Actually other than some full beryllium types (eg for CHIFI IEMs it be expensive stuff like the DUNU LUNA and Final Audio A8000), I suspect a lot of cheaper sets that are beryllium plated and coated may be a marketing gimmick. For sure there are some beryllium sets that are properly implemented and the beryllium deposit really makes a difference to the sound, eg textured bass, takes EQ like a champ, those seem to be hallmarks of beryllium drivers. But I've heard some purported beryllium budget CHIFI IEMs that don't really sound different from a conventional driver type IEM.
The KBEAR BElieve is also purported to be a full beryllium single DD, but the jury is still out on whether that is true. I know BGGAR and some folks have opened the shell to show that the driver looks like beryllium, but nobody has a spectrometer or tools to really prove whether it is a full beryllium or some other metal or even the % purity.
The official DUNU folks here on headfi made some interesting comments about the lining/material of beryllium drivers:
https://www.head-fi.org/threads/the-discovery-thread.586909/page-2968#post-15288735
"The PVD layer has to be thick enough and the microscopic grain pattern has to be regular enough to confer that pistonic motion beryllium is so famous for. That's why our sub-$100 products (DM-380 and DM-480) are still titanium drivers. Even the TITAN 6, at $139, is only coated on one side."
Personally I have a sneaky suspicion that at the budget CHIFI level, some of these novel material applications on drivers may be an element of marketing gimick, to stand out from the fierce competition at that price range. For all we know they are just sprinkling a few flakes of certain coatings on their drivers instead of uniformly applying it in the prescribed quantities to truly be effective.
Slater has a good post here about this issue:
https://www.head-fi.org/threads/chinese-asian-brand-iem-info-thread.820747/page-1874#post-15293524 -> see the last paragraph, if the material is sprayed on improperly or not implemented well, the driver may actually sound worse.
So DUNU says they have difficulty implementing this Beryllium coating in their sub $100 USD gear. And we already see unit variation in
macroscopic areas in these budget CHIFI in terms of sound and build, so forgive me for being skeptical that some CHIFI budget IEMs can ensure good QC for all their units when it comes to
microscopic application of these novel materials in the proper layering. Possibly for expensive high end gear like DUNU LUNA or Focal Utopias, the beryllium may be properly coated and the sound is really unique cause of these properties.
All these special materials, be it beryllium, graphene or diamond or whatever, needs to be coated and implemented properly to truly make a difference. In fact if you coat it wrongly it may make the driver sound worse by affecting its physical properties.
As for beryllium toxicity, it is toxic to process and postprocessing, probably when the driver is damaged and particles are released and inhaled.
Focal Utopia has a warning in the phamphlet with their headphones:
Kind of an apples to oranges comparison as most IEMs will not compete with earbuds in soundstage. Earbuds are closer to open backed headphones than IEMs actually.
IEMS generally have better isolation and hence subbass response, and they may also be more detailed as the transducer is closer to the ear.
FWIW, $5 - 10 can get u very good sound for earbuds, $50ish can get u midfi sound and $100 - 200 can get u TOTL sound for earbuds. IEMs on the other hand are more expensive relatively in the various budget/midfi/TOTL price brackets.
How is the FAAEAL Rosemary? Heard it is a bass monster.
