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Welcome, all! This new blog is designed to address some of the
many questions I receive regularly from musicians about technical issues. We’ll
cover a variety of topics, and I welcome comments and questions.
First, a quick introduction. I’m Frank, and I am the
founder, owner and president of Studio Sound Electronics. I have
nearly 50 years' experience in amp repair. Although I no longer
repair amplifiers myself, I want to share what knowledge I have gained along the
way. As a bit of background, I earned a bachelor's degree in
electrical engineering in 1970, did graduate course work following that, and
spent 35 years in the telecommunications industry as a senior engineer at
BellSouth and AT&T. During that time, I also began to repair guitar
amplifiers for various music stores in the Louisville, Kentucky area.
I started Studio Sound Electronics in 1997 in order to provide an online source
for technicians and do-it-yourselfers to find the parts they needed to repair
their amps. So, let's get started ...
Taking Care of your PA Horn Drivers
One of the most common equipment failures that we see in the
business is the blown horn driver. The diaphragms in horn drivers are
fragile, but with a little knowledge and care, they can last a long time. Here
are some tips to avoid horn driver failure (and for that matter, sub and woofer
failure as well!)
1. FREQUENT OCCURRENCES OF HARD FEEDBACK
If you go “ouch” after that last squeal, chances are so did your speakers! This
one is compounded by proceeding to use the speakers after they have probably
been damaged. You and/or your sound engineer need to respond very quickly to
out-of-control feedback. Consider adding a feedback suppressor to your
effects rack.
2. IMPROPER BIAMPLIFICATION: CROSSOVER TOO LOW OR HORN
AMP LEVEL TOO HIGH
Always check your speaker specs for the best crossover points. Just look at the
model number of your cabinets, or even the model number of your horn drivers,
and set your electronic crossover to the crossover frequency recommended.
3. NOT ENOUGH SPEAKER SYSTEMS FOR SPL REQUIREMENTS OR
PROPER COVERAGE
Most folks throw “extra watts” at the same speaker complement: add extra
channels of amplification in concert with additional speakers. You can’t ask
your speakers to produce more than their designed limits. If you bought your
PA system intending to play small gigs at small clubs, and suddenly you find
yourself booked for a wedding reception gig in a gymnasium, you need to add more
power amps and speakers. Consider renting equipment to adequately cover the
larger venue.
4. TRYING TO COVER AN OUTDOOR GIG WITH YOUR INDOOR
SYSTEM
Outdoor gigs require at least 12 dB (16X power) more sound output than indoors,
and as much as 20 dB (100X power!) to really do it right. If you are trying to
do an outdoor festival with large crowds, you need a professional sound company.
5. EXCESSIVE EQ
The classic “smile” EQ curve is actually smiling at your speakers imminent
demise! Keep in mind that EQs are best used for cutting, not boosting the
signal. Need more highs? Reduce the bass…Need more lows? Reduce the highs.
6. INCORRECT USE OF COMPRESSORS/LIMITERS
Excessive compression squeezes the life out of your music AND your speakers!
Learn how to use your equipment correctly.
7. NOT ENOUGH AMPLIFIER HEADROOM
Too little power, and amplifier clipping becomes the norm. Clipping spells the
end of not only speakers, but power amplifiers as well. Watch your clip
lights, and adjust the levels to avoid clipping at all costs. If you can’t get
the volume you need without clipping, you are woefully undersized in equipment
-see #3 and #4 above.
8. SUDDEN TRANSIENTS WHILE THE SPEAKERS ARE HOT
Turn-off thumps, plugging/unplugging mics, etc. The power amplifiers should be
the last item of equipment to be turned on, and the first to be turned off.
9. CLIPPING THE SIGNAL BEFORE IT GETS TO THE POWER AMP
Improper mixer gain distribution, line signal too hot, etc.
10. KEEP USING YOUR SPEAKERS AFTER DAMAGING THEM…
And failing to have the crossover parts checked for damage after abusing the
speaker system that way! Let your ears be your guide. If you hear distortion
from any clean inputs, damage has likely occurred.
Use these tips, and you will experience fewer PA equipment
failures.
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