I've read a pile of articles about handling the first reflections from your front speakers.

However, I have a theoretical question.

Using the mirror method (place acoustic panel on side walls, where you can see the speaker in a mirror) .... This sounds all fine and great, but I've seen no mention on how to place properly (without my grade 10 math set) if your speakers are turned (angled) slightly to face the center seating position.

Make since? If so, what is the easiest way to accomodate this as the first reflections are no longer where the mirror makes the speaker visible.

Now sure if I explained that well, but I'll see what replies come in.

Thanks !

The angle of the speakers don't matter so much as the sound wave has spread. It's still going to hit the wall at the same spot.

I always love a good debate, so I have to disagree with you.

Your saying if I turn a speaker say 10-20 degrees, that the sound field is exactly the same as if it was facing straight ahead? The first reflection points have to change, otherwise my speakers send out the same sound signals 360 degrees ... :)

It's late, maybe I'm missing something .... but :)

From a reflection standpoint, you can pretty much imagine that the speaker is a point source. Certainly the sound field is not identical, but the reflections hit the side walls at roughly the same spot. (Plus, you're not treating 5 square inches of reflection point, but more like 5 square feet, so a few inches isn't going to matter that much.)

my Panels are 2' x 4', so 8sq ft ... so guess chances are I'm ok then.

I must not be starting threads like this, when I'm exhausted :)

The point of using the mirror is to see the reflection of the source. Sometime this is unclear by saying the speaker/cabinet is the source. I treated it as the woofer/driver as the source and hence even if i toed them in slightly, i would look for the driver being right in the middle of my mirror. To make thing even easier, my mirror is precisely 2 feet wide. I marked on both end and placed the panel there.

There is not much sound that will come from the speaker cabinet itself, unless it is something such as rear ported. Place the panels so that you see the speakers in the mirror. Remember to look in the mirror on the right wall for the speaker on the left side of the room and visa versa. They will not always catch reflections from the opposite side speaker, but usually do.

The early reflection point for the left speaker on the left and right walls will be different. Also consider the early reflection point of the center channel ... so you'll end up with a moderately large area for early reflection treatment.

When you toe the speaker in, you will not change the early reflection area, what you will do is change the quality of those early reflections...basically, those reflections will be reflections of the speaker's response more and more off axis as the speaker is toed in away from the wall. That could change your treatment strategy from more diffusion and less absorption to more absorption and less diffusion.

The early reflection point for the left speaker on the left and right walls will be different. Also consider the early reflection point of the center channel ... so you'll end up with a moderately large area for early reflection treatment.

When you toe the speaker in, you will not change the early reflection area, what you will do is change the quality of those early reflections...basically, those reflections will be reflections of the speaker's response more and more off axis as the speaker is toed in away from the wall. That could change your treatment strategy from more diffusion and less absorption to more absorption and less diffusion.

I'm confused Dennis. Which products aid absorption (linacoustic, OC703?) and which aid diffusion?

Absorption is typically your fiberglass based wall mounted panel (there are others, but fiberglass based panels are for absorption).

There are hybrid products such as RPGs BAD panels or Quest AI's Perf Sorber, which provide both diffusion and absorption.

Pure diffusors are characterized by products such as RPGs Skyline and Flutter Free.

The use of a hybrid panel or a diffusor needs some input from an experienced professional.

Dennis (like always) gave some GREAT advise. Just to add we just did a newsletter on early reflection points. You can read it here
http://www.gikacoustics.com/news_020209.html

Glenn