Has anybody tried using single solid core cables?

Arcamadeus,
I try to avoid all encompassing statements or proclamations as there are always exceptions.
I will say I presently use solid core silver IC and speaker cables(bare wire to the speaker and amplifier terminals)and they are beautifully natural sounding, a joy and an asset to have in my system.
Charles,

Yes, I now use solid core silver cables all around and my experience mirrors what Charles just said.

YMMV but I also prefer solid core.ClearDay works best for me.I actually did hook up some 12 gage Romex(house wire) as speaker cables out of curiosity one day.The result was a smooth sound and no dynamics.Just as well,that stuff is so hard to work with!

I have the Clear Day solid core silver speaker cables. I also have the Morrow SP-6 and Anti-Cables. The Clear Day is much much better than the Anti-Cables and better than the Morrows.

12-30-13: Charles1dad
I try to avoid all encompassing statements or proclamations as there are always exceptions.

+1. Well said, Charles. To me the main usefulness of an unequivocal all-encompassing statement such as the one quoted by the OP, that not only excludes the possibility of exceptions but also fails to take into account the possibility that component dependencies may be involved, is that it helps to (negatively) calibrate the credibility of the person making the statement.

Arcamadeus, I'm not sure from your post if you mean four 18 gauge wires total (one for + and one for - on each speaker), or four wires for each speaker (two for + and two for -), or possibly even four wires for + and another four for - on each speaker.

Given the low impedance of your speakers (nominally 4 ohms, but most likely lower than that at some frequencies), if the length of the run is typical, say 6 to 12 feet, I would recommend that you use at least two of the 18 gauge wires for each polarity (+ and -). Or else use heavier gauge wire.

Also, you may find that you obtain better upper treble extension if you twist the + and - conductors together, say 3 or 4 times per foot. That will lower inductance, which if the + and - solid core conductors are physically separated might be high enough in relation to the speaker impedance to have perceptible effects in the upper treble region. The longer the run, the greater the likelihood of that effect being audibly significant.

Regards,
-- Al