[russe41]

Trying to biamp von schweikert vr4hse's with the top speaker being 8 ohms and the bottom being 4 ohms.
On top i'll be using a cary v12 (50watt)with a input sensitivity of 1.3v balanced or unbalanced and the bottom speaker will be driven with a mcintosh mc352 (350watt),input sensitivity of 1.9v unbalanced and 3.8v balanced.
They will be driven by a mcintosh c2200 preamp which has balanced or unbalanced outputs.
Is it best to just run the amps unbalanced,and will the 0.6v be negligible or should I be concerned about this?
Also am I going about this the correct way and if not what should I try?

[mgalusha]

What you really need to know is the gain in dB. It can be calculated from the input sensitivity if the manufacturer accurately supplies the output level for the specified input sensitivity, many do not.

The gain needs to match for things to sound right. Does either of the power amps have a level control? If so this can be used to compensate for a gain difference if there is one. If not, some method for doing this is needed. Bi-amping with dissimilar amps is never as easy as one hopes even if the gains match the tube amp and the SS amp might have signatures different enough that they don't blend well.

You can use a passive level control to match things up but that of course introduces additional concerns, primarily with impedance matching.

Sorry for the less than upbeat answer but it's not the easiest task to get a setup like this working seamlessly.

mike

[russe41]

  Mike,
  Neither amp has level controls, as far as matching gain in db I will email
  both companies and see if they'll give me that info. For now i'm taking
  test measurments with a radio shack SPL meter with different setups.
 
          Russ         

[richidoo]

V12 specs  Gain varies with load and amp mode. But ultra linear mode gives 25.2dB into 8 ohms. It really depends how the impedance behaves at the crossover. If it drops, your V12 gain will drop too, down to 21dB at 4ohms.

I can't find gain spec on the Mac, but I would guess 26dB which is industry standard. It appears that the c2200 has no provision to adjust the output volume separately.
Scott Endler makes a quality inline attenuator which could adjust the amps to the same gain.

As Mike suggested, it is usually pretty tough to mix tube amps and a SS amp together in the midrange. They have different flavors that just don't gel. I have tried to mix a 100W tube amp with MC402 using C220 preamp, on two different speakers, it just didn't work. But if the crossover is steep and low enough it might work out better.

A tube amp reacts to the speaker load diferently than the SS amp, especially a mac with autoformer output which isn't phased at all. In the crossover region especially is where speaker impedance can vary which trips up the tube amp, while the SS amp just pours on the juice.  It's worth a listen though! Good luck
Rich

[russe41]

I'm not opposed to doing some butchering so to speak and using an electronic crossover if it will integrate the system better?
Actually i've been throwing the idea around for awhile, just not sure how it changes the picture,seems like people who go this route seldom return to the passive way.

[mfsoa]

Russ.

I've been dreaming of doing the same w/ my VR4JRs.

What I envision is running the upper unit on the tube amp, using the internal speaker crossover to limit the bass frequencies. (200 hz crossover in my model, I think).

The bass cabinet would be fed by taking the output of the preamp into a digital crossover/eq thingy (Behringer - I forget the exact model # - DEQX2496 or something) then into the bass amp. This way, the DEQX not only acts as a level adjustment but can EQ the bass, where room modes are usually the most severe and the most correctable.

I'm hoping that any negative impact from 200 hz on down from the additional A to D and D to A conversion and associated processing will be offset by the ability to EQ the bass and match levels w/ the mid/tweet.

-Mike

[doug s.]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

doug s.

[Coytee]

On top i'll be using a cary v12 (50watt)with a input sensitivity of 1.3v

the bottom speaker will be driven with a mcintosh mc352 (350watt),input sensitivity of 1.9v unbalanced and 3.8v balanced.

They will be driven by a mcintosh c2200 preamp which has balanced or unbalanced outputs.
Is it best to just run the amps unbalanced,and will the 0.6v be negligible or should I be concerned about this?
Also am I going about this the correct way and if not what should I try?

I've not seen it mentioned yet.  If you are going to genuinely biamp (with active crossover) then here is a forumla you might want to know.

20*Log(v1/v2)

Where V1 and V2 are the input sensativies of each amp.  Knowing this, you will come up with an answer.  So for example, we have 20*log(1.3/1.9)=(-3.29)  This means you need to attenuate the more sensative amp (Cary) by 3.29 db's.  In my active, I don't know if I can go past 1/2db increments.  I would think if you attenuated by 3 db's you'd be good to go.

Knowing this you can volume match just about anything.  By the way, if you flip/flop the values (1.9/1.3) you will get the same NUMBER but it will be a positive value and not negative.  So ultimately, it does not matter WHICH number you put where as long as you realize what ever the value is at the end, is the amount of db's you want to attenuate the more sensative amp.

Hope this helps.

[Coytee]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

I agree.  I've biamped now for several years and have used solid state/solid state and solid state/tubes.  I've had zero problems getting things to sound good (other than some unrelated hum I had during some RCA/XLR conversions)

[face]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

doug s.

That sounds a lot easier than it really is.

[doug s.]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

doug s.

That sounds a lot easier than it really is.

yes, i realize that, depending on the speaker, it may be quite difficult to bypass the passive x-over.  doesn't change the fact that it will be dumb luck to get good results passively bi-amping w/two dissimilar amps.

doug s.

[face]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

doug s.

That sounds a lot easier than it really is.

yes, i realize that, depending on the speaker, it may be quite difficult to bypass the passive x-over.  doesn't change the fact that it will be dumb luck to get good results passively bi-amping w/two dissimilar amps.

doug s.

Sorry, I should have been clearer.  I know people who have bypassed the original crossover and have gotten odd results, even though they tried to emulate the original points and slopes.  And yes, bypassing the stock crossover can be a little work, but that's only grunt work. 

As far as bi-amping with tubes on top and SS on the bottom before and retaining the OEM crossover, I've also had mixed results.  I had a Welborne ST-70 on the tweeter section of my modified Tannoy Saturn S8's and a McIntosh MC-2125 on the woofers.  There was one small area of volume where things sounded balanced and sweet.  IIRC, too little volume and things were bright, too much and things shifted in the other direction.  It was a fun experiment though. 

Btw, nice Conure(green cheek?).

[doug s.]

i would strongly recommend bypassing the passive x-over and going with an active x-over, if you want to bi-amp w/two different amps, especially if one is tubes, the other solid state.  if you get good results w/the passive x-over, it will be dumb luck.

doug s.

That sounds a lot easier than it really is.

yes, i realize that, depending on the speaker, it may be quite difficult to bypass the passive x-over.  doesn't change the fact that it will be dumb luck to get good results passively bi-amping w/two dissimilar amps.

doug s.

Sorry, I should have been clearer.  I know people who have bypassed the original crossover and have gotten odd results, even though they tried to emulate the original points and slopes.  And yes, bypassing the stock crossover can be a little work, but that's only grunt work. 

As far as bi-amping with tubes on top and SS on the bottom before and retaining the OEM crossover, I've also had mixed results.  I had a Welborne ST-70 on the tweeter section of my modified Tannoy Saturn S8's and a McIntosh MC-2125 on the woofers.  There was one small area of volume where things sounded balanced and sweet.  IIRC, too little volume and things were bright, too much and things shifted in the other direction.  It was a fun experiment though. 

Btw, nice Conure(green cheek?).

ah, makes more sense, now.  but, if i were going to attempt to bypass a speaker's original x-over, i likely would not try to emulate the original's x-over points/slopes.  seems to defeat the purpose, imo - i would try for much steeper slopes, and perhaps move the x-over point, either up or down, depending on drivers and where original slope is.  i do agree  it isn't a walk in the park.  having something like a deqx, w/active dsp as well as active x-over, makes it easier, tho.     

yup, that's a green cheek conure.  she's never really happy unless she's on you...


doug s.

[carusoracer]

Wow that's one hell of nice picture of your bird

I'm trying to attempt the same in Bi Amping my HT3's. I wanted to experiment with the Jolida 302b on the top and run thre the Minimax Pre and use the AVA on the woorfer section. I was hoping that the volume control on the Joldia with some experimentation would a least get me in the ballpark