Bi-amping Vandersteen Treo CTs


So I just got a VTL IT-85 integrated amp and am very happy about the upgraded sound with the Treo CTs when compared to the previous amp, a Cronus Magnum II. But reading the VTL manual tells me it's possible to bi-amp by adding their ST-85 power amp, which seems appealing.

Here's a quote from the Vandersteen owner's manual:

The only way to properly bi-amplify the Model Treo is passively, with two identical amplifiers in a vertical configuration. (one stereo amplifier per channel) An electronic crossover cannot be used since the crossover in the Model Treo is not bypassed. The result would be two crossovers in series creating severe phase shift. The use of two different amplifiers or an electronic crossover will negatively affect the sound of the speakers and reduce their overall performance level.
Here's VTL's take on the matter:

The best example of this type of bi-amped system would be the use of the VTL ST-85 stereo power amplifier, which has been precisely gain-matched to the signal that will be output from the preamp outs of the VTL IT-85. It is recommended that for this type of system the amplifiers get connected to the loudspeakers in a horizontal (rather than vertical) bi-amp mode (i.e. with one stereo amplifier on the bass of both channels and with the other stereo amplifier on the top of both channels). In this fashion the IT-85 becomes the central source director and volume control for the whole system.

So who's right? 
john_g
Since an electronic crossover would not be used in the configuration suggested by VTL, the Vandersteen statement about two crossovers in series would not be applicable.

Also, it is claimed in VTL’s description of the IT-85 that its "sonic characteristic ... is similar to our well regarded ST-85 Stereo amplifier and the TL2.5 preamplifier combination – fast, musical 3-D sound, and solid bass support that VTL is known for." Assuming that is a fair statement Vandersteen’s caution about using two different amplifiers would presumably be inapplicable as well.

However a horizontal biamp configuration would not provide two of the advantages a vertical biamp configuration can potentially provide:

1)The ability to place each amp close to the speaker it is powering, thereby allowing the use of short speaker cables, and thereby minimizing the sonic effects of the speaker cables.

2)Sonic improvements that may result from having both channels of each amp processing the same signal, which would eliminate whatever sonic degradation may occur within the amp as a result of inter-channel crosstalk of differing signals.

Also, keep in mind that from a subjective standpoint biamping two amps having identical power capabilities would provide just a very modest increase in maximum volume capability. (And there are multiple other issues that can arise when biamping with amps having dissimilar power capabilities).

The bottom line, IMO: It will work in a reasonable manner, but whether or not the resulting benefit would be worth the cost is highly questionable.

Regards,
-- Al

You won't be able to horizontally connect the amps to the Treo's. They don't have a separate bass and treble/mid input.
If I would trust anyone, it would be Richard Vandersteen. If you doubt me, give him a call. He will return it the next day- Personally.
FWIW, I own the non-CT Treo's and run them with Atma-Sphere MA-1 monoblocks. It has to be the most transparent sounding system I have ever owned.
Bob
Thanks, Bob. However if the speaker can be vertically biamped it would seem that it must have separate and independent bass and mid/treble inputs, and therefore should be capable of functioning in a horizontal biamp configuration as well (putting aside the question of how desirable that may be from a sonic standpoint). I don’t see how each speaker would have a way of "knowing" whether its two sections are receiving signals from two channels of one amp, or from one channel of two amps.

And looking at the paragraphs concerning biamping on page 4 of the Treo manual I see nothing inconsistent with that.

Best regards,
-- Al

@gdnrbob

"You won’t be able to horizontally connect the amps to the Treo’s. They
don’t have a separate bass and treble/mid input."

I don’t know about your Treos but the Treo CTs I am listening to right now HAVE separate bass inputs and mid/treble inputs on the back of each speaker. I am biwiring the speakers with two separate runs of Audioquest cable.

If I am misunderstanding you please explain.




I agree with almarg.  I am guessing that the Treo manual says that to dissuade people from the idea of using different amplifiers for the highs and lows (e.g., trying to get tube magic on top and solid state slam on the bottom).  I suppose RV assumes people would know better than to use different amps for the left and right channel.  :)

Good luck; great speakers you have there.
Whoops, I had a 'senior moment'. 
In the words of Emily Litella:
'Nevermind'.
the key to the debate is do the two amps have identical transfer function - you have a VERY meticusuly engineered time and phase  accurate speaker why ruin that ?
will your amp dealer let you try it out ?????



Thanks to all who responded. Helpful and thoughtful info.