Tyll Hertsens Blog

I'm curious why you think that the bass hump isn't some resonant artifact of the measurement head that needs to be addressed in the compensation curve.

Here's my theory: It's due to the way that the sound waves impact the measurement head causing the air inside of it to resonate resulting in higher sound pressure on the measurement mic.

It is definitely centered around a harmonic of the big hump at ~3.5kHz.

I'm prolly just pulling things out of my ass though. I haven't reviewed my physics for some time now.

The best looking graph is the HD600 ...left channel. That wasn't the pair that ate your screwdriver on one of the drivers, was it?

Is web graph tool underdeveloping? Hallelujah!

The HD 600 and HP50 graphs match up pretty well with what I heard (and still hear with the HD 600) from both headphones, much better than the previous compensation curve. I felt the HP50 had too much mid- and upper bass* and a bothersome spike in the mid-treble, with a sort of well in between cutting out some of the upper harmonics on vocals. The HD 600 fares much better and, apart from the weak sub bass, its plot looks almost ideal.

*Though, strangely, distinctly poor extension--I suspect the pads weren't sealing on the bottom despite the vice-like clamping force.

Just out of curiosity were any of dummy head measurements of the speakers made with one ear of the head pointed towards the speakers? Since the dummy head is designed for what you could call on axis measurements it seems like it would be worth trying in several orientations to confirm the shape of the ear is not affecting these in room measurements.

It's much closer to reality than ID compensation was. But, I too am intrigued by that hump at 40hz with your dummy head measurements. Is a bass boost at 40hz desirable or can we dismiss it as a resonant artifact?. I do think, however, that leaving the bass flat for the compensation curve is the best choice.

Just wondering why we think the compensation curve should be subtracted from the measurement? Do we have a good argument why the offset is independent of the sound level? Has anyone checked whether the compensation curve has the same shape with sweeps at various levels? Non linearities can creep everywhere.

I've been doing this for a few years with Innerfidelity, by placing each headphone's responses in a tab, and clicking back and forth between the tabs.

Thank you so much for your work on this. The graphs have traditionally not represented very well what the end user hears, and the new graphs are much more representative of how these headphones sound, especially in the treble. The one thing that still bothers me slightly, though, is the dip around 4-5kHz that seems common to all headphones when measured and compensated. I'm not sure how accurate that part of the compensation is.

Please just provide the RAW measurements in a way that they are easy to read. Having 10 thick grey lines over another makes it very hard to distinguish them. Please have them averaged or select the two most reasonable.

Hey Tyll,

I think the new compensation looks better so congrats for that.
The new graphs fall a bit to quickly starting at around 700Hz up to 1500Hz, not sure if I can hear that. Otherwise the treble looks better. I've always thought HD800's brightness was misrepresented on your spreadsheet.

Here's the question:
(Since the perceived tonal balanced is volume dependent - more or less, along the equal loudness contours)
What's the volume @1kHz for which (you think) the new compensation is targeted?

On a side note, sad to hear about the spam filter problem. I was writing for a while the other day. Thanks for letting us know what happened anyway.

Regards,
Me x3

Innerfidelity has the best headphone measurement database right now and the Graph Tool will make it super awesome! I'm so excited I have to create an account just to tell you this: Thanks for all your work! Really looking forward to this :)

I don't get it. we start with a clear hypothesis about having the sound of speakers in a good room and go for it. then you don't like the results, which is fine, it's one idea with one room an one dummy head. then we enter the twilight zone.

if your real purpose is to have a compensation curve that reflects your impressions, maybe you could just draw it by hand for several headphones, make compensations out of it based on raw, and then average that.
but taking real data and manipulating it until it looks the way you feel, I don't like it one bit. only ugly marketing should do that sort of stuff.

and TBH it annoyed me when you made your own Harman curve too. it works, it doesn't. you have all the necessary data or not, that's life. but cherry picking the objective elements you subjectively like, that's not objective anything, but it's like alcohol free beer, it really looks like beer.
I kind of like the final curve, I'm sure you get how that's not my issue.

now that I've lectured you like I knew anything, it's the best time to ask for something(I'm such a great negotiator). I'd like to see the raw front looking dummy(no angle), with stereo and with only one speaker as you seem to have both. to see how much the response changes on that head from correct "crossfeed"(IDK how that should be called)of both channels, against one channel for one ear like headphones.

and congrats for the graph tool being made. that's really good news.

When measuring with a dummy head in a room, diffraction, refraction and reflection of the sound field around the head will create a spatial acoustic shadow zone. This phenomena then effects the measurements at the ear positions (leading to the Sombrero hump), but would not influence the single microphone measurement (see Harmon's room measurement above).

The cut-on frequency varies from 3-6 KHz, and is often found at 3.5 KHz, as noted above. This is relatively constant due to the geometry of the head, as noted in Tyll's summary of the measurements.

Does it then make any sense to try and use this type of dummy head room measurement to develop a headphone target curve, where the sound field is immune to head diffraction effects?

In addition to the room influences on the measurements dummy heads are made of different materials than real heads. I was reading that bone has a very unique combination of high stiffness and high vibration damping and only some exotic alloys including In can approach or better that and both parameters influence the acoustic properties of that structure.
Likely the material which is used to make the pinna will have different properties (including damping and absorption) than real ones. Obviously shape variations (especially of the targus) will have acoustic influences.

Interesting work, Tyll, thanks again for your contributions to the community!

One thing I note is that the curve appears to create a notch/discontinuity around 1K. I suspect it very unlikely almost all these headphones have a midrange discontinuity like that, it's a pretty critical area, and so it looks to me like there's an issue there that might create concerns about midrange linearity.

At the broader level, I've always had the concern no compensation curve actually allows a headphone with a reasonably flat acoustic response (assessed via sweeps, noise, etc) to display as "flat." The general form of the curve above 1K probably makes intuitive sense to enthusiasts with regular exposure to headphone response curves, but I think they'd be quite counterintuitive to people not as steeped in the craft.

In the absence of a standard "flat" compensation curve what about publishing a difference curve relative to your target? Musing out loud, people would be able to easily see where the response is on target or off and thus even if they're not able to intuitively process what the 4K dip really sounds would a differential plot would make it more intuitive?

Tyll and Dr. Olive, check out Figure 1 in this post:

https://www.innerfidelity.com/content/warren-tenbrooks-summary-head-meas...

The JBL M2 curve that Charles Sprinkle loaded into the DSP prior to your measurements is very close to the Reference Room speaker target "RR". These two sister target curves have the highest level of bass, consistent with your head measurements.

I wrote:

"...note that Figure 4 in Olive-Welti-McMullin AES paper 8867 (2013) presented headphone listening tests where corresponding curve RR1_G was preferred over curve RR_G. Presentation slides summarizing the preferences were posted by Dr. Olive.

In my opinion, the evidence weighs in favor of curve RR1 as a neutral reference curve over the typical Reference Room house curve, RR, used during Tyll's measurements..."

So, speaker curve "RR1" has 2-4 dB less bass 100 Hz and below and was documented as preferred by Harman when used as a basis for the headphone target.

I think your measurements bore witness to how the fingerprint of the bassier selected speaker compensation curve can be seen throughout the process.

I don't have any insights into the high frequency response, other than our discussion of comb filtering when two speakers played versus none with a single left speaker.

Great work - and I love the idea of the comparative online tool!

I seem to have missed the point of the new calibration curve though. If the new curve is supposed to be more accurate, why would we want to smooth away all the detail (and completely remove any low-frequency effects)?

I'm used to looking at Innerfidelity's compensated curve plots as is. I guess my brain doesn't want to re-learn new curve shapes without understanding what's behind this "progress". Being able to plot deltas will be awesome, but as an earlier poster mentioned, there's often an awful lot of variance between measurements - often larger than difference amongst headphones. See for example the Monster Turbines, vs the Monster Turbine Copper Pro. I'd swear they were the exact same headphone. On the other hand, look at the IE800 - it's L and R measurements seem to have come from two totally different headphones!

One final point on IEMs. We really all (myself included) have to get into the habit of stating what tips they were measured with. Tips have a huge effect on the spectra, especially foam vs silicone.

Nope. You cant measure what we see by putting a camera in an eyeball, any more than you can measure what we hear by putting a microphone in an ear.

Subjectivity rears its beautiful head here. The brain subjectively interprets the SPL data at the eardrum, and trough the entire inner ear as it is converted into a representation of SPL in nerve impulses. It wouldn't help to measure those impulses on the way to the brain either since the processor (brain) actually synthesizes our picture of the sound, with it's own correction curve, which is as individual as our set of ears are.

We will just have to make tests like Harmon did to find averages among listeners in comparing cans to a reference system.

I'm really looking forward to the InnerFidelity Graph Tool to be able to compare headphones live on the web. I'm feeling like a kid again.

I refer to Tyll's headphone measurements as an objective data point, but it appears that he's just arbitrarily gone and shifted the goal posts.

I wonder how the frequency response would change if the dummy had arms and an upper body.

We've been marketed the concept that "Ruler Flat" is desirable, for a good many Decades.

It's nonsense

Real World is a Curve.

Back in 2015, after not being able to hear the supposed wonderfulness of the Schiit Yggy DAC, at the Ann Arbor headphone meet, I had my own hearing evaluated at the University of Michigan's Ear Specialists.

Not only was my hearing well off "Flat", my headphone system ( Schiit Asgard 2 & Sennheisers ) was well off the ideal "Curve" .

Thru the magic of Equalization, UofM adjusted my little system to closely match Harmon's Curve, taking my own hearing ability into account.

Viola, I have a wonderful music system that I'm not in any hurry to replace or up-grade ( although I'm planning a Focal headphone and perhaps an Feliks amp.)

Tyll & Bob Katz are the leading folks on all this for the entire Audiophile World. I can't find any other Consumer based reviewers mentioning anything about any of this.

For me,

Tyll is Professor Tyll!

Bob Katz is a visiting Professor

Tony in Michigan

If you had a copy of the plain text numeric data for your graphs, you could probably write a quick script that would generate all the PDFs again for you in seconds.

The raw data as measured trough Tyll's dummy head represents perceived sound below say, 900 Hz? Yes it does, so we can leave it alone when trying to conger a subjective response curve. I think we do appreciate and desire the bass lift of a good listening room. When your head IS the listening room, boosting the bass to make headphone "match" room measurements producing a measured curve to approximate the preferred room make the cans WAY too bassy. I am fairly certain the RAW data below 900 Hz is a good approximation of what we subjectively consider accurate.