First order reflexion...................

[Clive]

Question to all our "Tweaky Birds" out there on first order reflexion. How does it affect what we hear, how can it be curved or corrected. Someone told me I needed a mic and a mirror 8O I take it that's the easy part............... Is this true?




CLIVE




HEY!! Why buy movie tickets when you can own a Theater?

[David Meek]

The mirror is just what you need to identify where your first order reflections. You sit in your "command" chair and have someone slide the mirror across the wall until you can see the front baffle of your main speaker in it. Mark that point as it is the "point of first reflection". Do this for both speakers on one wall and then repeat for the opposite wall. This'll point out where to put your acoustic treatment panel(s).

As far as using the mic for levelling the sound, how to do that will have to come from one of our sonic poobahs.
;x(




David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

[ThomasW]

Early reflections function as an additional 'sources' of the energy from the speakers. The reflected energy will combine with the direct radiating sound. The result can be a blurring or smearing of the sonics, since the reflected info is out of phase = time delay due to bouncing off the reflecting surface.

Comb filtering can also occur. This is where the out of phase reflected energy, combines with the in phase direct radiated energy and produces a null or nulls. This results in a frequency response plot with holes (nulls) that looks like the teeth of a comb (hence the name)

Early reflection (mirror) tests should include the floor if not carpeted, the ceiling, and the side walls.




theAudioWorx
Klone-Audio

[David Meek]

Oh, good point about the ceiling and floor Thomas. Thinking horizontally and not vertically.

[Chris D]

Yes, the ceiling is usually the most forgotten about surface. Treatment panels can get interesting, and expensive. Some companies do make aesthetically pleasing panels that work, also, but you can do something as little as adding a bookshelf or a carpet covered board to make small improvements.




CHRIS
Luke: "Hey, I'm not such a bad pilot myself, you know"

[justin]

I found a good book on this subject. The master handbook of acoustics by F. Alton Everest. Alot of interesting reading in there.

jus




Jus

Taking it one day at a time. Life moves quick.

[Burke Strickland]

The laser pointer that you confiscated from unruly teenagers at the movie theater :>) works well instead of a mirror. Turn it on and hold it against the front baffle of the speaker pointing toward the nearest wall, and wherever the beam hits the wall is where those pesky first order reflections are bouncing from.

Burke

[Clive]

Should work well, Thanks Burk. Easier to use too!




CLIVE




HEY!! Why buy movie tickets when you can own a Theater?