Hallo Martin,
ja mit "saubere Richtcharakteristik" war ein unverzerrtes omni-Pattern gemeint.
Aber wie gesagt, ist das bei hohen Frequenzen bei meiner Anwendung nicht ganz so kritisch.
Zu den Sennheiser 4-211 hab' ich leider immer noch kein Datenblatt gefunden, nur zwei Kommentare im Internet unter
http://www.solorb.com/dat-heads/digests/V3.400/D490und
http://www.solorb.com/dat-heads/digests/V3.700/D767**********************
Sennheiser KE 4-211-2 mic capsules
(used with Etymotic Research earplugs, for binaural recordings of music)
$140 new, within the last year)
Pickup pattern(s): omni-directional
Stealthability? Yes. When fitted in the foam earmolds designed by
Etymotic Research, they fit just inside the ear canal.
Best features: 1. They are "much" better as far as frequency response,
than the other stealth quasi-binaural mics that are sold for this purpose,
i.e., Core, Sonic Studios, etc. If "faithful" reproduction (compared to
the original performance) is deemed important, these mic capsules have no
peers (for the money; a Bruel & Kjaer model DPA 4060 would beat them but
the price is around $1,500!!).
Worst features: The mic capsules require someone to build a power supply
for them (either unbalanced or balanced). When sold, these mic capsules
are in a "raw" configuration. Black Audio Devices can build either of
these for potential customers.
Recommend to others? Without hesitation. For the money, these mics
can't be beat for binaural recordings.
**********************
I found an electret capsule that made my dreams come true. The
Sennheiser KE 4- 211-2. It's an omni with a diameter of only 4.75 mm
(0.187 in). Therefore the microphone dimensions will have very little
influence on the frequency response, even if I place it very near to
the sound source.
I glued it to one end of a 6mm (0.24 in) metal tube (by means of
epoxy. Be careful: other glues may damage the diaphragm!) which is 50
cm (19.7 in) long in order to eliminate reflections from the tripod. I
grinded the end of the tube that points to the capsule to have it
slightly decrease it's diameter until it reaches the one of the
capsule. The other end of the tube fits well into the cable outlet of
an XLR connector.
I made two of these mics and placed them one after another in front of
a KEF dome tweeter which has a very flat frequency response. Then I
measured the freq. resp. by means of pink noise in the 3.15 to 20 kHz
range. Result: Flat to within +/- 0.45 dB. The differences between
the two samples I've got were within 0.5 dB, mostly due to different
output level.
I mounted them at 90 degrees to the front of the speaker and found
them to be the omnis I expected. No significant difference to 0
degrees.
The bass freq. resp. is not as good: Sennheiser rates -2 dB at 40 Hz
and I didn't check that yet because it's no easy task to maesure that
low.
Now, before you believe me to be gone crazy, please be patient for
some further lines.
The following ratings according to Sennheiser data sheet:
Sensitivity: 10mV / Pa +/- 2.5 dB
Output impedance: app. 1.5 kOhms
Equivalent self noise: app. 36dB
Supply voltage: up to 15V
No specs on max SPL and distortion. And I haven't heard them yet
(have to build my preamp first).
Price: Deutsche Mark 50 incl. 15% VAT for each unit (app. $30)
Attention: Unfortunately there are several variants of this capsule
which are all labelled 'KE 4- 211'. You have to make sure that you get
the KE 4- 211*-2* because all other capsules, albeit looking the same
are much worse. To make sure you get the right one, I recommend not to
buy them in an electronic store 'round the corner', but to ask your
Sennheiser Industry sales representative for a distributor. These
capsules do not belong to the Sennheiser standard microphone program
and are sold by the *industry* division of Sennheiser. Therefore ask
for the industry sales representative.
**********************
Bei ELV steht leider nichts davon da, ob es sich nun um die 4-211-* oder die besseren 4-211-2 Kapseln handelt. Ausserdem verwirren mir die Preisangaben in o.g. Kommentaren etwas ($140 oder DM50 verglichen mit EU35 wie bei ELV? Fuer die "einfachen" 4-211 ohen "2" hinten am Namen oder die 4-211-4?)
Schwieriger wird's aber anscheinend noch, in dieser Preisklasse differentielle Kapseln (fig.of 8) zu finden. Noch schwieriger wahrscheinlich, differntielle Kapseln, die zur Sennheiser 4-211 passen...
viele Gruesse,
fe
