Need help What monoblock power amps for bass?

Ralph, regarding your comments on bi-amplified systems, have you ever heard
the Orion system designed by Sig Linkwitz? In its intended configuration a
separate amplifier channel is used for each of the four drivers per speaker
channel. This is with an electronic crossover.

The Orion system has a very large internet following and reading Mr. Linkwitz's
site I found his design objectives closely match my listening goals. However,
I've heard two different Orion systems and was disappointed in both. I expected
the individual amp/driver configuration would have been an advantage (low
distortion?). Now, from your comments, I wonder if this could have been a
detriment?

Pryso, in many bigger setups you have a source, a preamp, some sort of interconnect for all this, the amps and the speakers.

We all need the source, the interconnections, the amps and the speakers. Some people feel the preamp is not needed (separate thread for that) but one thing is dead certain: the more building blocks in the chain, the more noise, distortion and lack of bandwidth. An electronic crossover adds quite a bit of complexity. You can always hear the reduction in transparency and other colorations they bring. In addition, drivers in a speaker often require more than just the crossover- they might need some tailoring to deal with resonance, and some may benefit by having some sort of series resistance, particularly if you are driving a high efficiency speaker with a transistor amp.

These things are usually sorted out in a passive crossover, and not so often in electronic ones unless they are set up for the specific speaker, as in the case of the Dali. But as Dali owners can tell you, its crossover is a barrier to performance that must be overcome to realize all the performance the speaker is actually capable of.

If you try to biamplify without the electronic crossover, your amplifiers will not be running efficiently at all because they will have to reproduce signals that are being absorbed by a passive crossover- kindof a messy approach.

IOW it is to your advantage to keep the system simple if you can!

DACT, Marchand, Goldpoint, Acoustic-Dimension and Shallco make attenuators, Shallco being ladder type. Most have 10K versions and some have more than 24 steps. There's probably more brands I'm not aware of. Even the Placette passive is 10K, as far as I know, if you want it packaged and a remote.

Again, using either series or parallel resistors along with attenuator can increase or reduce the overall impedance.

What about shunt-type attenuator?I am thinking about ordering a pair of Endler's attenuators,connected straight into power amp(these already have RCA plug joined with them,so there is no interconnect cable to drive from preamp to power amp).Why not use these,or at least try them,and then build a similar style with Vishay S 102 for example?
Seems to me that having only one resistor in signal path is better than more of them.
Atma,why is active crossover neccesary with bi-amping?What about the passive crossover in speaker?Seems to me that each driver still gets the range it needs.

Audiobb, you can use the passive crossovers in the speaker if they are designed in such a way to allow for separate amps. The problem is that while the speaker only sees the frequencies it is supposed to, the amp still has to reproduce full-range. You get a lot more power out of the system if you have an outboard active crossover to sort that out for you.

In the case of the passive crossover allowing for bi-amplification, it does seem to sound better than using an electronic crossover. A feature of our amps is that they can be monostrapped together; this always works better than running one top and one bottom, assuming that they are the same model.