Polyester fiber panels/boards, do they work?

[dfira]

Searched the forum for 'polyester fiber' returned nothing. Thinking of picking up a few cheap from china to absorb the early reflections caused by an extremely cramp recording environment.

Only recording vocals, so don't need the greatest bass extension. How do these compare to foam panels?

Cheers.

[Mike Stranks]

Searched the forum for 'polyester fiber' returned nothing. Thinking of picking up a few cheap from china to absorb the early reflections caused by an extremely cramp recording environment.

Only recording vocals, so don't need the greatest bass extension. How do these compare to foam panels?

Cheers.

Can't comment on 'polyester fibre'... My space is fitted out with a selection of these: https://www.studiospares.com/studio-gear/acoustic-panels/studiospares.htm

in various sizes.

Where space permits I've fixed them 1"/2.5cm away from the wall to increase their effectiveness.

My space is used for recording spoken word and some mixing/balancing.

If the room was bigger, I'd have used Rockwool panels, but I need every inch/cm I can get!

Your comment about bass may be misplaced. Even though my small room is well-treated and suits my purposes I do have to be careful about bass nodes. These are almost impossible to deal with adequately in a small room. Stand/sit in one of these and you'll have a completely false impression of what's happening in the room and through the speakers.

[dfira]

Hi Mike, thanks for your input.

Yes i got bass problems but only a few dbs here and there, and because I'm not mixing music, only recording voice, i think i can live with them.

I want some rockwool panels too, and I'll probably end up getting one or two eventually, but my mike sits on my desk, in the corner of the room. It's that corner that i need to be primarily concerned with.

[Watchmaker]

Try looking up the "absorption coefficent" for polyester. I've never seen it, but we could fill most of the universe with what I don't know.

[dfira]

Try looking up the "absorption coefficent" for polyester. I've never seen it, but we could fill most of the universe with what I don't know.

That was a well recommended google! Thank you.

But the information is vast. I guess i could always just throw 20 quid at the problem and see how it goes... I think doing the research properly is going to cost me £20+ in time!

[Sam Spoons]

My uneducated take is that foam panels vary for the 'least worse' ('proper' open cell foam acoustic panels of a decent thickness and from a reputable manufacturer) which can work reasonably well to thin, cheap, closed cell foam panels from China which are fairly useless.

Thickness (between the outward facing boundary of the panel and the wall/ceiling) is what determines the lowest frequency the panels will absorb/control, how effectively it absorbs above that frequency depends on the properties of the materials used and how much of that 'thickness' is absorbing material and how much an air gap behind the panel.

Given that the duvet trick works, and most duvets are filled with polyester fibre, I'd bet it will be good enough to give a significant improvement over an untreated room but OTOH Rockwool is not expensive so trying to substitute a different, unproven, material seems a bit pointless.

[CS70]

Yes they do - obviously it'll depend on their geometry but otherwise open cell polyester is a good base material.

Edit: there's a lot of info online, google something like "absorption coefficient polyester" and add "mineral wool" if you want to compare.

[dfira]

What is OTOH?

Regarding getting something like rockwool. Yeah that would be preferable, but I actually find it rather difficult to source, I'm a little concerned with the toxicity, and I would want it in rather odd sizes (small and thin panels).

[Moroccomoose]

OTOH ='On the other hand'

[Sam Spoons]

OTOH, wot ee sez, sorry...

Polyester fibre will probably be very low density so will be less effective than a similar thickness of Rockwool RW3. But, like I said above, it will work, just not as well.

Regarding size/thickness Rockwool cuts very easily and RW3 in particular is easy to work with as it is rigid enough to support itself without sagging (at 'normal sizes at least). It comes in 1200 x 600 mm sheets in various thicknesses* and 50mm is probably the thinnest I'd suggest fo a balanced sounding room.

There are no significant health risks with mineral wool, it is inert, non-toxic and it's fibres are of a size that does affect the lungs in the way that asbestos does. It can cause skin irritation when handled and the fire resistant doping contains, IIRC**, formaldehyde which is not great stuff but it has not been shown to cause any health risk in the quantities you might encounter even installing RW on a day to day basis. Either way it dissipates pretty quickly during the install. I certainly had no worries or affects, apart from itchy forearms, when building my 10 traps for my studio, I won't hesitate to to use it when I build another half dozen panels in the new year.

* Rockwool is a trade name but there are other 'mineral wool' products from Owen Corning and at least one other manufacturer which may be easier to source in your locale.

** edit :- If I Recall Correctly

[Luke W]

Rockwool is not expensive so trying to substitute a different, unproven, material seems a bit pointless.

Definitely agree with this. There's lots of videos and blogs about making acoustic panels out of all sorts of materials and some are very bizarre indeed, but almost all of the methods I've seen look like too much of a compromise and a lot of wasted time and effort.

Adding an example to what Sam has said above, if you were to save a bit of money per panel on an alternative material for the inside of the panel, you'll probably spend it on extra support framing or mesh to keep it in shape!

[Watchmaker]

Both fiberglass and rockwool are layers of melted material that are turned into little fibers and formed into masses of product that can be easily shaped by the end user. The actual process for doing this is fascinating and I've been lucky enough to see it first hand when auditing a company that made the machines used to make such things.

Aside from the fact that fibreglass is made from sand (mostly) and mineral wool is made from igneous rock (volcanic), they are both essentially silicates of varying compositions and these types of things work by presenting frictional losses to pressure variations. The characteristic which gives glass a more harmul aspect is that the way the fibers cool during the manufacturing process creates a barbed terminus, whereas rockwool is tubular at the ends - or so I've been lead to believe.

The effectiveness of any material is due partly to density, and partly to the internal structure formed during the manufacting process and relies on forcing the molecules disturbed by changes in the pressure gradient to navigate an indrect path which results in frictional losses to attentuate sound. (layman's interpretation).

Polyesters are both less dense and have a more open structure resulting in lower frictional losses. They do work pretty well at higher frequencies and are good at damping down flutter echoes and the like.

I have a combination of all of the above used in various combinations to control the ambience of my room for various purposes.

[CS70]

OTOH, wot ee sez, sorry...

Sam, I don't have the possibility of finding the references right now but insofar I know open cell polyester is a better material than glass wool in terms of audio absorption, and it's being more and more adopted to that effect by people treating rooms professionally as a substitue for the classic rockwool etc. I was surprised myself when I learned that, but the tests (and the physical descriptions) were pretty clear.

Will try and find something when I can, it's been a while since I read about the subject. I may, of course, misremember completely due to too much cake.

[Sam Spoons]

[DanDan]

Polyester has become more and more available and affordable over recent years. Not so much in America or the UK oddly. Trump and MiniMe pact? There are many EU manufacturers, but Oh oh. Autex.co.uk
B&Q have the EcoWool. Recycling plastic bottles seems like a nice twist.
The absorption characteristics seem very similar to other fibres, better than some. This source seems to be great value. This batt is rigid enough to be hung from the ceiling without danger of sagging. It is certified for fire. Needs no fabric covering. Done. https://www.don-audio.com/Caruso-B100-B ... er-Isobond

[Drew Stephenson]

Hmm. So you could gwt a dozen for roughly £300. With no additional covering needed that puts them in a similar price to homemade rockwool + cara options.
That's going to appeal to a lot of people. Wonder how it compares to a rockwool block of the same size?

[Sam Spoons]

Density is about 40kg/m3 or ⅔ rds of RW3...

[Jorge]

https://www.bobgolds.com/AbsorptionCoefficients.htm

Compared with 4" thick Roxul Safe 72 kg/m3 or Owens Corning 703 48 kg/m3, the 4" Caruso polyester block has much less absorption of sound below 125 Hz. Same for the 4" Autex polyester in the Bob Golds' table.

If bass trapping is not important in your space and you get the fireproof version, the polyester would seem have the advantage of being a lot less itchy to work with than the rockwool or fiberglass.

[Drew Stephenson]

Thanks Jorge, useful info.

[dfira]

So my polyester boards arrived, and seem about on par with what is being commented here.

If i stack about 4 of them (measuring 36mm in depth) in front of my girlfriends face as she talks, you can hear a reasonable amount of bass extension less than 4 and honestly it sounds like it might do more harm than good.

Tbh i never tried the speaking test back when I had rockwool panels, but pushing the boundaries of my memory, and acceptable comparisons, I would say they're not quite as good as a panel of rockwool for the same size, but now I'm worried about catching lung cancer from rockwool!!

If i buy some rockwool, what is the best fabric specifically, to cover them in?

[Sam Spoons]

All the science points to the risk of catching lung cancer as a consequence of using Rockwool is vanishingly small, and who's to say polyester is any less dangerous?

If you are really worried doping the panels with a dilute PVA adhesive solution will help secure the fibres and I believe Camia acoustic fabrics are still able to contain any remaining fibres despite being fairly acoustically transparent.

Others have, I believe, covered the RW in clingfilm before covering in acoustic fabric with some success.

WRT your 'girlfriend speaking' experiment I'd expect a small reduction in HF but no affect on low frequencies from a 36mm thick low density panel. You need much more mass and 'acoustic impedance' (i.e. the slowing of air movement as it passes through the panel).

[DanDan]

On a quick look Autex Ultrafirm 50mm has an Alpha of 0.26 in the 125Hz Octave band. This is the same as some of the top performing Rock fibre products. Polyester is commonly used in clothing, bedding. I am sure there is plenty of evidence proving it's safety regarding health and fire behaviour.

[Sam Spoons]

Polyester is commonly used in clothing, bedding. I am sure there is plenty of evidence proving it's safety regarding health and fire behaviour.

A good point, having said that the evidence for the safety of RW is also well documented.

[vetko10071979]

An acquaintance of mine had these panels, he mixes and sometimes does vocals, and he says he has improved the sound, especially in the high and medium frequencies.

[Sam Spoons]

Good to hear some nearly first hand experience. TBH we've maybe been too analytical and forgotten that nearly anything vaguely similar will work, aren't we always suggesting a couple of cheap duvets (which are almost always filled with polyester)... Just that some things work better than others.