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Loudspeaker Enclosure Designer, v0.5 by David Kakenmaster, 02 April 1992. PLEASE DISTRIBUTE THIS ARCHIVE PACKAGE! IT'S INTENDED TO BE FREE, EX- CEPT FOR REASONABLE COSTS OF DISTRIBUTION (IE DISKETTES, ETC). YOU MAY COPY IT FOR OTHERS, UPLOAD IT TO BULLETIN BOARDS, PASS IT AROUND OR WHAT- EVER. I ASK THAT THE DISTRIBUTED ARCHIVE NOT BE ALTERED IN ANY WAY (UN- LESS YOU ARE ADDING DRIVER DATA FILES - THAT'S OK. DO NOT CORRUPT THE PROGRAMS - THAT'S NOT OK). LAST, KEEP THE ARCHIVE NAME AS LEDV0_5.xxx, WHERE THE x'S REPRESENT THE ARCHIVE COMPRESSION METHOD. IF YOU'VE RE- CEIVED A 'BUM' COPY OF THIS PROGRAM, CONTACT ME AT THE ADDRESS BELOW. I OFFER ABSOLUTELY NO WARRANTIES OF ANY KIND REGARDING THIS PRODUCT. AS DESIGNED AND ORIGINALLY DISTRIBUTED, IT WORKS CORRECTLY. INTRODUCTION - What is 'Loudspeaker Enclosure Designer'? Loudspeaker Enclosure Designer (referred to as LED from now on) is a powerful design tool to aid you in designing enclosures for virtually any bass loudspeaker driver. LED is unusual in the fact that the pro- gram is comprised of a series of Lotus-compatible spreadsheet templates. WHAT??? Spreadsheet templates???!!! Are you kidding???!!!! After the initial shock wears off, think about it... any good loudspeaker design program has accurate modeling, graphics capabilities, a driver database, port design, graph printing, etc... That's all well and good, but can you figure your taxes with it? Can you track your sales record? Can you plan your retirement with it? Can you build a phone directory database from it? Probably not. LED has many of the capabilities of the stand-alone enclosure design programs while still allowing you to use the platform for zillions of other applications. Yep, a spreadsheet! WHY DOES LED EXIST? I've been in the hi-fi business for quite a while now and have seen a great many enclosure design programs. Many are very good, some are outstanding, few of them are easy to use and NONE of them allow you to utilize the program's platform for anything else. Additionally, many are quite expensive. LED is very easy to use and has many of the fea- tures of the most expensive loudspeaker enclosure design programs avail- able while still allowing you to use it's 'platform' for other programs. LED v0.5 is also FREE! Page 1 FEATURES * Ease of use! LED is almost intuitive in it's usage. Many functions are supported by 'hot key' combinations when using As Easy As v5.0 or newer. * Speed. Because a template is loaded in RAM, recalculations are quick since disk accesses are minimized. Many spreadsheet programs access a math co-processor if one is available, further speeding up recalcu- lations. * Graphics. If used with As-Easy-As v5.0 or newer, LED v0.5 has 12 pre- formatted graph functions so you can see how your designs should per- form. All preformatted graphs represent loudspeaker/enclosure behavior between 10 Hz and 1000 Hz. All calculations are from 1 Hz to 1000 Hz, though, so you may adjust the graphs to represent other ranges. * Printing. All graphs can be printed quickly and easily, in either NLQ or draft mode. * Accuracy. The models used in LED are refined versions of those which were originally described by Richard Small and Neville Thiele. * LED supports both sealed and vented enclosure designs. You will be presented with maximally flat alignments, and you may design your own enclosures in any of 4 work areas. * LED supports multiple driver arrays, as well as compound (Isobarik) driver mounting techniques. * Large driver database. LED allows you to store your driver information in seperate files, allowing you to recall any driver to the program quickly and easily. You can also save your design files. * LED has 'in-car' response plotting capability, using a proprietary 'in-car' transfer function. This allows you to accurately simulate the effects of putting your design in a car and measuring it. * LED will calculate ideal internal enclosure dimensions which minimize panel resonances and internal standing waves. * In all ported designs, LED will recommend the minimum port diameter for each port used, so vent noise and power compression will be minimized. LED also calculates the proper port length for you. * Many more features... use LED to discover them all! HARDWARE & SOFTWARE REQUIREMENTS You will need an IBM compatible PC, XT, AT, 386, 486 etc. with at least 180 K of available RAM. You will also need a Lotus-compatible spreadsheet, preferably As-Easy-As version 5.01, from Trius, Inc. This spreadsheet is distributed as Page 2 shareware from many bulletin boards and shareware vendors. It is a superb product with features and performance rivalling most anything out there, shareware or commercial. You should know the basics of operating your spreadsheet program, too. If you cannot find As-Easy-As locally, call Trius, Inc at (508)-794-9377. Your spreadsheet program should be properly configured to your system, ie printer codes and graphics setup. The work areas of LED are set up for 80x25 text mode resolution. Graphs, however will display at the highest resolution your system can support - up to 640x480x16 VGA, if set up for it. NOTE: MANY OF THE HOT-KEY AND GRAPH FUNCTIONS ARE SPECIFIC TO AS-EASY- AS, AND MAY NOT BE RECOGNIZED IN OTHER SPREADSHEET PROGRAMS. HOW TO USE LED v0.5 MAKE BACKUP COPIES OF ALL YOUR LED DISTRIBUTION FILES NOW! IN AS EASY AS, YOU CAN PRESS ALT-H FOR LED v0.5 HOT KEY HELP. 1) Copy (from your backup disk) all the LED files which end in .WKS to the directory where you keep your spreadsheet files. Then start your spreadsheet program. 2) Build your driver database. Retrieve the SPKRDATA.WKS file. This is the blank template for building your driver database. You can enter the 1st driver's name and parameters in the HIGHLIGHTED fields only. When you're through, press ALT-S (Press the ALT key and hold it. Then press the 'S' key.) to save your file. You must name the file; I recommend something like DATxxxx.WKS, where the x's represent the driver's name. You may also want to save your data files in a seperate directory so they're easier to locate. To create another data file, you do not need to retrieve SPKRDATA.WKS again. You can simply type over the existing data you entered before, and save this file with a new name. Keep doing this until you've built up your database to the size you want. NOTE: If you have incomplete or different specifications for your driver, you can 'ballpark' estimate a few of them with the SPKRDATA.WKS file. EXAMPLES: 1) If you have Vas in metric units only, you can enter the value you have in cell F5 (Liters) or cell F6 (Meters^3). The converted English value will appear in cell H5 or H6. Enter the converted value into cell B6. 2) If the only Q value you have is Qts, you can estimate Qms via the following chart: Qms=3.000 if your driver's voice coil former is made from a con- ductive material like aluminum. Qms=7.000 if your driver's voice coil former is made from a NON- conductive material, like paper or Kapton. Page 3 Qms=4.000 if you're not sure of the voice coil former's construc- tion. Enter the value you select in cell B8. LED will then calculate an estimated value for Qes in cell H8. Enter this derived Qes value in cell B9. These estimates will help you, but there is no sub- stitute for having the actual values. 3) If you do not have the value for Sd, enter the driver's actual piston diameter (the diameter of the cone plus about a third of the surround) in cell F10. LED will approximate the Sd value for you in cell H10. Enter this value into cell B10. 4) If Xmax is supplied in English units (inches), enter the value in cell F12. Led will provide a metric equivalent in cell H12. En- ter this value in cell B11. You can create as many driver data files as you like. We'll focus on this first one though, as the others will function identically. 3) Retrieve the LEDV0_5.WKS file. It will take a few seconds to load into RAM. Once loaded you will be presented with two screens which describe how to obtain an upgraded version of LED. The third screen you see will have rudimentary instructions for the program, kind of like a crib sheet... 4) Import a driver data file into LEDV0_5 with the ALT-R keys now. High- light the data file to import and press enter. The driver data will load and the first alignments will calculate immediately. LED will beep when these initial calculations are done, indicating that you're ready to proceed with modeling your own enclosures and viewing or printing graphs. Press the F10 key if you'd like to view the max flat alignments graph now. Press enter to return to the work area when you're through. You may alter any of the retrieved driver data without losing your original driver data file. Note that you may enter data in HIGHLIGHTED fields only. 5) Now you can design up to 4 additional enclosures for the current driver, 2 sealed and 2 vented. ALT-1 or ALT-2 will take you to the USER 1 or USER 2 alignment areas where you can use your own box parameters. This should be self explanatory, but note that you can enter data only in the highlighted areas. 6) If you would like to view the optimal internal enclosure dimensions for each alignment, press ALT-E. These dimensions are based on re- ducing internal reflections and standing waves. 7) LED automatically calculates the optimum minimum port diameter for your driver in each vented enclosure design. Press ALT-E to view and work with these port calculations. Here you may change the quantity of ports used, and LED will recalculate the new minimum port diameters based on the new port quantity. This is especially useful if, for example, you have 1.5" tubing but a single 4" port is recommended by LED. Through an iterative process, you can alter the quantity of ports to be used until the calculated diameter of each port matches that of the available tubing. By trying different port quantities, LED will ultimately tell you that you can use 7 each 1.5" diameter ports instead of the single 4" port. As these calculated minimum Page 4 diameters will rarely be exactly the size of your port material, you should use the next higher available diameter, ie if LED recommends the ports be 3.35", you should use 3.5" tubing since that is a com- monly available size. To get an accurate length for the 3.5" port, go back to the design area and 'plug in' the port diameter and quan- tity. LED will recalculate the port length for each port based on the values you input and the box size/tuning. It's a good idea to heed the minimum port area calculations in order to prevent vent noise or power compression. LED offers the flexi- bility to design ports which allow enough air flow for best sound. 8) Experimentation is the key to success with LED. With a little trial and error, you can design some fantastic loudspeaker enclosures! NOTES FOR AUTOSOUND ENCLOSURE DESIGNERS LED has the capability of modifying your response plots to simulate the automotive environment. It is well documented that there is a large rise in low bass output due to the loading effect of the car's interior. While there are many generalizations and rules-of-thumb out there re- garding this loading effect, facts about the actual changes in re- sponse (the transfer function) are few and far between. Fortunately, at Polk we have gone to great lengths to measure and document this transfer function. After measuring a large sample of many types of vehicles, an averaged corrective filter response was derived which gives good and accurate results in most automotive environments. LED can display your design graphs with this same filter characteristic (transfer function) added to the half space (in-room) response curves. The resulting graphs depict the effect of modeling the response as though it were actually being measured in the car. Whenever you se- lect a graph denoting in-car response, this transfer function has been applied. Many graphs in As-Easy-As have already been formatted to display this in-car response, so you can work with automotive enclosure designs quite easily. Whenever you are modeling a driver/enclosure combi- nation which will be used in a car, you should make one of the in-car graphs the default. In this way you can design for the flattest re- sponse in the automotive environment. Read the next section about graphics to learn how to use, view and print these graphs. GRAPHICS - Viewing and printing frequency response graphs. 1) Whenever you retrieve LDSPKR05.WKS, it will default to displaying the half-space (in-room) maximally flat alignments. However, there are a total of 12 preformatted graphs you may view and print. Press ALT-G to bring up the graph menu. Select a graph type and it will become the default until you change graphs again or restart LED. 2) Since the graph names are truncated, a little explanation of their names is in order: Page 5 CORRECTIVE: The in-car transfer function corrective filter by itself. VENTED/ROOM: All three vented alignments, half-space (in-room) response. VENTED/CAR: All three vented alignments, in-car response. SEALED/ROOM: All three sealed alignments, half-space (in-room) response. SEALED/CAR: All three sealed alignments, in-car response. MF S-V/R: Max flat sealed and vented alignments, half-space (in- room) response. This is the default graph at startup. U1-U2 S/R: User 1 and User 2 sealed alignments, half-space response. U1-U2 S/C: User 1 and User 2 sealed alignments, in-car response. U1-U2 V/R: User 1 and User 2 vented alignments, half-space response. U1-U2 V/C: User 1 and User 2 vented alignments, in-car response. U1-U1 S-V/R: User 1 sealed and User 1 vented alignments, half-space. U1-U1 S-V/C: User 1 sealed and User 2 vented alignments, in-car. The pattern should be clear: MF: Maximally flat alignment U1: User 1 U2: User 2 S: Sealed alignment V: Vented alignment R: Half-space (in-room) response C: In-car response 3) To print the current default graph in NLQ mode, press ALT-P. Press ALT-O to print the same graph in draft mode. It's that simple! Graphs will print sideways at 8.25" x 10.75". SAVING YOUR WORK Press ALT-S to save the entire LEDV0_5.WKS template with all your alignment data intact. You will need to assign a name to this file, remembering two things: 1) it's name must be in the format of xxxxxxxx.xxx, where x's represent letters/numbers and 2) this name must not already exist unless you want your files overwritten and lost. NOTES ON DESIGNS IN GENERAL It is not my intention to tell you what boxes to design, but rather to give you some guidelines regarding the modeling process. In this way you can maximize the potential of LED and design the best enclo- sures for your needs. 1) The most predictable and accurate modeling results will be obtained if the selected driver's Qts value falls between 0.200 and 0.700. While results for values outside that range are useful, they are not necessarily as accurate as those falling within that range. Don't worry... most drivers fall comfortably within the range of best accuracy. Remember also that LED is but one tool which will help you design loudspeaker systems. It can provide only the mathematical models of your designs. Often, real world results will differ. If you build a system and do not like the way it performs... well, that's part of learning the art of designing loudspeaker systems! It is hoped that LED will encourage you to develop and improve your speaker Page 6 designing skills. With some practice you'll be able to fully inter- pret and utilize the wealth of information LED can provide. 2) The value for Ql (vented box loss) has been preset in LED v0.5 at Ql=7. This is widely accepted as the box loss value for 'average' size drivers and internal volumes up to about 9 or 10 cubic feet. For box sizes larger than this, the modeled low end response becomes less accurate using LED v0.5. LED version 1.0 has a user adjustable Ql feature, providing you a method to account for losses in large boxes or for 'other-than-average' driver sizes, thus resulting in more accurate models. 3) LED v0.5 can model multiple driver arrays in both normal and compound mounts. To do this requires manually altering the driver's parameters via this chart: # OF DRIVERS MOUNT VALUE ALTERATION (vs 1 driver) 2 normal Sd multiply by 2 Vas multiply by 2 2 compound Vas divide by 2 4 normal Sd multiply by 4 Vas multiply by 4 4 compound Sd multiply by 2 8 normal Sd multiply by 8 Vas multiply by 8 8 compound Sd multiply by 4 Vas multiply by 2 Unless a value is mentioned, it will remain the same as for one driver. Of note, LED version 1.0 has built-in support for inputting the driver quantity and mounting style, making these manual adjust- ments are unneccessary. 4) LED's maximum power handling calculations are peak, based on 'music power'. That is, the power handling limits are based on the driver's excursion limits, NOT it's maximum rated thermal power. If, in any model the power handling figure is higher than the manufacturer's rated limit, go with the rated limit!! Just because a driver's cone can move far enough does not mean that the driver's voice coil can handle the tremendous input power and heat generated by it. That said, LED's calculated peak power levels are based upon frequen- cies at or above Fb in vented boxes, and at or above F-3dB in sealed boxes. 5) Much note is made of the relevance of Qtc value in sealed boxes. This value can be used to describe the sealed alignments, and one can generalize their overall effect on sound: QTC ALIGNMENT EFFECT ON SOUND 0.500 `critically Light bass, though with great extension. Used in damped' many British speaker systems. Page 7 0.577 Bessel Lightish bass with very good extension. Optimum transient response. 'Fast bass' 0.707 Butterworth Maximally flat amplitude vs frequency response. Good transient characteristics and well balanced bass. >=0.800 Chebychev Bass peak which increases with Qtc value. F-3 dB (cutoff) point increases as Qtc also increases. These alignments are used in many mini speakers to give the impression of more bass. 1.000 - A preferred Qtc value for many car subwoofer ap- plications. Since the car environment will boost bass output, a very low half-space cutoff point is not always needed or desirable. 1.200 - Little bass extension and a bass peak of about 2.4 dB. Used in many mini-speakers with small drivers. This gives the impression of more bass than they really have. 6) Many accept that, as far as human hearing is concerned, the F-10 dB point is that at which bass response becomes significantly less audible. While you will perceive a dropoff in bass before that point, you'll still have useable (as far as our hearing is concerned) out- put down to the frequency at which bass response is down by 10 dB. So, if a driver/enclosure combination exhibits an F-3 dB point of 47 Hz and an F-10 dB point of 26 Hz, you'll have diminished but per- ceptable bass down to the lower frequency. 7) It is assumed that your enclosure, when constructed, will have it's walls lined with a 'stuffing' material like dacron or fiberglass. If you do not use any stuffing, add about 5% or 10% to the box volumes as calculated by LED to account for the volumes occupied by the driver, bracing and port (if vented). Finally, to prevent chances of standing waves arising, do not locate the driver in the center of any one enclosure surface. 8) In vented enclosures, you should attempt to keep the port(s) at least 4" to 6" away from the edge of any driver. You may also locate the port(s) on the back of the box. Doing this can also help minimize radiated noises from the port(s), with only a minimum decrease in direct radiated output. 9) You should attempt to read some of the published documents about speaker design. One of the best is 'The Loudspeaker Design Cookbook' by Vance Dickason. It is available from Old Colony Sound Lab in Peterborough, NH. Their phone number is: (603)-924-6371. The more you know about the world of speaker design, the better your design results will be... NOTES ON LED v1.0 You've probably seen references to LED version 1.0 here and there Page 8 throughout this document. This is an enhanced version of LED v0.5. It has all the features of LED v0.5, plus: user adjustable Ql, built- in support for driver configuration (multiple drivers, compound mount) accessed via simple input fields and 30 preformatted graph functions. It uses the same driver database as LED v0.5, so there's no need for re-building. LED v1.0 has many more hot-key functions, too. Ad- ditionally, LED v1.0 calculates data at 5 TIMES as many frequencies as LED v0.5, giving it smoother and more accurate graphs. The USER design work areas are also far more flexible in LED v1.0. There are more enhancements yet... why not get LED v1.0 to use them yourself? If you enjoy using LED v0.5, but wish you had these features, you can obtain LED v1.0 for $20.00. It will be sent to you on a 5.25" dis- kette. If you'd like it on a 3.5" diskette, add $1.00. Please send a check or money order (no cash) to me at the address below. Feel free to include any comments, questions or suggestions for LED. Thanks for your support of LED. I'm not out to get rich, I just want to offer a great program at a price which covers only my time, energy and a little lunch money..... Remit to: David Kakenmaster 890 N. Tabor Ct. Castle Rock, CO 80104-9715 Page 9