building a ribbon mic part 2: listening test

One of the best pieces of advice I got after building my ribbon mic was to test it through different preamps (thanks John Sanacore).


At my house I noticed some RF buzz, which is actually typical because my house is an RF nightmare.  I decided to ping the designer, Rick Wilkinson, and ask his advice.  Rick responded almost immediately with a comprehensive and detailed troubleshooting list that was incredibly helpful.  The problem ended up being a faulty cable, but I learned that the brass grille was part of the faraday cage from the exchange.

I took the mic to work the next day and ran it through the John Hardy M1, but wasn't very impressed with the sound.  It actually had sounded louder and clearer at the house through the RF buzz.  I then plugged into a sound devices pre similar to the one I used at home and was much happier with the output.  I also began looking into getting a cloudlifter to help with impedance loading and output gain from the mic.  My research was showing that ribbons in general tend to want pretty loud sources, but I have designs on using in more delicate situations and needed get it up to par there.

I emailed Rick again, and again he was again super responsive and detailed.  here's a quick excerpt of what he said to me regarding my experiences to this point:

High end response is determined by the input impedance of the preamp.

Generally, a higher input impedance delivers better high-end response in ribbon mics.  A REALLY high impedance preamp (10k ohms or higher) like the AEA TRP, or my DIY Preamp Kit made especially for my mics (available in another month or so) will really help the top end.  

"loading" is the term for the interaction between the output impedance of a microphone and the input impedance of the preamp.  The correct description of this interaction is something like: "The microphone has to work harder, if the input impedance of the preamp is lower."  This makes sense if the microphone is overly-simplified to a current source: It takes more current to drive a low-impedance load.

A simplified version of this is:

A lower input impedance requires the mic to work harder to deliver a signal. Thus, low-energy, high frequency soundwaves do not get transferred to a low impedance preamp as efficiently as to a high-impedance preamp.

You can see this interaction in my own design, by looking at the impedance curve on the specification PDF on my website.  As the measured frequency goes past 10kHz, the impedance soars - literally off the chart - lowering the effective output of the mic in those frequencies.

That's probably why an Austin Mic through your Hardy sounds like it does... I just looked at the specs, and their Jensen input transformer is 150 Ohms. The current flowing through the ribbon is trying to keep the foil inside the gap, not allowing it to move with low-energy, high-frequency soundwaves.

Supporting that theory, the Sound Devices input shows an input impedance of 2000 ohms - 13x higher than the Hardy.  Better high-end, right?

 And of course, he was correct.  The thing that the cloudlifter provided me was a good impedance load (3000 Ohms) in addition to the extra 20db of gain.  Here's a quickie listening test of the mic through the three different configurations.  All of this audio is 100% as recorded - no gain or eq adjustments of any kind. Note that the gain settings are described in the recordings, and in the first two examples its all the way open, and in the last clip its around 12 o'clock.



So, the impedance loading clearly makes a huge difference with regards to the tonality and the output level of the mic.  IMO it's not very usable straight into the John Hardy M1 unless you're talking about very loud and bright sources, but the sound devices pre and the cloudlifter/M1 combo make the mic much more versatile.

So, given an input chain that I liked (cloudlifter/John Hardy M1) I did a few more little tests with bright, transient things and the mic performed extremely well.



To my ears the mic is certainly mellower on the top end than my usual LDC, the Audio Technica 4050, and its certainly got its own personality.  It handles transients like a dynamic, which is to say that its a little jumpy on the loud stuff and it drops off on the low level stuff more quickly than a condenser.  To me that generally means that its not going to catch as much detail on a highly transient source, and will be happier with something relatively consistent.  It's also got low end for days.

With all of that said, that little strip of aluminum leaf I bought at hobby lobby, cut, corrugated and mounted into that chassis is clearly capable of capturing frequencies well above 20k, which is impressive.  I only ran the instrument tests at 44kHz, but check out how easily it handles all of the frequencies up to the top of that 22k spectrum.

This is the spectrogram of the instrument file linked above:

And here's the zoom in on my voice slate and the tambourine.

This mic is clearly capable of capturing ultrasonic frequencies.

I'll run another test soon where I use it as the S in an MS config on some thick metal movements and see how she does.

building a ribbon mic: part 1 - construction

Way back in July 2011 recordinghacks.com did a $60k ribbon mic shootout, and I had the opportunity to listen to a wide variety of ribbons on different sources due to the hard work of those dedicated pros. 

Around the same time, I was making a big personal aesthetic shift away from bright and quiet mics and towards warmer mics with more character - especially for recording bright and transient sources.  I knew then that I had to have at least one ribbon in my collection.  The problem of course, is that ribbon mics are expensive and I only spend so much money on gear any given year.

The solution to my problem ended up being the DIY Austin ribbon mic.  I don't have a ton of DIY experience, but I can work a soldering iron competently, so I felt like I'd have a shot at building the mic successfully.  I googled around a bit and found a few people that had built the mic with relatively little experience. 

In the end, the audio samples and the $200 price tag had me sold, so I took the leap.

Initially I didn't know exactly how much pride of ownership I'd feel or deserve after assembling the mic.  I certainly wasn't the one who designed it or even who sourced the materials.  In my mind, I was just going to essentially step into the shoes of a mic plant assembly line worker, so how would I feel when the mic that I built with my hands was complete?

Within a short time of the online purchase I had full detailed instructions in my inbox and a link to a series of videos detailing the construction.  It was great to get this in my hands early, as I was able to review the videos and instructions a few times before the mic even arrived at my door. 

The instructions and videos are not high on production value, but they are entirely informative and thorough.  I never felt wanting for instructions or reasoning in assembling the mic.

Once I had cleared out my workspace I set about building the ribbon motor, which meant gluing the two powerful rare-earth magnets onto the brace with a plastic spacer holding them against the walls. Next was to glue the conductive sheet to the edges of the brace and solder the lead wires to it.

All of that was the easy part.

The trickiest part was cutting and mounting the ribbon.  The ribbon in these mics is made from aluminum leaf whose thickness is measured in millionths of an inch.  It is incredibly fragile, and the process requires cutting a 1/4" ribbon with an exacto knife and then corrugating it with a wooden dowel inside of a sheet of paper to make it springy.

I shot a little timelapse of my building the first part of the mic, but the camera ran out of space as I tried again and again to cut and mount a proper ribbon into the ribbon motor.


first part of assembly-austin ribbon mic from rene coronado on Vimeo.


The kit only comes with one sheet of aluminum leaf, and by the end of the evening (and the timelapse) I had ruined all of it.

Undeterred, I went to hobby lobby the next day and bought more.  I spend the next evening ruining even more, but with every attempt I got further and further into the process before making some fatal error.  At one point I had cut and corrugated 3 consecutive ribbons with my exacto knife in a row, and was only breaking them in the mounting process, so I knew I was getting close.

Finally somewhere in the middle of my third sheet of leaf I managed to get a proper cut, mount and tension and I was so excited I was texting pictures to the wifey. 

With the ribbon motor built, I soldered the screen together and assembled the rest of the mic.  A quick test through a sound devices mixpre confirmed that I had a working mic, and I went to bed exhausted and happy.

So what kind of pride of ownership did I have at the end of this?

Tons.

Cutting and mounting that ribbon required a fair amount of skill, and that skill had to come through repetition.  It really took some stiking with it to make the thing work but knowing that I cut and mounted the ribbon that's translating the air movement into the sounds I'll record through it offers a very high sense of pride and ownership of the process.

With that said, Rick at Austin Microphones has put an incredibly high amount of research and development into this project, and I'm positive that even though I spent a few long evenings putting this mic together, Rick has invested far more hours than I have into the creation of this mic. 

In part 2 I've put up some listening tests through different preamps and with a cloudlifter in line.  The impedance of the preamp actually makes a huge difference on these mics, and I'll share some advice that Rick gave me in some subsequent correspondence regarding that and other things.

In the meantime, here's a much better timelapse of Rick building the mic to completion and testing it over a 2 hour period.


 

a short love letter to Mike Monteiro

My phone is constantly loaded up with podcasts done by people I enjoy listening to.  Many of them are audio related, some are not.  But some of them fall in between, and the Lets Make Mistakes podcast on the Mule Radio Syndicate is one of those. 

First a little background - LMM is hosted by Mike Monteiro and Katie Gillum of Mule Designs.  Mule Designs builds websites, but they podcast about design which is what interests me.

Mike is one of my favorite types of internet people.  He's intelligent, opinionated, a little eccentric and not entirely full of himself.  Matt Gemmell and John Gruber also tend to fall into that category.

With that said Mike is more on the eccentric opinionated side of that scale, which is why I love his stuff so much.  He also gives excellent advice to audio guys about the business and process of design just about every time he opens his mouth.  My first exposure to him was this video (which is NSFW if your job frowns upon frequent cursing)


so there's that.  The podcast actually doesn't have that much cursing and it rambles a bit more than a formal presentation like the video above would, but its very worth it nonetheless.

The episode that inspired this blog post was a recent one called "Another Stupid RFP process" There's just so much gold in there that it's difficult to do justice with a quick blurb, but I'll try:

An RFP is a Request For Proposal and is typical of agency workflow.  In it, multiple vendors will make a pitch to work on a specific job at the same time, and the committee needing the work done tends to decide who gets the job based on a number of metrics the derive from the pitches that are made.

It's also an awful awful process, and Mike and Katie just do a masterful job of taking down the entire RFP mentality.  In the audio world RFPs are common to music composition (even if they aren't labeled as such), and so many musicians make their livings writing and pitching music for free to committees on corporate boards.  Its also a dynamic that comes into play when pitching one's self as a sound designer for a project.

In the podcast, Mike illustrates that a good working relationship requires both give and take, not just give - and when you enter into a relationship where you'll be making emotional decisions you have to be able to figure out if you can work together. 

"it's more important to have people who can work together than it is to have like the smartest people possible" - Mike

"at my most pessimistic I think all of that stuff is an elaborate trap to make sure that nobody can be blamed if the project goes wrong" - Mike

"There's a huge difference to the relationship you end up having with a group of people, or even just the conversations you have when you're being called a 'vendor' and when you're being a design studio" - Katie

"There's something about the process that makes it seem more like picking a commodity than on creating a relationship" - Katie

"A 'vendor' is somebody who sells you things, and its the things that have the value.  A 'partner' is somebody who works with you, and its the working together that has the value" - Mike

"If you show up at an initial presentation with comps of what you're going to do for that company's site you are an idiot.  You are an idiot.  And you should be laughed at and you should be thrown out of the building and you should never get to call yourself a designer again, because what you're doing is making shit up out of your head and putting it in front of a client irresponsibly and passing that off as design work.   You have no idea what they're trying to solve, you have no idea what their internal mechanics are, you have no idea where they're trying to go in the next two, three years.  And yet somehow you've pulled a solution out of your ass.  And then you have the balls to take it into a presentation and present this as 'this is how we think, this is what we think you should do'" - Mike

"I think 'let me tell you how we approach design, ' and you can actually say 'let me tell you how we'd approach your problem'" - Katie

"This is a goddamn endemic with designers.  They are afraid to do the thing they know is right...I'll be sitting with a designer and going over some work and it looks dead.  It looks like they don't know what they're doing.  They're pushing their food around their plate. There's no joy in it, they're not trying things.  And at some point they'll say something to the tune of 'well if I were doing this my way...' and I'll just say nothing and let that silence hang like a Mike Daisey apology interview, and eventually they'll realize what they just said, and they'll get back to work." - Mike

"It's a really sad form of self-censorship, and it kills designers because they do crap work, and its also incredibly unfair to people who hired you to do this work because they hired you to do the best work that you possibly can, and instead you think they could think of." - Mike

anyway, I could transcribe the whole episode or you could just take my advice and listen to the podcast.  Also, don't follow @Mike_FTW on twitter, its a little too erratic.

-enjoy!