Koss KDX 300 Gold In-Ear Headphones (Playback 42)

Earphones and in-ear monitors
Koss KDX300
Koss KDX 300 Gold In-Ear Headphones (Playback 42)

The KDX family of sound isolating in-ear headphones represents the mid-section of Koss’ in-ear line-up, with the KDX 300 Gold ($99.99) slotting in as the top model within the KDX group. The Gold models use precision-made dynamic drivers (as do the lower-priced KDX Silver model), and feature earpieces that are finished in a soft matte gold color and appear to be molded from a polymer material, where Koss’ somewhat less expensive KDX Silver models (also reviewed in Playback) feature earpieces made of solid, polished aluminum. The Gold earpieces also incorporate what appear to be two tiny, outward facing vents or ports (though Koss product information makes no mention of these). As we’ll see in a moment, the KDX 300 Gold ‘phones not only look different from their Silver siblings, but sound different as well.


If you study Koss’ press releases on the KDX 300 Gold and KDX 200 Silver, you’ll have to scan very carefully before you spot any real differences, though there are a few. Specifically, Koss says the Gold model offers wider frequency response (10 Hz – 20 kHz for the Gold vs. 15 Hz – 20 kHz for the Silver), higher sensitivity (102 dB SPL/1 mW for the Gold vs. 100 dB SPL/1 mW for the Silver), and substantially reduced distortion (< 0.3% for the Gold vs. < 1.0% for the Silver).

For both models, Koss’ stated intent was to produce affordable in-ear headphones that offered a good measure of isolation from external noise sources while delivering “exceptionally rich audio” sound quality that is “crisp and clear.” Also for both models, Koss also draws a distinction between conventional, loose-fitting earbuds (the kind supplied with iPods and most other digital music players) and its KDX-series in-ear headphones, which aim to achieve a good airtight seal between the headphone’s eartips the wearer’s ear canals and thus to become, “acoustically coupled with the eardrum for almost perfect translation to the ear.”

Design highlights and product accessories include the following:

• Computer optimized dynamic (not balanced armature-type) “micro drivers” said to offer, “the quality usually found in larger, full-size stereophones.”
• Molded polymer earpiece housings with what appear to be miniature outward-facing vents or ports.
• Three sizes of silicone eartips (which Koss calls “ear cushions”).
• Signal cables with padded, patterned fabric sheathes that look much like miniature versions of the fabric wraps commonly seen on high-end audio interconnect cables and that are said to be “resistant to kinks and tangles.”
• A leatherette carrying case with spring-clasp closure.
• The KDX 300 Gold ‘phones are, significantly, covered by Koss’ “No Questions Asked Lifetime Warranty.”


I found the KDX 300 Gold earpieces made the headphone easy to handle and to insert. I particularly appreciated the firm but still flexible rubber signal cord strain reliefs that Koss provided—features that could prove to be real lifesavers (or cable savers) should active users inadvertently tug too vigorously on the signal cords (something that most of us know better than to do, but that can happen from time to time if we’re distracted or in a hurry).

The silicone eartips provided a good, though not class-leading, measure of sound isolation and were comfortable to wear. While some might wish for more than three eartip sizes, others will be relieved that Koss has narrowed down their choices to just three.

Contrary to Koss’ claims, I found the fabric wrapped cables were at least somewhat prone to kinks and tangles, although the Gold’s cable work better than the Silvers in this respect since they are a smidgeon thicker and thus more resistant to sharp bends or kinks.

One small criticism I would offer is that the KDX 300 Gold’s’ Left/Right earpiece markings are presented in the form of the micro-miniature letters “L” and “R” imprinted on the appropriate earpieces’ signal cable strain reliefs. Honestly, a guy could go blind trying to read those tiny little letters (bifocal wearers beware).


I found the tonal balance of the KDX 300 Gold headphones to be notably smooth, and more neutral and accurate overall than is the norm in this price class, with an emphasis on sonic warmth and richness. That said I could also see how some listeners might find the sound of the Golds almost too dark or subdued.

The KDX Gold’s’ superior tonal balance hinges, first, on the fact that the ‘phones produce bass that not only sounds taut and offers good pitch definition, but that also has plenty of foundational weight and punch (something the Silvers don’t do nearly as well). In turn, the Gold’s provide midrange that is at once revealing, yet also smooth and well balanced—never overly prominent or pushed forward in the mix (as is the case with the Silvers). As a result, the Gold’s midrange is more evenly matched with its bass and highs. While some might miss the Silver’s arguably more vivid and evocative midrange-forward sound, others will appreciate the Gold’s greater warmth, smoother sound, and generally more neutral balance. The only complaint, again, might be that the Gold’s more laid-back mids tend to give them a more “distant” and less “up-close-and-personal” presentation.

At the treble end of the audio spectrum the KDX 300 Gold’s offer good though perhaps not class-leading measures of high frequency definition and focus. Interestingly, some listeners initially perceive the Gold’s highs to sound a little recessed, and least relative to the KDX Silvers. I think this perception arises because the Silver’s region of midrange prominence extends up pretty high, making the Silvers seem brighter and more defined at first. But if you listen to the Golds’ highs in isolation (on delicate high percussion instruments, for example) you’ll discover they are in fact surprisingly clear and refined.

Overall, the KDX 300 Golds sound similar to, but a bit darker and just a touch less transparent than one of the strongest competitors in this class: namely, the NuForce NE-700X. Compared to the NuForce, the KDX Silvers sound noticeably more midrange-forward, with significantly less powerful bass.

To learn how the sonic characteristics I’ve sketched out above play out on real-world music, it may be instructive to describe what happened when I played two good recording through the Golds—recordings that took full advantage of the headphone’s balanced, full-range sound.

First up is “If You Love Me Like You Say” from blues guitarist Debbie Davies’ album Holdin’ Court (Little Dipper). This track features Ms. Davies playing an aggressively howling Fender Stratocaster guitar while supported by a razor-sharp, hard driving, and punchy-as-all-get-out rhythm section. The Gold’s did a beautiful job with the midrange utterances of the Strat, showing how its sustained notes often expand into a full on “howl” or “cry.” Similarly, the Gold’s powerful low-end captured the almost locomotive-like propulsive drive of the electric bass and the deep, thunderclap-like smack of the kick drum-- qualities that, with some competing earphones, tend to get lost in translation. On cymbals and the very upper end of the Strat’s voice, the Gold’s sound perhaps a little too subdued, but not badly so.

Next, let’s consider “So Sorry” from Feist’s The Reminder (Cherrytree/Interscope). On this song, where Feist’s vocals are for the most part supported only by an acoustic bass and guitar, plus occasional keyboard passages, the inherent smoothness of the Golds really came into its own. Feist’s voice is an interesting one, in that it rides right on that fair/foul line between sounding breathy, intricate, and expressive on one hand, yet can, on the other hand, sound occasionally brittle, glassy, and edgy—and thus become off-putting. On “So Sorry”, however, the Gold’s’ inherent smoothness enabled them to reveal the beauty and mystery that characterize Feist’s vocals at their best, while minimizing any tendency toward roughness, edginess, or glare. The acoustic bass sounded great, too, in large part because the KDX 300 Gold’s superior mid-bass weight, which give the sound of the bass while giving it vital body and depth.


Consider this product if: you want a well-made and sensibly priced in-ear headphone that offer quite well balanced sound and a good balance of sonic sophistication, smoothness, and refinement from top to bottom. While not necessarily a spectacular performer in any one area, the Gold is one of those ‘phones that wins you over by doing most things well (its sonic sins are mostly those of omission).

Look further if: you want a headphone that draws you into the music through a more vivid and intense midrange-forward sound (if these are your tastes, you might prefer Koss’ slightly less expensive KDX 200 Silver model).

 Ratings (relative to comparably-priced competition):

• Tonal Balance: 8.5
• Frequency Extremes: 9 (bass)/8.5 (treble)
• Clarity: 8.5
• Dynamics: 8
• Comfort/Fit: 9
• Sensitivity: 8
• Value: 8.5

Summing Up: Koss’ KDX 300 Gold in-ear headphone is a solid offering in this highly competitive price class. It wins hearts and minds not so much by doing any one thing stupendously well, but rather by covering most important performance bases at a very high level. In particular, the Golds will appeal to listeners who value sonic warmth, richness, and a smooth, refined and well-balanced sound.


Koss KDX 300 Gold Headphones
Accessories: 3 sizes of silicone ear tips, carrying pouch
Frequency response: 10Hz – 20kHz
Weight: 20 grams?
Sensitivity: 102 dB SP/1 mW
Distortion: <0.3%
Impedance: 8 ohms
Warranty: Limited Lifetime Warranty
Price: $99.99

(800) USA-KOSS

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