Proper method when rack is not on cement floor

Rushton, that link takes me to a sort of general page on HD. I see no jack posts there. I did a search and found a Tiger Brand selection in HD. Are these the ones you were referring to?

No problem. Is the idea to "push up" a bit on the jack once it has been put into place? That is, to put some counterpressure on what is probably a sagging floor? If so, how is that done with these jacks?

Okay. Just have to find someone willing to get into that crawlspace! I'm too big a guy to squeeze into something like that. I took another look at it, and it's more along the lines of two feet or so.

That's a great suggestion, Sean. Thanks. I can easily get a 4x4 cut to the right size at my local lumberyard. But, I have some questions...

The room where the equipment will be placed is 11' deep x 17' wide. The floor joists run from front to back, parallel to the 11' depth. So should I use just one 4x4 stringer that's about 16' long, set about halfway back into the room? The room is actually the back extension of my media / family room; the front part is about 12 x 17, and is over a full basement. That's where the media display and the front speakers are located. Yes, I understand that's counterintuitive. I should brace the flooring under the crawlspace and put the speakers and display over there. Tried it, didn't like it. It also did not meet the WAF. So I have to do what I'm doing. Given that my speakers are actually in a different part of this combined space, how much improvement will be secured if I do the bracing, but really have only the equipment in this area?

Zargon, much thanks for the detailed information. I should be able to do all that you mentioned (as needed). It's just a question now of getting it all in place.