OT: question on cables

[pete psingpy]

I'm finally setting up the keyboards again now that the new "studio" is ready.

 

I have a bag full of 1/4" patch cables. However, I know I was careful to buy "speaker" cables to connect from the output of my mackie 1202 mixer to the inputs on each of the Event monitors. The "speaker" cables looked just like the instrument patch cables.

 

My questions are: does it matter if I use an "instrument" cable to connect the mixer to the speakers? If so, is there a way I can tell an instrument cable from a speaker cable? Can I distinguish them by the wiring in the connectors?

thanks

[bleen]

If the Event monitors are active (powered), you shouldn't be using speaker cable between the Mackie and the Events. You need a good shielded, preferrably balanced, cable for that patch.

 

Speaker cable is two conductor, unshielded and ONLY for runs between a power amp and a passive speaker cabinet. Everything else should be shielded at all times to prevent interference.

[Dave Horne]

If you were to use unshielded cables (speaker cables) from your mixer to your amp (powered speakers), you'd get a lot of hum. There wouldn't be any harm done, you just couldn't live with the hum.

 

I really prefer to make my own cables. You get the exact length you're looking for and there's a bit of satisfaction knowing you did the job yourself.

 

You can use instrument cables (Shielded cables) from your mixer to your amp or powered speakers.

 

If you were to use shielded cables (either mic or instrument cables) from your _amp_ to your speakers, that would not be recommended. I assume from what you wrote you use a Mackier mixer and powered speakers. correct?

[pete psingpy]

Thanks for the fast replies. Let me clarify my situation:

 

I have a Mackie 1202VLZ pro mixer, and I need to run cables from the mixer outputs to the inputs on my powered Event PS8 monitors. The longest run will require about 25 ft of cable length.

 

Do I understand correctly that the only difference between "speaker" and "instrument" cable is that the instrument cable is shielded? i.e. these cables have the same wiring.

 

If that were true, wouldn't I always want to use instrument cable?

 

I think the guy at the music shop was saying the opposite of what you guys are: I believe he said I should use "speaker" cable to connect an un-powered mixer to powered monitors.

THanks

[Dave Horne]

Pete, if you are using a _powered_ monitor you will be sending that powered monitor a very weak signal from your mixer and that cable needs to be shielded ... an instrument cable would work and an XLR cable/mic cable would even be better (probably less hum). For such a long run, I would use XLR cable, but an instrument cable would also work.

 

A typical instrument cable has one wire with shielding. That shielding is the second 'wire' or connection in the plug.

 

An XLR (mic cable or a stereo cable) has two wires and they are both covered by shielding which is the 'third connection' in the plug. If you were to A/B both the instrument cable and the 'mic', the 'mic' cable might have slightly less hum, but it might not really make very much difference at all. If you are planning to do serious recording, I'd buy a 'mic' cable and be done with it.

 

I am not an electrical engineer, so my choice of words or my description might not be as refined as others, but I believe what I am writing to be basically accurate.

 

The guy in the store might think you are running a cable from your _amp_ to your speaker. In that case, simple lamp cord would be OK as long as the guage was heavy enought for the lenght of the run and the output of your amp.

[Reverend Rhythm]

Just to add to what Dave said: Instrument cable will work fine. Dies the 1202 have balanced outputs (they can be 1/4 inch plugs or XLR plugs)? Do the events have balanced inputs? If so you can run a balanced line (usually its XLR - mic cable).

[MurMan]

Hold on. I'm sure everyone is trying to help, but first things first.

 

The first step in selecting a cable is to understand the output and input characteristics of the two devices you're connecting. Googling for your mixer and monitors, I found their spec sheets. The main outputs on the mixer and the monitor inputs are available in both XLR and 1/4 inch TRS connectors. These are balanced (two wires plus a shield) connections and are electrically equivalent.

 

I would recommend using XLR cables because they are widely available in various lengths. Buy name brand cables, but there's no need to overspend. TRS is fine, but because it's possible to plug in an instrument cable (unbalanced, will not work for this application), I don't like them for balanced connections.

 

Good luck.

[pete psingpy]

I need to use the 1/4" outputs on the mixer since they are a separate set of outputs.

 

I could use the XLR or 1/4" inputs on the Event monitors.

 

So it sounds like the best thing to do would be to use a cable with 1/4" on one end and XLR on the other. But this also should be a "balanced" cable? The presence of at least one XLR cable will ensure balanced?

 

Does a "shield" mean a third wire? I opened the connectors on my cables and it looks like they all have 2 wires.

 

Sorry I'm dragging this out. I'm still confused between what "balancing" vs "shielding" implies.

 

Is this right:

 

1. "speaker" cable: one wire, not shielded

 

2. "instrument" cable: 2 wires, shielded because of 2nd wire

 

3. "balanced" cable: both shielded and balanced because of 3 wires. XLR connector cable is always balanced, but 1/4" cables may or may not be balanced.

[MurMan]

Originally posted by pete psingpy:

I need to use the 1/4" outputs on the mixer since they are a separate set of outputs.

 

I could use the XLR or 1/4" inputs on the Event monitors.

 

So it sounds like the best thing to do would be to use a cable with 1/4" on one end and XLR on the other. But this also should be a "balanced" cable? The presence of at least one XLR cable will ensure balanced?

It's better to use industry standard cables rather than build an adapter cable. Get a balanced TRS 1/4 inch cable. These plugs have a small ring next to the tip.

 

Does a "shield" mean a third wire? I opened the connectors on my cables and it looks like they all have 2 wires.

A shield is a conductor that encloses the other wires. Flexible cables use a braided mesh of small wires. A balanced cable will have two wires that are wrapped by the shield. Electrically, this is three wires.

 

Sorry I'm dragging this out. I'm still confused between what "balancing" vs "shielding" implies.

 

Is this right:

 

1. "speaker" cable: one wire, not shielded

 

2. "instrument" cable: 2 wires, shielded because of 2nd wire

 

3. "balanced" cable: both shielded and balanced because of 3 wires. XLR connector cable is always balanced, but 1/4" cables may or may not be balanced.

No problem, it's always better to ask.

Speaker cables have two wires. Usually not shielded, but they can be shielded to prevent the high currents in speaker cables from affecting other cables.

 

Your description of unbalanced instrument and balanced cables is correct. If a 1/4 inch cable has a tip and ring, it's unbalanced. If it has a small third ring, it's balanced and is called a TRS (Tip Ring Shield) cable.

 

Hope this helps.

Murray

[MurMan]

Pete,

 

One more thing. Balanced connections and shielded connections are two techniques that let us move low-level signals around without picking up noise.

 

For example, balanced, shielded cables can transmit low level mic signals hundreds of feet to a mixer. Pro gear will use balanced shielded cables even for short distances because it's the best way to avoid noise problems.

 

Unbalanced, shielded cables (instrument cables) work well for low level signals over a short distances. Like guitars, keyboards, and consumer audio/video systems.

 

Unbalanced, unshielded cables work well for high level signals, such as speakers and AC power. As the distance and/or power increases, the cables need to get heavier. (more copper).

 

These are simple explanations of cables, but it's about all you need to know for most situations. There's a wealth of information available about cables on the net, some of which is correct!

[Dave Horne]

Pete, I also own the Mackie 1202 and there are _two_ sets of main outs - 1/4" (TRS) and XLR.

 

There are also an additional two sets of outs (for a grand total of four outs!).

 

There is a Control Room out and an 'Alt' out.

 

I think it would be easier (as was previously mentioned) to simply use the XLR outs for your powered speakers since they accept XLR input and use one of the other sets for your other need. The output panel on the front of the mixer gives you _many_ options. Hell, I think you can even use the RCA tape outs as well.

[pete psingpy]

Originally posted by Dave Horne:

Pete, I also own the Mackie 1202 and there are _two_ sets of main outs - 1/4" (TRS) and XLR.

 

There are also an additional two sets of outs (for a grand total of four outs!).

 

There is a Control Room out and an 'Alt' out.

 

I think it would be easier (as was previously mentioned) to simply use the XLR outs for your powered speakers since they accept XLR input and use one of the other sets for your other need. The output panel on the front of the mixer gives you _many_ options. Hell, I think you can even use the RCA tape outs as well.

Dave,

I use the alt 3/4 outs to run into my soundcard for recording. I use the control room outputs to run to my monitors. If I remember right, I used the control room outs to monitors because there is more flexibility in terms of managing what signals are sent to the mixer control room outputs (e.g. tape, alt output, etc). I could be wrong, since I haven't used the mixer in awhile.

[dementia13]

I'm not sure that this was explicitly answered, but: you can buy a cable with XLR on one end and balanced TRS on the other. But-- the presence of the XLR doesn't necessarily guarantee that the 1/4" end will be balanced. Make sure by looking at the connector. On a typical instrument cable, you will have a ring between the tip and the side of the connector. This ring separates the two contacts: the signal feeds out through the tip, and the shielding connects to the side of the plug. A balanced cable will have an extra ring, giving you three contacts. Your local salesman will be glad to sell you the correct cable, as it will cost just a little more than the wrong one.

[Byrdman]

Originally posted by pete psingpy:

Thanks for the fast replies. Let me clarify my situation:

 

I have a Mackie 1202VLZ pro mixer, and I need to run cables from the mixer outputs to the inputs on my powered Event PS8 monitors. The longest run will require about 25 ft of cable length.

 

Do I understand correctly that the only difference between "speaker" and "instrument" cable is that the instrument cable is shielded? i.e. these cables have the same wiring.

 

If that were true, wouldn't I always want to use instrument cable?

 

I think the guy at the music shop was saying the opposite of what you guys are: I believe he said I should use "speaker" cable to connect an un-powered mixer to powered monitors.

THanks

Not sure if this has been made clear.

 

Speaker cables carry substantial power. Because the resistances are low and the currents high shielding is not required (or desirable in fact - it would increase the losses in the cables)

 

Signal cables do not carry significant power. They are sjielded because otherwise stray electromagnetic fields can cause signals in the cables.

 

If you use speaker cables when a signal cable is needed, you may (probably will) get hum.

 

If you use a signal cable when a speaker cable is needed, you may melt the cable or the connectors at the point the wires connect to them. 100W at 4 Ohms is 5 Amps, which a signal cable is not designed to handle.

 

If you are using powered monitors, you use signal cables to get the signal to them, not speaker cables.

 

To tell the difference, speaker cables that look similar to signal cables will generally have a gauge number printed on the side of the cable. Typically you will find some number like "16 AWG". This is (very roughly) an indicator of how much power you will lose in the cable - higher numbers mean more loss. (No - its not watts)

 

Hope that covers everything.

[pete psingpy]

Thanks! I learned a lot here. I know what I need now.

 

Another quick question though....

 

I found a cable in my collection labelled "speaker" on the side. It has 1/4" on both ends, just one ring on the end meaning unbalanced. BUT, this cable has 2 wires (I unscrewed the connector) and appears to be wired the same as my other "intrument" cables which also have 2 wires. Does this mean that this "speaker" cable is a shielded cable?

[MurMan]

Originally posted by pete psingpy:

Does this mean that this "speaker" cable is a shielded cable?

The "speaker" label means that it's probably unshielded. Usually you can open the plug and follow the wire connected to the ring (this is the shielded wire) into the cable. If you can see it going into the cable jacket just like the other wire, it's not shielded. Often there's heat-shrink tubing over the jacket to make the wiring more durable, so you can't see the shield.

 

Twist off the barrel on a few 1/4 inch cables and you'll learn to recognize the difference between shielded and unshielded As Byrdman pointed out, speaker cables carry appreciable current, so the wires will be thicker than signal cables.

[pete psingpy]

I found a cable labelled "instrument" and one labelled "speaker" (I mentioned earlier) in the collection.

 

Both cables have two contacts on the inside of the connector: one is in the middle and one goes along the edge. Both appear to have two wires but I didn't want to ruin the cables by ripping apart the casing too much. My observations are:

 

1. The "speaker" cable has a white sheathed wire connecting to the middle of the connector, and a black sheathed wire connecting to the edge of the connector.

 

2. The "instrument" cable has a black sheathed wire connecting to the middle of the connector, and what appears as a bare wire connecting into the side along the connector.

 

I have this huge pile of 1/4" connector cables. I know now that none are balanced, but it would nice if I could figure out which ones are shielded.

[MurMan]

Pete,

 

What you've described is exactly what you should expect.

 

The speaker cable with the black and white wires is unshielded. Black and white are the most common colors for a cable with a single pair of wires.

 

The other cable is shielded. There is a technique of pulling the wires being shielded through an opening in the braided shielding. The braid is then pulled, collapsing the shield. What's left looks like a bare wire. (If you look carefully, you can see that it's woven.) This wire is soldered to the ring conductor, the one on the outside.

[pete psingpy]

Originally posted by Byrdman:

Originally posted by pete psingpy:

Thanks for the fast replies. Let me clarify my situation:

 

I have a Mackie 1202VLZ pro mixer, and I need to run cables from the mixer outputs to the inputs on my powered Event PS8 monitors. The longest run will require about 25 ft of cable length.

 

Do I understand correctly that the only difference between "speaker" and "instrument" cable is that the instrument cable is shielded? i.e. these cables have the same wiring.

 

If that were true, wouldn't I always want to use instrument cable?

 

I think the guy at the music shop was saying the opposite of what you guys are: I believe he said I should use "speaker" cable to connect an un-powered mixer to powered monitors.

THanks

To tell the difference, speaker cables that look similar to signal cables will generally have a gauge number printed on the side of the cable. Typically you will find some number like "16 AWG". This is (very roughly) an indicator of how much power you will lose in the cable - higher numbers mean more loss. (No - its not watts)

 

Hope that covers everything.

I have some unidentified cables in the pile that are labeled "C.B.I. Artist 20 AWG". Does that offer any clues to what it is? The high number, if it refers to a gauge I think like you implied; I'd guess this is a signal cable.

 

The "speaker" cable that I keep referring to is labeled "16 / 2 speaker". If the 16 is referring to a gauge, this would make sense that the speaker cable has heavier wire.

[MurMan]

Originally posted by pete psingpy:

I have some unidentified cables in the pile that are labeled "C.B.I. Artist 20 AWG". Does that offer any clues to what it is? The high number, if it refers to a gauge I think like you implied; I'd guess this is a signal cable.

 

The "speaker" cable that I keep referring to is labeled "16 / 2 speaker". If the 16 is referring to a gauge, this would make sense that the speaker cable has heavier wire.

CBI is the manufacturer and Artist is one of their cable product lines. 20 AWG (American Wire Guage) is an appropriate guage for signal cable.

 

16 / 2 means the cable has a pair of unshielded 16 AWG. The guage required for speakers (or any other use that carries appreciable current) depends on the current and the length of the cable. I could explain it, but there's some math and basic electrical theory involved and we'd get even further off-topic. (obtw, there's a lot of speaker cable folklore, imho based on ignorance of Ohms Law.)

[pete psingpy]

Originally posted by MurMan:

Originally posted by pete psingpy:

I have some unidentified cables in the pile that are labeled "C.B.I. Artist 20 AWG". Does that offer any clues to what it is? The high number, if it refers to a gauge I think like you implied; I'd guess this is a signal cable.

 

The "speaker" cable that I keep referring to is labeled "16 / 2 speaker". If the 16 is referring to a gauge, this would make sense that the speaker cable has heavier wire.

CBI The guage required for speakers (or any other use that carries appreciable current) depends on the current and the length of the cable. I could explain it, but there's some math and basic electrical theory involved and we'd get even further off-topic. (obtw, there's a lot of speaker cable folklore, imho based on ignorance of Ohms Law.)

I'm still interested in hearing more (I may be the only one but this has been quite informative for me). V=IR, P=VI if I remember right. A thinner, longer wire will have more resistance and therefore generate more heat. It's interesting since the music store salesman had it completely backwards: He insisted I needed speaker cables to connect my mixer to my powered monitors.

 

Anyway, I went back to the store today and bought balanced 1/4" TRS signal cable. That's what I asked for. The packages are labelled "stereo cable". I hope I bought the right thing. They have 2 rings near the end of the connectors. Why called stereo though? I opened the connectors and verified that there have 3 wires.

[Keyrick]

A couple of clairifications.

 

A TRS "phone plug has 3 terminals. The Tip, which is on the end of the plug, the Ring, which is just below the Tip, and the Sleeve, which is below the the Ring.

 

Typically on a balanced cable with a TRS on one end and an XLR on the other, connections are as follows:

 

Phone Tip = XLR Pin 2 = Hot

Phone Ring = XLR Pin 3 = Cold

Phone Sleeve = XLR Pin 1 = Shield

 

A TRS plug can also be used as an Unbalanced Stereo conector where:

 

Phone Tip = Left Hot

Phone Ring = Right Hot

Phone Sleeve = Shield Common

 

This arrangement is also used on Stereo Headphones. The same convention applies to 1/8" "Mini-Plugs".

 

An instrument cable used for a guitar is unbalanced, shielded, and uses a Tip-Sleeve (no Ring) connector on each end. The Tip is hot and is wired to the other TIP. The Sleeve is the Shield Common and is wired to the other Sleeve.

 

Many speaker cabinet manufacturers use Tip-Sleeve connectors as well. The cables can be balanced or unbalanced (depending on whether or not the manufacturer grounds the sleeve on the amp chassis), unshielded, and should be wired Tip to Tip and Sleeve to Sleeve. As mentioned earlier, Speaker cables use a larger gauge of wire as they are required to carry much more current than an instrument or microphone cable.

 

I hope this helps.

 

Rick

[MurMan]

Originally posted by pete psingpy:

I'm still interested in hearing more (I may be the only one but this has been quite informative for me). V=IR, P=VI if I remember right. A thinner, longer wire will have more resistance and therefore generate more heat. It's interesting since the music store salesman had it completely backwards: He insisted I needed speaker cables to connect my mixer to my powered monitors.

Here's a little more speaker wire info. In ac circuits, we use impedance (Z) rather than resistance ®. Ohms law still applies, but you've got to use complex math instead of algebra. (Complex doesn't imply difficult. Well, actually, it is complex. It's math using numbers with real/imaginary parts. Oops, now I've to explain that imaginary doesn't mean that it doesn't exist. Sorry, this is like pulling a thread on a sweater ...)

 

If the speaker were connected directly to the amp, the ability to transfer energy from the amp to the speaker is maximized when the impedance of the speaker exactly matches that of the amp. (In this case, delivering 100W to a speaker requires that the output stage of the amp dissipate 100W too.) Not all amps operate like this.

 

There's also the issue of dampening, the ability of the amp to overcome the back voltage generated by the moving speaker coil. Maximum dampening occurs when the impedance of the amp is low compared to the speaker. This is one of many tradeoffs that amp designers face.

 

Speaker wire screws up the impedance match. The ideal speaker wire would have an impedance of zero. In reality, if it's impedance is negligible compared to the impedance of the amp/speaker, it has little effect on the impedance match.

 

There is great debate about what is negligible. What makes it fun is that no matter how close to zero impedance speaker wire gets, there's always someone that claims to hear a difference with an even bigger, more monster, wire.

 

Impedance includes the effects of resistance, inductance, and capacitance. At audio frequencies, the impedance of a speaker cable is nearly equal to the resistance. Very long cables with thin insulation can have some capacitance. Inductance for straight wires is negligible. Again, what's neglible is subject to debate. As long as it's non-zero, someone will be argue that he can hear it.

 

In the complete signal chain from mic/instrument to speaker, there are many transfers that involve impedance matches. Good thing that cable manufactures don't get involved.

 

You've also got the crowd advocating the special (expensive) audiophile ac power cords. If this made an appreciable difference, why aren't there more recording studios adjacent to nuclear power plants?

 

But I digress. Anyway, this should be more than enough theory to get you thoroughly confused. If you're still interested, go find some books on audio electronics that are at your level.

 

Also, some of the other MusicPlayer forums have more coverage of this topic.

 

Good luck,

Murray