No usable level from Ribbon mics

RawDepth

RawDepth

New member
I have four ribbon mics and have rarely used them until recently. Now I discover that two of them have no usable level.

I was experimenting today with my kick drum. I tried using the ribbons out in front of the drum at a 45 downward angle. Two of them were so hot that I had to resort to using the line-in jack on the micpre to keep them from peaking the meter, (and with zero preamp gain.) The other two mics had extremely weak signal using the mic-in jack. With the micpre gain turned full up they barely showed any meter nor waveform movement in the DAW. I can hear the mics working, but only slightly above the noise from the pre.

In all instances nothing changed but the mics, the mic/line input choices, and the preamp gain. The preamp works fine with all other mics. The phantom power has never been turned on while using ribbons.

Is there any obvious cause for this low level?
 
mostly separated wire? Not too many connections to check in those - might be worth a look to make sure they're not coming apart
 
I'd be weary of using ribbons on drums in proximity. They're sensitive to wind, and kick drums generate a lot of wind. Baring specialized use inside the drum or at an angle where the ribbon element is off axis / shielded from the wind. I love the sound of a good ribbon, but they're needy mics IMO. +55dB of gain and other quirks. Is the level just soft? Or soft and off? Slack ribbons, broken mags, bad connections, and other all to common for ribbon mic issues.
 
Well, the one is very low output. Not anywhere near what the other two good ones put out. The ribbon has a tiny bit of sag. One crease in the ribbon is flat. It is not usable with the output being that low.

The second dual ribbon mic is worse yet as far as output. It is all but dead. With the micpre set to full gain and tapping on the mic there is barely any meter movement at all. One of those ribbons has only the slightest detectable amount of sag. Like maybe less than 1/32nd of an inch of movement. Is that enough to render the mic dead? I mean dead?? There are no wires off or anything else wrong inside that I can see.

Does anyone know where I can get ribbon mics worked on? I would really like to use these mics.
 
If all the wires are good and the ribbon isn't sagging much, then it's probably a bad transformer. Sub in an Lundahl (or Edcor or Cinemag) ribbon transformer. That probably fix the problem, and it will sound a lot better than the stock transformer would sound even if it worked. :)
 
UPDATE:

On the dual ribbon mic, I found one spot where a wire was being pinched. I hadn't noticed it before. The cover (shielding) over the tranny was binding one of the lead wires and apparently had bitten through the insulation. This must have caused a short to ground which stopped the mic from working. I rescued and repaired the lead and now the mic works good again. Woo Hoo!

The other mic probably needs a new ribbon. It works but the output is extremely low and dull.


I just ordered some bulk ribbon material and a special corrugating tool to make my own replacements when I need them. If a new ribbon gives new life to this mic then maybe I'll make some for you other guys who need ribbons.

Give me a week or so to get the stuff in. I'll keep you posted.
 
UPDATE 2:

The new ribbon material came from an art supply house. They could not tell me the thickness of the material so I took a chance on it anyway. (It was only $7.99) Well now I know that was a mistake.

It is much too thin to hold the corrugations. It just goes flat again fresh out of the machine. What a disappointment. It does not have enough self stability to hold its own shape. Not a total loss, however...maybe my girlfriend will silver leaf something for me. :D

Anyway, now I have ordered some different material that is 4 microns thick. I wanted 2.5 like the original but the price is too high for just casual experimenting. According to my research the thickness only effects the sensitivity anyway, so, it should still work.

In the mean time, just for shits and giggles, I made a ribbon out of cheap household aluminum foil from the grocery store. It doesn't say on the package but it is probably around 25 or 30 microns thick. You cannot measure this stuff with a standard micrometer. You need to use a microscope outfitted with a calibrated oricle, which I do not have. I just wanted to see if it would work in the mic anyway.

[Fast forward 30 minutes...]

So far so good. The mic works perfectly but is very hyped in the lower frequency range. It kind of sounds like a cheap kick drum mic. The mids and highs are indeed there but rather off-balance compared to the lows. It sounds very muddy but is not distorted.

Hmm. I'm not sure if that is a bad thing or not. I could use the mic as a second low-end track for blending with another mic. It might work in places such as on the back of guitar cabs, kick drums, double basses, etc. Due to the lowered sensitivity it would need louder sources. However the heavier ribbon would take more abuse. I wouldn't always have to angle it downward on those loud sources.

Well maybe I've invented something here. The bass ribbon. We'll see.
 
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UPDATE 3:

Well, this is getting interesting. I tried the mic with "kitchen foil" in it on a kick drum. Not too bad for a test run. (My barroom drum kit is the only one I have here today. This drum needs new heads but you get the idea.)

I stuck an SM27 condenser inside the drum about 6" from the batter head. I set it to -15 dB pad and angled it slightly off axis.

Then I put the ribbon mic outside the drum about 8" out from the hole, also off axis to protect it some.

This first file is the SM27 as recorded raw. No EQ or effects of any kind.


This file is the ribbon mic. To give it some life, I made a +4 bump at 60 Hz, but no other changes.
(This is the mic with standard store-bought aluminum foil for a ribbon.)

Then I mixed the two files together without making any changes...well, other than levels for blending.


Today I received the 4 micron ribbons that I ordered to fix this mic but I am not sure I want to install that just yet. Hell, with some better heads, some beater "click", and a little "room" mic mixed in, this wouldn't sound too bad.

What do you guys think of my accidental kick drum mic?

(Is anyone following this thread or am I just here talking to myself?)
 
:D Not so much "bass hyped" as "no high frequency response whatsoever" ;)

Art supply aluminum leaf is 0.6 micron; very difficult to work with. I've done that and I'm not doing anymore :o
 
Yes, apparently the loss of sensitivity (from a thicker ribbon) starts at the highest frequencies and works itself downward. I am guessing that if the ribbon were thicker yet the loss of sensitivity would effect the lows as well. Since the low frequencies have the greatest amount of energy they are the last to die out.

This phenomena works for this miking application because I would have rolled off the mids and highs anyway on that front mic. Instead, my poor design seems to be doing that for me naturally and presumably without any phase issues that EQ can cause.

I am reading that in a pressure gradient design such as this, the path length from front to rear effects the frequency response. This experiment has brought me to understand that the sensitivity must first be under control for that to be realized. This also helps to understand why ribbon mics with thinner ribbons sound more natural. The less mass the ribbon has the better it will dance along with the various nodes and antinodes of the sound wave.

I don't see myself designing capsules anytime soon, but I do like to understand how things work.

I wonder if the thicker ribbon has greater electrical resistance.
 
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RawDepth said:
Yes, apparently the loss of sensitivity (from a thicker ribbon) starts at the highest frequencies and works itself downward. I am guessing that if the ribbon were thicker yet the loss of sensitivity would effect the lows as well. Since the low frequencies have the greatest amount of energy they are the last to die out.
Click to expand...

Has strongly to do with transient response as a function of mass. A high frequency wave, even an energetic one, will start to move that big heavy foil, which says, OK, I'll start moving, gimme a minute, then the wave rarefies and wants to pull the ribbon back the other way. The ribbon is like, WTF, dude, I thought you wanted me to go that way :confused:

This phenomena works for this miking application because I would have rolled off the mids and highs anyway on that front mic. Instead, my poor design seems to be doing that for me naturally and presumably without any phase issues that EQ can cause.
Click to expand...

Hmmm. Well, I think if you were to measure the phase response of the ribbon motor you might think otherwise. And with your typical cardioid dynamic, its frequency response is a function of its phase response--that path length difference creates a phase difference which gets you your cancellation. And the "problem" of phase response of an EQ is vastly overrated. We are much more sensitive to frequency response than (static) phase response anyway.

I wonder if the thicker ribbon has greater electrical resistance.
Click to expand...

Less. More metal = more space for electrons to move.
 
RawDepth said:
Yes, apparently the loss of sensitivity (from a thicker ribbon) starts at the highest frequencies and works itself downward. I am guessing that if the ribbon were thicker yet the loss of sensitivity would effect the lows as well. Since the low frequencies have the greatest amount of energy they are the last to die out.
Click to expand...

In theory, because of the forces on the ribbon, there is no direct relationship between ribbon mass and frequency response, so the mass/sensitivity relationship is linear on all the frequencies.

Since the thicker ribbons have lower resistance (in our case we could call it "impedance") to some extent we could make up the sensitivity loss with a larger transformer ratio. With thick ribbons there would be not enough acoustical damping to get rid of the resonances, so the higher ratio would be benefitial as means of additional electrical damping.

Best, M
 
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