Rich Peet wrote:
> --- In Walter Knapp <> wrote:
>>You would probably get a bit better PZM gain off the end cap if you
>>polished off the mold marks. At least it seems like you should.
>>
>
>
> Ok, I will set a 600 grit paper to finish the top on all futures.=20
> You'r right that is sloppy.
As I said, I've no idea if it matters, but it looks like it should. I
expect the cap is not flat either, but that's a whole 'nother
experiment, it's endless. Should be able to sand the cap on a block
pretty easy to smooth it up.
Note that most PZM surfaces I've seen have not been polished, more like
a matte finish.
> I am sorry, I don't understand this comment. I thought I needed both
> direct and reflected for pzm to work?
Probably the best place to start on pzm is here
http://www.crownaudio.com/pdf/mics/127089.pdf
My comment more went to the capsule being exposed to the direct sound
from the back. If it's absolutely solid it's probably ok. To be certain
you mount it in a housing and that housing forms the gap.
You want the mic to see the combination of direct and reflected in
phase. Nothing else. It does not have to see them separately.
I'm working on this on the modified SASS. Lang's SASS has the omni's
exposed, the original SASS has their's in a housing which forms the gap.
It's actually two entirely different types of mic. I'm building so I can
test both ways and see just what happens. Your's has the mic pointed at
the surface, which is different than Lang's, but it's still pretty much
out in the open. The gap formation depends on the regularity of the
front capsule surface in yours. It's also pretty critical that it be
closely parallel to the surface of the end cap.
>>I'm wondering how this element would compare to something like the
>>Panasonic WM-61A.
>>
>
>
> God yes I need better stuff in the basics. I have searched for years
> to find a element with good specs. The trash I used is $3 what is
> the cheapest for the wm-61a? Should that be done for 2.5-12. khz?
When I got some WM-61a's this year they were under $3 if I remember
right. Their frequency response lists as 20 - 20k. -62dB S/N Not
wonderful either, but the best of the panasonic capsules.
It's the biggest need for experimenting, a quality capsule that's not
expensive. So you are not that unhappy when it gets wrecked.
> ya. I put it out their for ie 6.0 and never thought that Netscape
> wouldn't resize. Sorry.
And this is Netscape 7, just out. It will resize if there is a html
wrapper with a size and sometimes otherwise. But you still end up
downloading that great big picture with all the extra bandwidth, resize
or no. I always organize them to screen resolution, set to 72 dpi, even
though that's not really current screen resolutions. That way they are
only downloading the pixels they will see, not a whole bunch that get
scaled down.
I just checked and ie 5.0 on my mac also makes it big, same as Netscape.
I don't have 6.0 on, tries to spy too much. I don't use ie much at all.
This turns up quite frequently in posts and html. Folks will take a
digital camera photo and just put it up unmodified. Mine are 5
megs/image uncompressed. Even if jpegs, they may approach a meg. A awful
lot to send. I think we are seeing a new rise in this as more people
have high speed connections, but for folks like me, living in the
country with a 56k modem, I notice.
>>>A sample recording 6' under a bird feeder with callers about 20'
>>>away. An expressway with severe rumble is 1/4 mile away.
>>>http://home.attbi.com/~richpeet/proto1.mp3
>>
>>Sounds fairly reasonable, need a lot more variety of recording.
>
>
> If this has value I hope that many others will bring the variety.
It's interesting. But then that's my problem, I've a whole list of
experiments to try. I'm actually a bit more interested in curved surface
PZM's. Crown barely dabbled in that, I have one of their prototypes that
I need to build a power supply for or change the mic. Then from there
I've got to start bending plastic. The SASS housings I'm working on are
another aspect of this. If the curved surfaces get interesting enough I
may build a curved surface mic like the SASS. The plastic for playing
around is fairly inexpensive, the big problem is mics for testing.
I think it's worthwhile exploring the entire area of building
inexpensive mics. And very interested in what's found.
Walt
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