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Moving Forward With A “Hybrid” Approach
Real World Gear: In Ear Monitors
An expert view on
IEM and hearing
Enrolling in “IEM 101”
In my earpiece designs, I strive for the widest frequency response
possible, 20 Hz to 16 kHz (usable, as opposed to 20 dB down). Anyone
claiming response at 18 kHz (+/- 6 dB) with current earpiece technology
is not being truthful.
All Ultimate Ears earpieces are tuned with a FFT analyzer on the ear
simulator; these curves are posted on the web site for each model and
are available to our clients (personal curves) when requested. With
this information, the sound person can look at the curve and do equalization
adjustments, making the earpiece even more accurate.
I really believe in repeatable curves so the monitor engineer as well
as everyone on stage has the same basic reference frequency response.
GETTING IT SEALED
Low and mid frequencies are the easiest to reproduce in an armature
loaded earpiece. The earpiece is reproducing down to 20 Hz; what dictates
low-end response in the ear canal is how well the earpiece seals.
The real challenge lies in higher frequencies, above 8 kHz. In the brand
new UE10 earpiece, I’ve reworked the high-frequency circuit and
used a lower impedance armature to get the earpiece to reproduce out
to 16 kHz (+/- 6 dB). Some EQ is still needed to make it perfectly accurate.
But in prior earpieces no matter how much EQ is boosted at 14 kHz to
16 kHz, the earpiece just will not respond.
Also by not having to boost the highs in the overall mix, you end up
with much more transmitter headroom. Of all the models on the market
today, we believe the UE10 has the widest frequency response in an armature
earpiece, 20 Hz to 16 kHz (+/- 6 dB).
OPEN DESIGN
By using different materials and magnets, a diaphragm earpiece
can have good bass response and headroom. It needs an average seal to
reproduce good low frequencies.
Diaphragm designs are very open, typically providing only 5 dB to 10
dB of isolation. This problem comes from radically different frequency
responses from the speaker when its put into differently sized ear molds.
Everything – size of the ear, length of the canal size of vent
– affects the curve. Also the diaphragm, when enclosed in an ear
mold, has a deficiency in the mid and high frequencies.
Even though an armature-based earpiece can reproduce 20 Hz, only 60
Hz and above is really heard. Low-end headroom is still an issue. Single
armature designs, in any earpiece, still do not have the ability to
reproduce a bass heavy mix without some distortion.
Therefore, I believe two low-frequency armatures are needed to reproduce
a solid, distortion-free live mix. It’s much the same concept
as a live PA, where often, more components are needed to adequately
produce low-end response in relation to mid- and high-frequency response.
Perhaps in the future there will be a single armature that can take
the low-end load.
 The UE-10 with triple drivers. |
A NEW HYBRID
By combining a single diaphragm with a high-frequency armature and the
circuitry from our model UE-10, I’ve been able to correct the
deficiencies of the dynamic and armature to create a new earpiece called
the Hybrid. In order to have a repeatable response curve, the size of
the low enclosure, tube length and port size were all evaluated and
controlled.
Trust me, this is easier said than done. I’d love to be able to
use two drivers for the lows, but an average-sized ear won’t allow
it. As a result, the new Hybrid is an open earpiece with minimal isolation
and plenty of bass response.
Real World Gear: In Ear Monitors
An expert view on IEM and hearing
Enrolling in “IEM 101”
Jerry Harvey is a veteran monitor engineer and director of R &
D for Ultimate Ears. Reach him at jharvey@ultimateears.com.
