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In Reply to: RE: Biamping KEF 107/2s posted by dbphd on August 04, 2012 at 18:18:56
Use identical amps. Two identical stereo amps or four identical monoblocks. Makes things easy that way with no need for gain balancing and no worry about differences in "amp sound" changing speaker voicing in the crossover region.
That said, some like to put a beefy amp on the low end and a more "refined" amp on the high end.
Cheers,
Presto
Follow Ups:
That's how I prefer to power my system (two stereo amps). And as hahax says below, each power supply only has to deal with the bass demands of its own channel, not two (the mids/highs are nearly irrelevant compared to the lows). Another benefit is that what is output from the amps has the same channel seperation as what is output from the DAC (as long as the volume controls are mono, which mine are).
If you biamp with identical stereo amps do it with vertical biamping rather than horizontal. That means one stereo amp per side, one channel for the bass, the other for the mid/treble. It allows the bass to effectively have a 'bigger' power supply(assuming a conventional single power supply for both channels) because the upper frequencies use less power.
hard in the bass. With a shared power supply bass signal demands can easily affect the entire sound, right up into the treble.
Indeed, horizontal is what KEF suggest/expect, and also what I found to be the case with spkrs of similar sensitivity but deeper unequalised bass, and of higher efficiency 91db/w/8ohm load. The Kefsr are 90db/w/4 ohm load
I don't recall if the 'conjugate impedance-Eq xover' on the Kef's also flattened the bass-port impedance peaks. But the bass signal demands wouldn't be much effected by that, anyway
I often wonder if those who went to a bigger amplifier instead and sold the matching power amp they'd bought ever tried horizontal bi-amping?
IMO the only value of vertical is that the wiring is tidier.
Of course if the two chassis had two separate power transformers, or split windings, then we're back with 4 mono-blocks anyway, and each PSU and amplifier channel is isolated.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Excellent food for thought.
The vertical approach may have another advantage... by using two stereo amps, you change the WAY crosstalk affects the system. With horizontal, the crosstalk affects the CHANNELS. With vertical, if affects the BANDS. One could theorize that the detriment from crosstalk in the crossover region could be less important than removing inter-channel crosstalk and making imaging even more "precise". We're really switching certain advantages and disadvantages with the vert vs. horiz. arrangements. Which produces the overall subjectively better should could actually vary depending on strengths and weaknesses of the speakers involved - or even the general type of music the listener in question is into.
I still like "monoblock with it's own supply per channel per band" thinking.
It's so extreme it's GOT to be audiophile. It's GOT to be good.
Separate circuit from the panel, each with it's own power conditioner too!! Woo hoo!
Cheers,
Presto
with the actual nature of the signal, and acoustic results when we listen at home.
Even in a good say coincident even sound-field mike recording, the total signal even through n-speakers is STILL mostly mono. The difference signals are small and for us the critical factor is their mids and higher, in those channels so that we get a sound field. JBTW position is orthogonal to music. IE Phase, timing, and FR are aspects of the same signal not separate.
What I'm focussed on is how hard a system is working and how to make that as inaudible as possible.
This is a hobby about the small stuff, which is crucial, so maybe it's not 'small', eh?
Bass instruments still have overtones and they do more to tell us how they are played, and how they are being reproduced.
I bought the vertical argument and went with one channel of my modified LEAKS in triode mode. They have seriously large PSU's for baby valve amps at over 20 joules each. Then the designer of my speakers reminded me about how Linn/Naim systems were always done horizontally and that I should try it, even just bi-amped ones. S'nap.
Given their task and PSU reserves both amps were loafing (into an easy non-reactive highish/efficient and sensitive load.) Yet one way around the sound was a lot nicer! The only real difference is the task the PSU's faced. One had to work hard but we minimised its impact on the total sound. The other PSU whose impact on the total sound was empirically potentially far greater was having a very easy time.
The only valid distinction between vertical and horizontal as terms is that in one we ask each PSU to deal with the demands of a full range signal one supply per speaker, and the other we isolate each PSU to lows or to highs.
That is, a single PSU for each power amplifier is neither horizontal or vertical, no matter how many chassis we use or how they're wired, it just is multi-amped. yes/
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
I'm not obsessing, I am speculating.
I fully agree that the division of bass currents between amps is beneficial. Actually, *channel* separation is improved as well. You have a completely separate amp for left and right channels all the way back to the wall plug. You could even go as far as to keep the circuits separate back to the panelboard (with one circuit per amp). Interchannel crosstalk is now moved between bands.
You get the benefits of bi-amping, the benefits of dividing up the bass current to both amps *and* the benefit of having what amounts to "dual channel monoblocks".
Horizontal is now the orientation that seems... silly!
Cheers,
Presto
Interesting. It makes sense from a power consumption standpoint.
Does one not lose the improved crosstalk from having separate power supplies for low/hi in the horizontal bi-amp though?
That would make for an interesting A/B comparison, or H/V in this case hahaha.
Cheers,
Presto
JBTW differing power outputs in two stereo power amps only matters - for passive bi-amping - if their voltage gains don't match.
And in any case the mid-treble amp is not going to be working hard at all, so lower power consumption there, no?
:-)!
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
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