Introducing the CE1 - The World's Most Somethingist Headphone

General Information

Welcome to the CE1 tour!

CE1.jpg


I hope this will be a fun and useful extension of our project testing various couplers/human-ear simulators (https://www.head-fi.org/threads/ety...phone-for-your-ears-and-your-couplers.908512/). The CE1 is not a regular IEM - it's an IEM with a microphone in each earbud's nozzle. The goal is to get the CE1 into the hands - and ears - of as many head-fiers as possible in order to collect data on human-ear response. These measurements will be your contribution to science and should also be helpful to you as individuals, since we can then figure out how your ears differ from the various modern ear simulators, i.e., which coupler type your ears are the closest match to, and/or what corrections you might want to consider when comparing FR graphs made with various couplers.

If you've ever measured IEMs before, you can probably help us out. If you've never measured IEMs before, you're probably not going to be able to participate - sorry :frowning2: After much debate and testing, it looks like the only equipment suitable for this purpose is a phantom-powered XLR-input sound card that is either ruler-flat, or can be calibrated flat via a loopback. If you don't know what all that means, I'd respectfully ask you to sit this one out. I did try to create (via the left earbud mic) an option to measure via RTA software like the iOS AudioTools app, but came to the conclusion this just wasn't accurate enough for our purposes. So, for now, this tour is for folks with phantom-powered XLR-based sound cards. You don't need a coupler to participate, but you do need to know how to use ARTA, REW, etc.

The instructions below describe what comes in the kit and what you'd do with it. Each tour member would be expected to pay for shipping to the next destination and to be reasonably careful with the IEM. Each earbud will fit in either ear, so we have a tiny bit of redundancy, but the included mics likely make the CE1 a little more fragile than your average IEM. For sure, they're not designed to be taken to the gym or used in the pool.

Instructions

The CE1 is best worn over-ear. The earbuds themselves are tiny, so most people shouldn't have fit issues, but its cables are a little chunky as each earbud has braided silver litz wires both for the headphone drivers and its mic. Wearing over-ear helps achieve a proper seal with deeper insertion and also supports the weight of the cable, reducing microphonic noise (which is crucial for our measurements).

CE1_parts2.png


The following eartips are provided new in the kit (if you use any of these, please, please, please clean them with alcohol or Clorox wipes before sending them on to the next tour member):

Trinity Kombi tips (M, x2)
SpinFit Cp100 (M)
SpinFit Cp145 (M)
Sony Foam (S, M, L)

Choose the tips that fit you best - if you have other tips that work better for you than any of the above, feel free to use those. The most important thing is you'll want to get a perfect seal. In my experience, that's not as trivial as you might think and there's a range of fit where the IEM may feel like it's sealed and isolating, but there's still a tiny air gap. The only way to know for sure is to look at repeated measurements. Once you have a complete seal, the bass will not increase any further and any subsequent measurements with an equivalently-perfect seal should be very consistent. (More so than with an ear simulator, because the outer ear cartilage provides a natural stop for the IEM.) We only want to record and save measurements made with a perfect seal, because that's what we're comparing against in our couplers. Please discard any measurements where it's obvious the bass is rolling off (relative to your other measurements) and expect this to need some care and attention; it's not as easy as just sticking an IEM in a coupler. Please also record which type/size of eartip you used.

The headphone itself has a 2.5 mm balanced termination, but for those that don't have a 2.5 mm balanced source, an Eidolic 2.5 mm balanced -> 3.5 mm single-ended adapter is included. The CE1's frequency response isn't particularly sensitive to source output impedance, so pretty much any source should work.

There are two other 3.5 mm plugs coming from the earbuds - these are from the earphone mics. These plugs each have a little plastic shield over them as a reminder that nothing should get plugged into these except the 3.5 mm TRRS adapter or the Rode VXLR+ adapter. In theory either mic can use either adapter, but the left mic is better suited to the TRRS adapter, and the right mic more suitable for the Rode adapter. I strongly recommend using only sound cards with XLR input supporting 48 V phantom power and therefore to use ONLY the right mic/earbud and simply move the right earbud into your left ear when measuring your left ear. (As mentioned above, I suggest ignoring the TRRS adapter/left-earbud mic for now due to the poor-quality sound cards in iOS and Android devices. Unless you're very clever and very creative, you're unlikely to be able to record an accurate FR down to the sub-bass using RTA methods like AudioTool(s). Most of these Android and iOS hardware devices have high-pass filters built in by default, and you can't disable them, which causes various levels of roll-off in the bass, making meaningful measurement comparisons a bit of a crapshoot. The TRRS cable and left earbud mic might be useful for comparisons against your own coupler, but I'd request not sending data recorded from the left mic or via RTA for now.)

Ideally, you'll want to first confirm that you can achieve a flat FR via loopback from your sound card output->input without the CE1 in the chain. Then plug the CE1 headphone TRS into your source, plug the right mic into the Rode adapter, plug the Rode adapter into your sound card and turn on phantom power at the XLR input. While measuring your ears, I'd recommend sitting completely still and not moving your head or jaw at all. Measurements will be noisy - if you look at the trace, you may even be able to see your heat beat registering vibrations. Higher volumes will help improve SNR, but be careful with your ears. Most of the measurements we've done in real ears haven't exceeded 85 dB @ 500 Hz. I prefer to reduce the variance by taking averages over a good number of samples. Once you're finished measuring, please pm me your REW, ARTA or ASCII files (documented to identify separate individuals and what eartips were used in each case).

The goal here isn't to review the CE1 but rather to collect as many human subject measurements as possible. So feel free to also measure friends, family, neighbors, etc. (We will anonymize any measurement data received/published.) Note that the internal microphone measurements won't match those from a coupler, because the CE1's mics aren't wide-band, and where the mics sit in the nozzles subjects them to shorter-wavelength resonances that won't be experienced by the coupler mic. Larger wavelengths (i.e., lower frequencies) will be more consistent, but the objective here is only in comparing the deltas, i.e., to compare ear vs coupler response from the exact same (internal CE1) mic.

If anybody's interested and willing to help out with this little experiment, feel free to jump on the tour by replying below and we'll try to coordinate shipping sequence based on your location.

Acknowledgement: Big thanks to @earfonia for the help and suggestions on design and build of the CE1 :)

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