[HELP][HELP][HELP][HELP][HELP] On an electronics issue

[Drizzt]

Hi all...
I need some help on understanding how the audio electronic works.
I mean, I have minimal knowledge on how to work with transistors and so on, but I lack the basic of audio interfacing: for example, I still have to find someone to explain me the 4ohm-8ohm issue...
For example, I have to take a signal with a mic and transfer it to a headphone, but have no idea of how it should work; I mean, I know how manipulate the signal, but whta input give me a mic? And what output wants an headphone?

HELP!!!!

[Six Of One]

If i get your question right: Microphones usually work in the millivolts range and are usually considered low impedance, which translates into the 35 to 600 Ohms region. The exact impedance varies from product to product and you should be able to find it in your manual.

For far more details see here:
http://members.aol.com/wickstrom1/well_con.htm

Headphones usually have an impedance around 40 and operate in the 150 millivolts region. Therefore Headphones and Microphones are more or less in the same league. Still you need some kind of signal amplifier between them to refresh the signal and increase volume. For more about headphones visit this link:

http://headwize.com/educational.htm

It is currently down but should be back anytime soon.

And about the 4 Ohms - 8 Ohms This is pretty much analog to power circuits. The amplifier is the power source, the speakers are the power consumers. A speaker is rated at x Watts Sinus (which is the technically term for it, don't confuse with Watts Sound, which is a fraud. Well, not really but... ) output at y Ohms. Watts is the energy the speaker can deliver, Ohm is the resistance of the device. Less resistance -> more Watts. But less resistance -> greater chance of blowing the whole thing into smithereens. Then there is also the part of a backflow into the amplifier (peaks) but i won't go into that. Roughly, each doubling of the Ohms at the speaker halves the Watts of the speaker. Each halving of the Ohms doubles the Watts. Amplifiers deliver Watts at a certain Ohm rate, if the Ohms of the amplifer is higher than the Ohms of the speaker calculate with MORE power, if the amplifer's Ohm is lower calculate with less power.

For ex. an amplifier delivers 30 Watts at 4 Ohm. The speaker accepts 30 Watts at 4 Ohm. A match made in heaven. The speaker accepts 30 Watts at 8 Ohm. It gets roughly enough out of this connection to deliver 15 Watts. The speaker accepts 30 Watts at 2 Ohms. It recieves enogh power to deliver 60 Watts. Both is dangerours in some sense. Either your amplifier can be damaged by overstretching, trying to deliver what the speaker asks for, or the speaker is redlined and blows.

Ohms change with the configuration of your speakers. Connecting speakers parallel (2 speakers on 1 amplifier output) doubles the the Ohms of the speakers for each speaker connected. This means connecting 2 speakers of 4 Ohms at one amplifier output increases the Ohms to 8. At any rate avoid connecting differently signed speakers parallel.
Connecting speakers in line (from one speaker to another one) halves the Ohms with every speaker in the line. Connecting 2 four Ohm speakers to one output reduces them to 2 Ohm each. The dangers are obvious.

So, that was a pretty long post and it is rather hard to explain stuff like this in a foreign language, so, if anything is not clear, please post.

Regards

[rugger]

Details are wrong :-)

If you connect multiple speakers in series, the total resistance is the sum of all of the resistances of the individual speakers.

eg two 8 ohm speakers in series

total = 8 + 8
total = 16 ohms

If you connect multiple speakers in parrellel, the inverse of the total resistance is the sum of the inverses of the resistances of the individual speakers see example.

eg: two 4 speakers in parrellel

1/total = 1/r1 + 1/r2 + ....
1/total = (1/4) + (1/4)
1/total = 1/2
total = 2 ohms

Hope this explains it.

[Six Of One]

Thanks for the correction. I guess i confused something there