Not an original suggestion, but I am using Anticables and am quite happy with them. They replaced a pair of $2k speaker cables from a highly regarded manufacturer. I haven't missed the old cables. YMMV, of course.
Not as cheap depending on your definition perhaps for $500 on the used market are the all copper braid trio, an entry level cable from Jena labs. These are just very high quality copper in a typical braid that happen to sound fantastic in my system.
Used Cardas would also be on my list for Merlin but not the Neutral whatevers you want the Golden whatevers but for $500 you should consider the Cross whatevers. The Cardas copper in those cables is excellent.
An off the wall pick ....that I have used on a couple of occassions... that simply sound good even though they are cheap are the Pheonix Gold Bulk cable! Get them in a fairly heavy guage. I use the ones, that are blue and white spiraled a somewhat big wire which my dealer custom terminated for me as I required (small spades one side Banannas on the other in a biwire) very low cost well under your $500 limit for an 8' pair. I got them from Agon dealer "Quest For Sound." You will loose Cache but of course not the sound of good thick copper which the Merlins seem to love.
At first don't be surprised that you are not blown away by them but leave them in your system for a good while. I did that and did a "shoot out" with some very fancy cables and these came out on top. Not just my ears of course. I did eventually let the upgrade bug hit and used Jena cables. However I still use these in a second type system.
I'm waiting for some speaker cable that has been a very hot topic lately on the Yahoo Tannoy site, known as the "surprise cable", everyone that has tried has raved about it. It's made in Russia! As far as I know it doesn't have a specific name. It's dirt cheap though, with shipping from Latvia or someplace like that, a three meter pair was $58. It comes with no terminations, and in fact they are not reccommended, and have a clear covering ala Monster Cable. I'll let you know how it sounds. It's supposed to be revolutionary.
I saw a thread somewhere that recommended Supra Classic 6.0. Bobby tried them too and agreed that they were excellent. MUCH cheaper than $500.
I just googled the thread and found it here on Audiogon.
I am very happy with the Supra 6.0 on my TSMs. I took the risk of ordering them without hearing them first, partly because of Bobby's and others' thoughts; and partly because of the low price. Even after reading the comments of others, I was very pleasantly surprised. I'd definitely suggest that you read the linked thread.
I would check out the Tg Audio cables on Agon now! Under your stated budget, broken in already. They throw a huge, layered, tall stage - more coherent than all others I had on my Merlin Mxe's (incl Golden Ref, Au24...haven't heard the Clear in house yet...)
No affiliation with seller other than happy Tg owner.
I am also using a 12' pair of Supra Classic 6 that I made up, with a braided sheath, Furutech rhodium bananas, and heat shrink where neccessary. They look good, and sound great with my VAC PA 35.35, and HPD 315 Tannoys. I kind of forgot about them, as the other cables have such a splash overseas, the Supra slipped my mind. They really are very, very, good.
I finally got my speaker wires (it's a long way from Lithuania to Washington State). I finally got around to putting them in a couple of nights ago, and, by God, they sound damned good! It cost me $58 including shipping, for a stereo pair of 10'. I even think they might be a bit better than my $1400 cables. What the heck, there's not much to lose. If you are interested, send me an email, and I'll get you the guy's contact info in Lithuania.
"It's supposed to be revolutionary"
If I'm not mistaken you must be mistaken, the revolution has passed ;^) I have heard plenty of bargain cables and some are quite a bargain but when you use the term revolutionary with a 58.00 cable it is either an oxymoron or it really is revolutionary, my guess is the latter. Listen to it for a while, what you may be hearing now is differences more than anything else. It's happened to me many times.
I think the TG Audio must be good although I've never heard them in my system they frequently come up in the discussion with these speakers. My recommendations all cost more than your budget. Personally I never found an inexpensive cable (read CHEAP) that really brought out what the Merlins with good amplification are capable of. Having said that you might look further into some of the recommendations above but do your homework, opinions are cheaper than really solid advice.
If it were me I would seek out Bobby P for his recommendations, he is your best resource.
Keep in mind that you have invested in a highly resolving musical loudspeaker and are about to have it updated with the master bam which I haven't heard but I'm sure is a significant refinement. What I see here, especially in your budget area, are cables that may be hit or miss. You really don't know without listening and if you can, ESPECIALLY being on a budget, listen before committing. If you don't, this could end up costing you a lot more than your original budget. I have owned these speakers for 10 years and am giving this advice through my experience.
Why do you think people are constantly changing cables and powercords? Either one of two reasons,1) they want to try something different because they can or 2) They are searching for something "better" typically because there is still something missing. Keep that in mind and choose carefully unless you're interested in joining the flavor of the month club. It can get there faster than you think, been there done that. Keep the money in your pocket until you feel comfortable with your decision.
General rule of thumb is stay with copper but there are a few silver cables that are proven to work with this speaker. TG Audio is one, from what I've read, the others are beyond your budget. I'm not sure if Bobby is currently recommending any silver cables with his speakers but I wouldn't think the TG Audio would in any way be objectionable. The following are a brief list of i.c. and cables I've tried. There are numerous inexpensive combinations I've tried with little success. Its easier to get it close the first time.
Harmonic Technology Truthlink and Pro Silway
Stereovox (currently using throughout my system)Infortunately they are expensive but they really brought it all together for me and I have absolutely no desire to look for something better which is a very good thing! They've been in the system over 6 years.
P.S. I forgot the Analysis Plus, I would steer clear especially the silver. I used the Oval 9 copper and ultimately they were just ok though great at the time, see what I mean?
I tried Supra Sword ICs with my Merlin TSM mmi monitors. Nothing to write home about -- until I put them in series with 2 other high end XLR ICs. They elevated the other 2 ICs beyond my expectations. I would never go back to using the Sword ICs alone. For me using them in series is the only way to go.