Impedence of Foxpro SP-55
- Thread starter AndrewS
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Evil_Lurker
New member
You can't really measure them with an ohm meter, anyway. It's a coil, and the D.C. resistance will measure lower than the A.C. impedance.
My 8 ohm speaker reads around 2 ohms on the multimeter, for example.
My 8 ohm speaker reads around 2 ohms on the multimeter, for example.
TimberToes
Active member
Originally Posted By: AndrewSThe DC resistance of a coil is all you need. A speaker with an 8ohm nominal impedance will usually have an Re of around 6.3ohms. If your speaker has an Re of 2ohms your nominal impedance is not 8ohms. That wouldn't even make a 3ohm nominal impedance rating.
Actually:
The term Impedance denotes an AC value that varies with frequency.
there is no correlation between the dc resistance and the AC Impedance.
well, ok resistance determines the Q of the inductor, and max wire current/i squared R loss, but thats essentially all.
The "Re" impedance at resonant freq, which in theory pure resistance, you have to measure that with the resonant freq applied to the speaker. And then calculate Re based upon the current and voltage at resonance.
the only reason a Nom impendace at some freq and Re are similar is because the speaker Q is so low, the difference in values are small.
But an ohmeter is gross oversimplificaton,and ...sacriliege!!
(being surronded by the best in test equipment will do that to you)
Impedance of a speaker voice coil is a function of number of turns of wire, size of the coil, and the magnet surronding it.
the resistance will be the size of the wire, and the length of the wire, and nothing else.
hope that help a little. and then just get an 8 or 16 ohm speaker.
Actually:
The term Impedance denotes an AC value that varies with frequency.
there is no correlation between the dc resistance and the AC Impedance.
well, ok resistance determines the Q of the inductor, and max wire current/i squared R loss, but thats essentially all.
The "Re" impedance at resonant freq, which in theory pure resistance, you have to measure that with the resonant freq applied to the speaker. And then calculate Re based upon the current and voltage at resonance.
the only reason a Nom impendace at some freq and Re are similar is because the speaker Q is so low, the difference in values are small.
But an ohmeter is gross oversimplificaton,and ...sacriliege!!
Impedance of a speaker voice coil is a function of number of turns of wire, size of the coil, and the magnet surronding it.
the resistance will be the size of the wire, and the length of the wire, and nothing else.
hope that help a little. and then just get an 8 or 16 ohm speaker.
Last edited:
Evil_Lurker
New member
Exactly, it will relate to wire size and length. I can even find you an 8 ohm speaker that is A.C. coupled through a capacitor, and your ohm meter will see it as an infinite resistance.
I've never seen an 8 ohm speaker ohm out to 6 ohms. That must be some tiny wire they wound it with.
What is it for, an I-pod?
I've never seen an 8 ohm speaker ohm out to 6 ohms. That must be some tiny wire they wound it with.
What is it for, an I-pod?