I'd like to have a "decent" audio system but can't afford the stealthbox, PPI amps, MBQuarts front and rear and so on and so on...<p>I bought a CD changer for $230 from www.autotoys.com (great deal) to match the concert radio. A friend of mine will sell me his Rockford Fosgate 150 amp for $75 and I would like to add a JL Audio sub for the trunk. Which style box should I get, bandpass or "regular"? I don't want to wake up the neighbors, do I need a 10" or 12" woofer? Any crossovers required? Lastly, do I "bridge" the amp or not? TIA for any advice, the guys at the audio shop think everyone should spend $2,000+ and keep referring me back to PPI, stealth etc...

I would recommend against bandpass...these designs are specifically made to make the most sound in a narrow frequency range. It may be prejudicial, but I associate bandpass style designs with high school bass-mobiles.<p>So, try to find a good deal on sealed or vented style. I think JLAudio makes a nice powerwedge 10" that would work well. I used to have the 12" with a 12W1...bought for $200 from a local shop brand new (retail was $280). the single 10 with a 10W0 would work well & retailed for $200...should be able to get it for $150 or less...model CS110R-W0.<p>Now for that amp: I am betting it is a two channel amp, so yes, you will bridge it. (the only reason you wouldn't bridge it is if you were going to use a dual voice coil (DVC) sub or you were going to use two subs). Next, ask your friend (or look at it yourself) if it has crossovers installed. I don't know that model (150?), but RF usually has little plug in module lookin things for crossovers...don't worry if it doesn't. For about $15, you can buy FMOD inline passive crossovers. They aren't the fanciest solution, but they are the cheapest & by far the easiest. <p>So, you need power wire to get power to the trunk (use 8ga or bigger...just in case you ever do get the $$ to upgrade) + a short ground cable. Should be less than $20.<p>Follow the FAQ for adding a sub...tapping the wires going to the rear speakers...materials should be less than $20.<p>So totals:<br>Wiring = $40<br>FMOD's= $15<br>Amp = $75<br>sub = $150<br>total less than $300 (less if you already have wires or your amp has a crossover).<p>steve

how are your manual skills?<br>If you are good at wood working etc, you might consider building your own box. It can be a fun and rewarding experience, and may also be cheaper.<p>Another item is the sub itself. While alot of the manufacturer's make good subs, consider that most home speaker woofers cost in the $10-$20 range. Myself I fell very cheated when i buy a single 10" sub for auto use for $300 when i can buy a pair of decent home speakers (with wooden boxes, grills, etc) for $500!! <p>Location, location<br>If you don't have the biggest ground pounder in the world, i find direct sound more efficient. What I mean, is, see if you can have the sub face directly into the passenger compartment. Examples are the ski sack opening, or the rear deck. If the woofer has to pound through the back seat, you loose some dbs here. Also I find with the direct sound approach, you are less likely to rattle the trunk, rear licence plate, licence plate holder, etc. In short, you will not sound like a 17 year old in a ground pounder! The sound should be inside not outside.<p><br>Make sure that your amp is bridgeable!! almost all the new ones are, but some of the older amps are not, or require a minimum 8ohm load in bridged mode.<p><br>1996 a4 2.8 qm

Here's a site that can help you calculate the proper size for your box:<br>http://www.boyte.com/acoustic/design/design.htm

I used it to build boxes around a pair of 61/2" Infinity's that I put in the back of my Xtra-Cab truck. They sound great.

The bandpass design is overly criticised. The original reason for a bandpass design is simple. They provide (if designed correctly) a natural 12dB per octave rolloff on the high end above their tuned frequency without the need for any external crossovers. Unfortunately, they can be complex to build, which leads to high cost. Some speakers are simply incompatible with bandpass designs, and will yield wild results regarding chamber volumes and port lengths. Many improperly designed bandpass enclosures will lead to the above mentioned 'one note bass' problem. A bad design will also lead to a quick and agonizing death for the speaker that it contains. This is due to the fact that the bandpass enclosure is a great distortion hider, therefore you can't tell that the speaker is being terribly overdriven far beyond the limits of its suspension and motor assembly's excursion range. Just thought I'd mention this so that no one passes up a well designed bandpass system because they think they are worthless.<br>