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
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?
ar_t
165 posts
 
Good grief.......

I missed this first time out.........

You have an 8" bass, 6.5" midbass, and a 3" dome midrange?

There is the clue why you don't like the sound. I won't even touch on the mish-mash of crossover points and slopes.

Go ahead......hate me.

After you get over hating me, seriously consider going active. I suspect that you will enjoy twidling with an active crossover. Much easier, and therefore more gratifying, than twiddling with caps and coils.

Cheaper in the long run, also.

I have built custom made crossovers, but they were all "twiddle-proof". It is too tempting to twiddle with them, and one can waste a lot of time twiddling and making things worse. Lots of fun, but not always a step in the right direction.
alpha_03 OP
39 posts
 
LOL, well I am not one to hate anyone, I appreciate your.....comments. However, you can, and may, snub your nose at my set up- but I would challenge you to a listen before you condem what I have built. With that aside, I enjoy the sound, as do every friend I have, some have better systems and say mine sounds better. But again, as previously stated, I believe the power output is limited due to the B&K's 8volt output. One listen to Rush's Red Barchetta, or Tchaikovsky's 1812 Overture, or Yanni Live at the Accropolis will instuct you as to the performance of a multi driver, extreamly low bass, done right system that can only be recreated using many drivers, not your typical 2 or 3 way system, but then the experts over at Wilson Audio have no clue why they use multi driver systems do they?

I have verified the problem - finally - I borrowed a Luxman pre from a friend that has a pre level sub out @75Hz- I believe, and I can now cause the amps to reach full power and clip, while the B&K sounds better, the Luxman gets much louder.

While I am no fan of bleeding ears, I am going to call B&K and see what can be done, if anything. Maybe I have a defective pre amp, who knows? (as of yet)

Again thanks for your comments.
kr4's avatar
kr4
3,672 posts
 
8 volts should be enough to drive any amp or pair of amps into clipping. Take a look at the amp's sensitivity rating; it's usually around 2V for full output.

Kal
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