Subs on stands

Depends. Generally you want minimum contact with the floor, and also minimum rocking potential, so anything you can do to minimize the contact footprint, and extend the footprint or lower the center of gravity and increase mass is good.


Any speaker driver will suffer from reflections from the floor boundary too, so keeping a sub close to the floor and walls can help minimize this particular effect.

I’ve had good luck with IsoTunes in general.

Putting subs on stands is a very bad idea for several reasons. 
1. Subs are most efficient when they are right in the corner and next most efficient right up against a wall. You want the driver as close to the plane of the wall as you can get it. Down firing woofers are great for this reason.
2. Most subs are anything but heavy enough. If you put your hand on the enclosure and feel it vibrating you have a problem. That vibration is distortion. Putting the sub up on a stand will just make the whole mess vibrate more probably most at a certain resonance frequency depending on the stiffness of the stand. 

The best way to deal with subs is to mount three spikes on the bottom which will give it the firmest connection with the floor. I also tell people to get a piece of granite and silicone it to the top of the woofer. The added mass will decrease enclosure resonance. Your local granite supplier will have all kinds of cut offs for cheap and will even cut it to size for you.

One other thing. When you put subwoofers into corners you eliminate the strongest primary reflections. The first one will be off the ceiling and the second off the rear wall. The effect on the bass will depend entirely on room dimensions. No amount of bass trapping or hocus pocus will change that. The best you can do is use room control to smooth things out at the listening position or get a bull dozer. With the subs in corners you at least minimize the problem.

+1 mjostyn! ALL woofers work best at the intersection of room boundaries (for best low frequency extension). Roy Allison designed his speakers with this in mind. As did Peter Snell (the famous Type A). Putting dynamic speakers out into the room away from the walls results in weak and uneven bass!

I've been using SubDudes for years.  Really tightens up the bass on suspended floors.  I also use a bass manger that provides room correction.

Thank you all for your suggestions. I will get to work making the changes. 

I put my JL Audio subs on top of 4" X 18" x 18" maple blocks that have 2" Star Sound brass spikes under it. Under the Spikes I am using Herbies gliders.

ozzy

If ever something cried out for isolation it’s a sub. 🙀

I run a JL E sub 10" set on a Sunoko Vent shelf and it improves the sound in every way.  I'm a believer in slight elevation and stabilization.

The best thing you can do is to experiment. There are many schools of thought on sub placement. (as you can see by reading here) It just takes a bit of effort to try different set ups. You don’t have to spend money to try it. Find something to place them on temporarily and see. I made some cribbing blocks about 14" square out of stacked 2x4 lumber. Its easy to add layers to adjust the height. (Milk crates work good) The added mass helps also. Dennis Foley of "Acoustic Fields" (they design room treatments for recording studios and listening rooms) recommends about 18" off the floor for subs to help smooth out the response.

I had the same experience as steakster and my subs are located just in-board and slightly forward of the main speakers which are 55" from the front wall (to the front of the speakers). This position not only makes the subs integrate seamlessly with the speakers in time but gives much tighter cleaner more tuneful articulate low end. I have tried many different positions and this is the best setup I have found for "my" room and system. Some will surly disagree. That is just the nature of this hobby.
I have found that putting subs well behind the speakers such as in the corners makes them sound somewhat disconnected from the speakers. Low frequency’s are much slower than higher frequency’s and take longer to reach your ears. Putting subs well behind the mains makes this worse. I’m talking about time alignment.
Speakers are Vandersteen 3a signature’s and a stereo pair of Vandy 2wq subs. (Vandersteen’s are time and phase aligned speakers.)