How to transform a surface into a loudspeaker

Would you like to make every surface behave like a loudspeaker?

Don’t you want something you can bring with you to play music with, without having to carry boxes around?

Whether you can buy something like this, or you an you can make your own device! This is how I did it:

The transducer:

The core element of this device is a surface transducer I bought online here for around 20 euros. The product is also sold on Sparkfun, they even have a video showing how it is built. The transducer itself is quite powerful but it needs a fairly loud signal to be heard. I tried by just connecting an MP3 player or the computer to it but the music was far too low to be enjoyed. As my purpose was making it a transportable device, I decided to build a small amplifier to attach to it.

A picture of the surface transducer

The surface transducer I bought

The amplifier:

There are thousands of projects online for building small or big audio amplifiers (an example here). As I didn’t want to loose too much time on it, I chose an easy option: using the LM383 integrated circuit.

LM383 is a mono audio amplifier capable of outputting around 7W. In order to properly use it, you need to add some few components around it. There are plenty of examples on the web like this, or this, or this other one. Although they are very similar, I opted for this simple one which can output 8W and can work with 9V batteries.

The schematics of the amplifier

The circuit’s schematics, taken from http://www.reconnsworld.com/audio_8wattamp.html

I have soldered everything together, and voilà !

I have to say that the integrated circuit is quite powerful; it actually gets a lot of noise which you can hear clearly with headphones, but given that I am not aiming at high fidelity it’s OK for the moment. If the input signal is not very low (e.g. an MP3 player at its maximum volume) the output is completely distorted, for which, I have added a potentiometer to regulate the input.

A funny thing: if you connect the plug to some big conductive matter it starts amplifying AM signals! I noticed it while I was making tests: just by touching the jack my body was behaving like an antenna and the electronics would bring the signal to the base band and amplify it. Watch the video to see it working !

[vimeo 60908699]
Advertisements

2 comments

  1. Hello, Thanks very much for this information, it’s really helpful. I have got one of those transducers and have been hunting for just the right amplification for it for a while online… your blog has been great for pointing me at the resources I need! Cheers, much appreciated!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s