As far as I know it should be fine. Try the other way too, copper to tweeter. . . .

Great. I know how important getting just the right sound from speaker wire is. I've settled nicely into the sound I'm getting from the Mapleshade thin, hardly insulated cyro'd copper set I'm using. I've preferred it to other copper and to silver-coated copper cables I've tried. I haven't tried silver cabling for speakers yet. I find that copper works really well for interconnects, and so does silver, but my system doesn't seem to lead me to prefer silver-coated copper to either separately. With this speaker wire I've tried all copper, all silver, silver-plated copper and the one that stayed (and multiplied!) were the VooDoo Cable which use both copper and silver conductors, and cry's them. Finding the right cabling matters! I find that copper works really well for interconnects, and so does silver, but my system doesn't seem to lead me to prefer silver-coated copper to either separately.

On the Hoffman forum there's a long thread about bi-wiring and jumper cabling for speakers. It's amazing how wide a divide of opinion there is there, which is the polite way of saying I'm surprised there are so many who can't hear or don't "believe" in a difference between types of wire. I keep wondering "what would they hear from Decware gear?'

Hopefully if you are going to do longterm damage to the amp someone will chime in pretty damned quick. I think you may be shortening the life of your output tubes a bit at the worst. If the sound is what you want and you're using new production tubes. . . then I think you can kick back and enjoy.

My DIY speaker cables are in some way based on Synergistic Research's cables, with multi-metal, multi-wires. Starting the path, I had a nice used pair of SR Copper Elements I was using. Then trying NOS WE 16 gauge wire, I liked things about it a lot, but it was too small for good power/flow to my HR1s...a little lean in the mids (especially low)...not enough bass in the balance. So I started experimenting with more strands of it. Three 16s brought up the flow/dynamics and bass pretty well, but also amplified the mid/upper mid emphasis of the wire, making it too hard. And this in turn, compounded the issue I have of the slightly rolled off top of the WE (as I recall anyway). So I added a strand, then two, of silver plated copper/teflon to one WE, also 16 gauge, hoping to bring up the top with the silver, and the mids/bass with both silver and copper, hopefully contributing both of their sounds (experienced with other silver on copper wires). This got a bit too tight and brittle (a potential issue with silver plated copper depending on the cables), though the balance got pretty good...the bass and low mids filled in, and the top opened up. Two WEs and one copper/silver also sounded "off" to me.

Following SR, I ended up with one solid/pure silver wire in oversized teflon, one solid/pure copper wire in oversized teflon, one very small titanium plated copper wire in oversized teflon, and one WE wire...Twisted to sound, finished with silver plated pure copper bananas, and adding a few Mad Scientists noise suckers (also to sound), and these cables to me beat my SR Copper Elements by a fair bit.

This was a long time ago and I have never gotten any sense it could be wrong for the amp or speakers.

Mine were pretty fun for me, experimenting along and along with my favorite cable to date, SR Copper, as a reference...so no sacrifice.

I tried a number of variations with what was around, then thought about it. Liking the dreamy potential of what I was hearing if I could fix the problems, and thinking I could fine-tune with a greater variety of wires, I ordered some things. I got lucky with the right combination of gauges and wire types.... extended, revealing, neutral, fast and smooth...slightly warm...not hard. Then trying a lot of twist variations they got really good...more revealing, extended, balanced, faster/more dynamic, and still smooth. The bananas were another good choice, and the Mad Scientist, sort of advanced "ferrite" like things, with more day to day exploration, things got even better.

It took several weeks I suppose, but then I just got happy with them, very happy. I occasionally play around with a couple Madscientist things....take them off, use different sizes or combinations...put them on different parts of the cables... Right now there is a small cupcake on each negative out at the amp, and a sample he sent...I think "magic tube," something like that (glass tube with some special powder mix in it) on the negative end at the speakers.

All that said, sounds like you just aced it! Way to go.

copper foil has been the "end all" of speaker cable for me, for about 10 years now....
I have some solid silver foil too... it is slightly more resolute... but it's significantly higher cost .vs. copper foil is not commensurate with the difference in sound which is relatively small.

Dan that must be what is giving me an even better detailed and smoother presentation with a better soundstage and depth.
I listened to a few albums that I am intimately familiar with and I have never heard them sound better, and as detailed and reveling as my system already was I actually heard things I had never heard before hidden in the background very nice surprise, sometimes it is better to be lucky than good.
Yes 8 gauge