Coherency in Multi-Driver IEMs

[carlcamper]

I recently read an IEM Review here which talks about Multi-Driver IEM coherency. To paraphrase, the reviewer stated that the various drivers were slightly out of sync in terms of attack and decay. I'd like to ask if this is a real, measurable phenomena, or is this just subjectivist speak?

 

[heraldo_jones]

I have more than 50 iems and I must say the ones with dynamic drivers have a much more natural than those with multiple balanced armature.

 

[majingotan]

I recently read an IEM Review here which talks about Multi-Driver IEM coherency. To paraphrase, the reviewer stated that the various drivers were slightly out of sync in terms of attack and decay. I'd like to ask if this is a real, measurable phenomena, or is this just subjectivist speak?

It's audiophool cool-aid IMO. It has to do with wonky frequency response peaks. Keep in mind that the FR curve shown has some smoothing applied to better show the curve rather than no smoothing at all so there might be certain peaks/resonance that is smoothed on the graph. Probaly the unit that the reviewer received has FR issues (unit to unit variation) which caused the perception of incoherency. In my subjective listening of tens of IEMs, I've never heard of an IEM that sounded "incoherent" after EQing to a specific curve. I have a 5 driver IEM, 1 DD IEM, 1 BA IEM and all the frequencies in the audible range sounded perfectly synchronized when EQed pretty close to DF target (I prefer that over Harman BTW). Even at their stock tuning, none of the ever sounded out of sync whatsoever.

 

[carlcamper]

It's audiophool cool-aid IMO. It has to do with wonky frequency response peaks. Keep in mind that the FR curve shown has some smoothing applied to better show the curve rather than no smoothing at all so there might be certain peaks/resonance that is smoothed on the graph. Probaly the unit that the reviewer received has FR issues (unit to unit variation) which caused the perception of incoherency. In my subjective listening of tens of IEMs, I've never heard of an IEM that sounded "incoherent" after EQing to a specific curve. I have a 5 driver IEM, 1 DD IEM, 1 BA IEM and all the frequencies in the audible range sounded perfectly synchronized when EQed pretty close to DF target (I prefer that over Harman BTW). Even at their stock tuning, none of the ever sounded out of sync whatsoever.

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Kabayan, thanks for that rational response. I also suspect that a lot of subjectivist opinions aren't grounded in quantifiable measurements, looks like this may be one of them.

 

[dc655321]

I also suspect that a lot of subjectivist opinions aren't grounded in quantifiable measurements, looks like this may be one of them.

Indeed. Ask the person throwing “coherency” around to define it. If their response is word-salad and/or does not use physical dimensions (dB SPL, volts, etc), they’re full of crap.

 

[frix]

I thought it had to do with missaligned phase. Thats also a real thing in speakers. How audible that is, is another question.