In my HT I'm going to have my mains hidden behind an acoustically transparent curtain. For front ceiling absorption I don't have the option of mounting panels due to recessed lighting cans in the way. I was thinking of hanging panels vertically from the ceiling just behind the curtain. How far in front of the face of the speakers should it be. How close to the top of them? How large a panel? I guess I could just use the mirror method? Any downsides to doing it this way?

Hope I explained my idea well enough...

Yes use the mirror method to hit the reflection point.

Glenn

Assuming your tweeters are at ear height, which they should be, the ceiling reflection points are halfway between your ears and the front of the speaker cabinet. As shown here:

How to set up a room

Of course, it's not a single point, but an area. If you have can lights there, cover that area as best you can leaving holes for the lights. A few small holes will be okay.

--Ethan

Here is a trick I am trying using craft paper. I cut it to the size of the panel and laid it out on the floor to see how the coverage looked. Ignore the hairy knees.



You can possibly use coffee cans on the floor to show where your can lights are. This way you know what areas to avoid. I have a large off center ceiling fan I am trying to work around.

Thanks for the replies so far. Not sure if I described my idea well enough though. The pic shows what I'm talking about. The absorber could be hung at whatever height was necessary. It could also be slightly wider than the speaker or span the entire width of the room. The latter option would also provide a ton of extra dampening though not as efficient as placing it directly on the wall, I assume. Theoretically it would have the same affect on errant sound waves as a brim of a ball cap has on the sun. I'd really like to avoid a ceiling panel due to the recessed cans.

Do you mean you intend to hang penal straight down from the ceiling? I've never tried that, but I think they'd have to hang down awfully low to stop reflections from the ceiling.

--Ethan

Yes, Ethan. I'm far from an expert but to me it seems if the panel was in front of the speakers say about 2' or so it may do the trick. Of course it wouldn't really do much for the bass though. The Cornwalls and Hereseys have horns for mids and highs. Judging by the top and bottom angles on the horns they appear to be fairly directional. Also, the mids and tweets are stacked right on top of each other. As long as the absorption panel hangs just above the horns from the listening position I don't think there would be an adverse affect on the sound, specifically the imaging. Again, I'm not an expert but the idea seems effective enough to not require a panel at the first reflection point on the ceiling.

Again, I've never tried that. But I'll be interested to see some data if you'd like to try it for me.

Programs like ETF and REW can show the strength of individual reflections, so it's possible to test this and see if you can place the panels "just so" to block the reflections.

--Ethan

Ethan, I'd be willing to check it out for you as soon as the room is completed. I assume I'd need a laptop, the software and a microphone, correct? Is the mic an expensive unit? Obviously we're not talking a Wal Mart karaoke special.

When the room is complete including all the acouctic panels except the ones we're talking about here, I'll contact you regarding the procedures to test it out.

Software and mics:

ETF, Windows, $150
FuzzMeasure, Mac, $150
Room EQ Wizard, Windows and Linux, Freeware
This article explains how I use ETF, but the principles apply to all such programs.
Comparison of Ten Measuring Microphones

I will see if Bryan has any data on this. I know this is something we have done in larger rooms.