Freaky speaker experience:

I have the Nuforce 9SE pre's and amps. I had them attached to my Focal JMLABS 936; bi-wired at the speaker but single ended at the amp. They sounded soooo crappy (tinny, bright, fatiguing) that I was ready to toss them off the second floor window. :) Could'nt understand. For kicks, I single wired it using the original jumpers. Now they sound awesome. About 10 cd's later still awesome.????? They sound different but as good as my Totom Mani's. Any ideas about the bi-wiring? Too much juice going to the high end?
The placebo effect works both ways.

Did you single wire w/same cable or use a different cable?
Plus, my wife hears the same thing. Same albums. I go back and forth between my Totems and these. Before I added the jumpers we both disliked the Focals. Now, we are feaked and stunned. We don't understand.

I also am not ready to sell the Focals now. I would have given them away two days age. But I want to make sure it isn't my imagination..... Placebo......
Sometimes less is more...

Decent jumpers allow both speaker terminals to look like a single electrical connection (almost) while with a bi-wire you are at the mercy of the "voicing" introduced by the additional wire. I am guessing in your case the speaker wire used is not the best match which became obvious in the bi-wire set up.

Had a similar experience once (lost 1/2 the bass) with bi-wire went back to original jumpers and was happy again!
switch back to bi-wire and see if you still notice the effect
bokfudo has this figured out...the 'feature' of bi-wiring does not guarantee any improvement.
Had the same experience with a pair of Avalons back in the 90s..never knew why
Any chance you had one set of drivers hooked up out of phase?
I'll second Rleff. Sounds like one of the woofers was out of phase. If everything appears connected right I might go so far as using an ohmeter and checking the cables.
If she's game, perhaps your wife could change from single to bi-wire a few times without letting you see. She should also not change them at all, just pretend to, a few times. Then do the same for her.

I'm open to there being a real difference with bi-wiring (that couldn't be achieved with a single run of the equivalent gauge of a single wire), but I've never heard a convincing explanation for why there might be a difference. The explanations always sound very hand-wavy to me. I'd like to seem some actual math.

Even so, I made some "true bi-wire" cables for when my new Vandersteens come. Cost for materials was under $40. By "true" bi-wiring, Vandersteen means keeping the two runs separate by at least an inch instead of having them in the same jacket. But I did this more because I could than because I expect to hear a difference.
I'll third Rleff.

-- Al
07-07-09: Kr4
The placebo effect works both ways.

To hear an effect that is the exact opposite of what is expected is an indicator that the placebo effect is not at work, and the reality is overwhelming the expectations.

If the placebo effect worked both ways, then the placebo control in medical double- and triple-blind studies would be unreliable for setting the statistical baseline.
I am going to have my wife try and trick me by bi-wiring and not bi-wiring; good suggestion. I want to make sure this is real. Plus play more music. But it was such a change that I believe it is real and not what I hope is real. I hated to think that I had to sell those huge heavy things in this market.....

No I tripple checked and the wiring has always been in phase.
Did you go back to bi wire to see if it happens again?
Al- in your opinion when the speaker jumper is removed to bi wire would that change driver impedances the amp sees as now the crossover is presenting different cap and inductor values to the amp driving them which happens to be the same for both woofers and high frequencies;maybe that seperation of the drivers is causing a strange impedance presentation to his amps? Just a thought.
i had the same experience happen to me with my infinity renaissance 90's, when i was buying speaker wire i wanted to get two identical sets so that they would sound the same so i spoke with the manufacturer before buying the wires and he told me that when you bi wire the current of your amp gets divided between the two wires and that only half the current would get to the woofers and half to the highs and he told me that he does not like to bi wire speakers, of course i did not believe him and bought the two sets of wires so that i could bi wire, well i have to say that the speakers had more detail and sounded clearer but they lost most of their dynamics and had no punch, i hated the sound of them, i too liked them better with a single wire, i though that maybe speakers that are harder to run ( need more current) like the ren 90's sound better with the single wire and maybe the manufacturer was right in that the current gets divided between the two wires when bi wired, then i added a second amp and bi amped the speakers and what a difference, they sound clear like when they where bi wired but now have all the punch and dynamics you could ask for, i could not believe the difference i was hearing, if i where you i would try to bi amp your speakers you won't believe the difference.
Rleff -- Interesting thought, but I wouldn't think so. From the amp's perspective, the speaker load impedance should appear to be the same in both cases, with the VERY slight exceptions that:

-- The total wire resistance and inductance, being greater in the non-biwired configuration, would cause the amp to see a VERY slightly heavier load in the biwired configuration.

-- The amp would see a VERY slightly greater amount of load capacitance in the biwired configuration.

-- The amp would have to deal with a VERY slightly greater amount of back-emf from the woofer section in the biwired configuration, because a VERY slightly greater fraction of it would be absorbed by the high frequency section of the speaker in the non-biwired configuration.

But I would think that all of those differences would be extremely minute, probably not audible at all, and certainly not enough to account for what Cepages seems to be describing. And having the amp deal with woofer back-emf, rather than the mid/tweeter parts of the speaker, normally improves rather than degrades the sound.

In saying these things I'm assuming, of course, that the wires do not have extreme, outlandish values of either resistance, inductance, or capacitance.

Greg said:
he told me that when you bi wire the current of your amp gets divided between the two wires and that only half the current would get to the woofers and half to the highs

He mis-stated that to you. What happens when you biwire is that the low frequency part of the crossover network in the speaker, being in series with the low frequency wires between the speaker and amp, keeps the high frequencies from going through the low frequency wires. And the high frequency part of the crossover network in the speaker, being in series with the high frequency wires between the speaker and amp, keeps the low frequencies from going through the high frequency wires. The result is less interaction between high frequency and low frequency currents, which normally results in a slight benefit. Also, as I noted above, back-emf from the woofer is conducted entirely to the amplifier, rather than some fraction of it being conducted to the mid/high speaker elements.

It's easy to understand how bi-wiring can result in either slight improvement or no improvement, but frankly I have no idea how it could result in significantly worse sound (assuming, again, that the cables have reasonably conventional parameters).

-- Al
So cool that your wife is going to conduct this experiment with you. I would get the "oh, my husband's an idiot sigh". Any results yet? I have Forests and have not bi-wired.
great point Al, but what i don't understand is why then when i added a second amp, two pass lab x-250's, the speakers had way more dynamics and punch, the bass from the woofer was much tighter, quicker and more controlled and the transaction into the midbass was smoother giving the speaker a warmer and fuller sound quality that i like as compared to when i had them bi wired they sounded much like as cepages describes, also when using the two amps there is a noticeable improvement in the midbass driver as compared to using one amp bi wired, i would think that by using two amps there would be more current to power the woofers because the amp no longer has to power the mid bass, midrange and tweeter and the second amp would power the mid bass, midrange and tweeter much easier too, makes me wonder if the guy who sold me the speaker wire was right about the current dividing in the two wires when you bi wire as two amps sound so much better than when you use one, anyhow for me it sounded better with using two amps, just my thoughts.
Hi Greg --

Biamping, as you no doubt realize, is simply a whole different thing compared to either biwiring or single-wiring from a single amp. It has lots of potential benefits, and a search of this and other forums will turn up lots of interesting reading on it. Although, of course, some of the advantages that are often mentioned for biamping only apply to active biamping, where an electronic crossover ahead of the amplifiers replaces the passive crossovers in the speakers. But "passive biamping," which I suspect is what you are doing, has lots of potential advantages, too, which biwiring doesn't provide.

Not sure if you are doing it "vertically" (one amp driving the highs and lows of one speaker, and the other amp driving the highs and lows of the other speaker), or "horizontally" (one amp driving the lows of both speakers; the other amp driving the highs of both speakers). The noted designer Steve McCormack has made the point in posts here that the vertical arrangement is probably preferable because in that arrangement each amplifier sees an identical signal at both of its inputs. That eliminates possible interactions within the amplifier between channels, via power supplies, grounds, and other paths, that can impact the sound when a single amp is handling two different input signals for two different channels.

In either arrangement, biamping reduces or eliminates the possibility of interaction between highs and lows in the amplifier output stages; it provides more total power; it presents each amplifier channel with a less complex load; and there are undoubtedly other advantages which I'm not thinking of right now. As I say, its a whole different thing compared to bi-wiring, which just basically separates the highs and lows so that they travel through different wires.

Best regards,
-- Al
very interesting, thanks for the info Al, the amps in my system are set up horizontally, i will have to try setting them up vertically one day to see what it sounds like.
In the second of my posts dated today (July 11) in the other current thread on essentially the same question, I propose the following explanation of what I think is going on here:

Here's a theory I just thought of: You are not really losing bass in the bi-wire configuration; you are just getting better bass damping (meaning tighter, more well-controlled bass), for reasons I'll explain below. That would very conceivably produce the slight measured loss in bass response that you have found (I presume using test tones), and on musical material could very conceivably produce a subjective impression of less bass.

The reason that may be happening is as follows:

In the bi-wire configuration, back-emf from the low frequency drivers is conducted directly (and only) back to the amplifier, which in your case has an extremely good damping factor (i.e., an extremely low output impedance). So the back-emf is absorbed there very effectively.

In the single-wire configuration, some small fraction of the back-emf from the low frequency drivers is conducted through the jumpers into the mid-frequency drivers, where it will not be effectively damped (because the impedance is much higher than at the amplifier output), and, more significantly, WHERE IT WILL PRODUCE SOUND THROUGH THE MID-FREQUENCY DRIVERS, ADDING TO THE SOUND PRODUCED BY THE LOW FREQUENCY DRIVERS.

So you may indeed be getting measurably more bass in the single-wire configuration, but bass which is the result of back-emf effects and is therefore less accurate!

And of course that loss of accuracy in the single-wire configuration (relative to the signal going into the speakers) may be subjectively preferable if it offsets inaccuracies which may exist elsewhere in the system, the room, or the source material.

-- Al