NOTCH FILTER
The LF notch filter on the KV2 version of the network can be activated and de-activated by the user. Spade terminal labeled "000" is pulled from the corresponding connection, left photo and tucked under the terminal block screw, right photo (to enlarge, click on photo).
The LF notch filter on the KV2 version of the network can be activated and de-activated by the user. Spade terminal labeled "000" is pulled from the corresponding connection, left photo and tucked under the terminal block screw, right photo (to enlarge, click on photo).
QUASI-ANECHOIC RESPONSE
The quasi-anechoic response of the V-Trac Klipschorn with the network is shown below (red plot). The green curve is the phasor sum of the left and right bass horn mouth responses combined with the quasi-anechoic response of the top section at 1.3 meter. The quasi-anechoic response of the V-Trac approximates the response to about 235Hz. The blue curve represents the response of the midrange horn. The purple represents the CP-25. The near-field bass horn response was corrected to account for both measurement distance and the ratio of mouth areas between the mid-range horn (102 sq. in.) and bass horn (693 sq. in). An -8dB L-pad is used on the midrange. The bass horn notch filter is active. No data smoothing, raw data from analyzer shown.
The quasi-anechoic response of the V-Trac Klipschorn with the network is shown below (red plot). The green curve is the phasor sum of the left and right bass horn mouth responses combined with the quasi-anechoic response of the top section at 1.3 meter. The quasi-anechoic response of the V-Trac approximates the response to about 235Hz. The blue curve represents the response of the midrange horn. The purple represents the CP-25. The near-field bass horn response was corrected to account for both measurement distance and the ratio of mouth areas between the mid-range horn (102 sq. in.) and bass horn (693 sq. in). An -8dB L-pad is used on the midrange. The bass horn notch filter is active. No data smoothing, raw data from analyzer shown.
ACOUSTIC RESPONSES
The Klipschorn bass unit acoustic response, located in a corner position, is shown in the plot below. The horn responses, measured at the left side mouth opening (purple) and right side (red) are shown. The microphone is placed in the geometric center of each respective mouth opening (19.5" from the floor, 4.5" from the wall). The green plot is the phasor sum (derived by post processing) of both left and right responses. The two responses are derived using DFFT on MLS impulse using a rectangular window.
The on-axis response of the V-Trac horn loaded with the BMS driver is shown below (green). The response of the Beyma CP-25 tweeter is also provided (purple). The responses derived using DFFT on MLS impulse using a rectangular window. Microphone placed at mouth.
MID-RANGE AND TWEETER CROSSOVER QUASI-ANECHOIC RESPONSE
The measurement microphone was placed 1.3 meters from the center of the V-Trac horn mouth section and an MLS impulse applied and response recorded. The mid-range and HF units were both connected to the network. The quasi-anechoic, frequency response for frequencies >1kHz is shown below. Purple curve is mid horn response, green is high frequency response and blue is total response. Frequency domain information derived from DFFT of MLS impulse. Red plot is excess phase determined by subtracting numerically derived minimum phase response from total phase measured.
CUMULATIVE SPECTRAL DECAY
The Cumulative Spectral Decay (CSD) plot of the V-Trac response shown above is provided and shown in the plot, top. Below is the CSD of the current production Klipschorn midrange (K55/K401) and high frequency unit (K77). Both systems operating with 4th order bandpass, 4th order high pass filters. Decay shown is over entire length of impulse response (4.1ms). As evidenced in a comparison of the two, decay rates are higher and exhibit better uniformity in the V-Trac system with no particular frequency demonstrating excessive overhang. Note also the exceptionally smooth decay at the V-Trac crossover frequency (~4500Hz). The data demonstrates that the V-Trac system exhibits better transient behavior.
EXCESS GROUP DELAY
Excess group delay plots provide a quantitative assessment of the time dispersive characteristics of a multi-way loudspeaker system. For example, if a loudspeaker system is claimed to be "time coherent" what that implies is a flat excess group delay plot across the useful bandwidth of the system. Here, for comparison purposes, we provide excess group delay plots of both the V-Trac with the KV1 network (red) and a stock Klipschorn operating with a A-type network (green). The KV1 is a 4th order band-pass on the MID and 4th order hi-pass on the HF. The A-type utilizes a first order high pass on both the stock Klipsch MID and HF units. As is evident in the plot comparing the two, the magnitude of the excess group delay errors associated with the A-type network are considerable and are responsible for distortion. The KV1 network evidences less phase error resulting in better imaging and enhanced stereophonic effect. Excess phase derived from DFFT of MLS impulse.
The Klipschorn bass unit acoustic response, located in a corner position, is shown in the plot below. The horn responses, measured at the left side mouth opening (purple) and right side (red) are shown. The microphone is placed in the geometric center of each respective mouth opening (19.5" from the floor, 4.5" from the wall). The green plot is the phasor sum (derived by post processing) of both left and right responses. The two responses are derived using DFFT on MLS impulse using a rectangular window.
The on-axis response of the V-Trac horn loaded with the BMS driver is shown below (green). The response of the Beyma CP-25 tweeter is also provided (purple). The responses derived using DFFT on MLS impulse using a rectangular window. Microphone placed at mouth.
MID-RANGE AND TWEETER CROSSOVER QUASI-ANECHOIC RESPONSE
The measurement microphone was placed 1.3 meters from the center of the V-Trac horn mouth section and an MLS impulse applied and response recorded. The mid-range and HF units were both connected to the network. The quasi-anechoic, frequency response for frequencies >1kHz is shown below. Purple curve is mid horn response, green is high frequency response and blue is total response. Frequency domain information derived from DFFT of MLS impulse. Red plot is excess phase determined by subtracting numerically derived minimum phase response from total phase measured.
CUMULATIVE SPECTRAL DECAY
The Cumulative Spectral Decay (CSD) plot of the V-Trac response shown above is provided and shown in the plot, top. Below is the CSD of the current production Klipschorn midrange (K55/K401) and high frequency unit (K77). Both systems operating with 4th order bandpass, 4th order high pass filters. Decay shown is over entire length of impulse response (4.1ms). As evidenced in a comparison of the two, decay rates are higher and exhibit better uniformity in the V-Trac system with no particular frequency demonstrating excessive overhang. Note also the exceptionally smooth decay at the V-Trac crossover frequency (~4500Hz). The data demonstrates that the V-Trac system exhibits better transient behavior.
EXCESS GROUP DELAY
Excess group delay plots provide a quantitative assessment of the time dispersive characteristics of a multi-way loudspeaker system. For example, if a loudspeaker system is claimed to be "time coherent" what that implies is a flat excess group delay plot across the useful bandwidth of the system. Here, for comparison purposes, we provide excess group delay plots of both the V-Trac with the KV1 network (red) and a stock Klipschorn operating with a A-type network (green). The KV1 is a 4th order band-pass on the MID and 4th order hi-pass on the HF. The A-type utilizes a first order high pass on both the stock Klipsch MID and HF units. As is evident in the plot comparing the two, the magnitude of the excess group delay errors associated with the A-type network are considerable and are responsible for distortion. The KV1 network evidences less phase error resulting in better imaging and enhanced stereophonic effect. Excess phase derived from DFFT of MLS impulse.
SWEPT SINUSOIDAL, 1M, ON-AXIS
The plot below are the frequency response of a corner loaded factory Klipschorn (SN 18W290) with the network. The response is with the microphone position about 1m away from the front face of the top section of the cabinet. The microphone is aligned directly on the axis of the mid-range horn mouth. The input signal is a sinusoidal sweep with data collection in a reverberant environment. The mid-range horn in this measurement has been attenuated by 10dB. Red plot shows effect of bass unit notch filter disconnected, blue is active notch filter. As is evident in the plot, the notch filter contributes to improved frequency response linearity within the 100-300Hz mid-bass region of the bass horn. Plots are 1/12 octave averaged. Compare to factory measured response of stock Klipschorn bass unit (ref. J. AES, v.48, no.10, Oct. 2000).
In the plot below, the
effect of data averaging of the swept sinusoidal response is shown.
Same test conditions as above are used. The notch filter is active.
Blue is 1/3 octave smoothing, red is 1/12 octave smoothing and green
is resolution limit of analyzer (=1/48 octave).
The plot below are the frequency response of a corner loaded factory Klipschorn (SN 18W290) with the network. The response is with the microphone position about 1m away from the front face of the top section of the cabinet. The microphone is aligned directly on the axis of the mid-range horn mouth. The input signal is a sinusoidal sweep with data collection in a reverberant environment. The mid-range horn in this measurement has been attenuated by 10dB. Red plot shows effect of bass unit notch filter disconnected, blue is active notch filter. As is evident in the plot, the notch filter contributes to improved frequency response linearity within the 100-300Hz mid-bass region of the bass horn. Plots are 1/12 octave averaged. Compare to factory measured response of stock Klipschorn bass unit (ref. J. AES, v.48, no.10, Oct. 2000).
In the plot below, the
effect of data averaging of the swept sinusoidal response is shown.
Same test conditions as above are used. The notch filter is active.
Blue is 1/3 octave smoothing, red is 1/12 octave smoothing and green
is resolution limit of analyzer (=1/48 octave).
PURCHASE
The KV1 and KV2 can be purchased directly from North Reading Engineering as part of a complete midrange and tweeter horn upgrade package for the Klipschorn.
KV1 $1050/pr.
KV2 $1450/pr.
Shipping networks shipped from US postal zip code 01864. For estimation purposes, KV1 (pair) shipping wt. approx. 25lbs, KV2 (pair) 32lbs. For US customers we use FedEx Ground. Full refund within 30 days of receipt. Customer pays shipping back to North Reading Engineering. Units must be unaltered. Please note that designs and components are subject to on-going improvements and revisions. The actual devices shipped may differ somewhat from photos shown.
The KV1 and KV2 can be purchased directly from North Reading Engineering as part of a complete midrange and tweeter horn upgrade package for the Klipschorn.
KV1 $1050/pr.
KV2 $1450/pr.
Shipping networks shipped from US postal zip code 01864. For estimation purposes, KV1 (pair) shipping wt. approx. 25lbs, KV2 (pair) 32lbs. For US customers we use FedEx Ground. Full refund within 30 days of receipt. Customer pays shipping back to North Reading Engineering. Units must be unaltered. Please note that designs and components are subject to on-going improvements and revisions. The actual devices shipped may differ somewhat from photos shown.
THE V-TRAC KLIPSCHORN NETWORK (KV1 & KV2)
A three-way crossover network for the V-Trac modified Klipschorn loudspeaker system has been developed and is described here. The V-Trac consists of a large format wood construction tractrix horn manufactured by Greg Roberts at Volti Audio. It is driven by the BMS ND4562 MID neodymium, 2" throat, polyester diaphragm, compression driver. High frequency content is handled by the Beyma CP-25. The network has been developed by extensive iteration between computer model simulations using both LTSPICE and MATLAB simulators and experimentally determined acoustic responses. The design approach considers the acoustic response limitations of each component and seeks a network configuration that establishes as near a flat, on-axis, near-field, frequency response as is possible within the design practice allowances for useable bandwidth, phase distortion, physical size, part count and cost. Network simulations are terminated with loads that accurately capture both impedance magnitude and phase information of the bass, mid and high frequency horns providing accurate predictions of purpose specific design revisions. Near and far-field impulse, frequency and phase data files and curves are generated using CLIO (v.7.3 and 10.31) acoustic analyzer.
Note regarding acoustic response curves - Real, unsmoothed acoustic response curves are not always pretty and are almost never shown simply because the data likely fails to substantiate the performance claims made by the manufacturer. We have characterized, in great detail, the acoustic response of this system. We have used computer simulation to develop the crossover network. The computer models were then calibrated to the actual acoustic response measurements. This provides us with a powerful tool to refine the networks and establish the desired acoustic response. The only thing that matters is the acoustic response of the system. We have refrained from showing the predicted response from simulation software because predictions have no value to the end user. That said, all claims are substantiated with performance data.
DESCRIPTION
The KV1 consists of two sections, a bass horn filter and a V-Trac filter. The bass horn filter section sends low frequency signals to the Klipschorn folded bass unit whilst the top section filter sends signals to the BMS midrange and Beyma high frequency drivers. Capacitors and inductors are Janzen manufactured (Capacitors: polypropylene Cross-Caps, Inductors: #18 air-core and #15 iron-core). Additional we have incorporated one design feature found on the current factory network, a large notch filter in the bass horn section. We have however, altered the shape of the response to suit our design requirements. The filter with the LF notch filter is designated the KV2.
HIGHLIGHTS
Midrange horn output level user modified by switching out L-pads.
Midrange filter is 4th order band-pass, establishes well-defined acoustic center of mid-range.
High frequency filter is 4th order high-pass.
Bass horn filter is low-pass available either without the notch filter (KV1) or with (KV2).
A singe KV2 network is shown below. The low frequency filter section (left) is shown with notch filter.
A three-way crossover network for the V-Trac modified Klipschorn loudspeaker system has been developed and is described here. The V-Trac consists of a large format wood construction tractrix horn manufactured by Greg Roberts at Volti Audio. It is driven by the BMS ND4562 MID neodymium, 2" throat, polyester diaphragm, compression driver. High frequency content is handled by the Beyma CP-25. The network has been developed by extensive iteration between computer model simulations using both LTSPICE and MATLAB simulators and experimentally determined acoustic responses. The design approach considers the acoustic response limitations of each component and seeks a network configuration that establishes as near a flat, on-axis, near-field, frequency response as is possible within the design practice allowances for useable bandwidth, phase distortion, physical size, part count and cost. Network simulations are terminated with loads that accurately capture both impedance magnitude and phase information of the bass, mid and high frequency horns providing accurate predictions of purpose specific design revisions. Near and far-field impulse, frequency and phase data files and curves are generated using CLIO (v.7.3 and 10.31) acoustic analyzer.
Note regarding acoustic response curves - Real, unsmoothed acoustic response curves are not always pretty and are almost never shown simply because the data likely fails to substantiate the performance claims made by the manufacturer. We have characterized, in great detail, the acoustic response of this system. We have used computer simulation to develop the crossover network. The computer models were then calibrated to the actual acoustic response measurements. This provides us with a powerful tool to refine the networks and establish the desired acoustic response. The only thing that matters is the acoustic response of the system. We have refrained from showing the predicted response from simulation software because predictions have no value to the end user. That said, all claims are substantiated with performance data.
DESCRIPTION
The KV1 consists of two sections, a bass horn filter and a V-Trac filter. The bass horn filter section sends low frequency signals to the Klipschorn folded bass unit whilst the top section filter sends signals to the BMS midrange and Beyma high frequency drivers. Capacitors and inductors are Janzen manufactured (Capacitors: polypropylene Cross-Caps, Inductors: #18 air-core and #15 iron-core). Additional we have incorporated one design feature found on the current factory network, a large notch filter in the bass horn section. We have however, altered the shape of the response to suit our design requirements. The filter with the LF notch filter is designated the KV2.
HIGHLIGHTS
Midrange horn output level user modified by switching out L-pads.
Midrange filter is 4th order band-pass, establishes well-defined acoustic center of mid-range.
High frequency filter is 4th order high-pass.
Bass horn filter is low-pass available either without the notch filter (KV1) or with (KV2).
A singe KV2 network is shown below. The low frequency filter section (left) is shown with notch filter.
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