Speaker wires shouldn't be longer than 60' ?

[stonehedge99]

Hi,

I have to drive 2 speakers on each side using a crown xls 802. For my current auditorium i need the sound guy sitting towards one side of the stage as theres no orchestra pit. So one set of 2 speakers wired in parallel on either the right or the left side of ths stage will have to be 83' away from the amp. So will a speaker wire run of 80' have a problem in that it will force me to drive the amp harder to pump out volume. The speaker wire used is OFC cable 18 guage.


Thanks

 

[dboomer]

It will probably work ... but it would work better with bigger wire. Having your speakers in parallel AND running a long distance work against you. I would suggest 12 ga wire for the lengths you plan on running.

 

[epimetheus]

I agree, 18 AWG is way too small. I would use 12 AWG or at least 14 AWG for a run that long.

 

[stonehedge99]

Hypothetically what are the max lengths you would go to with 18, 16 and 14 AWG wires ?

 

[museav]

Hypothetically what are the max lengths you would go to with 18, 16 and 14 AWG wires ?

It depends on the power being delivered and the impedance of the speaker, which relate to the associated voltage and current that along with the cable resistance actually determine the losses, along with the loss you consider acceptable for the application.

 

[Chris15]

Let us not forget that long runs of skimpy cable start to affect the frequency response of the system too...

 

[TJCornish]

While shorter and bigger gauge is always better, the reality is 80' is done fairly often. I would use 12ga wire and as long as this isn't for subwoofers where less than ideal damping factor makes a bigger difference, you'll be OK, at least for the power that an amp that small can deliver. 18ga is pretty small for any use whatsoever, and definitely too small for 80' on a 4 or 8 ohm system.

There are more complicated workarouds- transformers, series wiring, etc., but they're all a lot more work and cost than just running a big enough piece of wire.

 

[stonehedge99]

Ok ill write my 18 guage wire off and go buy new wire. I should have asked here before buying.

Now what guage shall i get ? The thickest possible ? Is that the way to go ? Tomorrow if i need to chop up that wire into smaller bits, the thick awg would still work well even for short runs right ?

Also on a side note what are the syptoms i might experience by using 18 awg on an 80' run ? The amp will sound less powerful ? I will lose volume and tend to drive my amp harder ?

 

[techieman33]

12AWG will be fine. Bigger is generally better but there is no reason to go for overkill. Yes the 12AWG will work for short runs.

 

[museav]

Also on a side note what are the syptoms i might experience by using 18 awg on an 80' run ? The amp will sound less powerful ? I will lose volume and tend to drive my amp harder ?

Well, hopefully you don't actually hear the amp, but the general issue is that some of the amp output will be 'lost' in the transmission down the cabling. Greater cable resistance and/or greater current due to a lower impedance load will increase those losses. A secondary issue is that since speakers are a complex load rather than a simple resistor and that their impedance varies with frequency, those losses can also vary with frequency.

 

[Lotos]

This thread made me randomly reminisce...

Had a Sennheiser Systems Engineer in our space awhile back, old French guy... Probably been installing audio rigs twice the time I've been alive.

We had recently had a new hire F.O.H. Sound join our crew, and he'd pointed out (and once pointed out, became apparent to everyone else...) a barely noticeable drop in volume on the SR Side of the rig compared to the SL... Easily compensated for, but there nonetheless if you were running "all things equal".

The Sennheiser guy (here for a completely unrelated issue with our Innovason desk and distant rack) noted this, and promptly asked where the amps were... They're located at grid height off SL on the second floor in a neighbouring room. He then wondered outloud if the cables run to the SR Speakers were of a different length than the ones to the SL side.

I was taken aback by this, I had never put much thought into it...

As it turns out, they were of identical length and it was an amp issue... But this was the first time I'd thought to consider the length of cable used provided it was under max spec.
Though one set of speakers is a good 40ft closer to the amps than the other, that just means the closer set has 40ft of coiled cable hung up in the grid. And that "lesson" is something I will never forget.

 

[Chris15]

The 50 metres (remember you have 2 wires @25m each) of 18AWG will have a resistance of 1.07 ohms.
With the 4 ohm load you are driving, this means that 20% of the power your amplifier produces is being lost as heat. Ouch.

With 12AWG this is only 6%.

 

[derekleffew]

This thread made me randomly reminisce...

Me too! I once worked in a venue that had monitor amps in a loft DSL, with speaker outputs on the US wall some 80-90' away. One problem: the wiring, in conduit and everything, was RG-59 coax! Allegedly/supposedly done by a professional. This was in the 1980s; today, I'm sure he'd use CAT5.

 

[chausman]

Me too! I once worked in a venue that had monitor amps in a loft DSL, with speaker outputs on the US wall some 80-90' away. One problem: the wiring, in conduit and everything, was RG-59 coax! Allegedly/supposedly done by a professional. This was in the 1980s; today, I'm sure he'd use CAT5.

Which is why I love the installation company our district uses.

 

[mbenonis]

The 50 metres (remember you have 2 wires @25m each) of 18AWG will have a resistance of 1.07 ohms.
With the 4 ohm load you are driving, this means that 20% of the power your amplifier produces is being lost as heat. Ouch.

With 12AWG this is only 6%.

Don't forget to take into account the skin effect, which will attenuate higher frequencies more than lower frequencies.

 

[TJCornish]

Don't forget to take into account the skin effect, which will attenuate higher frequencies more than lower frequencies.

I have yet to see any evidence that skin effect causes measurable detrimental effect on audio signals (outside audiophool "testimonials").

The Skin Effect Calculator (no endorsement implied - I found this via a Google search) lists 5Khz as the point where the skin depth is the whole conductor for a 12ga wire - in other words, no skin effect. North of 5Khz there is some skin effect, however the lion's share of the power of a typical audio signal is well below 5Khz - therefore making full use of the 12ga conductor where it most counts - and the impedance of high frequency drivers generally rises at high frequencies, reducing this effect more. Furthermore, unless there's a phase lag introuduced, this is a simple attenuation, which is solved equally simply when the system is tuned with EQ.

 

[museav]

Don't forget to take into account the skin effect, which will attenuate higher frequencies more than lower frequencies.

Much more a factor in RF but not really that relevant for audio frequencies. And if you want to consider skin effect then you probably also need to address the effects of capacitance and inductance forming a low pass filter that can also attenuate the higher frequencies over long runs.

 

[FMEng]

Furthermore, unless there's a phase lag introuduced, this is a simple attenuation, which is solved equally simply when the system is tuned with EQ.

Any time there is an alteration of frequency response, there is also a resulting change in phase. You cannot have one without the other.

 

[mbenonis]

Any time there is an alteration of frequency response, there is also a resulting change in phase. You cannot have one without the other.

...although you can play games to get the phase to do what you want (e.g., linear phase filters). Still changes the phase though.

 

[TJCornish]

We are arguing about the angle of the pin striping on a demo derby car. What's the lesser evil? 18ga wire so skin effect doesn't skew high frequencies but blows damping factor and wastes 20% of the amp's power?

12ga wire is the right choice here. If the user is sophisticated enough to be able to even measure the effects of cable capacitance and/or skin effect, they can surely correct it with the ample processing now available - FIR, etc.