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INTERACTIVE CROSSOVER DESIGN - XO_LEFT AND XO_RIGHT
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XO_LEFT and XO_RIGHT: DRIVER LOAD
Usage: XO_LEFT|XO_RIGHT N0 N1 value|impedance.zma|response.frd [Rseries]
Examples: XO_LEFT 0 3 RL=6 RS=5 * 6 ohm load with Rs=5 ohm protect, connected to nodes 0 (ground)and 3
XO_RIGHT 5 6 RL="impedance.zma" RS=5 * Z load from file, 5 ohm protect, connected to nodes 5 and 6
XO_RIGHT 0 1 RL="response.frd" * Test signal response by file (no Znom or protection)
value|impedance.zma|response.frd (must select one)
- A numeric value will be interpreted as a resistive crossover load connected between
nodes N0 and N1. The driver protection circuit can also be specified
- If an impedance and phase angle (*.ZMA) file is specified the Z and P
data from the file is used to calculate the complex impedance connected to
output nodes N0 and N1. Values that are not directly available
from the table will be interpolated from values that are in the table.
The driver protection circuit can also be specified
- If a frequency response and phase degree (*.FRD) file is specified the response
and phase data from the file is used to create a filtered test signal. Node
connections are ignored but are required to prevent hanging nodes during the
SPICE deck analysis. The protection circuit in this case has no meaning
since since the output is generated directly
[Rseries] (optional driver protection circuit)
- The electrical effects of a driver protection circuit built from a series
resistor and multiple back to back diode clamps is reverse calculated from
the desired load impedance making the protection circuit 'invisible' during
test. When making this circuit be sure to have a high enough R value to
protect your amplifier and enough diode drops in the circuit to get a suitable
drive voltage before the signal is clipped.
- Care should be taken when calculating the resistor wattage and safe diode current.
Keep in mind that typical silicon switching diodes will have ~0.7V drop each. For
example, if 4 diodes are in series (in each direction) this will result in ~2.8V peak
voltage accross the load or 1W maximum (0.5W rms) into an 8 ohm load. Use fewer
diodes for a lower limiting voltage and power.
ICD CIRCUIT EXAMPLE
The following example shows two crossover loads defined using ZMA impedance
files. In this case the tweeter and woofer loads are defined using ZMA file
complex impedance data to modify the SPICE generated test signals. For quick
analysis, resistive loads can also be specified. Additionaly, an FFT defined
response can be specified using the FRD format.
An additional option is the use of a driver protection
circuit. When this simple resistor and diode clamp circuit is used,
the interaction of the series resistor, crossover and driver load are all taken
into account when generating the test signal. The result is a reasonably well
protected driver should an amplifier or human error occur.
******************************************************************
* 1st order high/low pass crossover
*
* (1) C1 4uF (2)
* +----------------||-----------+
* | |
* | L1 2mH |
* +------/\/\-----+ (3) |
* | | |
* Vsig + Z=woofer.zma Z=tweeter.ZMA
* - | | (external protection here!)
* | | |
* /// /// ///
*
******************************************************************
Vsig 1 0 AC 1 * Input signal
C1 1 2 4uF * High pass capacitor
L1 1 3 2mH * Low pass inductor
XO_RIGHT 2 0 "tweeter.zma" 5.0 * Five_ohm+diode clamp protection
XO_LEFT 3 0 "woofer.zma" * No protection (direct connect)
******************************************************************
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Copyright 2007, Smith & Larson Audio |
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