Hi
I purchased a couple of good used 2446 J drivers. These are rated at 16 ohms. I threw my meter on them and I am reading 7.3 ohms on each one. Based on the spec sheet, I think it should actually be around 12 ohms.
The question is what is going on. Previous owner put in 8 ohm diaphragms or are they shot 16 ohm ones ?
Thoughts ?
I purchased a couple of good used 2446 J drivers. These are rated at 16 ohms. I threw my meter on them and I am reading 7.3 ohms on each one. Based on the spec sheet, I think it should actually be around 12 ohms.
The question is what is going on. Previous owner put in 8 ohm diaphragms or are they shot 16 ohm ones ?
Thoughts ?
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According to the spec sheet, they are likely to be a 16 ohm coil.
DC Resistance: 4.3 ohms (H), 8.5 ohms (J) ± 10% @ 25°C
DC Resistance: 4.3 ohms (H), 8.5 ohms (J) ± 10% @ 25°C
Very few inexpensive meters will read low ohms accurately. I had to pay $400. for a good Fluke
with low ohms back in the 70s.
with low ohms back in the 70s.
That's probably very true as this meter I have is $30 special.
However, I think I am mixing up impedance with resistance. Measuring in ohms across + and - is DC resistance right ? How do you measure the impedance then ?
However, I think I am mixing up impedance with resistance. Measuring in ohms across + and - is DC resistance right ? How do you measure the impedance then ?
DC resistance treats the coil like a wirewound resistor. The AC impedance can be measured
by several methods. Without much test equipment, you can run a sine generator set for 1VAC
output through a 1k resistor into the voice coil. This forms a 1mA AC current source driving the coil.
Then with the 1mA input, the coil impedance at a given frequency is Vcoil / 1mA. For example,
if the AC voltage across the coil is 10mV, then its impedance at that frequency is 10mV / 1mA = 10R.
by several methods. Without much test equipment, you can run a sine generator set for 1VAC
output through a 1k resistor into the voice coil. This forms a 1mA AC current source driving the coil.
Then with the 1mA input, the coil impedance at a given frequency is Vcoil / 1mA. For example,
if the AC voltage across the coil is 10mV, then its impedance at that frequency is 10mV / 1mA = 10R.
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2446J diaphragms may have been replaced with 2446H, datasheet here:
2446H/J | JBL Professional Loudspeakers
"DC Resistance: 4.3 ohms (H), 8.5 ohms (J)"
2446H/J | JBL Professional Loudspeakers
"DC Resistance: 4.3 ohms (H), 8.5 ohms (J)"
I've observed this with my pair of 2426J's also. Both measure about 7 ohms DC resistance, even in a four leads Kelvin measurement.
Best regards!
Best regards!
Kay Pirinha
and are you using yours with a crossover that calls for 16 ohm drivers ? My crossover does and I was wondering if I needed to change anything ?
and are you using yours with a crossover that calls for 16 ohm drivers ? My crossover does and I was wondering if I needed to change anything ?
As I said in your other thread regarding your 2446J's, use your Paragon networks that already call for a 16 ohms midrange driver.
My 2426J's are out of service at the moment, but I'm tinkering with using them in my 4430 builds after adapting the resistive dividers in the N-3134 xover networks.
Best regards!
My 2426J's are out of service at the moment, but I'm tinkering with using them in my 4430 builds after adapting the resistive dividers in the N-3134 xover networks.
Best regards!