The EQ232 is a versatile piece of equipment that is a "set once and forget it" type of device, as opposed to simpler EQs that may be built into a head unit, or is a part of an under dash type accessory. In car audio circles, the EQ232 is used to intricately setup and tune-in the entire audio system so that it performs at its best. With both input gain controls and output level controls, the EQ232 can be set to deliver a hot 8v output signal to the inputs of the amplifiers, allowing them to have their input levels set very low for the best noise rejection possible. The preamp outputs of the EQ232 send their tweaked audio signal into another pair of RCA cables that feed into the preamp inputs of the right mounted Phoenix Gold ZX400Ti stereo amplifier that runs the front stage.
Each ZX400Ti amp has a built-in, variable 24 dB electronic crossover, and this first amp fully puts its crossover to use. Splitting the audio frequencies, the crossover sends all signals above 90 Hz into its host amp, and anything lower than 90 back out through a pair of RCA outputs. Another pair of RCA cables takes this crossed-over low frequency signal (90 Hz and lower) and feeds it to the inputs of the second ZX400Ti amplifier. The left and right outputs of the front stage amp are connected to each of the two MB Quart competition passive crossover via 12 gauge speaker cable. The outputs of each Quart crossover are split into two high-level signals, one for the tweeter and one for the mid woofer of the respective door mounted reference series coaxial driver, and sent there via a four-wire, 15-gauge ribbon speaker cable. Since this amplifer is running into a 4-ohm load on each channel, its output isn't at its maximum capability as it would be into, say, a 2 ohm or lower load. However, because it has a solid 14.5 volts for its power supply, there is still a healthy 150 watts or so going to each door speaker. Unlike many competition amps, Phoenix Gold amps do not have a regulated internal power supply, so anything above a 12 volt power supply will raise the rated power of the amp. With the audio signal making its final stop at the inputs of the left mounted ZX400Ti amplifier, its built-in crossover is also used, but instead of acting as a two-way crossover that splits low and high frequencies, this one is set to only act as a one-way low pass filter. Though the incoming signal is 90 Hz and lower, the crossover steps this down to 70 Hz and lower, effectively creating a "hole" in the frequency range between 90 and 70 Hz. This was done intentionally to get rid of a peak in cabin response that occurs in that range. By creating this "hole" the car's natural tendency to augment these frequencies pretty much fills in that gap. The overall effect is a very smooth frequency transition that otherwise would have never occurred. This second ZX400Ti sends its outputs via two pairs of 12-gauge speaker cable out of the amp chamber and back to the subwoofer, which is fitted with a pair of 3-ohm 12" MB Quart subs. So the ZX400Ti amp with its 14.5 volt power supply kicks out about 200 watts to each sub, or close to the amp's conservative 400 watt rating.
The Lowdown
Designing and building the subwoofer enclosure took a lot of work, requiring several weekends of intense labor. Wayland made the decision to trade off the recessed storage well for use as space for a powerful subwoofer because in the end music was more important to him than the ability to haul a few extra bags of groceries. The family has a Subaru wagon for that. Though there is a small space for a sub enclosure of around 1/3 cubic ft. to the right of the sunken storage bin just under the hatch floor, Wayland wanted something a bit more radical, and enough bass to make the rear view mirror useless; enough bass to loosen his fillings, and challenge the structural rigidity of the car.
He wanted a lot of bass because he planned on using the car as the hybrid ambassador to the world of sound-off competition, and having a trick-looking, high performing sub is a must in that case. When he first looked inside the hatch of an Insight, he didn't see a hidden storage space lid in back. He saw an "in your face subwoofer" location! Other than the obvious destruction of the extra storage space of the sunken well, the sub couldn't interfere with the utility of the car, so that dictated it had to be easily removable for access to the spare tire and jack; have a benign look for everyday use, but the ability to look rad for show; have high SPL; and have a smooth, very deep bass extension down into the sub-20 Hz region. "Boominess" was not to be part of this package, only clean, sine wave quality bass.
Its sound had to blend in with the front speakers and not be overpowering. Per MB Quart's recommendations this pointed to a sealed enclosure design, rather than a ported or bandpass type. Wayland decided on 1/2-inch MDF instead of the thicker and denser 3/4-inch MDF normally used for automotive sub enclosures. This would save weight and help create a bit more interior air volume. Because the box would actually have many steps and shapes to it, by design, these would increase the overall rigidity of the cabinet, helping to make up for the thinner material being used. The main portion of the enclosure is rectangular as looked down on, but is a two-step box as viewed from the side, with the largest portion a deep box where it fills in above the spare tire space, and a shallower box where it rises up and over the raised floor section near the right rear corner. Once Wayland had built the main box section, he made the second part, the "lid." It is both wider and longer than the box it becomes part of, and is also about three inches thick, so he made it hollow to get every inch of interior air space as possible. The painted metal baffle cover was contact cemented to the top surface for a nice cosmetic appearance. An appropriate amount of fiberfill stuffing was added inside the cabinet to smooth out unwanted resonances. Special trunk "spackle" paint was used to finish the outside of the sub enclosure.
The stepped rear lip of the IMA aluminum cover was drilled and fitted with two, 1/4-20 threaded inserts, and the two factory tabs of metal on the rear wall of the car that used to help support the hatch floor compartment lid had their holes fitted with the inserts as well. The completed subwoofer neatly nestles into the hatch floor lid recess like it was meant to be there, and four stainless steel screws spin through holes in the subwoofer (lined with nylon bushings) and securely hold it in place. Wayland fabricated a simple grill cover for the sub out of extra MDF, and routered it to round off the edges before applying black grill cloth. The final touches to car's interior were done with the help of Frankie at Eastside Auto Upholstery. Continuing with the purple against silver & black theme, both front seats were removed, disassembled, and re-stitched to where purple piping divides the factory silver/grey from the black parts of the seats for a trick but factory look. Frankie also custom built front floor mats out of the same carpet material used in the hatch area, but with a tough underside for increased wear and tear resistance, and with matching purple edging around the perimeter.
The rear hatch floor carpet also has purple edging that ties the whole thing together; and along with the embroidered purple "HYBRID" of the amp chamber cover, the look is good enough to hint that it may have come from Honda this way. The completed sytem has a smooth but powerful sound, and with the amp chamber lid shut and the sub grill in place, it all looks clean and tidy and does nothing to detract from the car's outstanding character of being the advanced, clean burning, ultra efficient car that it is. Surely this Insight would be the perfect hybrid ambassador to the sound-off world where, who knows, it could out-perform its gas guzzling counterparts in the judging lanes as easily as it outdoes combustion engine vehicles on the streets. Or so Wayland says.