DIY Bass Drum Microphone Uses Woofer Cone As Diaphragm

Anyone into audio recording knows that recording drums is a serious pain. Mic setup and positioning can make or break a recording session. One particular hurdle is getting a great sound out of the bass drum. To overcome this, [Mike] has built a microphone using an 8″ woofer in an attempt to capture the low-end frequencies of his bass drum. Using a speaker as a microphone isn’t a new idea and these large diaphragm bass drum mics have taken commercial form as the DW Moon Mic and the now-discontinued Yamaha SubKick.

The project is actually quite simple. The speaker’s positive terminal is connected to Pin 2 of a 3-pin XLR microphone connector. The speaker’s negative terminal is connected to the connector’s Pin 1. [Mike] made a bracket to connect the woofer to a mic stand, which in turn was cut down to position the woofer at bass drum height. The setup is then plugged into a mixer or pre-amp just like any other regular microphone.

[Mike] has since made some changes to his mic configuration. It was putting out way too hot of a signal to the preamp so he added an attenuation circuit between the speaker and XLR connector. Next, he came across an old 10″ tom shell and decided to transplant his speaker-microphone from the open-air metal rack to the aesthetically pleasing drum shell. Check out [Mike’s] project page for some before and after audio samples.

17 thoughts on “DIY Bass Drum Microphone Uses Woofer Cone As Diaphragm

  1. neat. I like that he didn’t just stop at “good enough” too.

    what if a voice coil were attached directly to the drumhead itself, provided you are able to fix a stationary magnet held just right inside the coil… how would that affect recording — is this something that is done in some setups?

    1. i like this idea – i may steal it.

      how about a small lightweight neo magnet glued to the centre (or where the beater meets the skin) on the inside to move in and out of an internally internally suspended coil?

      1. First thing I remembered when you mentioned that – Tim Hunkin demonstrated a loudspeaker using a small magnet (or possibly just a piece of steel) glued to the center of a drumskin with an electromagnet placed near it. Check out 6:00 here:

        (The Secret Life of Machines, the telephone)

      2. hmm.. well, however it is done, the idea I had was to record the drum itself–for those that maybe want to “fake” the accoustical performance later in post– or perhaps the preferred mic setup and equipment isn’t available at the same time the inspiration and motivation is.

        either way, I figured a traveling voice coil would be more “transparent” as it would be less mass to move, making it more capable of picking up on the subtleties and nuances of a broader frequency range and sensitivity.

        whereas a traveling magnet will take a bit more energy to move, which may be good for capturing lower frequencies only, or acting as some kind of mechanical noise gate.. but really, I think those kind of settings should be more on the mixer side of things.

        I’d experiment with this on my own, but I lack the training /skill in accurately playing/recording a drum kit, nor do I have any worthy equipment for recording where such an elaborate setup would matter– let alone a drum kit to play on.

        1. To me an important part of the microphone is to capture the sound of the drum as precisely as possible, so mounting the mic directly to the head would change the way it vibrates and change the tone/tune of the sound.

          However, I think it would be handy for live setups where you need things to be easy and most people would be drunk anyway xD.

  2. The sound of a bass drum ain’t the sound at just one spot. There are two heads on them. Sometimes the drum is at fault. I once heard an acoustic jazz set at a bar in town, sounded real good. Drums that have texture and sound not just a spike of sound. Two rooms away from the stage while in the men’s room I noticed deep satisfying bottom octave sound from the kick drum, the kind never heard in the rock world. High ceilings 150 year old bar, acoustic! After the show I talked with the drummer about this, he said PA guys couldn’t figure out his drum sound and how get it mic’ed. Those kind of guys expect the kick to sound like a cardboard box thunk, only real loud. I hear them dial in the kick first, they always hone in on that same sound. Rock drums are usually tuned up near to max to make them loud, a short loud spike. Lowering tension coupled with good mic’ing will give so much more sound to play with.
    I did this project of sorts years ago, but found tossing a PZM mic in with a pillow inside gives full sound where assault is not on the bill. Nothing in the way on a crowded stage. One punk band loud enough on their own got this treatment making up the needed bottom octave.

    1. Yup. Drum miking, especially the kick, is one of the hardest parts of recording even in a studio setting. Drums are very nuanced beasts.
      When I was in school for it, we spent 3 months solid on nothing but drum mic technique and recording, and we only scratched the surface.

    2. As with any other instrument, 90% of how a drum sounds is in the setup. I always found that it wasn’t that rock drummers tuned “up,” but that they weren’t tuned at all…and that everything is just a series of dull thuds interspersed with high-hat and a crash.

      A method I’ve used before when close-mic’ing live drums on a small stage is to use a parametric EQ (one per drum) during sound check. Turn up the EQ’s gain, rather substantially, with a fairly sharp Q (if possible), and sweep the frequency around as the drummer boringly hits that drum over and over until the fundamental resonance of the drum is located: You’ll know you’ve got it when the air seems to vibrate around you and the dull thuds turn into thunderous roars, and the rock-and-roll drummer grows a big grin and says “Man that sounds awesome!”

      Ignore the drummer. Turn the parametric’s gain back to unity, and keep the frequency and Q (if applicable) setting for later. Rinse and repeat for each mic/drum combination.

      It just takes a few minutes, especially if the drummer knows he’s going to be put through these paces beforehand. You’ve now got a tunable acoustic system, which includes the drums and the FOH PA and the microphone and the microphone placement and the room, and you’ve got it tuned to do nothing at all: It’s ready for action.

      Relax and let the show begin. During the course of the first song (which is where things -really- happen behind the board with a small stage), while you balance levels and correct the unexpected vocal sibilance that just showed up, listen to each drum.

      If it’s a dull thud (of course it is!), turn up the fundamental on that one using the pre-set EQ until the drum is suitably and literally ringing. Too much? Back it off a bit. You’ve got a resonance control — if you want big bottom, you’ve got a knob for that. If you want a bit of pitch bend, and you’ve got an appropriate Q, you can do that too: Just raise or lower the frequency until you get a bend in the direction that you think (as the sound guy, the singular person responsible for the end result) think is appropriate.

      Once you think you’ve got it right, which might take a song or three, walk the room: You should be doing this anyway, but unless you absolutely -know- the room because you’ve mixed there a million times before, it always needs walked.

      End result? With a steady hand and a careful ear, a crappily-configured drumset sounds impressive and stage-worthy. People dance. People smile and groove more than they did before I introduced this technique (same band, same bar, same board, same PA, same drummer — and regular bi-weekly appearances).

      Disclaimers: I’ve left out the bit about using the rest of your per-drum parametric EQ to find the upper harmonics and the mechanical thwack of a stick hitting a head and adjust appropriately, but this is a description of one part of one technique — not a grand overview of drum mic methods and pitfalls.

      This will not work on a big stage as it relies on the proximity of the FOH to the drums and the non-directional bass inherent of a bar-sized PA. On a big stage, with actual directional bass (subwoofer arrays, bass horns, etc), and real distance between the FOH and the trap set, there will be too much latency (think ping RTT) between the drum, microphone, FOH, drum, and microphone.

      But big stages tend to include drummers who are at least friends with a good drum tech, so it’s not quite as important there.

      Oh, and my favorite small-room or large open-outdoor (yep, only those two) drum mic technique? Hang a decent (not an SM-57/58) directional mic over the drummer’s head, aimed at the middle of his kit (somewhere right of the snare) and mid-way between the drums and the brass. Add one kick-drum mic (see TFA). And…done! If the drums are jazzy and nice and set up properly, it doesn’t need much/any EQ using this technique — it just flows. (and you get at least a half-dozen-or-so channels back on your always-too-small board!)

    1. I think it was, but as i understand it, this mic is additional and meant to capture the more extreme low end and/or admospherics.
      The trouble with drumkits is that you have to make compromizes where you place your mics. A genral rule of thumb is that the best distance for a mic to record an accoustic body is the length of the longest standing wave the accoustic chamber can support. But if you follow this rule with a drum kit, you can imagine that bleed from other elements is going to be a problem, that is why kits are close mic’ed and why getting the sound is such a pain.
      Luckily, adding more mics like yhis can actually broaden the recorded spectrum.

  3. This looks pretty small, could be easily portable, this got me thinking. Elephants communicate over distance using infra sound, below human hearing. This “bass mike” might be able to pick up the infra sound allowing researchers in the field to more easily track Elephants in the wild. Well, it could work.

  4. Taylor Hawkins (the drummer for the Foo Fighters if you didn’t already know) mics his kick drum this way. Well, this is probably only 1/3 of his mic arrangement. I think he uses one mic to pick up the hammer striking the drum head, another inside the drum (usually poking into the hole in the front head) and one like the Yamaha Subkick, but I think it is actually the NS-10 woofer that is used.

    Using that three mic setup, he is able to capture the full range of sound of the bass drum.

    On a side note, Taylor Hawkins is a BEAST of a drummer. He always looks like he is having the greatest time playing.

    Part II of my side note is that the Foo Fighters might just be the greatest rock band of this generation. Discuss.

  5. Nice project!

    I hope the project creator keeps innovating and documenting. The ideal is that he continues research and advancing the capabilities.

    There are a few points I hope that someone will give added feedback regarding (as I am not audiophile enough so ‘scuse my lack of knowledge, to some this might sound like ELI5 grammar and questions but it is useful for many to have a solid explanation basis beyond license plate rattling “watts” car speaker). First what would be the range of resistance pickup? (What is the frequencies it can hear and how loud does it have to be?)

    As speakers have a rated Ohm to “drive” & (consumer level?) Microphones typically do not (list it). Is there some sort of signal preconditioning/amplification that occurs in order to pickup more sound (turn up the volume)?

    Again correct/enlighten or scold me – Speakers are designed to not bust at first spike or consecutive spikes and in fact the higher output they are rated at handling the less sensitive the “quiet” amplitudes are audible. (example; Got some semi fancy headphones last holiday season for a really reasonable price, surprise. at full volume my laptop/ipod/cellphone can barely “drive” them, I needed to build a amp for them).

    The previous projects are really nice. The authors did great at identifying, documenting and addressing the technical details. And even go so far as to document how to calibrate the correct impedance.

    In regards to sound, I wanted to share this link. http://www.soundlazer.com/about-this-project/.
    https://ksr-ugc.imgix.net/assets/002/376/245/5638363de5925a6bf3bd51dbbf68e09e_original.jpg?v=1406997907&w=700&h=&fit=max&auto=format&q=92&s=c2c9d46b487f76917c2a2c84a3aac550.

    What are those? Looks like those components from a Arduino range finder ultrasound modules in an array. Yes, that is very much what it is. The long of it is that he probably sourced the parts in a small run hence the cost. Also something about the writing and his description puts me off. Not very open. His new project he discusses new amazing secret thin film. Which makes me want to punch him over TCP/IP. (More on super sekret film in a second)

    Fine. Why am I bringing this up? Ferrite core/Magnet and Magnet wire (Nichrome?) isn’t the only player. Piezo. Acoustic guitar players use for amplification. People also know about the dinky piezo speaker our computers and other small devices we use.

    Piezo’s are also used in some regenerative electrical charging concepts. (I.e. in the soles of the shoes) A quartz material that if fluctuated (bent, tapped, shaken) will produce an electrical current. I believe there was even a article on how certain agencies can supposedly use the 3d accelerometer in our phone to record conversations. (the science is sound but as far as a live reproducible example I haven’t google-fu’ed it in a long while).

    I’m bringing up Piezos because the NEWEST/Latest development is PVDF films. PVDF films do come in sensor packages. (meas-spec.com) however Measurement Specialties is a bit vague and doesn’t use the word PVDF as so not have folks lured away from their provided solutions ($$-$$$)

    Maybe the project author/innovator can combine separate but multi stacked PVDF films in ever widening concentric disks/rings for a full range directional pickup system.

    I’m tempted to purchase a bunch of older/standard piezo guitar pickups, cut them into hexagonals, link them up like a honeycomb and use bathroom/grouting silicone (should allow to vibrate freely) or epoxy (should it be rigid to conduct/pickup frequencies better)?

    Either way the best mid-range to high frequency microphone will be made by someone who contours the microphone to have sound/frequency channels that matches the sound/frequency channels in the human ear AND OPEN SOURCE IT.

    The best low frequency microphone? aka Feeling the bass in your chest. Designed on the sound cavity of the human lungs and open source that.

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