bi-amping worthwhile?

[jdm56]

I've been playing around with different amplifier configurations and have developed some questions and some observations. First the observations: The amplifiers in my receiver are really pretty good, or else the amplifiers in my old Sony ES power amps are not that good. Take your pick. The upshot is they sound much more alike than different. In fact, I think I'd be hard-pressed to tell any difference at all! (darn tin ears!)

The real world sonic difference in 100 watts and 150 watts (or for that matter, 10W and 1000W) is pretty much nil, unless you are actually bumping against your dynamic limits with "merely" 100W.

I don't really listen to music that loud, according to my trusty old RatShack spl meter. Very, VERY rarely do I ever peak over 95dB, even when "jammin". Probably 75% of my listening is in that 85-95dB range. Subjectively, loud, but not over-bearing. So, even with my current "low-efficiency" speakers (90dB-1W@1m), I'm rarely asking my receiver to deliver more than 10W.

Question time: Which is "best", and why: driving a pair of speakers with say, one 250W/channel amp, or bi-amping the same speakers with 100W/chl on the mid/tweeter and 150W/chl on the woofers?

As far as value, isn't a good powered sub (or two) much more worthwhile than bi-amping a stereo pair of towers?

[colterphoto1]

bye

[docfi]

The main benefit of bi-amping is the use of an electronic, line level crossover that splits the audio signal (typically with an 18 or 24dB/octave roll off) into two frequency bands before the signal gets to the amplifiers. Subsequently, the need for the speaker to have its own internal passive crossover is eliminated. A speakers crossover is, arguably, the weakest link in a speaker design, lending to lower efficiency, poor amplifier damping and phase shifting to name a few drawbacks. Most people are not willing to spend the money on an active crossover and two amplifiers, but the for those who are the audible improvement is substantial. The trend over the past ten to twenty years is towards the powered subwoofer which contains an active crossover and an amp dedicated to the subwoofer driver. This still leaves the passive crossover in the main speakers though. I do not know if youd consider this to be a truly bi-amped system.

Here are some links:

http://sound.westhost.com/biamp-vs-passive.htm

http://mitglied.lycos.de/Promitheus/active_crossovers_in_speakers.htm

[jdm56]

I guess I should clarify: What I've been doing would be called "passive" bi-amping, through the split cross-overs in the speakers. True, this is not the same as "active" bi-amping such as could be accomplished with outboard electronic cross-overs, but there are still some potential advantages. I'm just not sure the advantages are worth the extra hardware and cost.

The benefits: Protection of the tweeter, by keeping potential distortion from an over-driven (clipped) woofer amp out of it; Ability to use, say, a tube, mos-fet, or class A amp on the mid/tweeter combo, while using a beefy A/B solid state amp on the woofers; and just the ability to put more power to the speakers overall. But this is where my question comes in, so I repeat: Which is best, the single 250W/channel amp, or splitting the crossover and using a 100W amp on the mid-tweeter combination, and a separate 150W amp on the woofers?

[colterphoto1]

forget it

[jdm56]

Uh yes, there certainly is something called passive bi-amping. Look it up, dude! When you split the crossover at the speaker terminals by removing the jumper between the two (or three) pairs of input terminals, you can use multiple amps, which is what I have been doing.

By the way, nobody asked you to "explain it".

[dkp]

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The real world sonic difference in 100 watts and 150 watts (or for that matter, 10W and 1000W) is pretty much nil, unless you are actually bumping against your dynamic limits with "merely" 100W.

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I have to humbly disagree with your statement that an additional 50 watts would provide no real advantage unless you are really cranking the volume (my words). I previously owned a B&K 307 receiver which puts out 150 wpc and just upgraded to separates at 200wpc. I heard the difference between the two immediately. I had always heard that RF-7s didn't need a sub if they had good amplification, and I can now attest to the truth behind that statement. I haven't been in the hobby long enough to give a good technical answer to why this is so, whether it was the addtional wattage or current of the amp, but I can tell you that the difference was nothing short of spectacular. I would guess that you may be partially right as my assumption is that I now get better sound due to the higher current amp.

[jdm56]

I'm talking mainly about an audible difference due to output capability. The output difference, expressed in dB, between 150 and 200 watts is exremely small; only one dB, in fact. Just perceptible. Now, what you were hearing may well have had nothing to do with peak power output. Personally, I'm not convinced of any gross audible differences of properly functioning power amps, but I would not dispute what you heard. Maybe it was a difference in the amps ability to deliver current into low impedence loads, but I was of the impression that the RF-7's impedence curve was pretty mild. Maybe it has more to do with that "first watt". Shoot, it could even have been due to the new pre-amp. I dunno.

[dkp]

Maybe more will jump in this thread and answer the questions...

I should also point out that I was not pushing the amp at all-the difference was apparent even at low volume. Additionally, the B&K Ref 31 was sent back for warranty work for about a week during which time I used my Yamaha 5560 as a pre-amp. While I did not like the sound of the Yamaha/B&K combo as much as my B&K 307 receiver, the difference in bass response was also immediately noticeable and better than the 307 unit alone (even at low volume). I know I'm not answering your question, just clarifying my situation.

David

[Daddy Dee]

I haven't biamped, but have been curious about it. Also stayed in a Holiday Inn Express last night, so here's what I think.

jdm, I think your instincts are probably right in wondering if investing in a nice sub wouldn't be better than getting into biamping.

While it sounds interesting, in principle, what it takes to actually accomplish biamping in terms of gear and practice, (expensive and too much like work).... this has cooled my jets as far as wanting to pursue biamping.

I realized it was well beyond what I wanted to spend or put into sweat equity. That is certainly a subjective call. Some people really love their results. Just hasn't been attractive to me.