Speaker Cabinet Designs 101 [How To Build a Speaker Cabinet]

How To Build A Guitar Speaker Cabinet

guitar cabinet factory 4x12

Ask a group of guitarists what their favorite instrument, amplifiers, and effects are, and each one will surely ramble on for hours about his gear of choice. Ask that same group about their favorite speakers and cabinets, however, and many of them will likely respond with a simple “I dunno.” The sad truth is that even though cabinets and speakers play major roles in shaping the tone of a guitar sound, they are often overlooked by players.

The overall sound of a cabinet is the result of all the components that go into building it and how they’re put together. Once you acquire the knowledge of what goes into building speakers and cabinets, you’ll start to understand exactly what you like and dislike about different cabinets. In this lesson, I’m going to focus on defining the components and materials that go into building speakers and cabinets as they relate to the sound they produce. My hope is that at the end of the two lessons, you will be well informed and on your way to identifying what your preferences are and what speakers and cabinets complement your playing the best.

What Type of Wood Is Best To Build a Guitar Speaker Cabinet Out of?

birch plywood to make guitar speaker cabinetWith very few exceptions, cabinets are made out of wood. Plied birch wood is far and away from the most common choice, though some cabs are made from particleboard or a combination of the two. Sonically, birch is great because it strikes a very desirable balance; it’s rigid enough to produce punch and definition while being soft enough to sound warm but not floppy. Remember that the cabinet acts as a resonator for the speakers just as the wood of a guitar acts as a resonator for the vibrations of the strings. Birch is also super durable and is well suited to withstand the vibrations, abuse, and travel that a cabinet is likely to endure.

How Thick of Wood Should a Guitar Cabinet Be?

The average wall thickness of a 4×12, 2×12 and 1×12 cabinets is ¾-inch, though some combos have been made from one-inch thick wood. A one-inch wall will be more rigid and will produce a tighter, darker and more blunt sound; a ½-inch wall will usually accentuate high frequencies.

Should The Guitar Cabinet Be Open Back or Closed Back?

loosening the screws on the back of a guitar speaker cabinet tunes the soundAnother factor to consider is whether the cabinet has an open back or a closed back. Open back cabinets generally don’t produce as much low end because the back pressure created by the speakers has a lot of room to escape. With a closed-back enclosure, the back pressure has a much harder time escaping the cabinet which, in turn, creates a more significant low-end resonance. In some closed back and front-loaded (where the speakers are mounted on the front of the baffle board) cabinet designs, you will see holes in the front or back of the cabinets. Those holes are known as ports and are intended to let some of the back pressure escape to allow for desirable frequency response.

Nifty Trick How You Can Tune Your Guitar Cabinet

An interesting characteristic I discovered about closed back cabinets is that you can change the sound of the cabinet by loosening and tightening the screws that hold the back board on. By loosening (or removing) some of the screws, you can “tune” the cabinet to be soft and floppy. If you want clarity and defined punch, use all the screws and tighten them up. It’s similar to the way drums are tuned—just think of the back board as the drum skin and the rest of the cabinet as the drum.

Does The Vinyl Covering Change The Sound of a Guitar Cabinet?

Another thing that I’ve found to affect the sound of a cabinet is the vinyl covering and the glue that holds it onto the cabinet. The glue and the vinyl slightly muffle the higher frequencies, in most cases in a desirable way. I first discovered this when I decided I wanted one of my 4x12s to have bare wood finish and proceeded to rip off all the vinyl. After the vinyl had been stripped I noticed a difference in sound.

Does The Age of the Guitar Cabinet Matter For Sound?

guitar speaker cabinet DovetailThe age of the cabinet and the amount of time it’s been played also affect the sound. An old cabinet with years of use and heavy gigging will, in time, soften up and lose it’s stiffness-sometimes too much for desirable results.

Should My Guitar Cabinet Have Castors or Rubber Feet?

The sound of a cabinet is also affected by what surface it’s sitting on. I’d much rather have my amp sitting on a wood floor than carpet or concrete. Wood interacting with wood will only extend the resonance of an amp as opposed to carpet or concrete which have little or no resonating abilities. For the same reason, I also recommend resting cabinets on rubber feet or nothing at all, as opposed to leaving the wheels on all the time.

Cabinet Fever – Part Two: Speaker Components

Now Let’s Take a Look At The Parts of a Speaker – Speaker Cabinet Designs Part 2

Celestion Greenback speaker cabinetIn September we wrote an article about the particulars of speaker enclosures and how they affect the sound of a cabinet. This month, we’d like to focus on the intricacies of the speakers themselves and their components.

A good speaker can be the difference between and awesome tone and a lousy one. But it’s not always that simple; a speaker that sounds good in combination with a certain amp and guitar will not necessarily sound great with every amp and guitar. There are several factors that need to be considered when attempting to achieve the perfect balance between a guitar, an amp, and a speaker.

Speaker Power Handling

For one thing, there’s the relationship between the wattage and the efficiency of a speaker and the amplifier that’s feeding it power. If you’re going for a very clean sound, you want your speaker to be able to handle all the power that your amp can give it and then some. If your amp is more powerful than your speaker’s power-handling capability, the speaker will be pushed to its limit, adding distortion to your sound. A good way to demonstrate this would be to take a 100-watt amp and plug it into a 100-watt cabinet and then into a 200-watt cabinet. The 100-watt cab will sound more distorted than the 200-watt cab because the speakers in the 100-watt will be pushed closer to their maximum capability, resulting in distortion. That’s why many players favor lower-wattage speakers driven to distortion by powerful amps.

Guitar Cabinet Speaker Magnets Types

The magnet contributes heavily to a speaker’s overall tone. The most common types of magnets found in guitar speakers are ceramic and alnico. The very popular Celestion 25-watt “greenback” has a ceramic magnet and, although it has less of a focused field of energy, it has its own character and a very cool sound. On the other hand, the highly acclaimed blue-colored Vox bulldog speakers, as well as some JBL and Electro-Voice (EV) speakers, use alnico magnets. Alnico magnets also have their own sound and character which, to my ears, is a little more focused.

Speaker Cones Types

Guitar speaker cones are made out of paper. When people refer to ‘vintage style cones,’ they’re talking about very simple, low-tech, flat paper cones. As guitar sounds evolved over the 40 years, some speaker manufacturers incorporated more intricate cone designs by introducing ripples and ridges with the goal being better rigidity and stability at higher power to stave off distortion.

Speaker Voice Coil For Guitar Cabinets

speaker voice coil for guitar cabinetThe voice coil is attached to the cone at the center of the speaker. It is here that the speaker goes from being an electronic device to an acoustic device. The coil is an actual coil of wire with connectors at each end that connects to the output of the amplifier. Think of the speaker as a loop with positive and negative designations, since that’s how it’s connected to the amplifier. When you play, the output of the amplifier sends a signal to the speaker which causes it to push out. When you cease playing, the output of the amplifier pulls the speaker back in. The reason that speakers are labeled positive and negative is so they can be polarized amongst other speakers without being out of phase.

The Speaker Frame [or Basket]

The housing in which all of these components are mounted is called the frame or the basket. The majority of frames are made by stamping a flat sheet of steel and bending it into its final shape. Steel is used because it’s relatively inexpensive and very strong, which is important so that its shape doesn’t change. Some high-end speakers use what’s known as a cast frame or speaker basket. Cast frames are made by pouring molten aluminum or a similar allow into a cast. When the alloy cools off and hardens, it’s almost impossible to distort or alter the shape of the frame, which makes it an optimal mounting for the components of a speaker.

The Impedance of a Speaker

No discussion of speakers could be complete without including some mention of impedances. What I’ve come to learn over the years is that the impedance of a speaker is an arbitrary decision made by the manufacturer. Leo Fender, for example, was really only making amplifiers with one or two speakers and decided that, with one speaker connected, it would be eight ohms, and with two in parallel, it would be four ohms—while taking into consideration that eight-ohm efficiency is an audio amplifier is most efficient for direct music input. In contrast, the British giants like Vox and Marshall pursued greater versatility in combinations of speaker hookups and settled at 16 ohms to facilitate their needs. Just make sure the impedance on your amp matches your cabinet(s).

That’s all for now. Next time we’ll look at different types of speakers. Come join us at Gear-Monkey Music Gear Message Boards

4 Comments

  1. IN YOUR DISCUSSION OF SPEAKERS ABOVE YOU STATE THAT WHEN YOU PLAY THE GUITAR THE SPEAKER CONE IS “PUSHED OUT” AND WHEN YOU STOP, THE CONE IS “PUSHED BACK IN”. I FIND THIS TO BE MISLEADING AT THE LEAST. WHEN THE AMPLIFIER SENDS A SIGNAL TO THE SPEAKER, IT IS AN ALTERNATING CURRENT SIGNAL, AND CAUSES THE CONE TO MOVE FORWARD AND BACK WITH THE FREQUENCY OF THAT SIGNAL. THE CONE MOVES FORWARD AND BACK AS LONG AS THERE IS A SIGNAL SENT TO IT.
    YOU ALSO STATED THAT THE ALNICO MAGNET IS “A LITTLE MORE FOCUSED”. ACTUALLY THE ALNICO SPEAKER SOUNDS BETTER TO SOME BECAUSE IT IS NOT AS EFFICIENT, AND ACTUALLY GETS LESS FOCUSED OVER TIME BECAUSE IT IS NOT A PERNANENT MAGNET AND IT DETERIORATES OVER A PERIOD OF YEARS. I’VE HEARD OF SOME PEOPLE ACTUALLY TRYING TO “AGE” THE ALNICO SPEAKERS BY ABUSING THE MAGNETS WITH A MALLET OR HAMMER. OLD, NATURALLY AGED ALNICO SPEAKERS ARE VERY HARD TO FIND, AND EXPENSIVE, BUT I WON’T BE USING A HAMMER TO AGE MINE.

  2. Hi – I have a 100 watt Peavey Vypyr combo amp with 2×12 speakers. The speakers have 8 mounting holes each but are only secured with 4 screws each, which is as originally supplied from the factory. I get some annoying vibration from using the speakers which is not there when using headphones or DI into a USB adaptor to a laptop. Should a speaker with 8 mounting holes have 8 screws and might this cure the vibration? Thanks in anticipation

  3. Thanks Charlie – it maybe the screws were overtightened. When the Covid lockdown is lifted i will get my torque wrench (in another location) and try even tightening.

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