I asked a similar question before, but answerers were apparently too absorbed with other details that they answered something irrelevant.
When building a riser for a down-firing subwoofer, is it necessary to cut a hole in the board slightly bigger than the speaker? My subwoofer rattles quite a bit when just using the little pegs that came pre-installed on it, so I'm trying to reduce the effects of reverberating sound waves on the enclosure.
Verified answer
A downward-firing subwoofer is designed to use the floor to propagate the sound. At the very least, it should be firing at a solid surface, so don't make a hole in the riser. By putting it on a riser, you will end up with less deep bass than intended. For best results, always follow the manufacturer's recommendations regarding placement.
I've owned subwoofers from Polk, Klipsch, JL Audio, and Velodyne, and have got to say i have been more than impressed with Velodyne. You failed to provide any expertise about your room measurement, however that you may most of the time figure that smaller rooms (200 sq feet. Or so) only need an eight-10" sub, however go along with a better subwoofer for better rooms. They come in 12, 15, and 18 inches and have pleasant constructed in amplifiers. $600 will have to be more than sufficient to get one- their influence 12" can be observed for less than $four hundred with shipping. Also, there's a line of subwoofers designed by means of legendary Bob Carver calle dSunfire that i have heard nothing but the great in audio circles. For roughly $600-$seven-hundred or much less that you can get a 12" variant used on EBay. You is not going to be dissatisfied by means of Velodyne, although.
I don't know about the riser part of your question, what you can do about the rattles would be to get this item called vibramat you can find it in a car audio store. It has a sticky resin to hold within the interior walls of a car or around duct work in a house. Purchase a small sample of this item and cut it in squares place beneath the pegs it will do two things, hold the sub still and take away the rattle while absorbing whatever transient noise that may interfere in the slightest bit from your audio. Amazon may have something like it. This may save you from drilling holes.
Best.