Crown-audio I-Tech 4x3500HD Bedienungsanleitung PDF herunterladen (Seite 57)

I-Tech HD DriveCore Series Power Ampliers

Operation Manual

page 57

constant regardless of whether the LevelMAX Limiter suite is enabled

(ON) or bypassed (OFF).

14.6 LevelMAX RMS Limiter

LevelMAX RMS limiting accurately limits the output signal to the

speciﬁed RMS threshold voltage.

14.7 RMS Threshold (VRMS)

The RMS Threshold should be set by the user to correspond to the

short term (2 hour) power handling of the transducer or system.

Refer to the appropriate JBL Speciﬁcation Sheet, Technical Manual or

Product Manual for two hour power ratings. To calculate the RMS

Threshold in VRMS, use the following equation:

where AES Power (Wrms, 2 hour) is the free air component power

rating.

If minimum impedance data is unavailable, use nominal impedance. If

2 hour AES power ratings are unavailable, use 2 hour IEC power

ratings. For most applications, it is recommended to operate LevelMAX

limiters in Auto mode so that peak thresholds are automatically

calculated based on the RMS threshold and selected LP frequency

(see 14.1).

14 LevelMAX Limiters

14.1 LevelMAX Peak Limiter

LevelMAX Peak limiting instantaneously limits the output voltage to

not exceed the deﬁned peak threshold voltage.

14.2 Peak Limiter Threshold (V

)

In Auto mode, the peak limiter threshold value is automatically

determined from the deﬁned RMS threshold and the low pass

frequency deﬁned in the XOVER block. For a low pass frequency less

than 100 Hz, the RMS to peak threshold ratio is 6 dB. From 100 Hz to

400 Hz, the RMS to peak ratio increases from 6 dB to 9 dB. Above 400

Hz, the ratio remains at 9 dB.

For Advanced and Manual modes, the peak limiter threshold can be set

by the user.

14.3 Peak Limiter Attack (sec)

The peak limiter attack time is instantaneous and cannot be modiﬁed.

The output voltage is limited to the value deﬁned by the peak limiter

threshold (see 14.1).

14.4 Peak Limiter Release (sec)

In Auto mode, the peak limiter release time is determined by the high

pass frequency deﬁned in the XOVER block.

For Advanced and Manual modes, the peak limiter release time can be

set by the user.

14.5 Peak Limiter Look-Ahead

Peak Limiter Look-Ahead inserts a delay into the peak limiter signal

path in order to ‘look’ at the input signal and anticipate when the peak

threshold will be exceeded. If it detects that the threshold will be

exceeded, the signal is gradually reduced prior to reaching the

threshold, while still limiting to the correct peak voltage. This approach

eliminates a sharp signal discontinuity which, in turn, could create

audible distortion.

The peak limiter look-ahead value is 0.5 ms. This value was determined

to be subjectively acceptable for most frequency ranges while not

adversely compromising overall latency. Overall latency remains

14.8 LevelMAX Transducer Thermal Limiter

LevelMAX Transducer Thermal limiting is designed to protect

transducers from long term thermal damage by gradually adjusting the

RMS threshold until the target long term thermal threshold voltage has

been reached. The thermal limiter functions only when the RMS limiter

is enabled and when the thermal voltage threshold is lower than the

RMS threshold. On the main limiter panel, the thermal protection LED

turns on once the thermal limiter is 0.75 dB into limit.

14.9 Thermal Voltage (V

RMS

)

The thermal voltage threshold should be set to correspond to the long

term (100 hour) power handling of the transducer or system.

Refer to the appropriate JBL Speciﬁcation Sheet, Technical Manual or

Product Manual for 100 hour power ratings. To calculate the Thermal

Voltage Threshold in VRMS, use the following equation:

where Power (Wrms, 100 hour) is the 100 hour power rating.

If 100 hour power handling data is unavailable, set 100 hour power

rating ≈ 0.8 x 2 hour power rating.

14.10 Thermal Response Time (s)

The thermal response time is the amount of time the average RMS

signal is above the thermal threshold voltage before limiting begins.

Once the threshold has been exceeded for the amount of time deﬁned

by the thermal response time, the RMS threshold is lowered until the

target thermal voltage has been reached. The thermal response time is

not the time it takes to reach the target voltage, although the longer the

thermal response time, the longer it takes to reach the target voltage. It

is also dependent on the amount of gain reduction and the ratio

between RMS and thermal thresholds.

Thermal response time is transducer-dependent and should be based

on the initial temperature rise of the transducer voice coil to protect it

from thermal overload.

If detailed transducer data is unavailable, the Thermal Response Time

should be left at the default value of 10 sec.

)(Impedance Nominal)hour100,(Power)(ThresholdThermal ohmsxWrmsVrms �

)(Impedance Minimum)hour2,(PowerAES)(ThresholdRMS ohmsxWrmsVrms �

1 2 ... 52 53 54 55 56 57 58 59 60 61 62 ... 71 72

Kommentare zu diesen Handbüchern

Keine Kommentare

Crown-audio I-Tech 4x3500HD Bedienungsanleitung Seite 57

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Empfänger und Verstärker Crown-audio I-Tech 4x3500HD