I definitely take into account for people's standards with regard to price/performance ratio, as well as tastes, and I'm still a little baffled, but enough of that (PM'd you)...

Back to the C4, that's a ~16 dB drop between 2.7 and 3.7 kHz... I was talking to someone else who was familiar with IEM design, and he was also suspecting weird phase cancellation possibilities around there. It's tough to have that ridiculous a gap between the two drivers, even with the widening caused by a high pass and its analogous low pass.

However, the K3003 is by far the most electrically linear and phase linear TWFK-equipped earphone I know, and it too has that dip.

All I know is that I've been working on my own custom-design IEM, and I've completely moved away from the TWFK precisely because of this problem.

On the TWFK, I am suspecting that the internal crossover between the mid and treble is first order and hence 90 degrees apart in terms of phase shift. In conjunction with the how a bass driver is implemented - or how it's crossed over with the TWFK unit, that 90 degree phase shift between the mid and treble could be doing some funky stuff interacting with it. This is assuming all crossovers are first order = very slow roll-off = high interactions between drivers. (I highly doubt second order because there's just not enough room to cram in so many crossover components, especially for a 3-way.)

The distances / bore lengths are too small to play a difference at audio frequencies to make any difference in terms of phase differences via time alignment. I've taken a look at the step responses the few IEMs I've measured and they are all perfect relative to speakers. It occurred to me "doh". A few millimeters (at most) is not gonna matter. It's not like delaying the main speakers 80ms so the subwoofer placed farther out in the corner of the room isn't delayed.

I don't have enough data, but I'm sure there are other IEMs using the TWFK without such a extreme dip.

Okay, so if we're looking at some of the same basic set-up as the 4.A/Ai or even possibly the w4 then why would people be saying the C4 is so detailed versus other customs while the 4.A isn't getting that sort of hype? I mean, other than different price points?

Quote from: Kunlun on November 15, 2012, 05:06:22 PM

Okay, so if we're looking at some of the same basic set-up as the 4.A/Ai or even possibly the w4 then why would people be saying the C4 is so detailed versus other customs while the 4.A isn't getting that sort of hype? I mean, other than different price points?

Most of the impressions I've seen on the quad heir custom have generally been positive.
The market for CIEMs is smaller than the universal market at equivalent price brackets (finding an audiologist to take a good impression and the worries about a refit, ease of demo and resale). I would think this would prevent most FOTM from bubbling over. I don't know if anyone is familiar with that model and the C4.

Yes, the 4.A has gotten good reviews on HF, but shouldn't the detail be very similar for earphones that have the same basic armatures? I'm thinking choice of acoustic filters plays a role as well.

As for FOTM, that definitely exists with ciems. Look the JH3A debacle where Jerry Harvey lied and used head-fi'er pre-order money to develop a vaporware product.