SCIENCE!Also shameless plug:
Hackerspace Warsaw &
GalleryI'm about to endeavour into making a custom IEM from grounds up, starting with ear impressions, through design, tuning to damping and maybe even measurements.
The whole idea is to make the most neutral yet musical IEM possible.
Also mess up horribly and spend lots of cash. (I bet I could buy about 2 ready-made TOTL CIEMs for this.)
Hopefully no electrocution will be involved this time - fortunately, last time it wasn't me being zapped.
Current plans involve:
1) Ear impression materials and tools - in progress, thanks to Corey
2) VSonic GR07 for a neutral dynamic driver CIEM experiment - ordered
3) 100% silicone with citric acid (medical) - acetic acid is smelly, but in a pinch could be used
4) Silicone caulk with gypsum (need pure gypsum and have to find the right proportion)
5) Custom tips for IEMs - Sony MH1, Hifiman RE-ZERO and RE-600 - to test the impression and molding process
6) Hacky 3D scanner to digitize the impression - to be done this weekend
7) Sonion 2354 tweeter armatures for neutral 4-way BA CIEM experiment
(The other two are Knowles TWFK and Sonion 26A005/8, which I already have. TWFK counts as two, the FK will be useful for bass.)
8) Silicone tubing - have some 4/6mm tubing as well as 2/4mm. Might need even smaller, e.g. 1/2mm.
9) Detailed crossover design for the BA CIEM
Optional further ideas:
A) PMA (polymethylacrylate) elastomer inserts - faux leather
B) UV printed acrylic shell
C) Using different 3D printing stock from ABS (e.g. PP - polypropylene)
D) Replaceable cables, probably Westone sockets
The choice for dynamic driver experiment is VSonic GR07's driver, because it's reasonably neutral and mostly hampered by the not that great, mostly undampened shell and too narrow nozzle. This driver is also nicely protected against likely mishandling. (Yes, I've killed a few IEMs while taking them apart. The membranes are easily damaged.)
Interior will be dampened, most likely with cotton, but perhaps glass wool. I also considering sourcing some Kapok cotton and silk.
This driver doesn't really require any venting.
The BA CIEM will have an external crossover unit for ease of tweaking and building, kinda like UM PP6. I'll try to use lowest values possible, probably 3+3rd order Butterworth for good phase linearity and excellent frequency response. Alternatively Linkwitz, 2nd order.
I'll try first order too, but I suspect that this will cause some interactions.
Current idea of this setup involves using both FK and Sonion-low (26A005/8) as bass drivers and mids drivers, WFK and Sonion-high (2354) as highs driver. The crossovers will be probably placed at 6 kHz (FK/WFK - B2 uses default 4.5, this might be good too if I cross Sonion-high lower) and 5k or 8 kHz (Sonion-high), 3rd order Butterworth likely. Sonion-low (26A005/8) will be running full range.
Resulting impedance should be relatively low, around 20-50 Ohm, and flattish, similarly phase response. High sensitivity. The peak/dip pattern falls such that the drivers mostly complement each other.
If it becomes necessary, I'll also have Knowles dampers, but I'd rather not resort to them.
Venting shouldn't be necessary here really - even the Sonion drivers don't need it really unless they're used as a sole bass driver.
Tubing layout is not determined yet.
The armatures
in question all have a different wideband sound: Sonion-low is warm smooth sounding, Sonion-high is sharp and coldish, FK is quite sharp while WFK is nicely smooth. Properly blended, this should give a neutral timbre.
I will either get a measurement microphone and jury-rig a measurement setup, send them to Anax/purrin for measurement, or both once I'm happy with the sound.
Starting a production line is not really planned, but I might do a one-off request, who knows.
Datasheets of the BAs:
Sonion 26A005/8Sonion 2354Knowles TWFKVisual ear impression and insert manufacture instructions (for those who can't understand Polish; there are some descriptions for others) are here:
http://www.ia.amu.edu.pl/index.php?option=com_content&view=article&id=76&Itemid=16Compared to this lab, my gear will be better in a few ways and worse in others. For example, I don't have a dryer, "gel machine" and pressurized equipment, but instead I will have many more kinds of lacquer and grease, lots of cyanoacrylate glue, various solvents, better mechanical tools.
