2. amps-preamps
  3. 1131913685

Bi-Amping

Hi everyone,

Well I steped up to dual power amps and bi-amping my custom made (self built) speaker system that I have finally finished- Cerwin Vega 15 inch subs, Vifa 8" bass and 6.5 Mid bass, dual Vifa 3 inch SoftDome mids, with a Morel 30's for the tweeter. The subs are @ 80Hz (via the B&K), the speakers are crossed @ 300Hz, 500Hz, 700Hz, and 3200Hz- 2nd order for the lows and 3rd order for the highs. One amp runs the subs and the other the speakers.

I am using two (2) Proton D-1200's, a B&K PT5 preamp, with an Audio refinement CD player. I am running Monster MCX 2s wire (4- 15' foot runs), Audio Quest power cables, and Monster M850i Interconnects, this is connected to a dedicated 20A wall outlet.

My room size is 28x14, shot gun style, painted dry wall, and half carpeted/harwood flooring, 8' room height.

My question is: I was expecting a more powerful sound then what I have presently. While everything did open up, it seems the DB output did not increase substantially, as a matter of fact, it seems I must now nearly max the volume control on the B&K to achive similar output when I was using a single amplifer. All be it, the sound is more refined and much tighter, the DB output did not increase. And I am concerned that the B&K is having trouble outputing enough voltage to run two amplifiers.

Is this the norm? Am I not suppling enough "juice" to the amplifiers via the wall outlet? Or, do I have to large a "hole" between the subs and the Speakers?

While this does sound very impressive, I am not as "jazzed" as I thought I would be.

Any ideas, comments, help?
alpha_03
rgwrjs
41 posts
 
I echo the advice about an active crossover. The difference between passive biamping, which you are doing, and active biamping is large.

Good luck
alpha_03 OP
39 posts
 
Well the B&K PT-5 pre-amp has an active Low pass section @80Hz, while the rest is thru the typical crossover network with in my speakers. Mind you it sounds very very good, I am mainly concerned with the matter of the B&K's output via a maxed volume control, the amps are not hitting peak power is my thought.

As for the Proton's - they are 110wpc, however, they are able to deliver 1500wpc transients for 200ms into 2ohm loads, or more, depending on the source material. They are very very powerful amplifiers. And with a S/N ratio of 120dB, they are very quite as well.

By way of example, I have an AB international 1100A which is rated to 550wpc, the Proton side by side (single amp) Is everybit as poweful, and, more refined. I also have an Adcom GFA-555 and the Protons beats it as well.

Again, it is my belief that the B&K hasnt the output to run two amps, but then I could be wrong, hence my question.

Thanks for the comments.
whoaru99
98 posts
 
Even with active x-overs etc. going from 100 watts to 200 watts is at best only 3dB increase. This is just past the verge of an audible increase in SPL.
whoaru99
98 posts
 
Nobody is questioning the Proton amps - I'm sure they are very nice.

Pretty much the bottom line is that the very best case only provides 3dB more volume doing what you are doing and the average case, less than 3dB. So, it is no surprise to some and no indication of a problem that you hear little difference; it is what it is and the principles of physics/acoustics/electronics are what they are.

If you want significantly louder you will need to drive the speakers with much more powerful amplification.
alpha_03 OP
39 posts
 
But I do not understand why the pre-amp needs to be cranked all the way up just to get nearly the same sound (dB) I had previously, using a single amplifier in bi-wire mode and yet the pre-amp would allow the amp to clip if I drove it to hard- (around +2 on the display) this would would be at ear spliting levels. Now, with the present set up, I can not clip the amps, even with the volume turn up as far as it will go. Mind you the B&K uses a digital volume control, and I have it set to it's maxium output of +8dB.

This is what I believe to be my problem. The specs for the B&K state 8volts max output, I wonder if this is indeed the problem?
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