Summary:
The MH750/755 variants having such a long history have also been investigated by other hardworking mates. I'm deeply appreciative of their advice and humbly give thanks to them too..and many others not named with apologies, those who I would greatly mention are
@crinacle @Slater @TheVortex @axhng @eqsOne @Nuclear Reactor @ClieOS @mochill @aspire5550 and finally
@Sead (Member of the Trade: Sony Mobile)
Just again to highlight.. Sony's OEM ( They designed, engineered, and make the prototypes but contract out to others for mass mfg) has 2 iterations of their drivers (pop it open yourself, only takes less than 2 mins with a thick pin ) from 2012-2013/4 (13WK-XX) -Off-centered oval vent & their newer 2015/6/7/8/9 (15WK XX onwards) with centered round vent and they do share almost identical sound signatures except the newer versions has a slightly elevated Mid/Sub Bass,
This was also agreed upon and mentioned by
@TheVortex &
@aspire5550 https://www.head-fi.org/threads/chinese-asian-brand-iem-info-thread.820747/post-14705306, as I believe Sony had to work with that, due to different factory contracts, product improvements and cost reductions thru the years, but are very strict on their preferred sound signatures to be as close to their prototype as possible.
How to Find/Buy a unit Today :
(They are getting very rare due to the lack of mass production )
Xperia Phones are Bundled with the MH750 , TYPE: AG-0500/AG-0501 (Black/White) , not MH755 (Shorter cable without microphone)
It's practically impossible now to get the older off-center air vent MH755/750 TYPE: AG-050X version made in 2012/13/14 anymore usually with MFG dates 13WKXX - 2013 Week XX. & 14WKXX - 2014 Week XX
MH750/MH755, TYPE: AG-0500/0501/0502/0506 , Mfg 2015-2019 (Center air vent) , can still be purchased from limited sellers, of course, may also be bought together with the Sony Bluetooth Receiver and recently also spotted the 2019 standalone MH750 Sony retail package
There are also reports of the newer MH755 retail packed with Bluetooth with a Straight 3.5 mm jack instead of a L-Jack and discontinued usage of the CE tagging with Product details on the cable for MFG 2017-2019
Did an in-depth 3 different Types and spent 1-week doing A/B/C testing so you don't have to :
1. MH755 AG-503 - MFG 2013 13WK27 - 2013 Week 27
2. MH750 AG-501 - MFG 2017 17WK42 - 2017 Week 42
3. MH750 AG-500 - MFG 2015 15WK52 - 2015 Week 52
Sony has another new variant mfg in 2019/20, with the straight 3.5mm Jack but since I don't own it or able to buy it ..I'm sorry I will not be able to comment on the sound signatures.
Below an image of the MH750 bundled with the Sony Xperia XZ2 Phone MFG 2017, notice it no longer has any CE markings or labels on the cable
The side vent that started all the confusion on the Internet with the MH755 VS MH750:
TYPE: AG-0503-MH755 (Mfg:2013) AG-0500/1-MH750 (Mfg:2014)
The 1 to 1, 100% Identical off-centered air vent MFG 2013-MH755 & MFG 2014-MH750 whereby the MH750 is super rare as you can't just buy them from any online stores as they are bundled only with Xperia Phones thus why
@crinacle made an incorrect assessment in 2019 review and comparison of MH755 (MFG 2013, Side Vent) vs MH750 (MFG 2017, Centre Vent) as they are 2 different hardware variants from different manufacturing periods back then.
The centered air vent, MH 750/755 has various TYPE: AG-050X versions.
This is how a fake MH750/755 driver looks like, without the 2 small eyelets, also most likely not secured or glued to the shell, thus in some cases, users have complained of a loose driver when the shells are shaken.
Lord of The Vents ;
In relation to 2013/14 side vent and the later & current common center air vent drivers
In my earliest memory, the MH750 model appeared first before the MH755, via the Ericsson-Sony partnership in 2011/12.
And it shouldn't be a surprise as all Sony Corp Comparison Charts use MH750 naming and not MH755 as to Sony they are one and the same product when it came to comparing with other earphones.
Why the air venting system tech, pray tell? Well due to the small form factor of the MH series from Sony, the vent assist in their microstructures and offers superb bass performances and maintaining detailed clarity with the treble,
Thus why there are always 2 x solder dots to secure the driver/shell from vibrations in Sony IEM, dated as far from the beginning (see Image below of Sony Ericsson W800,MH700, etc IEMs), another awesome example is the microscopic MH1 IEM.
This tech alone shows why Sony is legendary and groundbreaking in audio fidelity even today!
A Myth-Busting Recap :
1. MH750/755 shares the same drivers
2. Only differences are the thin short or longer thicker cable with Mic variants
3. 2 different H/W variants verified through the years
2013/14 - Side Vent Drivers
2015-2020 - Newer Centre Vent Drivers
Both versions can be identified as genuine with Sony's trademarked 2 x Solder Dots
An Extremely rare side vent MH750 mfg 2014 taken from a Sony Xperia Z3-- Yes Side Vent Drivers are not exclusive to only the short cabled MH755..as Sony uses the same exact drivers with the MH750 too
Finale:
Good Luck to Everyone
Now go find this hidden Gem Fast as its getting Rarer (
Side Vent MH750/755 ) as we speak
Edit/ IMHO I actually prefer the newer centre vent variants MFG in 2015-2019 versions, due to its all-rounded MID/SUB Bass and less peaky treble signatures.