Not everyone can be good at all things. Take, for example, stereo systems. Just because you can build an 800hp motor, doesn't mean you can build a kick-butt system. Thank goodness the world today is full of great technology that you can have at the touch of a button. Just as you can buy a prebuilt crate motor, you can also get ready-to-go sub enclosures that perform much better than a couple pieces of plywood and some scews.
We got a good look at one such enclosure during a demo we received from MTX at the 2004 Consumer Electronics Show. The company had one of its prototype Sledgehammer boxes spliced into the stock system of a Scion, and it really hit. The boxes are truly impressive for a drop-in unit. All you have to do is give them enough wattage and then sit back and enjoy the massage. They come in a variety of sizes and power capabilities.We chose to focus on the 7500 series because it will fit in the back of just about all the extended-cab minis made.
MTX acoustic engineers designed the enclosure to optimize performance and efficiency. Each enclosure is constructed with 3/4-inch MDF for durability and features a unique slot port design that provides an oversized area, which moves large amounts of air with virtually no vent noise.
Moving all that air is the new 12-inch Thunder 7500 Superwoofer. Weighing in at more than 20 pounds, the T7500 is capable of handling 400 watts RMS and offers a variety of features, including a die-cast-aluminum frame, solid-steel pole piece, expanded poly-cone dust cap, rubber surround, tinsel leads mated to heavy-duty terminals, and Spider Plateau Venting technology.
To power the Sledgehammer enclosure, we needed a serious amp. Thankfully, MTX has those, too. MTX told us that the Thunder 801D would be the perfect amp to power the subs. The amp features MTX Audio's Adaptive Class D Technology, a 40-200Hz low-pass crossover, low- and high-level inputs, and a compression circuit to protect the 'woofers when the system is turned way up, and it's only 12x10 inches in size, so it will fit nicely under the seat.
To bring juice to everything, we also picked up a StreetWires four-gauge amp install kit that gives us all the necessary wires, terminals, blocks, and even zip ties needed for the hookup. With all the instructions and wiring diagrams that come with the amp and wire kit, there should be no reason anyone couldn't accomplish this install - that is, if you have tools.
Here is the Sledgehammer box from MTX. As you can see, this is no swap-meet box. These are made to produce serious bass - and they do. The slot port design is very efficient at moving air, and it cuts down on vent noise. They are covered in carpet and capped with a molded ABS plastic front fascia for a nice look.
The amp needed to drive these speakers also has to have some oomph, so the Thunder 801D was sent with the order. This is a class D monoblock amp, and it's made to do one thing: power large speakers. The amp features high- and low-level inputs, so it's easy to tap into factory systems and a low-pass crossover, variable from 40 to 200 Hz, so you can tune it to your specific musical tastes.
Inside this box is MTX's 12-inch Thunder 7500 Superwoofer. It's built with all kinds of confusing technology, so, for the non-techie, let's just say this sucker is pretty tough. For you real tech heads, check out the spec sheet on www.mtxaudio.com.
+Class D Amps 101
We needed a little lesson on what Class D really means, so after talking with Rico Felice, one of the audio gurus at MTX, he turned us on to this information that's posted on the company's Web page. "Amplifiers that use Class D technology are switching amplifiers. These amplifiers feature MOSFET transistors that operate as a switch to manage the power applied to the speaker. This controlled switching creates a square wave known as Pulse-Width Modulation. High-frequency energy is generated from this square wave and is commonly concentrated at one point. Harmonics from this concentrated high-frequency energy travel into the radio-frequency range, and can cause interference with the radio's reception or through the audio system's ground, producing noise."
MTX cured this problem with its new Adaptive Class D Technology. With this approach, the amplifier's switching energy is constantly changing and is moved away from FM radio frequency ranges as the amplifier's load and output increases. This effectively eliminates the interference that is generated, thereby improving the amplifier's overall signal-to-noise ratio.
+Feeling Dim
Once an add-on system is installed in your truck, you might notice the headlights dimming when the subs go boom. This is generally caused by the heavy draw the amp and speakers put on the electrical system. There are two ways to remedy this: one is to buy a bigger alternator that puts out more amps; the other is to pick up one of these babies see here, aka a capacitor. It is basically a quick-discharge battery or, as others would call it, an electrical shock absorber. It keeps the power spikes from taxing the alternator by releasing stored power when needed.
 Hook It Up StreetWires was...  Hook It Up
StreetWires was nice enough to take all the guesswork out of buying wiring for amp installs. This four-gauge kit is designed for single-amplifier systems as high as 600 watts. It comes with all the appropriate power cables, terminals, butt connectors, and fuse holders to hook up your system. |  1. The first thing we did...  1. The first thing we did was to install the main fuse holder. For the amp, we chose to install it right by the battery on the driver-side fender. This way, we can easily see if the fuse has blown and replace it without hassle. Also, a general rule of thumb is to try to keep the fuse holder within 18 inches of the battery's positive terminal. |  2. Then the wire was pushed...  2. Then the wire was pushed through a hole in the firewall and run back to where the amp will be located. If you have to drill a hole in the sheetmetal of your truck, make sure to install a grommet to keep the metal from cutting through the insulation and causing a short. |
 3. OK, here is one way to...  3. OK, here is one way to get the signal back to the amp: it's a line-output converter. It takes the signal from your existing rear speaker leads and basically removes all the power from them. This allows the signal to be sent to the amplifier using low-level or RCA cables. High-quality converters such as the one pictured will allow you to adjust the level of each channel for the best sound quality. You won't need one if you have an amp with high-level inputs or a head unit with a subwoofer output, such as we do in this truck. |  4. We pulled the carpet out...  4. We pulled the carpet out of the truck to make routing the wires a little easier on us. We know the sub box will be in the back, so we ran enough wire for the box, routing it away from the power cables. The wires that come from the front of the truck were run along the firewall and then down the doorjamb. Keeping the signal wire separate from the power wires will help prevent interference or that annoying whine we've all heard before - and we're not talking about the one that comes from your significant other. |  5. All the solderless ends...  5. All the solderless ends needed are provided in the StreetWires kit. Strip the wire back about half an inch and crimp the terminal on. |
 6. We screwed the amp down...  6. We screwed the amp down under the passenger's seat toward the back so we could still access the adjustments and the fuses when the seat was moved forward. |  7a. Hooking the amp up is...  7a. Hooking the amp up is easy. Each terminal is clearly marked with power, ground, and so on. The low-level or RCA wires are even easier: red-to-red, white-to-white. not shown in the picture is the ground point. We drilled a hole and sanded any paint off the surface before installing the screw; this will give the amp a good, solid ground. Don't get lazy and hook it to the seat bolt; most of the time these are not the best ground you can have. | 
7b. |
 8. Call in a friend to help...  8. Call in a friend to help load the sub box. At around 160 pounds, this is no wimpy enclosure, and if you hurt your back, this box will only make it worse when you turn up the bass. |  9a. The way this box is designed,...  9a. The way this box is designed, it can either be situated facing up or forward. Up will sound a little better because the subs can push all the air freely. With it facing forward, it will cut down on the efficiency of the enclosure by a little, but we can still put stuff on top of it. | 
9b. |
 10. To hook up the subs, all...  10. To hook up the subs, all we had to do is strip the wires back and insert them into the terminals. Make sure you pay attention to the speaker-wire polarity. |  11. With everything installed,...  11. With everything installed, it was go time. We installed the main power cable to the battery and turned on the stereo. |  12. If your battery doesn't...  12. If your battery doesn't allow you to add a ring terminal like ours did, StreetWires can provide those for you, too. |
 13. We turned the head unit...  13. We turned the head unit up to about three-quarter volume, which is just about where all factory speakers start to distort, then we turned the gain up until we were happy with the bass note. Now that the main levels are set, you can add more bass by turning it up on the head unit or by turning the EQ knob on the amp. The Thunder EQ is an equalization circuit that is centered at 40 Hz and is used to enhance the low-frequency response of the subs with as much as 18 dB of boost. | | |