That leads me to comment that the ADEL tuning may in fact be causing different impressions for different listeners. The fit could be different. The ear structure, shape and size are surely different. And there may be differences between each auto-adjusting ADEL module. This may cause some to think they are bass heavy while others like me would be more likely to say bass light than heavy. That said the bass is smack on perfect for me and my tastes.
Because there are significant differences in the size of people's ear canals, that equates to a difference in effective volume of the air chamber formed within the ear canal, when the CIEM is inserted, and, therefore, a difference in the compliance of that captive volume of air, between one person and another. It is not inconceivable that there may also be tiny differences in the size and compliance of different people's ear drums. Since (as far as I understand it), the ADEL module introduces deliberate additional compliance into the air chamber in the ear canal (whilst the CIEM is inserted), perhaps there are differences in the degree to which the ADEL module
interacts with some people's ear canals and eardrums, vs. the degree to which the module interacts with
other people's ear canals and eardrums.
I hope that hypothesis makes sense - it's difficult to describe what I am trying to convey. If the hypothesis holds water, then the essence of it is that differences in the net total of natural compliance within the formed air chamber of one customer's ears and another customer's ears would be a variable that 1964 Ears cannot possibly be expected to control.
Having said that, the ADEL module is obviously designed to compliantly yield whenever it is required to yield, regardless of other variables affecting the air chamber formed by the CIEM within the ear canal. In other words, if, perhaps, one person has a slightly lower net total natural compliance, then their ADEL module might perhaps be required to yield to a greater extent, to compensate. But that would represent a difference in
amount of air displacement via the module,
not that the module would be actually altering the value of air pressure
required for it to operate to a given extent. To put it differently: to move the ADEL module to a certain extent
(scenario 1), and to alternatively move it to an even greater degree
(scenario 2) should be entirely possible within the range of operation of the module, but scenario 2 would nonetheless probably require more air pressure to occur within the formed ear canal air chamber in order to for the ADEL module to respond (yield) more. So, if that were to be the case, then more air pressure might have some perceptible difference in the subjective SPL of the bass frequencies being heard.
Please keep in mind that
none of the above is being stated as actual fact. It is merely a personal hypothesis. Furthermore, we are considering tiny, tiny, minute, miniscule variables, and it is difficult to know if/how the ADEL module operates in differing scenarios. The hypothesis also assumes (
perhaps erroneously) that the ADEL module treats the air in a captive manner, and does not simply 'vent' air pressure to the outside atmosphere. If it does vent air pressure to the outside atmosphere, then much of what I've hypothesised can be discarded.
And, of course, there may simply be tiny, tiny variations in the compliance of each ADEL module rolling off the production line.
In any event, I personally am still very keen to hear the A12, and not particularly concerned by some feeling the bass may be north of neutral, with others feeling that it may be south of neutral.
Even putting the above hypothesis, and the ADEL technology aside, having owned the UM Miracle, I know very well that
some CIEMs may not sound overtly capable in the lower bass registers but can suddenly sound superb when a recording stimulates such a CIEM to perform in the lower bass registers. Far too many in-ear transducers are tuned with a mid-bass hump to falsely make the bass response sound more impactful or warm, and when a CIEM is designed with little or no mid-bass emphasis, it can,
relatively-speaking, be perceived as being 'bass-light' by some people.
Yet another potential variable in one person's subjective bass experience of the A12, vs another person's, is that I suspect (don't know, just
suspect) that the A12 may have an impedance curve which drops rather low. This can be surprisingly challenging for an amp stage to drive, even if the transducer design has a relatively high sensitivity rating, overall.
If the amp-stage output impedance is too high, or if there is insufficient current delivery, some subjective symptoms of these technical shortcomings can be that some low-impedance IEMs/CIEMs can sound unrefined in the treble and/or lacking in bass performance.
I welcome any reasoned rebuttals to any of this, but just don't shoot me. All I'm trying to point out is that whilst it is not impossible that the A12 might be flawed, I consider it much, much more likely that there are more benign reasons for differences in subjective aural experience of the A12 and I have seen nothing at all yet which concerns me, personally, as a potential future A12 customer.
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