Thanks Mike!
Obviously I have some more experimenting to do.
I still have an 8020 in my hands (but soon to be sent back to Syntec
for replacement).
The distance from the top of the wire mesh grid to the top of the
element seems to be 5 mm. The diameter of the element is about 15 mm.
The metal edge at the top of the mic is slightly wavy, maybe
something like 1.5 mm variation. The highest part of the wavy edge
is about 1 mm down from the top of the wire mesh grid. Making the
lowest part of the wavy edge about 2.5 mm from the element. So
that's not very much, and perhaps the flush-boundary response may not
be much affected after all.
I will try flush mounting then compare poking out to diaphragm depth
as you suggest Mike. And do some googling.
Vicki
On 22/11/2011, at 10:35 AM, Mike Rooke wrote:
> If the mic is recessed in the boundary and theres a cavity formed
> due to the mic body and capsule postion then the boundary will be
> affected, a resonator is formed which will narrow the directivity
> and also boost the high frequency response at the same time for
> direct sources, for side on its probably attenuating more than an
> exposed / flush mounted capsule.
>
> If the mic body is sticking though the boundary then you may
> attenuate the boundary effect at high frequencies (> 10Khz) cause
> narrowing of the pickup pattern, and possible secondary reflections
> depending on how far away the diaphragm is. -Sound wave arrives at
> the boundary, traverses along the boundary hits the outer edge of
> the mic body and diffracts, some waves continue over the
> obstruction and contribute to the boundary. Size of the cylinder,
> depth to the capsule are parameters that can be modeled but beyond
> this discussion. Its one reason measurement mics have a slotted
> head to improve off axis response.
>
> All of the above depends on the mic diameter and how far it is away
> from the boundary surface, for most material < 8khz your fine.
>
> Play with the (use google) "ripple tank" application to see such
> effects in the browser, but for most the actual influence is very
> small and may even be beneficial narrowing the polar response.
>
> All hot air without testing the effect of the MKH flush mounted and
> then poking out to the diaphragm depth.
>
> BR
> -Mike.
>
>
> --- In vickipowys
> <> wrote:
>>
>> Hi Dan,
>>
>> Thanks for your comment!
>>
>> A question, wouldn't the metal tube of the mic then block some of the
>> sound that had been gathered by the boundary surface, from reaching
>> the mic element?
>>
>> I am not quite sure how to visualize how the sound gathering works.
>> Any explanations? Anyone?
>>
>>
>> Vicki
>>
>>
>>
>>
>>
>> On 22/11/2011, at 2:01 AM, Dan Dugan wrote:
>>
>>>> http://www.caperteebirder.com/index.php?p=3D1_27_recording-gear-2
>>>
>>> On that page you say:
>>>
>>>> MKH 8020 not suitable for SASS:
>>>> One drawback to the 8020s is that the mic element is set 5-10 mm
>>>> inside the mic housing, rather than flush with the surface, making
>>>> the mic unsuitable for SASS-style of mounting. (For SASS the mic
>>>> element needs to be flush with the boundary surface).
>>>
>>> This is not a problem! Let the mic stick out from the surface of
>>> the baffle (SASS or whatever kind of baffle you want the mic to be
>>> flush-mounted in) so that the diaphragm of the capsule inside the
>>> housing is level with the baffle surface.
>>>
>>> -Dan
>>>
>>
>
>
|