Inks traded his Etymotic Research HF5, in order to obtain this IEM, Rockit Sounds R-50, which popped out of nowhere. I've never heard about this manufacturer before, but it seems they reside close to San Francisco, California. I usually don't trust products made by random folks, but hey, I can still give some love to yet another Californian company.
Just like Brainwavz B2, R-50 is equipped with a pair of Knowles TWFK balanced armature drivers, tuned to be slightly warmer with less treble, according to the general public.
PRO: Considering TWFK drivers are used, R-50 is quite well balanced, retaining some resemblance to the diffuse-field reference; This is the first among TWFK-equipped IEMs. And the distortion has been further reduced at the frequency range, of which the human hearing is most sensitive.
CON: Just as expected, R-50's polarity is inverted. There is a harsh peak @ 10 kHz, but it is only audible when the IEM is fully inserted.
ON SECOND THOUGHT #2: Just like the other IEMs with TWFK drivers equipped, by adding a resistor in series, the mid-range gets boosted, while the treble level decreases. This under-damping scheme can further benefit from a shallow insertion, as shown on the right.
ON SECOND THOUGHT #3: By adding acoustic dampers to R-50's stem, users can further tweak the tonality. And of course, the tendency of acoustic damping is almost same as that of Brainwavz's B2. To my personal preference, "100 ohm resistor + gray dampers + shallow insertion" combination yields the optimal spectral balance.
I've analyzed 3 TWFK-based IEMs from different manufacturers, and Rockit Sounds R-50 is by far the best, due to much consideration put into circumstantial variables; A job well-done by Rockit Sounds.
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