low cost APE/SKM type pressure spheres for SD omni mics

[studer58]

I'm keen to try making some low cost 40mm diam diffraction spheres (similar to SKM/KA/APE 'balls') for use on my SD omni mics. My understanding is that these are typically made from wood, and then lacquered or highly polished to attain a reflective surface...so surface hardness rather than mass is the desired quality here ? However regular rubber squash balls are approx the right size, and easy to bore a hole in...and if slightly undersized the rubber would grasp around the outer diameter of the mic quite well. The low mass would be an advantage, compared with wood...not to mention lower cost. The fact that the squash ball is hollow could be a negative, as a 'resonant chamber' so close to the mic diaphragm sounds bad (in theory). To aid in reflectivity, the squash ball could be coated in a hard resinous paint or varnish. Any ideas out there as to why this might..or might not...work ? Alternatively, children's solid rubber "high bounce" balls from a toy store might be a good alternative, and non-resonant to boot !
Ray

[Corran]

I'm doing the same thing.

I found some pre-cut wood spheres at Michael's (craft store) that were in the "doll making" section (doll heads).

They have a pre-drilled hole that I plan on drilling all the way through. Then, I'm going to use some rubber washers to obtain a seal on the mic. I used these washers for a plexiglass shield with similar principles and it works very well.

I don't know about the actual acoustics but if they are normally made out of wood, then I'm sticking with wood too. The heads were only like $2.

[John Willett]

There was a guy in the States who made these for various microphones.

Can't remember his details; though I'm sure I read about them on this forum.

[Corran]

Interesting, if anybody finds that post please link.

[studer58]

Originally Posted by Corran

Interesting, if anybody finds that post please link.

I found the thread tonight.....worth reading from page 6 onwards to see elaboration of the issues and the maker, Mark Donahue of Soundmirror's contact details are contained there also !

It's here: New Sennheiser MKH8000 Series Mics

Ray

[Remoteness]

Keep in mind that you can set how many posts you want to view on one page.

I have mine set to 100 posts per page, so saying page six only references your settings.
For me it may be page two...
Someone else many have 50 per page, etc., etc.

In any event, thanks for sharing that link!
Very helpful for sure.

[hughesmr]

Originally Posted by studer58

I found the thread tonight.....worth reading from page 6 onwards to see elaboration of the issues and the maker, Mark Donahue of Soundmirror's contact details are contained there also !

It's here: New Sennheiser MKH8000 Series Mics

Ray

I've tried to PM Mark on these APE balls since this thread died off, but never got a response. I don't know if he's making them or not .... but would sure be interested if so! Mark, you out there?

[mljung]

Originally Posted by hughesmr

I've tried to PM Mark on these APE balls since this thread died off, but never got a response. I don't know if he's making them or not .... but would sure be interested if so! Mark, you out there?

I've done the same with the the exact same result [or rather lack of result]

Let hope for a response now...

[Teddy Ray]

Originally Posted by mljung

I've done the same with the the exact same result [or rather lack of result]

Let hope for a response now...

Peter Drefahl makes them too. he is a great, great guy with an encyclopedic knowledge of all things microphone. His prices are great taboot.

info@pdrefahl.de OR info@drefahlaudio.com


drefahlaudio microphone repair and reskinning service

[hughesmr]

Teddy, nice to see you back. Haven't heard from you since the "old" days on recording.org.

[Teddy Ray]

Originally Posted by hughesmr

Teddy, nice to see you back. Haven't heard from you since the "old" days on recording.org.

Thank you Sir.

[mpdonahue]

We were considering making a large batch of these and selling them, but in the final analysis we decided that the issues of marketing them as a product didn't justify the time involved.
That said, we would be willing to make a batch of the 3 different sizes (30, 40 and 50mm) for Neumann KM, Schoeps CMC and Sennheiser 8020. This will be a one time thing as we do our best to not be in the manufacturing business. (We will not make balls for the DPA products due to the time and effort involved in making the tapered profile of these mics. The DPA spheres are very nice and can be purchased reasonably from DPA)

After calculating the time to machine and materials cost (Guess which one is the lions share of the total....) we came up with $60 each for individual balls or $150 for a set of 3.
I really have no interest in chasing people for money, so orders will all need to be pre-paid.

Please let me know who is interested, which mics the balls will be for and and how many of each size. ForNeumann KM series please check if you have the 22mm or the 23 mm capsules (They made both!)

All the best,
-mark

[Corran]

Wish you made ones for Earthworks mics, I might get one.

I still need to experiment with the wood spheres I found at the craft store and some rubber gaskets!

[mpdonahue]

The hard part of the process is cutting the inner groove that the O ring sits in. If you don't do it just right the ball is either too loose or too tight.

-m

[David Spearritt]

Even though I have access to some state of the art mechanical engineering design services and fabrication, I concluded that it was better to buy the DPA balls after examining how well they were made. I valued my time to more than the cost of the DPA's.