Looking for suggestions on whether to put curtains behind speakers or not. I am happy with my set up but always wonder how it might sound (?better) with curtains behind the speakers. I have a large room with lots of windows. The windows behind speakers do shudder a bit with louder volumes/base but don't usually listen at such levels. The soundstage I get is great but the sound is somewhat bright compared to a friends similar set up in a smaller room with no windows and I always envy his sound even though he has the 802s instead of the 801s - it is a richer sound with great depth.

 

Would curtains improve things or deaden the sound?

Any particular type of curtains? Blinds or thick curtains?

Any other suggestions for room treatment that might help - been wondering about acoustic reflection panels instead of those red lights hanging from ceiling.

Any suggestions how I can try things out before committing to curtains?

 

Always had great help from these forums so thanks in advance.

Edited September 28, 2025Sep 28 by Cigar nuke

Hi, this brand of speakers has a reputation of being "bright" with a higher that flat measurable upper frequencies on-axis. This should be somewhat reduced by not listening on-axis like you are doing now. So, before doing anything else I think you should try aiming the speakers straight into the room with the side walls so you end up listening off-axis.

I'm sure @Keith_W can speak to the fundamentals involved here.

Getting bass effects from the rear windows—are the 801s rear ported? Something to eliminate those out-of-time window reflections will help with the overall sound image, if not with perceived brightness.

Hi and thanks for tagging me @Steff. 

 

Lots of glass makes the room sound bright. The reason is because they are membrane absorbers - they absorb certain wavelengths depending on the resonant frequency. Some of the energy is converted to heat, but the rest is re-radiated into the room at the resonant frequency. At the same time, high frequencies are reflected back into the room with no absorption at all. The nett effect is to reduce bass in the room (good), maybe creating some resonant bass frequencies (bad) and leaving the higher frequencies untouched (also bad). 

 

As @Satanica mentioned, this brand of speaker is also known for a bright top end which would compound the problem. His advice to toe them out might work depending on your listening triangle. 

 

Curtains are a very good idea. Some acoustic curtains are rated according to the NRC (Noise Reduction Coefficient). The best way to choose your curtains is to take some acoustic measurements so that you have some idea what frequencies need to be absorbed and what needs to be left alone. Of course you could wing it and guess, but results are rarely as accurate. I am more than happy to visit you and take those measurements and discuss what they mean. Or you could pay a professional acoustician (someone like Corsini) who would do a much better job than me, since he does it for a living and I do it as a hobby and for fun! 

On 28/09/2025 at 1:49 PM, Keith_W said:

Lots of glass makes the room sound bright. The reason is because they are membrane absorbers - they absorb certain wavelengths depending on the resonant frequency. Some of the energy is converted to heat, but the rest is re-radiated into the room at the resonant frequency. At the same time, high frequencies are reflected back into the room with no absorption at all. The nett effect is to reduce bass in the room (good), maybe creating some resonant bass frequencies (bad) and leaving the higher frequencies untouched (also bad). 

 

 

Hey @Keith_W, In acoustic modelling glass is typically treated as a highly reflective surface. 

Its ability to act as a membrane absorber, if at all, is debatable. 

But I agree glass is more leaky than a standard timber stud/plaster wall, and as such, will allow bass energy to exit.  

 

IMHO.... The surface should be viewed as a reflective surface, and acoustically treated as such.   

 

I would consider adding decently heavy curtains [whatever your wife will allow] to the rear and side walls. 

You could easily test this scenario, draping multiple/heavy blankets over the windows. 

 

You might also consider inset panel absorption over head, 40-50mm with a 10-20mm air gap [Larger gaps, allow the panel to operate lower in frequency], positioned between the beams, on the reflection axis to your seated position. This should help absorb frequencies down to lower midrange frequencies, subject to panel type and gap used.  

 

DSP would also help address final frequency response issues. 

 

Edited September 29, 2025Sep 29 by Grizaudio
A few extra points added.

@Cigar nuke 

 

Really nice room!

 

is EQ an option?

Based on @Satanica's comment that your speakers have a reputation for being "bright", EQ could dial that down before the sound leaves the speakers, essentially fixing the issue at the source.

 

@Satanica's other suggestion of listening "off-axis" should also reduce the "brightness" of the direct sound at the listening position.

 

Curtains will also significantly help to absorb top end if the sound at the listening position is still too bright - but I would target placing curtains at the 1st reflection points for the tweeters, and definitely not behind the speakers.

 

As @Keith_W says, glass is good for letting bass out, but reflects treble back into the room - IMO glass is a fantastic bass trap so long as the glass doesn't rattle, and you don't annoy your neighbours with the amount of bass leaking out.

 

On 29/09/2025 at 10:23 PM, Grizaudio said:

In acoustic modelling glass is typically treated as a highly reflective surface.

As you say, not for bass frequencies - glass lets bass straight through - which IMHO is awesome for achieving great "in room" bass, as the bass doesn't remain inside the room bouncing around taking ages to decay.

 

On 29/09/2025 at 10:23 PM, Grizaudio said:

Its ability to act as a membrane absorber, if at all, is debatable. 

But I agree glass is more leaky than a standard timber stud/plaster wall, and as such, will allow bass energy to exit.

Glass is a membrane absorber the same as a stud/Gyprock wall is a membrane absorber, just with different frequencies of operation.

 

On 29/09/2025 at 10:23 PM, Grizaudio said:

I would consider adding decently heavy curtains [whatever your wife will allow] to the rear and side walls. 

I agree with adding curtains to the side walls, but why add curtains to the rear walls behind the speakers to tame bright speakers?

Better to add curtains behind the listening position to damp 1st reflections from the tweeters, as the tweeters are not directing any sound backwards.

 

Mike

10 minutes ago, almikel said:

@Cigar nuke 

 

Really nice room!

 

is EQ an option?

Based on @Satanica's comment that your speakers have a reputation for being "bright", EQ could dial that down before the sound leaves the speakers, essentially fixing the issue at the source.

 

@Satanica's other suggestion of listening "off-axis" should also reduce the "brightness" of the direct sound at the listening position.

 

Curtains will also significantly help to absorb top end if the sound at the listening position is still too bright - but I would target placing curtains at the 1st reflection points for the tweeters, and definitely not behind the speakers.

 

As @Keith_W says, glass is good for letting bass out, but reflects treble back into the room - IMO glass is a fantastic bass trap so long as the glass doesn't rattle, and you don't annoy your neighbours with the amount of bass leaking out.

 

As you say, not for bass frequencies - glass lets bass straight through - which IMHO is awesome for achieving great "in room" bass, as the bass doesn't remain inside the room bouncing around taking ages to decay.

 

Glass is a membrane absorber the same as a stud/Gyprock wall is a membrane absorber, just with different frequencies of operation.

 

I agree with adding curtains to the side walls, but why add curtains to the rear walls behind the speakers to tame bright speakers?

Better to add curtains behind the listening position to damp 1st reflections from the tweeters, as the tweeters are not directing any sound backwards.

 

Mike

Thank you Mike. 
 

All great tips. Behind me (as I listen to my system now) are stairs to downstairs cinema and a bar. So curtains behind me not an option.

 

I think I will go with someone like corsini but we need to renovate so don’t want to do that just yet. I might start with the cinema which really needs some treatment and no further renos planned (pics attached - I’m pretty proud of the design which I did myself - used to be a second garage).

@Cigar nuke - a lovely listening room and a home cinema - I'm going to STFU

Edited October 18, 2025Oct 18 by almikel
typo

No don’t STFU. I’d appreciate thoughts on my untreated cinema. The ‘ole hand clap test still has a lot of echo. I could buy some random acoustic panels and glue ‘em on the walls but would prefer a more “scientific” approach….and something appropriately aesthetic

 

I haven’t shown the study hifi yet 🤣🤣🤣🤣

Edited October 18, 2025Oct 18 by Cigar nuke

1 hour ago, almikel said:

I agree with adding curtains to the side walls, but why add curtains to the rear walls behind the speakers to tame bright speakers?

Better to add curtains behind the listening position to damp 1st reflections from the tweeters, as the tweeters are not directing any sound backwards.

 

You are correct to point out high frequency energy is quite directional, but perhaps you are overlooking the impact of secondary delayed reflections? 

 

With any room, I would highly recommend taking measurements [impulse/step response] to investigate what's happening at listening position. 

Depending on what energy is doing in time, DSP 'might/could' be an easy solution without introducing dampening.   

 

Anyway, curtains behind the speakers will noticeably help tame frequencies above say 500hz [including unwanted high frequency] from secondary and primary wrap around reflections. 

So yes they would make quite a considerable difference. Its a very easy scenario to try with heavy blankets.  

 

But I agree, treatment to the wall behind the listening position, would address primary 'HF' energy reflecting [but that wall/space isn't shown in the pictures].  

 

2 hours ago, almikel said:

Glass is a membrane absorber the same as a stud/Gyprock wall is a membrane absorber, just with different frequencies of operation.

 

The ability for glass to act as a membrane absorber is negligible compared to its ability to reflect.

Glass is primarily reflective, with a very high reflection co-efficient.  90-95% of midband energy up will be reflected. 

Energy absorption through vibration is minimal, offering little practical control over sound compared to treatments like curtains or acoustic panels.

As it turns out, I just made this post on another forum. So i've cut and pasted it for your benefit. 

 

--- 

 

I have wondered for some time whether reverberant fields actually exist in listening rooms. Dr. Toole says that the RT60 should be renamed "early reflection decay", because small rooms have specular reflections and not reverberant fields. But ... a 20kHz wavelength is 17.2mm, surely that is short enough to form a reverberant field, as well as specular reflections? And given that specular reflections become more diffuse as you get further from the wall, at what distance do they become "not specular"? 

 

A reverberant field is supposed to measure the same no matter where in the room it is measured. I have made this theoretical point to others. And given that I am writing a REW guide, I decided to test this theory.

 

 

So I got the microphone out and took measurements from 6 positions. At MLP, 1m behind MLP, and 2m to the left and right ... as shown in the photo.

 

 

I then overlaid all the measurements and selected Topt. Now we look to see where the measurements diverge. As you can see, they are all fairly tightly bunched down to 600Hz, which is where they start to diverge. In my room, the Schroder frequency is 133Hz, which means the transition zone ends at about 532Hz. Nice to see the measurement following theory!

 

As you can see from my photo, I did not bother moving furniture out of the way when taking these measurements. This is why we have some specular reflections at 1.6khz and 2kHz.

 

What is surprising is how "dry" the bass is. The room has five smaller windows, one almost full-height picture window, and large openings to an adjoining staircase and the dining room. Plenty of opportunity for bass to escape. I guess this is why the bass is so "dry". As for that huge spike at 50Hz, that's the noise floor. I thought I could avoid it by measuring loud and long, but it looks like I didn't. 

 

So there you go ... "proof" that reverberant fields exist in small rooms. At least down to 600Hz in my room.

3 minutes ago, Grizaudio said:

The ability for glass to act as a membrane absorber is negligible compared to its ability to reflect.

Glass is primarily reflective, with a very high reflection co-efficient.  90-95% of midband energy up will be reflected. 

Energy absorption through vibration is minimal, offering little practical control over sound compared to treatments like curtains or acoustic panels.

 

We can test that. Put your microphone on the other side of the window (outside) and run a sweep. Then open the window and re-measure from the same position. I'll bet you mostly see bass frequencies. At least, that's what I hear when I am in my backyard with the music playing. 

Edited October 18, 2025Oct 18 by Keith_W

Just now, Keith_W said:

 

We can test that. Put your microphone on the other side of the window (outside) and run a sweep. I'll bet you mostly see bass frequencies. At least, that's what I hear when I am in my backyard with the music playing. 

 

I'm talking in the context of helping the gentlemen's high frequency issues @Keith_W

6 minutes ago, Keith_W said:

What is surprising is how "dry" the bass is

Looks good to me Keith... Not sure why you would call it dry... Decay looks about perfect. 

40 minutes ago, Keith_W said:

So there you go ... "proof" that reverberant fields exist in small rooms. At least down to 600Hz in my room.

 

@Keith_W I haven't read Toole's work on this subject.

I'm trying to understand your findings, in the context of Toole's theory.

 

Do you think Toole was referring to "how the reflections behave in space - Large vs small? "

 

I.e.  in a large spaces [Like a concert halls] reflections come from everywhere, and arrive to the listener dense and smooth.... whilst in a small room you are only dealing with a few dozen reflections, and they are more directional / less dense and smooth? I.e. not a true reverberant field? 

Edited October 18, 2025Oct 18 by Grizaudio

Ummm, i'll have to find the reference in the book and get back to you on that one. 

32 minutes ago, Keith_W said:

Ummm, i'll have to find the reference in the book and get back to you on that one. 

cool I’ll look up Tooles book too…. 
 

As you know I advocate for nearfield listening…. Which naturally promotes a short decay, direct field dominant listening experience (free from a lot of these concerns). 

 

On 18/10/2025 at 9:12 PM, Grizaudio said:

 

The ability for glass to act as a membrane absorber is negligible compared to its ability to reflect.

Glass is primarily reflective, with a very high reflection co-efficient.  90-95% of midband energy up will be reflected. 

Energy absorption through vibration is minimal, offering little practical control over sound compared to treatments like curtains or acoustic panels.

 

So I have taken the time to read about membrane absorbers.... a little more to improve my understanding.  

This link provides a good overview of the narrow band absorption properties for glass - in bass frequencies. 

https://www.troldtekt.com/product-advantages/good-acoustics/advanced-acoustics/different-absorber-types/

 

 

On 19/10/2025 at 9:39 PM, Grizaudio said:

 

So I have taken the time to read about membrane absorbers.... a little more to improve my understanding.  

This link provides a good overview of the narrow band absorption properties for glass - in bass frequencies. 

https://www.troldtekt.com/product-advantages/good-acoustics/advanced-acoustics/different-absorber-types/

 

 

I've always regarded glass in the binary - it lets bass out of the room and reflects treble back into the room - but obviously this is a simplistic view.

Across the audio spectrum of 20Hz to 20kHz, glass will go from acoustically transparent at lower frequencies, through operating as a membrane absorber, to reflecting higher frequencies back into the room.

 

No-one is suggesting glass is a good material to use as a membrane absorber!

 

From my perspective, I regard glass as the ideal bass trap - it lets bass pass through but reflects treble back into the room, preventing the "in room" sound becoming too dead (assuming you have tolerant neighbours).

 

cheers,

Mike

20 minutes ago, almikel said:

acoustically transparent at lower frequencies

No window is truly transparent. The glass must vibrate, and its mass resists motion.

So the energy transmitted is no where near 1:1. More like 30-50% of sound power at 20hz. [This has been my reading].. 

At the end of the day.... at low frequencies, transmission occurs because the glass moves as a piston, not because sound 'ignores' it.

Edited November 2, 2025Nov 2 by Grizaudio

A quick and simple thing you can do to test if Curtains would make a difference is to use Sheets, then Blankets, then a Doona/Quilt and have a listen. If you hear improvements with one, you'll know if thin, medium or thick curtains would be best for your room.

 

Personally, I've never liked uncovered windows behind speakers, for whatever scientific reason the sound is just wrong to me.

On 18/10/2025 at 8:13 PM, Keith_W said:

So there you go ... "proof" that reverberant fields exist in small rooms. At least down to 600Hz in my room.

Of course "reverberant fields" exist in small rooms - we have room modes in our small rooms, as science predicts.

 

What we don't have in our small rooms is a "diffuse" acoustic response - the pioneering work done by Wallace Sabine (the father of acoustic engineering), who invented the RT60 metric in 1895, based his maths on a diffuse sound field in large auditoriums (using a stop watch and bringing students in with seat cushions).

 

In our small rooms we have room modes and specular reflections to manage.

RT60 is not a particularly useful measurement in a small room - because a diffuse sound field doesn't exist.

 

42 minutes ago, Grizaudio said:

At the end of the day.... at low frequencies, transmission occurs because the glass moves as a piston, not because sound 'ignores' it.

Not true.

Low frequencies pass through glass - nothing to do with the glass operating as a "piston".

 

Mike

1 hour ago, Grizaudio said:

At the end of the day.... at low frequencies, transmission occurs because the glass moves as a piston, not because sound 'ignores' it.

That would support the idea that glass makes a good membrane absorber, which I accept is a bad idea.

 

Mike

15 hours ago, almikel said:

Not true.

Low frequencies pass through glass - nothing to do with the glass operating as a "piston".

 

Mike, I believe it is you who is incorrect. 

 

For a sound wave to propagate, air particles must vibrate. 

For instance, when you travel behind a doof doof car, the whole car is acting like a speaker cone, vibrating and transferring acoustic energy from inside the cabin to outside the cabin. 

Sound can't magically propagate on one side of a surface to another, without air particles continuing vibration transfer. 

No particle motion = no sound   

 

@Keith_W correct me if I am mistaken. 

 

 

 

Edited November 3, 2025Nov 3 by Grizaudio