Replace resistor by low-inductance resistor - Is it audible?

[March Audio]

Pick your poison -
differences between wirewound resistors are huge.

So again, this thread is an example of the typical ASR oversimplification.

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No, this is yet again an example of your incredible ability to miss the point and go on an irrelevant tangent with even less relevant tests and data.

We are talking specifically about resistors in a crossover. The variations will have no significant effect on an amp.

 

[pma]

Repetitive frequency is 800kHz (distance between 2 negative peaks), which is totally unimportant.

V = R*i + L*di/dt

i = 4.5mA
di/dt = 4.5mA/10ns (450 000A/s)

So you can calculate L and consider if it is OK for you. I am speaking about amplifiers, as I have already stated.

Sorry I made a mistake with i value.

i = 20mA
di/dt = 20mA/10ns (2 000 000 A/s)

Yes everything has inductance, but I do not need the resistors or capacitors that I use in amplifiers to have high inductance. And this 0R22/5W #1 has too high inductance, if used in amp feedback.

 

[Francis Vaughan]

And this 0R22/5W #1 has too high inductance, if used in amp feedback.

Then don't use it. It is as simple as that. But it has no bearing on whether the same resistor could be used in a crossover, or indeed in a different amplifier design that was more tolerant of the inductance (perhaps with slower output devices or better margins.) One assumes you have done the calculations and know what the allowable inductance is, and know for certain that whilst the poorer resistor is unsuitable, that the better resistor is within the allowable margins and can be used safely.

 

[solderdude]

Yes, for amps induction of resistors can be an issue.

The topic is about speakers... in this case inductance is a non issue as it is many times smaller than the wiring, and voicecoil inductance.

 

[Selah Audio]

Hi Rick---Are expensive crossover components more reliable?

No. It's very rare for passive components to fail. The only exception is with a pro audio speaker which may need a high power resistor with a heatsink casing. Due the use/abuse in the field heat dissipation and reliability are important.

 

[617]

No. It's very rare for passive components to fail. The only exception is with a pro audio speaker which may need a high power resistor with a heatsink casing. Due the use/abuse in the field heat dissipation and reliability are important.

Is high power dissapation using resistors common with pro audio type speakers? In hifi you see resistors padding down midranges and tweeters, the former being where you sometimes need really high wattage resistors, but I never thought a heatsink would be necessary.

 

[SIY]

Is high power dissapation using resistors common with pro audio type speakers? In hifi you see resistors padding down midranges and tweeters, the former being where you sometimes need really high wattage resistors, but I never thought a heatsink would be necessary.

With some speakers, the crossover parts are designed to fail before the drivers, which is kind of a nice idea. In my own experience, I inherited some NHT M3.3 that had gone dead after being abused with a high power amp. The drivers were fine, but a couple of the electrolytic caps had exploded. Ten minutes and about $2 later, I had a superb pair of speakers. According to a couple of the engineers at NHT, this design choice was quite deliberate.

 

[Bruce Morgen]

Since a shunt appears in the voltage divider just as much as a series, this assertion seems more than a bit odd.

My comment did not refer to resistors, but rather to inductors and capacitors used in the shunt portion of second (and higher) order filters, where they are not in the signal path per se.

 

[SIY]

My comment did not refer to resistors, but rather to inductors and capacitors used in the shunt portion of second (and higher) order filters, where they are not in the signal path per se.

Of course they are. And just as subject to voltage divider equations.

 

[Selah Audio]

Is high power dissapation using resistors common with pro audio type speakers? In hifi you see resistors padding down midranges and tweeters, the former being where you sometimes need really high wattage resistors, but I never thought a heatsink would be necessary.

In the few that I've worked on; however, this is one reason why many now are powered with active crossovers. Some of the resistors didn't use heatsinks but had standoffs to allow for air circulation under the resistor.

 

[Gringoaudio1]

When I was building tube guitar amps, finding voltage ratings for readily available resistors required some sleuthing. I shudder to think how many DIY projects may have under-rated resistors - possibly even commercial ones.

Resistors are not rated by voltage unless for huge voltages. You might have hundreds of volts running in various places in a tube amp but in what application would that entire voltage be dropped across that one resistor? And even if it was it would be well within the dielectric breakdown limits of materials used for making resistors. The rating that exists or matters for resistors we would ever use in audio is their power rating.

 

[DualTriode]

Hello All,

There would be no damping factor if the the driver impedance and series crossover resistors were not in the amplifier feedback loop.

So yes the inductance of crossover resistors does impact the performance of the amplifier. And yes it is measurable. Is it audible and to what degree that is another question?

The price of a Mills non-inductive resistor is not going to break the bank.

Thanks DT

 

[SIY]

There would be no damping factor if the the driver impedance and series crossover resistors were not in the amplifier feedback loop.

So yes the inductance of crossover resistors does impact the performance of the amplifier.

That would have to be one amazingly bad amplifier.

 

[wje]

The price of a Mills non-inductive resistor is not going to break the bank.

Yes, quite true! They're a solid product to use.

 

[DualTriode]

That would have to be one amazingly bad amplifier.

What makes that a bad amplifier?

That is how damping factor works, feedback!

The greater the feedback the greater the damping factor.

Thanks DT

 

[SIY]

What makes that a bad amplifier?

Sensitivity to absolutely minuscule amounts of inductance in the load. I've not yet seen an amp quite that bad, but there's probably one out there with a 5 digit price tag.

 

[DualTriode]

Sensitivity to absolutely minuscule amounts of inductance in the load. I've not yet seen an amp quite that bad, but there's probably one out there with a 5 digit price tag.

Put that resistor on your Bode 100 VNA and tell us minuscule. Show us the impedance and phase plots.

 

[SIY]

Put that resistor on your Bode 100 VNA and tell us minuscule. Show us the impedance and phase plots.

Wonder how amplifiers deal with voice coil inductances? Or speaker wire?

Yes, minuscule. 2/3 of a microhenry. Most tweeters have two orders of magnitude greater inductance. Step up a couple more orders of magnitude for midranges and woofers.

 

[A800]

What makes that a bad amplifier?

That is how damping factor works, feedback!

The greater the feedback the greater the damping factor.

Thanks DT

Lower output device resistance also results in higher DF.

 

[thewas]

Although the significance of DF in audio amps gets usually overestimated
http://diyaudioprojects.com/Technic...ping-Factor-and-Damn-Nonsense-Floyd-Toole.pdf