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Am I nuts? Biamping question...

Hi,
I'm new here and a bottom feeder in the world of high end audio (read as "poor musician") I am upgrading my studio. I have PMC FB1's (150W) I just purchased thru Audiogon. When I pulled my 1979 Roland spa-240 amp out of storage (I've been using active monitors: Event Tria) and hooked up the FB1's they sounded superb. Two days later one channel of the amp fried - I'm guessing deteriorated caps. So I started shopping. I am considering a pair of Hafler P7000's to set up a biamped system, but those amps are WAY overkill power-wise. Am I nuts to use such amps with these speakers?

The other option I am considering is using something more reasonable like P3000's in a vertical (pseudo) biamp setup. Do the differences between "true*" and "pseudo" biamping justify the use of the P7000's? I have never done "true" biamping before, only pseudo. The P3000's and the P7000's are the same price.

I know I'll need to make custom crossover cards for the P7000's - no biggie. The FB1's crossover is at 3k. I intend to set the low pass at about 3.5k for the woofers, and the high pass at about 2k for the tweeters.

I am trying my hand at budget mastering aimed at indie musicians. Any help is appreciated.
-jim
http://www.fixthatmix.com

* I know that "true" biamping involves removing the speaker crossovers - not something I'm interested in at this point. I believe my plan will yield the benefits of true biamping without screwing with the speaker design. Please tell me if I am wrong.
jimbo_9er
jimbo_9er OP
3 posts
 
Hi Kal,
Thanks for the feedback. The x/o's in the P7000 are before the power amp section. I don't think that removing freqs below 2k in the signal to the tweeter (and its x/o) would have a negative effect, but that is why I posted here. The speaker x/o is at 3k, and there are separate x/o's for each driver. Thanks again for commenting.

BTW - My reasons for wanting to do this include: avoiding burning up all that low freq energy in the tweeter x/o, and cutting distortion in the amps. I am not arrogant (enough ;) to think I can set up a true biamp and improve on PMC speaker design.

-jim
kr4's avatar
kr4
3,680 posts
 
Still the same. Cascading two crossovers creates phase and level problems. Use one or the other.

Kal
butsy
23 posts
 
I believe the improvement of bi-amping in a speaker like yours would be minimal. Try it with one amp first and if it sounds great ,,leave it alone (for now)!
horseface's avatar
horseface
222 posts
 

I had a Yamaha pro setup for a while with JBL 18" bass cabs, 15" JBL mid cabs and a set of Klipsch LaScala's. I was running one of the big pro Yamaha amps (350 wpc), a smaller Yamaha amp for mids and a Peavey CS-1000 for bass. I had the 18" subs (2245H) wired in parallel and the CS-1000 running mono. I bought an three way Ashley crossover.

To make a long story short ... It sounded like crud. No matter how I tried to dial it in ... when I dumped the Ashley and ran the built in passive crossover's it got a lot better.

For what it's worth - I think Kal's got a point. I do like the idea of bi-amping however. I'm running a small and large Mark Levinson amp in my 2 channel room and have the jumpers removed on my Aerials. I like the passive crossovers.

Pretty fantastic ...
jimbo_9er OP
3 posts
 
Thanks for all the responses. This is a great forum. The FB1's sounded lovely with my old Roland power amp. I might experiment with the biamping* and run some sweeps to see what is happening to the freq response and sound, before selling the second amp. (It's in my nature to test things for myself. It doesn't mean I'm ignoring the advice here - just attempting to verify it) My room is charted from several well defined reference positions. Everything I have read indicates that bypassing internal x/o's and attempting to biamp a system not specifically designed for it, rarely if ever works well. Your experience Horseface, seems to follow that pattern.

In reading the responses, I realized that I had been careless in my thinking. The tweeter's signal only decreases at 12 db/8va below 3k. At 2k there would be a lot of overlap between the x/o's. A better target freq for the amp's high pass x/o would be something around 200 where the overlap in the 2 x/o's would be minimal, but then there's the phase issues Kal mentioned.

*The amps come as a pair. I expect to sell the 2nd one after some playing around.
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