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Influence of curtains on room acoustics

abdo123

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So in our living room we have a humble 2.2 setup with generally subpar acoustics. We installed relatively thick curtains (the thickest the shop can make them, usually for performance spaces where you want zero light entering) and this thread is basically some rough measurements showing before and after. The curtains cover around 80% of the surface area of an entire wall, this is why the decay times were dramatically influenced, even at frequencies lower than expected. Speakers are flat on-axis with smooth directivity.

The room changes all the time so don't pay too much attention the region below 300Hz. I tried to control the microphone location as best as I can.

Here is a picture showing how thick the fabric in the curtains is

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and measurements

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Listening impressions were very very positive, however, there are some caveats. Bass ringing is much more obvious now since the mid-range and treble experience that less. I'm probably going to install some bass traps in one of the corners next. Everything with regards to anything in the vocal region from 800Hz and up is incredibly clearer and more intelligible. Overall it's defintely a very positive improvement.
 

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Bugal1998

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Thanks for sharing the measurements and listening perceptions. Which wall is nearly covered?

Did you notice any increase or decrease in the sense of spaciousness and/or envelopment delivered by the system?
 

Vacceo

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This is the clear demonstration that there is a viable method to get better sound even if your room has large windows.
 
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abdo123

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Thanks for sharing the measurements and listening perceptions. Which wall is nearly covered?

Did you notice any increase or decrease in the sense of spaciousness and/or envelopment delivered by the system?

One of the side walls is covered.

The spaciousness factor is definitely diminished, the space is too small for me to focus on early reflections and leave the late ones alone. So that's a compromise i just have to accept.
 

thorvat

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The spectrogram says its a good thing — peak energy timing is better. Not too difficult to EQ it down a bit if bothersome.

As an alternative to EQ-ing the 100-300 region I would suggest shelving down the entire 300-20K region by app 4dB which would result in the graph shown below.

I would expect both graphs to have much better LF-MF-HF balance in this case.

P.S. Goes without saying that adding a sub should considerably improve low end assuming the integration is done correctly.

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Bugal1998

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One of the side walls is covered.

The spaciousness factor is definitely diminished, the space is too small for me to focus on early reflections and leave the late ones alone. So that's a compromise i just have to accept.
As you said, it's about finding the right compromises to maximize the space... Especially if the same space needs to accomodate other uses. Yours is an interesting use case that's probably similar to the circumstances of many other readers, which makes the sharing of your experience and messurements all the more valuable.

I too found I preferred extra damping in smaller rooms due to the improved clarity and, at times, improved spaciousness due to more easily hearing the cues imbedded in the track... In my small room I had 4-6" absorbers covering a large percentage of most walls and the ceiling, and I wasn't sure if curtains on one wall were enough to give you a similar perception.

There's also an asymmetry in your room and I was curious what effect that may have.

I'm pleasantly surprised the curtains delivered a relatively consistent change in decay times over such a broad spectrum.
 
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Ciobi69

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This is the clear demonstration that there is a viable method to get better sound even if your room has large windows.
Windows are thinner than standard walls, so the bass frequency get thought the windows, and vibrate (dissipate energy) an acoustic told me this,Soo it's a myth that windows are super bad,with a curtain they are surely better than a wall
 

Vacceo

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Windows are thinner than standard walls, so the bass frequency get thought the windows, and vibrate (dissipate energy) an acoustic told me this,Soo it's a myth that windows are super bad,with a curtain they are surely better than a wall
The vibration you get on glass due to low frequencies is a terrible sound. Perhaps not due to glass itself, but windows have that tendency to be part of a metal or plastic frame that also gets nasty sound when it vibrates.
 

sq225917

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I have similar double lined 'theatre curtains' in my music room, the effects of drawing them to cover the 8 foot wide window is pretty much as you show. The soundstage is better centred with them drawn and maybe a hint of great stage width as a result.
 

Galz

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I have heavy windows as my right wall (left side is open to kitchen), so they don't vibrate at all (need pretty strong wind of a winter storm to make them make some sound). The 20Hz room mode (which is a width mode actually remains even when I open it (the sliding window is most of wall, and can be 75% open), I still get that 20Hz room mode, but overall bass levels are lower by a few db in comparison to closed window. So those windows are definitely having an effect on the bass, but probably aren't coloring it (as the overall response shape is not changed much when open, although I measured only the subwoofer).

Curtains are relatively heavy and are practically light proof (you need to place a strong light right against the fabric to get any light coming through, and most of the light coming in goes above and below the curtain rather than through it), yet probably not nearly as heavy as the ones shown here. Measuring only showed about 0.1s difference from 1KHz. Although I might not be looking at the graphs correctly...
 

ernestcarl

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As an alternative to EQ-ing the 100-300 region I would suggest shelving down the entire 300-20K region by app 4dB which would result in the graph shown below.

I would expect both graphs to have much better LF-MF-HF balance in this case.

P.S. Goes without saying that adding a sub should considerably improve low end assuming the integration is done correctly.

View attachment 225834

I thought @abdo123 already employed more than one sub so the graphs were really only of the mains on their own.

The shelving EQ could work well in improving the overall balance as shown in the predicted curves, perhaps… an A/B test should really be performed though just to make sure if it sounds better.
 

thorvat

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I thought @abdo123 already employed more than one sub so the graphs were really only of the mains on their own.

The shelving EQ could work well in improving the overall balance as shown in the predicted curves, perhaps… an A/B test should really be performed though just to make sure if it sounds better.

I don't follow him so I have no idea if he emplyed subs or not, but if he did I don't see a reason why they weren't playing with the mains during the measurement.

Speaking of measurement, I didn't catch how he actually did it (MMM, averaged sweeps, single point sweep) and what was the measurement distance.

Regarding the green curve - you don't really need A/B test to see that it can sound better - having the 320-950Hz range playing higher than 100-320 Hz cannot possibly sound good.
 
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abdo123

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I don't follow him so I have no idea if he emplyed subs or not, but if he did I don't see a reason why they weren't playing with the mains during the measurement.

Speaking of measurement, I didn't catch how he actually did it (MMM, averaged sweeps, single point sweep) and what was the measurement distance.

Regarding the green curve - you don't really need A/B test to see that it can sound better - having the 320-950Hz range playing higher than 100-320 Hz cannot possibly sound good.
a 1.5 cm thick curtain will not do anything to frequencies below 100Hz so I didn’t bother turning the subwoofer on.

All my measurements are single point sweeps, no EQ was applied.

I don’t like to EQ the response above 100Hz anyway.
 

thorvat

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a 1.5 cm thick curtain will not do anything to frequencies below 100Hz so I didn’t bother turning the subwoofer on.

All my measurements are single point sweeps, no EQ was applied.

I don’t like to EQ the response above 100Hz anyway.

Curtain will not do anything below 400-500Hz.

Unfortunately single point measurement is pretty much useless to get a relevant picture of anything, unless measuring direct sound of the speaker from close distance using gating.
 
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abdo123

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Curtain will not do anything below 400-500Hz.

Unfortunately single point measurement is pretty much useless to get a relevant picture of anything, unless measuring direct sound of the speaker from close distance using gating.

Well take it or leave it. The good thing about data is that it's not determined by either of our opinions.
 
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