The sound of combined speakers has many elements: increased volume, more speaker surface, and higher wattage handling capability, to name a few. Depending on the configuration, multi-speaker set-ups also benefit from increased resonance and comb filtering and phase cancellation in a single cabinet or the ability to separate the speakers into multiple cabinets and disperse sound across a wider area.

History

Fender pioneered the concept of multiple speakers for a single guitar amp in the 1940s with the Dual Professional, a combo amp featuring 18 watts into two slightly angled 10-inch speakers. At the time, the dual-speaker concept was adopted to provide more clean headroom at louder volumes. The name was changed to the Fender Super, the circuitry slightly altered and with ever-changing tastes in music, the amp ironically became highly prized for its overdriven sound. Through the 1950s and ’60s, guitar amplifiers were made increasingly louder to keep up with performance demands and more speakers were added to the designs. As these amps were pushed to their volume limit, each had their own distinct overdrive character, which the speakers greatly influenced. With the advent of the separate amplifier and speaker cabinet, originally known as “piggyback” amps, mixing-and-matching amps and speakers became a common practice.

The most common way to group speakers in guitar amps and cabinets is in pairs, either two or four speakers. Although other combinations are used: the 8×10″ Ampeg SVT-810E cabinet, Pete Townsend’s original Marshall 8×12″ cabinet, the 3×10″ Fender Bandmaster and the 6×10″ Fender Super Six amp for example, weight, physical size, and wiring configurations make speaker cabinets of either two or four speakers the most practical.

Allowing for differences in guitars, playing styles, amplifiers, the speakers themselves, and a host of other variables, general statements can be made about sound and application of the most common speaker combinations. I’ll use comparisons in familiar settings as a reference.

Tens

Two 10-inch speakers in an open-back combo conjures up sonic images of a Fender Vibrolux. A mid-powered amp that has more clean headroom than its 1×12″ sibling, the Deluxe, the Vibrolux is surprisingly warm and full-sounding with nice projection and top end at lower volumes; the combined 20 inches of speaker surface is very efficient. When pushed to higher volumes and overdrive, the smaller individual speakers provide a nice crunch with upper-mid bite and the character of their higher-voicing is more apparent.

A well-known 4×10″ sound is the blackface Fender Super Reverb; think SRV — the song “Pride and Joy” specifically. Although this combination shares many of the same sonic characteristics as two 10-inch speakers, increased wattage and speaker surface, along with the dramatic comb filtering that results from four speakers mounted in the same cabinet, creates an undeniable, unique, hard-hitting sound that is brash with just enough top-end compression to not be harsh. The Fender ’59 Bassman also shares this speaker combo and even though the amplifier is designed differently, there are easy sonic comparisons concerning the speakers. A few companies have made closed-back 4×10″ cabinets for guitar but they are not very common. Typically, closing the back of a guitar cabinet yields an increase in the lowest frequencies and a focused projection out the front of the cabinet, as compared to an open back.

Twelves

The sound of an open-back, 2×12″ speaker configuration for guitar is balanced and classic. The Vox AC30, Marshall Bluesbreaker, and the Fender Twin are sonically diverse combo amps that all share this format. The 12-inch speaker is ideally voiced for electric guitar and doubling the speaker surface and wattage makes for a loud, compact, albeit heavy, guitar rig that’s capable of clean headroom and nice girth. Closing the back tightens the low end and increases the overall punch, the Mesa/Boogie 2×12 Rectifier cabinet and the Orange PPC212 are excellent examples.

The most iconic image of a guitar speaker cabinet is undoubtedly the 4×12″. Designed for the 100-watt Marshall “Plexi” in 1965, the combination of 48″ of total speaker area and a large, closed-back box makes for a massive tone. Combined with a high-wattage amp, the sheer volume of a single 4×12″ cabinet can be stunning, let alone two of them together. If you need maximum chunk, the 4×12″ is your cabinet.

Mix It

Combining speakers of different wattages with a single guitar amplifier can prove interesting, sonically. This can be done in a single cabinet or separate cabinets. Since both speakers receive the same output from the amplifier, the speaker with the lower wattage rating will be working harder, producing a less efficient output that is closer to break-up. The speaker with the higher wattage rating will work more efficiently and sound smoother. Of course, the design of the speaker itself and the type of cabinet it’s in will influence these factors as well. Using a 12-inch speaker in one cabinet and a 10-inch in another gives you a best-of-both-worlds scenario. Full and chunky with beefy low-mids and a chimey bite in the upper-mids. Putting some physical separation between the cabinets further enhances the effect. Those parameters can be pushed farther by doing the same thing with a 2×10″ and 1×15″ set-up. Usually seen in bass guitar rigs, this high-wattage combination can offer bottom-end definition without sacrificing midrange punch.

As a general rule, make sure that the combined wattage rating of your speaker combination is greater than or equal to the wattage rating of the output of your amplifier, to minimize speaker damage. Also keep in mind that since all speakers receive the same output from the amplifier, your lowest-watt speaker is the starting point for figuring total wattage necessary. Here’s an example: for a 50-watt amplifier with a two-speaker set-up, a general rule of thumb is to use two 25-watt speakers as approximately one-half of the wattage of the amp will be distributed to each speaker.

Part four of this series will focus on the technical matters of impedance, wiring diagrams, and what effect they have on your amplifier and overall sound. Always remember to use your ears as your ultimate guide.

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