You are here

Log in or register to post comments
U6astik's picture
Last seen: 9 years 1 month ago
Joined: Sep 7 2012 - 4:16am
Explanations on BobGolds room modes' online calculator

I have to say that I was wrong when saying in my previous topic that the BobGolds online calculator is not helpful.

However, I would be grateful if somebody could explain me how to interpret the results.

I am mainly interested in reverberation time due to RT60:

RT60 (IEC/AEC N 12-A standard): 264 ms

  • ±50ms from 200Hz to 3.5kHz = 214 to 314ms
  • ±100ms above 3.5kHz = 164 to 364ms
  • <+300ms at 63hz = 564ms
  • 300<RT60<600ms

RT60 (ITU/EBU Control Room Recommended): 233 ms

  • ±50ms from 200Hz to 4kHz = 183 to 283ms
  • <+300ms at 63hz = 533ms
  • 200<RT60<400ms

Absorbtion to achieve ITU RT60: 608 sabins
Volume: 81 m^3

RT60 = 0.1611 V/Sa , where V - room volume, Sa - amount of sabins or room surface area x absorption coeff. If V=81, Sa=608; RT must be 0.0214 or 21ms. Comparing to 264 and 233, difference is too significant. What's that? Is there a mistake?

Why there are two different RT60s? What means t1<RT60<t2?

And also about the last 11 lines (apart from the last one):

(sabins - front wall - carpet) / Left+Right+Rear wall: 34 %
(sabins - front wall) / Left+Right+Rear wall: 85 %

What is this percentage about? Amount of sabins to be placed on walls or on floor and ceiling?

Schroeder frequency: 100hz

What's that?

Frequency Regions:

  •  No modal boost: 1hz to 27hz
  •  Room Modes dominate: 27hz to 100hz
  •  Diffraction and Diffusion dominate: 100hz to 400hz
  •  Specular reflections and ray accoustics prevail: 400hz to 20000hz

What can be deduced from that?

Count (27.8-179hz) : Axials=13, Tangentials=54, Obliques=72
Count (27.8-100hz) : Axials=6, Tangentials=9, Obliques=2

Does it tell anything important? To my mind, the amount of different types of modes is not so vital..


  • X