How to Wire a Speaker Boxby Jeff Grundy
For many discerning listeners and audiophiles, the stock speakers that ship with receivers or home entertainment systems seldom provide the acoustic range, clarity and musical neutrality needed to satisfy their listening needs. Of course, you could buy a better pair of speakers to add to your audio system. However, not everyone can afford the price tag of a set of high-end commercial speakers. If you're handy with some basic hand tools, you can build your own premium loudspeakers and save a considerable amount of money. Before you wire your new speaker boxes, lay some groundwork. proper design and planning of the cabinets is essential to ensuring optimal sound and avoiding potential wiring or phase issues.
Cabinet Design Basics
Designing and building an efficient loudspeaker requires much more than just nailing a few pieces of plywood together to make a box. The size and layout of your cabinet boxes depends primarily on the drivers you select for your loudspeakers. Loudspeaker drivers usually have ratings called Thiele/Small parameters, which determine the volume size of speaker cabinet required to produce optimal sound. You may see the ratings displayed as "Q" and "F" on the rear of the driver or its documentation. A good speaker-modeling program can help you determine the size and dimensions needed for your cabinets. Applications such as WinISD, LspCAD and CLIO (links in Resources) all let you input Thiele/Small parameters and then display the volume requirements for your cabinets. In addition to planning the size of your cabinets carefully, using the layout patterns included with your drivers will help make considerably easier to make the speaker holes in the cabinets. You should plan your driver holes, portholes and terminal block (the block where you connect the wires from the stereo or amplifier) location carefully so your cabinets will be easier to wire once you finish building them. Put simply, the more time you spend planning the design of your cabinets, the easier they will be to construct and wire. At a minimum, create a working schematic or sketch of your cabinets before you start. Ensure that you note locations of drivers, the crossover and the terminal block so you can visualize what the wiring should look like. If planning your first DIY speaker system, you may find it easier to use a kit that includes precut pieces for assembling the cabinets.
A crossover allows certain frequencies to pass to various drivers in your loudspeakers. For example, a simple two-way crossover sends high frequencies to the tweeter driver and lower frequencies to the bass driver. A crossover is essentially a small board consisting of wired coils, capacitors and resistors. The layout, size and values of the individual crossover components determine the cutoff frequencies passed to or blocked for individual drivers in the speaker cabinet. The number of wiring leads on the crossover determines the number of drivers you can wire to it. For instance, the crossover for a basic speaker with woofer, midrange and tweeter driver would have four wiring leads: one for each driver and one leading to the terminal block. Soldered connections for the wiring from the drivers or terminal block to the crossover work best. However, if you aren't handy with a soldering iron, butt connectors and a crimp tool will suffice. When wiring the crossover to the drivers, use a thick 10- or 12-guage speaker wire for speakers that handle a lot of power. For speakers you want to connect to a modestly powered amplifier, thin-gauge wire is acceptable. Mount the crossover on the rear wall of the cabinet or the base to make wiring drivers and terminal block easier.
The Terminal Block
The terminal block is the area on the speaker cabinet where you connect the speakers to the wires leading to your amplifier or receiver. The block you select may have push terminals or twist terminals for connecting the speaker wires and should attach to the rear of the cabinet. Wiring the terminal block to the crossover is relatively simple and requires just two short wires running between the two components. Just as with wiring the drivers, soldering is the best method for connecting the crossover to the terminal block. Nevertheless, you can screw terminals or butt connectors if you don’t want to solder.
Testing and Mounting
Before you mount anything in your speaker boxes, you should lay out your drivers and components and test them. Place your crossover in the center of a large table or work surface and then surround it with the drivers and terminal block. When testing the drivers and components, don’t solder the wires or make connections with butt connectors. Instead, lightly twist the wires together or use a little electrical tape to keep the wires touching. Connect your amplifier or receiver and keep the volume low as you test the sound to ensure the drivers and wiring works as planned. After testing, connect the wires to the rear of the drivers before mounting inside the cabinet. Leave a little slack in the wires so they can reach the crossover. Likewise, connect the wires to the crossover before securing it to the back or bottom of the cabinet with screws or hot glue. You can wire up the terminal block after you secure it in its hole on the rear of the cabinet. Once all of your connections are secure, you can mount the drivers and seal up the cabinets.
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