--- In "tk7859" <> wrote:
> I had completely overlooked that the MX391 is, in fact, a Wl183 already m=
ounted on a very small boundary and does therefore might have some boundary=
effect benefit as is. I wonder by what amount the effect is increased by =
increasing the size of the boundary - to 5 1/2 inches square in my case?
>
> This thought raise a second question. Will my EM172 capsules perform in=
a similar way to the MX391s if I reduce the size of their boundary to say,=
a 3 inch diameter disc. My limited knowledge suggests they will, but I do=
not have the skill or equipment to test this.
Hi All
On the other hand I could just build one and give it a try.
So I did that.
I planned to use 3 inch plywood discs because they would make a good fit, s=
upported by rubber bands, inside the modified poly pipes mentioned in my pr=
evious post. However, I came across a couple of 3 inch diameter plastic to=
ps from Cringle crisp/chip tubes. The EM172s were easily fitted onto these=
and suspended at the ends of the poly pipe. The sixth, seventh, eighth, n=
inth and tenth photos, in the "two into one blimp" album start with the new=
rig fully clothed and follow its undressing thereby demonstrating how it w=
as put together. The album is here:
https://picasaweb.google.com/G0SBW.PM/TwoIntoOneBlimp
The next job was to test it against a well performing largish boundary arra=
ngement. I chose the lightweight Shure MX391 equipped boundary (which perf=
ormed OK in comparison with a similar AT3032 equipped boundary. Photos 11=
and 12 in the above album show the rigs as tested.
The weather forecast for early this morning was reasonable; so 4 am found m=
e setting up the test in my back garden. The weather was not perfect as th=
ere was a 10/12 mph wind with gusts. Because both the rigs under test were=
PIP powered I used a HiMD minidisc for the MX391s and the LS-10 for the sm=
all barrier EM172s. Both recorders operating 44.1/16
Recording started at 4:30, while still dark, and continued for just over an=
hour. Because of the darkness, and lack of a flash light, recording level=
s were set with more luck than judgement. As it happens, the recording lev=
el was fairly evenly matched on both recorders (the settings were "15" on t=
he HiMD and "high 4" on the LS-10). Other than picking a suitable snippet,=
adding fade-ins and fade outs and then converting to 320 MP3 the recording=
s are as taken. There is a little wind rumble in places but, thankfully, n=
o aircraft noise - there are few flights at this time in the morning. The =
comparison recording is below with the MX391 recording being the first 4 mi=
nutes followed by the same 4 minutes as recorded by the EM172
http://soundcloud.com/g0sbw/new-blimp-test-mx391-vs-em172
The recordings are not vastly different. To my ear the EM172 small boundar=
y rig sounds a little more detailed and smooth? The last two photos in the=
Picassa album above show the spectrogram and the waveform for the .WAV fil=
e.
Prolonged listening might throw up more differences, but for now the new sm=
aller boundary rig gets my vote. It is also some 3 to 4 ounces lighter tha=
n a similarly set up EM172 larger, square boundary, rig. It currently is =
my chosen handheld rig for the nightingale walk. Apparently the smaller bo=
undary size makes little difference?
Any comment, critical or otherwise, is welcome
Cheers, TomR
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