#178

ah ok, interesting.

yeah that stuff is hard to cut and hard to fabricate. its function as an excellent shielding material is compromised if the continuity of the weave is damaged. but i’m sure you could figure something out that does a similar job. (standard woven shielding tube, for instance.) if it’s not mounted under a violin bridge it wouldn’t have the same structural stresses.

even with the kevlar, my PTW developed severe shielding issues after some years of sustained use (bridge slippage / adjustment abraded the surface eventually.) now i use integrated pickups built into a bridge “saddle” or the body of the instrument, which feels more reliable.

#179

Little question to those of you who use contact mics in a live situation. What are your strategies to minimize feedback / Larsen problems? So far every time I’ve tried to use contact mics live it has ended in a big feedback mess…

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#180

I’ve never had feedback problems with a contact mic.

What is it that you’re using it on?
Is it mechanically coupled to the amplification in some way?
Or super boomy?
Is the feedback low/mid/high pitched?

#181

I’ve used them on several things. Mbiras, kazoos, cigar box guitar, pieces of scrap metal (like CPU coolers), tape players, etc.
The cigar box guitar I can understand. The resonant body – and the strings via sympathetic resonance – likely are a good vector for feedback, but other things I don’t know.

The feedback is always in the mid high pitched area.

I have to note that the problem is mostly that the venues have a lot of reverb (think symmetrical concrete box) and that the volumes are usually loud, like in use-those-earplugs type of loud.
My guess is that past a certain level there’s no way to avoid feedback, but maybe I’m guessing wrong.
Maybe it’s because the sounds I try to amplify are sometimes pretty subtle and hence need a bit of gain to be made audible.

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#182

Hmm, it could just be the level of amplification is creating mechanical feedback with whatever you have it on.

Does it happen with different (types of) contact mics as well?
When it does happen does it stick to one ‘node’ (per object/situation) or is it wildly feedback-y (ala an air microphone)?

If always the same mic, it might be the resonant frequency of the contact mic you’re using.

It might also be worth testing with a parametric mid EQ to see if you can dial out a specific node (again, of either the mic or room).

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#183

if that doesn’t work to identify and correct the problem, i’d investigate three options:

  • disposing the amplified objects on some foam to avoid coupling with the surface (table etc.)
  • insisting with the FOH sound person on what the acceptable highest spl is for you. (some (most…) music doesn’t need to be 105dB (or even 95dB) loud.)
  • if all else fails, sample the tiniest sounds in advance (and find a way to keep the playing of those samples gestural).
2 Likes
#184

@Rodrigo and @ermina: some great advice thanks a lot both of you!

It does yes, but I mostly have the same type (cheap piezo-based ones) and they are usually firmly attached to a body, because otherwise they wouldn’t pick up much.

Not really sure what you mean here, sorry.

I need to do some more precise testing the next time I have a proper PA at hand (next rehearsals).

Or rather, what I am thinking is to just avoid live use of contact mics (or contact mics in general) in certain venues. There’s places where you can’t say: “let’s keep the levels low”. In these cases I think your next point, or even preparing things at home, is the right thing to do, even if it takes away from the performance aspect.

I have been thinking about it as well. I did a few shows where I would just use stuff I had sampled at home. It does make the whole thing a bit more static though, so maybe I’ll try to do as you suggest and do something in-between and maybe always incorporate that in all livesets (because you never know). Possibly I can also sample things with the channel on CUE (on the Octatrack) so I can hear what I do on the phones but avoid it getting out over the PA while playing. Most of the time I do sample/loop things anyway.

#185

It would be worthwhile doing some testing with a “real” contact mic (the fairly cheap k&ks are my go-to for most general purpose stuff). Some DIY ones are made around fairly shit piezo elements that are repurposed from being buzzer/beepers, so they are design to have strong resonant frequencies in the mid/high register.

Kind of relating to my last point. If the feedback tends to get “stuck” on certain notes/frequencies, that may be indicative or it being a resonant frequency of the contact mic itself and/or the room/equipment you are using.

What I sometimes do when I am purposefully working with feedback (though not with contact mics) is I “bleed” the room during sound check, by letting it feedback and finding what the problematic frequencies are, then using a parametric EQ (in software) to dial back those frequencies. This doesn’t get rid of all feedback (and in my case, I wouldn’t want to), but it removes the problem where some frequencies just dominate everything and/or lead to feedback when you don’t want it to.

2 Likes
#186

Good idea!
I do have mostly shitty piezos I have to admit. At least I guess they are, most of them I haven’t made myself. I only have one good one from Jez Riley French, but I haven’t used that one live yet.

That’s a great thing to do indeed! Thanks a lot!

#187

Just a note: looks like marshmallow’s back on the menu.

link

5 Likes
#188

Just spotted this while looking for some solutions for an upcoming project. Anyone tried them out? not as cheap as a DIY preamp option, but probably more robust. also being able to have a shorter TR cable on a piezo to keep it lighter and be able to use longer and have different length XLRs without adding noise is pretty appealing.

https://www.tritonaudio.com/bigamp-piëzo.html

#189

I tried this one. I can highly recommend it!
I compared it to a few different piezo pre amp solutions and it was definitely the best.

1 Like
#190

Anyone tried using MEMS accelerometers as contact mics? Looking for a high gain, low interference solution for a project.

https://www.analog.com/en/analog-dialogue/articles/mems-accelerometers-as-acoustic-pickups.html

3 Likes
#191

I totally missed this last week. That’s really interesting…
Unless I’m missing it, it seems crazy that that article doesn’t have any audio examples (even though they show waveforms and such).

////////////////////////////////////////////////////////////////////////////////////////////////////////////

On a different note (yet still contact mic-y), I was wondering if anyone had any thoughts on a possible solution for something I’ve been thinking about and working on a bit.

Basically I came up with a simple (clever-ish) way to “mic” a hi-hat using some 3d-printed parts in a way that’s non-invasive, and with some impulse response magic, sounds “usable”.

Checkit:

So this works well (enough), and based on how good this sounded, I’ve been experimenting with something similar for a cymbal/ride. I tried a similar approach (on the felt, under the bell) and it doesn’t really work on the ride. All the wobbling back and forth creates a constant phase-y/whooshy sound. (the hi-hat version has this too when I do a foot splash, but that’s not all the time, so it’s passable there)

The obvious solution is to have something that’s mounted on the cymbal itself, kind of near the bell or inner flat part, basically to minimize dampening the cymbal.

So the issues here are multiple. For one, having a low mass/weight contact mic and method of attachment to not dampen the cymbal. The k&k hotspot I normally use for this kind of thing is pretty small. The other thing is having it attached in a manner that I can still pack away the cymbal without a cable/jack dangling everywhere.

So the first main question here is with regards to mounting(/adhesives). Does anyone know of a good material to use here that’s strong, flexible, has a bit of thickness (so the contact mic can sort-of contour to the curve of the cymbal) and critically, isn’t too foam-y/absorb-y?

Second, and this is what inspired this post really, I was thinking that for easy of use and packing, that I would separate the jack from the contact mic, so the contact mic would be attached to the cymbal, but without a cable coming from it. So I was thinking of having some kind of compact/minimal jack, or plug, or connector. It would have to be sturdy enough so it wouldn’t pop off while playing, and low profile, so the cymbal can still pack away. Does anyone have any thoughts on this?

I was initially thinking those little dupont-style connectors, or perhaps even header pins, or some kind of locking header pin.

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Shielding might also be an issue here too.

So yeah, any general thoughts on the idea welcome.

3 Likes
#192

I wouldn’t trust duponts when there is vibration and movement involved, unless you plan to tape or hot glue them, which defeats the point I suspect.

RC Hobby connectors like Futaba J connectors might be a better option.

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#193

Yeah that’s what I’m thinking. A cymbal is a really wiggly beast.

Hmm, never heard of these.

So they are a bit dupont-ish but with some side slots?

Unknown

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#194

Pretty much, there are also more generic servo and RC power connectors. The “important” part is the male connector which has a shroud and should have a very snug fit. Try searching for “RC servo extension lead” and you will see what I mean.

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#195

Interesting.

Also just randomly watched A Quiet Place, and in it I saw that some hearing aids have a tiny connector that goes from each section. I tried googling what it’s called (I saw “RIC Socket” in some diagrams, but I couldn’t really find any useful info on that).

Something like that could be quite useful as it’s (presumably) sturdy, and also (again, presumably) shielded.

#196

I was also going to suggest u.fl or umcc RF connectors, I don’t know if they would stand up to repeated “pairing” well and it’s all designed to be SMD mounted.

I think mmcx connectors might be worth looking at, as they seem to be used on some high end earbuds. The official specs only rated for 500 pairings, but I’d expect real world use to greatly exceed that. In fact they look ideal, if you can find the male end at a reasonable price point!
SMA to mmcx pigtails might be an affordable option for the female end as sma connectors should be easy to buy and to work with.

2 Likes
#197

Man, you really know your “tiny connectors”!

images

I think this is an ideal solution! I can just have one end mounted directly on the contact mic, and the other end will be a ‘pig tail’ to a mounting bracket which will then terminate in a 1/4" jack.

Perhaps something like a right angle female jack, epoxied onto the back of a contact mic:
Unknown

1 Like