Biamp considerations with 2CeSigII's and 2W subs - Danger?

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Robertsmania

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I own a pair of 2CeSigII speakers, two older 2W subs and a Sunfire TGA-5200 amplifier.

For a long time I was using the speakers connected in a biwire configuration with one channel per speaker and the X-2 filter in front of the amplifier.  I ran all the speakers from the amplifier.

Recently I experimented with running my surround speakers back on my receiver, freeing up their channels on the Sunfire to biamplify the mains.

The manuals for both the speakers and the amplifier discuss setting up this sort of horizontal biamplified configuration, but they dont talk about introducing a high pass filter like the X-2.

I have tried all the configurations - biwired, biamped with the filter in front of the amp, biamped with the filter only in front of the woofer channel - and all the combinations of the voltage source and current source outputs on the Sunfire.

To my ear it sounds best with the signal going into the amplifier unfiltered for the tweeter/midrange channel using the current source and having the X-2 filter only on the woofer channel.

The contrast between that setup and the standard biwire I had been using sounds obvious to me. 

I was very happy until I stumbled on all the negative stuff on the Vandersteen FAQ page about the dangers of biamping...

http://vandersteen.com/vandersteenaudioqs.htm
...
Answer: HELLO BOB, I NO LONGER RECOMMEND BI-AMPING OF ANY KIND UNLESS BOTH ARE TUBE AMPS. MANY SOLID STATE AMPLIFIERS ARE UNSTABLE DRIVING THE TOP OF ALL OUR SPEAKERS. THIS CAN RESULT IN AMPLIFIER PROBLEMS OR SPEAKER FAILURE. IF CONSIDERING THIS MAKE SURE YOU USE A O' SCOPE ACROSS THE OUTPUT OF THE AMPLIFIER AND LOOK FOR OSCILLATIONS ON TRANSIENTS. MANY REPORT IMPROVED TRANSPARENCY ONLY TO FIND LATER THAT THE AMPLIFIER HAS SHORT BURSTS OF OSCILLATION TRAILING ALL TRANSIENTS. 
...
Answer: HELLO TOM, THIS IS WHY WE NO LONGER RECOMMEND BI-AMPING AS THE CHANNEL THAT IS DRIVING THE HIGH SECTION IS VERY CAPACITIVE AND CAN CAUSE MANY AMPLIFIERS TO BECOME UNSTABLE.  YOU ARE LUCKY THERE WAS SUC
H AN OBVIOUS PROBLEM BECAUSE MOST OF THE TIME IT JUST GETS BRIGHTER, THE AUDIOPHILE THINKS MORE DETAIL (AMP RINGING) AND IN A COUPLE WEEKS OR YEARS THE TWEETER QUITS?????????  THE RINGING CAN PUT OUT NEAR FULL POWER INTO A TWEETER V.C. ON SOME TRANSIENTS AT FREQUENCIES NOT AUDIBLE TO US BUT VERY DAMAGING.
...
There are a bunch, just search on the page for bi-amp.

I contacted the support folk at Sunfire and asked them if they thought there was legitmate cause for concern from amp ringing or instabilty.  Their response indicated that to their knowledge nobody has ever reported damaging a tweeter with my amplifier in a biamp setup.  They said that all of their amps are tested during development with a capacitve load to check for ringing but this does not mean that the load they use will be as capacitive as whatever is in the high section of the Vandersteen crossover. It wouldn't necessarily be revealing to test it in the abstract if the problem is with a specific load.

I do not have an oscilloscope, nor would I really know how to check for the oscillations on transients as described above.


I suppose I'm okay being deluded and hearing what is actually amp ringing but thinking its more detail - as long as I'm not really risking damage to my equipment.


What do you guys think, is there really cause for alarm and biamping my speakers is asking for trouble as Richard repeatedly suggests? 

Does anyone here have experience with oscilliscopes and maybe give me advice on how to check for amp ringing if I can borrow a scope or otherwise get my hands on one?

Mr645

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Re: Biamp considerations with 2CeSigII's and 2W subs - Danger?
« Reply #1 on: 8 Sep 2012, 01:36 pm »
I have been driving my 2Ce Vandy's for about ten years bi-amped.  First with a Parasound HCA-855a, 5 x 85 with two channels to each 2Ce and the remaining channel to a 4 ohm center speaker.  Never had any issues.  At the time, bi-wiring & bi-amping were recommended by Vandersteen.  I picked up a Parasound 200x5 amp and had that in the mix for a while, but I really could not notice any difference in sound so I eventually sold the 5x200 and went back to the same HCA-855a amp. 

I even e-mail Richard Vandersteen about his change in their thoughts on bi amplification and he replied that since I have been running the same amp for ten years with no issues, obviously this particular model of amp is fine dealing with the load presented by the set up I have and he sees no reason not to continue this set up since I am happy with the sound quality.

I am currently using s Pioneer VSX-32 as a processor (previous was a B&K  Ref-20). With the B&K I used an RCA Y connector to split the front signal to the amp. The Pioneer allows me to program 2 effects  channel outputs to front outputs so I do not need the Y connector anymore.  So both the top end and woofer on the 2Ce see the same signal.  Again, ten years of great sound with no problems, so as long as your amp is working fine, I would guess it should keep doing so.

Compared to a single channel, I find that bi-amplification gives me greater sound stage, tighter low end and greater dynamics.  For music, 2 channel, I preferred the B&K but for BluRay, the Pioneer and the ability to decode the high quality surround delivers a noticable improvement.