Room with a large window behind the speakers

[Bass13]

Afternoon all,

 

I will be moving my system to a window side of the room,  just wanted to ask any fellow SNA's out there, who have their speakers with a large window behind them. The thickness of the glass, whether it a single pane or double pane, also would have an impact on its reflective characteristics I dare say...

 

Any information regarding what problems you encountered, like windows leaking bass, etc would be appreciated...

Its going to be an interesting test, and a time consuming one to move all my gear & set it up again.

Just trying to get the best position for my system, in a not ideal room, before I treat the room.

 

Thanks in advance...

Edited April 30, 2024 by Bass13

[Guest]

Reflection from rear windows will be a problem, especially if speakers are close.  You can either add absorbers like I did, or add curtains

 

Windows leak bass more than walls. This may be helpful in your room as it could reduce the bass dips but you will need to confirm this by measurements.

[Keith_W]

There are a couple of considerations here. The first is the behaviour of the window. Windows have three "zones" where they interact with sound. The first zone are short wavelengths - these are mostly reflected and very few pass through the glass. The middle zone is the resonance zone, where the window may actually amplify the sound at that particular resonant frequency and radiate it back. They may rattle on their jambs and produce a rattling or buzzing noise. The lowest zone is the bass zone, long wavelengths exert pressure on the window, causing it to flex and store energy. The energy is then released on both sides - back into the listening room, and outside. This causes bass to lose half the energy compared to high frequencies where almost the entire wave is reflected with less attenuation. 

 

Thus the effect of windows is to introduce a spectral distortion - reflections are mostly high frequencies with low frequencies more attenuated. Too many windows can cause a room to have too much of a treble tilt and sound bright. 

 

Windows behave in other ways too - e.g. inadequate window seals can leak sounds outside (and let outside sounds leak inside) which increases your room's noise floor. 

 

So windows may need some treatment. I bought a rubber gasket from Bunnings and applied it around the window frame to reduce air leaks and apply some pressure on the frame to stop it from rattling. Thick curtains help attenuate high frequencies and restores some spectral balance. Or if you have a lot of money, consider double panes. 

 

The next consideration is the behaviour of your loudspeaker. Here are some measurements for you: 

 

 

The red line is the on-axis frequency response from 10Hz - 24kHz. The green line shows the frequency response behind your loudspeaker (i.e. 180deg from the front). This was a quick and dirty measurement that I did when I was at your place to see what was going on behind your loudspeaker, so it has some limitations. I normalized both curves so that max volume is 0dB. 

 

What you can see is the typical behaviour of a monopole speaker. The high frequencies drop off much faster than bass frequencies. Where front = back at 60Hz, by 21kHz the rear wave is -15dB compared to the front. In other words, bass is more omnidirectional, treble is more directional. There is also a huge drop-off at 40Hz, which is more pronounced in the green line (look at where the red and green lines diverge at 40Hz). This is likely SBIR and will probably disappear if the speakers were measured outside. And it will shift depending on how closely you place your speakers to the wall - the closer you place the speaker to the front wall, the higher up the dip will shift. 

 

Your current situation has the windows behind you, so the windows see the red response. This is not good - as mentioned, windows selectively reflect high frequencies, and the red response presents them with more high frequencies. The result will be an upward tilt in the FR making it sound bright. If you rotate the system so that the windows are behind the speaker, the windows will now see the green response - i.e. less energy at high frequencies. You will have the wall behind you where the entire spectrum is reflected with almost the same attenuation. 

 

In short I think you'll be fine. There are quite a few advantages of rotating your system around, not just acoustic ones. You get to enjoy the view out the window whilst playing music. Your speakers no longer obstruct your doors. And so on. 

[Bass13]

Thanks for you info & links @Snoopy8

 

1 hour ago, Keith_W said:

In short I think you'll be fine. There are quite a few advantages of rotating your system around, not just acoustic ones. You get to enjoy the view out the window whilst playing music. Your speakers no longer obstruct your doors. And so on. 

 

Once again, thanks for your time Keith, very much appreciated, this Saturday is moving system day, Mrs wants me to pull everything out of the room as she wants to clean the windows, walls floors, before I put it all back together.

 

I did some measurement's the way I will set it up as there is more room on that side, speakers 1.5 meters from the rear window, currently 1m, and around 3 meters apart, currently 2.6m and 1.5m from each side wall, currently one is 1m the other is about 2.5, as the door ways are in the way.

 

Lets see what she sounds like, it will be more interesting to see what the measurements say too.

[Keith_W]

BTW I found this on another forum: 

 

 

Pay attention to the glass row. See that the coefficient is 0.35 at 125Hz, and 0.07 at 2kHz? For "thick glass" the coefficient is even lower (meaning it reflects more sound). Both materials show a descending coefficient at higher frequencies, meaning that they will produce a treble tilt. 

 

Also note that other materials behave in the opposite way, e.g. brick plaster and ceramic tiles have slightly more 2kHz absorption than at 125Hz. 

 

How did your room rearrangement go?

[playdough]

Recently re arranged my own system which is directly in front of  and hard up to a  brand new 1.6 x 2.7m double glazed unit with awning opening. Window is furnished with a double, day/night blind with internal to reveal pelmet (of my design)

No real appreciable difference noted. No remedial EQ applied. THese windows seem to be quite neutral in room. Way different to a double plastered solid wall.

Edited May 6, 2024 by playdough
gaaaa, spalling auto correct got me again

[Bass13]

 

1 hour ago, Keith_W said:

How did your room rearrangement go?

 

Thanks Keith,

 

Delayed....I've struck a deal with the Mrs, as she's basically letting me manipulate the room how I like with this new setup on the opposite side of the room, we are waiting on a couple of quotes "Tomorrow" as I'm taking down those do nothing blinds in front of the large widow, will putting in some thick double s curtains & behind them will be Holland blinds, obviously my Mrs gets to choose colours for, to make it wife acceptable. We decided it would be easier & safer to move the system after the install.

 

 

[Bass13]

3 minutes ago, playdough said:

Recently re arranged my own system which is directory on front and hard up to a  brand new 1.6 x 2.7m double glazed unit with awning opening. Window is furnished with a double, day/night blind with internal to reveal pelmet (of my design)

No real appreciable difference noted. No remedial EQ applied. THese windows seem to be quite neutral in room. Way different to a double plastered solid wall.

 

There the sort of blinds she wants behind the curtains, that way if I'm not playing music she can open the curtains and have the blinds down to see out & let light in...

[playdough]

11 minutes ago, Bass13 said:

There the sort of blinds she wants behind the curtains, that way if I'm not playing music she can open the curtains and have the blinds down to see out & let light in...

Yep, the DG Unit performs the insulative property of a pleated heavy blackout in my case, with a clean modern looking outcome. (a little bit masculine looking if that's a thing) 

What you propose IMHO will be a neutral thing and better, that will soak/leak bass and the heavy drapes have reasonable co efficient of absorption of varying levels. well through the FR.

Sound choice, may as well call it an actual acoustic treatment, but don't tell the Mrs that, just nod and say yes.

Edited May 6, 2024 by playdough

[Keith_W]

Sounds like a nice plan. Curtains are typically transparent to bass frequencies but attenuate high frequencies. Windows are the other way round, they attenuate bass frequencies and reflect high frequencies. The two should balance nicely. I remember that is a massive window that you have, so in a way you will be getting room treatment that does not look as ugly as typical room treatment. Win-win

[Bass13]

Will be interesting to see what the system sounds like after this, and also what the measurements say too..

Basically the whole side of the room will have double s curtains & blinds behind them and that large thick suede couch gets moved to the opposite wall.

 

Edited May 6, 2024 by Bass13
couch material

[playdough]

The other corner,,,,,,,, required to balance things out

Oven/range hood will move some time the Cabinet Maker actually turns up................Kitchen/lounge reno is such a pita.

[playdough]

THe new system will be white and er, smaller, to appeal to the girls.

White round horn 900mm and 200litres  of curved enclosures (2 x 18")  in figured white washed hardwood veneer, rather than 650 (2 x 21") litres of ripple black, each  

 

 

It'll be the last one,,,,,,,

[Keith_W]

15 minutes ago, playdough said:

THe new system will be white and er, smaller, to appeal to the girls.

 

 

You are mistaken. Girls like it big and black. 

(edit) is that a stovetop on the right with a turntable on top? 

Edited May 6, 2024 by Keith_W

[playdough]

4 minutes ago, Keith_W said:

Girls like it big and black. 

er, well ah,,,,,,noooo, that's thrown a spanner in the works

Tall and white here,,,,,haha

 

Intimidated by the big black system maybe ?,,,,,,, only they know what "thought process" is bouncing around, I just follow their commands.

Edited May 6, 2024 by playdough

[playdough]

46 minutes ago, Keith_W said:

(edit) is that a stovetop on the right with a turntable on top? 

The thing on top of the stove is a surface mount range hood, to go under a series of 8 queen anne Tasmanian blackwood doors, opposite wall to the HiFi. every second cabinet will be stuffed with woolen blankets and XHD bats.

Turntable was sold a couple of months ago to fund the stove  might regret that ,,,,,, although haven't missed it. Still have the records.

[Bass13]

On 06/05/2024 at 1:50 PM, Keith_W said:

Sounds like a nice plan. Curtains are typically transparent to bass frequencies but attenuate high frequencies. Windows are the other way round, they attenuate bass frequencies and reflect high frequencies. The two should balance nicely. I remember that is a massive window that you have, so in a way you will be getting room treatment that does not look as ugly as typical room treatment. Win-win

 

Yes it will be interesting indeed, I've being going nuts researching the material, as there are some curtain materials that work better.

 

One retail outlet below has measurements, which I used as my base line to source the materials weight & composition and cross refence it to what other outlets have.

Acoustic Curtain Fabric

Acoustics: Noise Reduction - Sound Reduction Index (ΔRw) = 7dB, Sound Level Difference (ΔDw) = 9dB (with lining)
Sound Absorption - Noise Reduction Coefficient (NRC) 0.75 
Composition: 100% Polyester
Weight: 365gsm
Width: 2800mm
Light fastness: 5-6 (EN ISO 105 - B02)
Fire rating: Flammability Index 12 (AS 1530.2)

Our best performing Acoustic Curtains achieved a Sound Reduction Index (ΔRw) = 8dB, Sound Level Difference (ΔDw) = 10dB (with lining).

A 5dB noise reduction is clearly noticeable while a 10dB reduction is perceived as reducing the noise by half.

 

I'm just waiting on one more quote, which will make 3....

We cannot go roller blinds behind the curtains as the window in the centre of my large widow is too long, they don't make one that big apparently, so the Mrs settled for a S double sheer instead, behind the curtains.

 

So the curtains material which we picked has a "Noise Reduction Coefficient" NRC 0.71, cross refencing that to the above, its a little less 0.04

With the s/double sheer & s/double curtains and lining behind the curtains too....I will expect very similar results to the above, even if its gets around max 7db.

 

 

Edited May 8, 2024 by Bass13

[almikel]

As long as they don't rattle, and your neighbours aren't annoyed, glass is a great bass trap!

ie glass lets bass out and reflects treble back into the room.

 

From the perspective of good "in room" sound - letting the bass leak out rather than it bouncing around the room is a good thing!

 

Mike

[LogicprObe]

 

Curtains are a winner as you can adjust the sound of your room via opening and closing them!

[Bass13]

On 12/05/2024 at 4:56 PM, almikel said:

As long as they don't rattle, and your neighbours aren't annoyed, glass is a great bass trap!

ie glass lets bass out and reflects treble back into the room.

 

From the perspective of good "in room" sound - letting the bass leak out rather than it bouncing around the room is a good thing!

 

Mike

 

22 hours ago, LogicprObe said:

 

Curtains are a winner as you can adjust the sound of your room via opening and closing them!

 

 

Thanks gents for your input,  its been a longer process than I thought..... just getting a few people in to quote the job, the last two quotes will be tomorrow & Wednesday "total of 4 quotes", that's when the go will be given to build them, which is apparently another 5 to 6 weeks before than can build & install them.

Just trying to finally get my room sorted out, these are the things we music lovers must "eventually" do.

[Bass13]

We have progress....a curtain maker/installer has been appointed, Mrs just needs to finalize the colours and the build of the curtains should begin by next week. 

[playdough]

8 hours ago, Bass13 said:

We have progress....a curtain maker/installer has been appointed, Mrs just needs to finalize the colours and the build of the curtains should begin by next week. 

Well done, should be a good job when done.

[THOMO]

My main listening room has a bay window behind.This is a very good sounding room.It also measures well. have another with no windows-just open behind and that sounds terrible.

Edited May 17, 2024 by THOMO

[Bass13]

11 hours ago, THOMO said:

My main listening room has a bay window behind.This is a very good sounding room.It also measures well. have another with no windows-just open behind and that sounds terrible.

 

 

Thanks for your input & attaching those pictures, I'm just waiting patiently now for the curtains to be built & installed, feeling a tab excited actually cant wait to get this done, and finally setup the room for my system as best as the room lets me.

[Bass13]

Curtains getting installed  tomorrow finally

 

 

Edited June 17, 2024 by Bass13