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5.8 How do I flatten my system's frequency response curve? [IDB, DK]




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This article is from the Car Audio FAQ, by Ian D. Bjorhovde (ianbjor@mobileaudio.com) with numerous contributions by others.

5.8 How do I flatten my system's frequency response curve? [IDB, DK]


First, you'll need a good quality equalizer - either a 2/3 octave
(15-band) or 1/3 ocatve (30 band) equalizer or a quasi- parametric
equalizer such as PPI's PAR 224 that allows you to choose the center
frequency and bandwidth (Q) of each knob on the EQ. This will allow
adjustments to very specific frequency ranges. Next, you'll need to
get a hold of an RTA (Real Time Analyzer), which is an expensive piece
of equipment that good shops will usually have. The shops can then
equalize the system by making a measurement with the RTA, and varying
the levels on the equalizer in order to make the overall response curve
flat.

Unfortunately, most shops will not do this for free, since proper
equalization can take anywhere from a half hour to many many hours.

Another method involves buying an SPL meter (available from Radio Shack
for between $32 and $60) and a test disc (Autosound 2000 makes one that
runs about $25) that plays discreet frequency ranges - in 1/3 octave
groups. Then, moving through the range of frequencies, SPL
measurements can be taken at each range, and you can plot out a
"response" curve. You'll be able to see what frequency ranges need to
be boosted and which need to be cut. This process will be time
consuming (more so than an RTA, which can analyze the entire frequency
spectrum simultaneously), but should be much less expensive than having
it professionally done.

One last note: While a smooth curve will get the most points at an
auto sound competition, you must NOT rely only on the RTA to tell you
what sounds good. Use the RTA to get a good start, and then use your
(better, use someone experienced in tuning systems) ears to do the
fine-tuning.


 

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