Ok, so I caved...Azla's reputation precedes them; couldn't pass up seeing what their TWS offering was capable of. Was already ordering a couple books from the 'Zon, so tossed these in as well. Should be "crystal" clear from the photo, but the size I rolled the dice on were Medium. They are also available in all the in-between sizes from SSS up to L (on MTMT as well, if Amazon ever runs out of stock). I believe the lack of larger sizing past this point would be a reflection of the Korean market; perhaps there's not much demand for anything larger.
Here they are pictured on the ADV M5 and they're honestly fantastic bedfellows. I was somewhat surprised to find their tip surface is a lot tackier than your typical silicone or foam tips, which I imagine is to help with grip inside your ear (which it does
insanely well), but the tradeoff is that it'll grip onto whatever dust/hair/lint is floating around the air (or in your ear) until you clean it back off. If this becomes a chronic problem, you could always lick your thumb/forefinger and just wipe the surface of the tip prior to insertion. As always, good ear hygiene is a must with
any TWS and can mitigate leaving "friends" on the eartip surface long-term.
Sound-wise, the M5 were already temperamental enough with tips as they really don't seem to like anything with a nozzle that protrudes too much. This is for two reasons:
1. The upper midrange begins to smear and become
very sibilant. Anything that produces a more horn-like shape does not suit the M5 well, including the EPro TW00, which up until this point were my favorite tips
2. These fit inside the case more than easily. Due to the more rigid nature of the shroud, you do have to give the M5 a bit more of a tap when putting them in the case, but they will fit afterwards and do make contact with the charging pins. Same goes for the CX400BT and Melomania Touch, which I also tested for case compatibility.
And oh, what a difference in sound they make. Azla's full-size tips (the Sedna, not the XELASTEC) seem to perform a lot of cleanup for those TWS that have a slightly looser bass signature. In the case of the M5, which had a prominent, yet compartmentalized bass (not loose), it seemed to take the bass energy and give it more punch without sacrificing the overall intensity. Perhaps these are the tips the M5 were supposed to have all along, though might have been too expensive to include. The overall shape between the Azla Crystal TWS and ADV's flatter tips have a lot in common regarding shape and nozzle protrusion.
They even do fantastically with the CX400BT, which I have had a
beast of a time trying to find aftermarket tips that permitted a good seal, didn't completely mess up the midrange tonality, and even performs a little bit of a treble lift. Unfortunately, I find the CX400BT's treble tuning is already pretty rolled off and the Crystal can't perform miracles, but I do find things neutralize enough just from the tip swap to make these plenty enjoyable for vocal-dominant tracks. They did admirably with The Erised's
Desire EP, though I'll readily admit that the M5's extra bass weight (and added control, thanks to the tips) completely upstages the CX400BT on this sort of content:
Finally, I gave them a spin with the Melomania Touch. While they're
very temperamental inside the MT's case, the tradeoff with in-ear comfort more than make up for it. Overall change to sound signature is probably the least different over stock compared to any other TWS I've tried with the Crystal, though perhaps there's a slight boost in bass clarity, especially with the upright bass in Track 2 of the EP I linked above. In this case, that's not really a bad thing. If the stock bass signature was too much for you, though, I'm afraid the Crystal isn't going to fix that enough to make a difference.
All in all, I think the Senda Crystal are a fantastic alternative set of tips for the ADV M5 (and the only aftermarket tip I've been able to recommend for the M5 so far), a suitable alternative over the stock tips for the CX400BT, and a comfort/fit upgrade (just not a big sound quality one) for the MT. At their current price of $25 for two pairs, however, don't buy until you're absolutely confident in what size you need. Even I was apprehensive at ordering the Medium, but they seem to be the perfect fit in my ears.