Acoustic treatment with slats - before-and-after measurements

[S0crat3s]

I am trying to DIY my way into building a similar slat panel like the GIK SlatFusor 2S. My theater acoustics require certain areas to have a combination of Owens Corning 703 and aluminum Foil tape. See below, the areas roughly marked in yellow is where i need to add the OC703 with Aluminium foil tape. I have an option to add GIK SlatFusor 2S as well there. Its a large area on both the sides of the wall and that will cost quite a bit, hence I am thinking if i can install OC703 and on top of it add a felt sheet and wooden slats. Will that be similar?

 

[keenly]

Wood slats reflect some highs and look good, that is ok for putting in front of deep absorbers but otherwise not much use on their own.

 

[nathan]

I’m coming late to this party so apologies if I missed something in my first read of the thread. I’m seeking clarity with my comments, not to win an argument. I’m still an active learner…..

Nice!

If you add a 1,5x3 meter 15cm thick ceiling absorption frame/panel with polyesterwool, things will improve beyond belief. You will be in hifi heaven.

Something like this, but then bigger. https://fixthisbuildthat.com/easiest-diy-acoustic-panels-under-20-bucks/

Yep, these are great if you add a few inches of absorption behind them to reach down into the transition frequency of the room (and a bit below).

I hate to be a party pooper, but slats aren't really a serious acoustic treatment for music. In regards to minimize flutter-echo for speech it's fine. But for music we want either absorption or diffusion or normally a combination. Slats don't function well at neither.

That being said, if that's only treatment one can do because of WAF, it's certainly much better then a flat reflective surface. A RT60 measurement is invalid in a small room like this BTW.

It’s not the slats, but the gaps and the material in there, that is doing most of the heavy lifting. And while technically RT60 isn’t valid for domestic rooms, Reflected Decay Time as a general concept is. Thats why CTA, CEDIA, and others have defined optimum targets for it for home theaters:

The technique is also described in the attached screen shots. I won’t clutter the thread by posting those in line, too.

Finally Dolby has published guidelines for the same kind of targets in mastering suites….which are very similar.

 

[nathan]

It is in the calculator:
View attachment 271240

But polyester is completely harmless. Bulk PET for inner layer and thin, say 1-2", plates as coverage?..

I personally use double bass array for LF absorption)). But I wonder what the people can do with absorbers.

Works great for the range covered by the subs. But in most domestic rooms that means 100 to 300 hz still has room mode issues. Luckily that tends to be where panels of workable depth can start to help right?

 

[nathan]

Please look at the absorption charts. They only work for voice frequencies.

View attachment 271253

Others seem pretty impressive down to the region where active mode management with subs kick in no?

 

[nathan]

I am trying to DIY my way into building a similar slat panel like the GIK SlatFusor 2S. My theater acoustics require certain areas to have a combination of Owens Corning 703 and aluminum Foil tape. See below, the areas roughly marked in yellow is where i need to add the OC703 with Aluminium foil tape. I have an option to add GIK SlatFusor 2S as well there. Its a large area on both the sides of the wall and that will cost quite a bit, hence I am thinking if i can install OC703 and on top of it add a felt sheet and wooden slats. Will that be similar?

View attachment 339566

View attachment 339567

The main caveat is that it is possible to introduce comb filtering since all the slats are the same size and have the same spacing. It is not inevitable, but the variables (like slat size, slat spacing, and or distance between listeners and the walls the slat-covered-fiberglass is on, to avoid issues created by being too close to the slats) are not well documented from what I have found.

 

[nathan]

Wood slats reflect some highs and look good, that is ok for putting in front of deep absorbers but otherwise not much use on their own.

Though they tend to mitigate over absorption of high frequencies by providing some reduction in absorption of high frequencies, right?

 

[Jost Buergi]

This page in German by Bert Kößler has some detailed analysis on Slat "absorbers" which are so accessible theses days.

His bottom line - not that it would surprise us much:
1. The felt layer of 12 mm or so is much too thin in order to absorb mid or even low frequencies. So the felt rather works like a carpet.
2. Absorption can be extended a bit to lower frequencies if you add some space between panel (felt) and wall. Note: this is the case with others absorbers like Basotect, too.
3. The MDF slats don't add much acoustically except reducing the absorption above 2 kHz. So what you end up with is a narrow absorption range around 1 or 2 kHz:

EDIT: blue curve = on wall, green curve = 20 mm away from wall.

As Bert Kößler put it: not very helpful for Home Cinema or Stereo applications - but still better than nothing. Or as one might conclude: a possibly useful addition to your room if you want to reduce reverb just in that area.

 

[Bjorn]

Beware of measurementing data shown by manufacturers here. I just so one with felt showing very good absorption down to 400-500 Hz. That's simply not the case and is clearly misleading.

But slats do work decent to reduce flutter echo. So if the goal is simply to reduce some noise in a room to make it better when several are speaking (or kids playing) the treatment is ok. However, for music and hifi it's a no go IMO.

 

[janbth]

This page in German by Bert Kößler has some detailed analysis on Slat "absorbers" which are so accessible theses days.

His bottom line - not that it would surprise us much:
1. The felt layer of 12 mm or so is much too thin in order to absorb mid or even low frequencies. So the felt rather works like a carpet.
2. Absorption can be extended a bit to lower frequencies if you add some space between panel (felt) and wall. Note: this is the case with others absorbers like Basotect, too.
3. The MDF slats don't add much acoustically except reducing the absorption above 2 kHz. So what you end up with is a narrow absorption range around 1 or 2 kHz:
View attachment 396847

As Bert Kößler put it: not very helpful for Home Cinema or Stereo applications - but still better than nothing. Or as one might conclude: a possibly useful addition to your room if you want to reduce reverb just in that area.

Yes, this seems to match the before-after difference in the frequency response I measured in my room, see post #71. («Ohne Wandabstand» means «without distance to the wall», or something like that…)

 

[jaakkopetteri]

This page in German by Bert Kößler has some detailed analysis on Slat "absorbers" which are so accessible theses days.

Unless I'm missing something, I don't think basic online sims count as "detailed analysis". In-room measurements tend to show improvement extending way lower than sims, though measurements aren't a perfect tool either

 

[Jost Buergi]

(«Ohne Wandabstand» means «without distance to the wall», or something like that…)

Yes, thank you. I just edited that in.