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Sound absorption material... should I buy this stack of Rockwool ProRox SL960?

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  • Sound absorption material... should I buy this stack of Rockwool ProRox SL960?

    I can likely pick this up for $75 for a total of (20) 2x24x48 panels.

    Is this product a suitable substitution for applications that could otherwise use Owen Corning 703 (which seems to be mentioned more often in Google searches)?

    I tried doing some research but it gets muddy fast and I know I've read some things that simply aren't true so I don't have much faith in other info I'm finding.

    I'd like to make some room absorption panels and I have a large multi sub dream project that I'd like to get to some day. Regarding price, my research indicates that some OC and Rockwool products are very similar in performance and a big deciding factor on which to use is based on what's available locally in order to avoid considerable shipping charges.

  • #2
    Sorry for the double post. As has been discussed elsewhere, the the VB software seems to only be good for reading the forum with Android phones these days. I'd literally resorted to copying and pasting all of my text and pics to an email, sent it to my self and then got on my laptop to copy and pate it again from my email only to discover it had actually posted twice (both times w/o pictures of course).

    Here's the pics...
    Attached Files


    • billfitzmaurice
      billfitzmaurice commented
      Editing a comment
      As you said they're pretty equivalent, I'd use whichever is less expensive.

      Your double post situation is common. When making a comment like this one after I post it I typically get the 'working' spinning circle for at least a minute. Sometimes if I click on refresh the post will show up, but more often than not I have to close the forum link and come back later.

  • #3
    I have it on the walls and ceiling in my listening area. It's great. Use in my speakers also, with no negative comments at past speaker events.


    • Wolf
      Wolf commented
      Editing a comment
      Nice to see you around, Tim!

  • #4
    Thanks for the replies guys. I spent a couple of hours doing a deep dig this afternoon since the front page indicated that there weren't any replies even 18 hours after the first reply (still the case currently on my Android phone as well as my laptop).

    I'll provide some screenshots as well as links to where I found them. I learned more than I wanted/needed to. I also noticed that Google seemed to be pushing a lot more commercial sites than I'm used to. Maybe it's just this topic or maybe it's an indication of changes that have been made on their end. I really had to tweak some searches to force things in a useful direction. The info was obviously out there.

    Some general stuff I learned:
    The effectiveness of sound panels can be somewhat inferred by the density. Densities of 60-50kg/sq meter are the sweet spot and what you'll find in products sold specifically for acoustic applications but densities of 100kg/sq are common w/o much degradation in performance. As in my case, some products advertised with more of an emphasis on thermal insulation work great for acoustic applications as well. There is no obviously superior product or manufacturer and researching local availability for the cheapest option is warranted as shipping can add significant cost. If one looks at what frequencies are the priority to be controlled then density becomes a factor as more dense materials (think 90kg/m3 and above) are better below 1kHz but less effective above. I don't have enough personal experience in this area but when one compares the 2" 125Hz specs of Comfort 80 (.43) vs) OC 703 (.17) the choice seems pretty obvious when you realize how little you give up on the top end with the Comfort 80.

    In researching "ProRox SL 960" I learned that it was formally known as RW5 and has a density of 100kg/sq. I couldn't find any acoustic absorption data for SL 960 but I did for RW5, unfortunately I couldn't find any acoustic data for RW5 in a 2"/51mm thickness.

    Pricewise, expect to pay $1.50-$2.00/sqft for most options in a 2" thicknesses at internet retail. I'm sure shipping would be expensive but I didn't look into that. The 160 sqft I picked up worked out to .47/sqft and was the deciding factor for my purchase.

    I'll try to make a quick table comparing some common options so that others can hopefully see how a given product compares. All numbers are for on wall applications:

    Info for Rockwool ProRox line, I read somewhere that the SL 930 specs most resemble those designed for acoustic applications

    Information for Rockwool Rockboard 40 and 60

    Info for Rockwool Comfort 80

    I found tons of good info regarding the coefficients of different products here:

    I also found some interesting stuff here:

    Note how relatively more dense materials are more effective at lower frequencies but lose the advantage (and then some starting around 1,000 Hz. Also, be careful with the info in table 2. The RW3 and RW5 info seems to be taken directly from the bobgolds link above but in that link the RW5 is stated as being 30mm thick and the RW3 is listed as being 51mm thick. Also, per the bobglods link the 200Hz columns should be the more standard 125. With this you'll see that the 128kg/m3 Comfort 80 has a coeffeciemt of .43 at 125Hz.



    • billfitzmaurice
      billfitzmaurice commented
      Editing a comment
      Denser is better in the lows, but denser can become reflective of shorter wavelengths, explaining why it's not necessarily as good in the highs. What we're most concerned with is absorption where the box dimensions are more than a half wavelength, so with speakers denser may not be ideal. But if the 'box' is your listening room it probably is.

  • #5
    Looks like you went down an informative rabbit hole on this one. To add to the info you’ve compiled above I’ll add my 2 cents.

    Frequency dependent attenuation: As you look at the various attenuation performance tables you’ll note a general trend that thicker material is more effective than thinner material at low frequencies. Part of this is due to the longitudinal wave particle velocity, think of the cyclic motion of individual air molecules that experience compression and rarefaction. In a sound wave particle velocity and pressure are 90 degrees out of phase, at the wall with no particle velocity the pressure is greatest, conversely the particle velocity is greatest 1/4 wavelength from the wall. Acoustic absorption materials offer the greatest absorption when particle velocity is high.

    Following this to the logical conclusion you want absorptive material sufficiently far from a hard boundary for high particle velocity for the frequency of concern. For absorption panels placed directly on a wall higher frequencies are preferentially absorbed (1000 Hz is 34 cm wavelength, or 3.4” 1/4 wavelength where particle velocity is at maximum). Easy enough for standard in-wall insulation material.

    Typically you will also want lower frequency absorption. You can spend a ton of money and build up very thick absorption panels, or you can space your standard panels from the wall in the path of first reflections to flatten frequency dependent absorption. (Ignoring corner loaded bass traps and resonant absorbers for now)

    Spacing panels is what I’ve done in my family room. I hung panels of rockwool at the ceiling first reflections. I also experimented with bringing the speakers into the room about 30” and hanging panels behind them - worked great acoustically but did not work well for day-to-day living with my rooms layout.
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