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.