Ribbon Microphone Tuner (Tensioner) Project

guitartoys · Sep 19, 2016

Hello again, just though I’d post a recent update on my quest to make re-ribboning a ribbon microphone easier.

This time up, a Ribbon Tuner (Tensioner) jig. This has interchangeable carriers for different ribbon microphone trusses. So far I’ve made Carriers for Rick’s (http://www.diyribbonmic.com/parts/) truss, in addition to carriers for an MXL R80 and an MXL R144 ribbon microphone. This way you can print one jig, and then use a carrier for your specific mic.

This acts as both a jig to help you install and properly align a ribbon in the trust, in addition to allowing you to fix one end of the ribbon, and have the other end affixed on a moving end, to allow you to use a screw to move the moving end to put tension on the ribbon. Once you get the tension right, you can lock down the other end of the ribbon.

While a number of folks already have the means to tune the ribbon (either with a strobe or other electrical means), this will allow you to use your own electronics for that purpose. Next up, will be a little Arduino controlled device, which will output a signal to feed the ribbon (1Hz to 100Hz in 1Hz increments, and adjustable gain), along with a strobe, so you can watch the ribbon as you make tension adjustments to the ribbon. After that, I intend to modify the circuit to allow a stepper to make the adjustments automatically, if I can get it to work well.

But in the meantime, you can use this jig to re-ribbon a truss and use your own methods to tune it.

If you are interested in me designing a carrier for a particular ribbon truss, just let me know. I will be happy to make one for you. But you will probably need to send me the truss, so I can do the design work.

Please check out my instructable

http://www.instructables.com/id/Ribbon-Microphone-Tuner-Tensioner/

I of course welcome your feedback.

Thanks.

Michael

TLRT · Sep 21, 2016

I'm curious what is the correct way to set up the ribbon tension, what devices do I need, signal generator, and scope? I always made this by ear, which sometimes gave good results , and sometimes not

guitartoys · Sep 21, 2016

Yes, you can absolutely eyeball it. I've been eyeballing it, and very satisfied with the results. The problem has been, if I make the ribbon too taunt, it's really hard to easily back it off. I think this jig makes it a lot easier, as you can add tension in teenie increments. Then lock it down. So even if you want to do things manually, I think the jig will be worlds of help.

When it comes to tuning, you can get consistency across multiple mics, essentially being able to create matched pairs.

With respect to actually performing a tuning all I can tell you is what I've learned thus far.

First you use the transformer connected to the ribbon element. And you inject a sine wave into the output side of the transformer from a signal generator.

In my rig, you go ahead and solder the negative lead to the ribbon truss. You lay in the ribbon, get it centered, and then lock down the negative side on the fixed end of the jig. You get the other end on the moving part (connected to the threaded screw) centered up, and then lay the piece of aluminum (with the plus lead connected) in the slot to lock down the other end to allow you to tune it. Once you get it tuned, you lock down the other end of the ribbon.

What frequency? What I've seen on the web has been frequencies of 12 to 14 Hz as well as 40 to 60Hz, although it seems you would want to stay well below 60Hz. I found an article which said the RCA 44 was tuned to 20 to 25Hz, and the Coles were tuned to 40Hz to 45Hz. I'm going to look up their ribbon sizes and compare against my ribbon sizes as a starting point.

What voltage, I really don't know yet, but will sort out once I get my little arduino built. Too much, you blow the ribbon. To little you don't move the ribbon enough.

This is the black art that seems to be the secret no one wants to share. So I'm hoping as I learn, and also put out this little Arduino device, folks can make the tensioner, build the Arduino and publish their findings.

When using a strobe, you inject the signal as above, but then use something like an LED strobe to then watch the ribbon movement. What I've been told by someone who does it this way, is that the strobe needs to be 3Hz out of sync with the sine wave. So if you are tuning to 14Hz, you set the strobe to 17Hz. I plan to make the Arduino settable for both the sine wave and LED strobe frequency to sort it out. Then you adjust the ribbon to a motion that looks like resonance. I guess.

Otherwise, you could also measure the resonant voltage. so you have ground of the signal generator going to the transformer, the hot side of the transformer hooked up to a resistor, and the other end of the resistor hooked up to the signal generator. Then you measure (from what I understand most commonly using an O-scope) across the resistor. As you increase the tension on the ribbon, you will see the voltage go up, and once you pass the sweet spot, the voltage will go down. So you back off back to the sweet spot, which should be the resonant frequency.

I'd really like to try to use an Arduino or similar to measure the voltage, but at this point I don't know if it will be sensitive enough. So I'm going to start with the strobe, but still use the resistor and measure across it with my O-Scope to see just how much of a voltage swing there is. If it is something that the Arduino or similar can detect, what I'd really like to do is run a stepper to adjust the tension, to make everything automatic. I'd replace the manual screw with a stepper with one of those long Z-Axis rods on it, and let the stepper do the adjusting.

But I'm also concerned that the abrupt nature of the stepper starting and stopping, might make too much motion on the ribbon, and interfere with the process.

Anyhow, I'm learning lots, having some fun, and who knows maybe something useful will come out of it.

Thanks.

Michael