wjm@whuxk.UUCP (08/31/83)
In response to Joel @ sdcrdcf 's questions about EQ use, I present the
following answers, which appear to be of general interest to the net ...
1) The best way to adjust any equalizer (I'll assume a graphic EQ with 10+
bands in all that follows) is with the aid of either a built-in spectrum
analyzer or one borrowed from an EE lab. One also needs a pink noise source
- many EQ/analyzers have one built in or you can use a test record (the drawback
to using a test record is that any non-linearities in your phono cartridge
get included in the EQ - if you just want to listen to records this is ideal
since the cartridge non-linearities will be EQ'd out but what happens when you
switch to FM or tape?) with pink noise on it - like the Telarc Omnidisk.
The spectrum analyzer will include a calibrated microphone, which you should
put at your primary listening location in the room. Since the microphone
is sensitive to room position, you have two choices a) find the EQ settings
for each general area of interest and record them - of course this means
resetting the EQ each time you want to listen from a different easy chair
or getting the dbx 20/20 at $1300 which stores up to 10 EQ settings in its
memory and can switch between them with its remote control or b) use a
compromise setting - in many rooms (although not all) this works reasonably well.
Generelly, a good octave band graphic equalizer can do a reasonable job of EQ
most rooms. Admittedly, a 1/3 band EQ (much more expensive) can do even better
but a 10 band octave EQ works fairly well.
The key here is good - like any audio equipment, you get what you pay for.
Most of the EQ's I've recommended run around $600 list, so I'm not surprised
that Joel's results with a $140 ADC are disappointing. Frankly, if you have
a limited budget and can only afford $140 for an EQ - I'd skip the EQ and spend
the $140 on better speakers - its more cost effective.
As for friends tweaking your EQ, there are several solutions 1) record the
settings on a piece of paper and file it with the instruction books for your
equipment - this way, you just look up the settings when you recover from the
party and reset the thing 2) hide the EQ on the floor or out of sight (this
has the drawback that you can't enjoy the light show if you have an analyzer
and also you can't eq records to your tastes) 3) spend the $1300 for a dbx 20/20
which can reset itself automatically when the appropriate button on the
remote control is pressed.
2) Compensating for poor mixing is a subjective thing - there are no "right"
answers here - you just move the appropriate sliders to emphasize the freqency
bands you feel are out of kilter. You can move instruments around the room
since you have independent control of the left and right channels for each band.
Effectively, you have a separate balance control for each band.
3) What Joel said is true - room compensation is basically static (unless
you get new furniture, carpeting, or drapes) while recording compensation varys
with the recording. However, since this system is linear, that old friend of
us EE's, the superposition theorem comes to our aid. You record the settings
for room EQ, and then use them as the baseline for your recording EQ. (A more
convenient but expensive option is to get two EQ's one for room EQ with a
spectrum analyzer which you set and forget, and another (spectrum analyzer
not needed here) to tweak to compensate recordings.
Happy EQ Bill Mitchell
Bell Laboratories
Whippany, NJ