be little of this in your speakers. Your internal networks may be nothing more than simple frequency separation and in that case, the active xover will give you far more control over the resulting sound and no degradation.

Cnut, you are correct that room dynamics can significantly impact frequency performance. Those controls for tweeters are there to compensate for rooms either full of sound absorbing materials or with many hard reflective surfaces. Active operation, however, will do a better job that those controls. You simply get much more control.

Since the manufacturer of your speakers suggests going active, that-s probably the way to go. My comments were really about folks who were contemplating going active on speaker systems where the manufacturer does NOT recommend active operation.

Lastly, I-d suggest the simple way to solve your problem is to purchase the two way monitors and then get a high quality powered sub. The high quality powered sub, by the way is active! Your active xover will supply the line level signal for the sub and then it will supply the line level for the mid-range and tweeters.

Cnut, if you go this way you only need a two way active xover and two stereo amps. Life just becomes so much easier/simplier.

Here is an example of a two way active xover:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=245-862

There are more expensive units to be sure, but many folks have reported successful results with these.

Hope this helps -

Jerry