Fix It Friday : Diagnosing a Speaker Extension Cabinet

Written by
Logan Tabor
Published on
March 23, 2021 at 11:25:33 AM PDT March 23, 2021 at 11:25:33 AM PDTrd, March 23, 2021 at 11:25:33 AM PDT

This week on Fix It Friday we are going to be taking a look at my speaker cabinet (as seen below), and asking ourselves, “Why isn’t this thing working!?” For many of us, things like a speaker cabinet shorting out can be mysterious and intimidating, but they don’t have to be. Let’s take a closer look at this cabinet to find out what the issue is and see what we can do to take care of it before my gig next week!

Before getting too deep into it, we will want to test the circuit with a different speaker cable (if you are running a piggyback type rig) to make sure it’s not something as simple as getting a new cable. Additionally, it may be best to attach your amplifier to a different speaker cabinet altogether to make sure this issue is not with the amplifier itself. Once these possibilities have been eliminated, it’s time to start testing for shorts within our speaker wiring. The first thing we want to do in this situation, because this is a closed back cabinet, is remove the back panel (Image 2A). Once this is done we can see that we are working with two 10” speakers and a simple wiring harness with a Switchcraft J11 jack (Image 2B).


The first thing to look for would be any loose connections. Often times, especially with gigging musicians, a cabinet can rattle so much that over time a speaker connection can wiggle loose from its terminal and cause a problem with the cabinet. Look for loose wires around the terminals like the one outlined in red below (Image 3A). 

If you do see loose connections, go ahead and reconnect and then pull out your multimeter to give the circuit a test (Image 4A). The issue with my cabinet is NOT a loose connection, but for learning purposes, let’s pretend there IS a loose connection. In this case, I have two 8 ohm speakers wired in parallel for an overall 4ohm load. If my cabinet is functioning properly, I should see a reading of about 2.8 on my meter. In the picture below (Image 4B), you see a reading of 5.2 which means one of my speakers is disconnected or non-functional.


Lucky for me, I can easily see a rogue wire, and I simply refasten it to its corresponding speaker terminal. Something to note here is that if you have a single speaker in your cabinet, a disconnected speaker wire will read on your multimeter as nothing. BUT a problem with your jack will also read as nothing. So, if you don’t see any disconnected wires, you’ll have to keep digging…

Something else that happens often to speaker cabinets is that they are moved around for practice and performance, and often they are touched by many people. Sometimes, when a speaker cabinet is plugged in (with a cable hanging out the back of it) the speaker cable will get bumped from the outside. This can lead to the contact on the jack being pushed away from the cable and no longer being able to make a proper connection. Take a look at the image below to see what it looks like when this happens (Image 5A). The issue with my cabinet IS a bent contact in my jack. I can see it and I can confirm it by using the multimeter — I’m getting no reading on my 2x10 cabinet, so at this point it’s obvious that the jack is my issue (Image 5B).


Since I already have my cabinet open, I’m electing to go ahead and replace the portion of my speaker wiring harness that is connected to the jack. This will give me a fresh start at a low cost and it’s something any guitarist can do themselves. So once you’ve purchased the appropriate premade wiring harness, the first step is to connect your harness wires to the corresponding speaker terminals (Images 6A + 6B).


Some speakers have screw down terminals (these tend to provide the most reliable and long lasting connection) but most guitar speakers will have traditional spade terminals. For these, you can either buy a harness with spade connectors already crimped onto the ends of the wires, or if you prefer, you can solder your wires directly to the speaker terminals. Note: soldering directly to the terminals will give you a solid connection but will prove to be more difficult to work with when you decide to change the speakers in your cabinet one day. Once your connection is made on that end, insert the threaded portion of the jack into the jack plate, slide a washer onto the jack (exterior side of jack plate), and lastly slide on the fastener nut and tighten it down. 

In my case, I need a 4ohm load which should have a reading of about 2.8 on my multimeter (Image 7A). Looks like our repair was successful. The only thing left to do is plug my cabinet into an amp and make sure it screams!


Thanks for hanging out with us on this lovely Fix It Friday. For more tech tips and cool project ideas, keep an eye out for the next installment of our Make It Monday and Fix It Friday series’.