[Angaria]

Before I subject myself to a bunch of MDF dust, was wondering if anyone had experience with tube-ss biamp systems.  Specifically, I'm wondering how low the tube amp needs to go to capture the best of what tubes do.

I'm working on a design using this horn/compression combo  http://sites.google.com/site/drivervault/driver-measurements/horns-and-waveguides/qsc-pl-000446-gp/frequency-response (b&c de120) and one of these  http://sites.google.com/site/drivervault/driver-measurements/15/ae-speakers-lo15 AE dipole15 (90dB). 

Looking at a crossover around 1.5KHz - the compression driver will be run with a SET, and the woofer with 200 watt class D receiver  (thinking completely separate low and high pass filters, then work out the gain with individual volume controls on each amp).  Is 1.5KHz low enough to imbue the system with tube qualities?

If I need to go lower, I have a 12" B&C mid I could throw in, but I'm trying to avoid the crossover complications.

[iGrant]

Interesting question, tubes are supposed to give you 'even' order harmonic distortion and even and odd in SET, which our ears find pleasing. Instrument fundamentals (note attack) create harmonics which start an octave above, at double the fundamental's frequency.

Fundamental frequencies for all but the lower octaves or bass start around 100 hz, so the first even order harmonic (the loudest harmonic) would say be starting around 200 hz. Middle 'A' on the Piano is 440hz, so again a lot of even order harmonic information is around 880 hz plus minus an octave.

How low you can go with the crossover of course depends on what crossover roll-off slope you are using, at 1,500 hz you will need to lose a pile of power going to the tweater in around one octave, at least a 24db slope. So in this theory (or my speculation) most of the perceived benefits of tubes are going to be in your deep crossover slope which you will be trying to match with your SS matching slope going the other way up.

Not really sure how this relates  to your question, I just woke up and this was the train of thought I was on reading your post. Personally I want tubes on the bottom as well, I horizontally bi-amp often and you can always dial in the tube bass amp.

You may want to try an active crossover to experiment what works for you and your speakers.

Cheers,
Ian

[DaveC113]

The magic starts at 82.3 Hz. 

[doug s.]

my present tri-amped system has its x-overs at 80hz and 300hz.  (slopes are at 48db/octave, w/deqx dsp x-over.)  i have tried both tubed and s/s amps for the region between 80-300hz, (which is a 15" fostex pro-audio driver installed in a klipsch lascala bass-bin; decware-modded fostex fe206e drivers in oris 150 horns on top, and vmps subs on the bottom), and noticed no difference in performance.  and, when i bi-amped, (24db/octave marchand active x-over), i had s/s amps driving the subs from 60-80hz w/tubes on the mains.  so, i would recommend tubes no lower than ~60hz and no higher than 300hz.

ymmv,

doug s.

[Angaria]

thanks guys - some helpful thoughts and guidelines in there, regards.

[Tyson]

Anywhere between 300hz and 500hz.  I'm using a SS amp on my bass woofers, and a tube amp on my mid woofers and tweeters.  Below 300hz, and the tube amps are taxed too much, and above 500hz and the SS amp sound tends to intrude too much (for my liking, anyway). 

[Wind Chaser]

That will depend on the tube amp. 

[Niteshade]

Why not 20-20,000hz? It is a contiguous spectrum and should be handled fluidly, not disjointedly. It is true that power output is divided among every sound-making source within music. This fact tests an amp's abilities to encompass the full spectrum on its own (without bi-amping, electronic crossovers, active subs, etc...).  Power is indeed part of the sound quality equation.  It's the same with computers. A larger processor can handle more jobs easier than a small cpu. (I.e. A single core vs a quad core.)

That was a slight tangent- but sound quality is a function of how well an amp can multitask and keep everything together throughout the spectrum.  Some songs are purposely thinned so amps can play then louder. I have several songs that do this. Bi-amping is load division and allows better resolution during demanding volume settings or wide bandwidth passages.

I don't believe it matters whether an amp is tube or solid state. It's all about how an amp handles the entire spectrum when the demands are high upon it that creates magic. Can a full sound stage be maintained, without diminishing details during high output demand?  Can it do it without glare, brittleness? That's where the magic comes in.  I have heard some awfully good amps of both technologies that have the ability to sustain their wattage ratings while reproducing difficult passages.

In condensed form, audible magic to me is simply about accuracy, cohesion, resolution and sound staging within the amp's specifications.  I took the word 'tube' out and replaced it with 'audible'.