What to use for speaker wire speaker cables from PA or amp

[JFrankParnell]

If there was a thread about speaker cables, I caint find it now.

Specifically, today, I need to know about hooking a Peavey xr400b mixer/amp up to some speakers. Just a little vocal PA, nuthin special. Probly want 20-30 ft cables, just for convenience.

But I think the same thing applies to guitar head->speakers.

Just get some nice thick speaker/lamp cord down at the hardware store and put some 1/4inch plugs on either end?

[JohnH]

I just use the thickest 2-core cable that fits into a jack plug. Nothing special.

[lunaalta]

From my experience, a good, thick core, multi-strand, mains chord works well. If it's 3 core, just use 2, snip the earth back, well out of the way, so it doesn't do any harm.

I often used to re-wire loudspeakers with good cable, when I sold high quality/power hi-fi systems, in London. Clients spent money to have decent speaker cables and inside their loudspeakers, the speaker units were wired with crappy bell wire.

[JFrankParnell]

I found this: www.fender.com/news/why-instrument-cables-and-speaker-cables-arent-interchangeable/
It seems there is no shield around the speaker cable. Therefore a 'core' type cable is not indicated? It seems the difference between a purchased 'speaker cable' and one I make from zip wire: or 'lamp wire' or whatever is just the outer jacket of rubbery protection, correct? Thicker is usually equated with better in this context; is that true or feldergarb?

[ashcatlt]

I just go to the hardware store and grab a decent but cheap orange extension cord or two, snip off the ends, and add 1/4" on either end. You might even have this in your basement/garage/pile of crap. Most of the time you can use the brown extension cords, too.

[lunaalta]

Sorry, I didn't explain that very well, did I........... (well, I understood it...LOL)?  

By core, I mean the wire threads inside the pvc covering. You don't want to be using a shielded cable for your speakers.
At home, for example, I use a cable with 79 strands (actually, it's Absolute sound cable, expensive, but I got it free. It is spaced, 79 strand cable). So, a power cable with many strands inside, will work better, in theory (which I forget now, many years later) than bell wire, with half a dozen strands.

I read, years ago, of a test, done in an anechoic chamber, running speaker cables through with a strong signal. 'Apparently', you could hear the smaller cable's signal! Which equated with a loss of energy, while the 'fatter' cable was silent. The test wasn't associated with any brand of wire. 

The Fender article is right on the button, by the way!

With more strands in your speaker cable, you are less likely to be heating up the wire and losing signal, than with a thinner cable.

While on the subject, yes, there is a lot of feldergarb surrounding speaker cables. It has made several companies a lot of money.......
I tried many of the high profile 'monsters' out there, as part of my job, and found no improvements in sound with any, other than the simple, multi-strand, cables. Monster Cable had just entered the UK hi-fi market, in the early 80s, I wasn't impressed with the results. Also, I was told that the 'interwoven' types, which were heavily advertised, were detrimental to the signal, and could damage your amp! Something to do with capacitance, but I ain't much of a tech, so I can't expand on that.... 

Anyway, I'm sure some others are better versed than I am to talk tech on this subject. This is just my take on it.........
Good luck!
Ted

Yup! Ashcatlt, should work fine!

[sumgai]

JFP,

Well, as with anything else, it depends.

If you're going for rugged, outdoors-capable, long-lasting, then you want a 16-gauge extension cord from Home Depot or somesuch. Cut off the ends and mount some plugs, and you're good to go. That's good for your 30 foot run, and probably OK up to about 50 feet. If it were more than 200 watts (per channel), then I'd step up to 14 gauge, again up to about 50 feet.

If it's meant for indoor use only, and won't be constantly wiggled about (pack/unpack, setup/teardown, etc.) then 18 gauge lamp zip cord is sufficient for up to 100 watts, even at 30 to 50 feet. More wattage than that, you'll need 16 gauge zip cord.

Essentially, I recommended a larger gauge than strictly necessary for outdoor use simply because it's more likely to withstand rough treatment than zip cord. But in an emergency, I understand if one has to "make do" with what one has on hand. Just don't get dependent on lower quality stuff in situations that demand high quality materials, that's all I'm saying here.


In Engineering terms, it all boils down to what we call "ampacity". If you're interested, search on the web for that term, but be prepared for some eye-glazing math....

HTH





sumgai

[ashcatlt]

I've honestly never really worried about gauge. I've run big PAs through 100 ft "heavy duty" extensions a whole lot of times, without ever a question. Of course, I'm a hack. Leads to a question, though. These things are always labelled with a maximum wattage rating. I use that to tell me whether I can run my space heater off of it or not. Is there some reason we can't just make sure that's big enough to handle our needs? I suppose that they are spec'd at 60Hz, and maybe they dissipate more heat when carrying higher or lower frequencies? Is there any good way to correlate that rating to our uses here?

[sumgai]

ash,

Looking at it from your direction, a wattage rating is more than good enough. However, in my neck of the woods, everybody sells extension cords acording to the permissible amperage capacity. But that's just as good, because Ohm's Law works in our favor here.

If a cord is rated for 13 amps (medium duty on most packaging), and we want to know if it'll handle the power draw of some device, then we need to know either the voltage in question, or the resistance of the device.


If we know the voltage, we use: P = V * I

If we know the resistance, we use: P = I² * R


For standard (USA) house current, we'll use 120 volts. Rewriting the first formula above, we get:


I = P / V


Plugging in our known values, we get:

1,500 watts divided by 120 volts, which yields 12.5 amps.

A 13 amp cord will handle the wattage fine, under most conditions. To be certain, I might consider using a larger cord, or a smaller heater, but only because we're pushing the cord pretty hard up against it's rated limits. For me, the deciding factor would be 'how warm is the cord to the touch?'. If it's merely warm, than all is probably good. If it's almighty warm, or even hot, then I'd be looking for another, larger cord.


But you wanna use a heater, and JFrank wants to power a speaker, so....

When it comes to speakers and such, we need to use the second formula shown above. For a speaker cab, we know the impedance (equivalent to the R in the formula) and we know the amp's output wattage. But again, we need to rewrite the formula to determine how many amps are being drawn:


I = sqrt (P / R)


That's cumbersome, but we know the numbers. Conversely, if we have a multimeter in our toolkit, then we can measure the voltage being delivered to the speaker terminals, and use this formula:


P = V² / R


But let's keep it simple for now, because it's faster and easier to whip out Calc on the 'puter than to drop everything and dig out the multimeter.

For a speaker cab of 4Ω and an amp's rated power output of 100 watts, we see:


100 / 4, which equals 25, and is then reduced to its square root, or 5.... as in 5 amps.


From this it can be seen that a simple 9 or 10 amp extension cord will do the job. But I caution the reader that low-amperage wire like this is physically fragile, and may not be suitable for the anticipated environmental conditions. Of course, YMMV.


HTH





sumgai

[reTrEaD]

Feb 27, 2014 22:56:45 GMT -5 JFrankParnell said:

Probly want 20-30 ft cables, just for convenience.

That's some fairly serious length. Longer = more resistance. In a speaker application, we'll be concerned with the added resistance affecting the damping factor long before we have any issues with how much current the wire can safely handle.

You could do all the calculations by hand, referring to AWG charts for the resistance (multiply times two because you have one thirty foot length out and one coming back), and the impedance of the speakers. Or just use a calculator program like the one at the bottom of this page:

www.bcae1.com/dampfact.htm#demo

For 8 ohm speakers, 14 gauge is just barely what I would consider acceptable for a thirty foot length. YMMV. No issues with safety or cable failure. And we have 96% of the power reaching the speaker so you won't even notice the drop in volume. But the bass won't be quite as 'tight' and 'punchy' as it would with a larger gauge cable. Unfortunately, 12 gauge and larger cables tend to be somewhat unmanageable. Bulky and stiff.

[sumgai]

'TrEaD,

Ordinarily I'd fully agree with you, and with the figures on your linked page. But before I get into my disclaimer, I want to point out that BCAE does a credible job of calculating the damping factor and how it's affected by wire running to the speaker. I had to double-check for myself, and he does do it correctly throughout the calculator, all figures are rounded up or down very closely. I do quibble with how he arrived at some of those numbers, seemingly without explanation that a layman can understand, but that's a horse of a different color. However, in his paragraph Speaker Wire and Damping Factor, he misquotes the resistance of 5 feet of 14 ga. wire - it's not "0.016Ω", it's actually 0.0126Ω. (And it should be doubled, for 5 feet of wire running to the speaker - and back (which his calculator does do correctly).) The rest of that particular paragraph, which depends on that misquote, is also obviously miscalculated.

But I think the rest of the page is pretty much correct, that was the only glaring error I found.


Now, as to the damping factor in a guitar or PA amp. Keep in mind that BCAE's whole site is aimed at the audiophile (mobile, to be sure, but nonetheless....), presumably someone who is after the N^th of perfect sound reproduction. While we guitarists and vocalists claim to want the same thing, we don't, not really. In fact, the first glaring discrepancy is that the frequency range of our instruments/vocal cords is not nearly so large as that of a "whole spectrum" sound reproduction system. For starters, a guitar is missing the lower two octaves, 20-40Hz and 40-80Hz - the low E string being ~82Hz. If we look at the impedance curve of an average 12" guitar speaker, we see that the valley (a speaker's impedance is measured at the first low point (valley) after the first hump) is well below 80Hz, in free air. Hence, worring about full range fidelity is not gonna be much of an issue here, as the speakers are already a limiting factor, just as is the guitar itself.

Next, the average range of a vocalist is 300-3000Hz, excepting those who are designated as Bass singers, they can get down into the range of a guitar, 80 to 100Hz or so. As with the guitar, this also does not need the demanding specifications of a full frequency range system, nor the control over an amplifier's damping factor as would an audiophile's system.

Obviously when speaking of a Bass guitar and its range, we are approaching the need to consider the damping factor. But JFP specifically did not mention being able to handle a bass too, so I left out that whole part of the discussion. In the short run, the damping factor is not a big consideration in the nominal guitar/vocalist field. Bass players, yes, somewhat, but not for the rest of us.

And that was my disclaimer.


Now, one other consideration for everyone reading this. As it happens, all that wattage is used approximately 1 to 2 percent of the total time you are playing (or of the time you are listening to a recording). When you hit a note, the initial attack does need a considerable amount of power in order to not distort it in any way. But as the note starts decaying, the amount of power necessary to keep the note audible (the sustain portion of that note) is much lower than that of the attack - at least an order of magnitude, and often even less.

Remember too, that when you are reading an amp's spec, specifically the output wattage, that refers to the maximum capability, not the level at which you would ordinarily listen to music. What this means is that if you crank it up to the max, the initial attack of the pick hitting the strings may require close to, or even more than, your full wattage available. (When more is required, that would've been in order to prevent distortioin. Since more power wasn't available, the amp distorted the signal.) But as soon as the pick portion of the attack was over, and as the note started sustaining, the power needed to carry that note dropped to about 10%, perhaps even less, of the full output.

Then too, at average listening levels, the total amount of power needed is greatly reduced. Figure about 10 to 20% of the amp's maximum output for the attack levels, and an order of magnitude less for the sustain portions.... or about 1 to 2% of the amp's total power capability.

So why is all that power available, if we're not gonna use it except when we play the Arena or the Colosseum? Simple - to prevent distortion whenever possible. There's a reason why Fender Super Reverb and Twin Reverb amps are called the world's cleanest-sounding amps - they don't distort until right at the very upper limit of their capability. Other amps deserve just as high a reputation, perhaps many others, but Marketing has played a big part in this mindset/gestalt. Even so, we strive for the lowest distortion possible, just so we can hook up a ProCo RAT, and make a total mockery of our quest.

But at the bottom line here, when we play at less than ear-bleeding volume levels, the damping factor becomes almost a non-starter. Yes, it's still there, but at such a low level as to be ignorable for our needs.

HTH




sumgai

[reTrEaD]

I'll go along with all that, Sumgai. But the minute someone put a mic in front of a kick drum to add a little sumthin-sumthin the target changes. Or if they decide to pipe some canned music through the PA during band breaks. Keeping the bass tight and controlled isn't just a high-volume issue.

Of all the replies on this thread, these two are my favorites:

Feb 27, 2014 23:58:00 GMT -5 JohnH said:

I just use the thickest 2-core cable that fits into a jack plug. Nothing special.

Feb 28, 2014 13:45:21 GMT -5 ashcatlt said:

I just go to the hardware store and grab a decent but cheap orange extension cord or two, snip off the ends, and add 1/4" on either end. You might even have this in your basement/garage/pile of crap. Most of the time you can use the brown extension cords, too.

Old orange extension cords, especially those which have been carelessly used with hedge trimmers, are great fodder for speaker cables. But be aware that the gauge varies. I've seen a few rare cases where the wire was 18 gauge. Not something you would want to use for a thirty foot run. But I wouldn't hesitate to use it for a 4 foot cable.

[sumgai]

reTrEaD,

Point taken about the kick-drum being mic'ed, I hadn't thought through that far... I stopped at vocals, sorry to say.

But I think we're all agreed, a somewhat standard orange extension cord of 14 gauge will be sufficient. And now that I think about it.... I don't recall seeing any such beast made with too thin of a wire diameter for the length. IOW, if it's 50 feet and made for outdoor use (hedgetrimmers come to my mind, too), then it's more than likely 12 gauge, and that'll be more than sufficient, wattage-wise. As for the quality of the tone in the two lowest octaves, there may remain some "room for improvement" - subjective to the listener's perceptions, of course.





sumgai

[JFrankParnell]

You know, youre right, I did start off with 'vocals only' But, of course, as Retread says, it wont be long before I'm hooking up a kick mic and Oh bass player blew his amp, we need to try to run him through that. So, please, lets figure on a full range of instuments and whathave you, running thru this cheap little pa (I just got it for $75). Stadium gigs...Haha, no, just loud practices, parties, etc.

The reason I spec'd the long cables is because I am abso mental about setting up wires out of the damn way of everything and who knows what corner of the room a speaker might be, in relation to this mixer/amp. I like to run wires around the backside of stuff.

I wasnt sure what all to plug into that damping calculator, Retread.

[JohnH]

I had a look at the specs, and it seems like a handy piece of kit. But its only 100w into 4ohm, so I doubt that it's a place where bass and kick-drum signals should be.

[sumgai]

John,

One thing that most muscians have discovered over the years is that Peavey tends to understate their specs, not inflate them. That, and their solid reliability, not to mention their "bang for the buck" pricing is why they're still around.

Yes they've had a few misfires over the years, but by and large, they deliver more than they promise. Likely the only reason they're not bigger than Fender is they refuse to hire a Marketing wunderkind, and instead treat everyone 'just like folks'. Not a bad gig, if you can get it.

I wouldn't hesitate to at least try running whatever through that amp, even if looks on paper like it might not be a good idea. The worst that can happen is a busted output stage, and that's easy to fix. (Though more likely it'd be a fuse that went kerblooey.) But less than the worst happening, it'd just sound bad, and the user would quit abusing it.


HTH








sumgai

[JohnH]

My thought was more around making best use of the available headroom, given that most bass rigs have more power themselves than this pa, and most drummers wear heavy boots.

[newey]

and most drummers wear heavy boots.

. . .Nah, too easy!

[reTrEaD]

Mar 3, 2014 15:59:16 GMT -5 JohnH said:

My thought was more around making best use of the available headroom, given that most bass rigs have more power themselves than this pa, and most drummers wear heavy boots.

I agree you won't be able to do more than just bleed a little bit of the kick into the mix. But sometimes a little something can make a big difference.

Mar 3, 2014 1:04:47 GMT -5 JFrankParnell said:

I wasnt sure what all to plug into that damping calculator, Retread.

If you can't find a spec on the damping factor of the amp, just figure around 150 or so. The rest is self-explanatory. The impedance of the speaker at the end of the cable, length of cable, gauge of wire...