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Porous Absorber Calculators Don't Agree ??
Old 6 days ago
  #1
Gear Nut
 

Porous Absorber Calculators Don't Agree ??

Hey,

I am in the process of re-working and re-treating my home studio space (as documented in this other thread: Advice Wanted: Best Option(s) for Additional Bass-Trapping).

Part of the process is re-designing most of the absorbers in the room with the obvious goal of achieving more effective results than the decade+ old panels & traps I'd quickly made when it needed to be done with very little means, budget, knowledge, etc.



As part of the design process, I am modelling porous absobers using both:

http://www.acousticmodelling.com/multi.php (the multi-layer calculator)

&

AFMG Soundflow (I downloaded the demo version).


I started with the site and then grabbed the demo a little later in the process.
I have been flipping between "Allard and Champoux" (on the site), "Miki", "Komatsu", (and the "Absorber/Bies" setting in AFMG) models to get an idea of what the predictions seem to agree on and to temper expectations in case any particular model projects massively better results than another.


Anyway, the layer options in AFMG don't perfectly match the GFR numbers I've been using with the website, but the overall better or worse results seemed to mostly line up with what I would expect with either.


That said, I finally had the impulse to attempt to match the two calculators to see if they agree with each-other.. So I set them both to "Miki" (which appears to be the most agreed upon model they both share.. they do both also have Komatsu), and then matched as many settings between the two (including AFMG's number for "mineral fibre") as I could.



Despite my efforts, there is still a notable discrepancy between the two calculators.

Would you guess that something under the hood is simply using different processes (despite being set to the same model), or is there something else I might not have thought to match?

I can honestly get the graphs between the two to match more closely if I choose Absorber/Bies/Miki in AFMG but choose Komatsu on the website.



Would both calculators be considered at least somewhat trustworthy? Would one be far more accurate than the other?


I know that real-world results will likely differ in their effectiveness or specifics, but going into a build with at least some idea of whether 1 of 2 (or more) constructions might perform better / worse in a broad register (like "below vs above 100Hz for example) could still help guide me to some degree.
Thanks.

Last edited by stringsibanez; 6 days ago at 08:13 AM..
Old 5 days ago
  #2
Old 5 days ago
  #3
Lives for gear
 
Brian M. Boykin's Avatar
When I was using the calculators to design my room I used them only to help me decide where the point of diminishing returns was. Because of physical space and money constraints you have to devise a plan that gets you as close as possible to the room you desire. I follow the general guidelines that all the pro’s seem to agree on. For a small room with a small volume, lots of broadband as thick is possible, especially in first reflections. The back wall needs to be covered as much as possible. Corner traps as deep as possible. A cloud is a must. I’ve been building since August this year. I put up the cloud yesterday which completes the minimum I set out to do. The room sounds amazing, but as we know, REW can have a different opinion on accuracy. Decay times are on the dry side. I have some peaks and nulls to be expected. The swing is about +- 10dB with some low and high end roll off. I have more room for broadband which I intend to do and then I’ll move into tuned traps. The room was usable a couple incarnations ago and practice mixes I was doing were already translating well so now I feel like I’m in the bonus.

Short of the long is, keep studying and using the calculators to give you perspective of absorption and a general pathway to success, but your just gonna have to bite the bullet at some point and go or you’ll never start. I knew I would be moving into my new room in January this year and I read and studied till August.
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