I have just built a RH84 style amp in a most electrically horrifyingly dangerous way on my workbench.
I've made this for somewhere south of $20 total in parts, so it's a bit of a junkbox special. The idea is that it is a small cheap amp for the computer or the dining room. Because of where I got most of the big parts (a 1950's stereo radiogram in very bad repair, for $11) I have discovered that the output transformers absolutely will not talk to any speaker below 16 ohms. I have tried my 8 ohm studio monitors and to say the sound is on the far side of revolting is something of an understatement, with those speakers the amp gives horrendous IMD, no midrange and fairly strange sibilance. I have a couple of 16 ohm eliptical fullrange speakers that indicate that the amp sounds pretty damn good, even getting to spookily good. They lack a whole lot in refinement and everything from lower mids down sounds kind of rubbish.
Which brings me to the point of my post. I'm after cheap, with the emphasis on cheap, half decent fullrange drivers that are small and half decent. If I have to use two per box to hit 16 ohms per channel that is fine, though I'll take recommendations on configuration. I don't want to spend several times the value of the amp, though a couple of multiples is ok. High efficiency would be good.
I'm better at cabinetmaking than I am electronics, and I'm better at electronics than I am speakers, so "odd" cabinets are a possibility, but I'll need advice.
What I'm after is the driver everyone calls "surprising".
Any recomendations?
I've made this for somewhere south of $20 total in parts, so it's a bit of a junkbox special. The idea is that it is a small cheap amp for the computer or the dining room. Because of where I got most of the big parts (a 1950's stereo radiogram in very bad repair, for $11) I have discovered that the output transformers absolutely will not talk to any speaker below 16 ohms. I have tried my 8 ohm studio monitors and to say the sound is on the far side of revolting is something of an understatement, with those speakers the amp gives horrendous IMD, no midrange and fairly strange sibilance. I have a couple of 16 ohm eliptical fullrange speakers that indicate that the amp sounds pretty damn good, even getting to spookily good. They lack a whole lot in refinement and everything from lower mids down sounds kind of rubbish.
Which brings me to the point of my post. I'm after cheap, with the emphasis on cheap, half decent fullrange drivers that are small and half decent. If I have to use two per box to hit 16 ohms per channel that is fine, though I'll take recommendations on configuration. I don't want to spend several times the value of the amp, though a couple of multiples is ok. High efficiency would be good.
I'm better at cabinetmaking than I am electronics, and I'm better at electronics than I am speakers, so "odd" cabinets are a possibility, but I'll need advice.
What I'm after is the driver everyone calls "surprising".
Any recomendations?
Cheers, they look pretty interesting, though they are a 4 ohm driver, meaning I'd have to run four per cabinet to make a driveable load for the amp. That puts the price somewhere out of range for this project. I'll probably need an 8 ohm driver at a minimum.
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In terms of 'inexpensive' I'm looking at these...
http://www.madisound.com/catalog/product_info.php?products_id=1502
and
http://www.diyaudio.com/forums/showthread.php?t=117698
http://www.madisound.com/catalog/product_info.php?products_id=1502
and
http://www.diyaudio.com/forums/showthread.php?t=117698
Well, they certainly meet the cheap criteria. How do they sound? They state extension to 16k, which is about where I can hear to, but I imagine it tapers off a bit before that. How do you find the extension?
Dont know if this small Vifa is real fullrange, but interesting small low priced driver
It even has a copper cap on polepiece
http://www.madisound.com/catalog/product_info.php?cPath=45_241_282&products_id=8403
It even has a copper cap on polepiece
http://www.madisound.com/catalog/product_info.php?cPath=45_241_282&products_id=8403
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you might also look here, this guy has measured a number of full-range drivers and has some commentary on them in terms of quality and value for money.
http://www.zaphaudio.com/
http://www.zaphaudio.com/
You might take a look at these Pioneer BU20F20-51F. Good write by Nelson Pass http://www.passdiy.com/pdf/cs-amps-speakers.pdf good bang for your buck.
Bill
Bill
These are the most interesting of the ones posted above, they are more expensive but they are 16 ohm, so I'll need half as many and they are available in Australia. The only things that concern me are the low-ish sensitivity (the amp probably does 2W or something, maybe not that big a deal for nearfield listening) and lack of response up above 13k or so. Perhaps a tweeter with the main driver still run fullrange?
I'd like to check out the Pioneers above as well, but google has no mention of them apart from Mr Pass's article. Anyone know someone who sells them etc?
Cheers, thanks for the responses.
I haven't listened to them, yet. Hopefully I'll finish them up on Saturday. In any case, with my hearing, I'm not one you could question on sound quality 🙂.
Tom.
A bit of an update.
I've got four of these to play with. At the moment I have one in a medium sized cardboard box stuffed with socks. Mid-high sounds pretty good, though there is no bass to speak of. Certainly they sound a lot better than they should for the price.
I'll try to do some more formal measurements at some point, as there are no real specs available, time does not permit very much at the moment though.
I've got four of these to play with. At the moment I have one in a medium sized cardboard box stuffed with socks. Mid-high sounds pretty good, though there is no bass to speak of. Certainly they sound a lot better than they should for the price.
I'll try to do some more formal measurements at some point, as there are no real specs available, time does not permit very much at the moment though.
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At the moment the amp is an RH84 (have a search on the tube forum) made with clip leads and terminal blocks. Money is going into the house at the moment so this project is being done for absolute minimum $$$.
When I get more time I'll build it all into a box, probably an unused surplus streetlight housing I have. The speakers will be built with used scrap ply from work.
I think amp and speakers have hit about $50 now, including shipping.
When I get more time I'll build it all into a box, probably an unused surplus streetlight housing I have. The speakers will be built with used scrap ply from work.
I think amp and speakers have hit about $50 now, including shipping.
If vintage drivers are to your taste, why not try Magnavox 8WR's (or 6WR's)?
Some of the 8WR's came in a 16 ohm version, and the sound is not too shabby if you get one in good nick. Watch fleaBay in Oz. Readily available.
I have tried them with a piezo supertweeter with a pleasing result.
Doug
Some of the 8WR's came in a 16 ohm version, and the sound is not too shabby if you get one in good nick. Watch fleaBay in Oz. Readily available.
I have tried them with a piezo supertweeter with a pleasing result.
Doug
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