Ribbon microphone design

[monkeyxx]

I am on the short eventual path to attempting to build my own ribbon microphone, or a few.  I have some chassis/body materials, some corrugating gears (10-11 ribs per inch) and a collection of information, photos, white papers, and some experience with adjusting ribbon tension, and replacing transformers.

My question is, Why does the MXL R40 sound so different from the Royer R-121?  The ribbon motor assemblies are similarly proportioned, kind of small rectangles with similar looking magnets and more or less a similar looking ribbon length.  I've never compared them in real life, just from photographs.  The R-121 appears to have slightly more corrugations per inch, and possibly deeper corrugations, but I haven't seen it in person.  I think they both report 2.5 microns foil thickness.

The royer is a lot brighter and more present in the treble, which is exactly what I'm hoping to approach in my DIY builds.  The R40, while pleasantly so, is a bit darker, thicker, bassier, midrangier, which is great for guitar amps but I don't know if it's the best all-arounder.

The main difference I can spot visually is the difference in body and grille size, with the R40 being much larger.  Does this have a huge effect on frequency response?

There are things I can't account for, visually, like magnet strength and ribbon tension, for example, and exact dimensions and proportions.

I know a transformer will have a sonic signature, but I wouldn't guess from experience that transformer coloration would be the more significant design factor, compared to others.

Mainly could anyone offer advice on achieving a brighter tonality from a passive ribbon microphone design?

 

[Dylan W]

The offset ribbon motor in Royer ribbons makes the back brighter than the front when the source is close enough for the offset to have a significant acoustical effect. http://www.royerlabs.com/2in1.html

That doesn't seem to explain the whole difference though, since the front of a Royer is still more open than the R40.

I've always wondered this too. Curious to see what others have to say.

Dylan

 

[zebra50]

The transformer can have a big effect if the designer chooses.

By playing with the inductance it is possible to introduce a degree of high pass filtering that can partly compensate for proximity effect. Also winding capacitance can play a role at the top end - this tends not to be very big with ribbon transformers, but I would wager it is worse on the China mic than the Royer.

Another important factor on the top end response is the relative path between the front and rear of the ribbon. I suspect that is a big part of the difference.

Usually the China ribbon mics like the MXL have a wide tolerance on ribbon tuning and thickness. Many I've seen have been between 4 and 6 micrometers thick, based on impedance measurements and feel.

Hope that helps - keep reading around this forum, there were some good discussions over the years.

Stewart

 

[dmp]

If you replace the ribbon in the mxl it will sound WAY different.
The thickness advertised in Chinese mics has no meaning, evidently.
I recently changed the ribbon in a mxl r144 with 1.8um foil and the mic is balanced and has plenty of highs now. Not remotely as stock.

 

[Ishi]

I think it affects the high-frequency response of the body shape.

 

[ricardo]

Have a look at http://downloads.bbc.co.uk/rd/pubs/archive/pdffiles/monographs/bbc_monograph_04.pdf which describes the design of what IMHO is still the best ribbon in the known universe.

Wish someone would make a modern version of this with stronger magnets & power output.