Home Mix Room Overhaul - DIY Panel Build - w/ REW Charts/3D Sketchup

[endorka]

Thin plastic is not wrong if what it does acoustically is what you are wanting.

Starlight is correct - that's a big if though

If you are ok with the safety aspects, I can tell you some applications where I would not leave it acoustically to chance;

1) Anywhere there are potential first or second reflection points from speakers to the mix position. Bear in mind that you may move your speakers around to optimise sound once treatment is in place.

2) If I was building a "vocal booth" from gobos. Don't want these reflections in the mic.

Where I think it might be useful acoustically;

1) Building a small gobo fort behind an acoustic guitar to bring some reflections and a more balanced / less close mic'd sound to the mic. However, your gobos will have a wooden panel on one side anyway that will already serve that purpose.

2) In areas of your control room definitely not in mix position first or second reflection points.

With this in mind you could potentially build all your room treatment without coverings at first, and measure the response. Then add the plastic one panel at a time, measure again, and see if it has made things better or worse. On panels where it makes things worse, use your more expensive liner instead. Once you have the room optimised, cover with fabric and hope it doesn't change the HF response too much.

A more experienced acoustician may be able to make exact predictions about where the plastic would be useful or not, but that's beyond my confidence level I'm afraid

I think wanting a good looking and sounding result is a worthwhile goal. People often hear with their eyes, and your studio, recordings, mixes etc. will be judged harshly if they are made in a place that looks like a lashup. Even if they sound great.

The thing is, you are wanting something that sounds great and looks great. It's worth pointing out an adage a friend of mine uses: "buy cheap, buy twice". Sometimes the only way to get something correct is to spend more than you expected to. Sometimes buying something twice isn't a such big deal. Having to redo an entire room worth of panels and traps is a really big deal though. The time and labour alone is a huge cost.

Just my opinion - take your time, spend what is required, measure twice, cut once, and get the correct result first time. You and others will be enjoying the result for years to come, long after the extra $ have been forgotten.

Cheers,
Jennifer

[shybird]

Source of the post There are: polyester batting has a low GFR and will not reflect any high frequencies.

Thin plastic is not wrong if what it does acoustically is what you are wanting.

Thanks for the clarification! I did some more searching and found a thinner polyester batting at Joanns for super cheap! It's the 4oz variety (3/8 inches thick) which should be all I need. It's also 48" wide so it should work perfect on the face of the panel frames and superchunks without too much cutting.

Here is the link: https://www.joann.com/poly-fil-light-weight-4-oz.-bonded-polyester-batting-roll-48x45-yds/14195846.html

It's a 45 yard roll of the stuff for $61.46 after tax and shipping. It's actually cheaper than buying less by-the-yard.

I put some of the burlap up to a white sheet of paper to roughly mimic what it would look like with this poly bat behind, and honestly you couldn't even tell there was something behind it. It sort of just accentuates the burlap and makes it look solid rather than see-through.

That being said, I think I'm going to pull the trigger on this since it wouldn't cause any problems in the high end and it's CHEAP.

Source of the post The thing is, you are wanting something that sounds great and looks great. It's worth pointing out an adage a friend of mine uses: "buy cheap, buy twice". Sometimes the only way to get something correct is to spend more than you expected to. Sometimes buying something twice isn't a such big deal. Having to redo an entire room worth of panels and traps is a really big deal though. The time and labour alone is a huge cost.

This is great advice and definitely something I needed to hear. I don't want to make any huge mistakes along the way and I definitely want to be happy with the result by the end of all this. That being said I did find the poly bat super cheap! (as I explained above)

Also, I like the idea of going with no plastic and using the non-reflective poly bats instead...that way later on I can use your idea of adding wood slats to the front face of the panels if I do end up needing some additional high end reflections. It's a pretty small room width and length wise, especially with the fireplace jutting out into the room...so there's definitely a lot of reflection points that could've been troubling if I had gone the plastic route. So thank you for talking me out of that! I'm so glad I found that cheaper polyester batting material.

Also, I do enjoy the burlap look as long as it is flush, non-transparent, and with no creases. My rooms have a vintage/antique vibe already (old 1940's home) so the natural colors will go really well I think. Just has to be done right.

Thanks again to both of you!! You've already saved me some painstaking mistakes.
-Trevor

[shybird]

Alright, so I am having the hardest time sourcing a good burlap. Due to COVID, a lot of places are low on stock and out of the colors I'm interested in. So, I'm looking into other fabric types. I'm going to link below to a couple things from Joanns and if anyone has the time please let me know what you think! Probably going to do another visit to their store this weekend.

Posh Lining Fabric / 100% Polyester / $5.99 per yard (58" width)
https://www.joann.com/posh-linings/prd32708.html#q=posh%2Blining%2Bfabric&start=1

Suiting Fabric / 100% Polyester / $7.49 per yard (57" width)
https://www.joann.com/sew-classics-suitings-many-colors/xprd728532.html

Knits Jet Set Fabric / 100% Polyester / $5.59 per yard (58" width)
https://www.joann.com/knits-jet-set-2-fabric-solids/zprd_15304991a.html#prefn1=isClearance&prefv1=true&prefn2=size&prefv2=52%22%20-%2060%22&srule=price-low-to-high&addShipToHomeConditions=false&start=1

Cheers,
Trevor

[Starlight]

Source of the post... if anyone has the time please let me know what you think! Probably going to do another visit to their store this weekend.

The first one just shows as a solid colour so that is difficult to even guess at its suitability. The other two look like possible contenders, especially the Knits Jet Set Fabric because the first customer comment mentions how stretchy it is and that will make it easier to get a neat, tight wrap over your traps.

As you cannot breathe through them online, your visiting this weekend sounds like a good idea. For virus protection I imagine the shop won't be very happy at your checking a fabric for breathability by blowing through it, so why not take a hand-held hair dryer with you? Don't forget to switch it to blow air without heating.

[shybird]

Hey Starlight, those are all great ideas! Thank you for the reply.

I've found one more online but wouldn't be able to test in person.
https://www.efavormart.com/products/10-yards-54-wide-charcoal-gray-polyester-fabric-bolt

I've also heard breathability isn't always necessary depending on what the fabric is made of? Like as long as it isn't reflective...or is that completely wrong?

I've also heard that stretchy fabric is actually harder to work with...I guess you disagree with that notion?

Cheers,
Trevor

[Starlight]

A drumhead is not elastic but it gets stretched in place. Some textiles, such as denim, have zero elasticity, and would be hard to work with. At the other extreme lycra/spandex would be so elastic I can imagine that being the sort of stretchy fabric that is harder to work with. In our last studio, my wide and I bought a cloth to create a large backdrop (for making YouTube videos) and we discovered that it was slightly elastic - as I remember, over a 3 metre (10 feet) length it maybe could stretch 15cm (6 inches) and, like a drumhead, made it easier to get a taut, flat surface.

[shybird]

Thanks again for the reply Starlight! Much appreciated.

I talked to a staff member at Joann about that “Knit Jet Set 2” that I linked to above. Apparently it is not very see through, but it is stretchy, and it doesn’t pass air on the “blow” test. She was super nice and said someone else that day came in buying fabric for acoustic panels and he went with a suede which definitely did NOT pass the air test. She said it was much heavier than the fabric I was considering and also like $17/yard.

Again, should I avoid this fabric on the air test alone or might it be ok? She said it’s very soft and has a matte finish (not shiny). Depending on the answers I get here, I’m going to take a look at it tomorrow morning. But it’s a 30 minute drive so I’d love to know if it’s worth the trip or not.

Cheers!
Trevor

[endorka]

Home Recording Studio: Build it like the pros p.207;

In order for these panels to be effective, air has to be able to pass freely through them. This means you need to have a fabric that "breathes easily." In other words, if you put the fabric tight against your face, then you should be able to breathe easily through the fabric.

Everest's MHOA says the same thing in a more detailed way, p.191.

I'd take their word for it if I were you

On a related issue, Everest also recommends insulation of about 1 lb/ft3 for low density sound absorbing applications.

Cheers!
Jennifer

[shybird]

Hey Jennifer, thanks for the reply!

So I’m curious about that polyester batting that was recommended by Starlight that I use behind the burlap if I went that route...that stuff sure doesn’t look like it would pass the air test. It’s like 3/8” thick which is the thinnest I’ve been able to find!

But Starlight mentioned it has a low GFR and therefore won’t reflect sound. Based on that, it seems the most important part is that whatever material covers the panel should either be “breathable” OR have a low GFR so it does NOT reflect sound. And it seems that a low GFR does not always mean breathability...am I interpreting this correctly?

If that’s the case, then is the “breathability” test just a general way of getting inexperienced people such as myself into the ballpark of fabrics that will work? It seems like there must be fabrics that are not breathable, but are also not reflective and therefore any of the highs that are not actually passing through the fabric are being absorbed which is what the insulation would have done if those frequencies had been able to pass through in the first place.

Sorry to hammer this home! I’m just very amazed at how challenging it has become to find a “non-transparent” and yet “breathable” fabric! It seems a bit of a paradox...


Also, I’ve seen felt has been recommended for this as well? But I tested some regular old felt I had lying around the house and that stuff is not passing the air test...but it definitely doesn’t seem reflective either! Hahaha I’m so confused.

Any further clarification before I hit the fabric stores again today would be hugely appreciate! Thank you all again for all the help.

P.S. I’d like to suggest and help make a sticky post on the forum with a list of as many usable fabric types as possible with links to examples. And an explanation that either once and all confirms the “air test” is 100% critical or not critical if the fabric is absorptive by nature (low GFR or whatever...).

Cheers!!
Trevor

[endorka]

So I’m curious about that polyester batting that was recommended by Starlight that I use behind the burlap if I went that route...that stuff sure doesn’t look like it would pass the air test. It’s like 3/8” thick which is the thinnest I’ve been able to find!

But Starlight mentioned it has a low GFR and therefore won’t reflect sound. Based on that, it seems the most important part is that whatever material covers the panel should either be “breathable” OR have a low GFR so it does NOT reflect sound. And it seems that a low GFR does not always mean breathability...am I interpreting this correctly?

From https://www.sciencedirect.com/topics/engineering/flow-resistivity#:~:text=Air%20flow%20resistance%20is%20defined,through%20porous%20materials%20%5B25%5D.

Air flow resistance is defined as the ratio of static gas pressure between both sides of material to the airflow speed. Flow resistivity is defined as the airflow resistance within unit of thickness and it reflects the air permeability through porous materials.

It seems to me that breathability and and GFR and related. Low GFR ~= high breathability. I think the polyester batting will be fine.

If that’s the case, then is the “breathability” test just a general way of getting inexperienced people such as myself into the ballpark of fabrics that will work?

Yes. It's a way of obtaining a well predicated behavior from the absorbers. If you stray from this, the behaviour will be less predictable.

Remember that these are porous absorbers. In very simple terms, the sound waves getting in to them is how they work. Impede that with less porous materials and you will change their behaviour.

It seems like there must be fabrics that are not breathable, but are also not reflective and therefore any of the highs that are not actually passing through the fabric are being absorbed which is what the insulation would have done if those frequencies had been able to pass through in the first place.

Different coverings for different acoustic purposes can be applied to the front face of these type of absorbers, but from what I've seen not usually the sides and rear. However the fabric does cover the whole insulation. What works well for the front may not work well if applied all over.

My notion of the behaviour of these absorbers is that they work in three ways. There are three things that can happen to the sound that hits them;

1) It gets reflected.
2) It passes through.
3) It experiences friction in the insulation, causing it to heat up a tiny amount. Thus the sound is converted to heat.

You can change the behaviour of these with different front coverings. Perforated metal, slats, grilles, limp membranes or what have you. It can be very useful in addressing specific acoustic challenges. Everest and others explain this in great detail. I think you are getting somewhat ahead of yourself with concerns such as this at the moment. These are tools for fine tuning; at the moment you're after a sledgehammer to deal with low frequency problems.

A good approach is to deal with low frequency challenges first, then see what mid and high range challenges remain after that.

Sorry to hammer this home! I’m just very amazed at how challenging it has become to find a “non-transparent” and yet “breathable” fabric! It seems a bit of a paradox...

All this thinking you are doing is making it over complex. Stuart suggests a darker breathable covering under a lighter top layer if you're after a light cloth finish. Starlight's approach is similar. Both will work.

Also, I’ve seen felt has been recommended for this as well? But I tested some regular old felt I had lying around the house and that stuff is not passing the air test...but it definitely doesn’t seem reflective either! Hahaha I’m so confused.

It it's not breathable, stay clear of it.

Cheers!
Jennifer

[shybird]

Source of the post It seems to me that breathability and and GFR and related. Low GFR ~= high breathability. I think the polyester batting will be fine.

Jennifer, thank you again! Your reply came right in time...I was just about to walk into Joanns. It was helpful having some insight before walking into the store. Per Starlight's recommendation, I ended up taking a small battery powered air mattress pump with me to use on the fabrics and it worked great! So funny though walking through the store and turning that thing on randomly it sounded like a vacuum cleaner and I definitely got some funny looks haha.

It seems to me that breathability and and GFR and related. Low GFR ~= high breathability. I think the polyester batting will be fine.

That's what I figured! I did check some of the batting they had there and it did pass the air test. My apologies on that...I was completely thinking of a different type of material more in the styrofoam realm. I made some assumptions I shouldn't have.

HOWEVER, I did test out various felts they had there and though they all looked the same, some passed the air test and others totally did not! I couldn't figure it out. They looked and felt nearly identical and the thicknesses weren't too far off either. Both very soft and seemingly "porous."

I guess my BIG looming question regarding fabrics and the "air test" is this:

We are trying to avoid any fabrics that would create reflections in the high end (obviously most mids and lows will pass straight through) so that we can add those back in later if necessary with slats etc...that makes total sense as it gives us more control on the acoustics as we move forward. BUT, does all fabric that fails the "air test" automatically mean it will reflect sound? If so, then obviously everything should most definitely pass the "air test" if we want to avoid all reflections. I'm just thrown off when a soft and seemingly "porous" fabric like felt can both pass and fail the test...I just can't image felt reflecting high frequencies?! Even if it doesn't let them all through into the insulation. Might it just be functioning somewhat like the insulation and just absorbing whatever high frequencies that it's not letting pass through?

I'm sorry for being so OCD about this. Stuart probably remembers this from working with me 8 years ago! I also totally understand if you need to call me out on my "thought process." I'm here to learn and just really can't understand the full extent of this fabric issue.

All that being said, I really wish they had a darker poly-bat for my darker color panels since I plan to do some lighter and some darker. The white just won't work with the darker burlap if I go that route...which is looking like the best solution for me cost wise and also looks wise. A lot of these other fabrics were very prone to collecting lint. The burlap panels I have from ATS look the same as they did 8 years ago when I hung them.

Ok over and out. Thanks for bearing with me on this.

Cheers! (drinking a beer now )
Trevor

[endorka]

I did test out various felts they had there and though they all looked the same, some passed the air test and others totally did not! I couldn't figure it out. They looked and felt nearly identical and the thicknesses weren't too far off either. Both very soft and seemingly "porous."

I'm no expert on fabrics but perhaps it has to do with the denseness of "weave"? A denser weave with smaller "holes" would make it less porous I imagine.

I guess my BIG looming question regarding fabrics and the "air test" is this:

We are trying to avoid any fabrics that would create reflections in the high end (obviously most mids and lows will pass straight through) so that we can add those back in later if necessary with slats etc...that makes total sense as it gives us more control on the acoustics as we move forward. BUT, does all fabric that fails the "air test" automatically mean it will reflect sound?

I can't say I've considered the implications of dense felt before. However, I'm happy to venture a little though experiment at the extremes of my theoretical knowledge. Sound hitting the panel face can be;

1) Absorbed via conversion to heat within the insulation
2) Reflected
3) Pass through

If the covering is non-porous and sealed then the insulation won't be doing much absorption via conversion to heat of high frequencies. Also very little will be passing through "gaps" in the absorption material, although some will be transmitted by sympathetic vibration of the panel. The higher the frequency of sound, the less gets transmitted this way.

In other words, very little in the way of high frequencies are being absorbed or passing through. So that leaves only one possibility for most of them: reflection.

Perhaps then what you are wondering about is absorption properties of the non porous felt material itself? Will that be sufficient to absorb the high frequencies while the insulation inside deals with the low? I found this information from a manufacturer of felt;

[quote]Felt is produced by pressing and matting fibers together. The performance of felt in sound absorbtion is as a result of its optimum density and spring. The absorption of sound waves is achieved by the vibration of individual fibres within the felt. The energy is dissipated by frictional heat loss. Due to its method of absorbtion, too dense felt would not allow for sufficient vibrations.[quote] - from https://www.phelpsgaskets.com/blog/mate ... 20proofing.

In other words, the manufacturer is also saying dense felt won't work either for this particular application: broadband porous absorbers.

I wouldn't call out your through process, I sincerely admire your dedication to knowledge. The answers to these questions are available in Rod Gervais book and the MHOA, and if you have a genuine interest I would suggest buying them and studying them in depth.

If your goal is the application of known principles to build something in a reasonable time, however, there are many areas more worthy of that degree of theoretical questioning than others.

If it is possible to buy porous felt you know will work, why even concern yourself with equivalent non-porous stuff that looks very unlikely to?

Cheers, and enjoy that beer
Jennifer

[shybird]

Source of the post Perhaps then what you are wondering about is absorption properties of the non porous felt material itself? Will that be sufficient to absorb the high frequencies while the insulation inside deals with the low? I found this information from a manufacturer of felt;

Yes! Essentially that's what I've been wondering. If a material does not pass the air test, yet it is soft and seemingly "absorptive" NOT "reflective" then might it be absorbing whatever little bit of high frequencies can't pass through into the insulation?

In other words, the manufacturer is also saying dense felt won't work either for this particular application: broadband porous absorbers.

That is so wild! I just can't wrap my head around a material like felt reflecting ANY frequency. But at the end of the day it just shows how little I know about the complicated world of acoustics! I had no idea a material like that could be considered reflective. Super crazy!

If it is possible to buy porous felt you know will work, why even concern yourself with equivalent non-porous stuff that looks very unlikely to?

A good point for sure! I'm reverting back to my search for a good quality burlap. I think it will look the best with the stained wood panels I'm building. All the other stuff looks too sleek and modern (and the felt just clings and shows lint like crazy)! My place has a much more vintage vibe that I want to maintain. So, thanks to all your help I've at least narrowed my focus down to one goal. Finding a nice looking burlap that isn't out of stock! (ATS acoustics has what I need but due to covid, their supplier is out of stock)

I followed that beer up with some bourbon...

Cheers
Trevor

[SoWhat]

Greetings Trevor,

Methinks after your fabric "battle," you'll be the expert on the subject. I thank you for asking all the questions, as I will be using this thread when I get to that stage of my build.

I followed that beer up with some bourbon...

I've been a Maker's Mark drinker for 30 years.

All the best,

Paul

[shybird]

Hey Paul!

I'm certainly trying to understand the fabric issue in more detail haha. Jennifer definitely has a point in just using tried and true materials. I'm just finding it hard to source things right now due to COVID, so I'm looking at all potential options. Glad it's been helpful! I will post more as I continue learning. Would love to hear Stuart's breakdown of the fabric issue too.

And that's awesome! Maker's is great. Also love Woodford and Buffalo Trace. I visited Maker's and Woodford distilleries when I was younger...I grew up in Lexington, KY so it's kind of a right of passage lol. Got to dip my own Maker's bottle in the wax! Beautiful places/drives in the fall/spring if you ever get the chance to visit.

Cheers,
Trevor