CBT36K Assembly Manual
Page
56
of 89
11. MORE TESTING:
11.1.
V
ERIFY
S
PEAKON
W
IRING
:
Stand the speaker up on the floor and attach a
speaker cable to the Speakon connector. Use a 9V
battery and perform a polarity test on the mid-bass
drivers by holding the BLACK (-) lead to the
(-) terminal on the battery and the RED (+) lead to
the (+) terminal on the battery. All mid bass drivers
should jump forward. Repeat the test for the
tweeters and verify they all move forward.
NOTE:
For this test you will need a Speakon
connector that is wired with four wires: 1(+) and
1(-) connected to the mid-bass drivers, and 2(+)
and 2(-) connected to the tweeters; it is helpful at
this point to label these so you can easily identify
which pair goes to the mid-bass drivers and which
pair goes to the tweeters.
(Refer to
http://www.n4tze.com/speakonconnectorwiring.pdf
for in-depth Speakon connecting information.)
11.2. R
ATTLE AND
B
UZZ
T
ESTS
:
In this test we are going to sweep a test tone to
check for buzzes and rattles. This will verify that all
the screws are tight and the front panel gasket is
seated properly (See previous “AUDIO
MEASUREMENT TOOLS” section for signal
generator options). You can easily be fooled into
thinking the speaker has a problem because many
objects in a typical room can buzz. Also, if the
CBT36 cabinet is setting on a hard surface, buzz
and rattles can be originating there.
If you use the suggested PC “Audio SweepGen”
signal generator, a suggested generator test setup
is shown at the end of this section in subsection
10.2.3 “Generator Settings.”
11.2.1. Mid-Bass Test:
1)
We will start with the mid-bass drivers
first, connect a signal generator to the
input of a power amplifier and the output
of the power amplifier to the mid-bass
driver line.
2)
A DMM or AC voltmeter can be used
to monitor the drive voltage to the
speaker.
3)
Adjust the amplifier to a low setting
and start a sine wave sweep from 50 Hz
to 1000
Hz, either manually or
automatically as shown in the “Generator
Settings” section that follows.
4)
Increase the volume to a comfortable
level and listen for buzz or rattles in the
cabinet.
5)
If the tone is pure and clear then
increase the level till it is loud and
continue to monitor the sound for any
buzzes or rattles. (Both mid-bass and
tweeter inputs of the system can easily
handle long-term continuous levels up to
15 Vrms.)
6)
If something sounds suspicious, then
switch to manual mode if you are not
there already, and adjust the frequency up
and down slowly till the buzz becomes
most noticeable. Move your ear up and
down the cabinet to pinpoint to location.
Check for any loose screws or
components causing the buzz and tighten
as necessary.
11.2.2.
Tweeter Test:
Once you are satisfied that everything is OK with
the mid-bass drivers, then repeat the test with the
amplifier connected to the tweeter line. First lower
the level before connecting to the tweeter, and set
the generator to a 1000 Hz to 15 kHz sweep and
then repeat the previous steps with the tweeters.
