Vortex-15+ (Active Crossover)
15" Coaxial Two Way Design
Embedded Files
Crossover Design:
This updated active crossover for the Vortex-15 was designed to extract the best sound quality I could from the coaxial driver with the more precise controls and flexibility that comes with an active setup. The new crossover make improvements to the overall frequency response due to better a measurement processes during the development state. While tuning this crossover my focus was providing a very smooth sound power while balancing that with the on axis linearity. The decent behavior of this driver make that easy to achieve. There are some very narrow diffraction notches directly on axis which may make it look a little ugly but because they fill in when you move a few degrees off axis they are not noticed in listening. I ended up with a response that trends downwards very slightly as that is where I felt it had the best balance while cycling through my various test tracks.
For this active version of the crossover I did use a lowpass shelf to extend the bass response in the sealed cabinet from ~80Hz to ~55Hz which gives it a much more authoritative low end and extra kick. I can provide filter settings without that boost if you want to use the driver in a different cabinet design.
Even though this is an active crossover there are passive components used as well. A 1st order filter is employed on both drivers. For the high frequency driver the capacitor acts as a form of low frequency protection as well as dropping the level in combination with the series resistor which helps lower hiss on noisier amps/DSPs to more acceptable levels. On the woofer side I am using a 1mH air core in series with the driver. The increasing impedance provided by the inductor as you move upward in frequency provides an obstruction to the back EMF voltages that are generated by the driver while being driven. In some way it can be thought of as an external shorting ring. The benefit is a reduction of odd order harmonics in the midrange of ~5dB when compared to direct wiring the woofer to the amplifier. I used a 15 gauge coil to keep DCR low but it could be an 18 gauge if you want to save a few bucks.
-Optional filter PCB which is compatible with the active Vortex-15+ design-
Suitable Crossover Parts that fit the PCB:
C1(2.2uF) - L1(1.0mH) - R1 (5.1 Ohm) - R2 is not used
Crossover sim with individual driver responses and reverse polarity notch:
Crossover Filter Slopes:
Active Crossover Filters:
Note: The active crossover was developed on a Crown DCi 4|300N, these filter settings may not be compatible with all DSPs due to capability of filter types and numbers of usable filters.
High Frequency:
Highpass Filter - Butterworth 18dB/Octave - 1400Hz
Gain = -1.2dB
PEQ1 - Frequency = 1270Hz - Gain = 3.7dB - Q = 1.5
PEQ2 - Frequency = 1420Hz - Gain = 1.4dB - Q = 8.0
PEQ3 - Frequency = 1850Hz - Gain = -3.4dB - Q = 4.0
PEQ4 - Frequency = 2950Hz - Gain = -3.0dB - Q = 8.0
PEQ5 - Frequency = 5300Hz - Gain = -1.5dB - Q = 8.0
PEQ6 - Frequency = 7900Hz - Gain = -2.8dB - Q = 5.0
PEQ7 - Frequency = 8000Hz - Gain = 0.5dB - Q = 1.0
PEQ8 - Frequency = 15000Hz - Gain = -3.0dB - Q = 1.5
Low Frequency:
Lowpass Filter - Linkwitz-Riley 36dB/Octave - 1300Hz
Gain = -2.1 - Delay = 0.35ms
Low Shelf (1st order) - Frequency = 35Hz - Gain = 12dB
PEQ2 - Frequency = 65Hz - Gain = 4.5dB - Q = 1.2
PEQ3 - Frequency = 720Hz - Gain = -1.8dB - Q = 8.0
PEQ4 - Frequency = 920Hz - Gain = 6.6dB - Q = 4.0
PEQ5 - Frequency = 1080Hz - Gain = -2.4dB - Q = 8.0
PEQ6 - Frequency = 1500Hz - Gain = -6.0dB - Q = 6.0
Vortex-15+ Design Measurements - Active Crossover
Measurements gated at 14ms and blended to diffraction adjusted nearfield woofer response below 250hz.
No Smoothing Applied. Output level adjusted to equal the passive tests.
On Axis SPL & 10 Degrees Off Axis
CTA-2034 Style Spin Data
Harmonic Distortion @ 85, 95, 105, 110 & 115dB/1m - (Measured at 50cm)
110 and 115dB sweeps started at 60Hz to prevent amp clipping due to bass EQ in the active design though there is some clipping still present at the beginning of the 115dB sweep.
Compression at 85/95/105/110/115dB normalized against 75dB:
110 and 115dB sweeps started at 60Hz to prevent amp clipping due to bass EQ in the active design.
Note: some amp clipping was still present at the start of the 115dB sweep which is likely why you see much higher compression there below 90Hz. A Crown DCi 4|300N was used which gives ~300w per channel @ 8 ohms.
Page updated
Google Sites
Report abuse