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

[JimmyBuckets]

https://www.stereophile.com/reference/1095cable

A little bit of interesting reading.

 

[Killingbeans]

A little bit of interesting reading.

I think it's been mentioned on ASR before, but I couldn't find the thread(s). It's an old article.

At one point in the conclusion he says "finely etched with a little speculation". That seems like quite an understatement to me.
I'd like to see some practical examples and some strong correlation before I would even dream of considering audio cables as something that doesn't fall under the lumped-parameter model. This stuff is not really my strong suit, but I think the EEs on this site would agree with me, when I say that this paradigm shift is very unlikely to happen. It hasn't since the article was written, and it probably never will. With good reason.

 

[BDWoody]

https://www.stereophile.com/reference/1095cable

A little bit of interesting reading.

From the article:

For "free space," the relative permeability and permittivity, µr and εr, are both equal to 1; v is equal to c, the velocity of light. This is the "fast wave" and justifies the common comment that, for audio interconnects, the velocity of propagation within the dielectric is so high that signals respond virtually instantaneously across the length of the cable. However, we must be more cautious when discussing EMC-related problems and digital interconnects communicating high-speed data where this velocity becomes a significant factor.

Am I misunderstanding?

The point of this is for digital cables?

 

[andreasmaaan]

https://www.stereophile.com/reference/1095cable

A little bit of interesting reading.

It's been discussed many times on ASR. Here are a few search results.

I love that the sole (alleged) measurement in that entire paper has been liberated from any actual values:

 

[JimmyBuckets]

If it makes anyone feel better I'm currently using really cheap cables. I just got back into a little bit of hifi after years of just being too annoyed to come back to it. I don't think the article was claiming to have proved the issue one way or another. I am not an engineer but have been building kits and speakers since I was a boy 30+ years ago. I'm sorry but when you get to a very high level resolving system, small changes can make a difference. Is it worth it? That's up to you. I decided 10 years ago to sell all my gear and go back to enjoying the music. I can't lie...I do love the equipment too. I have never spent a ton of cash on interconnects or believed I couldn't put a really nice set together that will perform as well as a boutique brand, as everyone has pointed out...it's not magic. I'm glad everyone is so passionate about the hobby.

 

[egellings]

I think that the voice coil of the speaker (looks like a tweeter) has inductance that likely swamps out the inductance of the resistors, so they should make only a small amount of difference there. If a large ohms value resistor used in a vacuum tube plate circuit were subjected to a similar test, the results would be different. I think the amount of effect is application specific.

 

[Shazb0t]

If it makes anyone feel better I'm currently using really cheap cables. I just got back into a little bit of hifi after years of just being too annoyed to come back to it. I don't think the article was claiming to have proved the issue one way or another. I am not an engineer but have been building kits and speakers since I was a boy 30+ years ago. I'm sorry but when you get to a very high level resolving system, small changes can make a difference. Is it worth it? That's up to you. I decided 10 years ago to sell all my gear and go back to enjoying the music. I can't lie...I do love the equipment too. I have never spent a ton of cash on interconnects or believed I couldn't put a really nice set together that will perform as well as a boutique brand, as everyone has pointed out...it's not magic. I'm glad everyone is so passionate about the hobby.

If you want to actually test out your normal, well designed, interconnect vs another fancy silver one just ensure proper listening controls this time. I think you'll be surprised by the outcome.

 

[JSHamlet234]

We're starting to see a lot of fancy crossover components in speakers that cost peanuts, and which also sound like they cost peanuts. My guess is that these manufacturers know that the YouTube reviewers and bloggers are going to take them apart and fawn over the caps, coils, and/or resistors. The tweeter might only handle 2 watts, the woofer resonates like crazy, sensitivity is barely in the 80s, the port chuffs, but ZOMG LOOK AT THE POLY CAPS!

 

[MrPeabody]

The experiment was done with the resistor in series with the tweeter, and the results were entirely predictable. In trying to think of a different scenario where the results may have been different, the scenario that occurred to me is when using a Zobel to offset the impedance rise in the voice coil of a woofer. The rising impedance of the coil at higher frequency confounds the ability of the low-pass filter to attenuate the woofer. Sometimes a Zobel is used to nullify this effect, consisting of a capacitor and resistor in series, placed across the woofer terminals. At higher frequency the impedance of the Zobel is the just the resistance, which, being in parallel with the voice coil, suppresses the rise in the coil impedance. In this scenario the question is whether the inductance of the resistor would diminish this effect, given that the impedance of the resistor will rise slightly with increasing frequency. I'm too lazy at the moment to do any math, but one thing that occurs to me is that if the resistor's inductance would prove significant in this scenario, all that would be needed to overcome this small effect would be to adjust the capacitor value.

This is probably going to come across as preachy, but the right way to demonstrate this sort of thing is through mathematical analysis. It is impossible to generalize any finding obtained though any simple experiment performed with a couple of specific resistors used in one particular kind of circuit. Not to suggest that this approach doesn't have any value, because it does have some limited value.

 

[pozz]

The experiment was done with the resistor in series with the tweeter, and the results were entirely predictable. In trying to think of a different scenario where the results may have been different, the scenario that occurred to me is when using a Zobel to offset the impedance rise in the voice coil of a woofer. The rising impedance of the coil at higher frequency confounds the ability of the low-pass filter to attenuate the woofer. Sometimes a Zobel is used to nullify this effect, consisting of a capacitor and resistor in series, placed across the woofer terminals. At higher frequency the impedance of the Zobel is the just the resistance, which, being in parallel with the voice coil, suppresses the rise in the coil impedance. In this scenario the question is whether the inductance of the resistor would diminish this effect, given that the impedance of the resistor will rise slightly with increasing frequency. I'm too lazy at the moment to do any math, but one thing that occurs to me is that if the resistor's inductance would prove significant in this scenario, all that would be needed to overcome this small effect would be to adjust the capacitor value.

This is probably going to come across as preachy, but the right way to demonstrate this sort of thing is through mathematical analysis. It is impossible to generalize any finding obtained though any simple experiment performed with a couple of specific resistors used in one particular kind of circuit. Not to suggest that this approach doesn't have any value, because it does have some limited value.

IMO the main value of this thread is not the mathematical proof. There are always scenarios where these values matter, particularly for precise application.

The main value is a clear demonstration for the laymen. Some manufacturers swear that, you know, the best resistor will change the listening experience. And people buy based on that, or pay for needless component-level "upgrades".

 

[JSHamlet234]

IMO the main value of this thread is not the mathematical proof. There are always scenarios where these values matter, particularly for precise application.

The main value is a clear demonstration for the laymen. Some manufacturers swear that, you know, the best resistor will change the listening experience. And people buy based on that, or pay for needless component-level "upgrades".

The flip side of course, is the magic of the placebo effect. If a doctor prescribes an antibiotic for condition that won't actually improve from that antibiotic, but patient believes s/he is now taking the cure and should be getting better, that person is more likely to pull themselves up by their bootstraps and literally feel better. Another example would be the person who replaces the factory air cleaner assembly on their car with an aftermarket performance intake. These sometimes increase power by maybe 1-2%, sometimes not at all, and sometimes they are eventually proven to reduce hp by a smidge. However, ask anyone who installs one how they feel about it! "My top end improved and throttle response is amazing now! I love it!" Well, if they feel better about things, maybe it DID work... in a sense...

Likewise, if I were to recap my speakers with audiophile stuff, and I really believed that it was going to have a real and beneficial effect, and then I'm enjoying my music more because I've convinced myself that it sounds better, maybe I did find the happiness I was looking for.

 

[pozz]

Likewise, if I were to recap my speakers with audiophile stuff, and I really believed that it was going to have a real and beneficial effect, and then I'm enjoying my music more because I've convinced myself that it sounds better, maybe I did find the happiness I was looking for.

It only last so long and then you pay for another placebo masquerading as something else. Informed decisions are like diamonds in that sense: they keep their value.

 

[MrPeabody]

The flip side of course, is the magic of the placebo effect. If a doctor prescribes an antibiotic for condition that won't actually improve from that antibiotic, but patient believes s/he is now taking the cure and should be getting better, that person is more likely to pull themselves up by their bootstraps and literally feel better. Another example would be the person who replaces the factory air cleaner assembly on their car with an aftermarket performance intake. These sometimes increase power by maybe 1-2%, sometimes not at all, and sometimes they are eventually proven to reduce hp by a smidge. However, ask anyone who installs one how they feel about it! "My top end improved and throttle response is amazing now! I love it!" Well, if they feel better about things, maybe it DID work... in a sense...

Likewise, if I were to recap my speakers with audiophile stuff, and I really believed that it was going to have a real and beneficial effect, and then I'm enjoying my music more because I've convinced myself that it sounds better, maybe I did find the happiness I was looking for.

On one or two occasions long ago, I pointed out on some car forum that the claims made by the popular manufacturer of aftermarket high-performance air filters are misleading and even false. They show only that their air filters have superior air flow. They do not provide any data to back up the implied claim that the typical resistance to air flow, for typical pleated paper filters, will inhibit air flow to any significant degree. Most people who buy that product lack the smarts to realize that this is an implied claim, i.e., they don't understand that unless the original paper filter is inhibiting air flow to an extent that affects performance, the high-flow filter can't possibly make an difference.

 

[JSHamlet234]

On one or two occasions long ago, I pointed out on some car forum that the claims made by the popular manufacturer of aftermarket high-performance air filters are misleading and even false. They show only that their air filters have superior air flow. They do not provide any data to back up the implied claim that the typical resistance to air flow, for typical pleated paper filters, will inhibit air flow to any significant degree. Most people who buy that product lack the smarts to realize that this is an implied claim, i.e., they don't understand that unless the original paper filter is inhibiting air flow to an extent that affects performance, the high-flow filter can't possibly make an difference.

Yep. it really comes to down to pressure drop. One ATM is 407 inches of water. A clean paper filter usually results in 1-2 inches of water pressure drop, and that doesn't change until there is a significant dust loading. (at least 5000-10000 miles worth). If the popular aftermarket brands have 10-20% less pressure drop than 1 or 2 inches, out of 407, how much can someone possibly gain? Than you have intakes that draw hot engine air - if the engine was pulling air at 300K before the "upgrade" and now it's pulling in air that's 320K, that's a reduction in air density of 6.25%! Even if the air box housing was causing a pressure drop of perhaps 10 inches H2O, you'll never make up for the difference caused by the increased IAT. As the saying goes, "A fool and his money are soon parted."

 

[MrPeabody]

Yep. it really comes to down to pressure drop. One ATM is 407 inches of water. A clean paper filter usually results in 1-2 inches of water pressure drop, and that doesn't change until there is a significant dust loading. (at least 5000-10000 miles worth). If the popular aftermarket brands have 10-20% less pressure drop than 1 or 2 inches, out of 407, how much can someone possibly gain? Than you have intakes that draw hot engine air - if the engine was pulling air at 300K before the "upgrade" and now it's pulling in air that's 320K, that's a reduction in air density of 6.25%! Even if the air box housing was causing a pressure drop of perhaps 10 inches H2O, you'll never make up for the difference caused by the increased IAT. As the saying goes, "A fool and his money are soon parted."

It is really question of great the flow restriction of the paper filter is, relative to the total flow restriction from intake to exhaust. A simple electrical analogy is a bunch of resistors in series, with varying resistances, and you focus on one of them because it is the only one that you can see and can change. But if this one happens to be one of the weaker ones, and you replace it with another that is just slightly weaker, what impact would this have on the total series resistance? Before it would make sense to consider replacing that one resistor, you would first need to confirm that it makes up a significant portion of the total series resistance, in relative terms. Then you would need to consider how the total series resistance will be lowered if you replace that one resistor with the other one that is slightly lower. The difference in the resistance value, the existing one vs. the one that you're considering replacing it with, is not complete information by which you'd be able to calculate or even guesstimate the resulting decrease in total series resistance, were you to do the swap.

 

[JSHamlet234]

It is really question of great the flow restriction of the paper filter is, relative to the total flow restriction from intake to exhaust. A simple electrical analogy is a bunch of resistors in series, with varying resistances, and you focus on one of them because it is the only one that you can see and can change. But if this one happens to be one of the weaker ones, and you replace it with another that is just slightly weaker, what impact would this have on the total series resistance? Before it would make sense to consider replacing that one resistor, you would first need to confirm that it makes up a significant portion of the total series resistance, in relative terms. Then you would need to consider how the total series resistance will be lowered if you replace that one resistor with the other one that is slightly lower. The difference in the resistance value, the existing one vs. the one that you're considering replacing it with, is not complete information by which you'd be able to calculate or even guesstimate the resulting decrease in total series resistance, were you to do the swap.

Right - The volume of the air passing through the filter is determined by the displacement, RPM, and volumetric efficiency at that said RPM. For example, a 3L engine that achieves peak horsepower at 5750RPM and has 90% volumetric efficiency at that speed, will pull 300CFM through the filter no matter what at peak power. The mass of the air flow, which determines actual power assuming optimal fuel and ignition, is then affected by the density of that intake air. The density is determined by the temperature and the pressure, which is atmospheric pressure minus the slight vacuum imparted by the air filter, air filter housing, and the plumbing to the throttle body. That vacuum on a typical production car (at peak output) is usually around 10-15 inches of water, or about 0.3-0.5% of the pressure that would otherwise be available if the throttle body had nothing clamped to it at all. The air filter itself is usually only around 1 or 2 inches of water when clean, which is only about 0.03-0.07% of the total air charge pressure and thus air mass, and therefore output potential. Infinitesimally small. As such, even having no filter at all would not appreciably increase output.

And the difference caused by low-inductance resistor instead of a sand cast in a speaker crossover is even smaller! The placebo effect is strong, and a sucker is born every day.

 

[MrPeabody]

Right - The volume of the air passing through the filter is determined by the displacement, RPM, and volumetric efficiency at that said RPM. For example, a 3L engine that achieves peak horsepower at 5750RPM and has 90% volumetric efficiency at that speed, will pull 300CFM through the filter no matter what at peak power. The mass of the air flow, which determines actual power assuming optimal fuel and ignition, is then affected by the density of that intake air. The density is determined by the temperature and the pressure, which is atmospheric pressure minus the slight vacuum imparted by the air filter, air filter housing, and the plumbing to the throttle body. That vacuum on a typical production car (at peak output) is usually around 10-15 inches of water, or about 0.3-0.5% of the pressure that would otherwise be available if the throttle body had nothing clamped to it at all. The air filter itself is usually only around 1 or 2 inches of water when clean, which is only about 0.03-0.07% of the total air charge pressure and thus air mass, and therefore output potential. Infinitesimally small. As such, even having no filter at all would not appreciably increase output.

And the difference caused by low-inductance resistor instead of a sand cast in a speaker crossover is even smaller! The placebo effect is strong, and a sucker is born every day.

That is well written. Rarely have I encountered something as well-written as that on a car forum. It explains convincingly why the standard paper filter doesn't affect engine performance to any significant degree whatsoever, for intents and purposes the same as no filter.

 

[JSHamlet234]

That is well written. Rarely have I encountered something as well-written as that on a car forum. It explains convincingly why the standard paper filter doesn't affect engine performance to any significant degree whatsoever, for intents and purposes the same as no filter.

Unfortunately, there is a lot of knuckle-dragging on most car forums. People quote advertised "CFM" numbers without understanding what the spec really means. "This intercooler / muffler / air filter / cylinder head was flow bench tested to 1000CFM!" Yet, they have no idea how much pressure drop is occurring at that CFM; they have no idea how much air is actually flowing through any component of their engine, nor do they have any understanding of the relationship between that pressure drop in that location and how it will affect (or not affect) the engine in question. It's usually just a huge cluster of people spending boatloads of money on parts that are sold by forum sponsors. These sponsors are allowed by the admins to become the de facto forum experts, and anyone who engages in actual reality checking is shouted down by the sponsors, their lackeys, and the end users themselves who need to constantly rationalize their growing credit card bills.

That's why I enjoy this forum. Here, we do our best to delve into the actual science and engineering, and if it screws up someone's sales pitch, OH WELL!

 

[SIY]

https://www.stereophile.com/reference/1095cable

A little bit of interesting reading.

Famously and humiliatingly wrong.

 

[AnalogSteph]

There's one place I can think of where low-inductance resistors do in fact make a difference - output stage emitter resistors. Types with high inductance can be detrimental to amplifier stability there, so some attention to parts selection is warranted whenever you have to replace some or pick them in the first place. Instability may show up as excessive distortion and/or noise, or you might not notice at all if it's low amplitude and high up (as in the MHz region), but it is definitely not desirable as its effects are sort of unpredictable.