Copyright 1989 Mike Audleman (73577,3041) Distribution restricted to Model 100 Forum members SPEAKER.DVI Apr 26, 1989 Mike Audleman 73577,3041 What is SPEAKER.DVI? SPEAKER.DVI is a utility to aid an individual in designing the optimum speaker enclosure. The user needs to have the specification sheet commonly provided with the speaker or the specs are sometimes listed in the manufacture's catalog. SPEAKER.DVI will calculate a varieity of boxes with different frequency charastics and the user must choose one that fits their application. SPEAKER.DVI then will step the height or depth through a range entered by the user and show the combinations which will produce the best enclosure. The user must have some knowledge in building speaker cabinets. SPEAKER.DVI will not give "carpentry" information, just the INSIDE dimentions that the user can use to construct the box. What SPEAKER.DVI must know. The information that it must have is usually provided with most quality speakers. The speaker's free air resonance (Fo), equivalent air volume (Vas), Diameter of the speaker (D), and the total Q (Qts) are the information points usually provided and are all SPEAKER.DVI need to perform its calculations. What will SPEAKER.DVI tell me? SPEAKER.DVI will, after entering the required information, calculate the optimum width, depth and height for an array of combinations varying in volume and frequency responce. It will also, if selected by the user, send all results to the printer for a perminant record. The prelimenary information provided is the Q of the box (Qb), the internal volume of the box (Vb), the Q ratio (Qr) between the box Q and the speaker Q, volume ratio (Vr), resonant frequency of the speaker mounted in the box (Fsb), the 3dB low end roll-off frequency (F3dB), and the width, depth, and the height based on the optimum w-d-h ratio. The user needs to select a combination that fits their application based on the roll-off frequency, resonant frequency and possibly size limitations that may be involved in placing the cabinet in a crowded room or on a book shelf. Using SPEAKER.DVI you can sit with a list of specs out of a catalog and run through literally hundreds of calculations that would take hours to do on a calculator. SPEAKER.DVI also plots a graph on the LCD screen showing the ratio of the box volume (Vb) and the 3 dB roll-off frequency so you have a graphic representation of the information provided in numeric form on the CRT or printer. If the printer option is selected, SPEAKER.DVI will try to call XCOPY to dump the LCD to a Radio Shack DMP series printer. If you don't have this program or don't have a DMP printer, you will have to edit the line that loadms and calls XCOPY to call a LCD screen dump program for your printer or simply remove the feature alltogather. XCOPY.CO is created by DMP.DMP and loads into the alternate LCD buffer so it doesn't require a HIMEM setting or protected memory so will work with almost anything in himem. After you choose a combination that fits your application, SPEAKER.DVI will ask wheather you wish to step through Width & Depth (and calculate Height) or Width & Height (and calculate Depth). You are then prompted for the ranges for both Width and Depth or Height depending on which one you select. SPEAKER.DVI will then step through the combinations and point out the ones that will fit the optimum ratio. All the dimentions that are presented in this table will work and their internal volumes are all the same, only the width, depth and height dimentions will change. It will calculate the ratios and display them also. Other options of SPEAKER.DVI are to calculate values for a Ported reflex or an Acoustic suspention enclosure. It will also calculate the width, depth and height based on the optimum ratio for a volume entered by the user. Also, SPEAKER.DVI will calculate the internal volume of an enclosure with dimentions provided by the user. What else will you need besides SPEAKER.DVI? To complete the Ported Bass Reflex enclosure, you will have to use the tables in the Radio Shack book "Building Speaker Systems", catalog # 62-1087 as of this date, listed at $5.95, well worth it if you are serious abot making your own speaker cabinets. If you have any carpenter in you, the book probably will not be needed for the acoustic suspention box but before purchasing any components, material or wood, I highly reccomend that you obtain a copy of the book and read through the construction information. How does SPEAKER.DVI work? The formulas that are in the Radio Shack book have implemented in SPEAKER.DVI using the loops and other conditional statements provided by BASIC. You could design your cabinet without SPEAKER.DVI, but to run through various combinations on a hand calculator would be very cumbersome and time consuming. Also, I developed a formula to compute the optimum W-D-H ratio of a given volume. This formula is not in the book. The ratio provided in the book is 1:.6:1.6. This means that the depth should be .6 times the width and the height should be 1.6 times the width. Deriving the formula: V=Volume,H=Height,D=Depth,W=Width V = W x D x H V = W x .6W x 1.6W V = W x .6W x 1.6W --- -------------- W^3 W x W x W V = 1 x .6 x 1.6 --- W^3 V = .96 W^3 V = W^3 --- .96 ______ 3 / V \ / --- = W \/ .96 D=.6W H=1.6H And is Basic it is: W=(V*.96)^(1/3):D=.6*W:H=1.6*W Since most computers don't have a cube root, simply rase the figure to the 1/3rd power. You are welcome to make modifications to the program. If you do, please make them obvoius and if possible, upload a copy with a changed version number to the Compuserve Model 100 SIG, library 4 (Applications). I do request that you leave my name and number in the program and menus but you may add yours if you like. If you have any recomendations or questions, you may leave E-mail to me on CIS, 73577,3041.