Many times, we get so caught up in the gear, that we overlook some of the things that really need to be considered when planning out a build. Heck, I've been guilty of it myself too. Ever experienced this problem yourself? I'll list out some of the things to consider and potential "gotcha's" that I know of, andhopefully you all can add in some of your own as well.
-Amplifiers are too big to fit in the designated space
-The equipment puts too big of a draw on the stock electrical system in the vehicle
-Power wiring is too small for the current demands of the equipment
-Speaker wiring is to small for the power supplied over their length
-Speaker wire is too big to fit through door grommet spaces
-Amplifiers aren't powerful enough for the inefficient speakers chosen
-Speakers chosen are too large to fit in factory locations (diameter/depth)
-Materials chosen are not a good color/texture match for the interior
-Physical size/weight of the equipment takes up more space than desired
-Incompatible units/special adapters required
After doing several builds in my own vehicles and some for others as well, I've started using a process to help me reduce waste and cost, instead of going into a build willy-nilly flying by the seat of my pants. Here are a few tips to help save you some headaches...
1. Investigate first. Before placing a large order for parts and equipment, make sure that they are compatible. Make sure they FIT. Does your vehicle have a bus system that needs special adapters for that new head unit? When you run power wiring, do you have a grommet location on the firewall? Does it's location require more cable length? Look at the door grommets- Can you fit new wiring through them? If so, what's the max size? Do you have space to mount an inline fuse/circuit breaker near the battery?
2. Measure! Get out the measuring tape and check your physical locations to make sure your amplifiers and speakers can fit in the locations you plan to put them. Make sure you account for the extra space required for speaker/power/RCA wiring connections as well as the materials needed to mount them securely. Make sure your dash has enough depth to fit that new head unit.
3. Check the specs. Do you have a desired output volume you need to reach? If you buy a midrange that has a 10w power rating and is only 80db efficient, you might not get that output you want from the driver before it starts breaking up. Make sure your amplifiers supply enough power for your speakers. Check sensitivity ratings of speakers and efficiency of your amplifiers- especially with vehicles that have weaker electrical systems. Check the length of your power and speaker wiring runs- Do you have a properly sized conductor for the length and power supplied?
4. Visualize and draw/map out the build. This has been very helpful for me to get a design going and ensure I have the space to execute it. Here's a few pics of a layout I recently drew up for a friend who has a Dodge Avenger. He wanted to put 3 Arc SE amps in the trunk and was brainstorming for layout ideas in the space available.
Drawing out the layout helps you to see how it might look and fit in the available space. It also forces you to take into consideration the allowances/space for things like wiring connections and distribution.
5. Plan for future upgrades when available. Allow extra length on power wiring/speaker wiring in case you change the layout or equipment later. Can extra space be allowed for future upgrades to make them easier? When you cut the baffle for your door speakers, can they allow a slightly larger size down the road? When you are fiberglassing pods for your 2.5" midrange speakers, can they be made with a larger baffle to accommodate a 3"-4" driver down the road? In some cases, aesthetics win out and you need an exact fit, but sometimes not. Doing an entire rebuild of a custom piece can be time consuming and expensive. You can often build in a little extra tolerance for changes and still have a beautifully finished product.