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thiele-small speaker design applet hewlett packard HP-GL/2 netscape plugin

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overview

The speaker design program which you can access via this page uses Thiele-Small parameters for a speaker, and allows you to calculate various designs. The two primary style of speaker designs handled by the program are horn-loaded cabinets and vented cabinets.

The designs produced may be used to construct high efficiency horn-loaded cabinets for PA and sound-reinforcement use. Horn flares may be conical or exponential. Exponential flares have the best efficiency/distortion tradeoff of all flares. However, conical flares are easy to build. A conical flare is commonly seen as the mid-range cabinet in large PA systems (a Roy box perhaps?). Other flare types (hyperbolic, parabolic) are not implemented.

Hi-fi cabinets would most likely be designed using vented cabinets. As a social consideration, we do not include any design ability for band-pass designs used for cars that go thump-thump-thump. Similarly, closed cabinets are almost always outperformed by vented cabinets, so they have been omitted as well.

N.B. All units used by the program are metric.

To use the program, first enter the speaker parameters using the 'Choose Speaker' option. Next, choose either 'Vented Design' or 'Horn Design' to select features for your design.

If you are doing a horn-loaded design, you then go to the 'Horn Response' section to plot speaker capabilities, horn impedances, and system response.

Note, that for horn designs, the compliance volume (the air volume between the diaphragm and the throat of the horn) affects the high frequency response of the horn. Hence, a real design will show high-end rolloff unless a 'phase-plug' is used. If you specify a compliance volume, you will see high frequency roll-off when plotting the frequency response of horn designs. The compliance volume is specified in cubic metres, so, for example, with a typical 15" driver, the volume displaced by the driver is approximately 4 litres, and the compliance volume is roughly 3 litres, or 0.003 cubic metres.





When doing a horn design, the 'Speaker Limits' graph shows what the defined loudspeaker is capable of when different diaphragm to throat ratios (Sd/St) are used.

Fmin the frequency of simultaneous thermal and displacement limit

Nt the maximum attainable efficiency

fH the upper half-power frequency (3db point at the high-end)

par the 50Hz displacement limited acoustic power rating

Per the 50Hz displacement limited electrical power rating

Pa the thermally limited maximum acoustic power rating

Pin the thermally limited maximum electrical power rating





When doing a vented design, the following definitions are used:

VB the volume of the box in litres

FB the resonant frequency of the box

F3 the low frequency 3 dB point for the response of the speaker in the box

Dv the diameter of the vent (port) in millimetres

Lv the length of the vent in millimetres

PAR the peak acoustic power that may be produced at the speaker displacement limit (Xmax)

PER the electrical power to produce PAR (note, this can be greater or smaller than the speakers thermal capability

RG the system impedance which affects damping (the closer to 0 the better)




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