Topic: Bi-Amping Help

[SonicSound]

I am trying to bi-amp (passive) a pair of Dali MS4's.  I am using tube amps (Cary CAD M50 MKII monoblocks) for the high's and a Solid State (ML No.23 Dual Monaural) for the lows.  When I hooked it all up it sounded really bad.  No distrotion but very muddy.  Any insight?

[Church-Audio]

I am trying to bi-amp (passive) a pair of Dali MS4's.  I am using tube amps (Cary CAD M50 MKII monoblocks) for the high's and a Solid State (ML No.23 Dual Monaural) for the lows.  When I hooked it all up it sounded really bad.  No distrotion but very muddy.  Any insight?

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Now when you say biamp are you using the built in crossover in the speakers?
Most speakers when they are used in biamp mode need an external crossover they just use a capacitor inside for protection of the tweeter. Also remember your going to have to match the amps output levels accordingly they will not sound good with out some form of reduction.

I would try this turn on the tweeter amp first and listen to it with a known source ( cd ) then slowly dial up the low end amp until you are happy with the balance then do several hours of listing tests to make sure you got it right.

The biggest problem with using two different types of amps is this input sensitivity of the amps will not be the same. Some manufactures rate 0 db at .775mv some rate it at 1.2 volts, what this means is it takes a signal of .775 to reach 0 db or unity gain = max output of the amp and at a low level of distortion if its designed correctly

So if you have two amps one is .775 and one is 1.2 volts your amp at .775 is going to reach max level long before your 1.2volt amp does. So if this amp was driving the low end it would need to be dialed back to achieve a balance not withstanding the speaker individual sensitivity rated in db 1 one meter.

This is why I cut thru all this b.s and just use my ears and turn up the lows first and the high second. To get a match. The only reason why I asked you to do it in reverse was so that you could confirm operation of the tweeter. I hope this makes sense. Also this should be done in the actual listing position if possible because it changes as you move around the room (standing waves and all that jazz) Most people that really want to biamp or triamp correctly will use a digital cross over that will allow you to change parameters like EQ delay between speakers to correct for the misalignment of the drivers so they are time domain correct (the highs and mids, and lows arrive at the same time to the listener) as well as phase correction.

There are lots of good reasons to biamp, but if the built in crossover is good and you have a well made high output amp. For most applications of 100 db listening levels with high sensitivity drivers there is little advantage.

Its when you really want to crank levels that a passive crossover tends to crumble, and increase distortion. That is the major advantage of a active crossed over system reduced distortion increased dynamic range.

Good luck with your system.

Chris Church

[SonicSound]

I am trying to bi-amp (passive) a pair of Dali MS4's.  I am using tube amps (Cary CAD M50 MKII monoblocks) for the high's and a Solid State (ML No.23 Dual Monaural) for the lows.  When I hooked it all up it sounded really bad.  No distrotion but very muddy.  Any insight?

\\

Now when you say biamp are you using the built in crossover in the speakers?

+T
No, I am attempting a passive bi-amp configuration utilizing the speaker internal crossovers.  Neither of the amps have a variable gain stage control.  How can I match or dial in the two amps?

In general I prefer the CAD 50’s over the Mark Levinson, however the ML drive the low end very nicely.  I was trying to see if I could get the best out of both amps.  I was also avoiding an active bi-amp scenario (bypassing the internal crossovers and using external crossovers).   

[Church-Audio]

I am trying to bi-amp (passive) a pair of Dali MS4's.  I am using tube amps (Cary CAD M50 MKII monoblocks) for the high's and a Solid State (ML No.23 Dual Monaural) for the lows.  When I hooked it all up it sounded really bad.  No distrotion but very muddy.  Any insight?

\\

Now when you say biamp are you using the built in crossover in the speakers?

+T
No, I am attempting a passive bi-amp configuration utilizing the speaker internal crossovers.  Neither of the amps have a variable gain stage control.  How can I match or dial in the two amps?

In general I prefer the CAD 50’s over the Mark Levinson, however the ML drive the low end very nicely.  I was trying to see if I could get the best out of both amps.  I was also avoiding an active bi-amp scenario (bypassing the internal crossovers and using external crossovers).   

A external crossover should have a attenuators built into it, if not then you have to build a set of attenuators. This sounds like more work then its worth. You could also try and rent a nice digital crossover and see how that works I would look at anything by LAKE processing or XTA these are not names that are known to the audiophile world but they make some of the most respected signal processors in the world for this application. You will need to hook them up to a laptop via USB or serial and run the free software avalible for download by the respective manufactures mentioned. These crossovers have output attenuation so you will be able to match the amps outputs. There are much cheaper solutions but in my mind if your going to all this trouble to make you system sound great spend money, or keep using the built in crossover in your speakers.


I would not suggest using L pads on the output of your external passive crossover, because of the inductance and reactive load the put on your amp will degrade the quality of audio to a huge degree. The other way would be to use a potentiometer on the input of each amp by building an external box but again you need good quality potentiometers for this and a well sheilded box. Ether way its a huge pain in the butt to do this.

[Lil Kim Jong-Il]

There are some relatively inexpensive active crossovers that show up on audiogon from time to time.   The Marchand tube units get decent reviews and show up regularly.

you can build one as well:
http://www.welbornelabs.com/acm.htm
http://sound.westhost.com/project09.htm
http://www.tubecad.com/articles_2001/Tube-Based_Crossovers/page4.html

(search the playback forum and you'll find some other links I posted a while ago).


In my system, I'm using tubes and SS like you are, but both are from the same manufacturer and are well matched.  I've been close to going active on a couple of occasions but I'm still satisfied running passive.  VSA recommends passive and they recommend against disabling the internal crossovers in their speakers.  The only thing I've added is a passive HPF (auricap) inline to the tube amp because the vandy sub taps off the outputs of that amp.

[SonicSound]

I think I am in over my head.  I thought that it was going to be a simple deal but not the case.  I think that it will be better to spend money on other components.  Thanks for all your help.