Whats the max length speaker cable I should consider?

mattmarsden

Active Member
Due to how I want to lay out my room I'm going to need about 11m of speaker cable to each front speaker (I was thinking Silver Anniversary bi-wire). Will this length be OK and will I notice any degradation in sound as to using shorter runs?

Thanks for any advice/info
 

PSM1

Distinguished Member
11m will be fine and there will be no degradation in sound. I have over 10m going to my rears with no issues. The Silver Anniverary cable is a good cable with sufficient thickness so will work fine over that distance.
Are you planning on biwiring your fronts or just using the biwire to go to both speakers or using it to biamp the fronts? If planning to biwire I would personally save the money and not bother. As long as you have good quality cable with sufficient (Silver Anniversary Single wire is more than adequate) you will get no benefits with biwiring imho. If you pan to do one of the other 2 options (like biamp) then ignore this comment. Certainly biamping will give benefits in terms of sound quality.
 

BlueWizard

Distinguished Member
Generally, with adequate sized wire, 50 feet or 15.25 meters is considered the maximum.

Scroll down on this linked page until you come to a chart labeled -

"Maximum Wire Lengths For TWO CONDUCTOR Copper Wire"

Speaker Wire

For a more technical description, see this link.

Speaker Cable Length Differences: Do They Matter? — Reviews and News from Audioholics

Also, keep in mind that what you should do is often very different from what you can do. You can run any length of wire you want. But the resistance of the wire start to become significant and signal is lost in the wire.

Some say that wire resistance should never be more than 5% of speaker resistance, so 5% of 8 ohms is 0.4 ohms, 5% of 6 ohms is 0.3 ohms.

It is next to impossible to find specification charts on Euro sized wire, but you can use AWG (American Wire Gauge) equivalents to estimate wire resistance.

Here is a chart with the general specs for standard AWG wire -

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

And here is a chart that will convert AWG to Euro mm² -

AWG conversion table

The nearest equivalents in AWG and mm² wire are

1.5mm² =
AWG 16 = 1.31mm² = 13.17248 ohms per kilometer
AWG 15 = 1.65mm² = 10.44352 ohms per kilometer

2.5mm² =
AWG 13 = 2.63mm² = 6.56984 ohms per kilometer

Also notice that the first chart gives Current capacities for the wire.

The "Maximum amps for power transmission" or the lower value number can be considered a sustained current capability. The "Maximum amps for chassis wiring" can be considered the absolute maximum fuse blow limit of current for that sized wire.

We can use these numbers to give us a very vague and general understanding of the power capability of the wire to a give speaker load.

I typically use 8 ohms as the standard speaker load. Using the 13ga or 2.63mm² wire as an example, we see a current of 7.4 amp sustained and 35 amps peak.

Power = Current^Squared X Resistance or P = I²R

Sustained Power of 2.5mm² equivalent wire to 8 ohms -
P = 7.4² x 8 = 438 watts

Peak Power of 2.5mm² equivalent wire to 8 ohms -
P = 35² x 8 = 9,800 watts

You can see that this standard wire leaves you plenty of reserve capability.

However, in long runs of wire, even though the current and power reserver are there, the resistance, capacitance, and inductance of the wire start to effect the signal quality.

Unfortunately, it is next to impossible to get specific inductance and capacitance specs on specific wire.

Steve/bluewizard
 
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PSM1

Distinguished Member
So for 2.5mm cable to get to the resistance of 0.3 ohms you need to have 45m or more length. However as Steve has pointed out there are other things to consider with longer lengths. However, I feel for your application you will be fine.
 

BlueWizard

Distinguished Member
His application will be fine...as long as...he is using adequate wire.

If you use 16ga (1.3mm²) wire or larger, you should have no problems at 11 meters (36 feet), assuming 6 ohm or higher speakers.

I suspect the Silver anniversary bi-wire cable would be up to the job. Though perhaps a little on the expensive side.

Can we assume you are using bi-wire cable so you can run the left and right channels in a single cable? You aren't actually bi-wiring the speakers? Not a problem if you are, but trying to clear this up.

What do you have for an amp, and what are your speakers?

The Silver Anniversary XT and XT Bi-wire are 1.88mm², which is a none standard size, but it is between 14ga and 15ga, so it is more than adequate for the job. And priced at roughly £7.70 per meter unterminated.

The standard QED Original Bi-wire cable is £5.20 per meter.

The 13ga (2.63mm²) Ixos XHS343 bi-wire cable is £3.08 per meter unterminated.

Speaker Cable - Audiovisual Online - High Quality Audio Video Cables and Accessories

Again, as long as you stay at or above 16ga or 1.3mm², you should be OK.

Steve/bluewizard
 
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Mark.Yudkin

Distinguished Member
So for 2.5mm cable to get to the resistance of 0.3 ohms you need to have 45m or more length.
Nope. Steve is quoting cross-sectional area rather than diameter that you've quoted (and is normal in speaker wire specifications). 2.5mm copper wire has a resistivity of 3.47 Ohms / km, so you could have nearly twice that length before having 0.3 Ohms.
 
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mattmarsden

Active Member
Hi guys, thanks for all the replies. Just to clarify I am bi amping each front speaker - B&W 800Ds and B&W HTM2D so I don't want to compromise quality, but equally at 11m x 3 of biwire cable I don't want silly money cables so I thought the silver anniversary XT would be a good compromise
 

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