New to building, need some advice.

msharpe · 31st January 2006, 01:08 AM

I recently decided that i want to upgrade the speakers on my old stereo, and I wanted to do it for a small price. So I'm trying to figure out how to build an amp. I plan to use a pair of 150 watt 8 ohm woofers, four 8 ohm speakers, and a pair of 60 watt tweeters. Theese are all things I've found surplus, so I don't have all the specs on them. So basically, I've been looking around the net and in some books, and I've found a schematic for a class B amplifier that looks very simple. It's basically an NPN combined with a PNP transistor. I'd imagine it's really inefficient, but will something like this work for me? I planned to build an amp for each set of speakers, so 6 at least, and then wire them all in parallel to a power supply. Does this sound like it would work? I know that I'll need three way crossovers, but can I put two speakers on each midrange section?

Cal Weldon · 31st January 2006, 03:26 PM

I'm not any help with the amp but you can use 2 drivers for the mid section.

Its pretty tough to design an XO if you don't have the parameters of the drivers. Without them it's pretty much hit and miss, with miss being at the forefront.

richie00boy · 31st January 2006, 03:54 PM

Can you post the schematic for the amp? It is just not possible to build a usable audio power amplifier using just an NPN and a PNP.

If you are on a budget I would just say buy a used amp and speakers. Active is the best way not necessarily the cheapest way.

As Cal said without parameters, your speakers are pretty useless, but the good news is that you can measure them yourself.

Moderator - Cal must have been asleep as he left this thread in the Subwoofers section, it would be better in the Loudspeakers section would it not?

Cal Weldon · 31st January 2006, 04:09 PM

Thanks Richie, I have moved it.

msharpe · 31st January 2006, 06:19 PM

Well here are the schematics i've got, they're pretty rudimentary, just copied form a couple places. The bottom right is what is supposed to be a class B amp.

From how things are going, It's looking more and more like I might just buy rather than build an amp

richie00boy · 31st January 2006, 06:42 PM

That link is asking me to join to see the pics.

msharpe · 31st January 2006, 07:35 PM

OK hopefully this lik will work

richie00boy · 31st January 2006, 08:23 PM

Nope just the same

31st January 2006, 01:08 AM	#1
msharpe diyAudio Member Join Date: Jan 2006 Location: Pickerington, OH	New to building, need some advice. I recently decided that i want to upgrade the speakers on my old stereo, and I wanted to do it for a small price. So I'm trying to figure out how to build an amp. I plan to use a pair of 150 watt 8 ohm woofers, four 8 ohm speakers, and a pair of 60 watt tweeters. Theese are all things I've found surplus, so I don't have all the specs on them. So basically, I've been looking around the net and in some books, and I've found a schematic for a class B amplifier that looks very simple. It's basically an NPN combined with a PNP transistor. I'd imagine it's really inefficient, but will something like this work for me? I planned to build an amp for each set of speakers, so 6 at least, and then wire them all in parallel to a power supply. Does this sound like it would work? I know that I'll need three way crossovers, but can I put two speakers on each midrange section?

31st January 2006, 03:26 PM	#2
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	I'm not any help with the amp but you can use 2 drivers for the mid section. Its pretty tough to design an XO if you don't have the parameters of the drivers. Without them it's pretty much hit and miss, with miss being at the forefront. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

31st January 2006, 03:54 PM	#3
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Can you post the schematic for the amp? It is just not possible to build a usable audio power amplifier using just an NPN and a PNP. If you are on a budget I would just say buy a used amp and speakers. Active is the best way not necessarily the cheapest way. As Cal said without parameters, your speakers are pretty useless, but the good news is that you can measure them yourself. Moderator - Cal must have been asleep as he left this thread in the Subwoofers section, it would be better in the Loudspeakers section would it not? __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

31st January 2006, 04:09 PM	#4
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Thanks Richie, I have moved it. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

31st January 2006, 06:42 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	That link is asking me to join to see the pics. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more


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31st January 2006, 06:19 PM	#5
msharpe diyAudio Member Join Date: Jan 2006 Location: Pickerington, OH	Well here are the schematics i've got, they're pretty rudimentary, just copied form a couple places. The bottom right is what is supposed to be a class B amp. From how things are going, It's looking more and more like I might just buy rather than build an amp

31st January 2006, 07:35 PM	#7
msharpe diyAudio Member Join Date: Jan 2006 Location: Pickerington, OH	OK hopefully this lik will work

31st January 2006, 08:23 PM	#8
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Nope just the same __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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