In the plot below, the same test conditions as above are used but
notch filter is out. As evidenced in the plot, output between
100 and 200Hz is pronounced.
The photos below show how the notch filter can be switched out.
The mounting screw holding spade terminal labelled "000" (left) is
pulled from the connection and tucked under the terminal block hold-down screw (right).
Note wire markers (Brady Bluestreak).
SINUSIODAL SWEEP, 1M, ON-AXIS
The plots 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 6dB. The bass unit notch filter is active. Three plots show same data set, shifted to
show effect of data smoothing (resolution). Purple plot is raw
data from analyzer, blue and red, 1/12 and 1/6 octave smoothing,
NEAR FIELD RESPONSES
The bass horn near-field acoustic response, located in a
corner position, is shown in the plot below. The horn
near-field response, measured at the left side mouth opening (purple) and
right side (red) are shown. The microphone is placed at floor
level, located at the geometric center of each
mouth opening (~4.5" from the wall). The
green plot is the phasor sum (derived by post processing) of both
left and right responses. The two near-field responses are derived
using DFFT on MLS impluse using a rectangular window. Note large dips in response at
145 and 260Hz in summed response consistent with same measured in far-field
The near-field, on-axis, response of the
mid-range horn assembly
(K401+K55V) and the high frequency unit (Electro-Voice T35) are
shown below. The mid-range response is shown below without the
filter (red) and with (blue). The T35 response is also shown
both without filtering (green) and with the filter connected
MID-RANGE AND TWEETER CROSSOVER QUASI-ANECHOIC RESPONSE, 1M
The measurement microphone was placed 1 meter from the center of the
Klipschorn top-section and an MLS impulse applied and
response recorded. The mid-range and HF units were both connected to
the new network. The quasi-anechoic, frequency response for
frequencies >2kHz is shown below. Note the tweeter is wired
180° out-of-phase with respect to the mid-range polarity.
Purple curve is all frequency domain information derived from DFFT, dark and light blue
curves are 1/12 and 1/6 octave smoothing, respectively.
Excess group delay at crossover
between mid-range and HF unit both with
and without the filter. Microphone is located 1 meter from top
section on the mid-range axis. The 4th order band-pass on the
mid and 4th order hi-pass on the tweeter provides well established
acoustic center at the mid-range. Blue curve is the top
section with both drivers operating without a filter. Note the
magnitude of the excess group delay of the midrange is approximately
1.75ms behind the tweeter down to about 1kHz. The magnitude
then increases significantly below this frequency, a typical
observation. Higher order
attenuation rates (6th, 8th, infinite) will not reduce this value.
Active crossovers are required. Excess phase derived from DFFT
of MLS impulse.
QUASI-ANECHOIC RESPONSE, 1M
The quasi-anechoic response of the Klipschorn with the network is
shown below. The red curve is the near-field, phasor sum of
the left and right bass horn mouth responses combined with the
quasi-anechoic response of the top section at 1 meter (the green curve,
which agrees with near-field response, approximates this response).
The quasi-anechoic response of the top section approximates the
response to about 226Hz. The blue curve
represents the phasor summation of the two responses. 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). A -6dB
L-pad is used on the midrange. The bass horn notch filter is
active. No data smoothing, raw data from analyzer is shown.
can be purchased with either the switchable LF notch filter (KS2)
or without (KS1).
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 returned
Please note that designs and components are subject to on-going product
improvements, revisions. Actual devices shipped may differ
somewhat from photos shown.
THE ALTERNATIVE KLIPSCHORN NETWORK (KS1 and KS2 FILTERS)
A three-way crossover network for the Klipschorn loudspeaker
system is described here. The network has been developed by
between computer model simulations using both
simulators and experimentally determined acoustic
responses. The design approach considers
acoustic response limitations of each component and
seeks a network configuration that establishes as near a flat, on-axis,
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
design revisions. Near and far-field impulse, frequency and phase data files
and curves are
generated using CLIO (v. 7.13) acoustic analyzer.
Note regarding acoustic response curves - Real, unsmoothed acoustic
response curves are not pretty (although we like them). We
show them all. The only thing that matters is the acoustic
response, not the predicted response from simulation (we have those
The network consists of two sections, a bass horn filter (below
upper left) and a top section filter. The bass horn filter
section sends low frequency signals to the bass horn whilst the
top section filter sends signals to the midrange and high
frequency drivers. Capacitors and inductors are Janzen
manufactured (Capacitors: polypropylene Cross-Caps, Inductors:
#18 air-core and #15 iron-core). 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.
Midrange horn output can be user modified by switching out
Midrange filter is 4th order band-pass, establishes acoustic
center of mid-range.
High frequency filter is 4th order high-pass.
Bass horn filter is low-pass with notch
filter (user modified, notch
in, notch out).