My amplifier output and speakers have a Z of 8 ohms.
Would it be ok if I use 185 ohms speaker cable?
I was thinking of the RG114 coaxial.
What is the impedance of these paralleled wires speaker cables, I think it should be much more than 8 ohms...
Would it be ok if I use 185 ohms speaker cable?
I was thinking of the RG114 coaxial.
What is the impedance of these paralleled wires speaker cables, I think it should be much more than 8 ohms...
The 185 Ohm of course refers to coaxial cable characteristic impedance, i.e. how the cable impedance manifests itself when exposed to high enough frequencies. If this is just a few meters, I seriously doubt it will act as a transmission line at audio frequencies.
However, I am not sure how a thin coaxial shield will handle high currents. I wouldn't do it myself, as there is an abundance of cables around with higher Cu cross-section.
Anyway, impedance matching of loudspeaker cables is practically irrelevant due to the reason above.
However, I am not sure how a thin coaxial shield will handle high currents. I wouldn't do it myself, as there is an abundance of cables around with higher Cu cross-section.
Anyway, impedance matching of loudspeaker cables is practically irrelevant due to the reason above.
Cables need to be KILOmeters long to exhibit transmission line effects in the audio band.
Parallel C and series R are the only important parameters, both easily measured.
Parallel C and series R are the only important parameters, both easily measured.
I see what you mean..
I was thinking of the RG114 coaxial because of it's low shunt capacitance. But in speaker cables this is not quite important..?
on interconnects where the I/O impedance is high this should play a greater role but if short cable lengths are used this should not be too much of a problem...?
The conductor materials are quite important and especially the external surfaces of the conductors due to skin effect transfer...?
Are my considerations correct?
I was thinking of the RG114 coaxial because of it's low shunt capacitance. But in speaker cables this is not quite important..?
on interconnects where the I/O impedance is high this should play a greater role but if short cable lengths are used this should not be too much of a problem...?
The conductor materials are quite important and especially the external surfaces of the conductors due to skin effect transfer...?
Are my considerations correct?
I was thinking of the RG114 coaxial because of it's low shunt capacitance. But in speaker cables this is not quite important..?
Generalisation are dangerous. Do the maths, it is easy! C/foot x length = total capacitance. Is you amp happy with that? To most it is not a problem, but to some dangerous and destructive.
on interconnects where the I/O impedance is high this should play a greater role but if short cable lengths are used this should not be too much of a problem...?
Once again, it is easy to calculate the roll-off due to the output impedance and the cable C.
The conductor materials are quite important and especially the external surfaces of the conductors due to skin effect transfer...?
In what way "quite important"? Resistance is the property in question, and once again easily measured, unless you are into magic properties.
Skin effect may become apparent to the tune <1dB at 20Khz in "normal" cables. Again this is easy to estimate.
In general, robust lengths of copper as short as is reasonable will give no problem.
Generalisation are dangerous. Do the maths, it is easy! C/foot x length = total capacitance. Is you amp happy with that? To most it is not a problem, but to some dangerous and destructive.
on interconnects where the I/O impedance is high this should play a greater role but if short cable lengths are used this should not be too much of a problem...?
Once again, it is easy to calculate the roll-off due to the output impedance and the cable C.
The conductor materials are quite important and especially the external surfaces of the conductors due to skin effect transfer...?
In what way "quite important"? Resistance is the property in question, and once again easily measured, unless you are into magic properties.
Skin effect may become apparent to the tune <1dB at 20Khz in "normal" cables. Again this is easy to estimate.
In general, robust lengths of copper as short as is reasonable will give no problem.
Cliff?
Surely we're not talking more than a few nFs per cable here?
(Maybe we should stop here before another cable war breaks out) 🙄
Surely we're not talking more than a few nFs per cable here?
(Maybe we should stop here before another cable war breaks out) 🙄
nF? not surely! we are talking about something like 20-100pF/m actually. If you have something like 2-3m, like in my case, this is far less than 1nF..
Almost certainly not. But you, too, are guessing 😀😀
Why not simply measure it and sleep soundly at night?
Lossy Cable
Hi All;
All the capacitance discussion is burying the real issue.
The centre conductor is .007" diameter; roughly the equivalent of 33AWG wire.
Hope it's short run.😀
If you want low capacitance (for whatever reason) a better way is to use two conductors spaced by some distance such as basic twin conductor speaker cable with a web in between.
Intrinsically capacitance will be highest with a coax construction (all other things being equal) due to the higher cross section of conductor presented to each other (the entire outer surface of the inner conductor sees the entire inner surface of the outer conductor). While this confers good shielding properties, it offers in general higher capacitance between the coductors and the only way to reduce this (as is done in RG114A) is to use an inner conductor with small surface area and to reduce the dielectric constant of the cable deilectric by filling it with air. In this case the inner conductor would be too small for most people to even work with.
Good luck
Matt
Hi All;
All the capacitance discussion is burying the real issue.
The centre conductor is .007" diameter; roughly the equivalent of 33AWG wire.
Hope it's short run.😀
If you want low capacitance (for whatever reason) a better way is to use two conductors spaced by some distance such as basic twin conductor speaker cable with a web in between.
Intrinsically capacitance will be highest with a coax construction (all other things being equal) due to the higher cross section of conductor presented to each other (the entire outer surface of the inner conductor sees the entire inner surface of the outer conductor). While this confers good shielding properties, it offers in general higher capacitance between the coductors and the only way to reduce this (as is done in RG114A) is to use an inner conductor with small surface area and to reduce the dielectric constant of the cable deilectric by filling it with air. In this case the inner conductor would be too small for most people to even work with.
Good luck
Matt
How much of this RG114 coax have you got.
I'm thinking of the work done by Townshend Audio where multiple coax cables are used to acheive a 8 ohm impedance matched cable.
Unfortunately this would involve parallelling over 20 cables if they are 185ohms impedance each!
An interesting Youtube video on speaker cables, by Max Townshend
YouTube - Townshend Audio Isolda Speaker Cable "geometry matters"
And a link to the cables on his website
Isolda speaker cable
I'm thinking of the work done by Townshend Audio where multiple coax cables are used to acheive a 8 ohm impedance matched cable.
Unfortunately this would involve parallelling over 20 cables if they are 185ohms impedance each!
An interesting Youtube video on speaker cables, by Max Townshend
YouTube - Townshend Audio Isolda Speaker Cable "geometry matters"
And a link to the cables on his website
Isolda speaker cable
That Max Townshend ad is so full of BullCrap, I couldn't finish reading it. Characteristic impedance of speaker cables is irrelavant at audio frequencies unless you're planning to use extremely long cables, and even then, resistive losses will be much more important. Just use regular, good quality speaker cable, and don't obsess about insignificant details.
Well his turntable certainly works. I've owned an Rock Turntable for many years!
BullCrap aside I thought that the thinking behind these cables was relevant to a discussion about using coaxial cables for speakers.😉
For feeding speakers the first, and almost only, priority is low resistance. This means fairly thick cables made of a good conductor such as copper. In addition, you want fairly low capacitance - which means avoid coax. High capacitance can cause instability in some amps. You also want fairly low inductance - thick conductors kept close together gives this. Any extra effort to reduce, say, inductance by doing fancy weaves of a multistrand will increase capacitance so you can't win. A flat cable has low inductance but again increases capacitance, although by less than the multiweave. Just buy decent ordinary speaker cable.
Characteristic impedance is irrelevant unless your speakers are at the far end of the street, and even then the resistance will dominate. You are not matching to 8 ohms - both the amp and the speaker don't look much like 8 ohms at any frequency anyway.
The RF characteristic impedance of the cable has a slight relevance if you want to damp out any possible RF resonances (which can increase RF pickup), by adding a resistive network at one end.
Characteristic impedance is irrelevant unless your speakers are at the far end of the street, and even then the resistance will dominate. You are not matching to 8 ohms - both the amp and the speaker don't look much like 8 ohms at any frequency anyway.
The RF characteristic impedance of the cable has a slight relevance if you want to damp out any possible RF resonances (which can increase RF pickup), by adding a resistive network at one end.
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