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By Anthony Grimani April 4,2012
Expecting the Worst and Hoping for
the Best from Installed Systems
Anthony Grimani (firstname.lastname@example.org) is
president of Performance Media Industries,
with offices in Novato and San Anselmo, CA.
It happened again. I went to configure
and calibrate a home theater and ran
into a quagmire of unexpected issues
that caused a failure of the system. One
issue wasn’t immediately detectable,
and one progressed like a list of bad
coincidences from an NTSB airplane
crash investigation report.
I have run into speakers with a little
fleck of metal stuck on the voice coil at
the edge of the gap that started scraping
only at high levels and sounded like
absolute dread. I have seen connectors
with one little stray strand of wire barely
shorting between signal and ground–
worked fine at low levels but causing
more trouble at high levels. I have seen
XLR connectors wired every which way,
passing signal out of phase and 6dB
down in level. I have seen signal ground voltages on products hooked to
the same power strip but floating 100mV away from each other, resulting
in unrecoverable hum.
is obvious after a few
minutes; sometimes it
takes four hours to find
the root cause.
Every one of these little issues has taken down a system in one way
or another. Sometimes you still get sound and picture–albeit at reduced
quality–and sometimes the system doesn’t work at all. But in just about
every case the client was unhappy and withholding final payment. The
integrator’s staff diligently tried and tried to find the problem and fix it,
but in many cases it was like the proverbial needle in a haystack.
Problems like these often challenge even my engineering experience
and abilities. I usually show up with two or three large cases full of test
equipment, and at some point along the way, I am chasing aspirin with
gulps of coffee while scratching my head and reading the display of my
oscilloscope with incredulous disbelief. “What now?!” “No, don’t do this
to me!” “Wow, I really don’t know what the heck is up here!” I even
spout the ubiquitous “Maybe we should just reboot the system,” in hopes
of a magic solution. I test this and measure that. I bypass products, run
different cables, swap channels, and verify power line voltage conditions.
Sometimes the problem is obvious after a few minutes; sometimes it takes
four hours to find the root cause. More often than not, it is a $2 part that
is affecting the entire ecosystem of the AV signal.
The fact is that it takes deep knowledge of electrical engineering,
audio systems, video systems, power supply systems, and control systems
to detect, troubleshoot, and fix the inevitable problems that arise when
you have systems with dozens of interconnections, interface compatibility
issues, and unpredictable behavior. The technical staff available to many
integrators can’t necessarily be expected to have that knowledge base or
experience. But you can expect that these little bugs will cost you a ton of
money: delays, product swaps, staff time, truck rolls, and the inevitable
withholding of payment by your client. At the worst time in a project–
when you are spending a bunch of resources to fix problems–you are held
hostage by cash flow shortages.
How to Avoid the Problem?
My first suggestion to help avoid problems like these is to establish
relationships with skilled and competent consulting AV engineers. You really
want someone with a degree in electrical engineering. You want someone
who has spent time doing “bench tech” work at some electronics company,
and someone who has many years of field troubleshooting experience. I
suggest hiring them to do verification and commissioning of each and every
system you put together. There is always a problem lurking, and you don’t
want your client to be the one to find it. I have now been in front of about
300 systems, and I have not found one that passed all the tests. There are
too many parts and pieces at work to ever expect perfection the first time.
So do yourself a favor; when it comes to home theater and AV system
debugging and tuning, expect the worst while hoping for the best.
Hire the right engineering
talent, and read up on the
Chase Walton contributed
to this column.