Spinorama! (also known as CTA/CEA 2034 but that sounds dull, apparently)

[Finn]

Hello everybody, good to see that I am not the only one that is confused by the 2034-A.

I have more questions, to what is discussed. If I understand correctly for Early Reflection, first calculate the energy average for all bounces than calculate the normal average of the in-between values?

Is it the same procedure for the Listening Window, Horizontal Reflections, Vertical Reflections?

For the Sound Power and Estimated In Room Response single measurement are supposed to be converted to Pascal before calculating the weighted energy average and than converted back to dB SPL. Is that the same for all calculations or just the Sound Power and Estimated In Room Response?

 

[NTK]

Hello everybody, good to see that I am not the only one that is confused by the 2034-A.

I have more questions, to what is discussed. If I understand correctly for Early Reflection, first calculate the energy average for all bounces than calculate the normal average of the in-between values?

Is it the same procedure for the Listening Window, Horizontal Reflections, Vertical Reflections?

For the Sound Power and Estimated In Room Response single measurement are supposed to be converted to Pascal before calculating the weighted energy average and than converted back to dB SPL. Is that the same for all calculations or just the Sound Power and Estimated In Room Response?

Here is what the standard says on how they are calculated. The method of averaging is power average, which means RMS of the pressure magnitudes (or for sound power, the pressure magnitude weighted by the radiating area corresponding to the measurement point, see annex C).


Note that a new (minor) revision of ANSI/CTA-2034 (revision B) was released in Aug 2024.

ANSI/CTA-2034-B

This standard describes how to determine the frequency response, directivity, and maximum output capability of a residential loudspeaker. It is intended to determine the audio performance of a loudspeaker, not the loudspeaker's ability to survive a given input signal. This standard applies only...

shop.cta.tech

 

[Dave Zan]

Note that a new (minor) revision of ANSI/CTA-2034 (revision B) was released in Aug 2024.

ANSI/CTA-2034-B

This standard describes how to determine the frequency response, directivity, and maximum output capability of a residential loudspeaker. It is intended to determine the audio performance of a loudspeaker, not the loudspeaker's ability to survive a given input signal. This standard applies only...

shop.cta.tech

Thanks for the notification about the release of the revision, after more than 4 years I didn't even bother to check any more.
And then I see they still haven't fixed the problem that kicked off this thread in the first place, FFS!
Just to save anyone the time waste to download it.
(They require payment details to be filled out, despite the fact that it's $0.00 cost, FFS x 2)

Best wishes
David

 

[Finn]

Here is what the standard says on how they are calculated. The method of averaging is power average, which means RMS of the pressure magnitudes (or for sound power, the pressure magnitude weighted by the radiating area corresponding to the measurement point, see annex C).
View attachment 412225View attachment 412226

Note that a new (minor) revision of ANSI/CTA-2034 (revision B) was released in Aug 2024.

ANSI/CTA-2034-B

This standard describes how to determine the frequency response, directivity, and maximum output capability of a residential loudspeaker. It is intended to determine the audio performance of a loudspeaker, not the loudspeaker's ability to survive a given input signal. This standard applies only...

shop.cta.tech

yes, I have read the standard. And a few things are not explained explicitly as has been discussed in this thread or it is questionable if they comply with scientific research.

@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)

Good question! Floyd says, "Rear wall bounces: average of 180 deg, +/- 90 horizontal". Looking at my HATS Spinorarma template, I see that all 19 rear horizontal curves are used. So, i think Floyd meant average of ALL measurements from 180 +/-90.

Again, looking at our template, I see that the different directions are averaged first (energy average) and THEN averaged together as you said. Perhaps the CTA standard needs to be rewritten a bit to clarify.

I would like to know if all averages are calculated in Pa or just Sound Power and ERI?

And then it has been discussed to include all measurements from +90° to -90° for the Rear Bounce which would emphasize the rear bounce siginificantly if all single measurments where energy averaged together (19 measrurements for the read bounce vs. 23 for all other bounces). First calculating an energy average of all bounces and then average the bounces. would decrease the einfluence of rearbounce significantly.

 

[Finn]

Here is what the standard says on how they are calculated. The method of averaging is power average, which means RMS of the pressure magnitudes (or for sound power, the pressure magnitude weighted by the radiating area corresponding to the measurement point, see annex C).
View attachment 412225View attachment 412226

Note that a new (minor) revision of ANSI/CTA-2034 (revision B) was released in Aug 2024.

ANSI/CTA-2034-B

This standard describes how to determine the frequency response, directivity, and maximum output capability of a residential loudspeaker. It is intended to determine the audio performance of a loudspeaker, not the loudspeaker's ability to survive a given input signal. This standard applies only...

shop.cta.tech

Thanks for your reply. In the new version a lot of my questions have been answered more extensicvely in the Annex F:

Kind regards

Finn