This is a small active loudspeaker designed to boost the sound output of a laptop or netbook. It's built into a 40-40mm waste compression coupler that also houses a small amplifier based on the popular TDA7052 1 watt audio IC. This IC is designed to run on 6 volts but it also works well on 5 volts, enabling it to be powered from a standard computer USB socket instead of a bulky mains adapter

40mm pipe couplers are actually 50mm across at their ends, which is great because loudspeakers are also available in this size. I looked at a few specs and decided to go for a mylar coned driver from Maplin. Mylar speakers are generally more efficient than paper, but I was a little wary as I had played around with them in the past and thought they sounded a bit shrill and piercing on the ears, but whilst I accept they're never going to have much in the way of bass response, this one from Maplin boasted a good top end of 20KHz and so was worth a try. There's also a data sheet available which can be found here. The schematic and veroboard layout are shown below

The circuit closely follows that of the IC datasheet, except the input resistor is replaced by a preset pot to match the input sensitivity of the amplifier to the output level of the audio source

Audio is fed into the speaker by a 3.5mm stereo jack plug with the two channels mixed down to mono using a couple of 680R resistors which just about fit inside the body of the plug itself. Power is supplied by a type A USB plug. Wiring details are shown below

The audio/power lead exits through a cable gland made from the cut down body of a 1/4" plastic jack socket with the contacts removed. This also acts as a mounting point for the amplifier which is bolted onto it

The pipe coupler provides most of the components for the enclosure with the extra bits being the rear panel and front grille. The rear panel can be made by cutting out a circular disc from the plastic lid of an old jar, and the speaker grille can be made by using double sided sticky tape to attach a small piece of weed control membrane to one of the two plastic washers that come with the coupler. The grille is optional but recommended because the transparent diaphram of the speaker looks awful without it

Before screwing on the rear panel, stuff some acoustic wadding into the pipe. I used cotton wool but some filling from an old cushion works equally well. This really does make a difference to the sound

So how does it sound? Well considering how tiny the drive unit is, not bad at all, and it has enough volume to fill a fair sized room. Yes the bass is non existent, but the little speaker exhibits remarkabe speech clarity making it great for listening to talk shows and podcasts