Headphone Reviews

Koss BT540i ($199)
Looking very much like their ProDJ100, the Koss BT540i is...well, not very stylish. Val Kolton of V-Moda with his "no circles or plastic" mantra would cringe. Circular ear capsules, circular pads, and, but for the headband sliders and a few bits here or there, plastic and pleather everywhere. Yeah, this is a very plain looking headphone.

Earpieces rotate flat for storage in the included hard-shell case, but they can also folded inward to become quite compact should you want to do without the somewhat bulky travel case.

The other odd thing about the mechanical design is that when you spread the earpads apart to put the BT540i on your head, the headband wants flex around and rotate the earcups askew. It's hard to describe in words, but it takes a bit of getting used to before you can get them on your head straight.

Other than that one oddity, the BT540i is light and quite comfortable on your head, in fact probably second only to the Sony MDR-1RBT in comfort.

Sound quality is a bit of a mixed bag; overall balance is fairly good but a bit rough. Bass is present, though a bit loose sounding and modestly emphasized, but the upper-bass/low-mids are also a bit too emphatic giving the BT540i a slightly thick sound. Central mids to low-treble response is just about spot on, but a suckout in the mid treble and slightly overemphasized upper-treble lead to a papery and sometimes harsh nature up top. Sound on the wire in passive mode is pretty much the same as when operated wirelessly.

For me, I enjoyed the sound of the BT540i at lower volume levels, but as the volume rose, so did the harshness and bass bloat. If you're listening a modest levels, these may be the best of the $199 cans in this group. If you listen fairly loud, I'd stay away from them.

Measurements

Raw frequency response plots show a headphone that seals relaiably and is relatively insensitive to placement changes on the head. Compensated plots show a somewhat overemphatic bass boost (maybe 3dB more than I'd like to see), and the boost extending to far into the mids (I like to see the bass at baseline by 120Hz). The rise in the raw plots starting at 600Hz and rising 3.5kHz is just about perfect in my experience, but the immediately following 15dB fall is far to fast, and can be seen in the compensated plots downward notch at 5kHz. Upper-treble above 10kHz remains flat, but should probably slowly roll-off for proper response. Add to these treble FR issues the significantly ringing 300Hz square wave initial transient response and you wind up with the idea that these cans may have some trouble up top...and, in listening, they do.

30Hz square wave is moderately swaybacked and going out of phase but shows plenty of bass energy. Coupled with significant measured distortion down low would lead me to believe the BT540i likely exhibits some difficulty delivering a tight, punchy bass.

300Hz square wave shows an initial spike that does not exceed the height of the following waveform, and significant ringing after the leading transient edge. I've seen quite a few headphones that look like this and have found that it often doesn't damage the sound much (HD 650, DT 880, Focal Spirit Classic), and when it does it causes a papery or artificial sounding treble (Monster Beats Pro, Beats Mixr, Klipsch Image One, V-Moda XS).

THD+noise shows low distortion in mid and treble ranges, but is significantly elevated in the low-mids and below indicating troubles in the bass.

Isolation is good for a mobile headphone.