Speaker impedance - explain?

** NO.

** NO.

Do a Google search you lazy piece of shit.

........ Phil

I have....is confusing.

Actually I ask is on this board because when an actual person explains it, it makes alot more sense.

Some of the 'tutorials' and 'faqs' on the net are unneccessarily complex.

"andrew_h"

** First off - learn to use "googlegroups" correctly.

Do NOT simply hit reply !!!!!!!!!!!!!!

Hit "options" and then "reply".

That way we can see who you are replying to and about what.

** Basically, it is the resistance of the coil of copper wire inside. ** Speakers with impedances from 0.5 ohm to 1000 ohms have been made.

The range from 4 to 16 ohms is just *much* easier to make.

In the valve era, 2 ohms was common for radio set speakers and 16 ohms for early hi-fi speakers.

The most common by far now is 8 ohms, since it suits power transistor voltage and current abilities best.

Two 16 ohm speakers in parallel gives 8 ohms.

Two 8 ohm speakers in parallel gives 4 ohms.

It is just that simple.

....... Phil

How about starting with this response ?

Do you know the difference between resistance and impedance ( of anything ) before launching into an elaborate discussion of same.

It isn't. 4, 8, 15/16 are simply commonly accepted norms. 6 ohms isn't uncommon either in some kit. Don't forget that the impedance is simply 'nominal'.

Graham

I know. Some ppl like to 'show off' and 'miss the point'.

Graham

Thanks for all your replies.

I did search alot on google before - but yeh, alot of people like to read their own words, and so the descriptions arent as simple as they can be.

First of all, instead of "impedance" think "AC resistance". It's the value you would use when you are trying to compute the power the speaker will draw from the amp, via V^2/Z where V is the RMS output voltage and Z is the impedance.

(Note that the power drawn by the speaker is not the same as the sound power delivered, since speakers have a wide range of efficiencies... but 1% is typical.)

In a speaker, impedance is made up of the DC resistance of the copper wire in the voice coil, plus the AC "reactance" of the inductive effects from that same wire being in the form of a coil (with an iron core), plus the mechanical reactance due to the spring in the suspension and the mass of the moving cone. The reactance part varies with frequency, and actual speaker impedance typically has a big peak around resonance, or two peaks one on either side for tuned designs (like those with ports or passive drivers).

So, the numbers like "4 ohms", "8 ohms", etc are really just nominal values. Their main real use is in comparing suitability of drivers for use with a particular amp. Higher impedances demand less current from the amp to get a certain power, so amps are typically rated as to the lowest nominal impedance they are happy to drive. Lower impedance may draw too much current, but you can always use a higher impedance speaker... at least with modern solid state amps. Tube-type amps with output transformers typically have different taps for driving different speaker impedances, and there you should select the matching value.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

its the same as it would be if you were to calculate DC resistance except with the term impedance, it normally indicates that an AC signal is involved and under these conditions some devices behave differently giving you a different results of resistance over what would be Dc ohms. for example, a speaker coil can be inductive and thus at high frequencies the impedance of the circuit may increase. that is one reason among others that it is good to have a multiple set of speakers attached to the output that covers all ranges of audio. but in most practical mid range type speakers you will find the impedance matching very close to what a DC ohm reading is.

--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

P.S. one more thing. the lower ohm type speakers are normally used in low voltage systems where it saves on cost of an amplifier to drive the voltage up that will thus deliver enough power to satisfy your needs for volume. in the case of automobiles for example, 12 volt systems can only generate a limited amount of Db's from a speaker using lets say a 8 ohm system how ever, if you were to use a 4 ohm system you can then get double the output as long as the components can handle the current. 2 ohms systems even get more current in the speaker coil from a

12 volt amp.. then you have those amps that have power inverters in them so that the internal power voltage level is actually higher than the supply line. these normally draw more current depending on how much higher the increase of voltage is. these low ohm speakers are great and solves issues of getting more dbs from a speaker with lower voltage equipment how ever, it also adds to the cost of larger gauge wire for long runs. this is why higher ohm speakers are popular in some areas. long runs of small gauge wire with higher voltage amplifiers reduces the needs for larger gauge wire.

--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Well explained Bob couldn't have done better myself.....that ought to end this thread! ....Ross

Horrible manners. This IS sci.electronics.basics. People might actually discuss and help instead of being rude.

Ignore Phil. He suffers from a form of autism known as Asperger's Syndrome which means he's incapable of communicating effectively with the outside world. Your question's a very good one. If I hadn't drunk a bottle of Australian wine this afternoon, I'd happily answer it. Hopefully, however, someone else will. :-)

"Paul Burridge"

** Ignore Paul Buggerage.

The vile pommy cretin suffers from a form of autism known as Asperger's Syndrome which means he's incapable of communicating effectively with the outside world.

........ Phil