Acoustic panels - how high?

Is there a rule of thumb on how high an acoustic panel should be hung? I have a number of 2'x4' panels I want to hang behind my speakers and at first and second reflection points. My walls are 8ft tall.
Do I center the panels vertically on the wall or, since the top of my monitor speaker is only 4' high, do I lower the panel and center it on say the center of the speaker cabinet ?
Follow the directions in this link
A lot of good info, but didn't find an answer to my high to hang the panels on the wall. Maybe it doesn't matter.
Here's what I googled:
Thank you but again I found no answer to my question. Exact heighth on the wall must not be critical to room treatment.
Rockyboy...I have mine (12"x48" & 24"x48") exactly centered on the wall. 24 inches above and below the panel. I have 8 foot ceilings also.

I built a very crude stand for them that could be raised or lowered 6 or so inches at a time. I started them at 24" from the ceiling and lowered them until I found the perfect spot. Actually, I got them too low and had to raise them up. I went up and down several times with them to get them right. It just so happened to be centered on the wall when all was said and done.

I do have panel speakers (Magnepan MG3.6 & Martin Logan CLSIIA).
stay at your listening position and have a friend move a mirror along the wall until the speaker sound emitting areas are centered in the mirror. This center point can then be used as the center point of the absorber panels.
Very interesting. Thanks.. I've adjusted mine a couple of times but can't hear any difference. Of course, i can't remember what I had for breakfast this morning let alone how my system sounded before I moved the panels.
Like almost all room acoustic treatments let your ears be your guide. Since it is almost completely unpredictable how a particular room will interact with X brand speakers unfortunately the only way to achieve optimum or even good results with panels is to experiment - one panel at a time. I.e., if you try to find the best locations with multiple panels at the same time, with the panels all on in place when you listen, it's like trying to solve three simultaneous equations in four unknowns. Tip: when listening to one panel, keep all the other panels in another room otherwise they'll interfere with your experiment, then introduce one panel into the room at a time and listen again.
Follow Elwood's recommendation.
Elwood +1.
"stay at your listening position and have a friend move a mirror along the wall until the speaker sound emitting areas are centered in the mirror. This center point can then be used as the center point of the absorber panels."

The problem with that technique (using a mirror) is that speakers do not have uniform dispersion patterns thus making it difficult to visually obtain optimum results (using a mirror). This is especially true if you are listening to all panels at once initially when trying to make judgements. Not to mention all speakers actually have different dispersion patterns, making generalizations about location of panels kind of irrelevant. If you could obtain the dispersion pattern for your particular speakers you can do the geometry calculations and figure out exactly where the panels should go a priori.
oh, and another thing. not all panels are effective to the same degree and some panels do more harm than good. I wont mention any names but one of those that are ineffective is SONEX. it all kind of depends on what happens to the wave as it passes through the panel material twice.
It is possible since there was no difference in sound that the room is fine without them.
Another + for Elwood though. I used to have a few roomtunes etc..until I rebuilt the room with Crown moulding and added art to the walls.
Regardless of a speaker system's dispersion pattern, sound waves travel in a straight line and their angle of reflection will equal their angle of incidence. Thus, an easy way to find the first reflection point, of the waves that will actually reach your ears, is via the method mentioned by Elwood. ( Yes- a panel that will disperse or absorb those reflections must be chosen.
Further info, here: ( & (
Thanks, good info. I have treated first and second reflection points on side walls and improved things quite a bit. Think I will now experiment with a panel on my ceiling. No mention anywhere about treating the front wall either directly between or behind the speakers. Any thoughts?
It all depends on the geometry and the physics. In reality the second reflection points can be worse than the first ones. It all depends on the radiation pattern of the speakers, the dispersion pattern. That's why attention to the placement must be done by ear not some generalized instructions. Otherwise you're only finding the local maximum. Same goes for Tube Traps, you will not find the optimum locations by following the instructions of just plopping them down in the room corners since it depends on where the standing waves are actually located which might easily be two feet from the corner! Hel-looo!
OK, so I've just finished playing - yet again...

A friends place has a 12ft ceiling, so I've been looking at possible solutions.

So I got to thinking about my room with an 8ft ceiling and how a "baffle curtain" might help.

I just happened to have a piece of heavy duty vinyl 2 ft x 6ft and a couple of lighting stands, so I rigged it such that the vinyl hung down from the ceiling like a banner, across the room and tried it in a couple of positions...

1. just behind the speakers...
- There was some improvements in clarity and image
- nothing really to write home about

2. just behind the listening position...
- talk about an OMG moment!
- clarity improved beyond my expectations
- image now easily exceeds the boundaries of the room on most all tracks
- projection of venue acoustics forward now easily envelopes the listener on many tracks
- it's like surround sound with only two speakers
- the improvements can easily be heard outside of the room also, just amazing.

BTW - I also have a couple of 15" x 78"(tall) panels on the side walls behind the speakers to deal with an echo that travelled across that wall behind the speakers

I treated the top five feet of the wall behind my listening position with 2" Auralex Studiofoam Wedges, with LENRDs in the corners and accomplished the same effect. An added benefit is being able to listen at realist levels, without overloading the room. Happy listening!
Take Elwoods advice re the mirror and if you wish to maximize your efforts on first, and second,reflection,go floor to cieling with panels in those locations. You cannot go wrong with this simple solution,and it will benefit you. Good luck and let us know your results :) Pete
Eleven little Zilplexes will greatly exceed any benefits of acoustic panels.
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Hi Rocky,

One thing I have found is that acoustic panels improve imaging in the dimension you lay them out.  That is, if you don't find very deep imaging, put more behind the speakers. If you find the image is in a line between your speakers, put more dampening above and below the speakers, that is on the floor and ceiling. 

Of course, getting rid of primary reflections is the first thing you do, I just thought this might help. 
Thanks for your input. System has now evolved to final incarnation. I've addressed the room acoustics to the point that I can finally sit back and enjoy the music.