--- In "tk7859" <> wrote:
>
> Hello Rob and the Group
>
> Many thanks for your analyses. They have certainly got my grey matter
> stirring.
>
> The "typical frequency response curve" supplied on the 35-0192 data
> sheet does, indeed, show a rise to +8db at 5k, followed by a rapid
> fall to -3dB at about 12k. It seems my capsules are to spec and one
> gets what one pays for (=A30.35p :-)
Having written this I decided to have a look at the Rapid 35-0190 and
Panasonic WM-61a spec sheets.
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/SpecComp.jpg
Clearly the Panasonic capsules have, on paper, a smoother and more
extended response curve. I began to wonder what a Panasonic triplet
would sound like. So, I just had to make one. Luckily, I had seven
Panasonic capsules availabl with leads already soldered on. I sorted
and matched the capsules so that each triplet when wired up in
parallel had almost the same DC resistance. I then removed the Rapid
capsules from the stripboard of an already made up set of triplets and
replaced them with the Panasonic capsules.
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/replacingcapsules.JPG
Shows this process. The new triplets were then mounted on my wooden
barrier.
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/mountedwm61s.JPG
You will note the very long leads fastening the capsules to the
stripboard. I did not shorten them because if the experiment did not
work I wanted to reclaim the capsules (the Panasonics are nearly 10
times the price of the Rapids). I admit to being a bit worried about
the long length of unshielded wires picking up interference. Also
note the very close mounting of the capsules to the surface of the
barrier and each other.
I decided to test the performance of the Panasonic triplets barrier
against the Rapid triplets mounted in my lightweight barrier.
Previous tests showed the different barrier construction did not
affect sound quality when both were equipped with the Rapids. I first
ran a
tictoc test and made recordings with the Panasonics and the Rapids at
the same time. I set the clock up at the apex of a pyramid with the
two barriers at the ends of the base. The mics were about 3 ft. apart
and about 5ft. from the clock. I used two MZ-NH1 minidisc recorders
set to HiMD, mic sensitivity high, manual recording volume set to 30.
A 10 second snippet of the Panasonic recording and a the same 10
seconds from the Rapid recording have been joined together and can be
found here - the Panasonic goes first
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/10secpanrapmp3.mp3
It sounds like the Rapid is slightly louder. However if the wave
trace is viewed the tic and toc peaks are the same amplitude for the
different capsules. Looking at the wave trace it is seen that one of
the stereo channels, in both
Panasonic and Rapid is louder than the other - but not the same one.
I am sure this is due to the effect of the barriers being faced
inwards a little to point at the centre of the clock.
The RightMark spectrum analyses show this effect in so far as the
right channel of the Panasonic is loudest at -60dB and the left
channel of the Rapid is the loudest, also at -60dB. So the tics and
tocs seem to have been recorded at the same amplitude. The Rapid's
apparent louder sound is due to noise lower down the frequency
spectrum. The Panasonic shows a flatter, more extended frequency
response.
The Panasonic RightMark printout is here
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/panspectrum10sec.png
and that of the Rapid is here
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/rapspectrum10sec.png
The next test comparing the two barrier mics was an early morning
ambience recording on my back stoep. Again two MZ-NH1s were used set
up as before but with recording volume reduced to 22. Although there
was no wind and therefore no tree or surf noise several of my
neighbours central heating boilers were in full song. The same four
minutes of recording are here for the Panasonic
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/pan4minmp3.mp3
and here for the Rapid
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/rapid4minmp3.mp3
You will note that about half way through one of the boilers shuts
off, but about 50seconds later another starts up. A much quieter
boiler seems to continue all the way through. I have joined together
10 seconds of the Panasonic's quieter period to the same 10 seconds
from the rapid recording. Again the panasonic goes first
http://ad2004.hku.nl/naturesound/TomR/rapidVpanasonic/10secpanrapmp3.mp3
Well, the the cost of the Panasonic Triplet Barrier is $30 more
expensive than the Rapid equipped barrier. Is it worth it?
I'm voting with my wallet - I ordered some more Panasonic WM-61s from
a UK dealer this morning.
Cheers
Tom Robinson
|
