Cheap fabric for acoustic panels

[boing]

I’m building acoustic panels (Rockwool safe-n-sound in MDF frames) to be used as broadband absorbers and as bass traps straddling room corners. Common recommendations for fabric on the cheap are burlap and muslin.

Appearance counts. Burlap is a little too rough looking and muslin is usually plain or natural in color.

As for choosing an alternative material, I know about the blow test to see if air passes easily though. That doesn’t work online, or at a local store in the time of pandemic and masks. I fingered some muslin at Joann and it seemed like pretty closely woven stuff. I guess there are varieties, but I came away without any sense of what would work and what wouldn’t. Obviously anything vinyl or with a backing layer is out. Anything t-shirt like is OK?

I’ve seen cotton duck/canvas suggested in a few places. That seems “heavy” to me, but what do I know.

 

[Crater]

I built some 'bass' traps a year or two ago, I used dyed burlap from Hobby Lobby but I also put a layer of 1" thick polyester quilt batting between the rockwool and the outer fabric.

The quick & dirty test for acoustic fabric is to see if you can breathe through it, according to some random YouTube video.

 

[silky smoove]

muslin is usually plain or natural in color.

It's available in all sorts of colors, or at least it was at fabric stores near me before I opted for commercial products rather than making my own. The gold standard for acoustic treatment fabric is Guildford of Maine. Crosspoint is another excellent company. Acoustical Solutions is a good source for what's available: Acoustic Fabrics | Acoustical Solutions

 

[seamonkey]

I don't believe blowing through fabric is a valid test to see if it transparently transmits sound. Sound goes clean through plastic wrap no problem.

 

[silky smoove]

I don't believe blowing through fabric is a valid test to see if it transparently transmits sound. Sound goes clean through plastic wrap no problem.

It's a commonly cited way to test air permissivity which is a useful spec to understand for acoustic treatments, but it does lack a degree of accuracy. I always just stick with established types of fabric such as Guilfords of Maine, Crosspoint, muslin and burlap. Anything outside of that is a guessing game in terms of real world performance.

 

[boing]

Thanks for the responses. In the grand scheme of things the cost difference between cheap DIY fabric and the commercial product isn’t really that much, but relative to the cost of the other materials in the project, it becomes more of a pain point.

As long as I’m in DIY mode, I ordered muslin and rit dye. If it proves to be a mistake, I can always re-cover the panels and call it a lesson learned.

 

[N. Kentucky Bass]

I’m building acoustic panels (Rockwool safe-n-sound in MDF frames) to be used as broadband absorbers and as bass traps straddling room corners. Common recommendations for fabric on the cheap are burlap and muslin.

Appearance counts. Burlap is a little too rough looking and muslin is usually plain or natural in color.

As for choosing an alternative material, I know about the blow test to see if air passes easily though. That doesn’t work online, or at a local store in the time of pandemic and masks. I fingered some muslin at Joann and it seemed like pretty closely woven stuff. I guess there are varieties, but I came away without any sense of what would work and what wouldn’t. Obviously anything vinyl or with a backing layer is out. Anything t-shirt like is OK?

I’ve seen cotton duck/canvas suggested in a few places. That seems “heavy” to me, but what do I know.

Use whatever you like. I ordered the color that best matched my home studio. Material is felt. Applied with glue to sides of the frames. It's worked well for a few years.

 

[silky smoove]

Use whatever you like.

Unless performance is a concern, in which case you either stick with known fabrics that perform well or you conduct tests with actual measurements to see how things actually perform.

 

[N. Kentucky Bass]

Unless performance is a concern, in which case you either stick with known fabrics that perform well or you conduct tests with actual measurements to see how things actually perform.

If you're a professional, OK. I bet the majority of us are amateurs -- "enthusiasts" would be the word. Our rooms serve multiple uses. My recording studio is also my video production studio, and by the way, is my home office where I actually do creative work to buy the dog food. I need a pleasant space to create. So the color design of my panels was just as important as sonic benefits. I got both. The room sounds like a studio and produces results to my ears that are way more than adequate for an enthusiast. I repeat my advice to the OP: use whatever you like!

 

[silky smoove]

With the available colors in known quantity, high performing fabrics available there’s simply no reason to compromise.

 

[FerK]

Instead of starting a new thread I hope it's OK to reactivate this discussion a little with my question.

I have a dedicated practice room for my trio. We play with a combination of live sound and IEM (drummer and I both use IEMs, the guitar player doesn't). The room is some 15' x 20'. Floor is carpet, 2 of the walls are drywall/MDF fully covered in carpet, the other 2 walls are 80%+ covered on thin acoustic foam (one of them is drywall/MDF, the other one is wood+glass). The ceiling is exposed MDF.

These are the wood/glass walls. Some of the glass is already covered by a thin rubber carpet (the pictures are from moving-in day, some months ago). Dunno who did that, before I started renting the place, but at least the glass doesn't resonate at all.

I plan to finish this room soon (as I said, just about all of the walls are already covered with foam, the pics are all old). Right now these wood/glass walls that you can see above are covered with foam only up to the first 7'. The top "windows" are still exposed. Although it's a small % of the overall surface, and it seems to have little acoustic effect, it looks hideous.

My plan is to cover all of the exposed surfaces with fabric. That means the entire ceiling, and the last 2.5' of this odd window-wall. And here comes the question for the people with knowledge about acoustics:

Does it make technical sense to also cover the back wall, which is covered in carpet, ceiling-to-floor with a nice-looking curtain? How about the side walls, which already have acoustic foam?

It would kill two birds with one stone: it would make the place look a bit better, and it might provide just a tad more acoustic treatment (even if it's just 2% better), for the live sound.

What does the collective wisdom of TB have to say?

 

[silky smoove]

My plan is to cover all of the exposed surfaces with fabric.

Just fabric, or fabric encasing some sort of an absorber? If the former, don’t bother unless it’s purely for aesthetic reasons. If the latter, please provide details.

 

[FerK]

Just fabric, or fabric encasing some sort of an absorber? If the former, don’t bother unless it’s purely for aesthetic reasons.

Thank you, Smoove. I just realized how poorly my question was formulated. Because I hear no significant issue in the small exposed surfaces (even considering it’s glass), the fabric would be purely for aesthetic reasons. It’s only supposed to cover some 2 ft high, along ¾ of the length of one wall (some 12 feet or so). Perhaps fresher pictures would help. I’ll do that later in the week.

My question was about the rest of the walls, which already have a little of treatment via the foam or carpet. Would it be detrimental to hang a light fabric in front of them? In other words, would the fabric be reflective enough to make the foam behind it useless?

 

[silky smoove]

Would it be detrimental to hang a light fabric in front of them? In other words, would the fabric be reflective enough to make the foam behind it useless?

Fabric that’s suitable for acoustic treatment should pass most frequencies without any absorption. If you’re using a heavier fabric you may see some reduction of reflections that increase as frequencies increase. This can lead to the classic foam or egg crates problem of reducing mid and high frequency reflections while leaving low frequencies untouched which then leads to a boxy sound in the room that feels like it’s overemphasizing lows and mids but really it’s just lacking highs.

What type of fabric are you considering?

 

[FerK]

Haven’t started looking yet. I assume that the lightest possible fabric would be the way to go? I can easily procure 3.8lb/ft2 (160g/m2) flame-retardant cotton, which comes in 3m-wide rolls. Around here it’s called Molton, and it’s commonly used for stage-masking.

 

[silky smoove]

Haven’t started looking yet. I assume that the lightest possible fabric would be the way to go? I can easily procure 3.8lb/ft2 (160g/m2) flame-retardant cotton, which comes in 3m-wide rolls. Around here it’s called Molton, and it’s commonly used for stage-masking.

The weight is one aspect to consider but more importantly is the air permissivity spec. Think about burlap which is quite thick but also very porous. Despite its heavy weight burlap is perfectly acceptable in many acoustic applications. Muslin fabric is the usual go-to on the cheaper end of the spectrum.