First Ribbon Mic build

[ciscan.81]

Here are some pics of a 'from-scratch' ribbon mic I built last year...nothing ground breaking but I like it.

I got some advice from ribbon mic community here (notably Stewart) and promised some pics of the completed build...that was some time ago...

Anyway here they are:

shiny!!! Body 38mm mild steel tube, end caps lathed from solid mild steel - nickel plated

Front of offset-style ribbon transducer milled from mild steel and nickel plated

with SS filter mesh

back showing 1mm solid copper humbucking wires - overkill?

bracket carved from pvc electrical conduit to hold lundahl transformer and transducer

Anyway I am really happy with the look and sound of the mic and enjoyed the learning experience.

Thanks again to the ribbon community here for all the great info posted in discussion forums.

-Wayne

 

[micaddict]

Beautiful work!

Looks like you're not just good with electronics.

 

[mabell313]

I love the use of alternative materials!

 

[ciscan.81]

Thanks!

Oh, I forgot to mention, the ribbon clamps are made from pure copper (bottom) and brass (top) plated with pure silver...with holes tapped for 1.6M non-magnetic SS screws...that was tricky!

Ribbon is 2.5 microns...

 

[zebra50]

Great work! Looks awesomely elegant and I love the plastic part too - very creative. I bet it sounds great!

 

[reanimatorstudio]

Can't believe this is DIY. Looks real pro and expencive.

 

[OPR]

Nice work!!

 

[adeptusmajor]

Sound clips, or it didn't happen. 


Beautiful work, BTW

 

[zephyrmic]

Looking at your construction, which is fantastic, I could not see how you insulated the ribbon clamps from the mild steel motor assembly. Would you care to explain? Also, have you found any benefit in using steel as the motor body and providing a magnetic return path thereby? Interested to see your comments.

Kindest regards,

zephyrmic

 

[tchgtr]

Very nice! I'll bet it sounds great.
I do like the vibe of the ribbon folks here...
Keep 'em coming.

 

[ciscan.81]

Looking at your construction, which is fantastic, I could not see how you insulated the ribbon clamps from the mild steel motor assembly. Would you care to explain? Also, have you found any benefit in using steel as the motor body and providing a magnetic return path thereby? Interested to see your comments.

Kindest regards,

zephyrmic

Thanks! I really do love this mic.

I insulated the clamps from the flux-frame using silicon rubber insulating washers...the rectangular ones with a hole you get from most electronics stores...I cut them down to fit and then used a very thin smear of epoxy to glue the insulator to the frame and then the clamp to that...

There is about 1/2mm of clearance between the sides of the clamps and the frame.

I spent a lot of time reading about magnetic return paths, and chose a thick steel flux-frame and a steel body for this  purpose (apparently there are steels with better magnetic properties, but they weren't readily available)...

Obviously the trade off with thick flux-frames is the lengthened acoustic path (distance from front to back of the ribbon) and according HF roll off...I tried to strike a good balance and tapered the outside edges of the frame to help shorten the path a little bit.

I'd love to say that my design and use of a steel body made a big difference, but I have no means to measure or compare it. I just figured it has to help!

Steel also has the added advantage of being cheaper than brass and available in a wider range of sizes. Being ferrous, I think it may also help with shielding the motor from external magnetic fields (correct me if I am wrong there).

I can say that the neo-magnets in the frame are very strong, inserting the motor into the body is difficult!!!! The mic's output is higher than I expected (a bit hotter than a Royer-101). Perhaps the steel magnetic-return-path has something to do with it. (I like to think so).

The sound of the mic is similar to a Royer-101 (cheaper 121 with same motor in larger Chinese-made body). I kind-of modeled my motor design on the Royer-offset so I have a slightly brighter sound turning the mic around to the back. A while ago I borrowed a 101 from a friend and did some quick comparisons on a guitar cab. My mic has a fuller bottom end (perhaps due to the Lundahl transformer?), or the ribbon damping arrangement...? which I like and find useful as an 'out-the-front' drum mic/mono overhead. Otherwise pretty similar.

Cheers

-W

 

[zebra50]

Hi Wayne,

>> so I have a slightly brighter sound turning the mic around to the back.

Did you flip the phase when you did this? Your mic looks pretty symmetric from the photos so could be a phase cancellation issue, especially if you are testing with voice on headphones.

I might send you a transformer to try....

Stewart

 

[ruairioflaherty]

Where do I place my order?

 

[ciscan.81]

Hi Stewart...

I didn't flip the phase when turning the mic around...should I have?

My understanding of the offset ribbon design is that it was originally employed to allow the mic to handle higher SPL, with the ribbon being forced into the air gap/flux between the magnets, rather than forcing it out at high sound levels...

The theory goes that a byproduct of this is that the ribbon is positioned slightly differently, front / back relative to the resonant chamber of the mic body...thus a slightly different frequency response...

Another theory I think I read somewhere it may have something to do with the slightly different sized tiny resonant spaces bordered by the magnet sides, ribbon front or back and damping screens too...?

I am more than happy to be corrected by someone more knowledgeable on all this...

...hmm transformer cool! ...sounds interesting...I'll reply to PM...I'll need help deciding what specs to go for...transformers are not my forte...

Cheers!

 

[ciscan.81]

Where do I place my order?

Hah! Thanks mate!

If I factor in the time it took me to build this thing its going to be expensive!!! Could definitely outsource and upscale elements of the manufacture and speed it up a lot though...

Building them to sell would be really cool, but given patent issues, lack of anything really 'new' about it and the prevalence of ribbon mics in the market these days...I'm not sure it'd be worthwhile...would sure beat a day job though!!!

...who knows, with Stewart's transformer we could be onto a winner!!!

 

[zebra50]

>>I didn't flip the phase when turning the mic around...should I have?

Well, with a figure 8, the back of the mic is the reverse phase from the front. Do some experiments to convince yourself... plug in and listen to the mic on headphones. Speak into it whilst flipping the phase back and forth, turn the mic around, do the same... it is quite revealing! 

 

[ciscan.81]

Well, with a figure 8, the back of the mic is the reverse phase from the front.

Understood, but I didn't realise it would make a difference to the sound/FR provided I am not using another mic to cause cancellations etc...am I wrong? I did just read Royers site which also suggests flipping the phase when using the back side of their offset mics?

Curious...Explain...?  ???

I'll do your test with the phones when I get home...

I did the (quick and rough) front to back comparison by recording some guitar cab on both sides and then listening back..it is subtle but I think there is a slightly different high end response...

 

[zebra50]

Understood, but I didn't realise it would make a difference to the sound/FR provided I am not using another mic to cause cancellations etc...am I wrong?

No, you are right for recorded sound (although I know people who claim to be able to hear absolute phase). But...

For the specific case of monitoring on headphones you have two sound sources -  the 'real' sound of your voice, plus the monitored sound through the cans, and they can cancel quite dramatically - as you will find when you try it.

 

[Marik]

Congratulations! Great beginning! Beautiful work!

You don't really need a humbucking loop--just dont insulate the top clamp and then make a good ground connection between frame and body. Make sure all the surfaces are very clean and well clamped, otherwise it will increase ribbon DCR (higher noise) and contaminated/oxidized contacts can lead to RF problems.

My understanding of the offset ribbon design is that it was originally employed to allow the mic to handle higher SPL, with the ribbon being forced into the air gap/flux between the magnets, rather than forcing it out...

That's what Royer patent says. In practice I have very hard time imagining it happening. Ever seen how much ribbon moves even with the highest SPL's (considering there is no much air movement like say, with kick drum, where ribbons not used, anyway)? On the other hand, even when out of gap, the ribbon is still in the magnetic field (even though reduced), so mechanism of distortions is still questionable--if anything that would be rather compressing...

Another theory I think I read somewhere it may have something to do with the slightly different sized tiny resonant spaces bordered by the magnet sides...

That is cavity resonances, which do affect top end response.

Best, M

 

[ciscan.81]

Hi Marik

Thanks for the comments.

I did wonder about using the frame as the signal path for the top of the ribbon, but wasn't sure if there would be any unforseen consequences, so stuck with what I'd seen done elsewhere....nice to know it can be done...

If I do another build I'll certainly try doing it this way.  It was a shame to ugly-up the nice clean and shiny frame with the red wires and a bit fiddly to implement.

That is cavity resonances, which do affect top end response.

I thought I had read about cavity resonances somewhere, possibly a comment somewhere of yours on this subject...

Anyway thanks again for the comments, and thanks also for all the info you have scattered throughout the posts here. They were all very useful discussions to read when researching.

Cheers

-Wayne