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.......

I have downloaded a demo version of ETF5 from Acoustisoft
http://www.etfacoustic.com/ This software has measurement tools for
reverberation time, and I've only just started using it, so don't pretend to
understand it properly. Anyway, I've measured an RT60 of something like 2
seconds in the room, although it seems to be very flat with frequency,
rather than the normally sloping response. With the demo version I can't
save a file, so can't post one, and I'm reluctant to buy the software unless
I actually find it works. I'll make some more measurements and see if I can
understand what's happening.

My question is:- does anybody here have experience of ETF5 software, and can
they show me what a typical RT60 plot (say, of their listening room) should
look like.

Thanks

S.

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

"Serge Auckland" wrote in message
...
... Anyway, I've measured an RT60 of something like 2 seconds in the
room, although it seems to be very flat with frequency, rather than the
normally sloping response. With the demo version I can't save a file, so
can't post one, and I'm reluctant to buy the software unless I actually
find it works. I'll make some more measurements and see if I can
understand what's happening.

Don't know the software, but ... you would only get that
sort of RT in a domestic sized room by having virtually all hard surfaces.
That might suit you, but it would be very unusual and most people would say
it sounded too echoey. I would expect around 0.35 s - 0.5 s depending on
whether you have soft carpet curtains etc, or hard floor, rugs and blinds.
That's in the mid frequency range. At high frequencies it will probably
droop a bit, and at low frequencies it will probably go up to an extent
depending on the room structure.

Anyway if you're using the room to listen to music for enjoyment, the main
question is, does it sound nice. Not like a broadcasting or recording
organisation where rooms should be reasonably standardised. It would be
impossible to judge the balance of the material in a room with a very long
RT for its size but if the sound turns you on, what's the problem?

--
Tony W
My e-mail address has no hyphen
- but please don't use it, reply to the group.

"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.

"Tony" wrote in message
. uk...
"Serge Auckland" wrote in message
...
... Anyway, I've measured an RT60 of something like 2 seconds in the
room, although it seems to be very flat with frequency, rather than the
normally sloping response. With the demo version I can't save a file, so
can't post one, and I'm reluctant to buy the software unless I actually
find it works. I'll make some more measurements and see if I can
understand what's happening.

Don't know the software, but ... you would only get that
sort of RT in a domestic sized room by having virtually all hard surfaces.
That might suit you, but it would be very unusual and most people would
say
it sounded too echoey. I would expect around 0.35 s - 0.5 s depending on
whether you have soft carpet curtains etc, or hard floor, rugs and blinds.
That's in the mid frequency range. At high frequencies it will probably
droop a bit, and at low frequencies it will probably go up to an extent
depending on the room structure.

Anyway if you're using the room to listen to music for enjoyment, the main
question is, does it sound nice. Not like a broadcasting or recording
organisation where rooms should be reasonably standardised. It would be
impossible to judge the balance of the material in a room with a very long
RT for its size but if the sound turns you on, what's the problem?

--
Tony W
My e-mail address has no hyphen
- but please don't use it, reply to the group.


Yes, the room is hard, having a wooden floor covered in the central
listening area with a 3m dia. long-haired sheepskin rug. Furniture is
leather, and "minimalist". The room has always been difficult as it is
highly asymetrical, but since covering the walls behind the 'speakers with
rockwool, and building a bass-trap for the one difficult corner, it has
sounded very decent indeed. It is also part of a large open-plan layout, so
the room visually isn't huge, but acoustically, is over 12 metres long by 6
wide but only 2.4 high. Neverthless, I enjoy listening in it, but wonder
how it could be better.

S.

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

"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.

On Tue, 6 Mar 2007 19:27:11 -0000, "Serge Auckland"
wrote:


"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.



You won't see nulls caused by standing waves in a noise test. You need
the protracted phase coherence of an actual musical note to set the
wave up - it takes a few cycles to get going.

If you are happy with the reverberant nature of the room, you can cut
the standing waves down by breaking up any big flat areas that face
each other; these are the prime cause of standing waves. If you can
stand stuff near the walls to break up the area, that would be good.

The windows are definitely a problem, and I guess you can't do much
with them, although I'm betting you notice a huge difference in the
room's acoustic ambience when you close the curtains.

d

--
Pearce Consulting
http://www.pearce.uk.com

In article , Don Pearce
wrote:


You won't see nulls caused by standing waves in a noise test. You need
the protracted phase coherence of an actual musical note to set the wave
up - it takes a few cycles to get going.

Not quite. You *will* see nulls in the frequency response with noise as a
test signal. But to do so requires the *measurement* averaging time to be
long eough - thus allowing the frequency resolution to be good enough. You
can impose the 'coherence' by measurement.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

On Wed, 07 Mar 2007 09:45:08 +0000 (GMT), Jim Lesurf
wrote:

In article , Don Pearce
wrote:


You won't see nulls caused by standing waves in a noise test. You need
the protracted phase coherence of an actual musical note to set the wave
up - it takes a few cycles to get going.

Not quite. You *will* see nulls in the frequency response with noise as a
test signal. But to do so requires the *measurement* averaging time to be
long eough - thus allowing the frequency resolution to be good enough. You
can impose the 'coherence' by measurement.


OK, this is true, and of course I did identify a frequency for him to
try exactly this way from his noise test. But that test was never
going to show the 23dB dip he was able to find with the sine tone
test.

As you say, coherence is where you impose it, but for this purpose the
easiest place to do that is in the generation of the signal.

d

--
Pearce Consulting
http://www.pearce.uk.com