Cork for acoustic treatment.

[Cactus Studios BC]

I have been doing a little digging around about using Cork for room treatment and I stumbled on a thread here.
https://www.audiosciencereview.com/forum/index.php?threads/using-cork-in-acoustic-treatments.47348/

In all the posting on music and Hi Fi forums about cork I never found anyone doing what I have done. Taking cork flooring and flipping it over to use the backside. The top layer is hard and has been treated so is very reflective. But the back is raw, soft cork.
What is said is that Cork can have a absorption rating of anywhere from 30% to 70%.. I depends on thickness and how it was threated.
The back layer is possibly only 1.5 mm thick but the middle layer is made of soft paper product and then after that you have the back of the surface layer so this is really like having 10 mm overall.
The other part not often mentioned is that the nature of raw cork products like this is it's very cellular and textured so it not only has a potential to absorb sound but more importantly defuse sound.

I was setting to treat this room with a Quadratic defuser and some absorber panels. when my daughter ask me I I wanted all the old cork flooring she was just about to tear up and replace. First thought was that it's going to be pretty bashed up and it's kind of hard. She said I could flip it over.

So I have just completed placing it on the ceiling, my workstation wall and part way along the left and right walls. I ran out of material. The sound in here is actually amazing. I will see where I will need to go from here. For sure I still want a rear wall defuser and then I will experiment with some toss rugs and wall hangings. My purpose for the room is mostly for recording using mikes. But I will also need to listen critically.

 

[Purité Audio]

I would measure before and after to avoid disappointment.
Keith

 

[DVDdoug]

I would measure before and after to avoid disappointment.

YES! "Diagnosis before treatment."!

My purpose for the room is mostly for recording using mikes. But I will also need to listen critically.

It should be good for recording (most things). You generally don't want to record the sound of a small room (smaller than a performance hall) and you can add larger room artificial reverb later if you want.

But maybe not so good for listening. Most "room problems" are in the bass range where the cork won't help. And over-absorbing the mid and high frequencies will throw-off the frequency balance.

 

[holbob]

I would measure before and after to avoid disappointment.
Keith

Bit late now though looking at those photos

 

[Esprit]

I hope you don't have any humidity problems because that way the room "doesn't breathe".

 

[kemmler3D]

Cork is appealing for many reasons and I think your idea of flipping it over probably helps.

Agree with others that measurement is key for getting acoustic treatment right. Based on the pics it's possible you've already pulled out too much treble and upper mid-range. Easy to solve if so, just pull some off the walls or cover with something reflective.

I'll make one pedantic point, which is that you won't get "true" diffusion from cork, because that is defined as even scattering in both space and time and typically requires a surface designed for that. What you will get is some scattering at very high frequency, which can be almost as good as real diffusion as far as it goes.

Will be interested in any before / after measurements you might be able to do, and welcome to ASR!

 

[Cactus Studios BC]

Thank you all for your excellent replies. I'm glad I found this forum. This is my first attempt at actually doing some proper room treatment. I hope you folks can guide me as there's nobody within 300 miles of here that does treatment.
My brief background-
I've been recording for over 40 years now and have never had a properly treated room. But I sort of understood the basics and also the importance of it. I did the best I could in those spaces. I have owned my Yamaha NS 10M's for most of my life. So the room was less of an issue for me in most cases because I know my monitors. I don't normally mix music that requires a sub, mostly it's acoustic music, bluegrass, folk and some country rock. I've produced about 30 albums for clients over those years. I also did live sound for most of that time. I have been in a few professional studios and have read a lot of the books and articles.
Where I'm at-
Yes I have finished putting up the cork but it is mostly on the ceiling and the wall in front of me. It was either the cork or use drywall. There was no realistic reason to test the room the way it was because it was unfinished. There is the kitchen directly above me so in the cavity I had already placed 3.5" rockwool.

Before the cork went up the unfinished room was very dead because of the rockwool ceiling. Now it has what I would describe as "room" reverb time. I sat and played guitar and sang last night and it's defiantly a nice sound for that. Performing in dead rooms is a bit uninspiring. So this is what I think I want, a controlled reflection, defiantly not dead.
So here's my unofficial thoughts on what I might do.

First- you mention testing. Could someone point me to a good tutorial or article that I could see if this is possible. I have a few good condenser mikes and I have a couple of plug ins by Melda Productions and Span that I think I could use. But I have not looked into the actual method. This is an important step to me as now the room is a blank slate.

Second- I feel I want to build a Quadratic diffuser as I sort of like what I've learned about different diffusers. I found a video made by this one guy who actually explained the science behind it and how to properly build one.

Third- I was then going to experiment with the floor. My son used this rubber matting that looks like jigsaw puzzles.

Fourth- I was then going to build some wall panel absorbers.

My room is 11.5' wide and 14' long, the ceiling is 7'1"
Floor is fir plywood.
Ceiling is now Cork
Walls are
left= 1/2 cork- 1/2 ugly pine lumber and the doorway.
Front end all cork, small window in deep well.
Right OSB( chip board) painted and 1/4 cork
Rear wall mahogany ( 1965) wood paneling painted and a closet ( potential bass trap)

 

[kemmler3D]

First- you mention testing. Could someone point me to a good tutorial or article that I could see if this is possible. I have a few good condenser mikes and I have a couple of plug ins by Melda Productions and Span that I think I could use. But I have not looked into the actual method. This is an important step to me as now the room is a blank slate.

This will get you started - you'll probably want to invest in a basic measurement mic (The miniDSP UMIK-1 is very convenient) but earthworks or even Berhinger is usable if you don't want to go the USB route)

Second- I feel I want to build a Quadratic diffuser as I sort of like what I've learned about different diffusers. I found a video made by this one guy who actually explained the science behind it and how to properly build one.

Funny enough I've built one using my 3D printer, it's a lot less work (and weight and money) than doing it with wood, but still a lot of work, pretty heavy, and not exactly free. You can see how I did it in this thread. You will also need some CAD skills to do it this way. I could share my files with you, but frankly they need work and wouldn't be guaranteed to come out right.

However - having done it - building a true QRD might be an example of the last 5% taking 90% of the effort. Based on what I've read, building BAD (binary amplitude) diffusers is much more practical and almost as good, maybe better if you can benefit from low frequency absorption. I'm planning on building some of those in the next couple months if I get my act together.

In general I think you can't have too much diffusion (as long as you're sitting at the correct distance from the QRDs!) but you can easily have too much absorption at different frequencies. Doing measurements with REW will help you know exactly where you're at in that regard, as well as diagnose any existing problems more specifically.

 

[Cactus Studios BC]

Thanks you all for your comments so far.
I bought the Behringer EMC 8000 and have slower figured out how to use REW software as far as taking the measurements. I watched a lot of videos.

I made my first test May 8 when the room was raw and completed with the cork on the ceiling, the front wall and part of each side wall. I then installed the rubber floor matting May 9 and re tested.
My unprofessional conclusion was I needed to put clouds on the ceiling but it is to low ( 7 feet) So I cut four 6'x 14.5" holes in the ceiling to reveal the Rockwool. I then made fabric covers for these. So that is the last measurement made today May 14th includes this first official attempt at treatment.

Here is the groups of screen captures of REW and if anyone has any comments on what exactly I'm looking at I would greatly appreciate the input. I'm only guessing.

I'm using 1 NS-10M centered in the room, sitting on the shelf 46" from floor. Mike is place in center and 48" from monitor and 48" from floor which is my listening position. I'm using 84db measured both with the built in tool and my good ol' Radio Shack Sound level meter C weighted. I leave the room which is mostly empty right now.


My next project was to build a quadratic defuser for the rear wall but??

 

[Alice of Old Vincennes]

Hope your single

 

[Soandso]

The re-cycled cork's inner lamination layer is probably "medium density fiberboard" ("MDF"). Lots of speaker cabinets are constructed with MEF.

MDF has it's own acoustic properties independent of the cork since what MEF doesn't actually absorb can be getting evenly scattered such that sonic reverberations aren't purely angular reflections. In fact I wonder how much of any direct frequencies the inverted cork layer that's 1.5mm thick positioned right next to the wall is actually dealing with according to it's inherent cork properties after whatever the MDF layer's prior dispersal might be.

Top screen shot below is from a cork flooring marketer's website describing the lamination. Last screen shot for orientation being the side view of O.P.'s actual cork flooring.

……………

 

[Cactus Studios BC]

@Soandso Thanks for your reply.
This particular cork flooring is not using MDF in the center. It is high density cardboard/ cellulose? type material. More like packing material or an egg carton.
Looking left to right:
The bottom 1.5 mm layer is pure soft cork. It is easily damaged. This is the side I am using.
The middle 6 mm? layer is high density cardboard/Cellulose.
Then there's the upper layer which is about 3.5 mm of cork
Last is the top layer which is about 1.5 mm very hard treated cork and not so easily damaged.

@Alice of Old Vincennes My wife says she can barley hear me. Remember it's the basement. Above me is the Rockwool and this is a house built like a tank with 2"x10" subfloor then a layer of 1/2" fir subflooring then another 3/16" subfloor and then 1/4" thick vinyl plank flooring. It was recommended in a few videos to use 84db. I normally run much less. As said my system does not produce much bass unless I turn on the sub. That is only for proofing mixes or listening for fun when nobody is home. Bass guitar is one of my main instruments so it's not that I don't like bass. But for serious mixing subwoofers are to be used carefully to look for low end issues or artifacts like a plosives and bumped mike stands. They don't need to be always on.