Why am I experiencing listener's fatigue?

Have you tried to bi-wire the speakers with a different bi-wire speaker cable instead of running single with jumpers?
I have N803 and they are pretty bad when used with single run sp cable. I tried with different single run and bi-wire sp cable and with speakers on single run sp cable, I get tired really quick. I since have them bi-wired and no problems. I think B&Ws like to be bi-wired, regardless of the model. The jumpers they include with their speakers are nothing to write home about either. Also I have my speakers toed in so that tweete axis meets about 1 foot in front of me. I also listen near field, so that may be an option as well. FWIW. good luck

Hope you're OK man! It'd be a shame if the speakers did it to you... but I don't think so. Here is what I think about bi-wiring the B&Ws N803(I know you have the 805, but I think it applies). First thing that I notice when listenning with a single run is fatigue. What happpens with B&Ws, they just midrange like MOFOs when run with single sp. cable. It brings the midrange to a point where it is undigestable. My ears hurt. I immediately switched to bi-wire and it's a totally different sound now. Fatigue is gone and speakers just sound right. Much smoother throughout the whole spectrum. After you get checked out by your doc, and I really hope you're OK, is to go to the store where you usually buy your hi-end stuff, or at least where they know you, and get them to give you for home audition, some bi-wire sp cable. Make suer you get something good though, I'd say at least Monster M2.4s. B&Ws like a big fat speaker cable with as less of resistance as possible. I went to Stereo Exchange in NYC few months ago and listened to a system that consisted of McIntosh Integrated amp(I think it was like $6000 or something), Arcam FMJ CD33 player and B&W N805 speakers. Dude, I have the N803 and I did not know that the N805 can sound that frigging good!!! All was wired by Monster M1000 ic and Monster M2.4s bi-wire Speaker cable. I know the sales guy there since I bought a lot from them, they let me listen to whatever I want and as loud as I want to. I was in that room for almost 45 minutes, had no fatigue. But anyway, please let us know how this works out for you, most importantely your ears!!! Best of luck.

Oh...also, in your room it might be different with toe in. I said about a foot in front of me but I did check and they just cross in front of my face, not a foot, but may be 3-4 inches in front of me. But you know you have to experiment. And the funny thing is, when you move the speakers, the cables get moved as well, right? That is what you also have to consider - after you move the speakers, have them play for about 45 minutes to an hour before you evaluate them again. I noticed in my system that's the case - speaker cables need their time to come back to life again. May be that sounds crazy, but just what I observed in my system.

from the manual for N805... same as on my manual for N803. They recommend shotgun bi-wire cable. Which I think is the way to go. Check it out.
"All connections should be made with the
equipment switched off. There are 2 pairs of terminals at the back of the speaker to permit bi-wiring. The lower
pair feed the bass/midrange drive unit and the upper pair feed the tweeter. The terminals are insulated to prevent any likelihood of electrical shock, even when the speakers are used with the highest powered amplifiers, and accept a variety of cable termination to suit most applications.
Bi-wiring is the preferred method of connection and involves the use of separate cables from the amplifier to each pair of terminals. The separation of the signal paths improves the resolution of lowlevel detail and allows the user to optimise the type of cable to the frequency range of use.

Should you not want to bi-wire, perhaps
during the initial set-up procedure or
because you do not want to see a
multitude of cables in the room, short
cables are provided to link both positive
and both negative speaker terminals
together.
When using the links, insert the spade into
the slot in the side of one terminal and the
crimped pin into the round side hole in the
other. There is enough clearance to insert a
spade connector from the amplifier into the
same terminal as the crimped pin.
Ensure each positive terminal on the
speaker (coloured red) is connected to the
positive output terminal of the amplifier and
negative (coloured black) to negative.
Incorrect connection can result in poor
imaging and loss of bass.
When bi-wiring, do not use the linking
cables. Take extra care with the polarity of
the connections as incorrect connection
can also impair the frequency response
through the bass-midrange crossover and,
if the links are left in place, may cause
damage to the amplifier by shorting its
output terminals."

I'm not an expert, but I think you understand it correctly. Could you please keep me posted on what happens. I am just curious what will be the solution for you. thanks

Good to hear you were able to tame the brightness a little. I found that using Acoustic Zen Satori Shotgun speaker cables and Acoustic Zen Matrix Reference Mk.II interconnects in my system took my N803s to another level completely. Very smooth sound, no brightness, no fatigue. Also, I added EchoBusters Corners behind the speakers and that helps a lot as well. Biwiring the B&Ws is the way to go. What you may also consider is another set of tubes for the Manley. I would suggest contacting Kevin at Upscale Audio. He would be able to give you an advise on what tubes to use to get all the detail without harshness. Anyway, good to see the follow up.

of course it is Larry. Welcome B&W bashers to this thread

Vertigo, by the way, I think you should put the tweeter grilles back on. These tweeters are designed to be used with the grilles on, otherwise, I think the dispersion of high frequencies may not be what B&W intended. Just my opinion. I think they also mention it in the manual. Besides, this may even improve the sound even further.

Vertigo, also consider auditionning Sonus Faber Cremona, Cremona Audior and Vienna Acoustics Strauss. I audiotioned these and thought they were pretty nice but a little too smooth sounding for me. I like a little more open sound, but if you experienced fatigue with the N805s, these may be the ticket for you, depending on how much you want to spend.
And I would also suggest that when you audiotion the speakers in the showroom, make them play that system as loud as you would listen to your system at home for at least 30 minutes. This way you could tell if the speakers make you sick.
You could find some usefull info on the speakers I mentioned here - http://www.sumikoaudio.net/

Best of luck to you.