Monitor close to the wall to replace Allison 4s

"I am vertically bi-amping, one amp per speaker, so I could just double up the cables on each speaker. Any reason not to?"

Yes, IMO, there are reasons not to.

What you are referring to amounts to paralleling (aka monostrapping) the outputs of the two channels of each amplifier (i.e., connecting them directly together, through the speaker cables), with the same signal going into those two channels. As Yogiboy indicates, that is completely different than passive biamping, which is what you are presently doing with the Allisons (and which is what ElDartford refers to as dual-amping, to distinguish it from active biamping).

Passive vertical biamping, as you are doing now, results in one amplifier channel supplying current and power essentially just at mid and high frequencies, and the other amplifier channel supplying current and power essentially just at low frequencies. Paralleling channels is completely different, and results in both channels supplying current and power at all of the frequencies that are contained in the music.

Paralleling amplifier channels CAN be done with many tube amps (don't ever try it with a solid state amp!!!), and it can provide a considerable increase in power capability. But if things go wrong there are ways in which it can have very destructive results. And it is likely to produce very different sonic results than either passive or active biamping. And for good sonic results it would most likely necessitate changing which output taps on the amplifier are being used, and in some cases it may turn out that none of the available taps are optimal.

See the post by Atmasphere dated 2-11-13 here, and the discussion by Atmasphere and me in this thread.

I'll close by mentioning one conceivable scenario that to ME is sufficient reason in itself to avoid ever paralleling two amplifier channels: A small signal tube serving one channel of the amp fails, at some point in the future. You start playing music. One channel is trying to put many volts and watts into the speaker, while the other channel (with the dead tube) is trying to force the speaker's input to zero volts. The outputs of the two channels are, of course, connected directly together through the speaker cables in that situation. Ouch!

Regards,
-- Al

Almarg, I am very grateful for your input because I DO seem to be paralleling currently, as I am biwiring - that is mixing the signal to both sets of speaker posts - and I should be separating the hi pass and low pass inputs on the speakers to avoid a disaster,it seems! I can do that as I have 4 runs of single cable. Do I understand you correctly? Thanks!!!

Denis, if there are any connections between the high frequency and low frequency binding posts on the back of the speaker they should be removed. Speakers having separate pairs of binding posts for the high and low frequency sections of the speaker often come with a metal "jumper" that connects the two red terminals together, and another metal jumper connecting the two black terminals together. For biamping, those jumpers (or any wires that may be making similar connections) should be removed. If they are left in place, yes, you are paralleling.

You are not biwiring, though, which involves the same kinds of connections as biamping at the speaker end (with the jumpers removed), but drives both sets of cables and both sections of the speaker from a single amplifier channel, rather than from separate amplifier channels.

Regards,
-- Al

Al, I am both paralleling and biwiring, since each amplifier channel is driving both hi and low pass terminals- exactly as though they still had jumpers in place! But I will change that and not have any connection between the high pass and low pass terminals any longer.

Ok, I see what you are saying, Denis. I hadn't understood the reference to 4 runs of single cable. So you are biwiring to each speaker from the outputs of each of the two channels of the amplifier that is dedicated to that speaker. As you say, that amounts to both paralleling and biwiring.

A number of people have reported here that paralleling speaker cables (as opposed to amplifier channels) has resulted in some improvement in sonics, in their systems. So connecting two of the runs between the low frequency speaker terminals and one channel of the amplifier, and connecting the other two runs between the high frequency speaker terminals and the other channel of the amplifier, would seem to be worth trying, and might produce results that are at least slightly better than biamping with just two runs in total.

Regards,
-- Al