Hey Another one of my bizzare threads where I ask for help with something random Ok so, when my grandparents were younger my grandfather put together a box with a speaker for my grandmother so that she could listen to the radio in the kitchen. The speaker has been sat in the garage for probably about 40 years at the very least. Anyway, my grandfather recently passed away and my nan would like to be able to use the speaker again, sentimental value and all. Trouble is, it doesn't have an amplifier, it's just a big ol' speaker, about 25cm in diameter or so? It works with my stereo and the speaker output on my pc subwoofer but she doesn't really have anything with an internal amplifier that I know of. My point is, could anyone instruct me as to how I could build an amplifier to put inside the box so she can use it with whatever she likes? It doesn't have to be fancy, she's not an audiophile and we're talking about a speaker which is at least 50 years old. Just something simple which will work adequately that I can build relatively easily and cheaply. Also please don't reply if you're going to tell me it's not worth the effort or telling me I'm stupid, I know it's possible, I would probably improvise something myself but I really don't want to risk fucking the speaker up so I want to do it right. So yeah, please help. Thank you in advance
It is far from "stupid". I'm not an expert on speakers by any means (I'm still in need of figuring out the impedance values and what mis matching does) but under the assumption that its absolutely nothing more than a speaker mounted in a box with wires going out the back you could try this: http://www.ecelab.com/circuit-audio-amp.htm R3 is where the volume is controlled, slap a potentiometer on there and you'd be golden. Or maybe this: http://www.electronics-project-design.com/AudioAmplifier.html What are you going to use as an audio source?
Ah great they look pretty simple, it is exactly that, a speaker mounted in a box with wires, there's also a potentiometer for volume in there already too which I expect I will re-use, assuming it's of the right value of course. I'm pretty sure she intends to use it with her bedside radio which has a tinny little speaker, so the source would be the headphone jack
Probably the best bet is to grab a cheap pair of powered PC speakers and rip them apart. IMO, you'll probably spend more trying to build your own small amp. But if you really want to build your own you could look at some LM386 based designs. Might not be powerful enough though for that size speaker though. EDIT: What APE posted seems like a great idea. ST offers free samples for that part too. Then you could just order the other parts for pretty cheap off eBay. I would shop around on eBay. A lot of times you can an exponentially greater number of components for a tad bit more than you would pay just for a couple. http://www.st.com/internet/imag_video/product/251883.jsp
Ah interesting, I had vaguely considered cannibalising some PC speakers but would rather not kill working speakers if I can avoid it. Also I don't think it needs masses of power, these are my exact speakers, http://www.argos.co.uk/static/Produ...htext>WHARFDALE.htm#pdpFullProductInformation I literally unlplugged the left 5W satellite speaker and plugged in this one in its place, it sounded ok to me
http://www.ebay.com/itm/230697901363/ http://www.ebay.com/itm/160842979643/ I would just go with one of those kits. Seems like a perfect and affordable solution.
Maplin do a fine selection of amplifier 'kits' - I believe they do 1W, 8W, 20W and 200W amplifiers, which are basically the board and components. Follow the instructions, solder in the included parts, and you're away! Before you buy one, first open up the back and check the wattage and impedance on the speaker - it's usually written quite large - the wattage obviously in W, and the Impedance written in Ohms (Ω). Then, pick out one that matches or is near to the speaker.
Yup, just get a Velleman kit from Maplin. Match the impedance, yes - although it may not be written on the speaker if it's very old! Wattage, to a certain degree, doesn't matter so much. Well, it does, but it's common practice for sound engineers to use amps more powerful than the speakers... but then again, they know what they're doing! Stick to a low wattage amp and you should be fine, but do try to match the impedance. Oh, and it won't be stereo, of course. So you need a mono amp.
A speaker that old would've most likely be designed to operate with a Valve amp, so it's probably a low wattage design with a high impedance (e.g. 12w / 16 Ohms). Assuming this is the case, you shouldn't really have any problems driving it with an amplifier specified for 6 to 8 Ohms. It will make the volume control a little sensitive, but you can always minimize that effect by turning down the control mounted on the speaker.
Right it doesn't mention the impedence or the wattage, if it had said so it would have made this a bit easier and I would've mentioned it before now haha. If it's helpful at all the potentiometer sepcifies that it is 22ohms
