How to Change the Speaker in a Guitar Amplifier
- Sep 22, 2020
- in MDM How-To
In this post we’ll cover some tips on how to change the speaker in your guitar amplifier, either because you’re replacing a blown-out speaker or because you are upgrading to a new speaker.
We’re going to assume that the replacement speaker has specifications for impedance and physical size that match the old speaker. Matching the impedance, meaning replacing an 8-ohm speaker with another 8-ohm speaker (or 4-ohm with 4-ohm etc), is important to ensure you maximize the amp’s performance and don’t risk damaging the amp. If the speaker impedance or physical size are different, then additional factors must be considered, and they are beyond the scope of today’s post.
Back-loaded combo amplifiers are the most common for guitar, so that will be our model for this procedure. We discuss other amp types below. OK, here we go:
- Make sure the amp is unplugged from the AC power outlet and then lay the amp on its face.
Remove the backplate of the amp (if it has one) to gain easier access to the speaker. See photo above for a typical example of backplate with 6 screws. This amplifier also has a black metal screen that needs to be removed but this is not typical.
REMOVE THE OLD SPEAKER
- Find the (+) and (-) indications on the speaker terminals and make a note of which color wire is connected to each. Take a look at the photo above and see that the (+) is embossed on the grey terminal holder card, so the other terminal is the (-) by default.
- Disconnect the speaker wires, typically by holding the the barrel of the removable connector (the yellow area in the photo) and gently pulling the the connector from the spade terminal.
- Next remove the (typically 4) screws or nuts holding the speaker in place and carefully lift the speaker out of the cabinet.
FINAL CHECK ON REPLACEMENT SPEAKER
- With the old speaker out, and your new replacement speaker close at hand, this is a good time to compare them and make sure they are the same impedance and that the mounting holes line up the same. The impedance is typically marked on the back of the speaker (see photo above showing "8 ohms") or sometimes on the side of the housing enclosing the speaker coil.
MOUNT THE REPLACEMENT SPEAKER
- Now that you've confirmed the matching specs and size of the replacement speaker go ahead and position the speaker over the mounting holes inside the amplifier. Some amplifiers attach the speaker with nuts that thread onto a permanently mounted screws. In this case be VERY CAREFUL when positioning the speaker so that the screws align with the speaker mounting holes and do not pierce the speaker cone diaphragm, as indicated in the image above.
- With the replacement speaker in place attach it using the screws or nuts removed in Step 5. Tighten the connection taking care not to over-tighten and strip the screw/nut.
- Now re-attach the wires disconnected in step 4, paying attention to your notes on which color mates with the (+) and (-) terminals. The white wire to the positive and black wire to the negative is typical but not a rule.
- Replace the back plate and any other cabinet parts in the reverse order from their removal in Step 2.
- Do a quick final check that the wires are connected, then return the amplifier to upright and plug it in for a test of the new speaker.
FOR DIFFERENT AMP CABINET STYLES
Guitar amplifiers come in several different cabinet configurations and numbers of speakers but the steps to replace a speaker are very similar for almost all.
If you have a front-loading speaker cabinet the speaker grill and speaker need to be removed before you can disconnect the wires.
Speaker grills are typically attached with hook/loop fasteners. The grill is removed by inserting a thin flathead screwdriver in the slot where the grill touches the cabinet side and then gently prying it up until you can grab the edge. Put the grill aside and remove the screws holding the speaker in place. Lift the speaker and there should be enough slack in the wires to allow you to rest the speaker on the cabinet front face and disconnect the wires as described earlier.
Here's a nice video from the folks at Fender illustrating many of the steps discussed in this post.