I've been listening to my Etymotic ER-4PT/S for a few hours now and I have been listening to Spotify premium at 320 Kbps. I also have a few tens of gigabytes worth of high resolution 24 bit 192 kHz FLAC loss less files from HD Tracks and Chesky among others. I have been listening to my music library of LAME 3.9.9 --preset-insane 320 Kbps MP3 songs. The 4P -> 4S adapter really makes them ruler flat in terms of accuracy and neutrality. Now, my ER-4PT/S sounds more transparent with greater resolution and detail retrieval especially low level sounds. The dynamic range is a bit wider with greater contrast, but it is not by a large margin. The treble is airy and well extended. The overall sound is more coherent with better tonal balance.
I feel like I am a recording engineer or a producer. I can listen to my music from a trustworthy perspective and I can still spot the deficiencies in the different songs regarding mastering quality. Well mastered albums have an uneven keel in terms of quality from track to track depending upon where they source the music.
I can understand why these get passed up for something shinier or newer. There is not much to the design or the technology by today's standards. They're considered to be ancient, but they are timeless classics. The ER-4S lets the music through with the fewest coloration possible. It brings you closer to the music with the fewest possible distortions. It's not for everybody. If you have a lot of standard resolution 16 bit 44.1 kHz music in loss less format like FLAC or WAV or AIFF, then the ER-4S will reveal everything about your tracks with merciless scrutiny and precision. You will wind up analyzing your audio system rig and your music while you listen to your favorite tracks. After a while, this can get tiring unless you are a freak about stuff like this.
I can't say that they outperform custom IEMs that cost several hundreds or thousands of dollars more. However, they hold their own if you require extraordinarily high passive sound isolation and extreme accuracy and sound fidelity. If you want to know which audio codec, format, bit rate, resolution, and other options you should rip, encode, compress, or transcode your music files, get the ER-4S to determine the results with superb accuracy. You'll need a top of the line audio rig to make it worth your time and effort.
It's going to cost several orders of magnitude more money to match or surpass the ER-4S by going the custom multi-driver balanced armature or dynamic driver IEM route and you won't get it all unless you spend thousands for a top of the line custom personalized model. If you are looking for a full sized headphone, it will cost you even more money to beat the ER-4S and it won't outperform in all categories. I have the Ultimate Ears Ue-18 PRO and I am auditioning the Sennheiser HD-800 with the Cardas Clear headphone cable and these products cost thousands of dollars more than the ER-4S and they do some things better while other areas need improvements.
Here's my home audio rig:
Meridian 808v5 CD player
HeadRoom Ultra desktop amp with DAC and desktop power supply
Ultimate Ears Ue-18 pro
Etymotic ER-4PT with 4S adapter
Monster Signature Series Pro Power 5100 Power Center UHC
Cardas Clear power, RCA interconnects, USB cabling
LaCie 4Big Quadra 10 TB USB 3.0 external HDD
Western Digital My Passport 2 TB USB 3.0 Portable external HDD
System76 Leopard Extreme desktop PC
System76 Lemur Ultra Thin notebook PC
Verizon FiOS Quantum
ASUS Blu-Ray USB 3.0 12X external CD/DVD/Blu-Ray burner
CrashPlan+ family plan for 3 years
yes, it's true.
Here's my PCs:
I don't see the point in transcoding to the latest and greatest audio codec and format of the day just because it's popular. With my large library, it just takes too much damn time even though I have a System76 Leopard Extreme:
2nd Generation Intel Core i7-3970X Extreme Edition 3.50 GHz L2 15 MB - 6 Cores with Hyperthreading
64 GB - 8 x 8 GB - Crucial Elite Quad Channel DDR3 - 1333 MHz
4 GB nVidia GeForce GTX 690 with 3072 CUDA Cores
960 GB: LSI Hardware RAID 0 - 2 x 480 GB Intel 520 Series SATA III 6 Gb/s Solid State Disk Drive
CD-RW / DVD-RW Dual Layer [two of them]
Internal SD, Memory Stick, Compact Flash Card Reader
Internal PCI Express 802.11 bgn
27" Full HD SuperThin Widescreen LED Display (1920 x 1080)
Logitech Wireless Illuminated Keyboard and Performance Mouse
3 Yr. Ltd. Warranty and 3 Yr. Technical Support
Asus 12X Blu-Ray USB 3.0 burner
LaCie 4Big Quad 10 TB USB 3.0 HDD
Western Digital My Passport 2 TB USB 3.0 Portable HDD
System76 Lemur Ultra Thin (lemu4):
Intel Core i5-3210M
Corsair Vengeance 2 X 8 [16 GB] 1,600 MHz RAM
Crucial M4 SATA-III 6 GB/s 128 GB SSD
Intel Advanced-N 6230 802.11 BGN
14.1" 1366 X 768 LED
2 USB 3.0
1 USB 2.0
SDXC memory card slot
8X DVD burner
yes, it's true.
I'm keeping my Etymotic ER-4PT/S forever until they break. They'll last many years. To my ears, these are the best high end universal IEMs if passive sound isolation and accuracy are your top priorities like mine.