"Don Pearce" wrote in message
...
On Tue, 6 Mar 2007 18:03:14 -0000, "Serge Auckland"
wrote:
"Don Pearce" wrote in message
...
On Tue, 6 Mar 2007 13:39:14 -0000, "Serge Auckland"
wrote:
I have done some measurements on my listening room and would welcome
some
comments an advice.
The low frequency response of the room as driven by my 'speakers is :-
http://audiopages.googlepages.com/Sp...enmic-full.jpg
If anyone would like to replicate the FFT, the original WAV file is:-
http://audiopages.googlepages.com/whitenoiseopenmic.wav
Microphone was the one fitted to the Radio Shack Sound Level Meter, used
with the output taken to my sound card and recorded in Cool Edit. SPL
was
70dBC.
From what I've seen, the room response looks pretty reasonable, so I'm
happy
there. Go on, disillusion me.......
OK - here goes. Play a constant 150Hz sine wave tone through your
system. Now walk back and forth along and across the room with your
level meter and check how much it goes up and down. As you approach a
dip, slow down and move the meter gently in all directions (including
up and down) until you find the lowest level. How far is that below
the loudest part?
That will establish the level of standing waves in your room. In a
decent room, that should be comfortably less than 10dB peak-to-dip.
d
--
Pearce Consulting
http://www.pearce.uk.com
Certainly isn't within 10dB! More like 22-23 dB peak to dip, but much
more
dip than peak. In the main listening area, the swing was smaller, around
16dB Peak to dip, and again, few peaks and that of only around 6dB, but
some
quite deep dips. I did the test at 160Hz, as that's what is on my
(home-made) frequency test CD 1/3rd octave ISO frequencies.
Why did you chose this particular frequency?
S.
I chose that frequency because I could identify a dip there on your
plot. The optimum frequency for the test would probably be nearer 130,
though. This result certainly ties in well with your T60 measurements
- are you this isn't a bathroom?
Anyway, the result of these standing waves (for that is what is
happening) is that you will simply not hear certain notes - it will be
as if they weren't even played. This has to be a bad thing. Your walls
certainly need some treatment to deaden them a bit - hanging rugs
might be a good start.
d
--
Pearce Consulting
http://www.pearce.uk.com
And yet, the frequency response at the listening seat isn't at all bad, no
especially deep nulls or peaks. I do understand what you mean about
deadening the room further though, it's difficult to see how this can be
done given the amount of window area there is. This is a 1970s house when
enormous windows were the thing. I have blinds and curtains, but they don't
do a lot except at HF. I will experiment with some spare rugs, hanging them
from the curtain rails, and see what benefit I derive.
More to follow......
S.