Need help What monoblock power amps for bass?

Thanks a lot for all your kind answers.Dalton,monoblocks are mandatory due to the short speakers cables i own.I already chose this setup along time ago.

Ngjockey,i am still considering what attenuator to use,still i am not clear on this.Your input is very helpfull.But you were right,i was considering the pots.

Ramy,your speakers seems very serious and good.I appreciatte the input.I think power is not very important for Sinfonias,anything above 50 Watt would be ok.

Audiobb, my experience has been that while you can get much greater volume levels by bi-amplifying, you also pay a big price- figuratively and literally! First, to do it right you have to use and electronic crossover. Good ones are expensive, and all of them behave not only as crossovers but also as filters for detail and impact. You also have to pay for another amplifier.

I have found the most convincing systems don't use electronic crossovers, instead the amplifier drives the speaker full-range. Otherwise you face prodigious integration issues, and the better your speaker is the more you will notice them. For example, its a lot easier to bi-amplify if you use the same type of amplifier for top and bottom, as far as integration is concerned. That could be tricky in your case where you have an SET on top.

At any rate I've never seen a bi-amplified system work right. I've seen them sound OK, and I am open to the idea that one day I'll hear one that is done right but until then I advise against it- if best possible sound quality is your goal.

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.