PassRad
Panels Done, Time to Determine Best Placement and Hang Them Up
Twelve Finished Panels Ready for Hanging  
Placement and Hanging
As mentioned earlier, many domestic rooms are acoustically "OK" but that doesn't mean some treatment won't improve them. For absorption panel placement the first thing you want to find are the primary reflections from the left and right front speakers (and the center channel, if it's a home theater). These direct initial reflections from the speaker drivers have the most significant impact on what you hear.

Here's an easy way to find them:
  • Using a flat mirror (the bigger the better) have a helper slowly walk the room holding the mirror flat against the wall, at seated head height.
  • Sit in the prime listening position ("the sweet spot") with your head positioned as it would be when you're listening. Watch the mirror and whenever you see one of the front two or three speakers reflected, that exact spot on the wall should be marked in some way.
  • Turn your head to look at the mirror but don't lean in any direction, just try to keep your head in the most natural listening position. Those marked spots, at seated ear height, are the prime reflection points and the ones you want to first treat.
Quick Placement Tips
  • We're mostly concerned with side wall reflections but ceiling and floor reflections can impact sound quality as well. 
  • Hopefully the floor is covered with thick carpet and padding. If not, a thick area rug with padding placed in front of the speakers will help. 
  • Those first reflections from the two or three front speakers are the most critical. 
  • If possible, move interfering objects in order to keep the mirror flat up against the wall. 
  • An upholstered piece of furniture can be used instead of panels but note that leather furniture is not acoustically absorptive, it's reflective. 
  • It's most important to treat the walls at seated ear level. You don't have to treat large areas beyond that.
  • You can evaluate other listening positions beyond the sweet spot as well (but, you may need to keep a balance between placing acoustic treatments around the room and living with your significant others).
Our Installation - Step By Step ...
We followed our own instructions and located the prime wall reflections of the three front speakers in our system (a pair of Triton 2+'s and a SuperCenter XL). Once located:
  1. Mark each reflection, centering the panel on seated ear height so it is both above and below that point.
  2. Hold a 2'x2' panel and make short, light positioning pencil marks on all four sides, on the wall.
  3. Mount four of our spiked mounting plates (see photo to right) for each panel, using hardware appropriate for your wall type, near each corner as "guestimated" by eyeing the positioning marks made. Since the panels are simply pushed onto the spikes, the mounting plates don't have to be precisely placed as long as they're inside the frame of the panels.
  4. We suggest using four plates to compensate for the weight of the wood and cloth on each panel.
  5. Carefully level the panels and press them onto the mounts. Ours seem to remain firmly mounted and have not budged after 3 weeks. And, we can just pull them off if we want to replace the cloth or paint the room and then put them back up.
  6. By using two panels on each side of the room we managed to cover all three front speaker prime reflections because the three speakers aren't that far apart. Your mileage may vary.
Our Impressions -  Here's What We Heard

This room has some inherent low frequency acoustic flaws that our two inch thick panels will have limited impact on at these bass frequencies. However, the panels will have significant impact on frequencies above the bass range.
The most significant change we heard was in imaging and soundstage presentation. Imaging was dramatically more precise, with rock-solid, easily defined image locations now as compared to without the panels. The s oundstage also grew significantly in width and even a little bit in perception of depth, significantly better and more stable. We didn't hear any noticeable change in tonality or overall sonic presentation.  Because of the way we mounted them they can be taken down and replaced pretty quickly for comparison purposes to confirm these impressions.

We are also going to mount a couple of panels on the back wall, behind the listening position to see what impact they may have. We may want to use diffusers back there as opposed to absorbers as per generally accepted recommendations.

Notes  
 
The Noise Reduction Coefficient (commonly abbreviated NRC) is a scalar representation of the amount of  sound energy absorbed upon striking a particular surface. An NRC of 0 indicates perfect  reflection; an NRC of 1 indicates perfect  absorptionDue to the formulas used, the  coefficient  is not a  percentage  and values larger than one are possible (and common).

Links
 


Room Acoustics Recommendations (targeted for a studio but still worthwhile)



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