What the hell is an ohm?!

tl;dr

I made some sketchy choices on cheaping out on speaker wire, and then did some refreshing on high school electrical physics calculations. My calculations lead me to believe my setup is not a fire hazard.

Loud beginnings

In the summer of 2023, I picked up some truly brash old Sony speakers from someone who left them on their curb in my town. For nearly a year, they sat in a closet because I didn’t have an amplifier to power them. Finally, I found an equally crummy amplifier at our town’s local recycling center, and I was “lucky” enough that the passive Sony speakers had (nonremovable) wires already running into the unit - I didn’t have to worry about getting separate speaker wire. I plugged them into the amp, and with enough tinkering, they made sound. Much to the dismay of my roommates.

See, the Sonys seemingly use every cubic inch of their particle board construction to produce muddy music, and that means a lot of bass. Bass travels. As you get further away from any fesitval or open air event with big speakers, you’ll still hear the thump-thump-thump of the low-end frequencies, and unfortunately, the thin walls of the house that my roommates and I rent don’t do much to dissipate those thumps from the old Sony’s.

Thus, they have sat mostly-unused, until our neighbors asked to borrow them for a backyard party. They sounded good, up until the 80% volume range, where the speakers started to blow out. I tried my best to convince Ed to turn down the speakers so they wouldn’t blow out, but this crowd cared less about distortion-free music, and more about hearing (yet again) that thump. To each their own.

Quieter improvements

Having reached the peak of mount stupid on the Dunning-Kruger curve of “knowing stuff about speakers and amps”, I got my hands on two more pairs of speakers and amplifiers, The first being these truly wonderful JPW Mini Monitors and a Harmon Kardon 230. I needed to connect the amp to the speakers, and I googled for “speaker wire”. I ended up purchasing a spool of 24AWG wire from Home Depot. The JPWs sounded blissful, and I was really happy with the setup. I was blissfully unaware of the importance of wire gauge, but I simply got lucky.

Mathematics

Anyone who knows a shred about speaker wire should have alarm bells going off in their head. 24 gauge wire?! It was like building an interstate bridge out of toothpicks: bound to destroy itself, and hurt someone in the process. Well, luckily for me, my amp seemed to be ridulously low powered as an amplifier. To finish the analogy, all the cars on this interstate were filled with helium, making a bridge of toothpicks somehow not a problem.

This Harmon Kardon 230, has seemingly only one blog post worth of information online. The documentation states that it’s rated to output 10 Watts at 8 Ohms. Of course, the speakers that they’re hooked up to happen to be 6 Ohms. This makes the little cheat-sheet they gave me less of a cheat sheet of voltage ratings and more of a homework question on Ohm’s law.

This wonderful Ohms calculator has taken most of the hard work out of this, but not before I tried to do my own chicken scratch math. With the wattage and resistance from 10W at 8 Ohms, this works out to 8.94 volts and 1.12 amps. At 20W at 4 Ohms, this is again, 8.94 volts and 2.23 amps. Now, using 8.94 volts and 6 ohms, this gets us 1.49 amps. and roughly 13 Watts.

So, the speakers are presumably getting 13 Watts, which is less than the 70 Watts they’re rated for, but man they sound warm and nice anyways.

But I wasn’t concerned about the speakers getting too many watts. My main concern is the amperage, as this seems to be the limitation of concern for wires of various thicknesses. Googling “how many amps can 24 AWG handle” gets a variety of answers, with some sources saying numbers as high as 13 amps and others quoting 0.5. If I go by Georgia State University’s cheat sheet, they say 24 AWG wire can handle 3.5 Amps if it is used for “chassis wiring”.

Chassis wiring? This is a general description for wires that go “a short distance” and have ample “breathing room” around them that will cool them down. Cooler wires that aren’t bundled together can run more amps, as they have more opportunity to (thermally) relax before they light themselves, or something nearby, on fire.

This other cheat sheet states that depending on the number of cores (the number of strands that make up the wire), I’m looking between 1.2 and 1.6 amps. I believe the wire had 4-6 cores, meaning I’m leaning towards the top-end limit of 1.6, making the calculated 1.49 amps at 6ohms just barely within spec. It’s a thin rope I’m walking here.

In reality, I will not be throwing 100% of the amplifier’s output at these speakers, and it’s highly unlikely that it would be a sustained load on top of that.

Regardless, I learned a lot about speaker wire, and will probably invest in replacing this speaker wire in the future with higher gauge, just for the peace of mind.

Climbing the valley of despair

Satisfied with these zone-out-on-the-couch worthy set of speakers, you’d think I’d be content with what I had, and wouldn’t be interested in more audio gear. You’d be wrong. I caught the bug.

A family friend was upgrading their (already really nice) TV audio system, and knew that I was one to tinker with just about anything with a power button. Thus, I came to be in possession of a 7.1 Denon something-or-other amplifier, and around the same time, was reminded that my dad had a pair of large, unused Klipsch bookshelf speakers hiding in the house.

Again, I found my self in the wonderful predicament of interesting amplifier + neat speakers, and no speaker wire to connect the dots. This time though, I was working with considerably more power. The Denon system claimed 100 watts!? of power to each channel (read: each speaker) of audio, and the Klipsch speakers were rated to handle it. 100 watts was going to be considerably louder than the 13 that was going through the JPWs, and I wasn’t going to risk a toasty wire run just to save a buck on speaker cabling.

Thus, I did not cheap out on the speaker wire this time. Instead, I cheaped out on some awful banana plugs from Home Depot. They do NOT clamp down very firmly on the stripped end of the wire, no matter how tightly I screw in the little clamping screw. They will slip out at the earliest convenience, namely, every time I trip my foot on the cable or move the speaker around. This could be fixed with being decisive about where I want to keep the speakers, though.

100 watts is ridulously loud for a small-ish house. Would recommend, if you wanted “whole home” audio without paying the Sonos premium. (When I mean whole home, I mean that at full volume, you’ll hear it in every part of the house, no matter which room they’re in.)

Long story short: Need speaker wire? 14AWG. Don’t skimp on bargain banana plugs. Don’t annoy your roommates.