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I've been planning to use true-biwire (separate cables to LF and HF sections of speakers) between a Proceed Amp 3 and KEF 107/2s. But if I'm running two cables, why not biamp? According to the Proceed HPA3 manual that extols the virtues of biamping, the speaker's crossovers continue to distribute frequencies to the appropriate drivers. I'm intrigued by the concept of biamping, but I'd hate to blow a HF driver in a 107/2. I've sent email to KEF.
Anyone with experience or advice regarding biamping?
db
Follow Ups:
Which expects/suggest you use horizontal bi-amping, one stereo amp for bass and a matching amplifier for mid and treble. There are good reasons for this, see my post below.Do you still have the Kube line-level Eq box, as well? if you have you may be able to use it with differing amplifiers, IIRC. If not you won't get down to 20hz, more like 40hz IIRC.
Use the most powerful amp for the bass.
I'd also consider upgrading the Kube with better chips, and a better PSU.
I sold a few 107/2s.
Oh yes, one last thing, passive bi-amping can create extra earth paths, and a bit of crackle or buzz through the spkrs, running one piece of wire between a -ve terminal on one amp to one -ve terminal on the other amp will nail that problem.
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.'
Edits: 08/05/12 08/05/12
Thanks, Timothy, for the pointer to Section 3.2.2 of the manual. I must have skipped over that section. Obviously KEF anticipated that the 107/2s might be biamped. I'll try the horizontal connection KEF shows in the schematic.
db
I found bi-wiring with a better amp rather than more but lesser amps results in better sound.
I agree. If you are going to stay with passive bi-amping and spend money for additional amps you would be better in getting a new single amp and biwire. I have tried both passive bi-amping and a better single amp and always prefer a single amp. If you want to actively bi-amp then that is another story all together
Alan
In the case of the KEFs in question in this thread, the passive crossover also equalises flattens the load presented to the speakers (conjugate loading IIRC), also s in many high-end passive spkrs Eq's the drivers raw responses, before applying (or as well as applying) suitable electrical slopes which will give the (often different order) desired acoustic slopes.In fact by the time this model came out KEF were using computing and measurement to do all three jobs, trying to minimise parts count, and maximise quality.
Please both of you, do tell us, and the OP, where to go to find a tame and cheap techie with i) equivalent measuring gear and chamber to KEFs and ii) equivalent judgement to iii)design an active crossover to replace the existing passive circuits. So that your active bi-amping mantra - will - be an improvement.
IMO if you wish to comment on a proposal by an OP you should find out what the actual particular case is, before simply repeating a mantra that may not be applicable. Neither of you bothered to do any of that.
Very few high-end full-range speakers have the same crossover in each serial number let alone across each pair. Yes?
Did both of you try both kinds of passive bi-amping? In each case clearly distinguished please, what differences did you note?
And when you both went active on an existing high-end Mfd spkr, at least one I hope for each of you, how did you both match the Mfrs original crossover slopes, FR Eq and inductance eq?
And how much did it all end up costing?
EMWTKnow.
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.'
Edits: 08/05/12
Forget equalization and impedance compensation for a second... how about basic things like filter Q? Yes, some guys will pull their LR24 PA crossover out of the closet and bi-amp a speaker because they know the crossover point and relative levels of the drivers involved. But this creates a whole new speaker.
Yes, you need a guy who can measure (and properly interpret measurements) to do a passive to active conversion. As far as how close you'd need to match the existing response curve, some would say +/- 0.1 db but I think this is to associate much higher sensitivity to changes in SPL than the human ear is capable of. Some people can't tell when a tweeter is wired antiphase with a significant null!
In any case, you're right. Many say that passive bi-amping is a waste of time but I don't think this is necessarily the case. I think many advocates of active crossovers think passive crossovers in general are a waste of time, so bi-wiring/bi-amping makes no sense to them in the passive domain at all.
There are obvious benefits to manipulating which currents the amps see, and separating bass current from high frequency current, and doing it in different ways (horizontal, vertical, and even quad monoblocks).
Cheers,
Presto
Cheers,
Presto
? see below.If you did, did they sound different? IME they always do, with horizontal sounding much better, like it should. That's with matching amps each with a single shared power transformer.
And, how much more powerful was/were the bigger amps - in dbw - than the two matching amps totals in dbw? Twice as powerful is 3dbw extra.
e.g. two 100wpc amps as against one 400watt amp which should have 3dbw more headroom into the same spkr.
How many bi-amping 'cases' were involved?
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.'
Edits: 08/05/12
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
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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