Loudspeaker Crossover Design
Environmental Driver Control ™
All Contents Copyright © 1989-2018,
D+S Tech Labs, Inc.
The goal of the loudspeaker designer is to extract the optimum
performance from each driver while blending all drivers to
achieve a flat frequency response and a stable, linear phase
and impedance of the system. Not only are a driver's
frequency response and impedance determined by its construction
and materials but they are also greatly affected by its "environment".
The internal volume of the enclosure, the shape
and dimensions of a tuned port (if any), the amount of
insulation, the mounting of the drivers, the shape and
dimensions of the cabinet baffle, the shape and dimensions of
the driver's frame, the location and orientation of the
drivers on the baffle, the thickness and resonant properties
of the cabinet, etc., are all environmental conditions
affecting overall response and performance. And this doesn't
even include all the room acoustics.
The list goes on ...
There are too many variables affecting the overall response of the
system to mathematically predict end results from theoretical
data. There is only one way to account for ALL variables and
that is to measure the frequency response (SPL) and impedance
of each driver section when they are installed in their final
environment, then blend the sections together using advanced computer
optimizing software. The "final environment" should even
include appropriate placement of the speaker in the intended
listening room, but we can't quite get that close to each customer
on a production basis. So we settle for anechoic measurements.
All D+S speakers are built with the following process:
This is our proprietary EDC™ process for building crossovers
and we do it for every unit made!
Electro-mechanical woofer parameters are measured by the
LMS computer hardware system. The data is imported into
the LEAP computer software system to compute the optimal
cabinet volume and port dimensions for deepest and smoothest
The cabinet is built to completion with insulation and
all drivers and ports installed. Leads for each driver
section (woofer, midrange, tweeter) are hung out the port
for individual measurements.
Using calibrated microphones and an anechoic chamber, full range
high resolution measurements of on-axis SPL and phase sweeps are
made using a computer hardware LMS (Loudspeaker Measurement System).
These sweeps are made for each driver section.
"Near-Field" measurements are made at the woofer cone and/or
at the port for low frequency response.
Full range measurements of impedance and reactive phase are also
made by the LMS system for each driver section.
All SPL and impedance/phase measurement data is imported into
LEAP (a software analysis and optimizing system).
The conjugate networks are optimized to flatten impedance and
phase of each driver section.
The crossover (with conjugate circuits) is optimized to flatten
SPL response to within +/- 2db.
The crossovers are built using the high quality components.
The speaker is tested and sweeps are re-measured with the
crossover connected to each driver section outside of the
enclosure to verify correctness.
Each crossover is then installed and the speaker is fully tested
and broken in.
This process ensures consistent ruler flat response with linear
phase and precise imaging.
No "mass produced" store-bought speaker can ever come close.
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