1. An Introduction to MacSpeakerz, The Speaker Design Toolbox.
MacSpeakerz is a computer aided design (CAD) application for the Macintosh computer which allows the user to design loudspeaker subsystems with optimized response characteristics. Because MacSpeakerz was written specifically for the Macintosh, it takes full advantage of the friendly Macintosh interface. It can show you Frequency, Excursion, Impedance, Phase and Group Delay Responses of any combination of loudspeaker driver and enclosure that you specify.
A large library with over 700 loudspeaker drivers is provided with the MacSpeakerz program including Audio Concepts, Carbonneau, Celestion, Credence, Dynaudio, EV, Focal, Fane, Gauss, JBL, KEF, Fostex, MTX, Panasonic, Precision, Ramsdell, TAD, Yamaha and more. However, you can easily expand the library to include new drivers.
Engineers will be pleased to know that MacSpeakerz employs the mathematical models of Thiele and Small for both vented and closed box type loudspeaker subsystems. These models are readily traceable to the published literature on loudspeaker design. A bibliography of the engineering papers is included for use by technical types.
One of the nicest things about MacSpeakerz is that it's very easy to use. Anyone who wants to build their own speakers can use it to build an optimum enclosure on the first try.
About the MacSpeakerz Demo
This Demo version of MacSpeakerz allows the user to explore all the features of MacSpeakerz,
but only for one driver, the Nordschow-Wright NW1800. You can model various enclosures for this driver in closed or vented boxes and plot the responses on the screen.
When using the Demo version the user will not be able to utilize the Open Subsystem or
the Open Driver commands. Of course MacSpeakerz normally can analyze a complete
library of drivers and recall the user's SubSystem files.
Demo Quick Start
Closed Box Evaluation
• Launch the MacSpeakerz Demo Disk.
• Notice that the driver you will be evaluating is loaded in the Driver and
Subsystem Parameters window, the Nordschow-Wright NW1800.
• Activate the Box Parameters window by clicking on it once or use the left/right
scroll keys to activate the windows.
• Activate the VB, (Box Volume), field by clicking on it. Try a box volume of 2 cu ft
followed by Return. (Or use the Box Calculators under the Box Menu (at top) to design
your enclosure).
• Notice that the Qtc (Closed Box Q) has been calculated.
Note: You can also approach your enclosure design by entering a Qtc (Closed Box Q),
and the corresponding VB (Box Volume) will be calculated. Try the Butterworth
alignment of .707 in the Qtc field, followed by return. This alignment will give you
the flattest and most extended Frequency Response.
• Do a command F from the keyboard.
• Check out the Frequency Response curve!
• Store it in memory 1 by doing a command1.
• Note that under m at the right side of the Response window a 1 has been displayed
to indicate that you have information stored for that memory.
• Look under the Box Menu and open the Box Dimensions window.
• There are three recommended enclosure dimensions to choose from which have good
side to side ratios. Close window when done. (use a command W from the keyboard)
Continue for Vented Box Evaluation
Vented Box Evaluation
• If you want to design a vented enclosure, enter the frequency that you want to tune
the box to, 40 Hz for example, in the Box Freq field, FB, followed by return.
• Notice that the minimum recommended vent area, Sv MIN, has been calculated.
• Do a command F from the keyboard to see what the curve will look like tuned to 40 Hz.
• Experiment with various frequencies until you find the curve that you want.
• Store the selected response in memory 2 by doing a command 2.
• Do a command E from the keyboard to clear the Response window and recall memory 1,
the closed box, by typing 1 from the keyboard. The Box Parameters window will be
refreshed with the contents of the selected memory. Now recall memory 2, the vented
box, by typing 2.
• Now choose a vent(s) from under the Vent menu.
The vent length has been calculated in the Lv field. The length listed will be per vent.
A vent which gives you a negative number would not be feasible.
• Print your report by doing a command P.
The print command will allow the user to print a normal report for the Nordschow-Wright NW1800 driver. Included in the printout is an expanded listing of the parameters shown in the Driver Parameters window, the contents of the Box Parameters window, the Subsystem parameters, and the recommended Enclosure Dimensions.
Additional information:
• The On/Off status of each response is shown under the Analysis menu by the checkmark
at the left of the menu item. Only those responses that are selected are actually
calculated.
• You have two choices for the Frequency Response. You can choose between 0 dB Mode
and dB SPL Mode which can tell you the dB SPL (loudness) of the proposed system.
2. The MacSpeakerz Windows:
The program starts up with three windows open on the desktop.
The Response Window
This is the top window where the predicted Frequency, Excursion, Impedance, Phase and Group Delay Responses will be displayed. It normally shares the screen with the Driver Parameters and Box Parameters windows below but you can use the top window's zoom box (upper right corner) to allow the Response window to fill the entire screen for increased resolution.
The Driver Parameters Window
The bottom left window displays an abbreviated list of the parameters of the driver currently loaded. The complete list of driver parameters is shown in the Driver Editor window.
The Box Parameters Window
The bottom right window is where you describe the box you want MacSpeakerz to analyze. A complete box description consists of two parameters:
1. Box Volume, V(B)
2. Box Resonance Frequency, F(B)
(F(B) = 0 for closed box)
Note: The term "subsystem" is used in this manual to mean a loudspeaker driver (such as a woofer) in combination with its enclosure. This is to distinguish between a complete full range loudspeaker system and the subsystems which comprise it.
Once the Box Parameters have been finalized, the vent can be designed using the Vent Surface Area, S(v), and Vent Length, L(v), fields. Make sure that the Box Volume, V(B), and Box Frequency, F(B), fields contain the values you want to use because these are used in the vent calculations. To determine the vent dimensions you enter a surface area for the vent opening in the S(v) field, press Return, and the length of the required vent will be calculated and displayed in the L(v) field. If L(v) turns out to be a negative number, then the vent is not feasible and the vent area will have to be increased or the box frequency lowered.
The Minimum Recommended Vent Area, S(v)MIN, is displayed in the Box Parameters window. This is the smallest vent that will be free from vent noise. In practice, it seems that vents as small as half this area can be used without excessive vent noise. Vent noise can be evaluated by driving the completed box at the box frequency near maximum amplitude and listening for a "whooshing" sound.
Another way to design the vent is to choose one of the commonly used tube configurations from the Vent menu. The surface area of the vents you select will be calculated and loaded into the S(v) field. The required vent length will also be calculated and displayed in the L(v) field. The vent length given in the L(v) field will be per vent. If you choose four 2" diameter vents, the length listed would be the length of one 2" vent.
Isobarik Enclosures
MacSpeakerz can model isobarik (sometimes called "compound") enclosures. Enter "1" for the number of drivers in the Number of Drivers field. Next, divide the V(as) of the driver by two and enter this new value as the V(as) of the new compound driver. For a given frequency response, the isobarik configuration results in an enclosure of half the volume compared to using a single driver. (The default value in the V(as) field cannot be changed in this demo version)
3. The MacSpeakerz Menus:
Following are detailed descriptions of each menu command. Commands are arranged in the same order as they appear across the menu bar on the screen.
3.1 About MacSpeakerz
(under the apple menu)
This command brings up a window with information about MacSpeakerz including the current date, time, and free memory. The window remains on the screen until you click the mouse again.
3.2 The File Menu Commands:
The File menu is the first menu to the right of the apple menu. The commands under the File menu are as follows:
New Subsystem
Selecting New Subsystem clears all subsystem and driver edit fields as well as clearing the contents of all 10 memories. The Response window title reverts to "Untitled Subsystem" until a new subsystem is loaded or a new subsystem name is entered from the Subsystem Editor window. (from the keyboard use command N)
Open Subsystem...
Brings up a standard Macintosh file dialog window and allows you to load a previously saved Subsystem file. (Disabled on the Demo version).
Save Subsystem
Saves the current Subsystem file. (from the keyboard use command S)
Save Subsystem As...
Brings up a standard Macintosh file dialog window and allows the current Subsystem file to be saved under a new name or to a different disk.
New Driver
Clears all Driver edit fields. Select New Driver before entering the parameters for a new driver to assure that all the parameters of the previous driver are cleared.
Open Driver...
In a fully functional version of MacSpeakerz it brings up a standard Macintosh file dialog window and allows a Driver file from the Driver Library to be loaded. For the Demo version, it brings up the Demo window.
Save Driver
Saves the current Driver file.
Save Driver As...
Brings up a standard Macintosh file dialog window and allows the current Driver file to be saved under a new name, to a different folder, or to a different disk.
Page Setup...
Brings up a Macintosh page setup window to allow control of print parameters.
Print...
Brings up a Macintosh print dialog box and prints a standard report on the current subsystem. The report contains the currently displayed frequency response plots including all driver parameters and subsystem parameters. The report also includes the date and time printed. (from the keyboard use command P)
Quit
Closes MacSpeakerz and returns control to the Finder. (from the keyboard use
command Q)
Ordering Info...
Provides information on how to order a fully functional version of MacSpeakerz.
3.3 The Edit Menu Commands:
Undo
No Undo functions have been implemented in this version.
Cut, Copy, and Paste
These standard Macintosh functions can be used to cut, copy and paste among the edit fields.
Edit Driver
This command brings up the Driver Editor window. From the keyboard use command D, or locate Edit Driver under the Edit menu. Use it to enter the parameters for a new driver and then select Save Driver As... under the File menu to save the new driver file to disk. Use the cursor up/down arrows to move around the edit fields. Follow each entry with a "Return" from the keyboard to enter the data.
When finished, select the close box of the Driver Editor window to return to the Frequency Response window.
It is a good idea to select New Driver (under the File menu) before entering data for a new driver. This guarantees that no old data will be mixed with the new driver parameters.
Edit Subsystem
This command brings up the Subsystem Editor window. Use it to enter information to be saved with each Subsystem file you create. Subsystem information consists of the name of the subsystem, the number of identical drivers sharing the enclosure, box volume, box frequency, compliance ratio, the complete driver file, the contents of the 10 memories, vent information, and notes about the subsystem.
Note that the title of the Response window follows the Subsystem Name that appears in the Subsystem Editor window.
3.4 The Analysis Menu Commands:
Calculate Response
Selecting this menu item tells the system to calculate and plot the Responses that have been selected under the Analysis menu. Plots already on the screen will remain. Response calculation takes about 5 seconds on a standard Macintosh Plus. (from the keyboard use command F)
Clear & Calculate Response
This command has the same effect as Calculate Response except the screen is cleared before the new response is plotted. (from the keyboard use command G) Use this command to clear the Response window. Note: memories stored are not cleared by this command, only the display is cleared. Build a display for printing by clearing the display and then recalling only those memories you wish to print. The printed report contains only those response curves currently displayed. (from the keyboard use command E)
The Loudspeaker Response Functions
Frequency Response
Phase Response
Group Delay
Excursion Response
Impedance Response
The Loudspeaker Response menu items toggle on and off. Select once to turn the response on and select it again to turn it off. After the responses are calculated and drawn a small label is placed at the top tight of the Response window to indicate which responses are displayed. Only those responses that are selected are calculated.
0 dB Mode
dB SPL Mode
MacSpeakerz has two choices for the frequency response scale: 0 dB Mode and dB SPL Mode. SPL, or Sound Pressure Level is a measure of the perceived loudness of sound. While the 0dB scale is normally used to quickly locate the -3dB and -10dB frequencies on the response curve, the dB SPL scale is useful for showing how loud the speaker can play at full power, or at any power level you enter in the P(in) field of the Driver and Subsystem Parameters window. This feature is especially useful where it is necessary to derate the system power below the maximum thermal power rating of the driver in order to avoid violating the excursion limit of the driver in a particular enclosure.
When you open the MacSpeakerz application the default SPL distance is 1 meter. Scroll over to that field by using the up and down cursor keys. Enter values either in meters (top) or feet (bottom) followed by return. When you enter one the other is calculated automatically and the SPL scale is recalculated to reflect that new distance.
When you're in the SPL mode the screen will redraw whenever you enter a new value in one of these fields. If you do a return without changing the value, it won't redraw.
The SPL can be predicted for any Distance, D, any Number of Drivers, N, and at any subsystem Input Power level, P(in).
dB Per Division
You have a choice of three different dB per division settings. You can set the vertical scale to display either 1, 2, or 3 dB per division. The 1dB step allows for a high resolution plot or you can see a more course resolution plot of the frequency response at 3 dB. The default setting is 2 dB per division. The 1 and 3 dB settings allow you to zoom in to see detail or to zoom out to gain perspective.
Delay Range
Excursion Range
Impedance Range
Choose the scale for each Range. The default settings are shown by a checkmark.
3.5 The Display Menu Commands:
These commands are used to save and recall up to 10 response plots in the 10 memories. The contents of the memories are saved to disk as part of the users subsystem file.
Clear Display
Use this command to clear the Response window. Stored memories are not cleared by this command, only the display window is cleared. The printed report contains only those response curves displayed when the print command is given. (from the keyboard use command E)
Redraw
The display is cleared and the last calculated response is redrawn.
Show Plot Tokens
For monochrome screens, plot labels can be displayed to identify the type of response plot. The labels are also useful for busy printouts on a non-color printer.
Recall Mem
These commands are used to save and recall up to 10 response plots in the 10 memories.
Recall Mem 1, . . . Recall Mem 10
Draws the response plots previously saved to the selected memory. The Box Parameters window will be refreshed with the contents of the saved memory.
Store Mem 1, . . . Store Mem 10
Saves the current selected responses, V(B), F(B),Q(tc) and vent information in the selected memory. (from the keyboard use command 1, command 2, etc.)
Saving the Memories: The contents of the 10 memories are saved to disk as part of each subsystem file. The memories are saved only when the subsystem file is saved. Loading a subsystem file causes the memories to be restored to those saved with the subsystem file.
3.6 The Vent Menu Commands:
This menu lists various configurations of different diameter tubes often used for loudspeaker vents. Selecting one of these commands causes the net surface area of the tube(s) to be calculated and displayed in the S(v) field. Then, the required vent length is calculated and displayed as L(v) in the Box Parameters window. The vent length given in the L(v) field will be per vent. If you choose four 2" diameter vents, the length listed would be the length of one 2" vent.
You can enter either the Vent Surface Area in the S(v) field (followed by a Return) and the corresponding Vent Length, L(v), will be calculated; or, you can enter the L(v) and the required S(v) will be calculated. The latter method is useful when you want the vent to be a simple baffle cutout. Here, the vent length would be the baffle thickness. You would enter the baffle thickness as the vent length and the required surface area of the cutout would be calculated. You could then make the baffle cutout any convenient shape that would give the required surface area.
3.7 The Box Menu Command:
Box Dimensions
When you have finished your subsystem design and know the volume of the enclosure you want to use, you can use this command to get some recommended enclosure dimensions. Verify that the volume you want is entered in the Box Parameters window in the V(B) field, then select the Box Dimensions command. This will bring up a window which shows the dimensions for three enclosures of different shapes which will provide the box volume currently entered.
Rectangular Box Calculator
In addition to calculating the volume from arbitrary enclosure dimensions, MacSpeakerz will calculate the dimensions from the volume. You can enter box dimensions and the box volume will be calculated, or you can enter a volume and MacSpeakerz will calculate the dimensions using the golden ratio.
Trapezoidal Box Calculator
The trapezoidal box calculator includes an angle field to specify the angle of the side of the enclosure. The default is 15° when you first open the trapezoidal box calculator. MacSpeakerz takes the V(B) from the Box Parameters window and calculates the dimensions from a 15° trapezoidal enclosure according to the golden ratio. In the Demo version the dimensions have default settings which cannot be changed.
3.8 The Crossover Menu
MacSpeakerz has four types of crossover calculators: 1st, 2nd, and 3rd Order Butterworth, and 1st Order Series with adjustable damping. They all operate in the same manner with the user entering the impedances of the tweeter and woofer and specifying the crossover frequency. The MacSpeakerz Crossover Menu includes a Resonance Compensator Calculator, Inductance Compensator Calculator (Zobel) and a Tweeter Attenuator Calculator. These calculators have default entries that cannot be changed in this Demo version.
3.9 The MacSpeakerz Files:
MacSpeakerz can save two types of files, Driver files and Subsystem files. The Driver files make up the Driver Library. Subsystem files are the users working files on specific subsystem designs. Note: The term "subsystem" is used here to mean a loudspeaker driver (such as a woofer) in combination with its enclosure.
Driver Files
These are small files which occupy about 1K byte each or about 800 files per 800K byte floppy. The compact size of driver files allows users to accumulate very large libraries of drivers in a minimum of disk space.
A library of drivers is supplied with MacSpeakerz, but most users will want to create and save files of their own. Creating a new driver file is easy. First, you need to choose the Edit Driver command under the Edit menu. Then select New Driver under the File menu to clear the parameters of the current driver. Enter the data on the new driver, field by field, making sure to follow each entry with a "Return" from the keyboard. For MacSpeakerz to perform the small signal signal response calculations such as frequency, phase and group delay, the following parameters are required:
f(s) : The free air resonance
Q(ts) : The total Q of the driver
V(as) : The equivalent compliance volume
To utilize the excursion function these additional parameters are required:
x(max) : Max Peak Displacement
S(D) : Piston Area
n(0) : 1/2 Space Reference Efficiency
P(t) : Max Thermal Power (watts)
For impedance these parameters are required:
Q(ms) : Driver Mechanical Q
R(e) : DC Resistance
The other parameters are provided for completeness and to allow for the addition of new features in future versions of MacSpeakerz.
Subsystem Files
Each Subsystem file contains the subsystem parameters plus one complete driver file, enclosure parameters, and the contents of the 10 memories. Subsystem files occupy about 5K bytes of disk space. This allows one 800K floppy disk to hold about 150 Subsystem files.
Use Subsystem files to store your work in progress as well as your finished subsystems and notes on the subsystem. A Subsystem file is the place to create a collection of response curves for a particular driver in a range of closed and vented boxes. Then, whenever you want to do a new system design with that driver, you can start with the family of curves in that driver's Subsystem file.
Color Support
MacSpeakerz supports color on Macintosh computers. The various memories are displayed in colors which are coded to match the corresponding information in the plot windows legend.
Memory Color:
1 Brown
2 Red
3 Orange
4 Yellow
5 Green
6 Blue
7 Violet
8 Gray
9 Pink
0 Black
There is an Appendix A: Loudspeaker Design Aids, for those who wish to look at the mathematical formulations of loudspeaker design. Also included is a table of the most popular Closed Box alignments to use as guideposts for an optimum design.
Closed Box Alignments
Q(tc) = 1.0 This response corresponds to the smallest box of interest. It has a slightly peaked response.
Q(tc) = 0.707 This is a Butterworth alignment which has the flattest possible amplitude response.
Q(tc) = 0.577 This corresponds to a Bessel alignment which has the flattest possible delay response (most linear phase response).
Q(tc) = 0.50 This corresponds to a Critically Damped alignment in which the step response has no overshoot. It requires the largest box.
