The three types of joinery used for building speaker cabs. Dovetail joints are the strongest and are most often found on high-end cabinets with exposed, stained wood. Diagram by C.J. Sutton
As you can see in the diagram, these are quite different from each other, but it’s important to note that unless the joint is made poorly and allows the corners to flex, the joinery type has virtually no effect on the sound. Rabbet joints are the most commonly used in domestic cabinets because they are fast and easy to execute, and they’re strong. Finger joints are the most sought-after because that’s how Leo did it in the ’50s and ’60s. These joints are stronger than rabbet joints and reduce the potential for flexing. The strongest of all is the dovetail joint. Good dovetail joints can hold together without any glue, but don’t worry—no one actually builds speaker cabinets with unglued dovetail joints. You’ll see dovetail joints on higher-end cabinets, particularly those made of stained wood with visible joints that are part of the look.
The baffle. The front part of the cabinet where the speakers mount is called the baffle. It needs to be the strongest and most rigid piece of all because this part of the cabinet is subject to the most impact stress. Baffles are nearly always made with Baltic birch plywood, or in some cases even MDF—even if the cabinet walls are made of solid wood, such as pine.
There’s a lot of hubbub about whether speakers should be mounted to the front or rear of the baffle. When a cab has a front-loaded speaker, the grille is removable to allow access to it. Front-loaded speakers are found most often in bass cabs and ported guitar cabs, where the back of the cab is designed for rigidity and is not removable. A rear-loaded speaker attaches to the back of the baffle, which you access in closed-back cabs—such as a Marshall 4x12—via a removable back panel. Most open-back combo amps also sport rear-loaded speakers.
The theory behind front-loaded speakers is that they don’t seal up perfectly to the baffle and thus allow air to escape, which adds some musicality to the sound. Also, in a recording situation, it’s easier to swap out front-loaded speakers in a quest for different tones. Conversely, rear-loaded speakers can be more of a pain to replace. In closed-back cabs, you have to remove the entire rear panel. If you’ve ever opened up a 4x12 cabinet, you know there are a lot of screws involved in securing that back panel. And if you’ve ever decided to take a shortcut and not put all the screws back in, then you know about the potential for ugly rattling.
A side note about 4x12 cabs: Some have posts inside that connect the center of the baffle to the rear panel. These baffle posts are designed to offer additional support and create one more connection point to keep the rear panel from flexing.
Speakers can be attached to either the front or rear of the baffle. Front-loaded speakers are accessed through a removeable grille; rear-loaded speakers are housed in open-back enclosures or in closed-back cabs with a removeable rear panel. Diagram by C.J. Sutton
Before you can access the rear-loaded speaker in some open-back combo amps, you first have to remove the chassis. This means virtually disassembling the entire amp. Please note: Never stick your hand inside an amp chassis. There can be lethal voltages present even after the amp is turned off and unplugged.
So is one speaker-mounting method superior to the other? That depends on what you’re after: Rear-loaded speakers form a tighter seal to the baffle and provide a sound that works well with rock ’n’ roll and heavier music, and front-loaded speakers can sound airier. But there’s no right or wrong. My friend Jason Jordan of Monarch Cabs says it best: “It’s all a matter of preference, really. What guitarists think of as a “good” sound is based on the music they listen to. As builders, we have formulas for making speaker cabs sound a certain way. It is a science. But at the end of the day, you need to experiment and listen, and then simply go with what works for you and your playing.”
Although the vast majority of amp cabs have either an open back or closed back, it is possible to have both. This 4x10 Marshall cab has been professionally modified to be configured either way, depending on the size of the stage and the band’s music. If you’re considering doing this yourself, the trick is to cut the back panel into thirds and then completely wrap each piece in “cab carpet.” This creates a super-tight fit between the panels and prevents rattling. In closed-back mode, tour-case latches hold the middle section securely to the fixed top and bottom pieces. Photo by Andy Ellis
Cab placement. So what happens when you want to take your rig public? What should you consider when placing an amp or cab onstage? The answer depends greatly on whether the cab is going to be miked up or not. If it is, then the cab can really go anywhere. To keep the stage volume down, many bands face their cabs backward—or even remove them completely from the stage—because the miked sound will be fed back through the monitors, which can be either onstage wedges or in-ear buds.