Speaker cables under floorboards - a good or bad idea?

Hi all…. Relatively inexperienced about the dos an don’ts of how to run speaker cables from the amp to the speakers for optimum performance. Am using Supra Classic 4 cables - 5 metre runs - from a Lyngdorf TDAI 2200 to a pair of Quad ESL 57s. The Supra cables are currently sitting on the floorboards for their runs from the amp to the ESLs. Am content with the way it all sounds, if not with the way it looks! The floor itself is suspended timber with a joist depth of 6 inches under the floorboards. And over the coming weeks, I will be lifting the boards to fit rockwool sound insulation in the underfloor cavities (to reduce the sound levels reaching the room beneath mine). ….So, I thought I would take the opportunity, while the boards are up, to run the Supra speaker cables under the boards. To be effective, the rockwool needs to be dense, and fill the underfloor cavities as tightly as possible. This means that, if I run the Supra cables under the floor boards, for most of their runs, they will be in intimate contact with dense rockwool. … Given that a lot of folk have found that the best way to run speaker cable is on cable elevators - i.e. as little contact with anything as possible - is the plan wise? I could try it and see/hear for myself of course, but obviously want to avoid taking the boards up - again - if the SQ is compromised.  Any thoughts - or experience - would be most welcome.
The rockwool needs to be packed tight?

I think it need to be packed everywhere, NOT TIGHT. The tighter the pack the less effective it is. Be careful with that too.. Don’t breath it, or expose it to open air...It has to be sealed...Protect yourself and OTHERS when working with it...Kids, Dogs Cats, Rabbits....

Second the size of the stran, is what is important. The wave is what you’re trying to control. Bass? or ALL sound? Large stan = better bass control, a mixture of stan size makes a BIG difference, overall, sound control.

Third, it’s speaker cable, and you want to lose the cable? WHY? It’s not a surround, thing, it’s not ugly, why do it? You said why NOT, to do it, so why do it? You answered your own questions. You raise the cables so YOU can clean under them, RIGHT? You hear a difference?..   A lot of bass, and anything on a platter or caddy, is gonna be an issue..  If the cable is in the wall and the BASS in the room, what about from the speaker to the wall or amp to wall, still exposed to vibration. Just sayin'. If anything was going in the wall, I would plan on it staying there, if I didn't like it for some reason... 39 1/4 x 5? 3 dollars a foot for the REALLY good stuff.
How much did that speaker cable cost to begin with, I'm frugal... BIG TIME..

If you do it I suggest installing a conduit for the speaker cables in order that it can be easily removed/replaced (if needed) later on.

You would want something with attachable right angle elbows to come up through and flush with the flooring.

I would also run the left/right cables separately @ least 6" apart.

1" conduit should work, or maybe 1.5" just to be future safe.

Also, avoid routing it close to any AC wiring.


Very useful, helpful advice - many thanks DeKay.
Conduit sounds like a good idea. Save some of the wood then if you ever sell the place you can plug your holes, new buyer will never know. 
Didn't think of that, conduit is a good idea. Yup..

Horrible idea. Worst for sound quality, won't hardly reduce noise transmission. Speakers on springs, cables on elevators. Done.
I would get a preamp + amp combo that supported long runs of XLR cables. You could stuff those cables under the floor board easier (with respect to sound quality) than the speaker cable. I know the professional grade Benchmark StarQuad XLR that I use can work in your scenario well for very long runs. I think my cables are 15 feet or 25 feet runs, it sounds excellent. Some smart guys on A’gon told me to makes sure my preamp-amp combo supports the AES48 XLR standard for long runs. I contacted the manufactures of gear I was interested in to ask about AES48 before I bought. For ex. Benchmark and W4S supported it and Luxman did not.


I know the Lyndorf 3400 can support XLR not sure about your 2200. You can also use the 3400 as a preamp only and output to different amps via XLR, I have done this in a demo of the 3400.

BTW - i though the preamp + DAC of the 3400 was really good. The amp section was not something I liked. When I went to an external amp via XLR the system sounded great. That was a $15K external amp but I think a Purifi amp from March Audio for under $2K would likely yield the same results.
It will make cable lifters pretty challenging
Seriously, horrible idea. To give some idea, I tried wrapping my cables with very thin gauge wire to see it it would control vibration. As mahgister pointed out, hold them while playing music its shocking how much they vibrate. Just this thin wire wrapped around them devastated dynamics and detail, sucking unbelievable life out of the music. Packing cables tight in rock wool, when you hear how bad it is, don't try and say nobody tried to warn you. Springs under speakers will improve sound and reduce transmission. Cable elevators will improve sound, even more if used with my rubber band tweak. https://systems.audiogon.com/systems/8367#&gid=1&pid=10
I disagree with millercabon.
I think running the cables underneath the floor in a conduit would be a good way to go. If anything you could change, I would opt for some Audioquest cables with DBS-Like the GO-4-Good but not cost prohibitive.
If suspending cables is the cool thing to do now then you can run them completely through the floor and they can be suspended from the ceiling of the room below.