Help finding listening position (38% rule applies here?)

[zak7]

Hi! Anybody know if the 38% rule also applies here or may change when the height ceiling of a room changes in aradical way as here(check the pic)? I need advice here to know where are the first reflexion points.

This is a 20 FT (lenght) x 10 FT (Width) room.
This is a side view, the red line is the ceiling.(as you see varies).

Thanks!!!!

[Bob Olhsson]

The effect of room shape varies a lot because some frequencies will be reflected while others won't depending on the construction of the room.

There's no substitute I've ever found for simply putting in a bunch of time experimenting with speaker position.

[Ethan Winer]

Originally Posted by zak7

Anybody know if the 38% rule also applies here or may change when the height ceiling of a room changes in aradical way as here(check the pic)? I need advice here to know where are the first reflexion points.

Zak, the 38 percent rule is a function of the room's length front to back, regardless of the height. However, in your case you have two "back wall" distances. I agree with Bob that the only way to know the best places for your speakers and mix position is to measure the LF response at a high resolution (1 Hz bandwidth). But 38 percent is probably a good starting point in that room.

--Ethan

[AMIEL]

Originally Posted by Ethan Winer

Zak, the 38 percent rule is a function of the room's length front to back, regardless of the height. However, in your case you have two "back wall" distances. I agree with Bob that the only way to know the best places for your speakers and mix position is to measure the LF response at a high resolution (1 Hz bandwidth). But 38 percent is probably a good starting point in that room.

--Ethan

Interesting Ethan! you said Zak 7 have 2 backwalls distances because the height changes so the height of each front and back wall are different?... and high resolution ....do you mean to split the freq response graphic in 1 hertz to analyze what is going on? ????wow..can u elaborate a simple procedure?

[NathanEldred]

Originally Posted by AMIEL

Interesting Nathan!

I'm NATHAN, he's ETHAN.

[AMIEL]

Originally Posted by NathanEldred

I'm NATHAN, he's ETHAN.

Well Ethan ,Nathan... similar and both jewish names like mine!

[eirikur]

Originally Posted by AMIEL

Interesting Ethan! you said Zak 7 have 2 backwalls distances because the height changes so the height of each front and back wall are different?... and high resolution ....do you mean to split the freq response graphic in 1 hertz to analyze what is going on? ????wow..can u elaborate a simple procedure?

I think he's talking about measuring the room's low frequency response using stepped sine tones at 1HZ interval... Such as using the test cd found on his Realtraps site:
RealTraps - Test Tone CD

[Ethan Winer]

Originally Posted by AMIEL

do you mean to split the freq response graphic in 1 hertz to analyze what is going on? ????wow..can u elaborate a simple procedure?

Besides the link eirikur posted to our test tone "CD" you can download, see this article which explains how I use the ETF software:

RealTraps - Optimizing Acoustic Treatment using ETF

There's also FuzzMeasure (Mac only) and Room EQ Wizard (Mac or Windows). Google can find all three of these very capable programs.

--Ethan