Recently got myself a decent Field Recorder and an LOM Geofón. Apart from picking up on the tectonic shifts in the Berlin Underground, I was planning to record some impulse responses of various metal gates, fences, scaffolding, etc. to use with convolution experiments.
For recording IRs I have had good experience with using Logic’s Impulse Response Utility, but for that you need a transducer to transfer the audio sweep to the physical medium. For a classic impulse response you usually use the air around you, so your transducer is a speaker.
Now, getting to the topic of the discussion - for metal you need an Exciter, which kind of functions like a speaker, but without the frame and baffle, and which transfers vibrations directly to the surface you attach it to.
I wanted to ask if any one here has experience with these kind of exciters, and especially with some that go deeper into the low-end of the spectrum. Recommendations welcome, and especially for those available in Europe.
Never mind how to drive them, I’ll figure that out, unless we’re talking lasers or something
Maybe that Hainbach could help here … I remember an installation he did in Berlin in an - I think - abandoned industrial building - where he excited a lot of mechanical stuff to create sound scapes.
Since he seems very open to share his experience, you might find it on YT or even direct contact could be successful …
I have used these a few times. They have a few different models, I used the “ghost” 3” type though there are others. https://vidsonix.com/vx_transducer.html
I also have one of these. It’s great for exciting objects (especially large or heavy objects) but it’s not very portable as it requires a minimum of 400 watts (max is around 1500w I think) to power it.
Usually I’ve made my own diy style. The simplest is just a piezo transducer. Same thing as a contact mic but wired to an output instead of an input. Works for exciting small, light objects with higher frequencies. A better but more involved approach is modifying a small speaker. There are several ways to do it but basically you want to attach something to the cone that will act like a striker when the speaker is placed against on object face first. The old classic is a wine cork cut to the appropriate length hot glued to the center of the cone. If you want a sharper attack transient a thumbtack can be stuck in the striking end.
I’ve done some experimenting with exciters, these two styles
Attached them to acoustic guitars, wood panels, ceiling tiles, pink board insulation, and cardboard boxes. They are super fun but I was never able to get gripping thumping bass out of them. A large cardboard box with a port worked the best for low end, even better than a large sheet of plywood.
My favorite way to use them was in an acoustic guitar. I had them in the guitar, wired in stereo to strap pegs/jacks, one on the front and one on the back. I used a pickup and effects and sent them through the audio exciters and guitar, like the tonewood amp or the yamaha transacoustics. It is surreal having chorus, delay and reverb in an acoustic instrument.
Even better, and something the commercial products can’t do, was playing my digitakt though the guitar and having it jab me in the gut every kick drum. Makes a great wooden “CRACK”. Great for resampling and recording too.
This video is insightful, and I think there’s a sequel
Thank you so much all. These are excellent suggestions.
I will add that for this particular exploration, I am not dependent on the metal medium transferring the soundwaves to the air for listening. Instead I am interested in the frequency response in the metal , and will additionally be picking up with a Geofón, which I expect to be great in the lower frequencies, but not so much in the upper range. Therefore looking for an exciter with great bass response.
Blurrghost’s Buttkicker does seem to do the job, but probably more power than I need, as well as not being that portable, when you take into account something to drive it.
It raised an additional question though. The metal parts I intend to record are in public areas around where I live. Think stairwell railings, entrance gate, scaffolding on a construction site.
As I am not creating any sound installation (on purpose), and in fact intend to bother my neighbours as little as possible, I expect to mount the exciter’s just for the brief period of recording. The Geofón has a magnetic attachment, so that’s easy, but a lot of the exciters seem to be designed for more permanent installation with adhesives.
I expect the answer to be to attach the exciter to a small metal plate, and then fasten that to the metal structure with clamps or something similar. Or one of those metal bands you can fasten with a screwdriver perhaps?
I’d be thankful to hear suggestions, if any one has insights on other temporary attachment methods with good frequency response?
Just for reference if you end up shopping for these they’re called “hose clamps”.
Attaching the transducer to a metal plate wouldn’t be my first choice just because you’re introducing another material that could influence your ir capture but it might be fine. As far as quick mounting it will depend on which device you end up with and what you’re going to mount it to. If it’s light enough and you’re only going to mount to ferrous metal (steel for example) you could mount magnets to it with epoxy. You could use some sort of quick grip clamp as long as the object being excited is thin enough for the jaws to fit around it and the transducer. The cheapest zip ties you can find (cut them with wire cutters to remove). Duct tape? A trucker’s hitch tied in an old shoelace?
Huh, just picked up 2x Visaton EX 60 transducers and I’m itching to use them. Full-spectrum, less of a low-end focus.
I’ve been trying to figure out interesting resonators or resonant materials (would be nice if I didn’t have to hammer my own bronze at home, of course)
Clamps would work well, my exciters are almost unusable after all the applications of double sided tape. To be fair, I used the strongest tape I could find but found it necessary
