To me, the ER4S has bass linearity until about 45 Hz, when it starts to roll off pretty badly. I think the issue is that the ER4S underdamps the driver with a pair of resistors, and that affects the way the bass responds to any amplifier. Even though I appreciate the ER4's smoothness, its bass doesn't ever feel convincing to me.

Tom: do you think it would be worthwhile to use a crossover network that adds more series resistance to the ER4. Obviously it would have to shunt away the extra resistance above 1k or so (like the ER4B did?)

 

On the other hand, custom-molded versions of the ER4S tend to be more peaky in the upper midrange perhaps because of tubing and the acrylic interface.

The custom molds I have for the Etys are soft silicone, not acrylic. But you're right about the added peakiness. Tri-flanges are not only smoother and more tonally correct, but also more detailed. Customs do have the ability to give a wider, less "in-your-head" image though which can be a nice effect.

Alright, so I'm doing quick ear comparos between my lowly amp whore HD558 and these... No way these sound like the Senns to me... They have bass, but IMO these are more analytical and have obviously less bass (well, at least to me). That said, I can easily and clearly perceive tones all the way down to 30 Hz with the Etys, just the tonality I get is towards the analytic side of things.

As far as compensation, I fully understand what Marv is saying. I get pretty consistent results with my coupler all the way up to 9 or so kHz. However, this is not an official, standard, Pope blessed coupler so the gap shape and volume may necessitate a different compensation + whatever adjustments. I'll see what I can get, but in the mean time, relative results across measurements should be comparable.

So if one feels Etys are the neutral reference, other things like the Dunu, SHE cutetips, and most random dynamic and perhaps even 100 driver BA designs may sound uber-bassy.

Closest things I've heard to these Etys would be the Phonaks PFE112 (gray filters), followed by the Noble 4s and indeed the Noble FR/PR in R config.

I really was originally skewed towards thinking "objectively" that the PFE112s where neutral given the measurements and the standards, until I had them on my ears. For a long time I tried all kinds of tips (including some Comply ones that I gave away in the end), cuz I thought the problem was seal... to no avail and pretty much gave up on IEMs. Tried some "OK for the $" dynamic IEMs to get more measurement baselines, and bass absence problem went away using similar size and shaped tips, even "slightly" bassy ones according to some reviewers, which helped me rule out the seal problem theory.

You guyses know I felt the Noble 4s were a bit bass lite to me. Maybe with IEMs things get a bit more relative, Dunno...

Don't think so... HD6x0s have a bit less of that, and still sound close to the HD5x8 to me.

When Milos came over with the 009s we tried an uber-bassy track from youboobs. The 009 might have been a little attenuated relative to some of the dynamic cans I have (HD600s and such), but they still delivered skull crushing bass from that track. LOL! I remember the look on Milos when I was checking that track up... One could hear the stators going "tic-tic-tic" loudly from the outside... None of that bone crushing bass with these. Gets better if one pumps up the volume though. Could see there being a deficit in the ~45 Hz area, but who knows.

Kinda: