Big 2 channel Amp OR Smaller 6 channel and TRIamp?


Speakers: High end w/TRI-AMP binding posts.

Which amp scenario would you choose?

A - 2x300W Discrete Amp, use jumpers to connect 3 posts together on each side and run 2 speaker wires to each speaker.

B - 6 or 7x100W Discrete Amp, no jumpers, run 6 speaker wires to each speaker.

Speakers are KEF Reference 203.1 but that shouln't matter for discussion sake. The above scenarios could be applied to biamp speakers as well.
vintagegroove
Same old, same old. (A) without doubt.

With scenario (B), your woofers would see only 100w.

Kal
1. Depends on crossover points.
The 50:50 energy point is about 350hz.

2. Can the amp make full power with 6 channels driven, or more likely, somewhat less than rating.

Depending on cross over point and amp permitting, you may even want to bridge a pair of channels for the lows and simply biamp.....
For the KEF Reference 203.2 (could not easily find the specs for the 203.1), the LF crossover is 300Hz in these speakers and sensitivity is 89dB/2.83v/m so the woofer eats half the power and the power rating is 50-200w. So, I would guess, again, that the 300w amp would be the more effective solution.

Kal
Kal.... What do you think about my observation (based on measurements) that the equal power frequency (350 Hz or thereabout) is not what natters? I have found that with a real music signal the peak voltage swing requirement for the higher frequency signal is only met by a power amp with substantially greater power rating than that based on equal power.
Can you explain how you reached this conclusion? AFAIK, the current (and power) required is a function of voltage swing of the source and the impedance of the load.
02-18-12: Eldartford
I have found that with a real music signal the peak voltage swing requirement for the higher frequency signal is only met by a power amp with substantially greater power rating than that based on equal power.
No question about it. As we discussed in this thread, in a properly gain matched passive biamp (or triamp) arrangement there is no division of voltages between the different amplifiers, just a division of current and power. If there were a division of voltages, it would mean that gains are not properly matched, and frequency response flatness would be thrown off.

(In saying that, I'm neglecting small voltage differences that may occur under properly gain matched conditions if a tube amp having significant output impedance is involved, AND if the speaker presents significantly differing impedances in the frequency ranges handled by the different amplifiers).

Concerning the OP's question, I would expect that which configuration would provide better overall results will depend on the specific amplifiers that are involved. But fwiw my instinct is that it is generally best to go with a less complex solution (Option A in this case) than a more complex solution (Option B in this case), unless there is a clear reason to do otherwise. Or unless there is an opportunity to try both approaches, and compare.

Regards,
-- Al
Kal... Using a stereo power amp rated at 600 wpc (and therefore capable of large voltage swing, even continuously) I monitored peak voltage while playing dynamic music as loud, or louder, than I normally would do. With this setup I varied the crossover frequency. For the high frequency signal the voltages which I saw, if maintained continuously, would correspond to power levels far higher than the continuous rms power being delivered.

People who design audio amps for 150 wpc provide power supplies that can maintain voltage corresponding to not much more than 150wpc. In my view it would be better to run a much higher power supply voltage even without ability to maintain it continuously. (This is sometimes called "headroom"). The FTC rule about power specs, and audiophile fixation on the FTC power spec, discourages such a design approach.
Headroom, of course, is not power, per se, unless it is used. So, do you think that the OP's scenario (B) is superior to scenario (A) for that reason?
How about you bi-amp, with 200 wpc for the woofers and then use a second amp for the mids/tweets and jumper them? You could, for example, get a 150-200 wpc 5-channel amp and leave the center channel idle.
Kal... I guess I would prefer option A, which, as I understand it simply means using a 300 watt amp for the speaker.

I don't see any advantage to using more than one amp unless there is a line level crossover.

Headroom reduces risk of clipping.
How about you bi-amp, with 200 wpc for the woofers and then use a second amp for the mids/tweets and jumper them?
Jumper what? Why? Cannot think of a jumper in this situation that would not create the potential for a short.

Kal

02-20-12: Kr4
...
Jumper what? Why? Cannot think of a jumper in this situation that would not create the potential for a short.

Kal
The OP mentioned that it has Tri-amp binding posts. The only way I've seen this is with three pairs of binding posts jumpered together (e.g., as with the MIrage OMD-28 which I am familiar with). When removed, the three pairs feed the woofer(s), midrange, and tweeter, respectively. So I'm saying remove the jumpers between the woofer and midrange, but leave the midrange-to-tweeter jumpers intact. Then use one amp to drive the woofers alone and a second amp to drive the mids/tweets which are jumpered together.

If the factory jumpers are one-piece bars that connect all three, remove them and insert jumpers to connect only the mids and tweets.
Sorry. I forgot about the OPs three pairs of terminals and was trying to fit your suggestion into 2 pairs.

Kal

02-20-12: Eldartford
Kal... I guess I would prefer option A, which, as I understand it simply means using a 300 watt amp for the speaker.

I don't see any advantage to using more than one amp unless there is a line level crossover.

Headroom reduces risk of clipping.

Well, there's still an advantage to bi-amping straight into the speaker's passive crossovers because bass-heavy passages still won't use up all available power and current, leaving little for the mids and tweets. With a separate amp for the woofers, the mids and tweets have a fuller dynamic range unhampered by power and current being siphoned off by the needs of the woofers.

I have had a pair of dual-terminal Mirage M5si's for nearly 16 years, and have ampified them with a wide variety of configurations. I've tried everything but line-level crossovers. Passive bi-amping with high-current amps has the most speed, transparency, frequency extension, and dynamic range, especially compared to single-amping, though bi-wiring helps.

Even if you decide on a single high-powered amp, you should probably still bi-wire and maybe even tri-wire.
Just get a big enough amp. That's all.
If you want a 6 channel amp that'll actuall deliver all it's rated power into each channel, it'll cost you. Bryston make theirs with a seperate power transformer for each channel. Some others probably do too, but that's the only one I know of. I have researched many multichannel amps, so I'm not too sure who makes what other than Bryston.

If the sonic improvement is worth the expense is a personal thing; depends on ears and wallet.