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Program: TurboBass Express V10 (C) 1983-2019.

O.K. So you would like to design some speaker cabinets for yourself. Easy, I don't expect to turn you into an acoustic engineer, but you may be wondering what all those funny symbols are about, well forget them! The software TurboBass Express allows you to design cabinets for a single transducer (speaker) easily with just 3 parameters from the technical data sheet of the speaker you want to use. Contact the manufacturer to obtain the TS parameters needed to successfully calculate your box. Try Google. Enter the product code of your loudspeaker.  Alternatively CALL THE MANUFACTURE!

Remember that you have just spent a small fortune buying those subs, but to get them working right and to make them respond to your requirements, they will need a box made to the correct size, otherwise you are wasting your time with them. Don't just any old box them TURBOBASS THEM!


A closed-box design is much easier than a vented-box design. There are fewer parameters to worry about, and the final system response is much less sensitive to variations in these parameters. Building a closed box is easier, because constructing and fitting a vent to a cabinet can add several hours to the project construction time, vented boxes also require additional tools. Tuning a vent can be time consuming and may require some test instruments, although it can be well worth the trouble with some drivers, others will give excellent performance in a closed box, and some will function well only this way. To successfully calculate a sealed box for a given loudspeaker the following parameters are needed.

1. Fs (the resonant frequency of the driver)

2. Vas (the volume of air having the same acoustic compliance as the driver

3. Qt (or Q) (total driver Q a measurement of sharpness of resonance


The vented cabinet program uses the formulas developed by D.B Keele,Jr., to find box characteristics that will obtain good performance with a given driver, you will require the following parameters

1. Fs (resonant frequency of the driver)

2. Vas (the volume of air having the same acoustic compliance as the driver)

3. Qt (or Q) (total driver Q, a measurement of sharpness of resonance)

The response obtained by using this program to design vented boxes is known as the FOURTH-ORDER BUTTERWORTH, considered by most designers to be optimum. it is flat, with no peaks or dips, and consequently dose not sound boomy. Once TURBOBASS has calculated the required size of cabinet use the vent diameter program to fine tune your cabinet


The following parameters are required to calculate a vent area.

1. the box frequency calculated by vented box program

2. the total loudspeaker diameter in inches

3. the X-Max, minimum diaphragm excursion in millimetres.

In order to tune the box designed calculated by the vented box program a vent of a specific size must be installed. The vent must have an area large enough not to impede air flow, otherwise vent noises such as whistling and chuffing will be heard. Small considers that maximum air velocity in a vent dose not exceed 5% of the speed of sound, vent noise will not be a problem, nor will constriction of air flow alter the system parameters, Once you have used this program to calculate the required port size, use the port length calculating program to fine tune your cabinet


The following parameters are required to calculate vent length.

1. the box frequency calculated by vented box program

2. the box volume calculated by vented box program

3. the vent area in square inches calculated by vent are program.

Use this program to fine tune the vented cabinet with Small's method. Note that three inch diameter cardboard tubes are readily available from such sources as mailing tubes, carpet rolls, and dry cleaners. However a solid vent is preferable, build the vent with solid wood (MDF) into and as part of your cabinet, this will give far superior results.

Note that internal porting subtracts the internal volume from your box . Mounting the duct on the back of the cabinet or even underneath it, can help attenuate any objectionable noises produced by the vent.

TurboBass Express. It's all about cabinet design to blow your mind! Download TurboBass

Richard H. Small       For more than 40 years, Neville Thiele's and Richard Small's Thiele-Small (TS) parameters have been the de facto criteria for assessing the performance of loudspeakers. Their unified approach analyzes the electromechanical behaviour of a speaker's components and the interaction with each other and with the air inside and outside the speaker cabinet. The resulting equation is mathematically identical to that describing a circuit. Then, sound produced by the speaker can be calculated by a simple circuit analysis. By using the TS parameters in computer models, users could design the loudspeaker/cabinet interface without having to manually build a speaker cabinet.

Richard Small's experience in electronic circuit design for high performance analytical instruments at the Bell & Howell Research Canter in Calif. laid the foundation for his loudspeaker analysis and measurement work at The University of Sydney. Later, he was head of Research at KEF Electronics Ltd. in Maidstone, England. A Senior Member of the IEEE, Dr. Small is a member of the Institution of Engineers Australia. He is a Fellow of the Audio Engineering Society and has received the Society's Publication Award, Silver Medal and Gold Medal. He is a senior principal engineer for Harman/Becker Automotive Systems in Martinsville, Ind.

Neville Thiele worked at EMI Australia Ltd. for 10 years designing consumer audio radio and video equipment, and with the Australian Broadcasting Corporation for 23 years, designing and assessing equipment and systems for sound and television broadcasting. His honours include the Institution of Radio and Electronics Engineers Australia's Norman W.V. Hayes Medals for best papers and its Award of Honour, as well as the Silver Medal of the Audio Engineering Society (AES). He is a member of the Society of Motion Picture and Television Engineers and a Fellow of the Institution of Engineers Australia and the AES Mr. Thiele is an active member of the ITU-R's Australian National Study Group and Standards Australia's committee on digital audio and video. More on TS design.

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