Introduction: Ribbon Microphone Upgrade for MXL 990
TL;DR – 3D printed ribbon bracket, 3D printed transformer bracket for MXL 990 Mic, along with a Ribbon alignment jig for a www.diyribbonmic.com/parts ribbon element.
BTW, this is the condenser version of this MXL mic. Apparently they have a ribbon version too in the same body.
Update 20160123: I continue to learn, and have found that using 22lb copier paper instead of parchment paper yields a much more pronounced corrugation in the ribbon. Also, in place of the brass nut, I switched to a brass tube, so I can rotate the tube to help align the ribbon. My initial idea of the nut was to prevent you from being able to rotate it, but I have found you need a way to help center the ribbon.
I’ve been a long time audio buff and musician, who has a little recording studio in my basement. It’s always fascinated me how expensive “good” ribbon microphones were, yet their construction was terribly simple. If you traverse the web, you’ll see I’m certainly not the first to go down this path of homemade Ribbon Mics. There are a number of good resources out there on the series of tubes. But of course, I’d like to think I’m a little different, and you can be the judge of that. My approach has been to use cheap microphone bodies and upgrade, rather than making a body from scratch. This has some limitations with respect to the dimensions of the body, but I think it gives a much more professional look. At the same time, you now have to convince someone that the guts in that MXL is a whole lot better than they might think. But once they listen to it, I think they will be able to make that judgement themselves. In addition, with my new 3-D printer, I figured I could design and print anything I might need to help the process, and it seemed some tools and jigs were missing from all of the other posts I had seen.
Starting with a Kit
What started this journey for me was running into Rick at www.diyribbonmic.com/parts (sadly, it was more than a year before I could finally get the time to finish this project). I saw he had everything you need to make a Ribbon mic element (motor), transformers and even a complete mic, along with an excellent set of instructions and videos. He was very easy to communicate with, and I had numerous emails with him before I even bought the kit. But to save some time and cash, I wanted to upfit an old MXL mic.
Being an engineer, the first thing I did immediately after ordering my kit, was to look how to improve what was already a good thing. A couple of things immediately struck me. 1st was that no matter what, I knew full well I would need to eventually re-ribbon the thing. And I wanted to make that process as easy as possible. And I wanted to be able assemble and disassemble the mic cleanly. So I started to work on some 3-D Printed parts.
But before you get started you will need to hit Rick’s site at www.diyribbonmic.com/parts and buy the ribbon motor kit and his OTA transformer. You will need an MXL 990 mic, and the 3-D printer files on thingiverse.
Why MXL Mics
In a word, they’re cheap, easy to find, and many folks buy them as part of their 1st studio equipment, to then end up tossing them in the back of the closet somewhere as they move on to get better quality gear. So they are good candidates for cannibalizing for upgrades. While ripping the inner layers of mesh out of the basket is a bit of a pain in the butt, you can’t beat them as a nice mic body as a base for an upgrade. And they most often come with a decent shock mount. I often find them used for less than $50 each on craigslist, and found 4 for $25 each. Sticking a quality Ribbon Motor and Transformer into one, quickly turns them into sounding like a mic costing $1,000 or more.
1st is a Series
This is in fact the 1st in a series of Instructables, with adjoining 3-D printable files to either upgrade or entirely build a Ribbon Microphone. Since it’s my first, I’m making it fairly detailed. The ones that follow won’t be as long.
This Instructable is to take a ribbon microphone element (motor) from Rick at www.diyribbonmic.com/parts along with his OTA transformer and upgrade an MXL 990 using some 3-D printed fixtures and tools.
Over the coming months I will be offering up other Instructables. I have recently completed an upgrade for the MXL R144 Ribbon Mic (Ultimately, I plan to build in a phantom powered preamp into this body), and will shortly be working on similar upgrades to the MXL R80 Ribbon Mic. All this will ultimately culminate in an entirely 3-D printable Ribbon microphone (active, with a Phantom powered preamp), which I also hope to CNC a metal motor. They will come in time.
Step 1: Needing Some Tools (Here’s Where Some CAD Skills and a 3D Printer Helped)
When I traversed the web, what seemed to be missing, were some tools that would make things much easier to deal with ribbon prep, installation and the final build. And that’s what I wanted to accomplish in this Instructable. Some things I realized would make things so much easier.
- Cutting Guides – Terribly simple, but really necessary. You need to cut the Ribbon straight and of a particular width. So I fired up InDesign, and made a very simple cutting guide of parallel lines for different Ribbon Widths. I also added a page for cutting some parchment in 20mm wide strips, so you can make pocket carriers for the ribbons, after you cut them. In addition to a cutting guide to trim the ribbon foil into smaller pieces, so you don't waste it.
- Paper Ribbon Carrier – Again, a simple set of parallel lines 20mm apart to cut some 22lb copier paper, to allow you to fold it in half, and gently tuck your ribbon into it so you can corrugate it. Once you cut your ribbon, you need some place to gently stow it, before you corrugate it. NOTE: Don't try to crease and fold it by hand, it ends up putting a curve in the carrier. Fold the carrier over a straight edge, like a ruler and fold it that way.
- Plastic Tweezers – So much easier than toothpicks to move the ribbon around, although, you will still love to use those toothpicks in some places.
- Toothpicks - Rick supplies some toothpicks in his kit, and they actually come in very handy in gently moving the ribbon around in addition to using the tweezers
- Glass – Since I have a 3D printer, I always print on glass, and found it so much easier to cut the ribbon on glass. 1st tape down your ribbon cutting guide, then some parchment paper, then lay the foil on the parchment, and top off with another layer of parchment paper. I also just used some picture frame glass.
- Ribbon Alignment Jig – This 3D Printed part is probably the single most important thing I made. Getting the ribbon properly aligned and tensioned in the motor is really tough when you just lay the motor on your desk, and try to do everything free hand. This jig allows you to place the Ribbon Motor in it, than drape the ribbon element across it to more easily align it, and put tension on it. I used brass nuts, to hold the ribbon in place, and used a toothpick to slide them (the brass nuts) around to align and tension the ribbon. The ribbon really needs something to help keep it aligned. This really did the trick. Then tighten up the clamps to hold the ribbon in place (one end 1st, make final adjustments, then the other end). If there was any one thing that I was happy about, it was this jig. I literally was able to use my very 1st ribbon and got it done in like 5 minutes. I attribute it to this tool. After working on some other ribbon motors, I came up with a simplified version. Both versions are included for download and print.
- Ribbon Corrugator – In traversing the web, I learned that corrugations of 20 or so per inch were optimal. I tried to 3D print some gears to that specification, but the teeth are just too fine for my 3D printer (a friend’s got an SLA, I might hit him up). And again hitting the Internet and various Ribbon Mic sites, I came across a very simple arts and craft corrugator, which works perfectly. I of course wanted to 3D print some fancy contraption for it, but the simple device works just fine.
- 3D Printed Ribbon Motor Mounting Bracket – Again, my biggest motivation here was to create a means to allow the Ribbon Motor to be easily removed to be re-ribboned. This is what I ended up with. This is a little recess in the bottom so the copper strip has room, and little channels in the back, so you can press fit the positive wires in place.
- 3D Printed Transformer Bracket – Again, rather than just use some stuffing to hold it in place, I wanted something a little neater. So I came up with a similar looking bracket, where Rick’s OTA transformer slides into. This rotates the transformer on its side so the 2 ribbon motor wires go up through the holes on the same side to connect to the motor on the back. It also has a bit of a stand off, to move the transformer further away from the motor, so the magnets don’t effect it as much. It makes wiring things up easier.
Step 2: Parts List
- Ribbon Motor Kit and OTA transformer from Rick, you don’t really need the full MXL 660 upgrade kit, as you will use my 3-D printed parts, just email him for the two parts, he’ll hook you up. (No I don't have any affiliation with diyribbonmic, just found his motor on line, got it, liked it, and found Rick to be a great guy)
- 3D printable ribbon fixture jig, motor bracket and transformer bracket
Step 3: MXL Mic Disassembly
Basically, you just want to strip it down to where you only have the case, XLR connector and basket. The mic basket has 3 layers of grille material. You really want to remove the two interior layers
- Unscrew the black base nut at the bottom of the mic. This is used to trap the non-shock mount, but also helps hold the thing together.
- Once that has been removed, you can then unscrew the upper and lower halves of the mic.
- There are 2 screws that hold the basket to the metal plate. Unscrew those, and the basket will come loose, revealing the condenser element.
- Unscrew the condenser element, and cut the wires. Hang on to the element, as you will need that little solder tab for a ground tab later.
- Cut the wires for the XLR connector close to the circuit board, and remove the circuit board.
- Loosen the screw that is holding the XLR connector in the body, and let it drop out. Desolder the + & - wires from the XLR. You will also need to add a new chassis ground wire later.
- Grille – OK, this is a little bit of work. The grille on the Mic has 3 layers. Now on one hand you can just leave it alone, but it does impact the frequency response of the mic. Therefore, I suggest you remove the inner 2 layers. This is a little tough, as the layers are soldered in a number of places. I used long nosed plyers and some long necked wire cutters. But if you are patient, you can completely remove the 2 inner layers. One thing to point out, is that in removing the inner layers, you may deform or pull down on the top of the mic grille. The ribbon element has some tight tolerances. So make sure you take a screwdriver handle and push up on the inside of the grille to again return the top to where it is curved out. You don’t want to have the top of the ribbon element touch the grille, as it will short. Ultimately, if you don’t trust the clearance, you can use a piece of electrical tape.
Step 4: Putting It Together
Let’s first get the Mic body prepped for the new ribbon motor (element)
- You will need to drill 2 holes in the metal plate (that the condenser element was mounted to), to secure the 3D printed ribbon element bracket and transformer holder. I would suggest that you use the transformer holder as your guide. Place the transformer holder aligning it with the 4 large center holes in the plate, and use a punch to mark your 2 drill holes. Drill to fit a 4-40 or similar size screw. Don’t forget to deburr.
- Using a film of silicone seal on the bottom of each bracket, secure the brackets to the metal plate. I would suggest screws going through the ribbon element bracket, with the nuts on the transformer side.
- See that little Intent in the bottom of the blue bracket? See the little grooves in the back of the bracket? Those grooves are for the plus (+) wires to sit into. This is the BACK of the MIC
Step 5: Wiring Up the Transformer
- Before you wire up the OTA transformer, you should test fit the transformer into the bracket, to make sure it’s not TOO tight. You may need to use an Xacto blade to shave it a bit. But you do want it very snug.
- Now you need to prep the OTA transformer. Solder a 6” black wire to the mic input – side, and TWO 8” red wires to the mic input + side of the transformer. Then heat shrink. 3/32” heat shrink for the single wire, and the 1/8” heat shrink for the plus leads. Don’t make the heat shrink too long up the black or red wire, as you need them to be pretty flexible close to the metal plate.
- You will then want to wire the transformer up to the XLR connector. If you haven’t done so already, loosen the screw for the XLR connect in the side of the mic body. The XLR connector should drop out the bottom of the mic body.
- The output wires of the OTA transformer are plenty long, in fact you can see if you might want to trim them a bit. But I left mine alone.
- Slide some heat shrink tubing up the transformer wires, and put the wires THROUGH THE MIC BODY
- You need to run the wires through the mic body BEFORE you solder them to the XLR connector. Then solder the red lead to the + pin, which is pin 2. Solder the black lead to the – pin, which is pin 3. Slide the heat shrink over the pins, and shrink with a heat gun.
- Now, while that XLR screw you loosened to drop the XLR connector out of the body should provide ground for the mic body, I went ahead and soldered a ground wire, that I then connected to one of the mic body screws just to be safe. It should look like this
- Now twist the transformer output wires a bit. Insert the XLR connector back into the body, making sure you properly align the connector with the key slot and tighten.
- First check the orientation of the Mic brackets. Remember that little notch in the bottom of the ribbon element bracket? See those little channels going up the bracket? Those are for the wire to sit in. That’s the BACK of the mic. Take the red and black transformer input wires, and slide them through the hole in the back of the bracket. Next put a little blob of silicone seal in the transformer bracket, and you will want to insert the transformer into the bracket so the back of the transformer, with the 2 mic input wires face the back of the mic. Slide the transformer in. It will be a tight fit. It’s supposed to be.
- Next loosen the side screws on one of the metal arms on the bottom mic bracket, and slide the metal plate into place. Twist the transformer wires a bit as you go. Then install the 2 screws to hold the metal plate in place, and tighten up the side arm screws. This is actually where I connected the ground lead. I used one of the solder lugs from the condenser element for the ground.
- Now the black wire will be soldered to the bottom center of the ribbon element. What I did was pull the wire back out, and trimmed, stripped and tinned it. The red wires will go up the channels on each side of the bracket, and to the center top of the ribbon element. What I did was push them into the channels, sorted out where center approximately was, and then trimmed, stripped and tinned them.
- You are now ready to install the ribbon element.
Step 6: Putting the Ribbon Element (Motor) Together
Follow Rick’s instructions (pages 9 through 13 of his instruction PDF) for building the motor. Glue the two magnets in using the spacer, with the proper polarity. Remove the spacer when dry. HOWEVER, do not solder the connection wires to the motor. You will solder the motor while it is in place. But you can tin the copper. But remember to mark the back of the body with a nice red plus + sign to indicate the plus end of the element. It will make things easier later.
While this picture doesn't show it, you need to put the 2 copper strips on, one at each end.
Step 7: Prepare for Dealing With the Ribbon Using the Cutting Guide PDF
- Use the ribbon pocket guide to 1st cut a number of pieces of 22lb copier paper. This will create 20mm wide strips. First cut a strip of 22lb copier paper to be about 145mm wide. Tape the cutting guide onto the piece of glass, and then tape the 22lb copier paper on to the glass on one edge, and using a steel rule (cork side up if it has it), using a brand new exacto or razor blade, cut them into strips. These will give you 20mm wide strips, which are around 145mm long. Don't try to fold and crease them by hand. The paper will end up with a bow or curve in it. Fold them in half long ways, using a straight edge. You will use these as pockets to place the recently cut ribbons into them.
- Select and cut the ribbon cutting guide. There are several difference sizes to choose from. The closer the ribbon is to the magnets the better, but you don’t want the ribbon to actually touch the magnets. While Rick suggests basically a 4.75mm wide ribbon, I’ve found that using the ribbon alignment jig, I was easily able to keep the ribbon centered, and have been able to easily do 5mm and carefully 5.25mm wide ribbons. So pick the ribbon cutting guide you want to try, and tape this to the glass.
- Then tape a layer of parchment paper on top of this. Keep a spare layer of parchment trimmed to fit on top, as you will want to put another layer on top of the foil before you cut it.
- Take a second piece of glass, and tape the ribbon sheet cutting guide to it, then tape a piece of parchment paper. Have another piece of parchment paper ready. You will use this piece of glass to trim up the big sheet of ribbon foil to a smaller size.
Step 8: Cutting the Ribbon
Here too, there is some finesse in cutting a good ribbon. I've seen that Rode uses a laser cutter. You need to be gentle with the sheet. You don't want folds or creases. You need to make sure you have a nice set of parallel lines. The edges of the ribbon shouldn't be ragged, but nice cuts. You need to hold the ruler firmly on the ribbon, to ensure no part of the ribbon shifts while you make your cut. I found that I wasn't holding the ruler down well, and a part of the ribbon would shift, making it skinny for a little section. Maybe a thicker piece of metal would be better to hold it down. That's why it's always a good idea to cut multiple ribbons at one time.
Also - Practice. You can use some standard kitchen foil (thinner in this case is actually better), and you can try cutting ribbons of different widths, so you can sort out which size makes sense for you to use.
- Turn off all the fans, close the heater vent, put the dog outside, kill the cat (Geesh, OK, I like cats) close the door. The slightest breeze will send the foil flying.
- Put the surgical mask on
- OK we have a branch in the process:
- If you are using Rick’s foil material, you can leave it in the thin parchment paper, as it cuts OK.
- If you are using the foil from Lebow, I have found that when you cut the foil in the parchment they provide, it sticks on the edges, and can tear the ribbon. So if you are using Lebow foil, I suggest removing the foil from their parchment, and use kitchen parchment paper.
- Tape the parchment on top
- Using a fresh razor or Xacto and steel ruler (cork side up), cut the ribbon material.
- Take the extra ribbon material and put it back into its parchment and store.
Step 9: Corrugating the Ribbon
Take the ribbon, in the carrier, and in a nice steady motion, while applying decent pressure on the two gears, corrugate the ribbon.
Don’t pull on the paper, rotate the gears and let the gears do the work of pushing the carrier and ribbon through them.
I have found that trying to do this all in one motion is best, as you can see the places in the ribbon, where you may have stopped. (Hence, my next project to improve this corrugator)
Step 10: Mounting the Ribbon
Yes, there is some finesse in properly installing, centering and tensioning a ribbon. You will get better at this the more you do. Which is is why I make the cutting guides and Jig, so it is easier to replace a ribbon, whenever you want.
I also initially started out using Brass Nuts to hold the ribbon down, and help center and put tension in the ribbon. However, I'm now using a brass tube (a piece of 1/4" brass coupler with the nut removed). I will probably try to find a piece of brass rod. I've also found that the top of the Alignment Jig isn't as smooth as I would like. What you want to have happen is to have the ribbon stick to the brass rod, and slide on the plastic. Sometimes the opposite happens. I'm thinking if I switch to a brass rod, and even just making it moist will help. I'm still trying to improve the process.
- Have the Ribbon Alignment jig already printed.
- Cut 4 pieces of 3m double back foam tape into squares about 5mm and put in the indentations of the ribbon alignment jig. This holes the screws in place while you tighten them.
- Taking an edge of the exacto, remove any sharp edge on motor bracket and clips, which will go against the ribbon
- Clean up the motor
- Take some scotch tape and stick around the motor magnets to pick off any fine metal that the magnets may have picked up.
- Clean with some alcohol (don’t use acetone, it will loosen the superglue)
- You want enough tension to where the ribbon looks straight across the motor. You don’t want it to sag. But you also don’t want too much tension, to where you are stretching out the corrugations. You want to see the corrugations.
Step 11: Add Ribbon Motor to Mic Body and Final Build
- First, everything you do from this point is slow and gentle. You don’t want to trash the ribbon element you just installed. I’d still keep the surgical mask on, to keep you from breathing directly on the ribbon.
- Gently remove the Ribbon Element from the holder. You can pull off the excess ribbon from the ends.
- Look for that + mark that you made on the back of the ribbon element. That’s the top. Gently slide the ribbon element into the bracket. The copper strips will be in the back, and the plus is top.
- Carefully solder the minus (-) lead to the bottom. What I found was that some hemostats I had laying around were pretty non-magnetic, and helped hold it in place.
- Then press the red plus (+) leads into the channels, and solder both to the top of the element.
- My element stayed put just fine. But if you are worried about vibration noise, you can use a little dab of silicone seal on the top corners or a rubber band across the top to hold it in place.
- Grab the mesh basket, and slide the element inside and secure the basket with the 2 screws.
- Now grab the bottom of the mic body and screw it onto the bracket. Then the black nut.
Step 12: Final Test
Grab a cable, hook it up to your preamp, audio interface or mixer, and give it a try. NO PHANTOM Power. You will need to turn the gain up pretty high. What I recommend is to put an inline preamp close to the ribbon mic, so it has some gain before it gets to the mixer. A phantom powered in line preamp is perfect, because you can plug it right into the bottom of the mic. I suggest that you get one of the following
Rick’s Ribbon Mic Preamp from www.diyribbonmic.com/parts
Cloudlifter CL-1 - http://cloudmicrophones.com/products/cloudlifter-cl-1/
Triton Audio FETHEAD - http://tritonaudio.com/index.php?sectionid=4&option=com_content&task=category&id=17&Itemid=33
I'm starting with the Triton until I can get an "in mic body" phantom powered preamp.
Overall, I’ve been really impressed with the purity of the sound. It sounds great. I like that this let’s me quickly and easily re-ribbon when needed, and the alignment jig really makes installing a new ribbon a snap. I hope you have as much fun with this as I did.