Q First off I'd like to thank you guys for making an awesome magazine. I've been a devoted reader and car audio enthusiast ever since I first heard bass. At 14 I did my first install in the '78 Lincoln my parents bought me. It consisted of a Rockford Fosgate 18" sub, Urban Audio amp and a Walkman tape player connected via a 12' headphone-to-RCA cable. No highs, just bass! Ahhh, the good old days. Ten years and dozens of installs later, the "inner audiophile" is all grown up. Currently I'm stationed in Iraq and hope to be home in a few months. I want to build an SQ competition system. This is what I have in mind: Pioneer AVH-P7500DVD with AVIC-88DVD, XM Radio, Pioneer EQ and the 6-disc CD changer; MB Quarts or Focal highs; Rockford Fosgate amps-T4004, T8004 and a T3000bd; and for subs, two JL Audio 8W0's for midbass up front and three JL Audio 12W7's in the rear. I want to power the audio gear separate from the car's electrical system for a more pure signal. I know I'm going to need a lot of power-the T3000bd alone has a fuse rating of 300 amps! Does this mean I need to install a separate alternator rated at or above the combined amperage? What size/type capacitor and battery do you recommend and how is it wired?
Thank you for your time, your recommendations and any words of wisdom are greatly appreciated.Shane Fields
P.S. Do you know if I can use my GI Bill to come to your school when I get out? I would love the opportunity.
A It's interesting to hear you discussing your plans to build an SQ, or sound quality system. Most enthusiasts are more into big boom and high SPL, but I have always suspected there would be a shift back to high fidelity someday.
First let's talk about your system design-for a sound quality system, you want to incorporate the fewest speaker components possible, and go with the highest quality you can manage. SQ is not about SPL, and the two never occur together unless it is as a compromise to both. My philosophy is to go with the largest, best-sounding speakers that I can to reach a reasonable SPL without multiple anything. For instance, the perfect system would be a pair of big, smooth tweeters, and a pair of 10" woofers-that's it, the traditional 2-way system. The problem is that you usually can't fit a pair of 10" woofers in the door of a car, and locating them in the back will cause a new set of problems. If I were building an interior to support the audio, I would incorporate optimally positioned speakers in the front, just like a good home stereo.
This can work surprisingly well, since a speaker can usually cover two decades of range, which means "times 10 twice." A woofer that can play 20Hz times 10 and times 10 again, will go as high as 2,000Hz (which is 10 X 10 x 20Hz). A big tweeter can often play as low as 2,000Hz and up to 20,000Hz, meaning you can get a 2-way to cover the entire spectrum with a bit of tweaking and hard work. The problem is that if you shift down to a standard car audio 6 1/2" coaxial, you will need a sub, since the midwoofer can only go as low as 100 to 150Hz. Here is where we see the common "2-way plus sub" best compromise system for SQ. It won't play too loud, but the competition rules only measure SPL to a much lower level than an SPL contest. Just getting close to the top of the range is good enough, since the points difference awarded for SPL in a sound quality competition is not a big deal.
The key here is one pair of tweeters, one pair of woofers and a single or at most a dual sub. Each speaker emits waves that will never all arrive at the ear at the same time, so the more speakers you add, the more you mess up the clarity and focus.
Your front-end electronics would be fine, but I wonder about your amplifier choice. I would certainly consider your selection of amps for a car that was meant to peel paint, but I don't think you need that level of sheer power for SQ purposes. With a different amplifier arrangement, you won't need to do much of anything to the charging system.
As for using the GI Bill to come to school, it doesn't really help much for a course that is only 8 to 11 weeks at the max. It is more suited for one- or two-year courses. Regardless, it would be great to help you build your competition ride as a class project! Stay safe, and I hope to see you soon