Can a single terminal speaker be bi-amped?

Just acquired a second Hitachi HMA 7500, legendary amp from 70s, revamped by Approved Audio, and want to use both amps with my Kef LS50s. I would double up the speaker cables. What damage could I cause?
You could destroy one or both amps. Don't do it.

The only practical option might be to bridge each amp but I wouldn't bother.
Yes, as Kr4 stated...bad idea to double them up. How about bridge them if possible, or even use them as mono channel of amp 1 for the left speaker, and one channel of amp 2 for the right? It may improve separation compared to running one amp in stereo. Give it a try and let us know....
The problem is that your speaker would create a pathway AKA circuit that the power from amp one would travel to another. I am embarrassed to say I have done this experiment. The only way you might be able to biAmp is to use a really carefully designed crossover outside the speaker that would override your speaker's one crossover (wich should be disconnected). It is a major undertaking some of the other suggestions make sense e.g. bridging etc.
How does doubling have the potential to destroy the amp(s)?
Sorry, Mechans, I wrote my question before I saw your response.
Doubling the load onto vintage amps isn't healthy as well.
The only good solution I see is to get biwired speaker.
Seconding Mechans' comment, when the two amplifiers are paralleled, to the extent that each of them is "trying" to put out a signal that is not absolutely identical to the signal that the other amp is "trying" to put out they will each be forced to drive that difference into a load impedance corresponding to the output impedance of the other amp. In the case of most solid state amps that output impedance will be very close to zero ohms.

It looks like the HMA-7500 can be bridged. However in this case I would not recommend doing that either, because the impedance of the LS50 gets as low as 4 ohms at some frequencies in the bass region, where a lot of energy is often required. In bridged mode the amp will "see" a load impedance equal to 1/2 of the speaker's impedance, meaning as little as 2 ohms at some frequencies. The HMA-7500 is not rated to drive less than 8 ohms in bridged mode.

-- Al
Give it a try and let us know how it works out. You could just run the speaker wire from one amp to the terminals of the other amp and turn them on at exactly the same time. Good science experiment :)
If you put all the blue smoke back inside it will work again.
The real reason this is not practical is that amps have a low output impedance and each will, effectively, short-circuit the other when connected.
OMG THAT Sounds Real Audio!
Thanks very much for very detailed answers, even comprehensible to a non-physicist like me. Guess I wont be bi-amping speakers that are not bi-wirable!

Would you please " like me on Facebook " I don't have many friends.......
Dividing a passive cross-over is not a difficult procedure for an appropriate technician and well worth the low-cost investment. Especially if you are capable with the mechanics of installing the required additional binding posts.
Csontos has it right. If the cross over is built on a circuit board, you would need some real experience to bi amp, but if not or you can easily distinguish, before the crossover, the input from the tweeter vs the input of the woofer, you could very easily bi amp these. Of course, you will void your warranty.
What does "OMG THAT sounds Real Audio" mean, Czarivey? I may understand the physics now, but I couldnt follow that sentence:)