I have 2 sealed, front firing 15" subs.
In redesigning some of my dedicated HT, I have realized that I would like to raise the subs up by 4" or so. I realized this while sitting on the couch which is my first row, listening to music. (one of the redesigns is a new screen, so without a screen right now, I have become reaquainted with my music collection.)
My primary movie viewing position is in the "second" row, which is a row of theater seats, and then there is a "third" row of theater seats on a riser. The first row couch gets little use during movies, but will now become my first choice for music listening.
So I realized that the couch in front of my "primary" seating position is blocking/absorbing some of the punch from the subs. Granted, I am 4' or so further away in the "primary" position, but I also feel that the sub punch is being absorbed by the couch in front.
So I have set out to raise my subs up by ~4" to get them a little more above the couch and into the line of sight of the back two rows.
My idea was to source a couple pieces of scrap concrete or granite slabs, pavers, flagstone etc. to put under the subs. But that would require a slab(s) of at least 18" x 20" x 4" thick. Pretty hard to find in my initial search.
Then I got to thinking I could just get 8 smaller blocks and place them under the 4 feet of each sub. That would be easier to source. I was then planning either way to put a larger, heavy piece of something on top of the sub to add more weight and firmly plant the cabinet on whatever I put underneath it.
Are there any drawbacks to going the 8 smaller blocks route? That would leave an airspace under the subs, but as they already sit on the four feet only, and they are front firing, sealed, I don't see any initial problems.
Or would it be better to remove the feet and try to find a larger slab to put under each sub? Placing them flush and flat on a larger slab?
All of this is going to be over carpet and pad over concrete floor.
Or are all choices mentioned equal?
I don't really feel like going through the time of building, gluing and screwing and filling with sand riser boxes.