PLACEMENT OF LARGE MONITOR SPEAKERS
The closer a speaker is to the walls, ceiling or floor the more bass it
produces.
A speaker in the middle of a room radiates low frequencies in
in all directions (into ' full space' ).
If the speaker is placed against a
wall the low frequency energy is concentrated into half the space, which
boosts the lows by 3 db.
Putting a speaker in a corner maximises bass
output into 1/4 the space. Highs aren't much affected by speaker
placement because they radiate mainly out front.
One way to prevent rear wall reflections is to flush mount the monitors
in the wall. They should be isolated by foam rubber, fiberglass or rubber
shock mounts. If flush mounting is impractical, wall reflections can be
weakened by placing the speakers at least 3ft from the rear wall and
4ft from the side walls.
(LEDE) Live End Dead End arrangement is where the front
half of the control room around the speakers is made very sound
absorbent (dead) by applying muslin covered fiberglass or acoustic foam to
the walls and ceiling. The wall behind the engineer is hard and
reflective to provide ambience and increase loudness. This surface is
broken up to diffuse the sound.
Reflection Phase Gratings are often used
for this purpose.
LEDE rooms are not always absorbent in the front and reflective in the
rear. The speakers can be flush mounted in a hard wall array that is
angled to eliminate early reflections. The idea is to create a reflection
free zone at the mixing position.
Many control rooms can be improved by putting thick material on the
walls behind and to the sides of the speakers or by pulling the speakers
out from the wall at least 2ft.
Some of the claimed benefits of an LEDE
control room are :
- Mixes are easier and faster to do because you hear more of the sound from the studio and less from the control room.
- The overall sound is clearer.
- Stereo image and depth is improved greatly.
- Frequency responce is flatter.
- Boom and ringing is reduced and transient responce is sharpened.
In any control room the speakers are mounted at ear height or slightly
higher. For best stereo imaging align the speaker drivers vertically and
mount the speakers symmetrically with respect to the side walls. Place
the two speakers as far apart as you're sitting from them (about 8ft) ; aim
them towards you and sit exactly between them.
Wire the speakers in the same polarity to obtain a sharp centre image. For
both channels,connect the amp positive terminal (+ or red) to the speaker
positve (+ or red).
Polarity adjustment is also called speaker phasing.
To determine whether a speaker is wired in correct absolute polarity :
1. Produce a kick drum sound (standard polarity microphone or drum
machine)
2. The speaker cone should go out the instant the drum is
struck.
Reverse the leads of both speakers if the opposite occurs.
To adjust the stereo balance,play a mono signal and assign it to
channels 1 and 2 at the console. Adjust the faders so that the signal
reads the same on VU meters. Then while sitting exactly between the
speakers the sound image should be localised midway between the
monitors. If necessary center the image by adjusting the left or right
volume control on the power amp.
Listening level during mixdown should be maintained at about 85 db SPL.
The Fletcher Munson effect says that you hear less bass in a program
that is played quietly. If you mix while monitoring at say 100 db SPL, the
same program sounds weak in the bass when heard at a lower listening
level. Therefore programs meant to be heard at 85db should be mixed and
monitored at that level.
Play a musical program at 0 VU and adjust the level to obtain an
average reading of 85 db on the sound level meter. Mark monitor setting.
To avoid losing power from heating the speaker cables put the power
amps close to the speakers and use short cables with thick
conducters. The low resistance of these cables allows maximum damping of
the speaker by the power amp. Use following -
Less than 25ft cable length - No.16 gauge.
25 - 50ft - No.14
50 - 100ft - No.12
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