speaker cables

[kallenin]

(I don't know if speakers count as peripherals, but couldn't find anywhere to put this...)

Okay, so for computer speakers, you have two speakers on one cable that plugs into a jack. For a stereo system, you plug in each of the jacks seperately. Are computer speakers simply bundling both cables (in total 4 wires) together?

The nutshell: How would I go about converting regular stereo speakers into something I can plug into a computer? (would i need to buy a certain kind of connector (like stereo mini) and solder the wires to it? but FOUR connectors?)

-Kallenin

 

[alltaken]

ok 2 normal speakers have 4 cables

2 computer speakers have 3 cables!!!!

yes you can turn two normal speakers into computer speakers.
do the speakers have any RCA plugs on the end of them?? (or is it just two bare wires)

easiest way is to get a 2xfemaleRCA-3.5mmMINIJACK (perhaps they are called 1/8" or just stero plugs, but you know the ones)

then on your speakers you would need to add a male RCA to each (making sure you have the wires around the correct way)

then just plug them in.

p.s. how are these being amplified????
because straight from the computer will be quiet as anything!!

 

[Teq]

Hi Kallenin,
Computer speakers almost always have an amplifier built into one of the speaker boxes. Depending on the speakers this can be anything from 1 to 10 watts rms per channel.

Most sound cards cannot directly drive a speaker... and you may damage your sound card trying.

To hook conventional "stereo" speakers up to your computer you need to take a few things into consideration...

<i>First</i>: Are the speakers magnetically sheilded?
If not you run a high risk of blanking disks, messing up your monitor (if it's CRT Based) and perminently magnetically charging any metal parts of your desk.

<i>Second</i>: How much power do they need to produce a reasonable sound level. For some speakers it can take 15 or 20 watts (rms) of power to reproduce voices at a conversational level... even more for music.

<i>Third</i>: Do you have the facilities to amplify the output of your soundcard? This could require a damned expensive stereo or home-theater amplifier.

Ok... enough for the cautions... Here's a simple way around the problem...

Connect your sound card output to your stereo!

All you need is a stereo headphone extension cord, with a mini-stereo plug and jack, long enough to reach from the computer to the back of the stereo and an adaptor with a mini-stereo plug on one end and two RCA plugs on the other.

Plug the extension cord into the soundcard, the adaptor into the extension cord and the "AUX" input of your stereo.

Turn on the stereo, select AUX in, turn up the volume sliders on your taskbar and play some of your favorite music...

Enjoy!

(You will be amazed how good the average computer sounds through a decent stereo)






<b>(</b>Press ALT-F4 for IQ Test<b>)</b>

 

[kallenin]

That'd be great...if i had a stereo! Hehe---i just have the speakers.

Anyway, these speakers are kind of old...I haven't been able to find anything on them online. Is there any way to tell if they are magnetically shielded (other than turning it on and waving a galvanometer around...)? Also, will a simple power amp circuit do, or is the sound card expecting something a bit more sophisticated? THe speakers are 8 ohm, 10 watts. Perhaps if i knew how much power were coming out of the sound card, I could use a simple power amp...

-Kallenin

 

[Teq]

Hi Kallenin,
To tell if your speakers are magnetically shielded, go near them with a compass. Doesn't matter if they are turned on or not. If the compass leaves magnetic north to point at your speaker... guess what... not shielded.

I have a set of Minimus 7 speakers from radio shack that will turn a compass 3 feet away! Needless to say they ain't gett'n noplace near my monitor or floppies!

As for power amps. The output of soundcards is pretty standard "line level". This is .7vrms or 1volt peak, somewhere in the 30 to 50 ohm impedence range. It will feed the AUX inputs of just about any stereo and can be used directly on the inputs of most power amps (in which case you use the on-screen sliders for your volume controls.)

From what you say, just about any 10w or 20w/channel stereo amplifier should drive them just fine. Hit your local used electronics dealer... just be sure to test before you pay <G>.

If you're of a mind to homebrew an amplifier (fun stuff!!) there are all kinds of kits and plans to be found on the web, try some google searches, you'll be amazed what's out there.



<b>(</b>It ain't better if it don't work.<b>)</b>

 

[kallenin]

Thanks,

One more question: am I looking to MULTIPLY the voltage (by roughhly 10), or just to shift it up 10 watts?

-Kallenin

 

[Teq]

Wattage is a function of voltage and current. (P==E*I)

Power amplifiers do two very important things...

First, they have voltage gain to provide enough signal for higher levels of output.

Second, they must have current gain so they are capable of driving very low impedence (i.e. high current) loads such as those of 4 or 8 ohm speakers.

Simply increasing the voltage does not give you a circuit that can drive such a low impedence. Increasing the current won't give you the needed voltage to develope a lot of power. A power amplifier, thus, includes a voltage amplifier at it's input to drive the current amplifier at it's output... this accomodates both requirements.

10 watts across an 8 ohm load requires you to produce about 9 volts of output ... P==E^2/R == (9*9)/8 == 10.1 watts.

But it also requires you to produce about 1 amp of current... I==E/R == 9/8 == 1.1 amps.

The industry standard for "line level" outputs, used on most soundcards is .7vrms into a 100ohm load (i.e. considerably less than a 1/100th of a watt of actual power) ... The power amp needs to convert that into 9vrms into 8ohms... i.e. about 10watts.



<b>(</b>It ain't better if it don't work.<b>)</b>