Questions about Sub-port placement?

[95 Silver TA]

Wanted to know what are the benefits and draw backs of having the ports on a sub like the VTF-MK3 too close or too far away from the wall.

Does the having the ports (facing the wall) too close (like 1-2 inches) disrupt air flow and cause port noise or cause bass to get too boomy?

Does having it too far (like 10 or more inches) reduce bass impact?

And what spacing is considered ideal?

What considered too far and too close?

[mystik610]

Hsu recommends keeping the ports at least 4 inches away from the wall. In my experience, any closer than that and the sub will be prone to distortion.

Having the sub fire into the wall will give your sub additional boundary gain, so there are definitely perks to keeping it relatively close to a wall. This will yield you more SPL's without any additional effort from the sub. If you can keep the sub in a corner...even better!

[Bill Mitchell]

I'm sure you've seen the posts by Pete Hsu that advise at least 4" from port to wall. Similar advice is in the Audyssey setup guide for receivers so equipped; they advise 4" to 5".

With corner placement, when I tried moving my sub port from 4" to 11" from the wall, Audyssey had to set the trim about 1.0dB higher. When I tried moving the sub even farther from the corner, the trim in the AVR was set 2.0-2.5dB higher. As a comparison, when I reconfigured the sub from MaxOutput to MaxExtension, Audyssey set the trim about 2.0dB higher for the same average sound level.

Of course, you already expected this. The farther you move the sub from the corner, the less the corner focuses the sound on the rest of the room, and the more power is needed from the amp for the same sound level.