Bone Conduction Device

[Menticol]

Hello guys!

A girl friend of mine wants to attach a bone conduction device on a set of hi-fi headphones, as part of a gadget for therapeutic use that she's attempting to build.

So she bought this transducer from New Zealand (along with this product brief) and asked my help to make it work.

The problem is, I never worked with this type of transducers before!

Given the fact that she wants to play music with it, I don't know what kind of amplificator can power it (at that impedance!), if a filter network will be required, or even how are the device internals. That " IEC-5" connector also looks fairly obscure for me, so I don't know how to power up the component.

I hope any of you could give me a starting point, it will be immensely appreciated.


Here are the device specifications

Impedance: 68 or 500 ohms (nominal)
Sensitivity, free air: 100mW for 0.2G at 500 Hz
Perceived sensitivity: 25mW for 110dBSPL
Max input power (continuous): 250mW
Max input power (50% duty cycle): 500mW
Frequency response: 400 - 14000 Hz, refer graph
Connector: IEC No. 5 polarised or non polarised


And the frequency response curve, finally something familiar to me.
View attachment 68530

Thanks in Advance

 

[KeepItSimpleStupid]

You know that "bone phones" exist? https://www.audioboneheadphones.com/

or https://lmgtfy.com/?q=bone+headphones

 

[Menticol]

You will laugh the hell out of me, but no KISS, I had no idea.

Wait, Audioguru's joke about the third world arriving in 3... 2... 1...

Continuing with the answer, yes, it's embarrassing. In fact, when she told me about "hueso vibrador" (vibrating bone in spanish) I thought it was a slang word for an obscure therapeutic procedure or a sexual toy, not the transmitting medium for a transducer.

Anyway, the girl already got the device and my bet now is making it work. What can I expect after injecting an audio signal on that thing? A puff of smoke from the poor amplifier?

 

[KeepItSimpleStupid]

Something tells me it's only two pins with a 5 pin connector. Me thinks that you at least need at least a pin out and connection diagram and a source for the connector. It also looks like polarization may or may not matter. Kinda like speakers. Two out of phase isn't good.

There is no mention as to what happens when it's fed DC, and it doesn't look like you have to limit the frequencies to the band suggested.

I don't know if they intend the user to equalize the frequency response curve. i.e Use a DSP (Digital Signal Processor) . Beyond me.

The next problem is what Z is it 68 or 500?

Find out Z. I think you basically would want to drive this thing with an OP amp.

I don't feel like playing with the power formula's but it's only like 2.5 mA RMS for 50 ohms, so it looks like you can blow the transducer easily.

To give you an idea of where I'm familiar with: A power amp that has a 3A supply and an 8 ohm load can deliver 72 Watts RMS, but now you need to know what RMS voltage is also required to deliver 72 Watts. Knowing all of this, you can determine the peak currents required and the peak voltages required.

Then you can select an OP amp and a power supply. You might be able to use a rail splitter and a 9V battery or maybe two 3V Lithium cells.

Next, you need to know what the input will be. Standard audio, or say a headphone jack.

And I'll add this: https://www.head-fi.org/t/607282/headphone-amp-impedance-matching-basics-you-need-to-know

Not sure where to head and if the transducers as is are compatible with say a cell phone/MP3 player headset.

Anyway I heard of the "bone phone" probably 30+ years ago and probably from the "Sharper Image". These guys: https://www.sharperimage.com
110dbSPL at 100 mW makes it whopping loud.

 

[Menticol]

Outstanding answer KISS, Thank you!

Now I have something to work with