subs near window?

Nope....Ella can't sing that low.

Dave

I think if you are asking whether the sub will rattle the window glass then you might consider using Marigoaudio.com VTS Tuning Dots on the windows.
You will hear better sound throughout the full audio range, even before you add the subwoofer.
For the support foundation beneath your subwoofer there will be many suggestions which are found in archived Audiogon discussion threads.
One of the simplest - place Herbiesaudiolab.com "Big Fat Black Dots" between the bottom of the sub and the top of a granite tile or tiles resting directly on the carpet.
If the carpet pile is not flat enough to permit that idea then consider one of the many carpet-piercing cone type footers.
Personally prefer to flatten a rug rather than piercing it. Don't care much for tattoos either :>)

Two possible problems from putting the sub near the window:

1. Bass will escape through the window, never to return.

2. The sub could vibrate the window and turn it into a large resonator (giving you a peak at the resonant frequency).

The first problem can never be cured.

With the second problem, this can be solved by increasing the mass of the window (thus lowering the resonant frequency to something lower than what your sub can do). I have no idea about those MarigoAudio tuning dots, but I would be skeptical if they had enough mass to treat a window.

You could increase the mass of your window by leaning something really heavy against it. Pad the corner of this object with some cloth/carpet and you're done.

Best solution is not to put the sub next to the window at all.

I have had dual velodyne 18in subs damage the seal between window glass causing condensation.

Here's a thought. From what little I know about how deep bass sound waves propogate I think if you are going to damage your windows (and that is certainly possible) you are as likely to do it regardless of where you place the subs. Also, consider whether or not there is a bass node where you are placing the sub.

To prevent damage caused by 'window' rattling sound (which is not necessarily the province of deep bass alone) damp the window panes or just turn down the volume a bit.

FWIW I recently traced a 'buzz' like vibration in my room to a framed picture on the wall. This was not caused by excessive bass. Just placed a little damping materiel between the bottom of the frame and the wall and it went away.