Love the clickbait-ey thumbnail that belies a technical video containing electronic circuit diagrams and a detailed discussion of the physics of sound recording. Don't ever change, dude!! XD
I got a bag of Piezos, soldered those to cables just like that, and it worked well on the drumkit and a 1995 Yamaha mixer. We attached the pads with duct tape to the drums.
Thank you for making these videos and for all the research you are doing on contact microphones. Your passion resonates through everything you say and do which make these videos very engaging. I am looking forward to all your future content.
What I would love to see is a frequency response from your setup without any piezo disc in line. Output of your buffer directly connected to the input of the other buffer. That would show the "quality" of your measure devices. Otherwise thanks for your work! Kind regards, keep making sounds.
Some more videos I might make using this apparatus: 1) Piezo films vs brass piezo disks, which is better 2) What should I use to stick my mic to things and how does it affect the sound 3) why isn't 'what is the frequency response of a contact mic' a sensible question 4) pros and cons of different preamp designs.Let me know if any of these would be helpful.
I saw your video on why frequency response isn't a sensible question. It makes sense. The paper I read fixes the piezo to a 6mm piece or steel along with the preamp pcb. The disc, therefore, affects the recording. I dud hunt down a few disc's, of a variety of frequencies, from a specialist electrical wholesaler. They were very thin, some brass, some stainless steel. I tested them. They were better than the other large ones I'd found on ebay, for bass response. They also had a wider piezo electrical disc covering one the back. The main problem withem was that they were both very thin. The brass one needed a heat sink when soldering as it deformed slightly in the heat zone and the stainless one wouldn't solder. I used electrical conductive glue, with some epoxy over the top for mechanical strength. Both of them had a very thin layer over the piezo material that melted away very quickly compared to other generic types. I look forward to more of your videos. Really helpful
Hi great video. I have read a paper by a Foley artist who mentions picking piezo disc with a certain frequency response and using a preamp with at least 4mega-ohm input impedance. Old crystal mics that came with tube driven tape machines used this high impedance, no current inputs have anything near that. These two factors will give you a better frequency response. I have used certain guitar pedals with 1meg buffers, powered up and turned off. These were an improvement but not perfect. I have read another article about using piezo tweeters, because they're cheap and will "work" alongside a low mid/ woofer in a speaker, without a dedicated crossover, they're often used in cheap cabinets and have a nasty cracking sound. The article stated that actually they give a higher fidelity response. You need to choose one with a much lower resonance and use a crossover to filter out the lower frequencies. The result is much higher fidelity sound. I have connected a piezo to the tape head input on a hacked cassette machine during electronic experimental performances, although I couldn't find out the input impedance for that setup, audibly the bass response was greatly improved.
Absolutely correct! Getting the correct impedance on the input for a piezo transducer as a pickup Is an absolute must for decent sound. A piezo transducer used as a tweeter is really nasty around 4kHz. It is best to build a circuit to cut anything below 5kHz being sent to one used as a tweeter.
@Yoda8945 thanks for the validation, I've been putting together experimental machines and building budget large PA, for gigs for years. I'm self taught. I have always gotten good sound, loud and clear at gigs. Any idea what input impedance the tape head preamps have in tape machines.
@@stuartchapman5171 Unfortunately, I don't know that. My guess would be that tape head preamps would need to be really high impedance as the heads are really high resistance and very low output. You have given me something to experiment with. My information about the need for high impedance inputs was gleaned many years ago from Barcus-Berry, Peavey acoustic guitar model amps, and Schertler David amplifiers, all of which use very high impedance inputs for the preamps to tame piezo pickups. The Schertler David is an amazing sounding amp. I was introduced to it about 10 years ago when I did some live sound work for a harp convention. (Celtic, not harmonica)
Excellent, I look forward to more experiments and explorations in this vein! The thing is, piezos are dirt cheap, preamp eqs are dirt cheap as well, when theyre put together into a, "contact mic" package there tends to be superfluous cost for some reason.
Nevermind any relevant discussion on impedance matching. The Piezo is a super high Z device. It needs a ten meg input circuit, you are using much less than that. No wonder their is no bottom end. A JFET buffer with a 10 Mega ohm input resistor will work pretty good.
I don't have that operational. I use the PAM 8043 module!!! Could you give me some advice on how best to build and get results for this contact surface mic? Thank you very much.
Piezo ceramics have very prominent and wide peak at the resonance frequency that depends on their physical characteristics (size etc.) and what's more, if you deform the disc, unless the energy stored has a way to dissipate, it'll stay deformed until the stored energy will leak away naturally. Thus you must have a resistor, or some other way for energy to dissipate, at the output of the disc or it has no low frequency response to speak of.
This is a great video thanks Michael. Would using a Triton Audio Fethead do the same job as the zero gain amplifier? Also about other video ideas, I'd love to see one about making a diy Geophone. There's so little information online as far as I can see about making your own.
The Fethead looks like a cool device, it would be interesting to test it out. It almost certainly still has the poor bass response problem with piezos, because piezos just have very different electrical properties than other mics and therefore have different design considerations and consequently need dedicated preamps.
Kind of a dumb question but placing a pole near the origin (soldering a capacitor very close to the piezo) would flatten the freq response up to near the resonance peak, wouldnt it? It's kind of a common practice among cigar box guitar builders
Interesting question, but I don't think so. Placing a cap in series will create a high-pass filter which will make this problem even worse. Placing it in parallel will make a low-pass filter. This will correct the shape of the response, but by attenuating the high frequencies instead of boosting the low ones. I mean, if your sensor always outputs silence, technically the frequency response is flat.
Hi great friend. Can you answer, is that possible to build a diy contact mic that have flat responce from 20hz to 20khz? I saw some datasheet of the contach mic and their responce is very good.
I sell a couple of DIY kits over on my website metalmarshmallow.com which have very good behaviour between 20 - 20k Hz. There is a phantom-powered version and a non-phantom powered version. There are a number of videos about them on my other youtube channel, Metal Marshmallow @metalmarshmallowllc Having said that, the frequency response of a contact mic is not a well defined concept, because the sensor's behaviour changes when you stick it to something. The graph shown in piezo datasheets is usually measured with the disc suspended in the air, held up by a vibrational node with calipers.
You put tape between the two piezo elements, which would affect the sound. I'm actually not sure how to attach them together without affecting the sound to some degree. There would be muffling even if they were taped only on the outside. Then there's whatever effects the mounting, the container, the AD and DA converters introduce. Finally, to make generalizations about _all_ piezo discs, you'd need to have a much bigger sample size than just two discs.
The only people who really use contact mics are noise/experimental artists…. Hi fidelity isn’t the main concern tbh, if it was they’d be using some cheapo Behringer dynamic mics or even some condensers
They're "the only people who really use contact mic's" BECAUSE they're not high fidelity enough for anyone else, although that's not true because people do use them on acoustic instruments, often with a preamp.
very cool :O! I would love to see the effect of weighing it down in addition to the amplifier!. I have seen somewhere that the performance is much improved if the disk can be pressed quite firmly and evenly into the surface being measured. I guess you cant always do that depending on the surface :)
