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I do believe that is one of the best things with the Abyss, being able to rotate the pads for a good seal.
Responses abyss: yellow = pad pressed against measurement frame, blue = less sealed, pink = even less sealed
The bass response (70-80 Hz) of the Abyss objectively varies by nearly 10 dB, depending on the seal or not of the pads.
According to several people who have tested the Abyss, sealing pads seems impossible.
Can we talk of true fidelity about this headphone with a response bass heightened by nearly 10 dB if sealing pads impossible ?
(as if we were to increase the bass of +10 dB with the bass potentiometer of an Hi-Fi amplifier to have more spectacular bass).
That's interesting. I've had half a dozen people come over to my place and from what I am aware, none of them had a problem with getting a good seal, if they so wished. It was simply a matter of rotating the cushions so the thickest part rested on the nape of the neck instead of directly behind the ears.
Moderate seal:
Good seal:
That's interesting. I've had half a dozen people come over to my place and from what I am aware, none of them had a problem with getting a good seal, if they so wished. It was simply a matter of rotating the cushions so the thickest part rested on the nape of the neck instead of directly behind the ears.
Okay - found out what it means. Still looks strangely bad for the abyss, no?
An obvious point, the measurements made by the French forumeur differ quite significantly from yours on the frequency response (function of the sealing pad) (ie you can find: bass roll off with Lack of seal:-5db at 20Hz, the French found: bass roll off with Lack of seal: -20 at -30 dB at 20Hz with an +10dB peak at 70-80 Hz with a lack of sealing pads) .
On the issue of the Abyss port for a perfect seal, even turning the pads, you acknowledge yourself that there may be a real problem for some people (depending on the anatomy of the head) making sealing sometimes impossible.
You said : “ I didn't have a problem with seal with the thick part of the pad toward the nape of my neck, though I can definitely see it as an issue with some people. With the above tweaks in place, I do prefer to run the Abyss fully sealed.
Seems with a good seal the bass smoothes out flatter along with very slight increase in treble energy around the 8-9khz region. But what could be the reason for -5dB decrease in FR Mag with a good seal between the 5-6kHz mark? Is something being cancelled out?
I purposely provided a graph which was more of an apples to apples comparison. The question really is: how much group delay (in terms of ms) can one hear to notice a difference? So in that respect one needs to be very careful in the presentation of data. Also, there's a little bit of roughness in the group delay measurements which are of no consequence, so smoothing the graph a little bit doesn't hurt. "Consensus" among speaker builders seems to indicate that the audible threshold is about 25-30ms. Even then, there is a lot of debate concerning this. So in that respect, the graph should be visualized more like this:
Finally, one needs to understand what context the group delay measurement is used in by speaker designers: bass reflex boxes and crossover design. For open headphones, this measurement doesn't provide anything meaningful which can be correlated with subjective experience. If the measurement has little or no correlation with subjective experience, then it's useless. In such cases, to present it as a differentiator (and in such a way as to intentionally or unintentionally highlight differences) only adds to confusion of the uninitiated. Because people who are unfamiliar with interpreting measurements have a tendency of makings all sorts of stuff up.
Finally, one needs to understand what context the group delay measurement is used in by speaker designers: bass reflex boxes and crossover design. For open headphones, this measurement doesn't provide anything meaningful which can be correlated with subjective experience. If the measurement has little or no correlation with subjective experience, then it's useless. In such cases, to present it as a differentiator (and in such a way as to intentionally or unintentionally highlight differences) only adds to confusion of the uninitiated. Because people who are unfamiliar with interpreting measurements have a tendency of makings all sorts of stuff up.
From what I read (which is a great deal less than you have admittedly), this really isn't just related to bass reflex boxes and cross-overs but also other things including positioning of speakers/transducers. So I take it to mean that (in the case of headphones) you throw a signal which consists of >=2 frequencies with a known phase relationship between the two at a driver, then look at what comes out?
I am wondering how the system gets this result? Does it just send out an impulse input, fft it and look at the phase against freq? I recall an earlier plot where the abyss at about 350kHz kindda went 'advance' with -ve group delay which is a little weird and looks like some kind of resonance was crossed or something which is even stranger as it doesn't have a cross-over to do that sort of thing. I admit i'm no expert (did study vibrations and control back in my years, but not audio specific), but saying tens of milliseconds is inaudible is perhaps too dismissive? Don't get me wrong, all I'm saying is that many, many experienced ears have not mentioned much wrong with the Abyss so a glaringly poor result as the above must have manifested itself to someone - either that or there's something not quite accurate about the measurement/processing of the data. May be it's to do with the fact that the drivers are much closer to our ears than with speakers? May be the group delay results is an analysis of a square wave input? This would be an odd choice cos you'd need lots of square wave frequencies to get an accurate result?
I don't really know to be honest, I've never had the equipment/computing power you guys have these days so I'm not sure what's currently possible/done. But I am curious about the fact that a seemingly relevant measurement does not show itself to be audible. More importantly, the bass is an area which nearly all says the abyss excels yet seem to come out worst on these plots...
Vibration and controls, I had such hard time getting a handle on state space domain, never understood it I think
My guess on the group delay was simply looking at the delay in cross-correlation function between input signal and measured SPL for some kind of band limited signal. Maybe arta documentation says more?
Arnaud
The creepy/weird thing is, a post-grad I worked with was a French dude called Arnaud.
Eh! I was at VTech, did MS in Vibration & Acoustics / Active Noise Control of PC fan noise. I know a few french people who also did controls but no other arnaud