Mechanical Transmission of Noise via Headbands

An accelerometer or interferometer would be neat. Measure at the back of the cup, the headband connection point, several points along the band, the other cup, etc. Setting up your axes and calibrations might be wonky work, or just ignore absolutes and simply look for trends. Look for rolloffs. Look for transformation/attenuation across the band. Repeat with a different clamping pressure and see how much that changes things. Repeat with mass loading the cups vs not.

I worked briefly with Nitinol back in university. It's perhaps best known for being a shape memory alloy, the kind where you bend it out of whack then heat it up and it magically returns to its original state. It's cool and buzzword worthy, though not terribly relevant for headphones from where I'm standing. I'll eat those words though if someone can show me actual charts where the nitinol headband shows any significant dampening of vibrations. Normally you have to get into actual hysteresis before it makes a palpable difference, and again usually in conjunction with other elements (typically in a support frame or embedded in a matrix). Again, not saying it's impossible, but I want more data other than someone saying they shoved a fancy metal stick up against their ear holes and the sound got better.

 

^Nope, but I dredged the thread back up because I'd forgotten that there was at least one headphone that had this weird problem, haha. Perhaps going full-on into researching this is more just for the sake of academic curiosity than anything else, though I imagine there are far more useful applications for any findings into the matter than hobbyist audio.

I was more a member of the objectivist camp for the longest while but hearing how much of a ridiculously obvious* difference a simple cable swap made to my ears in store meet settings (unfamiliar music and source but with stock cable to compare), I've come to appreciate that there's a ridiculous amount of sensitive variables in personal audio gear design.

@purr1n this doesn't mess with my inner peace, mind. It's just a slightly fun topic to look into that I figure members who're curious could waste some time on while stuck in quarantine, or elsewise while being hermits as per usual )


*fortunately for my wallet, the change in tonality was very much for the worse— made the Klipsch HP-3 sound thiccer and muddier than the Nighthawk. Also I Googled hysteresis, didn't know that there was a specific word for that!

 

Yup. Finally ordered an ACH-01 and I will report back with measurements in a week or two.

 

I mean, undamped resonance is resonance, so theoretically this effect could affect (did i do it right?) frequency response.

 

Another data point: The Superlux HD681B that I bought on a whim many years ago because I was interested in how much modding potential the thing has. Turns out... not that much. The 4.5kHz peak is here to stay and it's about as bad as it looks.
I got results similar to Keith Howard stock (green line). It's also a three wire headphone and it seems there's considerable electrical crosstalk. To eliminate it I simply desoldered the capsules (red line). The adapter is a much neater solution, though.

Note I got some minor 50Hz hum and some LF noise in the red graph. It's a semi-open headphone so at high frequencies it's much better than the open Sennheisers. I also expected it to fare much worse in the lower frequency region. The headband is very ringy. I actually got the idea after @Lyander posted his files for the Meze. I didn't tap the headband when I listened to the Mezes, but I don't think the Superlux is any better.
Well, the peaks at 155 and 189Hz are at an almost 20dB higher level than the HD800 in the same region. There's even a high frequency component to the ringing when tapping the headband, which makes me wonder if the peak at 1.5kHz may be related to the headband aswell. I suppose it's more likely it's rear radiation from the driver, but who knows.
EDIT: Just noticed there are even minor bumps in the FR at the same frequency as the crosstalk peaks!