From: James.Paulson@p0.f3004.n134.z1.fidonet.org (James Paulson)
Newsgroups: k12.chat.senior
Subject: Re: Music with boom
Date: Thu, 21 Jan 93 10:23:02 PDT
Organization: FidoNet node 1:134/3004.0 - The Orion Project, Medicine Hat Alta

On Tue 19-Jan-1993  4:36a, Sunny Aujla wrote:

SA> I just started putting together a
SA> system in my car. The first thhing I got was my Alpine alarm. I'm
SA> currently running an Alpine 7516 deck with a 6 speaker system and 2 subs.
SA> Using Rockford Phosgate amps - the Punch 45 and Punch 150. Man do they
SA> pound! I got 2 10" Alpine subs, although I don't like them very much and
SA> want to switch, any suggestions? I put Boston Accoustic Tweets and
SA> Phosgate mids. I got Pioneer 5 x 7's in the rear. This I want to modify
SA> too. I drive an '85 Laser Turbo XE. Pretty good car. I want to get the
SA> Alpine 11 band Eq, it's the digital-graphic one they made about 2-3 years
SA> ago. It's really incredible man. I'm gonna put a 10 pack in the hatch as
SA> well soon. Well, talk to ya soon James.

If you are displeased with the performance of the Alpine subs, you have to remember that these are not a very stiff sub, therefore the Thiele-Small parameters dictate that this type of sub performs best in a sealed box of approximately 1 cubic foot. The mathematical relationship of this box should be such that there are no standing waves created, ie. don't make the box width, heigth or length any direct relation of each other, such as by making the length exactly twice the width. Sealed boxes produce more 
accurate bass than ported (tuned) boxes, but not as much bass as a ported design. It is a tradeoff. Do you want powerful bass or do you want accurate bass? You can't have both.

The other question is what is the impedance of the sub itself? If they are 4 ohm subs and you've wired them in Parrallel, then you are feeding the Punch 150 (your sub amp I believe) a 2 ohm load for bass. This is a bit dangerous because in actuality impedance could be dropping as low as 1/4 ohm cooking the amp to quick death. If they are in series, your amp is seeing an 8ohm load and in reality the power that you feed the sub is 1/2 of what you normally would into 4 ohms, therefore a maximum of 75 watts to
 both subs, not to each would be all that your sub is seeing.

If you are after more powerful bass, recognizing that you don't get as accurate of bass as if you were to have a sealed sub box, I would recommend a pair of RockFord pro drivers - 10 or 12 inch maximum, of 2 ohms impedance each wired in series, or a pair of 8 ohm subs wired in Parallel. This will allow you to feed a safe 4 ohm load to your amp with lower distortion coming out of the amp itself. The RockFords are optimized to work best in a ported box, and ported box design is done with a nomogram. Port dia
meter, length, and box size are all built around each other. A 4 inch diameter port works best tuned at around 39hz with a 10, around 31hz with a 12. It is this tuned frequency that adds the "punch" to the bass since you get a peak in performance at 39 hz. A 3rd order box (simple ported) would give you the best results - avoid complex 5th and 7th order designs. The other option is a single 4 ohm Pro 12.

12 to 15 inch subs tend to move more slowly than the music coming into them and create phasing problems in the vehicle. Anyone who sells you 15 inch subwoofers to lead you to believe you will get more bass is lying unless they tell you the whole story. I've heard stereos with 4 tens that top over 134db - that is way too much - you can't listen to it that loud. It was on a Laser - the window glass in the back (no kidding) was bulging an inch. The body won't last long if you listen to it like that - it was m
oving all over. (Now I see that you drive a Laser as well - you should have seen it.)

A sealed box produces a "flat" signal from 25 hz to 200 hz whereas a ported box has a "rise" in its response at the tuned frequency. I don't know the dimesnsions of your vehicle enough to predict a good crossover point, but if you send me the largest dimensions in length, width, and height of your vehicle, I will calculate a close crossover point for your bass and others. Set the bass at about 75-90 hz, and the mids/highs at around 150-200 hz.

You have a lot of power in your amps because they are a 2 ohm stable amp and are one of the most durable amps known to humanity (the Punch). The Alpine 3939 is very nice, agreed, yes I want one, yes they are over $1000. I just bought a new electronic crossover and have added a center channel to my system, the next thing would be an Epicenter Bass Enhancer (Audio Control makes these) to enhance bass on music that was recorded earlier than the new bass intensive stuff. It actually creates bass in the music. 
I am not a basshead, I just love to hear super rich music, and subwoofers can do that. They aren't just for boom fans. 

If you listen to Celine Dionne with a subwoofer system in a car, you will agree that it is very listenable and enjoyable. How about Enya? Ever listen to her? Most car audio contestants seem to like Madonna's Immacualate Collection for the fact that its well recorded, popular, and sounds great in a sound off car. Of course there's 2 Unlimited, Marky Mark, etc....they're all fun to listen to as well. Joe Satriani is great.....

Write me back.....there's too much to comment on here in one letter. I have more recommendations for you, but I'll wait to hear back from you.

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