Proof that speaker cables make a difference

[Speedskater]

The wavelength of 20kHz is less than an inch!

That's for sound traveling thru the air.
This discussion is about electrical signals traveling thru wires.

 

[preload]

Don't forget that in a passive crossover there is already more inductance, capacitance and resistance in that crossover than in the any speaker wire you are talking about. The greatest contributor to all that crap between the amplifier and the driver is not the cable, its the passive crossover.

Right and the resulting frequency response of the loudspeaker should already account for the effects of the passive crossover network.

 

[preload]

To add to your information this is handy too. One would need a fair amount of cable for a 2 Ohm wire.

This is true. However, even adding 1 ohm translates to a whopping 2dB difference at 300Hz and 10kHz in Russel's example. At a fraction of an ohm, we're looking at a fraction of a dB, but this is JUST considering DC resistance. We still haven't accounted for the differences in inductance across cables, which "adds" a varying amount of impedance as a function of the frequency on top of the DCR.

To be clear, I'm not saying that differences in R and L in real world loudspeaker cables make HUGE differences in perceived sound quality, as is often claimed. But using commonly accepted characteristics (i.e. applicable LCR figures and not non-applicable transmission line theory), the amount of FR deviation might be "potentially audible." That's my point.

 

[MDAguy]

the only reason I have nice cables (and they're not crazy expensive or anything like that)... is they look pretty cool.... I don't know if my 51 year old ears can hear the difference, but my eyes sure like the way those beefier cables look attached to my boxes!

 

[egellings]

If you mention the "speed of audio @ 20kHz", please be sure to state whether it's through air, a wire or whatnot.

 

[MDAguy]

If you mention the "speed of audio @ 20kHz", please be sure to state whether it's through air, a wire or whatnot.

right, because those wave lengths and amplitudes will vary dramatically, right?

 

[solderdude]

20kHz wavelength in cable: around: 15km
20kHz wavelength (acoustic) in air: 17mm
20kHz wavelength (acoustic) in water: 80mm
20kHz wavelength (acoustic) in steel: 0.3m
20kHz wavelength (acoustic) in glass: 0.2m

 

[Chrispy]

20kHz wavelength in cable: around 15km
20kHz wavelength (acoustic) in air 17m
20kHz wavelength (acoustic) in water 80m

Wouldn't that air one be for 20 hz?

 

[solderdude]

Wouldn't that air one be for 20 hz?

yep, was in mm so edited it.

 

[egellings]

The harder the material, the faster sound (acoustic) goes through it.

 

[lemnoc]

The high value woofer resistors are more likely in parallel with the speaker driver, and would not directly add to the resistance of the cable.

And the typical DC resistance of a voice coil is what compared to the resistance of the speaker cables ??

 

[RayDunzl]

The harder the material, the faster sound (acoustic) goes through it.

I wonder how the "hardness" of a gas is determined...

 

[solderdude]

I wonder how the "hardness" of a gas is determined...

View attachment 96533

by measuring the speed of sound in a gas at a specific temperature ?

 

[thewas]

I wonder how the "hardness" of a gas is determined...

By the bulk modulus which the counterpart of solids stiffness:

Speed of sound in ideal gases and air

For an ideal gas, K (the bulk modulus in equations above, equivalent to C, the coefficient of stiffness in solids) is given by

thus, from the Newton–Laplace equation above, the speed of sound in an ideal gas is given by

where

• γ is the adiabatic index also known as the isentropic expansion factor. It is the ratio of the specific heat of a gas at constant pressure to that of a gas at constant volume (
  
  ) and arises because a classical sound wave induces an adiabatic compression, in which the heat of the compression does not have enough time to escape the pressure pulse, and thus contributes to the pressure induced by the compression;
• p is the pressure;
• ρ is the density.

Source: https://en.wikipedia.org/wiki/Speed_of_sound#Speed_of_sound_in_ideal_gases_and_air

 

[Max Townshend]

Townshend is inviting you to a scheduled Zoom meeting.

Time: Dec 5, 2020 18:00 GMT


Topic: Townshend cable measurements Demo + Q&A.


To demonstrate that characteristic impedance matters in the case of speaker cables.

Forum questions regarding voltage and oscilloscope timebase settings will be addressed.


The session will have the following format:


A brief overview of the paper.

Introduction of the test set-up.

A live repeat of the experiment.

An opportunity to discuss the theory and test practices.

To facilitate preparedness, should you have any specific questions, please feel free to pre-submit them to us. This is not a requirement.

Open section for ad hoc or any further questions concerning cable testing.




Join Zoom Meeting

https://zoom.us/j/93569703283?pwd=Q3hHOStzU0dENnArY0lGV2F3ZGJFZz09



Meeting ID: 935 6970 3283

Passcode: JYzH2K



The session will be recorded.

 

[Propheticus]

My first and last question: is an (additional) drop of 0.1dB @ 20kHz audible?
(hint: I already know the answer, but try to make a point here)
I do not need to waste my time attending a demo that shows cables measure differently. This is known. When measured accurately enough you will indeed find differences. For a stretch of max 3m, with sufficient gauge, they are however so minute they are inaudible....and with a big margin from becoming audible.

Thanks for the invite. I pass.

 

[Max Townshend]

OK. Here is figure 2 from the BS Audio article. You can see that both branches in the circuit have inductors, which block high frequencies. The left branch has a 330 uH one (lower than the right branch), and will have a lower impedance at high frequencies. At 100 kHz, ω=6.283e5 rad/s. Impedance (Z) from the 330 uH inductor is 1j*L*ω = 207j Ω. There is no way the impedance curve can level to 8 Ω at high frequencies. The impedance of this circuit rise to infinity as frequency goes to infinity.

So figure 2 alone is totally bogus. A total fail at basic electrical circuit. I am now afraid of these people with anything electrical. Can I stop now?

View attachment 94544

I checked back and the graph is wrong, thanks for pointing that out. The circuit shown is with 2.2uF 10R Zobel. The attached graph is (approximately) correct.

 

[MDAguy]

Why not do a Null Test between two cables? A standard OEM type cable, and a Townsend cable? Keep it in the realm of human audible range and, then we know for sure if there is anything different?

Or am I missing something here?

 

[Speedskater]

I checked back and the graph is wrong, thanks for pointing that out. The circuit shown is with 2.2uF 10R Zobel. The attached graph is (approximately) correct.

What test equipment model did you use to measure that impedance curve?

 

[Mike B]

Can we get a shirt that says, "Cable denier"?