We asked custom electronics (CE) pros about the blunders they encounter when DIYers or inexperienced pros can’t get their systems to work.

Here are some of the rookie mistakes you should avoid:
Buying the least expensive gear and finding out it doesn’t have the features you need, like discrete control codes (on and off, for example) or enough inputs and outputs.

Hooking up equipment using substandard cables, connectors and adapters, leading to poor performance and, eventually, no performance.

Underutilizing gear that you already have. For example, connecting the DVD player using composite cable when it has component or HDMI outputs, and not setting the TV to the maximum resolution.

Never realizing you could be watching HD channels you’re paying for: “You mean Channel 4 is standard but 404 is HD?!  I never knew!” 

Compromising setups that you learn to live with, like having to leave a cabinet door open, or moving cables from one device to another.

Forgetting to install Ethernet jacks at the A/V locations.

Skimping on power protection. 

Mounting video devices in poor locations: displays too high and projectors not centered correctly when there’s no lens shift available.

Failing to wire distributed audio speaker locations for stereo.

Forgetting to put power where it’s needed: racks, TVs, projectors, powered seats.

Trying to use “rules of thumb” for speaker locations in unusual rooms, such as those with missing walls or angled seating.

Wiring low-voltage cabling parallel with the electrical, often done in retrofit situations when the installer or DIYer simply uses the same holes used by the electrical wires.

Inadequate ventilation for equipment, resulting in burned-out gear (and calls to the manufacturer for their “faulty” products).

For plenty more tips on potential pitfalls, check out the “What I’d Do Differently Thread” on the AVS Forum. Our custom installers also offer these stories from experience:

One DIYer mounted his old 42-inch plasma into a recessed niche. He then framed in the niche, drywalled and finished the wall, for that “built-in, framed-out look.” 
The problem, of course, is that he walled up his TV.  He said that he wanted to see only the picture and nothing else, completely ignoring the fact that the TV had no ventilation and no access for service/repairs.
He continued to show that his equipment— receiver, cable box and subwoofer— was also installed and placed behind the wall, explaining, “I’m using an RF remote, I don’t need to see my equipment.”
I could not believe what I was hearing and seeing!  We ended up selling him a new and properly designed home theater, and sure enough, when we tore the wall apart, there was all of his equipment and subwoofer. —Matthew Menck, Superior Home Theater

I once had a client who used commercial audio (70-volt system) was used in a residential distributed audio system. The original homeowners took key equipment when they moved, and the new homeowner thought he could just put regular residential equipment in its place. —Rob Schultz, Inspired Electronics

Contributors: Morgan Harman, The Tech Source; Isaac Imig, Gorge Audio/Video; Rob Schultz, Inspired Electronics; Sam Johnson, Pro Home Systems; Raff Sanchez, B-Sun Media Systems LA