Why RTings measured it differently: AKG open-ear bad 1k-3k distortions

[vrships]

Amir measured buncha AKG popular open ear headphones like K701, 702 and 7xx and all of them show unacceptably bad distortions peaks in the 1k-3khz range:

AKG K701 Headphone Reviews (China and Austrian Made)

This is a review and detailed measurements of two versions of AKG K701 headphones: one made in Austria and one in China. They are on kind loan from a member and cost US $249. Let's start with the China version. It is lightweight and doesn't impart feeling of a premium product. The large cups...

www.audiosciencereview.com

The numbers may be different but the existence is confirmed in other reviewer's results, too.
I am just surprised how these "reference" AKG phones that are liked by so many (including me), are actually quite bad in its cleanliness and fidelity in the most sensitive frequency range.

But RTINGs has quite different numbers from the measurement in Harmonic Distortions.(It's weighted instead of the basic "Total")

Headphones v1.5 - Graph Tool

www.rtings.com

It looked much better than the results posted here, the 2 peaks are well below 0.3% at 100dB SPL.

And because of this, it actually outperformed the few models Sennheiser HD660s. While the THD results from Amir shows HD660s is ages better than AKG from 200Hz and above.

How could understand the big difference here in distortion? Was something done very differently by different reviewers? How should I make judgements given these opposite results?

 

[ugur38]

Amir is measuring Total Harmonic Distortion (THD) and Rtings is measuring Weighted Harmonic Distortion (WHD).

Rtings says this: This test differs from Total Harmonic Distortion (THD) by applying a perceptual filter to each individual harmonic before calculating the total.

Actually I don't understand Rtings' distortion measurements and Amir's distortion measurements are much more readable to me.

 

[solderdude]

Rtings found that distortion in the lows isn't as audible as in the mids.
As they wanted a single number (in order to make a rating of sound quality) they needed to produce a number that related to perceived distortion.
Later on Rtings created different ratings for different use cases.

The problem is... it should be measured at different SPL which not many do. With some headphones the distortion (compression) rises quickly but can sound fine at background listening levels.

 

[vrships]

Amir is measuring Total Harmonic Distortion (THD) and Rtings is measuring Weighted Harmonic Distortion (WHD).

Rtings says this: This test differs from Total Harmonic Distortion (THD) by applying a perceptual filter to each individual harmonic before calculating the total.

Actually I don't understand Rtings' distortion measurements and Amir's distortion measurements are much more readable to me.

THD is basically sum of powers of all harmonics of 2x, 3x, 4x, ... in the spectrum.

WHD as I understand it requires a weight to each harmonics, but they need to be normalized so they can be directly comparable to non-weighted THD otherwise the final THD percentage would be make no sense if the weights are too large or small overall.

For example for 1kHz output, THD= Power(2kHz)+Power(3kHz)+Power(4kHz)+...
WHD maybe: Power(2kHz)*0.5+Power(3kHz)*0.9+Power(4kHz)*1.2+.... But now sure how they choose what these coefficients to use and it may be the cause that WHD of certain input frequencies are muted.

 

[vrships]

Rtings found that distortion in the lows isn't as audible as in the mids.
As they wanted a single number (in order to make a rating of sound quality) they needed to produce a number that related to perceived distortion.
Later on Rtings created different ratings for different use cases.

The problem is... it should be measured at different SPL which not many do. With some headphones the distortion (compression) rises quickly but can sound fine at background listening levels.

Current reviews of WHD are given for 90dB and 100dBSPL.

Even given the calculation difference, their results still look too much cleaner than measurements of other sources. The notorious distortion peaks for AKGs are all gone, making them look better than Sennheiser models.

I would definitely avoid all AKG phones if those measurements with spikes are real from various sources. Those are just worse than any headphones of any kinds from renowned brands in modern era.

But now looking at RTings results I don't know what to choose..

 

[okok]

rtings distortion figures different from many other sources, untrustable in my sense

 

[solderdude]

Current reviews of WHD are given for 90dB and 100dBSPL.

Even given the calculation difference, their results still look too much cleaner than measurements of other sources. The notorious distortion peaks for AKGs are all gone, making them look better than Sennheiser models.

I would definitely avoid all AKG phones if those measurements with spikes are real from various sources. Those are just worse than any headphones of any kinds from renowned brands in modern era.

But now looking at RTings results I don't know what to choose..

One will never have 2kHz at 104dB or 114dB SPL with music so above a few hundred Hz one does not need to measure it BUT, and this is the point, it can show driver issues.
Hardly ever I hear AKG owners complain about distortion. It isn't as audible as some believe.

 

[vrships]

One will never have 2kHz at 104dB or 114dB SPL with music so above a few hundred Hz one does not need to measure it BUT, and this is the point, it can show driver issues.
Hardly ever I hear AKG owners complain about distortion. It isn't as audible as some believe.

Partly because listeners do not really know what the sounds are supposed to be. If you add 2x and 3x distortion to an otherwise pure sinusoidal 2kHz wave, you will notice it is rougher and less comfortable to hear. But in music one never knows if some tones is intended to be smooth or rough. To verify this you can have AKG K702 and HD660s side by side, play the same pure sinusoidal 2kHz wave and hear if AKG is indeed rougher? But of course you have to level the volume and prepare a lot of other things to make it accurate, which makes little sense if you don't question the measurements from professional acoustic instruments.

 

[solderdude]

I never listen to pure tones for pleasure. Only music is relevant IRL. And for me also not at high levels.
I do not have AKG headphones myself though but measured and heard quite a few.

 

[Aperiodic]

I never listen to pure tones for pleasure. Only music is relevant IRL. And for me also not at high levels.

This is important. It seems to me that the ear (my ear anyway) perceives volume differently through headphones than through speakers. Maybe due to the lower distortion levels that (good) headphones can deliver? I don't know for sure but I do know that 114dB is a torture test for headphones and ears- and that headphones are replaceable. So I set the volume when I begin listening at a satisfying but reasonable level and try to avoid turning up. If you have to turn up more as you get further into a long listening session, there may be an issue.

 

[solderdude]

114dB continuous at 30Hz or so is a torture test for headphones.
For the ears, a 114dB peak in music not so much to the ears. Is easily reached when one plays a song at impressively loud levels.
I would not recommend to listen to 1kHz tone at 1kHz or so.

 

[Lunafag]

Weighting bass distortion is baffling to me. Sure, comparing bass vs bass with harmonics added is probably not that audible. But that's not how it works in headphones. Play a voice sample and a strong subbass tone at the same time. A headphone with high bass distortion will make the voice warble but a headphone with low bass distortion won't. And for bass distortion even measuring at 114dB doesn't always reveal audible issues(see Amir's GL2000 review). Maybe the solution is distortion measurements that go beyond harmonic distortion.

 

[solderdude]

Yes, you can do IM measurements or multitone but it will look messy.
When using a 100Hz + 1kHz tone you will see harmonics + 900Hz and 1.1kHz and the latter two will be SPL dependent.
The current HD measurements at various SPL and some knowledge to correctly interpret the plots also will reveal if a headphone has low IM distortion.