Hello All
I was not too sure where to post this message. Logically it belongs
on the "Micbuilders" Group, but then, there is an ongoing discussion
on th "Phonography" Group which is very pertinent to the subject.
However, my experiments with triple Rapid capsules have been mentioned
a couple of times recently on the "Naturerecordists" Group. This in
turn has caused a couple of e-mails requesting info on progress. I am
therefore posting this update here.
I have been quite pleased with the performance of my wooden, barrier
type, mounting of the stereo pair of triplet capsules. Because these
require a 9V battery supply to get them to work adequately (minidisc
PIP is not successful) I have used perforated board to mount the
capsules and the capacitor/resistor circuit. A logical next step was
to use the 35-0192 PCB mounting capsules rather than solder pad 35-0190s.
Theoretically the 35-0192s are identical to the 35-0190s - just a
different type of mounting. During my initial testing of 35-0192
triples I was surprised to see a 3dB drop in sensitivity compared to
35-0190 triples. I reasoned that this was due to the soft, camera
pouch style of mounting of the 35-0192s compared to the hard, wood
barrier mounting of the 35-0190s.
I therefore mounted the 35-0192 and 35-0190 triples to the same wood
mount and carried out "TicToc" tests. The "triplesamebarrier" photo
in the "Lightweight Barrier" album at
m("btinternet.com/my_photos","//uk.pg.photos.yahoo.com/ph/g0sbw");">http:
shows the barrier equipped with the two stereo mics.
The results of the test were interesting in so far as the PCB mounted
35-0192s were now slightly more sensitive than the solder mount
35-0190s. Detailed investigation of the mounting of the triples to
the wooden barrier showed the more sensitive triples to be about 0.5mm
closer to the wooden barrier; the gap being 0.5MM compared to 1.0mm.
The photo "mountinggap", in the same album above, unsuccessfully trys
to show the difference in gap.
These experiments allayed any fears about the PCB mount capsule being
inferior to the solder mounted variety. I was therefore free to
develop ideas for a more ergonomic barrier mic using the 35-0192s.
The main focus of my nature recording activities will be a local
saltmarsh. Access to this is only on via one and a half miles on
foot (forget your 4x4s - they'll sink without trace). The wooden
barrier weighs 2 lbs (990gms). It also requires a reasonable tripod
for a mounting (mine weighs 7lbs). This is cumbersome cosidering the
weight of the minidisc recorder.
I am an avid reader of Rob's student's activities via their blogs (any
chance of becoming a "distance learnig" student at senior citizan
rates?) and I saw the mention of cardboard barrier mountings. This
set me thinking; I had some "Corrux" corrugated plastic left over
after making my parabolic reflector, so why not use that - it is much
more durable than cardboard, and stiffer. I then thought that it
would be good to make a folding barrier for easy transporting in a
jacket pocket or similar. I had difficulty developing a suitable
folding geometry and started thinking about using the natural
attributes of the material i.e. the sockets formed by the corrugating
component.
The basic idea is shown in the "construction1" and "construction2"
photos in the above album
Thickish copper wire rightangles are pushed into the corrugations to
hold two pieces of corrux firmly together at the correct angle to each
other.
The "barriercomparison" photo shows the wooden barrier and the
assembled, collapsable, corrux barrier side by side.
The "components" photo shows the finished components of the
collapsable barrier laid out next to each other, and
The "packingsize" photo shows the components as they would be packed
for travel - just a little larger than three CD jewel boxes. It also
weighs 1lb less than the wooden version.
So how does the collapsable, corrux barrier perform compared to its
wooden companion? To my aged, inexperienced ears - just as well.
TicToc tests showed the collapseable to be, maybe, 1db more sensitive.
To try and assess how well it sounded versus the wooden barier I used
both rigs to record the playback of a HiFi test CD - the speakers were
the excellent BBC LS3 5a studio bookshelf monitors. A 30 second MP3
snippet of the recordings is given here (the first 15 seconds is the
corrux, collapsable and the second 15seconds is the wooden barrier).
m("btinternet.com/3ctm3wtm3_30sec.mp3","//uk.geocities.com/g0sbw");">http:
To my ears there is no difference. However a trace of the excerpt in
Audacity shows the corrux collapsable to be louder. Apparently
"corrux versus wood" is not an issue.
A four minute MP3 of a live recording using the corrux collapsable is at
m("btinternet.com/002-livetest1mp3.mp3","//uk.geocities.com/g0sbw");">http:
This was made on my back stoep at 9am today. Wind was 16mph (quite
the lowest for many days) but the faux fur busby managed to control it
reasonably well. There is a lot of noise of the wind in trees and
some noise of surf at the sea shore about a mile away at 2 o'clock. A
neighbour's bamboo wind chimes are at 8 o'clock some 60 ft. away and
a small birdbath fountain plays at 3 o'clock 25 ft. away. The
MZ-RH910 minidisc recorder was set to manual record, high sensitivity,
15 rec. volume.
Lessons learnt:
Corrux material/bent wire consrtuction works well - as good as one
inch thick lumber?
The gap between the capsule and the barrier is important - the smaller
the better.
Move away from the coast - we've had horrendous winds since mid November
Maybe a better way of using triplets is to go back to the solder pad
type, superglue thre capsules together in a vertical row, then
superglue the triplets direct to the face of the barrier i.e. have no
gap twixt capsule and barrier. Then use a conventional battery box to
power the capsules via the coax leads (talk about going full circle:-)
I trust the foregoing has been of interest to some and, maybe, useful
to a few. You are not going to get MKH clones (but for about $20
maximum you should not expect to). They do work though - quite well,
actually.
Cheers
Tom Robinson
BTW The original 35-0192 triplets are now being used in a disc filled
in my parabolic reflector. A photo of this disc is in the above
mentioned album. The "parabolic reflector" album at the above website
shows the construction of the reflector
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