I was at ALMA International's annual conference last weekend. (ALMA International is the International Association of Loudspeaker Manufacturing & Acoustics.) At the conference I gave a talk to an audience consisting mostly of audio industry acoustical engineers, discussing consumer-facing measurements, DIY measurements, and our measurements. Among other things, I showed them videos explaining how we measure headphones -- specifically, how we place headphones on the fixtures for measurement. I'll post more information and videos here on the forums after CES, going over the placement technique and tools we use here when we measure headphones.
This was my second ALMA conference, and it has become one of my favorite events -- the people, the discussions, the seminars, the whole experience. There's something to learn from everyone I meet and talk to at ALMA. I've been speaking with Dan Foley of Audio Precision (and current president of ALMA International) for quite some time about more progressive headphone measurement testing, and received some new ideas this weekend from engineers that we have the tools at Head-Fi to explore now. Anyway, more on that over time.
For now, I wanted to post some additional measurements taken of the Sennheiser HD800 (S/N 00342) and HD800S (S/N 13134) -- those are the second-unit HD800 and the brand new HD800S previously tested. (We have not yet received the brand new HD800's.) These measurements were done at the show, in conditions noisy enough to be far less than ideal for testing headphones. For these, then, we went to 100 dBSPL (at 40 Hz) to get above the din, and also tested at times when it was a bit less crowded.
The following are measurements taken by Brüel & Kjær at the show. I placed the headphones on the head, and Vince Rey from Brüel & Kjær did the final positioning and conducted the measurements using their latest HATS (head and torso simulator) and their PULSE analysis software. Here are the results:
The cursor on the HD800S measurement is placed at 80 Hz, so you can see that H2 is at 72.219 dB and 72.357 dB. The cursor on the HD800 measurement was not at 80 Hz, but you can see that the difference between these measurements is around 3 dB to 4 dB. This is similar to what we were getting back at the office.
I also took these headphones to the Audio Precision exhibit, and we measured both on Audio Precision's AECM206 headphone test fixture. Ryan O'Connor from Audio Precision helped with the measurements. Here's what we got:
In this test, the difference between the HD800 (gray) and HD800S (black) at H2 (80 Hz) is 2.866 dBSPL.
Again, these measurements were done in far less than ideal conditions (in the exhibit area at the show), but we did try to go loud enough and average enough to separate the fundamental and H2 (and H3) from ambient. These measurements are consistent with our other measurements of the HD800 and HD800S so far.
Thanks to Vince Rey and Ryan O'Connor for their help.
Since this thread is long -- making this topic a bit challenging to track -- here is a summary (with links) of the posts so far:
2017-12-27: For nearly two years, it has been accepted as fact by many that Sennheiser may have deliberately increased 2nd order harmonic distortion with the HD800S by 20 dB to achieve its fuller sound. Our initial measurements last summer suggested otherwise, and feedback from Sennheiser was consistent with our findings. We looked into the origins of this theory, and did an entirely new set of FFT measurements on the HD800 and HD800S we had on hand. You can see this at the following link:
Did Sennheiser Add H2 Distortion To The HD800S? (Our initial measurements suggested the answer is "no.")
2018-01-02: We measured a second Sennheiser HD800 and (with those measurements) offer a possible explanation for how this theory of deliberately-added higher 2nd order distortion in the Sennheiser HD800S may have come about. Long story short, our measurements so far do
not support the assumption that Sennheiser added 2nd order harmonic distortion to the HD800S, which is also consistent with feedback from Sennheiser. You can find out more at the following link:
Additional Sennheiser HD800 FFT measurements, as well as a closer look at the measurement that started this assumption nearly two years ago.
2018-01-03: We received a brand new Sennheiser HD800S (S/N 13134) from Sennheiser and measured it. I also posted the serial numbers of all the Sennheiser HD800's and HD800S's measured to date. You can see the brand new Sennheiser HD800S's FFT and the serial numbers of the other units at the following link:
Brand new, unopened Sennheiser HD800S measured
2018-01-04: I posted with more information and details about our measurement systems. You can read that at the following link:
The Audio Measurement Lab at Head-Fi HQ
2018-01-04: I posted a link to more information about (and photos of) the DIY headphone measurement rigs from which many (perhaps most) of the headphone measurements you see on the web are made. You can see this at the following link:
DIY Headphone Measurement Rigs
2018-01-04: We take a closer look at the InnerFidelity FFT that led to the nearly two-year-old theory that perhaps Sennheiser deliberately added 2nd order harmonic distortion to the HD800S to tune its fuller sound (a theory that our measurements so far do not support). I think more interesting than the HD800S measurement is the HD800 measurement which shows higher H3 than H2 (which seems to be largely responsible for the difference at H2 between these models in this one measurement). Was the HD800 in that original FFT measurement modified? The HD800 labels on it read "HD 800 DP Mod," whereas the HD800S labels read "HD 800S." Here's a link:
Taking A Closer Look at InnerFidelity's Original HD800/HD800S FFT
2018-01-04: @daltonlanny asks why I'm not depending on distortion measurements from
DIY measurement rigs (shown in a link above) to get us closer to answering this. I discuss this, including a link to an article by Audio Precision's Dan Foley that covers (among other topics) the importance of instrument precision in measuring distortion. Here's a link:
Should We Count On DIY Headphone Measurement Rigs For THD Measurements In This Discussion?
2018-01-08: I was at ALMA International's annual conference last weekend. (ALMA is the International Association of Loudspeaker Manufacturing & Acoustics.) I gave a talk at the conference to an audience consisting mostly of audio industry acoustical engineers, discussing consumer-facing measurements, DIY measurements, and our measurements. Among other things, I showed them videos explaining how we measure headphones -- specifically, how we place headphones on the fixtures for measurement. I'll post more information and videos here on the forums after CES, going over the placement technique and tools we use here when we measure
While at the conference, I visited the exhibits of Brüel & Kjær (B&K) and Audio Precision (AP) to measure HD800 (S/N 00342) and HD800S (S/N 13134) using their headphone test fixtures. Again, these measurements are consistent with our findings so far, and do not support the original theory (that Sennheiser deliberately added H2 distortion to the HD800S). Here's a link to those measurements:
HD800 and HD800S FFT Measurements From ALMA International's Conference (That is a link to
this post.)
2018-01-14: We received three brand new HD800's from Sennheiser, serial numbers 49282, 49759, and 49760. We did a preliminary FFT measurement of the highest-numbered unit (49760), and it is consistent with our other measurements so far. I'll post the results later, after we've measured all three of these new HD800 units.
2018-05-19: A gentleman on reddit (username "oratory1990") posted measurements of his HD800S and a friend's HD800 on reddit. I was pointed to his thread there and asked to respond, which I did (here). You can read my response (and additional details and measurements) at the following link:
More HD800 and HD800S Measurements At Higher SPL And Lower Frequency (20 Hz)