Earlier this week, Mark and Jason Krywko from Sleek Audio paid a visit to my office to chat, and to let me hear their upcoming SA6 in-ear monitor. A father and son team with years of experience in the hearing aid business, they have spent the last few years genuinely paying close attention to the community at Head-Fi.org, and set out to create a product that addressed what they saw as a fundamental need based on their observations: a headphone (in this case, an in-ear monitor) that could be easily user-customized to accommodate the widely varying sonic preferences of listeners and/or the variations in sonic character of different gear, and to do so mechanically/acoustically (as opposed to using electronic equalization).
The ability to do this is something I've always wanted to see in a headphone--mechanical/acoustic equalization. With loudspeakers, audiophiles regularly adjust for sonic preferences by adjusting loudspeaker placement--moving speakers closer to (or further away) from walls and corners can dramatically affect bass performance; and toeing-in speakers can be used to adjust treble response. Even with some full-sized headphones, varying headphone placement over the ears can be used to some degree to adjust headphone frequency response (but I'd still like to see a full-sized audiophile headphone that provides purpose-built acoustic/mechanical sound tailoring). But with IEMs, it's pretty much a zero-sum game--either they're inserted correctly or they're not (there is some tweaking that can be done with the use of different tip types, but not with the level of control or predictability that the Krywkos were obviously after).
Upon arriving at my office, the Krywkows unfurled some frequency response measurement sheets (with accompanying narrative) to show me just what effects the interchanging of the various sonics-adjusting parts have. It was very clear to me that this father-son pair was very serious about the precision of their methods and designs, with respect to the goal of predictable frequency response adjustments through the use of interchangeable pieces. Specifically, the SA6 comes with three different "bass ports," and three different "treble tubes" (for each of the two earpieces, of course). (For simplicity’s sake, let’s just call each of the three variations of bass ports and treble tubes minus, flat, and plus.) The use of the term “bass port” might suggest that the SA6 isn’t sealed, but it is--if I understood the Krywkos correctly, the different bass ports simply change the internal volume of the body (and thus the bass response); but the SA6, regardless of which bass port you use, remains sealed, and you can expect isolation from ambient noise to be competitive with other universal-fit IEMs. The treble tubes adjust treble response through both filtering and tube diameter (again, if I understood their explanations correctly). NOTE: The cable is also removable, using proprietary connectors that allow the cable to turn 360-degrees at each earpiece (and will probably also mean different cable-length choices at some point, if not from the outset).
All three of us listened to the SA6 prototype through my Tomahawk, with both Mark and Jason grinning broadly upon hearing what a good portable amp could do for their SA6. I was very impressed with this $249 IEM, and the way it could be tailored. During the visit, I kept the flat bass port in, but tried the flat and plus treble tubes, and the plus very noticeably increased the treble energy, changing the entire character of the SA6. I have since played with all the various pieces, and the various combinations make for a changeling of an IEM--their system works. So far, in early listening, the plus bass port is a little too big and loose for me, the flat being the best combination of control, detail and extension. And, for a single-driver IEM, there is significant bass extension here--if you’re thinking single-driver means Etymotic-type bass quantity, you’re only right when you put in the minus bass port.
I’ll say more about the SA6 in the headphone/earphone forum after more time with the SA6 prototype I currently have. We also recorded a brief interview segment with the Krywkos while they were in the office, using the HHB FlashMic, so listen for that in Episode 005 of the Head-Fi Podcast, which should be released soon.