Sennheiser MKH800 twin

[Sebastian Krause]

Hi together,

anybody knows, what exactly is between the two capsules of the MKH800? It's only a brass ring, is there any labyrinth or damping material?

thank you!

Sebastian

 

[Tim Campbell]

Well there is most likely a delay network. That would be the easiest way of having a multi pattern mic.

 

[Sebastian Krause]

Thank you for your answer. Is there a way to build it by myself?
I still have two capsules from MKH30 and would like to test it...
Sebastian

 

[Tim Campbell]

Well those are fig 8 capsules. If they are purpose built capsules with only one membrane then you might be able to do it within a mixing board by combining signals. If it is the same capsule as the 800 then just wiring it would work. If you really wanted to build a multipattern capsulle from 2 capsules it might be easier with 2 MKH40 capsules.

kingkorg stated that the mkh series capsules have a huge midrange bump and need eq in the amplifier circuit and are tuned very low. Unless you are using them as rf capsules with a Sennheiser preamp you may find you can make a good sounding mic from cheap chinese capsules easier

 

[Sebastian Krause]

Thank you Tim.
The situation is: some years ago, I got those MKH30 capsules. I made some copies of the MKH30 with the original schematic, you can find in the service manual and I use this microphones a lot. I also made an "omni" by closing the capsule on the backside and use this combination as m/s setup.
It's nice for live recording because of the possibility to manipulate the stereo-width and the microphones are very quiet, so there is no need to set an exact gain... this is helpful in unattended recording and live situations, I play myself ;-). Today I have still some capsules and it would be nice to have other characteristics too...

Sebastian

 

[Tim Campbell]

Well you could convert them to some version of cardioid by blocking half the air pressure to the backside of the membrane then you would have all three patterns with your 3 mics.

 

[Sebastian Krause]

OK, but how to do this?

 

[rogs]

... I made some copies of the MKH30 with the original schematic, you can find in the service manual and I use this microphones a lot.....

Can I ask how you approached the task of copying the inductors?.... How did you go about selecting appropriate bobbins and ferrites, for example?...

 

[Sebastian Krause]

ops, this is 10 years ago... I hope, I have the data for you... will search for tomorrow ;-)

 

[Tim Campbell]

Well you could completely block the back back membrane into an omni and then start very slowly drilling holes in the obstruction until you achieve cardioid. Look at what they have used on cardioid ribbons.

 

[Sebastian Krause]

I use cardoid ribbons, Beyerdynamic M500 clones ... build from BM85 radio microphones... there are no drilles holes on the backside of the ribbon but one hole, 5-6mm diameter as far as I remember... filled with wool. Yes, the condenser capsules are using this holes... what do you thing about the volume behind the "closed" side, more in the direction of an "infinite buffle" or more in "tuned buffle"?

 

[Tim Campbell]

You simply need to half the air pressure reaching the rear. It doesn't matter how. Be inventive.

You don't want to add any attenuation of frequencies. It is already a working capsule with the response you want.

 

[Sebastian Krause]

Can I ask how you approached the task of copying the inductors?.... How did you go about selecting appropriate bobbins and ferrites, for example?...

Hi Rogs,
in this time, I had no experience in building a microphone, I worked in a company making ultrasonic hardware an software, we did test equipment for automotive. But I made music and I always made records from... When I found the MKH30 capsules, I decided to make some microphones... The schematic was availible... OK, the circuit starts with an oscillator in the region of 8-10 MHz as far as I remember.. you can find it in service manual. I got two sets of trafos from Sennheier as spare parts and made some measurements.... I think only inductivity... then I searched for a core, optimized for the frequeny range (and with adjustable symmetry) and rebuilded the inductivity of the original coils... it works... I'll search for the core tomorrow...
Sebastian

 

[Sebastian Krause]

Hi Rogs,
I found it but it's not 10 years ago, it was in 2006 ;-)
The Core is an P-Type from TDK, Material K1,with AL40.
I try to attach the data sheet and a picture...

 

[Sebastian Krause]

You simply need to half the air pressure reaching the rear. It doesn't matter how. Be inventive.

You don't want to add any attenuation of frequencies. It is already a working capsule with the response you want.

Hi Tim,
thank you, I will make some experiments ;-)
Have you some hints for me, how to measure microphones?
Sebastian

 

[rogs]

Hi Rogs,
I found it but it's not 10 years ago, it was in 2006 ;-)
The Core is an P-Type from TDK, Material K1,with AL40.
I try to attach the data sheet and a picture...

Thanks for that... very interesting.
I'm guessing you used the 'real' Sennheiser coils as a reference, and then experimented with the actual number of turns you needed for each winding?
(I'm assuming the properties of the TDK cores were a little different from the originals? )

 

[Sebastian Krause]

yes, I measured the inductivity between 6 and 8 MHz from the original coils and rebuilded this inductivity for all coils with my cores...

 

[rogs]

yes, I measured the inductivity between 6 and 8 MHz from the original coils and rebuilded this inductivity for all coils with my cores...

Were you able to get sensitivity and noise figures similar to the original Sennheiser figures, from your DIY mic?

 

[Sebastian Krause]

no idea, I don't know how to measure... but I'm very happy with sensibility and noise. Some years, I recorded wit the line-level input of a Digigram VX in my notebook... this is how they look inside and assembled...

 

[Sebastian Krause]

this was the first pair with original coils...