Kicker Technical Tips
Page 30
Dr. K: What about this business of gain matching?
Greg: Glad you asked Dr. K!
The trouble is most competitors by-pass this stage of setup, compromising the signal to noise ratio of their
system. The result: poor dynamics, linearity, and sometimes noise. It’s too easy to pass up, “so just gain it”.
You can use an oscilloscope to set gains, or use the CD104 disc from Autosound 2000 with an inexpensive
Radio Shack amplified speaker (part#277-1008). The later system is explained in detail in the notes from the
disc. It is quick, cheap, and effective. After you have completed this sequence listen to the results. Chances
are your system will improve dramatically. Tracks 25-29 on CD102 are also helpful. Listen to the overall spec-
tral balance at this point. You may make subtle changes to the gain to improve spectral balance. For exam-
ple, if the top end of the system sounds ”hot” from the crossover frequency up, you may reduce the out-
put of the tweeter amp instead of shelving the entire top-end of the EQ later. Just make sure that you do
not take it too far, reducing the overall dynamic range. By having a 3-to-1 gain ratio, you have the luxury of
some adjustment for the benefit of spectral balance. The instructions for this procedure are included with
the disc. Try track 4 on CD104 and watch your scores soar.
(Greg takes a drink and there is a short pause.)
At this point a good competition car should begin to take shape, and you have not even touched the EQs
yet. You can look at the overall curve on a RTA, but your ears should be the final judge. Here is a cool trick
that may save your bacon at a critical time: Once your gain structure is set, document it. Pick a frequency in
the middle of each passband on the 104 disc, then set your head unit for a moderate volume and docu-
ment it using the digital readout on the deck or measure it with a volt meter. Measure each section, at the
amp’s speaker outputs, sub, mid-bass, etc with a voltmeter set for AC., and write it down. In the event that
you ever have an amp failure or tear the system down, you can now set it back in a jiffy, even if it is in the
lanes.
Dr K: Hey look the food has arrived.
( He has secretly switched the brand of coffee Greg usually drinks with Folgers instant, with flavor crystals.
Let’s see if he notices.)
Greg: Now that’s great coffee!
Dr. K: I cannot slide anything past you, Greg.
( They both enjoy a big laugh.)
Dr.K: Excellent Greg. Now what about those EQs. Are we ready to adjust them yet?
Greg: Easy big fella. Remember, stick to the procedure!
Now is a good time to go through the IASCA setup disc and use tracks 2-4 to evaluate the system’s relative
polarity. This track is more effective than the simple in-phase / out-of-phase track on the judging disc, as it
is repeated at three frequencies. Use the liner notes, you may have to reverse the polarity on a sub, mid-
bass, or midrange to improve staging and imaging. For more detailed instructions, reference the articles on
polarity vs. phase in the tech briefs and read the liner notes of the IASCA setup discs.
Dr.K: (getting anxious) Surely we can adjust the EQ, now?
Greg: That’s right, now you finally get to put your paws on the EQs. I hope you have at least a pair of one
third octave EQs. For those that are new to the game I recommend that you use tracks 33-60 on the IASCA
setup disc. Listen to the tracks on that set of headphones that you just bought. This is good ear training. It
takes a passage of music, adding boost and cut at several different frequencies. After you have become
familiarized with it, you will find it to be a quick way to get a car in the ballpark. Most novice tuners tend to
boost EQs, with some experience it tends to go more the other way around.
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