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Wide Sound Stage Parabolic Reflector - Outdoor Test

Subject: Wide Sound Stage Parabolic Reflector - Outdoor Test
From: "tk7859" tk7859
Date: Tue Jan 22, 2008 5:33 pm ((PST))
--- In  "tk7859" <> wrote:

> After I have done an outdoors test with the current setup I will try
> repositioning the mics as you suggest.  Will also try mounting the
> front pair of triplets, again angled as you suggest, on the front of
> the circular disc which holds the focal point capsules.  this will
> reduce the reduce the gap between front and rear capsules to 4.5
> inches and make a simpler, neater assembly while still allowing the
> front triplets to be in front of the plane of the dish's rim.

Hello All

Since last Saturday we seem to have had non stop wind and rain.  I've
kept myself busy mounting the barrier triplets so that they face
directly away from each other.  I've also 75% completed a 10inch diam.
Jecklin type disc which will fit inside the parabolic reflector.  At
the focal point of the reflector two, disc mounted, stereo triplets
will face into the dish and at the outer end of the disc two more
stereo triplets will be mounted at 115degrees and about 5 inches apart. 

However, this afternoon the wind dropped and the sun was out so I
managed to do first outdoor tests of the parabolic with the barrier
attached and the sextuplet stereo pair (with the barrier triplets
opposing each other) powered by an 18V supply.

The following photo shows the positioning of the parabolic reflector
during the tests.  You can see it is on a garden stoep pointing over
nearby gardens, a small tidal estuary (the centre of which is about
quarter of a mile away), a spit of saltmarsh and, eventually, the open
sea which is three quarters of a mile away.  Directly in front of the
reflector is some open ground with small bushes, whereas to the left
and right at 45 degrees are some taller conifers.  Immediately to the
right, and just in front of the plane of the reflector, is a small
birdbath fed with a trickle of water.  Behind the reflector and at an
angle of 45 degrees to the plane of the reflector is the 20 ft. high,
55ft long wall of a house.

http://ad2004.hku.nl/naturesound/TomR/Wide%20Stage%20Parabolic/Test%20Ground.JPG

A Google aerial photo of the situation, showing the position of the
Parabolic/Barrier and the direction it was pointing is shown here

http://ad2004.hku.nl/naturesound/TomR/Wide%20Stage%20Parabolic/Direction%20of%20Reflector.jpg

Three samples from the resulting recordings follow.

The first 2 minute sample has local birds to the left and right, and
the bird bath water trickle to the right.  Gulls, curlews and geese, a
good distance away on the marsh, can be heard centre stage.  A central
heating boiler situated in a room directly behind the reflector can be
heard starting up.  I can also be heard walking toward the reflector
from right rear to just behind and to the left of the reflector to
switch off the minidisc.

http://ad2004.hku.nl/naturesound/TomR/Wide%20Stage%20Parabolic/002-ParBar%20B2mp3.mp3

The second sample (2 minutes) includes distant calls from the marsh,
some localised birds, and the arrival of some geese from the right
into the line of the parabolic reflector.

http://ad2004.hku.nl/naturesound/TomR/Wide%20Stage%20Parabolic/geese%20arrive2%20mp3.mp3

The final sample  (43 seconds) is mainly the geese after they had
settled down but there are some interesting splishes and splashes to
the right.  This is a blackbird using the bird bath.  At the end of
the sample the blackbird flies off from right to left across the front
of the reflector.

http://ad2004.hku.nl/naturesound/TomR/Wide%20Stage%20Parabolic/splishsplash%20mp3.mp3

My conclusion is that the tests show the parabolic/barrier combination
gives a wider stage than a parabolic on its own even though the stereo
definition is not very good.  I think further tests out on the
saltmarsh, away from buildings and neighbourhood noises, will be
useful.  The parabolic/Jecklin combo  also needs to be tested there. 
Unfortunately more rain and wind is forecast for several more days as
from tomorrow.

Cheers

Tom Robinson






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