A couple of issues ago, I asked for your suggestions for a new project vehicle. The first couple of suggestions came in, so I wanted to share them with you. Thank for your comments and keep 'em comin' ...
Tyrell writes: I was flipping through the magazine, saw your column and decided to offer my suggestions, which I'm sure have been brought up thousands of times by now. I've been an installer for almost four years now and a fan of car audio for much longer than that. As an installer, I would like to see something like a nice, clean "space-saving" build in something like a Mazda Miata or maybe an old MG-a small car with a killer audio system that doesn't take up all available space. If it's been done, and done well, I would love to see some photos of this.
Joe Zuk from Chicago: I read your quote at the top of "Troubleshooting;" please just don't do an H2. I had a 1995/96 Oldsmobile Silhouette, the one with the Dust Buster front. I found out it was possible with its huge dash to get about four 10" woofers in there. There was clearance under there, but the wiper assembly arm was in the way, which I don't think would be too bad to relocate. Talk about some up-front BASS! As much as I like the fiberglass work with paint, sometimes simple is better or has more class. How about a hardwood interior or Pergo? Some nice wood grain with a light interior could be nice. Just thoughts.
Our old school bus was the Pontiac Transport version, where we built a center console subwoofer cabinet for "bass up front." At the time, I looked at using the acreage on the dash top for a staging array, but we sold off the van instead. In the Escalade school project we added fake hardwood to match the factory fake hardwood, but I haven't done natural wood in a car in 20 years. But Pergo laminate flooring? That stuff is reeeeally hard to form into curves ...
I have an MTX 3002 amp hooked up to a set of Kicker comps. I'm looking into getting a more powerful sub and was thinking about the Boston Acoustic G5. I also want to get a pair of 6 1/2" speakers. I have 3 1/2s in the front and 6 x 9s in the back now. My amp is rated for 300 watts.
I just read the article in your October issue about single-amp solutions, "Why buy three when one will do the job?" So I need a new amp and was wondering what you had in mind for the 3 1/2s, 6 x 9s and the 6 1/2s. How could I run those speakers and the sub I have now?
If you could help me out that would be great.Vincent
A| I agree with the author that there are many benefits, but also one key disadvantage, to single-amp systems. The benefits include: less space required for amplifiers, lower cost to get started and overall simplicity, not to mention flexibility. A system can be as simple as a source unit, maybe an equalizer or processor, the single amp driving a couple sets of speakers and possibly a passive crossover network. Around one thousand bucks will get you a system that, providing it is installed correctly, will put every factory audio system at double the money to shame.
While the industry started out as a pair of speakers with a pair of amplifier channels, somewhere in the mid-1980s the single stereo amp connected to a few hundred speakers was born. I remember looking over Phoenix Gold application guides showing four tweeters, four mids, four woofers, two midbass drivers and 16 individual 8" subs and a single center-channel speaker all connected to ONE stereo amplifier that you could use to arc-weld! That's 31 speakers connected to a stereo amplifier. MTX, another popular brand of the era, also promoted the single-amp system with massive crossover networks that were assembled like sculptures of copper wire and polystyrene.
For enthusiasts wanting a single-amp system using a 2-channel amplifier, you will need to build a crossover (or have one fabricated if you can't find what you need) suited to your sub and full-range speakers. The crossover will have a large value inductor or coil that passes bass to the sub while filtering out higher frequencies and a mixture of inductors and capacitors for each of the 6 x 9s and 6 1/2" speakers to keep low bass from causing damage while letting the mids and highs pass.
The crossover is the key to dividing your power properly and building one is a lost art. I still teach crossover design, but it is becoming a smaller part of the class material. Yet, the chance of you buying a pre-built crossover that is close to exactly what you want is not a simple assignment. Recently, as a lab project, one of my instructors dug a 2-channel amplifier out of the archives and connected a complete system with 2-way components, a pair of 6 x 9s and a pair of 12" subs all through a patched-together selection of capacitors, coils and resistors. The students were impressed that it could be done and work so well!
With external hand-built crossovers, several issues come up, one being "attenuation." Since your tweeters are more sensitive than your woofers, each tweeter will need a pair of resistors wired in a configuration known as an "L pad," which will reduce the output of the tweeters to match your woofers. This is a major key to sonic linearity, but it does result in a small portion of your precious power being turned to heat. That bothers some purists. You are in a particularly tricky spot since you also have a pair of little 3 1/2" speakers, which can't take near the bass or power that the 6 1/2" speakers can handle. Also, they do not come with "bass blockers." So, unless you go for a 6-channel amp that can also handle a sub in mixed mono, you might have to ditch the 3 1/2 inchers, or break out the crossover and attenuator designs.
Another issue is "insertion loss," in which the subwoofer's coil will naturally waste energy due to its resistance. You need to use a large-gauge coil, or you can lose up to 3dB or half of your amplifier power to heat. That is why I always prefer to build and tweak my own crossover networks-it's a fun and rewarding element of the one-amp system.