- Oct 17, 2018
Sorry Guys, I haven't been keeping up! I don't have time to read through all of the above, can someone summarize any still unresolved issues? I'll try to clarify if I can. I also have a HATS file that does the Spin calculation, so I can look at that to get another reference.
@twelti Thank you so much for taking the time out to respond!
I'll summarize the two questions I have about the Early Reflections curve. As a recap for everyone, the ER curve is defined in CTA-2034A as an average of the following curves:
Floor Bounce: -20v, -30v, -40v
Ceiling Bounce: +40v, +50v, +60v
Front Wall: 0, ±10, ±20, ±30
Side Wall: ±40, ±50, ±60, ±70, ±80
Rear Wall: 180, ±90
So my questions are:
1) Does the rear wall portion only include the 3 curves listed above, or is it every curve from ±90 to 180 degrees (19 curves)?
The original 2002 Devantier paper specifically says the 'Rear' portion of the calculation includes 19 measurements. The CTA-2034A document is unclear as to whether to use 3 curves or 19. Toole's book implies 3, and @amirm confirmed above the Klippel software calculates it only using 3 curves as well.
2) Is the ER curve computed as a single average of all the above angles, or do you first average each 'section' of the curve and perform an average of all five results? The latter gives a bit heavier weighting to the vertical portions in the final curve.
The Devantier paper makes it clear the curve is an average of averages, but the CTA-2034A is more ambivalent. At least one popular speaker design tool (VituixCAD) calculates it as a single average of the 26 listed angles, which is also how others and I originally interpreted the standard.
Though there usually isn't that much of a difference regardless of how you calculate,or some speakers the ER and ERDI curves can change a fair bit depending on how you calculate, especially around crossover.
(Made a few edits for clarity)