Main > Audio/Jukebox/MP3 Forum
Using car speakers in a cab
JoeB:
Folks, all of you seem to forget one important thing..
PSU from PC are 12V.. PS in car when car is running is really closer to 14V!!! It's only when the car is off, is it even near to 12V!!
If you guys want to do it right, your best bet is to go to a local pawn shop or thrifty store (or flea market) and get a 12V Power supply!
I found mine at a local pawn shop, and paid 30$CDN for it (which is less than 20$US) and I got a PSU that supplies 13.8V constant 10AMPS (or 12AMP peak). That translates to about 138W RMS!!! (Which is probably close to 300W peak). And all this for less than the cost of any decent PC PSU! (not to mention that any decent 12V PSU will come with build in thermal protection, build in voltage cutoff/spike protection, etc.. goodies that a regular PC PSU will not have!)
LK
Tehrasha:
--- Quote from: JoeB on February 18, 2003, 04:04:11 pm ---Folks, all of you seem to forget one important thing..
--- End quote ---
Nothing been forgotten. Math for current and wattage remains the same.
--- Quote ---If you guys want to do it right, your best bet is to go to a local pawn shop or thrifty store (or flea market) and get a 12V Power supply!
--- End quote ---
Your risk of 50/60 Hz hum increases greatly when using generic 'power supplies' as car amplifiers have no built-in filtering for powerline freqs.
--- Quote ---I found mine at a local pawn shop, and paid 30$CDN for it (which is less than 20$US) and I got a PSU that supplies 13.8V constant 10AMPS (or 12AMP peak). That translates to about 138W RMS!!! (Which is probably close to 300W peak). And all this for less than the cost of any decent PC PSU! (not to mention that any decent 12V PSU will come with build in thermal protection, build in voltage cutoff/spike protection, etc.. goodies that a regular PC PSU will not have!)
--- End quote ---
13.8V at 10A is 138 Watts..period. RMS has nothing to do with DC voltage/current/power measurements.
Peak of 15A would bump you up to 207 Watts. Figure in a generous 60% efficency for the amplifier and divide for 2 channels of audio.
Maximum peak output 62 Watts/channel. 41 Watts/channel nominal.
As for voltage regulation and shutdown safety, yes computer PS have these as well, in fact the voltage regulation is most likely far superior to generic 12v power supplies.
They have to be. Your computer is alot pickier about its voltage levels than an audio amplifier is. A car amplifier will chug right along even if the supply voltage dips to 6 Volts (albeit quieter and less efficient). Try that with your computer sometime and see what it does. :)
Silverwind:
--- Quote from: JoeB on February 18, 2003, 04:04:11 pm ---Folks, all of you seem to forget one important thing..
PSU from PC are 12V.. PS in car when car is running is really closer to 14V!!! It's only when the car is off, is it even near to 12V!!
If you guys want to do it right, your best bet is to go to a local pawn shop or thrifty store (or flea market) and get a 12V Power supply!
I found mine at a local pawn shop, and paid 30$CDN for it (which is less than 20$US) and I got a PSU that supplies 13.8V constant 10AMPS (or 12AMP peak). That translates to about 138W RMS!!! (Which is probably close to 300W peak). And all this for less than the cost of any decent PC PSU! (not to mention that any decent 12V PSU will come with build in thermal protection, build in voltage cutoff/spike protection, etc.. goodies that a regular PC PSU will not have!)
LK
--- End quote ---
not forgetting at all :)
If you run your car stereo with the engine off it's approximatly 12.9 volts..
with it on.. it's usually between 13.8 and 14.4 volts...
but you try to use what you have available.. if you have a free computer PSU handy.. you would use that.. not as much voltage as you would like maybe.. but hey it's the free method..
I also agree that PC power supplies typically have higher standards applied to them.. it's a must when dealing with sensitive electronics..
AlanS17:
I've had plenty of problems with unshielded speaker magnets. I personally think a good set of computer speakers is ideal. Nobody is gonna see them anyways. They'll never know.
Carsten Carlos:
--- Quote ---Your risk of 50/60 Hz hum increases greatly when using generic 'power supplies' as car amplifiers have no built-in filtering for powerline freqs.
--- End quote ---
A big condensator between + and - of the powersupply should help.
Anyway, I'll know more the next days, when I connect my speakers!
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