Monitor frequency response question

[crowning]

Hello,
maybe some of you guys have messed around with the frequency meter
during a studio installation and can interpret the diagram below with
much more experience.

At the top there's the original signal from a CD (it's pink noise, don't ask
why the graph is descending), below is the signal recorded at my
listening position with a condenser microphone.

Generally I'm rather happy to get it that good (for a non-studio environment).

What I'm worried about is the up- and down region between 640 Hz and
10 kHz, are this room reflexions which can be controled with absorbing
materials at the walls?
And if so, which materials are best for this frequence range?

Thanks in advance for your time.
Tom

 

[Ethan Winer]

Tom,

> don't ask why the graph is descending <

This is because pink noise falls off at a rate of 3 dB per octave. This is intentional.

> Generally I'm rather happy to get it that good <

If only. I can't tell how many dB each division is, but I promise you the real response is far worse than what's shown there.

> are this room reflexions which can be controled with absorbing materials at the walls? And if so, which materials are best for this frequence range? <

Yes, the skewed response is caused by reflections, and is best solved with absorption. See my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

It's a fair amount to read, but it explains all of this in great detail.

--Ethan

 

[mshilarious]

Personally I find the response graph difficult to believe, since monitors that can reproduce 20Hz at 0dB are, to put it mildly, expensive.

 

[giraffe]

i set up a earthworks sro in my room one time, and played some pink noise out of t5he monitors (really just for the fun of it, was not a scientific test)

and you would not believe the LF energy (10-50 hz) i noticed i was getting when i had the mic's open but the pink noise off.........

you can barely hear it at night if everything's off in the studio and your not moving. (noticed after i saw it) i think it comes from a factory about a 1/4 mile from here.

that's life.

 

[crowning]

Tom,

> don't ask why the graph is descending <

This is because pink noise falls off at a rate of 3 dB per octave. This is intentional.

> Generally I'm rather happy to get it that good <

If only. I can't tell how many dB each division is, but I promise you the real response is far worse than what's shown there.

> are this room reflexions which can be controled with absorbing materials at the walls? And if so, which materials are best for this frequence range? <

Yes, the skewed response is caused by reflections, and is best solved with absorption. See my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

It's a fair amount to read, but it explains all of this in great detail.

--Ethan

Thanks a lot for the comment and the link, I'll read it!
Best wishes,
Tom

Edit: If pink noise falls of at 3 db per octave you can get an
idea how many db each devision is.

 

[crowning]

Personally I find the response graph difficult to believe, since monitors that can reproduce 20Hz at 0dB are, to put it mildly, expensive.

The level itself is relative because just just have to increase the recording
level to push it up.

My goal was to compare the linarity of the graph compared to the original
graph, not the absulote levels (which don't interest at all).

And for the bass response, the monitors have a subwoofer to help there
It needed some time to place and adjust the subwoofer to match the
monitors, but now I'm a happy camper.

Thanks for your comment.
Tom