Came out of the enclosure and old iPod clock radio pictured. It has pretty decent sound for such a small driver, but I didn’t expect this oddity upon removal.
It’s the equivalent of magnetic shielding. The second magnet mostly cancels the magnetic field of the main magnet. This was more important when we used CRTs and the magnetic field would mess with them when you put a speaker close to the CRT.
measure resistance and compare to whats printed on it
Please note the 6 ohm value printed is the impedance, not the resistance. However measuring the resistance can still be useful, if it measures open circuit or extremely low it can indicate an issue. Just don’t expect it to be exactly the same as the impedance.
So how would you measure the impedance. Impedance being the resistance of the inductive load at a certain frequency. The Henry value of the coil isn’t printed there nor is the tuned frequency. 6ohms would be one value you could use to work back wards through the equation.
It’s been a long time since I studied this but this is something that always puzzled me. I ended up buying and a special meter for this stuff. The name of that even escapes me
I haven’t messed around with the math in so long that I do not recall most. Now, I just assume it is a peak power rating. Like, 6 ohms at 5 watts means no more than around 800 mA.
If I’m hacking audio, I don’t typically do much with output stages. I would rather mess with the preamp, filters, and buffer.
This post was more of a curiosity about the second magnet. I’m curious how they applied it, why, the glue, process, and if it is just in serial polarity or if there is more going on in this application.
When I did my electronics training one of my instructors was an audiophile. He weod go down the rabbit hole on speaker coil windings, amps, anything audio. He owned a side business rewinding speakers(?) and making speakers.
The other kids listened intently and I was just wanting to get out of there or back on topic.
Impedance is a function, not a value - that’s why it’s often plotted as an impedance curve. If you’re seeing a single value you’re probably seeing either the nominal impedance or the minimum value.
As for how to measure it, all you need is a resistor, an amplifier, a signal generator (your phone or computer will be perfect), and a multimeter that can measure AC voltage. If your amplifier is pretty flat, you can simply measure the amplifier output voltage once and then measure voltage drop drop across either the resistor or loudspeaker at various frequencies. Some basic math will let you determine the resistance of the loudspeaker at a given frequency. From there you can even start hand calculating the t/s parameters, although calculating Vas is a bit fiddly.
