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Re: Wide Sound Stage Parabolic Reflector - Outdoor Test

Subject: Re: Wide Sound Stage Parabolic Reflector - Outdoor Test
From: "Rob Danielson" danielson_audio
Date: Tue Jan 22, 2008 10:09 pm ((PST))
At 1:33 AM +0000 1/23/08, tk7859 wrote:
>--- 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.
>A Google aerial photo of the situation, showing the position of the
>Parabolic/Barrier and the direction it was pointing is shown here
>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.
>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.
>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.
>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.
>Tom Robinson

  Hi Tom--
Shows promise.  Seems to be good hard left & hard right imaging now. 
I was trying to hear if there is an interaction between the mics at 
the focal location inside the dish and the side firing ones. On 
sample 2, it seems like an interaction would more likely occur when 
the geese are first arriving on the right, yet I think I'm hearing 
some phasing or doubling at the end of sample 2 when the geese are in 
the center. Not sure I'm hearing it correctly or how to explain it. 
One way to test localization is to record a repeatable sound at each 
of the clock positions from 7 o'clock to 5 o'clock.   A way to adjust 
the balance between the side and center mics might be useful, 
wouldn't it?   Rob D.


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