Manual-8, Fix-lt-with-the-crossover school – Rane AC 24 User Manual

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Manual-8

6. Realtime Analyzer setup:

a. Place the RTA mic on axis, 1 meter away from

the Low driver as shown in Figure 5, Position 1.

b. Set the RTA SPL Filter to C-Weighting.

c. Turn on the Pink Noise.

7. Make sure the Pink Noise Level coming into the crossover is

able to light the red OL indicator.

8. Set SPL

MAX

for each driver (one Output at a time):

a. Depending on the maximum safe SPL rating of your

system, you may want to use ear protection.

b. Place the RTA mic on axis at 1 meter (see Figure 5).

c. UnMUTE the AC 24 Output associated with the driver

you are setting the Limiter for.

d. Slowly increase the LIMIT Threshold until the RTA SPL

meter reads the SPL

MAX

calculated in step 4 for the driver

you are setting the Limiter for.

e. MUTE the associated AC 24 Output.

f. Repeat for each driver.

Method Two: Voltage at the driver.
Method Two uses the voltage at the driver instead of the SPL.

Using voltage is not as desirable as SPL because impedance often

varies with frequencies. Manufacturers provide the maximum

recommended continuous power (P) and Nominal Impedance

(R) ratings for each Driver. The maximum voltage is calculated as

follows:

• V

MAX

= √(P*R)

P = Maximum Power

R = Nominal Impedance

• Calculate V

MAX

for each driver.

• Follow the steps outlined above for setting Limiters using SPL.

Simply substitute volt meter readings for RTA SPL readings.

System calibration is complete!

We highly recommend installing the included security

cover As Soon As Possible!

Fix-lt-With-The-Crossover School

Consider the following (now that you have worked so hard to

accurately set up the crossover). Some maintain that a good active

crossover can work alone like a parametric equalizer in the hands

of an expert. This does require experience, skill, and the right

equipment to back it up (not to mention a licensed set of ears).

Regardless of which school you profess, the absolute importance

and effectiveness of some kind of realtime analyzer in your system

cannot be overstressed! Analyzers in general have come a long

way. An analyzer saves tremendous amounts of time and provide

the absolute consistency, accuracy, and plain old good sound that

few ears on this earth can deliver. You’ll wonder how you man-

aged without one.

39.4"

POSITION 4

POSITION 1

POSITION 2

POSITION 3

(1 meter)

mic

Figure 5. Setting Output Levels with a calibrated mic.

STEP FIVE: Setting Limiters

Each AC 24 Crossover Output has a Limiter. Each Limiter has an

independent Threshold control with a range of 0 dB FS to –64

dB FS. To maintain spectral accuracy, Mid, Hi-Mid and High

Limiters are linked. Linking is accomplished with wired-or con-

trol. These outputs all receive the same gain reduction regardless

of which one initiates limiting. Independent Threshold indicators

show which band is the source of the limit condition. The Low

Output Limiter may operate independently. This is often desir-

able to prevent “pumping” or modulating higher frequencies. If

desired, there is a Low Limit Link switch.

Method One: Driver SPL.
1. Do not change any of the previously calibrated AC 24 Output

Level controls.

2. Do not change any amplifier gain controls.

3. MUTE all AC 24 Outputs.

4. Set all LIMIT controls to –64.

5. Determine the maximum SPL for each driver.

a. Find the manufacturers sensitivity rating

(dB SPL @ 1 watt, @ 1 meter ) = dB SPL

REF

b. Find the manufacturers maximum continuous power

rating (P

MAX

)

c. SPL

MAX

= dB SPL

REF

+ [10*Log(P

MAX

)]

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