STK Professional Audio SPM-122AP, Руководство пользователя, Страница: 6 / 12

6
Placement Tips
*Avoid placing loudspeaker into the corners of a room.
This increases the low-frequency output and can cause
the sound to be muddy and indistinct.
*Avoid placing loudspeakers against a wall.
This ,too, increases the low frequency output, through
not as much as corner placement. However, if you do
need to reinforce the low frequencies, this is a good way
to do it.
*Avoid placing the active speakers directly on a hollow
stage floor. A hollow stage can resonate at certain
frequencies, causing peaks and dips in the frequency
response of the room. It's better to place the active
speakers on a sturdy table or tripod stands.
*Position the active speakers so the high frequency
drivers are two to four feet above ear level for the
audience(make allowances for a standing/dancing in the
aisles audience).
High frequencies are highly directional and tend to be
absorbed much easier than lower frequencies.
By providing direct line-of-sight from the active speakers
to the audience, you increase the overall brightness
and intelligibility of the wound system.
*High reverberant rooms, like many gymnasiums and
auditoriums, are a nightmare for sound system
intelligibility.
Multiple reflections off the hard walls, ceiling, and floor
play havoc with the sound.
Depending on the situation, you may be able to take
some steps to minimize the reflections, such as putting
carpeting on the floors, closing draperies to cover large
glass windows, or hanging tapestries or other materials
on the walls to absorb some of the sound.
*However, in most cases, these remedies are not
possible or practical. So what do you do?
Making the sound system louder generally doesn't work
because the reflections become louder, too.
The best approach is to provide as much direct sound
coverage to the audience as possible.
The farther away you are from the speaker, the more
prominent will be the reflected sound.
*Use more speakers strategically placed so they are
closer to the back of the audience.
If the distance between the front and back speaker is
more than about 100 feet, you should use a delay
processor to time-align the sound. (Since sound travels
about foot per millisecond, it takes about 1/10 of a
second to travel 100 feet)
HUM
*Turn the LEVEL control all the way down.
If the noise disappears, it's coming from the signal
source. If not, try disconnecting the cable connected to
the INPUT jack. If the noise disappears, it could be a
"ground loop", rather than a problem with the active
speakers.
Try some of the following troubleshooting ideas:
*Use balanced connections throughout your system for
the best noise rejection.
*Whenever possible, plug all the audio equipment's line
cords into outlets which share a common ground.
The distance between the outlets and the common
ground should be as short as possible.
*The hum may appear when using an unbalanced
source(consumer preamps, CD player, VCR, etc.).
This is caused by the unbalanced-to-balanced interface
between the devices(and exacerbated by the fact that
most consumer audio equipment have a two-wire line
cord, without the third-pin safety ground).
Use an interconnect cable wired as shown below.
The important point is that the shield and wire from the
XLR pin 3 are jointed at the RCA(source)end.
*The baluns are threaded at one end(75 ohm) to fit TV
coax cable and have two wires at the other end
(300ohm). They will not affect the video quality.
*If the hum persists, try removing components one at a
time from the back of the mixer or preamplifier, and
check for hum each time(turn off your equipment before
you undo any connections).
It is fairly common to find more than one problem.
*If your preamp or mixer are the only things connected
to the active speaker and the hum is still there,
try different connection cable, or move the preamp/mixer
to another location.
Placement Tips & Hum