Absorption only on front wall?

[subframe]

I’m remodelling my living room and have the opportunity to treat the wall behind the speakers with 1.5” - 2” of absorption. Absorption would be PET panels under those felt + slat panels (which are mostly for aesthetics). The other walls in the room don’t allow for significant treatment of any kind.

I have not yet chosen the speakers for the room, but smooth off-axis response will be a hard requirement for whatever I choose.

Since the room is not built yet, I’m not sure if I should take the opportunity to do this, or just build the room un treated, then try to treat after I can measure it. Any thoughts would be much appreciated!

 

[DVDdoug]

I always say, "Diagnosis before treatment". So it's best if you can measure the room first, and again after treatment to make sure you've made an improvement.

Usually the "real problems" are in the bass range and that requires bass traps. Regular "acoustic panels" do absorb much (if any) bass.

 

[sejarzo]

Absorption would be PET panels under those felt + slat panels (which are mostly for aesthetics).

I am unsure what you mean by either of those types of panels. Would it be possible for you to elaborate? Thanks!

 

[RB Dennis 57]

I’m remodelling my living room and have the opportunity to treat the wall behind the speakers with 1.5” - 2” of absorption. Absorption would be PET panels under those felt + slat panels (which are mostly for aesthetics). The other walls in the room don’t allow for significant treatment of any kind.

I have not yet chosen the speakers for the room, but smooth off-axis response will be a hard requirement for whatever I choose.

Since the room is not built yet, I’m not sure if I should take the opportunity to do this, or just build the room un treated, then try to treat after I can measure it. Any thoughts would be much appreciated!

In theory, absorptive in close, then diminishing to reflective further away. Diffusers can be used to control, but not eliminate reflections, perhaps at the mid-points.

 

[subframe]

I am unsure what you mean by either of those types of panels. Would it be possible for you to elaborate? Thanks!

Certainly.

Examples of PET panels from Autex: https://www.autexacoustics.com/products/quietspace-panel and from Fsorb: https://www.f-sorb.com/technology

Slats are from here: https://www.thewoodveneerhub.com/co...ts/slatpanel-walnut-acoustic-wood-wall-panels and you can see some discussion here too: https://www.audiosciencereview.com/...th-slats-before-and-after-measurements.42559/

 

[sejarzo]

Thanks!

Is that 9mm felt so thick that it would block sound from reaching the PET panels? The general recommendation is that whatever fabric one opts to cover rigid fiberglass panels must be very open (like burlap or material specifically produced for absorber covers) or it renders the underlying material far less effective.

 

[sejarzo]

In theory, absorptive in close, then diminishing to reflective further away. Diffusers can be used to control, but not eliminate reflections, perhaps at the mid-points.

With the assistance of my wife to do the seamstress part of the project, we built a lot of absorbers for a basement HT room that turned out to be highly reflective. When I put a 2" Owens Corning 705 panel at the first reflection point of my speakers, it created a 6 dB peak suckout from 550-1000Hz. So yes, one must be careful with placement of absorption.

 

[DanielT]

Not just front wall. Here's a video about early lateral reflections and a quote from an acoustician who comments on the video and gives concrete tips and advice on what to do with your home HiFi:

I-or:

"It has been known, and well described scientifically, for at least 40 years that high levels of early lateral reflections confuse hearing and should be kept low. However, the conditions in two-channel listening rooms are completely different from concert halls, which is why one should be very careful with comparisons here.

In practice, this means that you should mount absorbers at the first reflection area on the side walls or use textile panels or thick curtains/drapes if you want to optimize your listening room. An area of approx. 0.5-1 m2 is sufficient and in addition it is most important to have good absorption from approx. 1 kHz and up, which is why it is reasonable to have an absorbent thickness of approx. 4 cm. More low-frequency reflections are conveniently handled via equalization."

faktiskt.io • Logga in

 

[sejarzo]

There are definitely two schools of thought in that regard. I see diffusers at the first reflection point rather than absorbers.

Boston Symphony Orchestra Control Room - WSDG

32nd TEC AWARD WINNER! Overview A cultural icon for 134 years, the Boston Symphony Orchestra is world-renowned for the excellence and diversity of its performances. Broadcast from Symphony Hall, via radio, TV and the Internet, these symphonic and ‘Boston Pops’ concerts encompass the entire...

wsdg.com

 

[tuga]

There are definitely two schools of thought in that regard. I see diffusers at the first reflection point rather than absorbers.

Boston Symphony Orchestra Control Room - WSDG

32nd TEC AWARD WINNER! Overview A cultural icon for 134 years, the Boston Symphony Orchestra is world-renowned for the excellence and diversity of its performances. Broadcast from Symphony Hall, via radio, TV and the Internet, these symphonic and ‘Boston Pops’ concerts encompass the entire...

wsdg.com

Three schools of thought. There's also deflection of the Reflection-Free Zone design:

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/RPG_Diffusers/Presentations/Studio%20Design%20From%20Mono2Surround.pdf

 

[sejarzo]

Three schools of thought. There's also deflection of the Reflection-Free Zone design:

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/RPG_Diffusers/Presentations/Studio%20Design%20From%20Mono2Surround.pdf

Works in a control room, but likely not applicable to 99+% of home listening rooms.

 

[amirm]

1.5 to 2 inches will only absorb high frequencies of which there is not a lot behind your speakers. Whether you need that kind of absorption there depends on how much you have overall. If the room is already dead, you don't want to put more there.

 

[subframe]

1.5 to 2 inches will only absorb high frequencies of which there is not a lot behind your speakers. Whether you need that kind of absorption there depends on how much you have overall. If the room is already dead, you don't want to put more there.

Yeah, I worry about taking too much high frequency energy out of the room without any mid or low absorption to go along with it. In this room, the side walls are mostly glass with some drywall, and the back opens to kitchen, so the speakers will see wood and tile. there will be rug and furniture in front of the speakers, and it may be possible to add minimal ceiling treatment at that first reflection point if ceiling bounce ends up being very problematic. The front wall is the only location i can place any significant treatment at all.

However I wonder if its better to actually not install anything on the front wall at all, to avoid skewing reflections and/or just wasting money.

 

[ozzy9832001]

I'd run some measurements first. Honestly, the panels are pretty thin and not going to do much for LF sound. Even at 4", probably still wouldn't do much. I'd probably say, don't bother. In my small room, I have the front wall treated and the corners (ceiling and walls), but I get awful resonances building up in the corner it's murder on my ears. Even then it took alot of thick treatments to make a dent in it.

 

[DanielT]

There are definitely two schools of thought in that regard. I see diffusers at the first reflection point rather than absorbers.

Boston Symphony Orchestra Control Room - WSDG

32nd TEC AWARD WINNER! Overview A cultural icon for 134 years, the Boston Symphony Orchestra is world-renowned for the excellence and diversity of its performances. Broadcast from Symphony Hall, via radio, TV and the Internet, these symphonic and ‘Boston Pops’ concerts encompass the entire...

wsdg.com

Three schools of thought. There's also deflection of the Reflection-Free Zone design:

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/RPG_Diffusers/Presentations/Studio%20Design%20From%20Mono2Surround.pdf

Maybe a little OT for this thread but it's a fascinating topic. Acoustic treatment in concert halls, opera houses that is. I don't know how much of what the acousticians work with in those cases you can copy to your own listening room at home, but you might be able to get some ideas.

odeon.dk
https://odeon.dk › pdf › Exto...PDF
THE ROOM ACOUSTIC DESIGN OF THE GUANGZHOU OPERA HOUSE
(for some reason I can't paste the pdf link, I took a screenshot and attached a picture how to find it via googling)

Another example:

Testing the Concert Hall’s acoustic reflectors

Work is underway to make the Opera House sound as good as it looks. Meet the acousticians solving a 40 year-old problem.

www.sydneyoperahouse.com

 

[Bjorn]

It's going to help break up flutter echo. But overall the treatment is quite poor and could have done much better.

You're saying it's only place you can have treatment. That's very unfortunate but the question is if it's really true. If one can have paintings or pictures, one can also have treatment.

 

[subframe]

It's going to help break up flutter echo. But overall the treatment is quite poor and could have done much better.

You're saying it's only place you can have treatment. That's very unfortunate but the question is if it's really true. If one can have paintings or pictures, one can also have treatment.

Fair enough. There are small sections of side walls behind the listening position that could host some absorption or small diffusers. That’s truly the only other location, though, and it’s not obvious to me that treatment there would be helpful.

 

[DanielT]

But if you are going to absorb the sound with the help of textile panels or thick curtains/drapes, you have every opportunity in the world to fix an aesthetically pleasing solution. Colors, shapes, patterns, maybe with motifs, something artistic and so on. Only the imagination sets the limits.

Floor reflex, as usual thick carpets in front of the speakers.

The most difficult to solve is the first reflection from the ceiling. In any case, if you are now thinking about putting something up on the ceiling. It might look a bit strange. Or not. It depends on taste regarding the aesthetic.

How much reverb and accompanying damping you like is also a matter of taste.Having said that, few people like the extremes, such as a completely bare, unfurnished room for example (as the base for sound reproduction).

Speaking of creativity. Here it flows regarding diffusers:

Wood acoustic diffusers have become a decorative item - loved the idea!

Hi As an acoustician I am tired to tell people not to think room treatment only as absorption. In most small rooms absorption often creates more issues than it solves. Diffusion is a better solution. However, all I hear: they are expensive, ugly and difficult to place in a room. I am hence...

audiosciencereview.com

 

[Bjorn]

Fair enough. There are small sections of side walls behind the listening position that could host some absorption or small diffusers. That’s truly the only other location, though, and it’s not obvious to me that treatment there would be helpful.

If placed at the reflection points, it's going to make a big difference actually Possibly more than the treatment you're planning on the front wall with many speakers.
Type of treatment will depend on distance and partially on taste.

 

[Bjorn]

The most difficult to solve is the first reflection from the ceiling. In any case, if you are now thinking about putting something up on the ceiling. It might look a bit strange. Or not. It depends on taste regarding the aesthetic.

I think it can look quite nice but taste will vary.