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August 2009
Enjoy the Music.com Review Magazine
Sleek Audio CT6 Custom Earphones + Wireless Module
Best Audiohpile Products Of 2009 Blue Note AwardI love them to bits!
Review By Phil Gold


  I've reviewed some outstanding components over the years, some of them way up there in price, but nothing gives me greater pleasure than to discover a genuine audiophile bargain. Today I am happy to bring you an inexpensive yet remarkably flexible set of custom earphones the type that fits your ears and your ears only.

Sleek Audio CT6 Custom EarphonesYou pay a visit to your local audiologist (in my case Dr. Marshall Chasin of the Musicians' Clinics of Canada) who will take a set of impressions of your ear canals that you can send on to the custom earphone manufacturer of your choice. I've done this twice, first for the Ultimate Ears UE-10 Pro (click here), an expensive indulgence, and now for the more modestly priced Sleek CT6 customs. You're in and out in twenty minutes and it's time well spent. Remember to keep your jaw open for the best fit. No universal fit canal earphone can come close, and the perfect fit you can get from your own custom earphones mean they are very easy to insert, they feel comfortable for long stretches of time, and with their excellent seal they block out a great deal of external noise and provide amazingly solid bass.


What's Not To Like?

The first issue is that you're buying before trying. I guess that's why you read reviews.
Next, not every impression gives a perfect fit on the first try. I have a 100% success rate, and I put that down to the skill of Dr. Chasin and the two vendors I've dealt with, but if you have a problem, then the audiologist and the vendor will make things right for you. Actually I did run into a small problem this time which I forgot to mention. One earpiece is clear and the other smoky. As it happens, I like it this way because it's so much easier to tell which goes in which ear! Sleek Audio offered to make it right for me but I love it this way so I told them not to bother. Sleek offers a wide range of colors and finishes on their website 7 solid and 6 transparent colors for each of shell and top plate.
Some people are not comfortable with the feel of a canal earphone you should try a universal fit first they make disposable tips for testing. If you don't like the sensation, steer well clear.
The dirty secret ear wax. Canal earphones will need regular cleaning. The manufacturer provides a tool for the purpose. The design of the CT6 (with one wide opening) makes cleaning much easier than the UE-10Pro (with two smaller openings).
Custom fits cost considerably more than universal fit, over and above any charge for the audiologist's appointment (say around $50).
You can't resell them if you don't like them well you can try but who'd buy them?


The Ultimate Ears UE-10 Pros run around $900, while the Sleek are a much more affordable $349.99, or $449.99 with the wireless option as tested.


Taking A Closer Look
Sleek Audio CT6 Custom EarphonesSleek Audio's background as a manufacturer of custom hearing aids informs the design. This is no cheap knockoff but a serious attempt to bring high quality earphones to discerning audiophiles and regular head-bangers at something approaching mass market prices. Instead of expensive double or triple armature drivers, Sleek has developed in-house a single ultra-wide balanced armature tuned to your personal preference (at the time of ordering) in the custom mold. I asked them to give me the flattest response possible, while others may prefer a bit of bass emphasis or some other contour to suit their personal tastes or the application they have in mind. You can choose how far the mold extends into your ear canal (the longer the better they say), and where on the mold the female sockets should be placed. You can even have custom artwork if you like, but that's an extra cost. You can pick the cord color too, but it's a much thinner cord than the UE-10 Pro has, and terminates into a right angle molded plug. You can specify 4 or 5 foot I prefer a 3 foot length because I keep my iPod in my shirt pocket, but that's not an option yet. Since cords are the most vulnerable part of canal earphones, it's great they plug in so easily, ready for quick replacement.

But maybe what you want is to cut the cord entirely. In fact I'm listening to a Prokofiev Violin Concerto on the Sleeks as I write this, and I'm using the optional KLEER wireless module. Sleek claim CD quality, a 60' radius and a ten hour battery life, in a convenient and comfortable lightweight package.

Let us take a look at each of those claims in turn.

Wireless Quality: It is hard to test the CD quality claim, since you are not just listening to the effect of digitization, transmission and conversion back to analog. You also have to factor in the quality of the headphone amp included in your wireless receptor and compare that to the quality of the original analog output. I have to say I'm very impressed, especially given how small the package is. When you attach the device to an iPod there isn't a whole lot difference between wired and wireless sound. The wireless is somewhat less detailed, not so well pitched in the bass registers and not as clean in the treble, but it is vastly better than previous generations of wireless headphones, even expensive Sennheiser and AKG Hero models I've tried back in the day.

Wireless Range: These things don't fade in and out like older technology they are either on or off, and you won't be comfortable on the edge of their range, with the sound cutting in and out. In clear air I found I could go about 75 feet from the transmitter, but inside my house there are dead zones and live zones. You should be perfectly ok if you are in line of sight of the transmitter.

Battery Life: You've got two components to charge the compact boxy transmitter and the receiver. You plug them both at once into the supplied USB connector for a minimum of two hours and the battery life easily meets the advertised 10 hours. There are tiny on-off switches hidden under a protective cover on each device but I was advised just to leave them on they power down automatically when not in use for five minutes. They will hold their charge for about three months when the power switch is off, or for a week with the switch on. Unlike other wireless phones, you are not stuck if the battery runs down just plug them in using the cable.

Comfort and Convenience: Similar KLEER wireless technology is now found in the latest Sennheiser MX-W1 wireless phones, but the physical implementation is quite different at the receiving end. Sennheiser builds the receiver and amp into the earpieces, making them rather ungainly. Sleek gives you a separate lightweight elongated receiver (just 20g) with short cables extending from each end which plug into the earpieces. This receiver sits on the back of the neck. I didn't find this arrangement all that comfortable. It's ok when your head is facing forward but the cord tends to snag on your ears as you turn your head to one side. You can also dangle the receiver under your chin but that just looks odd! But this is the price for the wireless advantage and you can take it or leave it. The transmitter (12g) plugs into any mini-jack headphone output and adds minimally to the size of the iPod. One transmitter can support up to four receivers at once. It takes just seconds to switch back to a wired configuration, although I didn't get the knack of switching without removing the earpieces from my ears as some might.


Getting Down To The Listening Tests
Sleek Audio CT6 Custom EarphonesTo find out the true potential of these phones, I plugged them directly into a very high quality headphone amplifier the Graham Slee Solo which I connected straight to the superb EMM Labs CDSA SE CD/SACD player. I compared them directly with the Ultimate Ears UE-10Pro.

The Sleek phones performed splendidly. They show a very rapid response to the music and remain undistorted even at high volume levels. They have a warmer and somewhat shallower sound than the UE-10Pro, more open at the top and consistently musical. Strings are a little thin but brass is bright and realistic, piano warm and open. Bass weight, extension and articulation are very strong, close to the superb standards set by the UE-10Pro. Jazz and pop are their forte where they are more forgiving than many competitors and remarkably even over a very wide frequency range. They really excel when it comes to the human voice where their warmth is very welcome, but I would turn to the UE-10Pros for their higher ultimate resolution and stronger imaging abilities when listening to classical music. That being said, the Sleeks did such a splendid job with the difficult Shostakovich Piano Concertos and in Beethoven String Quartets, breathing life and energy into these masterworks, that any preference for the UE-10Pros must be explained in the following terms. The Sleeks are wonderful, but the UE-10Pro may be the best three figure headphone in the world.

I found the Sleeks very comfortable for long periods in wired mode. They do exhibit more microphonics as you jiggle the thin cord than the UE10-Pro with its much more substantial cord, but this is rarely a problem in practice unless you are exercising. I've been using them for my 40 minute walk to work every day. I find them a little more difficult to insert than the UE-10Pro since they are slightly smaller ad it's sometimes hard to find the right orientation. They seem to offer more isolation and lower sensitivity than the UE-10Pros but the differences here are minor.

In short, these are great canal phones and I love them to bits. I'd probably pass on the wireless option but that's a very personal decision and it doesn't cost a whole lot extra. Sleek has a winner here remember you heard it here first.




Sleek CT6



Sub-bass (10 Hz - 60 Hz)

Mid-bass (80 Hz - 200 Hz)

Midrange (200 Hz - 3,000 Hz)

High-frequencies (3,000 Hz on up)



Inner Resolution

Soundscape width front

Soundscape width rear


Fit and Finish

Self Noise

Value for the Money



Type: In ear monitors (IEM)
Frequency Response: 10 Hz to 17 kHz
Impedance: 50 Ohms
DC Resistance: 24 Ohms
Sensitivity: 110dB SPL/mW
Isolation: Up to 30dB
Input Connector: 1/8-inch stereo plug
Cable Length: 48 or 60 inches, removable
Travel case: Pelican carrying case - very durable and waterproof
Cleaning tool: Wax pick
Warranty: 1 year (30 day return for initial fit issues)
Price: $349.99 ($449.99 with Wireless Module)


Company Information
Sleek Audio
600 8th Ave West, 3rd Floor
Palmetto, FL 34221

Voice: (800) 777-7937
Fax: (941) 747-3573
E-mail: Info@sleek-audio.com














































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