Headphone and Headset Measurement Seminar Listen Inc.

171030_HeadphoneMeasurementSeminar_Photo_Listen
Steve Temme talks about various measurement techniques using Listen Inc. hardware and software.

On a surface level, one might be tempted to think the seminar was just a long infomercial for the gear being discussed. But as the presenters progressed it became quite obvious that the driving force behind the development of the software and hardware is the significant difficulty of acoustic measurements, and the peculiarities of measuring headphones in particular. The products themselves are essentially reflections in the flesh of brilliantly imaginative and technical thinking about headphone measurement. I found it fascinating.

The core of Listen Inc.'s solutions is a sophisticated software package called SoundCheck that has three primary capabilities:

  1. Test Sequencing - An extensive library of pre-existing tests and functions that can be dragged and dropped into a test sequence. Woot! No more line-by-line programming for me.
  2. Virtual Instruments - Once connected to appropriate USB controlled hardware devices containing digital to analog and analog to digital conversion, the software is able to act as a: signal generator; multimeter; real-time analyzer; oscilloscope; and spectrum analyzer.
  3. Data Analysis - Loads and loads of stuff here, but SoundCheck can perform numerous time domain, frequency domain, and distortion analyses. It also has a variety of algorithms to perform complex measurements and speed up data acquisition times.

It's pretty obvious from the demonstrations I witnessed that this software will be able to do everything I've been doing...and much, much more. Of particular interest to me, it will be able to provide cumulative spectral decay plots (waterfall plots), something I've been yearning to do for quite a while. And it will be able to provide an array of distortion measurements including: THD+noise, THD, Rub & Buzz, Loose Particle Detection, Intermodulation Distortion, Non-coherent Distortion and Perceptual Distortion Measurement.

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Cumulative spectral decay (time/frequency; waterfall) plot from the SoundCheck software.

Steve Temme went into a great deal of detail on the non-coherent distortion measurement. Frankly, it's quite complicated and far over my head, but basically it's a dual-channel analysis that looks at the difference between the input and output of the device under test (DUT) when excited by a complex signal. In fact, you can use music to perform the test! Though, my understanding is pink noise is more commonly used. For more information go to this Listen Inc. page.

One of the big unknowns here is exactly what tests I will be adding to the current array of InnerFidelity tests. I'll be taking a lot of advice from Listen Inc. about improvements to my process, but I'd certainly be interested in your ideas.

This, of course, means once the dust settles and I've got a new measurement procedure I'm going to have to go back and remeasure a bunch of headphones. I'll probably limit it to "important" headphones, but it will be another mountain to climb. Ah well, job security I guess.

Listen Inc. also has a number of hardware products to exersize and monitor the headphone and measurement head. Potentially of interest for the InnerFidelity headphone measurement program are:

A problem I've had in the past is difficulty doing impulse response measurements with Bluetooth devices. The latency of transmission causes my tester to loose sync of the MLSS signal. This can also occur in wired mode with headphones that use DSP as that can also cause some latency.

Listen solves this by providing methods for "open loop" testing where the software basically listens for trigger tones to fine tune synchronization, and initiate acquisition and analysis. So now I will be able to add impulse response measurements for bluetooth and DSP wired headphones. And, you can store test signals on an iPhone or iPad and run measurements sequences for Lightning connected headphones.

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COMMENTS
jim in cheyenne's picture

This is great news! Yeah it's time to update the equipment.

How to bridge between the old measurements and the new? You will have better ideas than I, but I would think a half dozen or so well chosen headphones, from modest to 'all-out' with carful discussion of the differences would suffice. Of couse all of us hope than half dozen includes our favorite....

Good luck, keep up the good work!

jim in cheyenne's picture

This is great news! Yeah it's time to update the equipment.

How to bridge between the old measurements and the new? You will have better ideas than I, but I would think a half dozen or so well chosen headphones, from modest to 'all-out' with carful discussion of the differences would suffice. Of couse all of us hope than half dozen includes our favorite....

Good luck, keep up the good work!

Oops, I tried to register, but Listen wouln'd accept it
Is ther some 'company' we are supposed to use?

JMB's picture

I quite appreciate the progress in Grass design. Our ear canals and pinnae are quite variable (even between one owns left and right ones) so exactly which would be the one to choose? Also the materials used to make artificial ears/heads are quite different to our tissues (especially regarding damping and resonance behavior). So there will be an ever changing improvement for more realistic ears (upgrade for ever like we do our toys).
I still have a more basic question about how measurements at the eardrum are relevant for headphones but not for loudspeakers. I understand that IEMs don not use our outer ear and only a part of the ear canal but that does not apply to circumaural headphones which leave the function of the ear canal and at least partially the outer ear intact as would listening to loudspeaker in free air. Basically this is a question about what is the right compensation curve.

coastman25's picture

Surely, the obvious candidates for revaluation using the new testing methods and equipment would be your current wall of fame headphones. However before going there perhaps look at models were the test results did not match your listening experience and see if that is still the case with the Listen Inc system. Then some visa a versa ie re-test some you are familiar with I know for sure your listening experience matches your current test results.

GTABC's picture

That would make the most sense to start.

I'm really interested in the subjectively poor headphones with good measurements(under the old methodology) along with subjectively good headphones with bad measurements (under the old methodology).

Gosh it would be nice if new measurement equipment/ techniques changed measurements in such a way that they would more often be aligned with subjective impressions.

I've often heard that headphones that measure poorly rarely sound good but that there are many examples of headphones that measure well but sound awful.

100VoltTube's picture

I would also love to see some more measurements of those types of headphones. In addition, it might also be interesting to see more measurements of headphones where the measurements tell one story about the sound signature and the listening tells a different one. For example, the beyer T70

100VoltTube's picture

It might be interesting to look at Fourier transforms of the headphones' output as a function of input frequency. A sort of 3D Fourier transform, if you will (or just a couple of normal Fourier plots). It might also be interesting to see how the distortion components change during the decay of a tone. Like a CSD plot, but the decay of a single sine wave.

Journeyman's picture

I do hope they help you out. It's great advertising in the long run given the fact you are a reference for many headphone enthusiasts.
I also think the headphone community would be very grateful.
Tyll I do hope you measure some Beyerdynamic Headphones models again. :-D I know you don't really like them but the DT880 is a reference for many people.

MRC01's picture

What a treat. It's great to see this level of research which will improve SOTA for everyone. Thanks for sharing the experience. As for what kind of new measurements to include, I suggest CSD plots.

zobel's picture

I imagine that the new distortion / noise measurements may be the biggest improvement in conveying perceived sound quality. Those, along with the waterfall plot, and improved SPL/freq. graph, there has to be be a much improved set of measurements that will go much further in describing the sonic features of all HP measured.

Thanks for keeping your tests as relevant as possible Tyll. I like your idea of covering the 'worthy' cans and letting the unwashed hoard go as is.

thu hien's picture
bobusn's picture

No excuses! Thanks for your dedication, Tyll!

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