And another from SA

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I've been lurking in these forums for a while now and, seeing a fellow South African post an introduction, thought that an introduction would be in order.

So what is mgoedeke all about then? Well, my primary intererst is music and DIY audio is a natural extension of that. I am a poor student (2nd year B.iT at the University of Pretoria) and as such am a devout follower of planet10's frugalphilia (tm). Here in South Africa, the exchange rates and import duties take DIY audio out of reach of someone like me (survival first) so one has to make do with what is produced locally or eastern imports.

High efficiency speakers and horns appeal to me especially (for one it allows one to use IC amps). All my listening is done with my PC as the source (SB Live! DE5.1) and I listen to anything from early music through classical, blues, jazz, rock and even some dance. All this might be herecy to some, but a 32-band graphic EQ (plug-in for winamp) makes even my cruddy (modded) multimedia speakers sound passable. Curerntly a 115l 10" sub tuned to about 28 Hz takes over from these, but soon I will listen to the fruit of my first active system (been saving up for a while)

Current projects (short term):

Quieten down PC (hard drive is nr.1 culprit), thinking of building a MDF enclosure

Multi-amp (PLLXOs to begin with) non-inverting Gainclone setup with 15" PA bass mid. Still deciding on whether to use a mid-tweeter (old unit from Coral BX-7 I got from my grandfather) or horn, even though it might look a bit PA-ish (then again this is a party speaker of sorts).

ESP Project 93 (still looking for a good electret capsule)

6,5" bass-mid and 1" tweeter (bought bulk and have enough for a couple) floorstanders and mini-monitors. ($ 35 for drivers for stereo pair and they look good to boot) T/S wise these are good for 40 Hz F3 in a 15l box an are 87 dB@2.83V/1m.

Various subs (build for friends, mostly car use)

Long term projects (i.e. dreams):

Electrostatic headphones (direct valve driven)
Multi-amped horn system (a kilowatt doomsday device on a smaller scale ;-)

Let the good times roll

From Gareth

Hey its good to see that there are some South Africans out there who are into this kind of stuff. I'm sure you agree it is hard to get parts and components in SA. I thought Cape Town would be jacked up, but not really. Don't you wish we had websites like Parts Express with all those groovy components at such good prices?

My Elliott P3A amps cost me around R500 in total (that's 70W x 2 into 8R and 120W x 2 into 4R). It's a brilliant amp if you want some power and don't wanna spend a fortune. The most expensive part was the toroid at R320 for a 300VA 25-0-25. The Toshiba output transistors are hard to get now too. Where do you buy your components from?

Well, see you round the forums

DIYAudio, the disease spreads to Africa

Yes, sourcing components is a real pain. R500 for the P3A sounds like you did a P2P version of it, or? One can get hold of Seas from TV audio (in Johannesburg, dunno about Cape Town), but you can get Vifa there(dunno where from), but at those prices i'd rather go elsewhere with my money. To ship stuff costs more than than the components themselves and I'd die for a place like PE (even played with the idea of goin into business with audio) for a while. I get my electronics from Communica or Electrocomp.

I am looking at building a P3A and having some of my EE friends lay out a PCB for me, but first I want to get my hands on panasonic electrets somewhere (and R25 for a LM1875 isn't exactly cheap by US standards, but for a 25W amp, I'm not complaining). I'll use gainclones to begin with and use the P3A for my woofers when I am done with my passive pre-amp/active crossover.

Rod now suggests some alternatives and has a link to a site with even more design goodies for the P3A.


My P3A

hey martin

no actually i handmade the PCB's for my P3A's. Here's a Pic of the unfinished version:



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Vintage drivers

Sorry about the slow reply, but university projects are keepig me very busy. I measured them at 80mm (3") and they are Alnico. I have four of these (the original used two per cabinet). I also have the two 10inchers (which are unbelievably solidly cast (5mm aluminium cast basket and large alnico magnet), but one of them was blown at a party (some idiot decided to turn up the cheap jap 2x50W reciever into clipping, and they played really,really loudly for what they were worth (they were crossed over to my 10" sub) and the next morning I noticed the one cone was torn concentrically around the dustcap. The vc went with it (rated for 8W, 16 Ohm nominal). I pushed these through my impedance jig and i think something is wrong (Qtc of 0.96 and Fc of 45 Hz) and this might have to do with them having been lying face down for some time (suspension sag) and when connecting them to my amp with music, one can audibly hear the volume increasing when one presses the cone inwards.

Can one repair such speakers (recone) or would this be an insult to the magnet/basket? The surviving 10" has surprizing extension (might measure it with my new mic soon) and might be a candidate for a low-order crossover. I was actually hoping it would be suitable for an Edgar style bass-horn eventually but I leave that one for another day (or year in all likelyhood). Really time to turn in (c++ is 3v0l)

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