For free demo download of LspCAD, contact IJDATA

note: The latest information and files for LspCAD and LspCAD PRO can be found at http://www.ijdata.com


LspCAD is a software package that helps you to construct and simulate loudspeaker boxes and passive crossover networks.  The name LspCAD is short for Loudspeaker Computer Aided Design.

LspCAD  includes both a box and a crossover modeling utility of exceptional power.

The box utility

The software package provides support for modeling 9 different kinds of loudspeaker boxes with dynamic loudspeaker units. These are:

Closed box.

Bass reflex.

Double tuned bass reflex. Two types.

ABR (passive radiator).

Four types of bandpass boxes 1, 2, 3 and 4.

LspCAD has a powerful tool for modeling room response and cabinet diffraction effects to help you create good sounding loudspeaker systems. Moreover it is possible to simulated flared basseflex ports i.e. ports with a larger cross sectional area at the ends.

Measured SPL data can be imported and merged together with the simulated data. Supported file formats are among other LAUD and LEAP.

See below a screendump showing what the desktop may look like when working with the box utility.

The data plot diagrams in LspCAD are in windows which you can re-scale or minimize allowing you to concentrate on the information that is most important at each point in the design. The available diagrams are:


Frequency- and phaseresponse "on axis". Shows also acoustic contribution from ports and loudspeaker units.

Cone excursion.

Air speed in ports.

Impedance response with phase.

Group delay.

Impulse-, step- or toneburst response.


Most of the diagrams can be exported in a number of formats. All diagrams can be printed out individually or in group.


The data is entered through dialogs, most of the dialogs are non-modal i.e. they can be left open on the screen. Also one can resize the large dialogs and scroll through them so that only the properties that is the most interesting for the moment needs to take up precious space on the screen.

The passive crossover utility

The crossover utility can model 2-way and 3-way loudspeaker systems with one or two loudspeaker units per network.

Besides the rudimentary filter calculator existing in most loudspeaker modeling software the user can import measured SPL and impedance data and thus model a real system.

The filter parameters are easily computed and controlled from the dialogs, one for each network. One important thing to note here is that one can enter the internal DC-resistance of the inductors, a feature that is important in order to achieve accurate simulation results.

A filter schematic, which can be printed out shows the looks of the crossover.

The available diagrams are:

A unique feature called Filter music allows you to filter a music sample through the loudspeakers frequency response (both magnitude and phase) and listen to the result with a pair of high quality headphones, thus you can get a pretty good idea of how the complete loudspeaker sounds without even having to put together the crossover unit!

All diagrams can be exported in a number of formats. All diagrams can be printed out individually or in group (vertical off axis response, surface plot can not be printed in group).

The advanced passive crossover utility

The advanced crossover utility gives you the opportunity to construct advanced passive crossover networks.  

Up to four-way systems of any configuration with up to four different driver units is each network is possible to model, this gives you the opportunity to construct very complex systems. The program is very simple to use, constructing a 3 way system with 4th order slopes takes about 1h starting from scratch.

A built in easy-to-use network optimizer makes it really easy to optimize filters with up to 24dB/octave slope. A wizard function helps you with the first attempt to create a filter.

The active crossover utility

The active crossover utility gives you the option to create active crossover networks with common OP amplifiers. Besides the common filter links, things such as treble and bass rise circuits and notch filters are possible to implement.  The optimization possibilities of the advanced passive crossover utility exist here too.

For more power, check out LspCAD PRO

For Demos or free upgrades for owners of LspCAD: see http://hem1.passagen.se/ijdata/lspcad.html

LspCAD was developed by Ingemar Johannson in Sweden.