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Description: Surface transducers give you the awesome power to turn almost any surface into a speaker. They're essentially just a speaker except instead of a cone, the coil is attached to a pad that conducts the vibration into whatever you press it against. Hook it up to an audio source and press it against the nearest table, wall or cardboard box. You can even put it against your head and play music directly into your skull (the ultimate surround sound).

Note: We are waiting on a datasheet. However, these have a 4 ohm nominal impedance and can handle about a watt continuous.

Dimensions: 50mm in diameter, 31mm tall

Weight: 260 grams (0.5 lbs)

Documents:

Comments 67 comments

  • They are more expensive than normal speakers for a few reasons:
    1: Since there is no cone they need to incorporate some other way of keeping the coil centered and stable inside of the magnet. You can see the little spring arms in the photo.
    2: These are designed to impart energy into a surface while not having anything to push against; they use inertia to do the job. Consequently, these transducers typically are weighted to provide extra push.
    3: Because of both 1, 2, and the fact that these are intended to be mounted in any orientation, the springs mentioned in 1 have to be fairly rigid. To overcome this, the transducer requires a more considerably more powerful magnet to provide any kind of decent sound at reasonable power levels.
    They aren’t arbitrarily expensive, there is a lot of engineering packed inside of these little beasts.

    • Good points, but they don’t explain the price, you’re simply describing the technology. (In fact, your point #2 is flawed, they do push against something - the resonating surface - as proven by the L-shaped attaching arms as seen in the photo).
      6 months ago, I bought 4 25-watt surface exciters (with roughly similar physical dimensions to these) for about $6 each. The $6 price tag was not a sale price. Looking elsewhere on the net at this moment, one can find many similar units in the same price range. This isn’t new technology, there’s no justification for the price listed here, unless there’s some super-duper features not listed.

      • Let me rephrase then.
        Imagine you are wearing roller skates but for some reason you need to push a dresser across the floor. Assuming you’re in the middle of the floor and don’t have something solid to brace against, your next option is to add mass to yourself so that more of your applied force is imparted to the dresser. Newton strikes again.
        Also, metals appropriate for this purpose are expensive. Adhesives appropriate for this purpose are expensive. Rare earth magnets are very expensive. Engineers are expensive. Patent licensing is expensive.
        If you put all of that aside, it comes down to a simple phrase: “what the market will bear”. If nobody buys it, the price is too high.
        Besides, Rob has to keep the beer flowing in the break room :)
        Keep up the great work Sparkfun. I love that you have kept to your roots.

      • Usually you get what you pay for. And this unit looks pretty sturdy. Robert did a real nice tear-down of this gadget in the new product video, where you can see more of the product’s construction details.

      • These are significantly heavier and more solid than the ‘exciters’. They have a much larger magnet structure and more robust suspension.
        Given that, yes, they are more expensive than the exciters you find at parts express or elsewhere.
        You fail to mention to offerings by clark synthesis can be upwards of $500 each. There is a large price range and these neither fall at the bottom nor at the top.

        • Awesome, thanks for the clarification on these details, Robert (I was hoping you’d chime in anyways).
          The 25 watt exciters I have are also very solidly built, mine also have metal enclosures and steel suspension, and actually look very comparable in quality to these that you offer. And you’re right, there’s a huge price range overall for exciters/transducers - just as there are for “normal” speakers.
          However, at $20 a pop, these are priced out of the “experimenters” range, given that they have such low power capability. After 6 months, my $6 units still perform solidly.
          Maybe if I can scrounge up $20 I’ll buy one of these to compare.

          • Put your money where your mouth is. If you promise to do a video about them, or at least a good write-up with pics, I’ll send you a pair. Be fair and let people know what they’re getting.
            The wattage range is just being safe until we see a full datasheet.
            Let me know if you’d be down for the challenge.

            • Doing a comparison between these and what I’ve used would be somewhat difficult. Mine are (basically) attached to the joists in my crawlspace and I feed them sine waves at certain frequencies as a “whole-house capable” alert system - 25 watts is good for that; without knowing the specs for these, I’d be hesitant for fear of over-driving them.
              But if you want a stand-alone review, I’d be ok with that; though I’ve never done such a thing before, and am sure there’s others out there that are more capable and certainly more worthy.

              • Well, you would have them to play with if you could give them a good review.
                I wouldn’t mind them being broken, sometimes that’s the best way to figure something out. It’s your call. You have experience with other ones.

                • Um… I’ll push them to their limits for you. I’ve been playing with all kinds of audio components. I’ll even take lots of pics and write up a big blog post and maybe even do a video and put it on a pretty high traffic website if you send me a pair, hell just one. =)

                  • Thanks for the offer, but I think enough people have these in their hands now. I just wanted to get someone to review them initially when we started selling them so people could have a resource. There’s a good amount of information out there about them now.

                • Are these like the transducers that were sold on thinkgeek?
                  What kind of frequencies do you get from these?
                  The ones from think geek had no bass to them at all.
                  I would love to get a pair and review them :)

  • Sweet product here. Well worth the money to me. I am setting up experiments at a university and this thing is awesome. I connected it to a waveform generator and a power amplifier and ran it through its frequency range. It definitely has some of its own natural frequency responses. It wants to jump out of its mounting brackets when it hits one of them. I am using it to excite some long, thin rods of metal and I can easily hit both the 1st and 2nd natural frequency (normal bending and S-shape mode). I have an Abacus model and the data matches the FEA analysis well. One bad thing - all of the ones I bought previously have broken. The sheetmetal diaphragm broke right at the square corner near the screw mounting bracket. However :) I see that they have thickened this section and added some round fillets (basically eliminated the stress concentration and reduced the bending stress). The new ones should last a lot longer. Just FYI. BTW, I freaking love Sparkfun!

  • Just want to add my 2 cents. I just received one of these yesterday. Hooked it up today directly to a 1/8" jack and plugged it into my computer playing some music. Placing this thing all over the office/home has been a lot of fun! I am going to be using these in my Architecture/Fine Arts Masters thesis, and I can’t wait to really dive deep into this. I know there has been a lot of technical/practical arguments going on in the comments here. But purely from a creative/experimental standpoint, this thing is AWESOME!

  • Anyone know what the thread is in the tapped hole?

  • I’ve put 18W rms into it for several minutes. Gets mighty hot but hasn’t burnt out. I wouldn’t advise running it continuously at this level, but it’s quite robust.

  • This thing is very solidly built, no complaints about the price from me; well worth it imo. If anyone needs to know, the central post’s thread is M5 with 0.80mm pitch.

  • Given the great lengths that makers of “real” speakers go to to try to get wide, uniform frequency response, and the utter unpredictability of the radiating surface these units will encounter, it would be absurd to expect anything approaching high fidelity reproduction.

    For many uses that may be OK, but I’m not ready to trade in my home theater speakers just yet.

  • What is the xmax of the transducer?

  • I am thinking of an alternate use - wondering how long the ‘throw’ of the shaft is and how slowly it can be controlled - would a v-slow sine wave (60hz or so) result in the shaft moving in and out - am thinking of mounting it upside down and afixing one side of a small mirror to bounce a laser off of - with the right positioning and controls I am thinking that 2 will allow for xy control of the beam and could even allow for scanning… first a scanning flashlight powered by a laser and then later perhaps allowing for painting an image

  • Hey, I’m interested in knowing the material that the round rubber pad is made of. I’m trying to figure out whether that rubber is safe for strapping onto anyone’s skin.

  • Would this be mono or stereo?

  • I tried playing directly into my skull. Liked it!

  • Got one of these for Christmas. Wired it up to a 3.5mm headphone jack, and had a lot of fun playing stuff straight from my old iPod. With a large surface, like a window or a wall, it reached about the loudness of a person speaking. Later, I tried it out with an amp. Not sure exactly what I was putting into it (I hooked it up to the 8-32 ohm output), but this sucker was LOUD. Like shouting loud. I was afraid to try it on the window, for fear it would break it… but by my guess, on the wall it was about the equivalent of a 60-watt boom box. Might get me a few more, to mount on the backsides of walls for a surround-sound system… =)

  • Has anybody measured the frequency response of this thing, or do I need to wait for the datasheet?

    • I did some initial studies with these pressed onto different thicknesses of plywood. Check out the results: http://adamlaskowitz.com/blog/wp-content/uploads/2011/11/analysis_diagram-01.jpg

  • I would love to get a couple of these to review. I have worked with the Clark Synthesis Silver transducers, the Rolen Star transducers (both versions) and those cheap plastic bug shaped ones as well. I have tested them on a lot of different materials, including glass, wallboard, styrofoam insulation, MDF, foamcore and large sheets of plate steel (and likely some other materials I am not remembering). We have used various ways of coupling to surfaces (ie. screw mount, epoxy, double-sided adhesive tape and welded) I have used transducers in creating custom sound systems used in medium -sized gallery exhibits and live performances with 200 pound sheets of steel. We’ve done a lot of testing and would love to test these too. I’d be happy to publish the results as a comparison video if that would help folks here.
    I can even come by the SparkFun HQ to pick them up since I am local. Let me know!

  • Just ordered one and it works quite well. However, both the connection wires were damaged when it arrived - appears to be pinched at different locations, especially at the point where the two wires come out at the back of the transducer. I think the wires are not strong enough with weight of transducer(thicker wire probably required - although through hole diameter limits options). Have others found the same with wires.

    • I just received this item this week and noticed the same thing. My red wire was actually severed where it had rubbed the outer diameter of the transducer housing. Luckily there is still a good inch or so left to use, but both black and red wires have insulation damage near the point where they enter the housing. This is something that probably needs to be addressed, as some customer probably won’t be able replace them if they do break off there.

  • I’d just like to know how they sound. It would have been interesting if you had hooked one up to say, an MP3 player and set it up on the table. So we could compare it against your voice in the video. Maybe jrossetti will include a demo in his review?

  • Can I use these with the audio amplifier kit -STA540?

    • Indeed it will. That amplifier can drive a 4 ohm load(such as this transducer) at much higher power than needed(description says “about a watt”, but Robert says it’s a safe guess until they get the real numbers in).

  • Sort of an apple to orange discussion. The $6 NXT-type exiciters are low mass design, working best with lightweight free planes such as unsuspended gaterboard. SF’s mass exciter can move, gee, mass - making them useful for a wide range of applications beyond lightweight free planes. In the late 60’s I lived in a log house with two big mass exciters turning the whole house into a speaker - at about 100W each. BTW - you can get the WowWee paper guitar amplifiers for about $10 in any big-box store - NXT low-mass exciter, amp, battery holder and 6' stereo cable. BTW2 - HiFi guys spend big bucks for accurate high pass filters with a 20Hz cut-off because the rumble caused by a cartridge climbing a small warp in a record will peg their amps. It takes a LOT of power to make low frequencies audible.

  • Hmmm, this X-ducer looks like a likely candidate for bodging out an analog seismic sensor. Should be slam dunk setting it up as a perimeter security detector.

    • Seismic waves are very low frequency, so this might not be able to pick them up, since it was designed for (higher) audio frequencies. Amateur seismograph designs are similar in concept but on a much larger scale - think heavy weight on a pendulum, with a magnet surrounded by a coil of wire. The larger scale supports measuring the lower frequencies. But I think you’re right that you could pick up footsteps, give it a shot and let us know how it works!

      • Detecting footsteps is exactly the purpose I have in mind. Much like the U.S. military “AN/PSR-1 Seismic Intrusion Detector”.
        http://www.prc68.com/I/PSR1.shtml
        The real trick will be building a water resistant housing that’s also a decent resonance chamber.
        I’ll post what I I find when this arrives.

  • Robert, I don’t mind the price (probably will order one today), but it will be great if Sparkfun can offer different sizes. I personally saw similar one used in a aid for people with hearing loss. Basically what is done, they have a titanium screw into the bone and this screw is like a hook for such transducer.

  • Any word on what frequency response is like? Could it be used to create substrate-borne vibrations for behavior experiments?

  • Hmm, so is the reverse true? Could I make my surface a microphone instead of a speaker…

    • Probably, but I imagine that it would only work well if you were being yelled at by giants.

      • There are some good projects out there that basically tape a microphone to a large flat surface like a wall or table and use its sound transmission qualities to allow use as a gesture interface with the computer. (I’ve always wanted to implement my own version of that)

    • Yes, but you would need to provide a large surface (like a styrofoam plate) attached to it to capture the sound waves. You will also need a hefty amplifier to get a decent signal. A 4ohm winding probably won’t provide a large enough voltage to be read by a computer or a voice recorder.

  • how would i run the actual sound to this?

    • Yep, just hook it up like any normal speaker driver.

    • I hooked this up to the speaker output of my home stereo and that worked. Not sure if it is the ideal setup, but it did work. And anyway I think that is the intended setup.

  • any notion how much displacement (in mm) these can achieve?

    • Maybe 2mm at most if you let the pad move freely. It makes quite a bit of noise, though.

    • I bought one. I haven’t measured, but I’d say “not much”. Maybe 1mm? Maybe a few. They’re very rigid though. I haven’t tried just putting DC on them and seeing the extents, but in trying to move them by hand, they don’t move much.

  • I want to know if this will do Infra-sound.

    • Well, F0 is ~20KHz and frequencies significantly below F0 can endanger the structure of the transducer. At F0 ~=20KHz, this would be an “extreme tweeter”.

      Basically, no :)

      • Ok so there’s an F0 (530+/-30%) and an FO ~20kHz max. Confusion ensues.

      • I’m curious. I just read the datasheet looking for this info, and see the following:

        Resonance F0 530± 30% Hz

        That seems to be saying resonant freq is 530 Hz, +/- 30%

        Where did you see F0 is 20kHz?

        530Hz is some juicy bass, innit?

    • Do you mean ultrasound; audio signals too high for the human ear to hear?
      Infra-sound would be extremely low-frequency. I’m not sure what the use would be.

      • Infra-sound is indeed very low-frequency. Alfred Hitchcock used this “budding” technology on theater goers viewing the premier of “Psycho”. Infra-sound, most often in the range of 16 to 18 Hz is too low to hear, but not too low for the body to FEEL. The way the body “feels” this frequency range most ofter produces a feeling of unease, or dread, in the listener. Hitchcock knew this and had humongous speakers installed behind the screens of the theaters, capable of producing these VLF sound waves. They were used during certain parts of the movie to good effect.
        Survivors of large earthquakes often report such a feeling of dread slightly before, during, and after large quakes (aftershocks) that are attributed to these sub-sonic infra-sound waves in the earth’s crust.
        I know it takes a lot of energy to move a mass of air (or otherwise) at these sub-frequencies. One watt ain’t going to cut it.

      • sub-sonic. ie - subwoofer. frequencies below (or near the lower threshold of) hearing range are called subsonic.
        they can be useful since they don’t have directionality. you can use them to create ambiance (check Richard’s post above).
        However, Richard is wrong with one point. Sure, you need to move a lot of air to create very low frequencies. But, we’re not moving air here. With surface transducers, you can use minimal power to get a similar result. to get to 10-14hz, you need a 15" cone (for example) with an inch of travel and about 1kw. with a tactile transducer, you can get by with maybe 1/10 of the power for the same perceived output.

        • You are moving a surface, making it move air.

        • I think you’re talking about different things here. You’ll get the “same perceived output” only if you’re just talking about feeling the energy on a surface. The transducer is vibrating the surface directly, whereas a sound wave traveling through the air can only couple so much energy into the surface to produce that effect.
          However, this is not the same “perceived output” with respect to actual audio as a sound wave traveling through the air, and then interacting with the body. Nor can a surface transducer produce the same subsonic audio as a regular speaker perceived or not.

  • Yes, Chill_Bill has a valid question, the price is not proportional to the wattage, considering the comparable transducers out there on the web (such as on parts-express.com).

  • How come these are so expensive? Aren’t they just speakers with a pad instead of a cone?

    • Say, couldn’t I just make one of these?

      • yes. you can make anything if you have the right tools.

      • You can make most everything on this website yourself. That’s not the point though.

        • Well, the point is, it’s a strong magnet, some machining, and then a wound voice coil attached to a suspension system. Sure, you could make it, but I bet that you’ll spend way beyond $10 doing it.
          Actually, if you get bored…
          Get a normal speaker driver. Remove the cone. Fix the voice coil assembly to the basket of the driver, and BAM, you have a tactile or surface transducer.
          However, the voice coil won’t be rigid enough for much output, but still…


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