Club Amiga de Montreal - CAM/CAM_CD_1.iso/files/373.lha/SpkrSimDemo_v2.0/SpkrSim_Instructions.pp/SpkrSim_Instructions

Text File | 1990-05-06 | 15.6 KB | 319 lines

                         SpeakerSim Demo

                       (c) 1988 dissidents


                    The Up Front Information



     We would  like  to  thank  you  for  your  interest  in  our
products.   SpeakerSim  is  the outgrowth of our own search for a
good loudspeaker analysis tool.  Actually, this  demo  shows  off
the third generation of SpeakerSim.  The first generation program
was produced in 1980 for a time sharing mini computer, while  the
second  generation  appeared  some  4-5  years later running on a
small  8  bit  home  computer.   Neither  program  was   released
commercially,   rather,   they  were  used  for  our  design  and
consulting work only.  When the Amiga was introduced, it appeared
to be the perfect vehicle for the third generation of SpeakerSim.
SpeakerSim now boasts far more flexibility than  was  dreamed  of
back  at  generation  one.   SpeakerSim  offers  a full Intuition
interface, color control,  a  variety  of  graphing  modes,  high
resolution display, and very fast calculation times.  In fact, it
takes only a few seconds to produce plots that  required  several
minutes with generation two.

     This instruction sheet assumes that you  are  familiar  with
the  operation of the Amiga personal computer.  SpeakerSim uses a
relatively standard Intuition  interface  with  pull-down  menus,
requesters,  gadgets  and so forth.  If you are not familiar with
these items, we recommend that you read the  Amiga  Users  Manual
before  running  SpeakerSim.   Some  familiarity with AmigaDOS is
also helpful.  Please note that when this manual says to 'select'
or  'click on' an item, move the mouse pointer over the object in
question and then depress and  release  the  left  mouse  button.
This  demo does just about everything that the real program does.
The exceptions are that this demo runs only in  640  x  200  mode
(640  x 400 version not available in demo), plotting is disabled,
and that you are stuck with a single driver and have  no  way  of
calling  in  other loudspeakers for test purposes.  Also, some of
the calculations have been altered, which slows down the plotting
times  a  bit.   Finally, some of the 'saftey valves' and 'bullet
proofing' have been eliminated, so we suggest that you not try to
do  anything  that  is out of the ordinary or just plain 'weird'.
Obviously, we had to 'sabotage' the demo to prevent  its  use  in
serious design work!!

Amiga, Workbench, and  Intuition  are  trademarks  of  Commodore-
Amiga, Inc.





                  'What's All This Then?'



     SpeakerSim  is  a  tool  that  will  help  you   to   design
loudspeaker  systems.  These systems can be used for a variety of
applications,  including  home  Hi-Fi  and   professional   sound
reinforcement.   In  order  to successfully utilize this program,
you must be familiar with the concept of frequency  response  and
the practical limits and trade-offs of loudspeaker system design.

     SpeakerSim's primary use is in modeling the  lower  half  of
the   audio   spectrum.    Technically,   the  program  uses  the
established  Thiele-Small  vented   approach.    Vented   systems
(sometimes  called ported systems) offer the advantages of simple
construction and smooth, extended frequency response.  SpeakerSim
can  also  be  used  to  model closed-box (AKA sealed or infinite
baffle) systems.  Generally, the resulting graphs are accurate up
to  several  hundred  Hertz.   Above  this,  cone  breakup  modes
dominate the response curve.  Since cone breakup  usually  occurs
at  higher  frequencies for smaller diameter drivers, midbass and
midrange drivers may also be modeled.

     When first activated, SpeakerSim will simply  show  a  blank
screen and its title bar.  You should think of this surface as if
it were a very intelligent and dynamic sheet of graph paper.  All
response  plotting will take place here and you will have control
over a number of different parameters and graph types.  You share
this  surface with a number of small windows and requesters which
will pop up when SpeakerSim needs input from you.  At the  bottom
of  the  display is a status line containing relevant information
about the plot.  By holding down the left mouse button,  you  can
determine the frequency/amplitude coordinates of whatever section
of the plot that you happen to be pointing.

     Generally, there are two ways of using this program;  either
in the design of an all-new system, or in the customization of an
existing system.  In either case, you will be trying  to  produce
the smoothest, most extended response curve possible.  SpeakerSim
allows you to alter the key parameters, Fb (tuning frequency) and
Vb  (box  volume).   You  may  also  note  the  effects of device
parameter variation by using the 'multi' graph mode.   This  mode
(actually  two  different  modes)  produces 14 frequency response
curves.  One parameter of your choosing is altered from sweep  to
sweep,   allowing   you  to  take  construction  tolerances  into
consideration.  It may also be used to speed the  design  process
in  other ways.  Once you achieve the response curve desired, you
may save it as an IFF picture, or dump the image directly to your
printer.   SpeakerSim  will  also  calculate  the  required  vent
dimensions  for  you.   SpeakerSim  will  multi-task  with  other
programs.   You also have complete control over color, with 16 of
your choosing out of a palette of 4096.









                       Demo Lesson part 1

              'So what's the basic idea here, eh?'



     If you would like  to  see  a  few  examples  of  SpeakerSim
graphs,  examine  the picture files with the Display utility.  To
use Display, open the System drawer  and  click  on  the  Display
icon.  Now, while holding down the shift key, double click on the
desired Example icon.  In a moment you will see the Example.   To
stop  Display,  simply  click  in  the  upper  left corner of the
screen.

     When the program is started you will be greeted by  a  blank
screen  and the title bar.  To see an example of just how quickly
the program plots, hold down the mouse  menu  button  and  select
Do-It  under  the  Do-It  menu.   You  will  be  greeted with the
plotting requester.  By default, a loudspeaker called 'Demo Unit'
is  set  to  run.  The other menu attributes default to 2D Normal
mode, Smooth shape, and Small Signal response type (You may  wish
to  verify  this).   Now,  simply  click on the 'Plot' button and
watch.  The requester will  disappear,  semi-log  paper  will  be
drawn  with the appropriate scales, title and status bar, and the
plotting  will  start.   Note  that  the  title  bar   now   says
'Graphing..'  and that the pointer has turned into a 'Wait' sign.
The plot should only take a few seconds to complete, signified by
the return of the normal arrow type pointer.

      You may now go back to Do-It, set  new  Fb  and  Vb  values,
erase the screen and plot this new set-up.  You may call Do-It as
many times in succession as you wish.  To  overlay  graphs,  just
skip  the  Erase  step.   You  may  also  change any of the graph
attributes between plots, such as  Mode,  Shape,  Multi-Parameter
(if  applicable),  and Response-Type.  To find the coordinates of
any point on the graph, just hold down the left mouse button  and
move  the  pointer  to the desired location- the coordinates will
appear in the status bar, updated in real-time.   Once  you  have
settled  on  a design worthy of remembering, you may select Print
from the Project Control menu for a hard copy, or you may  select
Save  IFF for a screen image file (standard IFF ILBM form).  When
you are finished with the program, select Quit from  the  Project
Control menu, and answer 'Yes' when it asks for verification.

     That's  the  basic  idea  behind  using  SpeakerSim.    Now,
continue on to the next section for a more detailed, step-by-step
example.






                    Demo Lesson part 2

             'I gotta know more, More, MORE !!!'



     First, boot up  your  Amiga  and  start  the  SpeakerSimDemo
program.  Don't alter any settings yet.


     Let's plot a single small signal graph.  For the attributes,
select  Shape = Smooth, Mode = 2D Normal (Multi-Parameter will be
ignored), and Response-Type = Small Signal.  Select Do-It and set
Fb  and  Vb  to  'reasonable'  values, like 40-60Hz and 2-6 cubic
feet.  Note  that,  like  Multi-Parameter,  the  Start  and  Stop
Factors  will  be  ignored  since  we have chosen 2D Normal Mode.
(Either 2D Multi or 3D Multi must be chosen for these factors  to
take  effect,  as  you  shall  see).   At this point, your screen
should be blank, so click on 'Plot'.  In a few seconds,  a  nice,
flat  curve  should  be  drawn.   Note  that  the status line now
contains the driver name and the chosen Fb and Vb values.   Let's
examine  this plot a little closer with the mouse.  While holding
down the left mouse button, move the pointer around  the  screen.
You  will  notice  that  the  Frequency  (F)  and  Amplitude (dB)
coordinates in the status line are constantly tracking your mouse
position.  Releasing the mouse button will "freeze" the readings.
At this point we would like to do an overlay, so it  would  be  a
good  idea  if  we switched pen colors.  To do this, select Color
and click on one of the middle  color  boxes.   To  exit,  select
either  'Okay'  or 'Cancel'.  To graph, select Do-It, type in new
value for Fb, and select 'Plot'.  DO NOT SELECT ERASE.  In a  few
seconds a second plot will appear over the first.


     You may now ask yourself "How  tight  is  the  manufacturers
quality  control?".   Let's  examine  how  a  +/-10% tolerance on
acoustic compliance (Vas) will effect the design.  Select Mode  =
2D  Multi  and Multi-Parameter = Vas.  Select Do-It and set Start
Factor = .9 (10% down) and Stop Factor = 1.1 (10% up).   Finally,
select 'Erase' and 'Plot'.  A series of graphs is now drawn, each
one with a slightly different Vas.  For a slightly different view
of  the  same  subject, set Mode = 3D Multi, erase the screen and
re-plot.  You will now see a third axis extending  out  from  the
origin.   This  is  the  Multi-Paramter  axis  (in  this  case it
represents variations in Vas).  Each curve  is  displaced  at  an
angle  so  that  trends can be easily spotted.  This displacement
'un-calibrates' the mouse cursor.  In  order  to  get  a  correct
reading  for  any  curve, click on the appropriate color box from
the 14 that appear along the right edge of the screen.   A  small
arrow will point to the selected color.  As you may have noticed,
Multi plots take awhile to generate.  You can speed this  process
considerably  by  setting  Shape  =  Sketch  (do this, erase, and
re-plot).  Thm cost for this speed is a somewhat 'jaggy' shape.





     You can also use Multi to run  through  designs  quickly  by
using  Fb  or  Vb as the Multi-Parameter over wide ranges.  Let's
say that a friend wants to use this driver in a 2 cubic foot  box
that  already  exists.   Where should you tune it?  For this run,
set Mode = 2D or 3D Multi, Multi-Parameter = Fb, Start  Factor  =
.5  and  Stop Factor = 2.0.  Vb must be set to 2 cubic feet.  For
Fb, try around 40 Hz, as this will produce a range of 20 Hz to 80
Hz,  which  should  certainly  show  us  the  trend.   Once these
variables  are  set,  erase  the  screen,  and  plot.   Note  the
variation  in shapes.  Normally, you would find the flatest curve
and investigate further.


     Once a satisfactory small signal response is  produced,  you
may  wish to check the maximum acoustic output power.  Set Mode =
2D Normal, and Response-Type = Max Power.  Set Fb and Vb  to  the
desired  values, erase, and plot.  This curve represents the safe
operating area of the driver/enclosure.  It is  in  essence,  the
lesser of both the Thermal and Excursion Limits.  As an exercise,
overlay the Thermal and Excursion Limit  curves  on  the  Maximum
Power  curve  and note which type dominates at given frequencies.
These curves can be useful for finding  possible  failure  modes.
Note  that  the  power graphs indicate signal strength in dBW.  0
dBW = 1 acoustic watt on these graphs.  Designers of high  output
monitors  or  PA  systems  should  find  this  useful for minimum
acceptable output and direct/reverberant field calculations.


     The only item left in the design cycle is to  determine  the
vent  dimensions.   To  get these numbers, select 'Run Vent' from
the Project menu.  The vent is calculated using the  most  recent
settings  for  Fb  and  Vb, (the drivers displacement volume also
plays a role in this).


     When a given design is settled on, it would be wise to  save
the result.  You have two basic options; either save it as an IFF
picture (ILBM) file, or dump the screen image  to  your  printer.
Saving  an  IFF  pic takes far less time than doing a print dump.
To save the screen, select Save IFF from the Project  menu.   You
will  now  be  greeted  with  the  Save IFF file requester, which
allows you to scan your  disks  and  directories  to  see  what's
available.   After  finding an appropriate disk and/or directory,
type in a name for the graph.  (Try something  like  FirstPic  on
the  RAM:  disk.) When you've got the save name set, click on the
'Okay' button.  A small  requester  will  now  appear  with  your
chosen  name,  and  a place for an optional graph note for future
reference.  This note will be saved  in  place  of  the  screen's
title  bar,  and  is particularly suited for use with the Display
utility.  When  you've  finished  typing,  click  on  the  'Save'
button.  Saving should only take a few moments.  Now, if you pull
down the SpeakerSim screen and open the RAM  disk  on  Workbench,
you  will  see  your graph's icon, saved as FirstPic.  If you try
saving another graph as FirstPic, the program will warn you  that
a  graph  with that name already exists.  The inverse of Save IFF
is Load IFF, which lets  you  call  in  old  graphs  to  use  for
comparisons,  design  starting  points,  etc.  To try this, first
call up Do-It and erase the screen (exit via  'Cancel').   Select
Load  IFF,  and  when  the  file requester appears, scan the RAM:
disk in order to see the available files.  (Use the  'Next  Disk'
button  if  required.) You should see the name of graph which was
just saved (FirstPic) as well as its icon  (FirstPic.info).   (If
it  is not visible, scan though the names with the scroll bar and
arrows placed off to the right).  By clicking on the graph  name,
it  will  automatically  be loaded into the 'Name:' box.  At this
point, simply click on the 'Okay' button and  a  small  requester
will  appear  with the chosen file name, and two loading choices.
If you click on 'Use Picture Colors', the graph  will  be  loaded
with  its  own  color map.  By selecting 'Use Present Colors' the
picture's color map is ignored.  (In our example both the picture
and  present  maps are the same, so it won't matter which one you
choose).  If desired, you may load in any of the demo graphs, and
experiment with the Present/Picture choice.


     For a direct hard copy,  select  'Print'  from  the  Project
menu.   Two  types  of printing are supported; 'asynch' if memory
allows (which lets you continue doing other things), and  'synch'
(which  forces you to wait until printing is completed before you
can do anything else with SpeakerSim).  Generally, you will  want
to  say 'Yes' at the 'Remap background to white?' prompt in order
to minimize printer ribbon wear and tear.


     The only thing left to do is to quit the program.   Quit  is
found  at  the bottom of the Project menu.  Verification is asked
for.  Answer 'Yeah' if it's really time to do something else.  If
you find it difficult to do something else, you should answer 'No
Way', and continue to graph (but don't  forget  to  let  the  dog
out).