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Old 6th December 2007, 05:38 PM   #1
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Default Resistor Inductance

Hi Folks!

Are non-inductive resistors worth it?. What would be the difference between buying a 1 Ω wire wound resistor at my local Radio Shack to put in series with my tweeter, as appose to buying the "audio grade" type? How much inductance are we talking about? Also, is there any sonic differences between attenuating resistors in series and using them in a L-Pad configuration?

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John.
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Old 6th December 2007, 05:49 PM   #2
DcibeL is offline DcibeL  Canada
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You want to discuss whether the difference between something that costs pocket change, and something that costs a little more pocket change is worth it?

From Solen here in Canada a cement wirewound 10W resistor costs 23 cents and a metal oxide 10W resistor costs 53 cents. Radioshack in the states wants $2 for a 10W cement resistor (according to their website) and the values are very limited. The difference in price is pocket change, especially when compared to the cost of an entire speaker project, so why not?

I think the point I'm trying to make here is that you'll save much more money by simply not shopping at Radioshack then you will from using a slightly better metal oxide resistor.

And yes there will be a significant difference between simply adding a resistor in series and using an L-pad. Take a look at an impedance response plot and think very hard about what will happen in either circumstance. The L-pad will apply a uniform attenuation over frequency, but the series resistor will not because the impedance of your speaker will change over frequency. Sometimes this can be benificial.
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Old 6th December 2007, 06:26 PM   #3
MJK is offline MJK  United States
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I measured a number of the inexpensive sand cast resistors from Parts Express and some more expensive Mills resistors, using my LAUD set up, and none of them showed any inductive behavior. I think the audible differences that some people claim to hear between these two types of resistors has more to do with slight differences in actual resistance values and not so much to do with some inductive behavior.

The comments above about the relative cost differences are exactly correct. I usually buy the Mills resistors and spend a little more assuming the construction is of higher quality. The cost difference is not significant compared to the other components in the speaker design. But if I was truely looking to pinch some cost out I would not hesitate to buy the sand cast resistors.
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Old 6th December 2007, 07:14 PM   #4
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It's really not the cost that I care about. Just wondering if there's an actual difference (roll off) in sound, especially regarding tweeters.
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Old 6th December 2007, 08:03 PM   #5
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I wouldn't worry about the inductance that much for the tweeter resistor. Comparing to the inductance of the voice coil of the tweeter the inductance in the resistor is so small and you can completely ignore it. It will only affect very high frequencies way beyond human hearing capability. If you are talking about the resistor in some other circuitary that will be a different story. No worries for the tweeter resistor.
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Old 21st December 2007, 04:50 AM   #6
bastek is offline bastek  United States
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With my inductance meter, a white sand cast resistor of 20 ohms, measures 0.4 mH, which is almost the inductance of the tweeter (0.35mH). A mills 20 ohm resistor measures 0.4 mh also, so there is no benefit in using it.
Now, what happens if you put this resistor in parallel to the tweeter?
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Old 21st December 2007, 05:17 AM   #7
soongsc is offline soongsc  Taiwan
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Recently I compared the white resistors with Duelund resistors, and the Duelund ones sounded much cleaner. The white ones sounded a bit harsh.
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Old 21st December 2007, 05:21 AM   #8
gootee is offline gootee  United States
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Quote:
Originally posted by bastek
With my inductance meter, a white sand cast resistor of 20 ohms, measures 0.4 mH, which is almost the inductance of the tweeter (0.35mH). A mills 20 ohm resistor measures 0.4 mh also, so there is no benefit in using it.
Now, what happens if you put this resistor in parallel to the tweeter?
I'm surprised that they measured so high. Were they very large resistors?

Did you measure the inductance of the shorted probes, too, as a baseline?
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Old 21st December 2007, 05:31 AM   #9
bastek is offline bastek  United States
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They are both 10W resistors. The probe's inductance is minimal. (0.003mh). I was surprised too.
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Old 21st December 2007, 05:43 AM   #10
tubino is offline tubino  United States
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Quote:
Originally posted by bastek
With my inductance meter, a white sand cast resistor of 20 ohms, measures 0.4 mH, which is almost the inductance of the tweeter (0.35mH). A mills 20 ohm resistor measures 0.4 mh also, so there is no benefit in using it.
That is surprising. What frequency were you using? Probably around 1K, no?
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