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A long time ago when my lounge was somewhat, uhmm , modified to accommodate my sound system we had no curtains. This was mostly because we could not afford any. It soon became clear that the room was little spooky at night but more importantly it was too alive sounding. So we got curtains. These were actually mostly blinds and were lined with hefty acoustic lining. After a while it became apparent that this was not enough so over decade or so acoustic treatment devices snuck in and more and more. The room is not perfect but it is where I want it....at least for now. So are curtains still relevant ?
This is the room with curtains open, seen from the right speaker. As you can see, lots of glass, sound damping glass with 50db efficiency but still glass.
Untitled by jdza, on Flickr
Here it is with curtains closed.
Untitled by jdza, on Flickr
So what does all these curtains do?
Here is a graph of the system's frequency response at the listing position. This is an all analogue system with no eq ability. The calibrated omnidirectional measuring microphone set at the listening position and height ,set at a 45 degree angle to capture the room.
curtains by jdza, on Flickr
Here is a graph of ideal in room freq. response from Floyd Toole at Harman
Screenshot 2019-11-08 at 17.48.41 by jdza, on Flickr
If you look at my graph closely ,you'll see 4 curves. That is with all curtains open to all closed in 4 stages. Hardly any difference! So curtains do nothing?
This is a T 30 graph of those same frequency responses. T30 is the time a sound impulse take to drop by 30 db in seconds. The slower the more echo there is, thus the more alive or splashy the room. Too high and sounds will mesh and detail disappear. Too low and detail will improve but sounds will have less "air" and spaciousness. It is generally recommended that for medium sized stereo rooms the value should be from 0.2 to 0.5 seconds. For smaller and home theatre rooms a value of 0.2 seconds or lower is recommended. More important ,the octave to octave variation should me no more than 25%. Usually one only concentrate on values of around 250 to 4 kHz.
So bearing in mind the above ,here is the T30 with curtains open and closed:
Black all curtains open and green closed. Bear in mind this room has extensive other treatment Time in milliseconds on y and frequency on y.
rt 30 by jdza, on Flickr
So does curtains make difference? yes but... Not below the transient frequency of the room. It is generally held that it will only make a difference at higher frequencies and will skew the sound balance of room, causing the room to sound unbalanced. I was quite surprised at how low in frequency the effect of the curtains go
This is the room with curtains open, seen from the right speaker. As you can see, lots of glass, sound damping glass with 50db efficiency but still glass.
Untitled by jdza, on FlickrHere it is with curtains closed.
Untitled by jdza, on FlickrSo what does all these curtains do?
Here is a graph of the system's frequency response at the listing position. This is an all analogue system with no eq ability. The calibrated omnidirectional measuring microphone set at the listening position and height ,set at a 45 degree angle to capture the room.
curtains by jdza, on FlickrHere is a graph of ideal in room freq. response from Floyd Toole at Harman
Screenshot 2019-11-08 at 17.48.41 by jdza, on FlickrIf you look at my graph closely ,you'll see 4 curves. That is with all curtains open to all closed in 4 stages. Hardly any difference! So curtains do nothing?
This is a T 30 graph of those same frequency responses. T30 is the time a sound impulse take to drop by 30 db in seconds. The slower the more echo there is, thus the more alive or splashy the room. Too high and sounds will mesh and detail disappear. Too low and detail will improve but sounds will have less "air" and spaciousness. It is generally recommended that for medium sized stereo rooms the value should be from 0.2 to 0.5 seconds. For smaller and home theatre rooms a value of 0.2 seconds or lower is recommended. More important ,the octave to octave variation should me no more than 25%. Usually one only concentrate on values of around 250 to 4 kHz.
So bearing in mind the above ,here is the T30 with curtains open and closed:
Black all curtains open and green closed. Bear in mind this room has extensive other treatment Time in milliseconds on y and frequency on y.
rt 30 by jdza, on FlickrSo does curtains make difference? yes but... Not below the transient frequency of the room. It is generally held that it will only make a difference at higher frequencies and will skew the sound balance of room, causing the room to sound unbalanced. I was quite surprised at how low in frequency the effect of the curtains go
