Speaker wire

[fpitas]

On which physical principle should a lower frequency signal modulate the a higher frequency signal in a wire? This is not a voltage divider or a total current brickwall limiter.

If there is non-linearity in the wire resistance, or (more probably) in the woofer current draw, you'll get some intermod. It's something to think about, but not real straightforward.

 

[sarumbear]

On which physical principle should a lower frequency signal modulate the a higher frequency signal in a wire? This is not a voltage divider or a total current brickwall limiter.

I already said: Ohms law. The voltage drop caused by the bass signal, which has the most energy, hence causes the most voltage drop is also applied to the high frequency signal. In other words low frequencies start to modulate the high frequencies.

 

[thewas]

If there is non-linearity in the wire resistance, or (more probably) in the woofer current draw, you'll some intermod. It's something to think about, but not real straightforward.

The "problem" is there isn't such, at least not in the typical audio frequencies band, that's why for example no IMD measurements for cables are performed.
The change of the loudspeaker impedance depending on frequency is something that is long considered and the reason why amplifiers with low damping factor are needed but even this doesn't cause any modulation, but just a change of the FR.

 

[sarumbear]

If there is non-linearity in the wire resistance, or (more probably) in the woofer current draw, you'll get some intermod. It's something to think about, but not real straightforward.

You don’t need non linearity in the cable. The bass signal has vastly more power hence causes much more voltage drop then high frequencies.

 

[fpitas]

The "problem" is there isn't such, at least not in the typical audio frequencies band, that's why for example no IMD measurements for cables are performed.
The change of the loudspeaker impedance depending on frequency is something that is long considered and the reason why amplifiers with low damping factor are needed but even this doesn't cause any modulation, but just a change of the FR.

Right, we're in agreement for the most part.

 

[sarumbear]

The "problem" is there isn't such, at least not in the typical audio frequencies band, that's why for example no IMD measurements for cables are performed.
The change of the loudspeaker impedance depending on frequency is something that is long considered and the reason why amplifiers with low damping factor are needed but even this doesn't cause any modulation, but just a change of the FR.

I disagree as either I can’t explain the phenomena to you or you fail to see what’s happening.

 

[fpitas]

You don’t need non linearity in the cable. The bass signal has vastly more power hence causes much more voltage drop then high frequencies.

Not meaningful unless it causes mixing of some sort, which takes a non-linearity.

BTW, by "mixing" I mean in the RF sense, producing sum and difference frequencies.

 

[sarumbear]

Not meaningful unless it causes mixing of some sort, which takes a non-linearity.

Bass and treble are send mixed through the same wire.

 

[fpitas]

Bass and treble are send mixed through the same wire.

Nomenclature, sorry. "Mixing" in the broader electronics world produces sum and difference frequencies.

Frequency mixer - Wikipedia

en.wikipedia.org

 

[sarumbear]

Nomenclature, sorry. "Mixing" in the broader electronics world produces sum and difference frequencies.

Frequency mixer - Wikipedia

en.wikipedia.org

If they are separate sources. In this case there is one source, one power amplifier output.

 

[thewas]

I already said: Ohms law. The voltage drop caused by the bass signal, which has the most energy, hence causes the most voltage drop is also applied to the high frequency signal. In other words low frequencies start to modulate the high frequencies.

Typical loudspeaker cables have a constant impedance in the audio frequency band so the voltage drop in proportional to signal output and there is thus no frequency response change. Even if it wouldn't be constant it would just cause a linear distortion (frequency response change) but no intermodulation, as for this a non-linear behaviour is necessary and such doesn't exist in the cable, at least in the low frequency range we are talking about.

 

[fpitas]

If they are separate sources. In this case there is one source, one power amplifier output.

It always takes non-linearity, though. Otherwise, no new frequencies are created.

 

[dualazmak]

As I already wrote here;

In my multichannel multi-driver (multi-way) multi-amplifier stereo project, I need to use so many (and rather long, in my case) SP cables. I have been sticking to very reasonable (cheap) tin-plated Y-lugs and AWG10/AWG12 multicore vinyl cabtyre cables with great satisfactions as I shared here and here.

After my 30-year try-and-error journey, now I definitely believe that these very cheap tin plated pure copper Y-lugs and R-lugs are the best terminal-contact solution since rather soft metal tin plate effectively increases the contact surface area when tightly connect and squeeze;

Furthermore it is critically important to eliminate any magnetic susceptible metals in handling of speaker level signals as I shared in my posts here and here.

You can find the latest backside cabling photos of my amplifiers and SP drivers here on my project thread) and here (post #636 on that thread).

 

[Suffolkhifinut]

I meant the Ampere lev orel?

They are all laid out in BS7678 (IEE) Regulations), although if you're not in the trade there are many variables to be taken into account. Ambient temperature, length of run, single core, multicore, type of enclosure and several others.
If you're dealing with 2core flexible cord in open air then as a rule of thumb, 1.5mm2 - 15 Amps, 2.5mm2 - 25 amps. You shouldn't need to go bigger than 2.5mm2 and don't forget cords with a PVC insulation and/or sheath should not be exposed to direct sunlight for lengthy periods of time.

 

[Killingbeans]

Furthermore it is critically important to eliminate any magnetic susceptible metals in handling of speaker level signals as I shared in my posts here and here.

I don't see any indication of it being critical?

You mention something about "blur", but give no practical examples and no explanation of the supposed physics responsible for this effect?

 

[MAB]

Furthermore it is critically important to eliminate any magnetic susceptible metals in handling of speaker level signals as I shared in my posts here and here.

Actually, @ctrl analyzed this. It’s gonna take a ton of magnetically susceptible materials to have an audible impact. We should thank nature for this, otherwise our world would be very sensitive place with some very strange and surprising electrical phenomena!

Different Binding Posts - is it audible?

The influence of BP on the sound of loudspeakers has often been controversially discussed. It even goes so far that individual voices describe the influence of binding posts as immense and recommend only very high-quality BPs - That made me curious. The full mini series: Capacitor...

www.audiosciencereview.com

So, no not much impact due to this phenomenon.

 

[thewas]

Typical loudspeaker cables have a constant impedance in the audio frequency band so the voltage drop in proportional to signal output and there is thus no frequency response change. Even if it wouldn't be constant it would just cause a linear distortion (frequency response change) but no intermodulation, as for this a non-linear behaviour is necessary and such doesn't exist in the cable, at least in the low frequency range we are talking about.

To easier show that a signal in a linear ohmic cable won't modulate another signal lets take the above mentioned example with loudspeaker impedance Z2=4 Ohm and cable impedance Z1=0.1 Ohm which are connected in series to the amplified with output voltage Vin and thus create a simple voltage divider:

The voltage difference Vout which is applied to the loudspeaker Z2 is always proportional to the input voltage (which is the output voltage of the ampifier), namely according to the equation:

so in this case 4/(0.1+4)=0.976 thus 97,6 % of the input voltage from the amplifier.

Now lets assume a high frequency sine with an amplitude of +-1 V, at the loudspeaker the maximum applied voltage of the sine will be 1 V * 0.976 = 0,976 V and the minimum one -1 V * 0.976 = -0,976 V and thus the total amplitude of the sine will be 0,976 V - (-0,976 V) = 1,952 V.

Now lets add to it a low frequency oscillation which at the point of observation has an amp output value of 10V, the high frequency since will be added to it making the output of the amp oscillate between 10 V +1 V = 11 V and 10 V - 1 V = 9 V. The loudspeaker will see at those points maximum 11 V * 0.976 = 10,736 V and minimum 9 V * 0.976 = 8,784 V and thus the amplitude of the high frequency sine will be 10,736 V - (-8,784 V) = 1,952 V and thus the same as above, the beauty of LTI systems.

 

[Speedskater]

OK, so this is what is happening:
The cable and the loudspeaker form a series circuit (so 'series circuit' rules apply)
a] the cables has about the same impedance at all frequencies.
b] a multi-driver loudspeaker may have low impedance and high impedance points at different frequencies.
the cable & speaker act as a series voltage divider.
So the loudspeaker will have less voltage at the low impedance points than at the high impedance ones.

 

[fpitas]

OK, so this is what is happening:
The cable and the loudspeaker form a series circuit (so 'series circuit' rules apply)
a] the cables has about the same impedance at all frequencies.
b] a multi-driver loudspeaker may have low impedance and high impedance points at different frequencies.
the cable & speaker act as a series voltage divider.
So the loudspeaker will have less voltage at the low impedance points than at the high impedance ones.

True enough. But still, if no new frequencies are created, no intermod can result.

 

[thewas]

OK, so this is what is happening:
The cable and the loudspeaker form a series circuit (so 'series circuit' rules apply)
a] the cables has about the same impedance at all frequencies.
b] a multi-driver loudspeaker may have low impedance and high impedance points at different frequencies.
the cable & speaker act as a series voltage divider.
So the loudspeaker will have less voltage at the low impedance points than at the high impedance ones.

That is considered though at the tuning of the loudspeaker as typical hifi is designed for voltage and not current sources, a reason why for high output impedance amplifiers like many tube amps loudspeakers with a linearised impedance are needed as otherwise some extra FR sounding will result.