what do you put under your sub?

Jaff2290

You won't need spikes....I doubt the concrete will interact much with your sub except to reflect energy...carpet and under carpet will provide damping to reduce any chance of rattle .....so why mess with it.

If it sounds muddy you may have room mode issues.....nothing to do with what your sub sits on but partly related to where it sits and the room shape itself.

My floor is a concrete slab with carpet and padding. The factory-supplied spikes for my two subwoofers were too short. They did not couple with the concrete. I was able to twist the subs a little in each direction. The subs seemed to float on the carpet.

I replaced the factory spikes with longer ones from Madisound. Nice but inexpensive cones with the proper thread size. They touch the concrete and the subs are now rock solid when I push them. Bass tightened up noticeably. Drums are more solid and defined and the bass (upright) line is better defined. Not only could my friends and I hear it but it was visible in measurements using my TacT equipment.

Later I decided to work on what was on top of my subs, frequently a forgotten area. My speakers are Apogee Mini Grands which are ribbon panels are mounted on top of dedicated subs. I put 30 pounds of sand on top of each sub and noticed improvements similar to what I observed with spikes although more subtle and not readily discernable in TacT measurements.

Before someone starts another "what kind of sand should I use thread" let me state I used AcoustiSand MKII. It is proprietary, scientifically-optimized grain size, double cryo'd, 6N silica sand. (6N=99.9999% cat crap free). It looks a lot like grit-blasting sand from Home Despot but don't be fooled. AcoustiSand really is worth the 100X mark up.

If anyone is curious they can try what I did. I had some ordinary (non-audiophile grade) sand around. I put it in double plastic trash bags just as an experiment. When I liked the results I upscaled to very heavy clear plastic bags inside of custom made fabric bags (with Velcro closures) that matched my subs. Kitty litter or bags of pet food could be tried just as a quick experiment.

One thing I noticed about the sand I used. It was very dry but it still packed into a very firm mass after being on the subs for a while. All the shaking settled it down. I can press on it with a fair amount of pressure and it will not move. I am wondering if that is still giving me good dampening or whether something that would not pack (something round) would work better. Oops, I guess this is a "what kind of sand should I use thread".

But not to forget Jaf2290's original question. Yes, I definitely recommend spikes long enough to penetrate the carpet/pad and couple with the concrete slab.

In my previous post, I made the assumption that the sub cabinet does not resonate in the frequency range you are using it for....if you have a cabinet that resonates (side walls waffle) then you have serious problems...coupling to something massive, like the concrete floor may help to dampen this but cabinet resonance means you will have distortion, especially on transients....normally a sub will be solid and very heavily braced internally to prevent this happening (i.e. no need to couple it to something solid in order to stop it resonating)

shadorne, the cabinet does not resonate at all... im fairly certain the problems i have are placement/ room effects. simply need to keep trying new locations.

Rel Stentor MK2...I put 200/pr Symposium Rollerblock Jrs under it, best tweak I have ever done. I totally lost the "one note blues", the sub opened up, easier to integrate..I used four, one under each foot. I can't begin to tell you what a huge diffence they made, and for a change, a tweak that wasn't a trillion dollars.