Speaker Wire and Effective Damping Factor

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AmpDesigner333

Speaker Wire and Effective Damping Factor
« on: 17 May 2018, 05:48 am »
Speaker Wire resistance can kill damping factor.  This is especially important with low impedance, high power amplifiers.

The load (speaker) is connected to the amplifier output in series with the amplifier's output resistance AND the speaker wire's resistance.

As a fun math experiment, compare the output resistance (impedance simplified) of a high performance amp, like Maraschino, which is less than 10mΩ before the connectors (both) and about 16mΩ after.  This results in a damping factor of 500 into an 8Ω load.  If the speaker wire has a resistance of 16mΩ, that would cut the effective damping factor in HALF (now effectively 250)!

Now, add TWICE (round trip) the resistance of a 6-foot wire....
    10-gauge is 12mΩ
    12-gauge is 19mΩ
    14-gauge is 30mΩ
    16-gauge is 48mΩ

Damping factor is just load resistance divided by output resistance.

So, an amp with a damping factor of 500 and (16mΩ output resistance into 8Ω) driving a load through a 6-foot 16-gauge speaker wire has an EFFECTIVE damping factor of only 125!

What do you think happens when an In-Line Maraschino is used, hanging from the speaker with 6" (that's INCHES!) long 12-gauge wires?  Hint: 1-foot of 12-gauge is only 2mΩ....

Folsom

Re: Speaker Wire and Effective Damping Factor
« Reply #1 on: 17 May 2018, 06:00 am »
Funny how a bunch of people just got done telling me that it doesn't do anything :roll:

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #2 on: 17 May 2018, 06:01 am »
Handy table....

1000 ft of 8 gauge: 0.628 Ω
1000 ft of 9 gauge: 0.792 Ω
1000 ft of 10 gauge: 0.999 Ω
1000 ft of 11 gauge: 1.26 Ω
1000 ft of 12 gauge: 1.588 Ω
1000 ft of 13 gauge: 2.003 Ω
1000 ft of 14 gauge: 2.525 Ω
1000 ft of 15 gauge: 3.184 Ω
1000 ft of 16 gauge: 4.016 Ω
1000 ft of 17 gauge: 5.064 Ω
1000 ft of 18 gauge: 6.385 Ω
1000 ft of 19 gauge: 8.051 Ω
1000 ft of 20 gauge: 10.15 Ω

Speedskater

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Re: Speaker Wire and Effective Damping Factor
« Reply #3 on: 17 May 2018, 05:02 pm »
Funny how a bunch of people just got done telling me that it doesn't do anything :roll:
It's not that it doesn't do anything, it's that when the damping factor gets well above 10 it's further impact quickly diminishes.

What they are hearing is the effect of added series resistance causing response changes with frequency. Just look at the Stereophile measurements of some tube amps (just about the effect).

Johnny2Bad

Re: Speaker Wire and Effective Damping Factor
« Reply #4 on: 17 May 2018, 05:24 pm »
The explanation covers only half the story.

Effective Damping Factor values for calculation includes:

 > 1 run speaker cable > resistance of crossover elements > voice coil resistance > 1 run of speaker cable
(ignoring for the moment the effect of various connectors, etc which would further increase the above value).

A value of 20 or higher is adequate.


AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #5 on: 17 May 2018, 09:46 pm »
It's not that it doesn't do anything, it's that when the damping factor gets well above 10 it's further impact quickly diminishes.

What they are hearing is the effect of added series resistance causing response changes with frequency. Just look at the Stereophile measurements of some tube amps (just about the effect).
How do you come to this conclusion?  Lower damping factor means less control over the speaker.  More control typically means better, more accurate sound.

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #6 on: 17 May 2018, 09:56 pm »
The explanation covers only half the story.

Effective Damping Factor values for calculation includes:

 > 1 run speaker cable > resistance of crossover elements > voice coil resistance > 1 run of speaker cable
(ignoring for the moment the effect of various connectors, etc which would further increase the above value).

A value of 20 or higher is adequate.
How do you come to that conclusion?

Speaker system are typically designed to assume near zero source impedance.  The voltage at the speaker terminals does NOT include resistances "inside the box".  Think of it as a black box, and your job as an amplifier is to deliver the most accurate signal to the black box.

planet10

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Re: Speaker Wire and Effective Damping Factor
« Reply #7 on: 18 May 2018, 04:48 am »
A value of 20 or higher is adequate.

+1

Or another way of putting it, anything over 20 brings you vanishingly little.

dave

planet10

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Re: Speaker Wire and Effective Damping Factor
« Reply #8 on: 18 May 2018, 05:13 am »
Lower damping factor means less control over the speaker.  More control typically means better, more accurate sound.

The 1st is true (but implies that each speaker needs maximum control). The 2nd is baldface misinformation.

A speaker/amplifier system to sound most accurate needs to have a range of total damping. A amplifer can provide a certain amount of electrical damping. A speaker has an inherent mehcanical damping. These add up to give total damping. If the amplifier has too low an output impedance (high damping) can overdamp a speaker and cause lean bass.

Now it is true that many (if not most) speakers available today are designed with the assumption that the amps has a high damping factor (ie >20). If you own one of those speakers you should get an amplifier with high damping or you may find that the bass is towards bloated/fat. But there are speakers available (even more common in the diyWorld) where the speaker likes to see a higher output impedance because they have high meanical damping so don’t need so much electrical damping.

This can be taken further. Since a speaker is a current driven device, there is an argument that an amplifier that is a current source will have all sorts of lesser distortions. So it sounds better. But only practical if the impedance is close to flat since the FR of a speaker driven by a current source will be convolved with the speakers impedance. Almost every speaker with a crossover will not satisfy this criterion — the crossover makes the impedance take a wild ride. Also we have the speaker’s fundemental resonance which is typically shown by a big rise in impedance, a sign of an underdamped situation where extra electrical damping is beneficial. So to use a current amp you either need a speaker with very well behaved impedance (very rare) or use current amps in an active system for mid/top where over the bandwidth of the directly driven loudspeaker the impedance is flat, and use a voltage amp for the bass because the speaker does not have a flat-curve.

Also, with a single driver FR system, the impedance rises at the bottom and at the top. and an amplifier with just the right output impedance can extend the flat frequency range both up & down. Experiments with a constinuously variable Transimpedance amplifier (output impedance can be dialed from near 0 to near infinity) that each different loudspeaker had an optimal setting.

So what is the best damping? It depends. The OP is trying to stir up a tempest in a teapot.

dave

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #9 on: 18 May 2018, 05:25 am »
+1

Or another way of putting it, anything over 20 brings you vanishingly little.

dave
Based on what?  I've heard the difference, and much more.  So you know I'm not just making baseless claims, I'm an electrical engineer with 30+ years experience in audio (consumer and pro), plus military, medical, fire safety, and even toys.  That's design experience from concept to production.  I've been able to connect the dots between measurements and sound.  This is through circuit changes, measurements, and listening.

I can say for a fact that higher effective damping factor sounds better on systems that have adequate resolution.  This is the reason I brought it up in the first place.  Speaker wire (or "just straight wire") is low enough inductance that its inductance is negligible.  Speaker wire is low enough capacitance that its capacitance is negligible.  The resistance is NOT negligible, and damping factor matters!

Take a look at what people say about Cherry Amplifiers!  Why are so many people saying it's the best sounding amp they've ever had?  We do things right, and low impedance is one of those things.  Pay special attention to the ILM (In-Line Maraschino) owners.  Many of them HANG the amps from their speakers.  The result?  Speaker wires with less than one foot of round trip length ---- near-ZERO speaker wire resistance.  We're talking about less than a milliohm!  The sound delivered by these high performance (117dB+ SNR, 0.002% THD, 0-100kHz), small, light (they weigh about a pound), yet very powerful (up to 1000W into 1.8 ohms!) amps is nothing short of amazing.  Here are some reviews on Cherry Amps:
https://www.audiocircle.com/index.php?topic=127654.0

If you think a 1960s technology audio system sounds just swell, than higher damping factor, wider bandwidth, DC coupling, true balanced operation, super low noise, super low distortion, and adequately low speaker wire resistance won't help you.  Hey, some people are perfectly happy driving a Yugo.

planet10

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Re: Speaker Wire and Effective Damping Factor
« Reply #10 on: 18 May 2018, 05:48 am »
Based on what?  I've heard the difference, and much more.  So you know I'm not just making baseless claims, I'm an electrical engineer with 30+ years experience in audio (consumer and pro), plus military, medical, fire safety, and even toys.

Me too. And possibly over a much wider range of loudspeakers. 45+ years in audio. And while no engineering degree (1st half of one, but i started with an honours math degree 1st) an engineering mind. And i like to leave it open. Engineering will let you comfortabley generate numbers, but if you include everything in the circuit and damping factor greater than about 20 adds vanishing little to the end result. Much as Johnny2Bad has already done for us in this thread.

dave

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #11 on: 18 May 2018, 05:59 am »
Me too. And possibly over a much wider range of loudspeakers. 45+ years in audio. And while no engineering degree (1st half of one, but i started with an honours math degree 1st) an engineering mind. And i like to leave it open. Engineering will let you comfortabley generate numbers, but if you include everything in the circuit and damping factor greater than about 20 adds vanishing little to the end result. Much as Johnny2Bad has already done for us in this thread.

dave
Dave,

So we can agree to disagree.  In my experience, it matters more with high performance hardware (measurement and SQ wise).  Lower speaker wire resistance won't do much if you're using an already handicapped tube amp with poor damping factor, rolled off highs, and high noise, for example.  Have you ever heard a Cherry Amp?  Have you checked out the link I included above?  Have a great night.  It's pretty late here in Allentown PA....  Thanks for contributing to my board.

-Tommy O

p.s. Check out this thread started by a customer that went from a life of tubes to Cherry Amps ("SHATTERED GLASS … No more tubes – Class D all the way baby and loving it!"):
https://www.audiocircle.com/index.php?topic=154294.0

planet10

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Re: Speaker Wire and Effective Damping Factor
« Reply #12 on: 18 May 2018, 06:14 am »
… you're using an already handicapped tube amp with poor damping factor, rolled off highs, and high noise, for example.  Have you ever heard a Cherry Amp? 

Your amps are on my long lost of amps i’d like to hear. And i’m guessing that  the tube amps of which you are talking are those pretty much emulating the crap of the past. There are some VERY good tube amps.

To quote WindChaser from that thread:
Quote
… how much better it mated with my speakers…

Exactly. Just like i said in my long post… with his speaker. And i also said most loudspeakers need an amp like yours.

dave

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #13 on: 26 May 2018, 11:31 am »
Check out my post on this thread about solid versus stranded wire:
https://www.audiocircle.com/index.php?topic=157556.msg1688249#msg1688249

Speedskater

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Re: Speaker Wire and Effective Damping Factor
« Reply #14 on: 27 May 2018, 01:15 pm »
F. Langford Smith wrote about this in 1947.
Industrial audio consultant Dick Pierce wrote this paper in 2002:

"Damping Factor: Effects On System Response"
Dick Pierce
Professional Audio Development

http://www.cartchunk.org/audiotopics/DampingFactor.pdf
http://www.cartchunk.org/

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #15 on: 28 May 2018, 07:40 pm »
F. Langford Smith wrote about this in 1947.
Industrial audio consultant Dick Pierce wrote this paper in 2002:

"Damping Factor: Effects On System Response"
Dick Pierce
Professional Audio Development

http://www.cartchunk.org/audiotopics/DampingFactor.pdf
http://www.cartchunk.org/
Not one mention of speaker reactance!  Translated: obvious bias toward low performance amplification

Speedskater

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Re: Speaker Wire and Effective Damping Factor
« Reply #16 on: 28 May 2018, 08:42 pm »
Not one mention of speaker reactance!  Translated: obvious bias toward low performance amplification
That's because system 'Qr' which is what this is all about is measured at resonate frequency where the reactances cancle out.

AmpDesigner333

Re: Speaker Wire and Effective Damping Factor
« Reply #17 on: 29 May 2018, 04:40 am »
That's because system 'Qr' which is what this is all about is measured at resonate frequency where the reactances cancle out.
If you're looking at a simple resistance (representing output impedance of the amp at a given freq) driving a reactive network, there is no "cancelling out" of the reactance.  Here's an interesting article I found regarding speaker reactance:
https://hometheaterhifi.com/technical/technical-reviews/a-secrets-technical-article/

Zero output impedance is ideal, although unattainable, so the lower the better, but where does it stop making a difference?  I like to look at it as orders of magnitude, and two orders of magnitude (minimum, as a rule of thumb concerning impedance ratios) gives us a damping factor of 100.  This is only attainable with adequately low speaker wire resistance.  Note that some speakers dip very low impedance wise (under 2 ohms, like some ESLs, and Gallo speakers, those with transformers are notorious for this).  However, this static impedance number only tells half the story, and is generally an over-simplification.  There is a phase angle from the back-EMF of the speaker, and this can amount to a much worse situation than driving a simple 2 ohm resistor.  Ever wonder why some amplifiers "can't handle" low impedance speakers?  This is why some manufacturers say stuff like "stable down to 4 ohms" or "speakers less than 4 ohms are not recommended".  It's like a hockey fight ---- harder to land a solid punch when you're sliding on the ice.  The slippery ice is like high output impedance!  Simple physics, related to opposing forces.

Amps with very poor damping factor (non OTL tube amps, for example) can't fight much against the back EMF of the speaker.  This causes a "sloppy sound", especially noticeable in the bass.  Also, most amps with great damping factor only have that characteristic at low freq (100Hz, where it's typically tested, and lower), then the output impedance climbs like crazy as the freq goes up.  Some amps with high bandwidth damping attain this by applying tons of feedback, creating the need for wild phase shifts to allow stability.  This is especially the case with Class-D that wraps feedback around the output filter.  The same technique to get decent specs on paper when the amp is driven with sine waves of one or only a few frequencies (what's used for THD+N testing, for example).  Music is not a continuous tone!  The problem is that this same "high feedback" practice can cause an "etched" sound.  How many times have you heard "great bass, but harsh sounding" about one of those pre-fab module based Class-D amps?  We have conquered this issue with our patented and proprietary amplifier circuitry.  This is why users of other Class-D amps, as well as tube fans, have migrated to Cherry Amps.  Thanks.

-Tommy

planet10

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Re: Speaker Wire and Effective Damping Factor
« Reply #18 on: 29 May 2018, 05:12 am »
Zero output impedance is ideal

Given that this is false what follows does not have univesal application.

Quote
Ever wonder why some amplifiers "can't handle" low impedance speakers?

It is simple. The power supply cannot deliver sufficient current. Also the reason why some amps cannot do a decent job driving ESLs. With an ESL it is more a case of the speaker looking like a capacitor. Since Power =VA x cos(phase angle) and the closer to a capacitor the speaker is the closer cos(phase) gets to zero (and has little to do with back EMF. Esa Meriläinen’s book has a very good analysis).

Quote
Amps with very poor damping factor (non OTL tube amps, for example) can't fight much against the back EMF of the speaker.

Once the output impedance becomes greater than the speakers (damping factor <1) we get into current amp territory. With a true current amp there is no EMF. The lower an amplifier’s output impedance the greater issues it has with back EMF.

Quote
This causes a "sloppy sound", especially noticeable in the bass.

This is very dependent on the mechanical damping of the loudspeaker system — if the impedance curve is flat at resonance the speaker has a well damped bass response and a high damping amplifier will sound very thin prodcuing lss than ideal bass.

Quote
most amps with great damping factor only have that characteristic at low freq (100Hz and down)

Duh. Given that damping factor only has a real effects in the region of the speaker's resonance frequency.

dave

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Re: Speaker Wire and Effective Damping Factor
« Reply #19 on: 29 May 2018, 06:01 am »
\https://hometheaterhifi.com/technical/technical-reviews/a-secrets-technical-article/

The real purpose of this article is to show the Smith chart of impedance and the intro has some shortcomings in terms of not telling the whole story (and some untruths — ie a tweeter’s impedance is not capacitive). What we have with the 3 impedance plots shown here are just what one sees when one looks at the 3D impedance curve (Nyquist plot) collapsed into a 2d chart when looked at from a specific axis. Yje magnitude when one is looking from an axis where the imaginary parts disappear, the phase angle when collapsed from a view that hides the real data, and the Smith chart  Variation of orthoganal to both of these (ie from the end). Much better, given computer screens these days would be a 3D display and the ability to rotate the view point.



https://www.prosoundweb.com/topics/sound_reinforcement/the_nyquist_plot/#

Richard Heyser was a proponent of this and one of the audio magazines he did measures for showed a Smith curve (or similar). http://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf

dave