1.5mm or 2.5mm speaker cable

[master811]

Trying to decide on whether it's worth going for 2.5mm speaker cable for some Boston Acoustics XS. I've found some cheap OFC stuff on eBay.

The max run is probably about 10m at most (and only for the rears). Would the 2.5mm make a difference there or would 1.5mm be sufficient?

 

[Andy8421]

Master,

Any speaker cable will only make the sound worse. Thicker speaker cable will make the sound less worse.

If you stay away from the brand name cables, then the price of 2.5mm^2 is very reasonable - wire is actually pretty cheap if you dont have to pay for the advertising as well.

Some of the ebay cable has had a higher resistance when tested than would be expected, the implication being that the quality of the copper isn't as pure as it could be. Even so, ebay 2.5mm^2 with Chinese copper is still better than brand name 1.5mm^2.

If you want a known quantity, generic 2.5mm^2 cable, try

79 Strand Twin Fig 8 Speaker Cable

Very similar to QED 79 strand, which was the benchmark speaker cable before cable manufacturers discovered marketing departments. This cable has been tested by a forum member, and found to be of good quality.

There are 'rule of thumb' calculations that look at total cable resistance as a % of speaker load resistance, but I wouldn't bother fiddling about. Buy the thicker cable.

Andy.

 

[Alan Mac]

Some of the ebay cable has had a higher resistance when tested than would be expected, the implication being that the quality of the copper isn't as pure as it could be. Even so, ebay 2.5mm^2 with Chinese copper is still better than brand name 1.5mm^2.

The samples of the Chinese “copper” conductor that we tested were very poor indeed.

It would take a cable with 4 mm² cross-sectional-area (CSA) conductors of this Chinese “copper” to roughly equal the resistance of the “TLC” or other good quality cable with 1.5 mm² CSA conductors.

To equal good quality 2.5 mm² CSA copper conductors would require a “Chinese” cable with conductors having a CSA of more than 6 mm².


http://www.avforums.com/forums/inte...t-speaker-cables-have-resistance-figures.html



Alan

 

[master811]

The samples of the Chinese “copper” conductor that we tested were very poor indeed.

It would take a cable with 4 mm² cross-sectional-area (CSA) conductors of this Chinese “copper” to roughly equal the resistance of the “TLC” or other good quality cable with 1.5 mm² CSA conductors.

To equal good quality 2.5 mm² CSA copper conductors would require a “Chinese” cable with conductors having a CSA of more than 6 mm².


http://www.avforums.com/forums/inte...t-speaker-cables-have-resistance-figures.html



Alan

I take it there is no way of really knowing the source/purity of the copper on eBay, or should I assume all of the cheap say 1.5mm or 2.5mm cable is Chinese? Would all of the cable that has a clear plastic insulator on there be Chinese stuff?

Also, would the insulation of the wire have a significant effect on the weight of the reel? i read through your link above and emailed sellers on eBay about the weight of 2.5mm 100m cable and one came back with "about 4.5kg". Is that what you should expect?

 

[Andy8421]

The samples of the Chinese “copper” conductor that we tested were very poor indeed.

It would take a cable with 4 mm² cross-sectional-area (CSA) conductors of this Chinese “copper” to roughly equal the resistance of the “TLC” or other good quality cable with 1.5 mm² CSA conductors.

To equal good quality 2.5 mm² CSA copper conductors would require a “Chinese” cable with conductors having a CSA of more than 6 mm².


http://www.avforums.com/forums/inte...t-speaker-cables-have-resistance-figures.html



Alan

Alan,

Thanks for this.

I hadn't picked up on just how poor the Chinese copper was. I should pay more attention next time.

Master811,

If you are intent on using ebay cables, why not buy a short length first and test it? You do still have the risk of it being batch dependent, so you could possibly test a good bit, only to have the reel come from a different (poorer quality) batch.

Once you get away from the brand cables, the pricing is much more reasonable. Given the low price of the TLC cable (£44+vat for 100M), are you saving so much on the ebay stuff to make it worth the hassle of checking it out?

 

[Alan Mac]

I take it there is no way of really knowing the source/purity of the copper on eBay, or should I assume all of the cheap say 1.5mm or 2.5mm cable is Chinese? Would all of the cable that has a clear plastic insulator on there be Chinese stuff?

Also, would the insulation of the wire have a significant effect on the weight of the reel? i read through your link above and emailed sellers on eBay about the weight of 2.5mm 100m cable and one came back with "about 4.5kg". Is that what you should expect?

None of the e-Bay adverts for loudspeaker cable that I have seen specify the resistance (per unit loop length) of the conductors.

You could in principle measure the resistance of a short sample length but you would need a milli-ohm-meter (such as the Rhopoint M210 which I use).

http://www.rhopointcomponents.com/images/milliohmmeter.pdf

It would be unfair to generalise about the quality of “Chinese” sourced cables though it is true that most of the poor quality cable conductors (for mains wiring as well as for loudspeaker cables) do originate in China. But it is likely that this is simply a reflection of the fact that a large proportion of electrical and electronic goods now comes from China.

I see no reason to suppose that all cables with a clear plastic insulator have high resistivity conductors.


The volume of copper in 200 m of 2.5 mm² wire is:

200 m x 2.5 mm² x 10^-6 m²/mm²

= 0.000500 m³

The density of copper at 293 K is 8.96 Mg / m³

So the mass of the copper in the cable should be:

0.000500 m³ x 8.96 Mg / m³

= 4.45 kg

Which is close to the 4.5 kg you quote. However this does NOT prove that the conductor definitely is pure copper. It is simply consistent with the mass one would expect to measure if the conductor was pure copper, was 200 m long and had a CSA of 2.5 mm².

As Andy says, it is much simpler just to go for the 2.5 mm² cable from TLC. I think it is also available from Farnell.

The results for the sample of the TLC supplied cable that I measured were:

Loop resistance: 14.8 mΩ/m
Loop inductance: 476 nH/m
Capacitance: 63.3 pF/m

The resistivity of pure copper at 293 K is 16.8 nΩ m which puts the calculated loop resistance per unit length for 2.5 mm² CSA pure copper at 293 K at 13.8 mΩ/m .


Alan

 

[master811]

The person that came back to me was for this cable: 10m of 2.5mm Loud Speaker Cable Oxygen Free 322 Strand | eBay UK

He actually mentions the copper content, although I guess no way of knowing (short of getting a sample) how good it actually is.

 

[Alan Mac]

The person that came back to me was for this cable: 10m of 2.5mm Loud Speaker Cable Oxygen Free 322 Strand | eBay UK

He actually mentions the copper content, although I guess no way of knowing (short of getting a sample) how good it actually is.

I have now obtained a sample of this 322 strand cable.

The measured results are as follows:

Loop resistance (at “DC”) 20.6 mΩ/m

Loop inductance (at 200 kHz) 380 nH/m

Capacitance (at 200 kHz) 56.3 pF/m

The “target” resistance for pure copper, 2.5 mm² CSA, conductors is 13.8 mΩ/m.

At 20.6 mΩ/m this 322 strand cable is not as good as the TLC cable (14.8 mΩ/m).

But it is much better than the cable that “diablo” measured, which worked out at about 38 mΩ/m.


Alan

 

[master811]

I have now obtained a sample of this 322 strand cable.

The measured results are as follows:

Loop resistance (at “DC”) 20.6 mΩ/m

Loop inductance (at 200 kHz) 380 nH/m

Capacitance (at 200 kHz) 56.3 pF/m

The “target” resistance for pure copper, 2.5 mm² CSA, conductors is 13.8 mΩ/m.

At 20.6 mΩ/m this 322 strand cable is not as good as the TLC cable (14.8 mΩ/m).

But it is much better than the cable that “diablo” measured, which worked out at about 38 mΩ/m.


Alan

Thanks for that. How do I get the resistivity from that figure? Not quite sure what units you are using? is that milliohms per metre?

 

[Alan Mac]

Thanks for that. How do I get the resistivity from that figure? Not quite sure what units you are using? is that milliohms per metre?

Yes, mΩ/m is the SI standard abbreviation for milli-ohms per metre. [SI is itself an abbreviation of “Le Système International d’Unités”].


There is no need to calculate the resistivity of the conductor material [measured in ohm metres (Ω m) ]. For the purposes of ensuring that the loudspeaker cables are suitable for your application, you just need to know the RESISTANCE of the cable conductor [measured in ohms (&#937 ].

To obtain the conductor resistance for a length of cable, simply multiply the loop resistance per unit length (mΩ/m) by the cable length in metres (m).

As a general “rule of thumb”, the resistance of the cable conductor feeding the loudspeaker should have a resistance which is less than 5% of the nominal impedance of the loudspeaker. So for example, for a nominally 8 Ω loudspeaker, the cable conductor resistance should not exceed 400 mΩ.


Alan

 

[master811]

As a general “rule of thumb”, the resistance of the cable conductor feeding the loudspeaker should have a resistance which is less than 5% of the nominal impedance of the loudspeaker. So for example, for a nominally 8 Ω loudspeaker, the cable conductor resistance should not exceed 400 mΩ.

Alan

I read elsewhere, in another thread that ideally you want the loss to be less than 1% or is 5% low enough in most cases?

 

[diablo]

I read elsewhere, in another thread that ideally you want the loss to be less than 1% or is 5% low enough in most cases?

The lower the better. But whereas 1% is easy to get to in a pure stereo set-up with speakers 1.5 metres either side on an amp, for long runs you would need very thick cable to get near to that.

The most important speakers are the fronts and centre which are hopefully fairly near to your receiver.

 

[Alan Mac]

The lower the better. But whereas 1% is easy to get to in a pure stereo set-up with speakers 1.5 metres either side on an amp, for long runs you would need very thick cable to get near to that.

The most important speakers are the fronts and centre which are hopefully fairly near to your receiver.

To illustrate the effect of loudspeaker cable length on the magnitude part of the frequency response:

The attachment “LS2TLC1and5”: shows the effect of changing the loudspeaker cable from 5.4 m of 2.5 mm² “TLC” cable to 27 m of the same type of cable.

5.4 m of this cable has a loop resistance of 80 mΩ which is 1% 0f 8 Ω. 27 m of this cable has a loop resistance of 400 mΩ which is 5% of 8 Ω.

[The red trace corresponds to the 1% and the brown trace to the 5%].

The schematic of the electrical model of the loudspeaker used in the computer simulation is shown in attachment “LS2TLC5” (with the values for 27 m of cable).


Alan

 

[Starbucks78]

Sorry for digging up an old thread.

Most speaker cables are oxygen free copper, but this cable from TLC which has good feedback is referred to as 'plain annealed copper'.
I do not really understand the difference, is there a difference, is the annealed not OFC?

Maybe someone with better knowledge could please explain?

Thanks, Steve.

 

[Alan Mac]

Most speaker cables are oxygen free copper, but this cable from TLC which has good feedback is referred to as 'plain annealed copper'.
I do not really understand the difference, is there a difference, is the annealed not OFC?

Oxygen Free Copper (OFC) has no real engineering advantage over plain annealed copper for loudspeaker cable applications.


Alan

 

[Starbucks78]

Thanks, decision made then and at that price worth a gamble.

 

[mrbenn]

i've used the loads of the tlc speaker cable and its fine, great that its also cheap!

 

[Lethagized]

So glad i found this thread before buying 4mm ebay cable. Thanks to all involved in steering me away

 

[Lethagized]

Just wondered if someone could quickly answer this question. The TLC wire at 2.5mm, if i double it up, will it equal a solid core of 5mm?, or isn't that the way it works with speaker circuitry?

 

[triplecheeseburger]

Master,

Any speaker cable will only make the sound worse. Thicker speaker cable will make the sound less worse.

If you stay away from the brand name cables, then the price of 2.5mm^2 is very reasonable - wire is actually pretty cheap if you dont have to pay for the advertising as well.

Some of the ebay cable has had a higher resistance when tested than would be expected, the implication being that the quality of the copper isn't as pure as it could be. Even so, ebay 2.5mm^2 with Chinese copper is still better than brand name 1.5mm^2.

If you want a known quantity, generic 2.5mm^2 cable, try

79 Strand Twin Fig 8 Speaker Cable

Very similar to QED 79 strand, which was the benchmark speaker cable before cable manufacturers discovered marketing departments. This cable has been tested by a forum member, and found to be of good quality.

There are 'rule of thumb' calculations that look at total cable resistance as a % of speaker load resistance, but I wouldn't bother fiddling about. Buy the thicker cable.

Andy.

Am I correct in thinking that the 79 strand twin fig 8 speaker cable you mentioned is copper coated aluminium? Isn’t pure copper better?

 

[examiga1990]

God this is an old thread, but back in my HI-FI days in the 70`s I used QED `79 and thats a good starting point. I think the last stuff I was using mid 90`s was bi-wire Monster Cable that was a good few quid per metre. I would get as good a system as you can afford before going to mad on cable but start with some good stuff first. Back in the early days when we all used crap bell wire before we knew about quality cable it was amazing to hear the difference just cable made, it was like heavens doors opened to our ears. Weve come along way since. As long as you start of with a good quality record deck/cd deck, mid range amp and quality speakers you will not go to far wrong