The question here is not whether you CAN interchange instrument and speaker cables, but whether you should interchange them. The short answer for those comfortable with TL:DR modality, is NO.

But why not? We’ve all been in a crunch scrambling to get set up and all those ¼ to ¼ cables look alike. Sure different coloured casings, plated connectors, gold coloured connectors, braided fabric outer covers, yada yada yada.

So what’s the difference?

I was recently doing a project and needed two XLR cables and one speaker cabinet cable. I could get a 25’ microphone cable from a brand name provider for $20, but a 5 foot speaker cable with tip and shield ¼ connectors was $29. What the heck?

Hence, time for some scientific research, which means going to electronics documents and not to look at marketing or advertising stuff. Cynical? Moi? Absolutely.

Instrument Cable Construction

Instrument cables are what we refer to as unbalanced shielded cable. There is a single conductor which is connected to the tip portion of the ¼ connector. Wrapped around the single conductor is a shield, typically made from fine braided copper wire. Sometimes the shield is just foil. The single conductor is a very narrow gauge of twisted fine wires or a solid wire. Solid wires move more signal but are susceptible to breakage when kinked. Twisted wires are most common. The shield is soldered to the chassis of the connector. The shield is what cuts down on noise and interference. If you get a lot of hum or noise with an instrument cable, the shield is likely poor or compromised. The larger the gauge number, the finer the conductor. As instruments move very low power signals, they don’t need large gauge wires, so most instrument cables use 24 AWG gauge conductors.

Speaker Cable Construction

Speaker cables use the same connectors on the ends and this is what makes them hard to tell apart from instrument cables. However, the cable itself is very different. It has two conductors and no shield at all. Back in my old days, we made speaker cables out of Tip Shield ¼ connectors from Electrosonic and used what was commonly called lamp cord for the wire. This wire has no shield and has two independent conductors. It’s built to move a lot of voltage, and the thicker the gauge, (lower the number) the more energy you can move down the cable. Today’s speaker cables are still two conductor affairs, with no shield but cased in tougher materials, with each conductor wrapped in its own cover. Speaker cables move a lot of power and are not really susceptible to interference so there is no shield. The heavier gauge wire is needed to allow the amount of power the amplifier is pushing out to get to the speaker without causing issues. 16 AWG gauge is common here, but for longer runs you will finder thicker conductors in use from time to time.

Why to Not Use Speaker Cable for your Instrument

The big deal here is that there is no shielding. Your cable is carrying a very low level signal and thus collects interference and noise like an antenna. Your signal is degraded and things sound lousy.

Why to Not Use Instrument Cable for your Speaker

The problem here is that the very thin conductor is like a really narrow hose and your amp is looking for a really big hose. This means that the cable is going to dissipate a lot of the energy as heat. If you find your instrument cable getting hot, time to junk it, but also confirm that it’s not actually a speaker cable. The speaker is also expecting two conductors with the same power transfer capability. You do not get that in an instrument cable. The shield is not built to carry a signal.

Some folks say it’s not a problem at low output levels at the amp, but my guidance is just don’t do it. If you run your amp with a high level of output into an instrument cable, the cable could melt, could start to burn, or seriously damage your amps output stage because it cannot push the power it is making down the wire. Not worth it.

The Recognition Problem

Labeling cables by the maker should be standard to indicate instrument or speaker type. Some say instrument on them not for convenience but because the maker proposes that direction of signal travel matters. That’s a very different discussion. I recently bought a few different speaker cables from different makers. None of them were clearly labeled as speaker cables. Thus once the pegboard card is tossed, you cannot tell by looking at the cable if it is speaker cable or instrument cable. If that bugs you, join the club. If you can unscrew the connector cover, you can check how many connectors the cable has and if it has or does not have a shield. What a nuisance.

My proposal is one of those handheld labellers. While you can buy cable tags to attach to the wires, many don’t bother. If you print one of those labels and leave enough leader, you can wrap it around the cable perpendicular to it and then stick the ends to each other. They hold up very well in this manner and it’s pretty cheap, certainly cheaper than blowing a gig with the wrong cable or blowing the output stage of your amp.

Thanks for reading and until next time, peace.