Can rear reflection from ports affect stereo imaging?

[GeorgeH]

I have a 5.1 system consisting of four Onix Reference 1 speakers, and a Ref100 center channel. I use the system for 2 channel music as well, and stereo listening is one of my main goals with the system.

My normal speaker setup has the front mains sitting on a flat surface (top of a Salamander console), with the back of the speaker 10 inches from the back of the wall. The Ref1s are rear-ported, and I run them small to avoid the bass exaggeration that happens with rear ported speakers being placed so close to the wall.

So far so good. No booming bass, and the 2-channel imaging is good, but I recently found that if I take the speakers off the top of the console and put them on stands just in front of the console, which puts the rear of the speakers about 26 inches from the rear wall, the imaging improves considerably.

Why does this occur? Is it due to reflection off the back wall from the ports reaching my ears too soon when the speakers are set on top of the console, closer to the wall? If so, can this successfully be treated with small acoustic panels behind the speakers? I want the enhanced imaging, but I can’t leave the speakers on stands in front of the console on an ongoing basis, and I like to avoid pulling the stands out anytime I want a “serious” listening session.

The room is untreated acoustically.

Thanks for any feedback,
George

 

[Seth=L]

May have something to do with the distance angle relation to the seat. The port should have no bearing on the imaging, as it radiates lower frequencies that aren't necessarily part of imaging as much as they are just different in bass.

 

[bpape]

It also likely has to do with losing the boundary below the speaker (the cabinet) which is acting just like a wall would.

Bryan

 

[GeorgeH]

Thanks guys. I was wondering about those issues as well. I'll experiment with positioning more.

 

[annunaki]

I am guessing that it has to do with the placement of the speakers on the rack and reflections from the hard surfaces there. Is your television placed between the speakers as well?

Try bringing the speakers right out to the very edge of the rack or potentially overhanging the edge of the rack.

 

[GeorgeH]

I have the speakers all the way out to the edge, with the plasma recessed back a few inches. I will try to pull them out a few inches to see if that reproduces the imaging affect. I still can't leave them that way on a regular basis, but it's easier than pulling stands out.