Wire wound Power Resister reactance to AF

If it's a dummy load to stand in for speakers, why worry about inductive reactance when speakers have it also?

Why are you trying to substitute a purely resistive load when the rated "ohms" of a speaker specifically is inductive reactance.

What brain fart made you think that

And you're a licensed Ham?

I found the DRM information interesting though.

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Good point.

I don't think that. But since the impedance curve for every speaker is different, I don't know what else to do and have seen other similar designs.

Massive Ego, compensating for a tiny weenie?

"Chris W"

You can expect their values to remains constant ( +/- 0.1%) over the audio range and way beyond too.

.... Phil

"Greegor"

If it's a dummy load to stand in for speakers, why worry about inductive reactance when speakers have it also?

With bass drivers the rise begins above 500Hz and with tweeters it begins above 3 to 5 kHz.

Why are you trying to substitute a purely resistive load when the rated "ohms" of a speaker specifically is inductive reactance.

The rated impedance for all bass drivers and most other drivers too is at taken at a frequency where the load impedance IS resistive.

For nearly any bass driver, this frequency is around 250 Hz and the impedance value is 10 to 25% greater than the DC resistance.

What brain fart made you think that

** The OP never made any such silly assumption.

And you're a licensed Ham?

..... Phil

It will have less inductance than a loudspeaker.

"Jasen Betts"

- hobbling along behind the rest of the pack.

Till a truck runs him over .....

Splaattt........

.... Phil

A friend was using some 22ohm versions of those resistors for the same job. An impedance sweep ...

"john jardine"

..... Phil

A 50 watt 8 ohm in this style from my stock measures 130 nH @ 10kHz

A 250 watt 4 ohm unit I have measures 850 nH @ 10kHz

"The Phantom" "Phil Allison"

..... Phil

The meter was zeroed with a heavy copper shorting plate, then:

A 63 mm piece of 16 gauge copper wire, pressed down as close to the fixture (to minimize loop area) as I can get it, measures 21 nH @ 10 kHz.

A 63 mm piece of 30 gauge copper wire, pressed down as close to the fixture as I can get it, measures 37 nH @ 10 kHz.

When I measured the resistor, I could only get the body of the resistor snug up against the fixture, not the actual current path, so there was more loop area than with the wire.

Of course, the OP, using these resistors for his load, would have much more loop area unless he exercised extreme care. The inductance of the resistor isn't going to be the main determinant of the inductance of his setup.

Interesting!. Just measured a (to hand) 20ohm. Shows 5uH. Then measured a Welwyn 0.1ohm and it showed 60nH. Both seem reasonable numbers as I'd assumed all these types of resistor were wirewounds (observed via the flotsam of experimental disasters). From the figures you quote, it looks like the construction varies from maker to maker. In pursuit of geek science and with a milling machine to hand, I opened up the Welwyn 20ohm. A la ...

You'll notice that on the web page the OP linked:

under description, it says "Resistor Element Material: Ceramic". I assume that would account for the low inductance.

"john jardine"

Using this on-line calculator:

L = 4.6uH

A resistor of only 0.1 ohms is likely made with flat strip conductor and far fewer turns than the example in the pic.

....... Phil

"Phil Allison"

.... Phil