Bi-Amping

LOL, well I am not one to hate anyone, I appreciate your.....comments. However, you can, and may, snub your nose at my set up- but I would challenge you to a listen before you condem what I have built. With that aside, I enjoy the sound, as do every friend I have, some have better systems and say mine sounds better. But again, as previously stated, I believe the power output is limited due to the B&K's 8volt output. One listen to Rush's Red Barchetta, or Tchaikovsky's 1812 Overture, or Yanni Live at the Accropolis will instuct you as to the performance of a multi driver, extreamly low bass, done right system that can only be recreated using many drivers, not your typical 2 or 3 way system, but then the experts over at Wilson Audio have no clue why they use multi driver systems do they?

I have verified the problem - finally - I borrowed a Luxman pre from a friend that has a pre level sub out @75Hz- I believe, and I can now cause the amps to reach full power and clip, while the B&K sounds better, the Luxman gets much louder.

While I am no fan of bleeding ears, I am going to call B&K and see what can be done, if anything. Maybe I have a defective pre amp, who knows? (as of yet)

Again thanks for your comments.

8 volts should be enough to drive any amp or pair of amps into clipping. Take a look at the amp's sensitivity rating; it's usually around 2V for full output.

Kal

You can hate me.......it won't hurt my feelings! Some of my ex-coworkers will tell you that I made a career of getting people (mainly bosses) to hate me. Ah......the good ol' days.

Anyway.

Seriously, if you are going to try that many drivers, with that combo of crossovers, you MUST use some fancy measuring stuff to know that it is done right. In which case, you would know for certain what the problem is.

I'm not saying that multiple drivers, etc. won't work. I am saying that you can't guess what works and what doesn't. I think it is a safe guess that you do not presently have the gear to do such. Ergo, you don't know why you have a gain problem.

OK, back to your problem.

8 V out of a preamp is enough to melt any amp. Most amps have 26 dB of gain. A few dB either side, maybe.

As for drive, it should be able to drive 2 amps. Most amps are at least 10K input Z. That is not likely to be the problem. 5k is not that hard of a load to drive, which is probably a safe guess for worst case. A mismatch in gain more likely is.

As for your setup............you may want to try 4th order Linkwitz-Riley. That many drivers, with crossover points so close together, can be a nightmare. Not only do you have to take into account the phase of the crossover, but also that of the drivers. Heh, heh.....

One of my famous audio designer buddies had a very expensive multiple driver systen, made by a very well-known designer. I showed him how it had a nasty comb filter effect, depending on whether you were a short guy like me sitting down, or a really tall guy like him standing up. And everything in between.

He very quietly put them up for sale 2 weeks later.

But I do not understand why the pre-amp needs to be cranked all the way up just to get nearly the same sound (dB) I had previously

Your ears are fine, and yr setup seems correctly done. What's happening is you're losing energy in the pre->2amp connection. That's because you have halved the input impedance of the amps by putting them in parallel -- i.e. the "combined" load the pre sees is now very difficult and it is struggling to provide the appropriate amount of energy (and isn't making it). The two amps together are sucking up the pre. Remember, when you halve the voltage, the wattage drops to 1/4th.
The rest (room, you need a shrink, 3way xover, etc) don't apply;^) Cheers!

Heh, thanks Gregm, yout thoughts (final ones are noted) :)

I agree, the pre is my problem and I have confirmed this by using another preamp. I have sent an email to B&K but I havent recieved any return responce as of yet. Possibly a phone call on mMonday would be a better idea.

The only options I believe I have are to either use a different pre, or, an electronic cross-over.

As for my cross over points, each driver has it's own independent crossover network which is terminated to it's appropriate power input. With exception given to the subs, they use the internal 80hz low pass x-over via the B&K.

Since I do not have the working knowledge of how the output from the B&K is provided (independently, or summed), I can not say what amount of voltage is present under a given load (the amplifiers draw at various output levels).

I appreciate your help guys, I really do, while I do not agree with all that has been written it is food for thought.

Thank you