The first rule of CONTACT MIC club

My new HISSandaROAR library is officially released now and as it consists solely of contact mic recordings I thought I’d share some of the most important aspects of recording with a contact mic that I’ve discovered the hard way – through experience….

CONTACT04

 

The first rule of using a CONTACT MIC is not actually about the mic itself, its this:

1. WHAT IS IT PLUGGED INTO?

 

At a guess I’d say I own over a dozen piezo/contact mics of various forms, bought over the last dozen years, but only three of them deliver seriously useable results. And just one of those three ‘good’ contact mics cost ten times more than all the others combined, simply because the people who created them understood rule number one. Its not ‘just’ a contact mic, because the mic is only as good as what it is plugged into, and the only way to insure you get great results is to also match the preamp, and the only way to do that is to sell both as a package. I’m sure the reasoning behind this is very basic for anyone who has studied electronics but THIS ARTICLE spells it out…

 

“The problem with piezo guitar pickups and contact mics is that they are not well matched to typical audio inputs. By their nature they can generate a lot of signal, but they cannot drive a 50 kilohm typical line input. The pickup needs to work into a much higher impedance, typically 1 megohm or so.

The reason why these devices often sound tinny is because the piezo sensor presents its signal through a series capacitance which is small, typically 15nF or less. When wired to a normal 50 kilohm line input this forms a 200Hz high-pass filter, which eliminates the bass.

If wired to a consumer plug-in-power microphone input of about 7 kilohms impedance, the result is a 1kHz high-pass filter. Hence the reputation for poor bass performance…..”

 

YES, Its all about IMPEDANCE

I have seen people suddenly ‘discover’ contact mics. And by ‘discover’ I suspect it tends to mean ‘discover the work of someone else who has used one’ who then heads off to an electronics shop, discover piezo mics cost less than $5, buys one, plugs it in, gets a signal but then wonders why they don’t get the same results…. Well now you know, its all about the IMPEDANCE!!! Re-read that quote from the article above:

“When wired to a normal 50 kilohm line input this forms a 200Hz high-pass filter…”

How many times have I seen a piezo element wired up to a 1/4″ jack plug? Many, many times… And now that you know the above tech to be true, what will the results be? Unintentional high pass filter (aka small speaker syndrome) Take anything you’ve ever recorded or listened to, put a HPF on it set to 200HZ and have a second listen…. It suddenly sounds like its coming from a transistor radio from 1973. Great if that is your intention, but otherwise…..

 

 

The second rule of using a contact mic is more practical, it’s about attaching it. The results are often surprising – sometimes I’ve found a prop (this happened last weekend) and thought: “THIS will sound AMAZING with a contact mic” and then hooked it up & been thoroughly underwhelmed. What seems resonant & complex through the air may well be singular & far less interesting with a contact mic. But its when the reverse is true that things get exciting.

My old studio at Ropa Lane in Maupuia was originally owned by a metal company (literally, not the music genre) and when I took the lease they left some huge long I-beams in one of my warehouse spaces. When you lightly tap these 5m long beams they rang like bells, I loved them & couldn’t wait to get my contact mics out. But when I did they were WAY less interesting than through the air. I’m sure I’ll work out the pattern at some stage, but in many ways the mystery is actually a pleasant side effect. Not knowing the outcome means when you do stumble across a beautifully resonant body, time slows down… Recording this library for HISSandaROAR I’ve had many moments where through experimenting I’ve stumbled across a sound, and hours have past before I really became conscious again – I had a sore back for three days because of it. The situation generates what calls someone with a complex name I can’t remember calls ‘flow’ and the only other device that does that for me these days is my modular synth, but thats a different kettle of fish – I now know every time I switch it on, three to five hours will pass!

 

 

So if there is a rule 2 to CONTACT MIC club it is this:

2. YOU KNOW NOTHING

Keep an open mind & explore. A contact mic makes you look at the world in a different way, and for that alone you should be thankful. The flip side to those I-Beams I mentioned, was another prop I bought for practically nothing and hadn’t found a use for, at all – it was a slightly scodey stainless steel shower tray. The trick with it was suspending it so it was free to resonate, and one listen with a contact mic attached would make you wonder WHAT was creating the beautiful musical tones! It sure wasn’t what the literal description makes you think of, thats for sure!

No doubt I’ll think of more rules at some stage & continue this post, but also when creating the CONTACT MIC library I slowly developed a method for both creating and naming the sounds I was recording. Heres the analogy: when someone plays violin, you could happily define the sound created as consisting of four parts:

1. the human performer
2. the resonant body (the violin)
3. the activator (the bow)
4. the acoustic space

Any HISSandaROAR library you know is me, so I ignored part 1 but one aspect of using a contact mic that bears discussion is rule 3:

3. THERE IS NO ACOUSTIC

Check this video to see what I mean:

 

 

Until the drill bit meets the metal surface that the contact mics are attached to, there is no sound. You could hold a contact mic up & scream at it & record nothing! As with the drill that can work to your advantage. You don’t have to worry about extraneous noise – you could be listening to loud music and recording with a contact mic with zero leakage! But it is also a key factor in the use of the sounds – because there is no acoustic to help cue the listener what produced the sound, they appear almost more abstract. But due to their great resonance they work brilliantly as hidden components of complex composite sounds!

 

Also referring back to that list above, I became fascinated with parts 2 and 3. So maybe rule 4 is this:

4. SEPERATELY CONSIDER THE RESONANT BODY AND THE ACTIVATOR

With experience I collected up various activators (see photo below) and of course, only some activators would work with some resonant bodies… But it gave me a language & a mental model to use when attempting to identify likely candidates, and equally that is invaluable for the imagination.

 

 

Most of the resonant bodies and activators I used in the HISSandaROAR library are shown, briefly, in this video:

 

 

As far as low end goes, you can hear in that video some of whats possible. Heres some recordings of that big yellow half deflated balloon – the low frequencies created are beautifully expressive:

 

 

Rule number 5 isn’t really a rule but requires thought:

5. HOW DO YOU ATTACH A CONTACT MIC?

I use two methods, depending on the resonant body. First I always carry a roll of thin double sided sticky tape which works well if the surface is clean & flat. Its fiddly to apply and can be frustrating if the surface is dirty, because as soona s you move it you have to replace the tape, but when the surface is clean its my preferred method…. The other method I use sometimes is a product called BluTak – its intended for attaching posters to the wall, but it works well when the surface is more irregular or dirty…. It pays to always have both with you when recording, along with the always essential gaffer tape. In some extreme cases I’ve used Blutak between the contact mic and the surface and then wrapped the whole thing in gaffer tape. But you have to be careful as too much tape can deaden the very resonance you are trying to record…

 

 

Rule number 6 is

6. PLEASE DON’T EMAIL ME ASKING WHAT MODEL OF CONTACT MIC I USE

I’ll list the models below, just so I can forward this article any such emails in the future!

Most of the recordings in the new library were done with two Barcus Berry Planar Wave contact mics combined with & two of their 4000XL preamp. Here is a link to the Barcus Berry product page. I like the 4000 preamps they come with due to them being phantom powered and having a 12dB switchable pad. I could not have cleanly recorded some of the metal shrieks & creaks in the library without that pad!

 

 

The other contact mic I own is a Trance Audio Inducer, which appears has been discontinued (incorrect – see update below) but here is a link to the Trance Audio site. Their preamp runs on two 9volt batteries which I like less than phantom power but I prefer Trance Audios actual contact mic capsule. Here is a photo comparing the two:

 

 

There are many other types of contact mics out there, the first I ever heard of was the C-Ducer but the contact mic element seems a bit big & awkward for my applications… Feel free to comment with any others you have experience with?

 

Lastly rule number 7 is

7. LEARN THROUGH EXPERIENCE

A contact mic is like any microphone, you have to learn to use it… and (hopefully) you never stop learning! So in the meantime here’s a preview of the new library:

 

 

check out HISSandaROAR CONTACT MIC Library here!

 

UPDATED Nov 12: I got an email from Trance Audio: “We still custom make the mono Inducer System, and we also do a custom modification of our stereo Amulet System to make it more useful for SFX work. We don’t list these on our website as they are not stock items, but are happy to enquiries”

 

74 Responses to The first rule of CONTACT MIC club

  1. bluekun9 says:

    Tim Prebble = The Good Teacher

    Really, I have learned so much reading your blog.

  2. Pingback: HISS and a ROAR Contact Mic, Tim Prebble Explores the Lack of Acoustic

  3. eonomine says:

    wow, i just discovered this site through synthtopia, fantastic sounds mate and very useful info re: the 200Hz barrier..

  4. I use contact mics for certain things, but still learned from your article. And the sounds in your library, amazing. Congratulations for this release.

  5. Thomas Alf says:

    Great article and fantastic sounds, Tim! The balloon sounds are fascinating.

  6. Sacha says:

    FYI – Trance Audio are actually still making their Inducer, but it is made to order / custom item only. It took about 8 weeks to ship when I purchased mine last spring.

  7. felix says:

    Great article.

    One thing I’ve found with piezos is that a drop of superglue gives a closer connection and better transmission than double sided tape.

    Obviously this is only relevant if you want a piezo permanently attached to something, but the difference is marked.

  8. Pingback: Contact Mic Reel | Publique

  9. Cooper says:

    wouldn’t it be way better for all those sounds if you throw the foam away and let it vibrate freely?

    • tim says:

      sorry, what foam are you referring to?

    • tim says:

      do you mean underneath the prop? you should try it sometime so you know for yourself, but a metal object sitting on wood that is struck will rattle ie metal against wood, rather than freely resonate – try it sometime

      • Zach says:

        I have used styrofoam to mount metal objects for music… it works wonderfully. The acoustic sound is notably improved… and it provides and excellent surface for a contact mic. You can have multiple objects just sitting on the styrofoam, and the mic pics them up well. The first time I saw this it seemed counterintuitive. I believe the key to the good sound to be due to the lightweight (low-density) nature of the foam structure and slight rigidity of the polymer. But idk.

  10. Pingback: Clube do Microfone de Contato | Som de filme

  11. Guy says:

    Great article, will be very useful, although it needs some time to digest it all!
    I think that the complicated name you refer to (“The situation generates what calls someone with a complex name I can’t remember calls ‘flow’…”) is Mihalyi Czikszentmihalyi, and the book is Flow: The Psychology of Optimal Experience (1990).

  12. tani P. says:

    Great stuff! I use Silly Putty to stick contact mics to random stuff. Basically the same thing as Blue Tac.

  13. bassling says:

    Thanks, you inspired me to solder together a piezo rather than use the cheap clamp thing I’ve been recording with and it’s great:

    http://bassling.blogspot.com/2011/11/how-to-make-contact-microphones.html

    I looked into getting a Barcus Berry but can’t see any in the country and the shop I asked in the US reckon they don’t freight well.

    There’s always some bit of kit one wishes one had, eh?

  14. Pingback: Clube do Microfone de Contato | Som de filmes

  15. E. S. A. says:

    Late, as usual, but I’m delighted to have discovered this. A quick question, What do you use for a recorder? I have a Zoom H4n. Will this be compatible with the pick ups you listed above? And why do you use two of them. Thanks ESA

    • tim says:

      I use Sound Devices recorders – 722 and 744, as they have very clean preamps. I’ve never used a Zoom H4 but I understand they are not so good with very quiet sounds…. I use two contact mics because we have two ears

      • Marc Shulman says:

        Thank you Tim! . . . For a cool and informative article ~ I am an electric guitar player.. and I play in stereo, through two amplifiers.. because we have two ears! It’s amazing how much flak I get from recording engineers and soundmen!

  16. I love this article Tim. I’m gonna by few of those mics that you’ve mentioned. I’ve really liked the sound of piezo mics. I can see the difference hugely. Also wanted to say, that what if you’d combine contact mic with the X/Y couple for the acoustic feel if you want to get more of it. Since contact mic sounds dry like this, it would be amazing also for an attack of the sound effect, since it’s picks it up so different from usual mics. Cheers.

  17. Pingback: Contact Mic Field Recordists | Music of Sound

  18. Pingback: II. Contact Mics – Sound on Solid Objects | The Sound Design Process

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  20. http://www.youtube.com/watch?v=fXIeFJCqsPs

    i think this is who you were referring to when you said “flow”….

    and that lecture was PHENOMENAL!!

    I am having a problem building this “drawdio” device for the purposes of making a pool of water ‘touch-sensitive’ and contact mics are, maybe, a feasible alternative. Which is how i discovered your site. i wanted to see if i could use a contact mic to trigger a video black out using MAX MSP.

    thank you for reminding me of FLOW.

  21. Ames Newton says:

    Hello,
    I’d like to use contact mics with my (soon to be delivered) iPhone. Do you know which preamp/devices I should invest in?
    Many thanks,
    Ames

  22. Derek Heming says:

    Great page on contact mics, thanks for all the info. I just found an interesting contact mic that uses piezo-polymer film (PVDF)and also has a built in preamp/buffer circuit. It’s the Measurement Specialties CM-01B contact mic: http://www.meas-spec.com/product/t_product.aspx?id=5431 and it’s only $32. It has a nice freq response and it’s touted as being extremely sensitive.

    Nobody in the country has these in stock so I’m currently putting together a group buy with a few of my audio geek friends to curb their $25 handling and $35 shipping fees. I should have them within a few weeks from now and I’ll report back here what I think of them for hifi applications. Either way, I thought you might be interested in something that’s a little different from the norm.

  23. Ben Carey says:

    Thanks Tim for for all the sounds and advice.

    I have just recently bought a Cold Gold Buffered XLR Contact mic which should arrive in Sydney in the next week or so from Canada http://www.contactmicrophones.com

    Do you have any experience with these? I have a Zoom H4n that I’m to be using it with, and got this particular model because it had it’s own preamp so I didn’t have to rely on the H4n pres. Any advice with this type of contact mic and getting a clean signal with my setup would be appreciated!!

    Ben

  24. johannes says:

    hey tim,
    nice article, i really enjoy reading it.

    did the mics differ regarding its frequency respond?
    did you compare them?

    thanks, Johannes

    • tim says:

      not hugely….
      When I get around to writing a review of the new Trance Audio contact mics I will do a recording using one side of each – the placement creates such huge variance it is otherwise difficult to compare….

    • johannes says:

      with mics i meant the barcus berry and the trans audio…

  25. johannes says:

    didint see your reply, thanks.

    does the use of xlr on the bb result in greater signal noise ratio?

    • tim says:

      minimally maybe….. I never compared that aspect – balanced XLR should always be better but it is very short cable run, so not like running 30m of mic cable in an EMF dense area…

  26. Desmond says:

    hey there. I’ve been trying to get a watch’s ticking sound with a contact mic into arduino’s analog input. I can get heartbeat, but no luck with watch ticking. Any ideas?

  27. Desmond says:

    Well I have no idea how to do find the required impedance matching or required preamp. Contact mic is sensitive enough I think, because when I connect it to a Marshall amplifier, I can hear the watch ticking quite well. Also is there a way to use Marshall amplifier’s speaker output as my analog input?

  28. Tim , or who ever els ….

    Would you be open to trying this with the DAzzo pickup ?
    It has three walls that hear incoming sound waves in 360 .

    Thanks

    Teddy

  29. hanif says:

    Very interesting and useful. I recently discovered that by connecting
    a jfet very near to the piezo disc it acts as an impedance converter
    similar to the efect in an electret mic.This eliminates all the problems
    associated with low output impedance and preserves the low freqs.

  30. Andy Ancrum says:

    Have been struggling for years with the issue of how to get your beautiful sounding acoustic instrument to sound less than disappointing through an amplifier, and how to control feedback. I have just got to the stage of running tests, that is, listening to the same sound (the one my ears hear) through different kinds of mics. Attaching piezos to things, hitting and scraping things, singing into mics, piezos. Thought I was losing the plot, then I found your site. Cheers

  31. Pingback: Contact Microphone Techniques | . : . : . P a r t i c l e S o u n d s . : . : .

  32. Grant says:

    Can you suggest a good contact mic for picking up very very quite “sounds”?

    I am building an automatic safe cracker for a school project and I need something that can “hear” the “tick” when the correct number is dialed in.

    • tim says:

      i have included links to the contact mics that I use in the article, the only better one that I know of for very, very quiet sounds is the discontinued Sanken contact mic which used to sell for approx US$3,000

    • hanif says:

      The nikkei acoustics Contact Mic is ideal for this.
      Comes with amplifier which has audio filter control.

  33. david says:

    how would / does the best of the two worlds work together (the phantom powered barcus berry 4000 preamp with the better transaudio transducers) ?

    does the barcus berry pre work well with other piezo bender style mics too?

    does it provide gain or is it just a direct box? i only see a knob for monitor out…

    interested in the barcus berry pre, but not as interested in the barcus berry transducers (for the mounting difficulties you have already mentioned).

  34. iain says:

    Hey there Tim,

    I just wondered what that putty stuff is you use to attach the barcus berrys? Is it just blue tack? does it affect the sound much?

  35. Pingback: Contact Microphones | andrewlogie.co.uk

  36. Hey, awesome article. I have a Mackie Onyx 1620 board which has 1Mohm input impedance (the guitar buttons) on channels 1 & 2. Do I still need a buffer circuit or can I plug right into the board?

  37. Pingback: New HISSandaROAR Release! | Music of Sound

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  39. BJ says:

    Stumbled across a man on kijiji selling a pair and found this page. Can anyone describe results from an acoustic guitar?
    Thank you

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