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at
 
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Default Using computer progs to design speakers?

Hi,


How good results can you get by using computer programs to design speakers?
There are many such progs available. How much trust would you place into the
results? If you make a cool design by a program and build it, what can you
expect in reality?

Can you recommend some good progs that would work? What are the most useful?
And how can you get most use of them?

Any thoughts? Info much appreciated.

-at


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Arny Krueger
 
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Default Using computer progs to design speakers?

"at" wrote in message


How good results can you get by using computer programs to design
speakers?


First, that depends on whether you're designing a subwoofer (easier, fairly
straight-forware) or a full range system (much more difficult and tricky).

There are many such progs available. How much trust would
you place into the results?


At worst, the best of them are good starting points. Doing it right takes a
lot of legwork. For example, passive crossver design "by the book" starts
with a full set of frequency response and complex impedance curves for each
driver.

At the least, a good program will simulate the performance of the design you
give it parameters for. This is a big help because you can run a lot of
simulations in the same time it would take you properly evaluate something
you tried in the real world.

If you make a cool design by a program
and build it, what can you expect in reality?


AFAIK many professional designers start out with a theoretical design, and
then polish it in the lab and listening room.

Can you recommend some good progs that would work? What are the most
useful? And how can you get most use of them?


Any thoughts? Info much appreciated.


You can "rent" a program by having retailers like Madisound make the design
for you with their software.


  #3   Report Post  
Rich.Andrews
 
Posts: n/a
Default Using computer progs to design speakers?

"at" wrote in
:

Hi,


How good results can you get by using computer programs to design
speakers? There are many such progs available. How much trust would you
place into the results? If you make a cool design by a program and build
it, what can you expect in reality?

Can you recommend some good progs that would work? What are the most
useful? And how can you get most use of them?

Any thoughts? Info much appreciated.

-at




I wrote my own program years ago and it worked pretty good.

As in all things, there is a little tuning to be done after it is built.

If you don't trust the programs, you could always do the math with a
pencil and paper.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.


  #4   Report Post  
Dick Pierce
 
Posts: n/a
Default Using computer progs to design speakers?

"at" wrote in message ...
How good results can you get by using computer programs to design speakers?
There are many such progs available. How much trust would you place into the
results? If you make a cool design by a program and build it, what can you
expect in reality?

Can you recommend some good progs that would work? What are the most useful?
And how can you get most use of them?


The accuracy of these programs is limited by a number of contraints:

1. Your understanding of the limits of the model. Any program based
on, for example, the Thiele-Small model will work well (given
other contraints listed here) in predicting the resulting response
with in the piston band of the system, but will not include
diffraction and baffle effects. If you expect the predicted
response of a 12" woofer at 800 Hz to be accurate, you WILL be
disappointed because you did not understand the limits of the
model.

2. As in all such excercises, garbage in give garbage out. And that
means if you plug in driver parameters from a catalog or a spec
sheet and expect the results to reflect reality you WILL be
disaapointed, because you failed to account for the fact that
there can (and often is) large variations in the operating
parameters of drivers AND differences between the specs and
purchased reality. Similarily, the performance and drivers
changes with conditions, and if by not accounting for these
changes you design a system that violates the constraints, you
WILL be disappointed in the results.

3. The sophistication of the model and the accuracy of the model
description. If you make assumptions about some of the detailed
parameters of the design, you WILL be disappointed. For example,
you design a system which assumes perfect absorbtion in the
enclosu if your design depends upon that assumption, you WILL
be disappointed in the result, because you made unrealistic
assumptions

Now, notice that all of the above comments have the operative word
"you" as the agent of failure. This is based on my experience extending
over 30 years of doing this wort of work, more importantrly, of watching
many others do it. My observations show clearly that the discrepancy
between the predicted design and implemented reality is due almost
entirely to the program user: that person's failure to understand
what the model does and what its limitations are, providing unrealistic
parameters to the program, and making unrealistic assumptions about
the design. I have seen a half dozen speaker design programs take the
same garbage data and result in the same garbage design, and those same
half-dozen programs take the same good data and operating under the
same reasonable contraints spit out a VERY competent and realizable
design.

Now, beyond that, there's another factor you didn't ask about. While
all of the programs, within their constraints, do a very reasonable
job, some of them a simply miserable to USE because the person who
wrote the program spent most of their time working on implementing
the math and NO time on dealing with simple usability issues. What
good is the most sophisticated, realistic modeling program if you
end up being so frustrated using it that you're ready to shoot the
computer followed by yourself? This problem, regrattbly, plagues more
programs than it should, and it's not just limited to speaker
software, to be sure.

An example of this are the older versions of LMS. It's a VERY good
mathematical model under the hood, but it has a LOUSY user interface.
I don't know if they've cleaned it up or not, but it was bad enough
that I found it difficult to recommend even considering the sophistication
of the model. It also was buggy in the sense that you could see gross
mathematical truncation or roundoff errors occuring in plots.
  #5   Report Post  
Don Pearce
 
Posts: n/a
Default Using computer progs to design speakers?

On Tue, 3 Aug 2004 12:50:26 +0300, "at"
wrote:

Hi,


How good results can you get by using computer programs to design speakers?
There are many such progs available. How much trust would you place into the
results? If you make a cool design by a program and build it, what can you
expect in reality?

Can you recommend some good progs that would work? What are the most useful?
And how can you get most use of them?

Any thoughts? Info much appreciated.

-at


Do bear in mind that these computer programmes generally deal with
nothing deeper than the physical conditions surrounding the
fundamental resonance of a speaker driver. They will help you with
gross alignment and tuning of a cabinet, but they have nothing within
them that addresses the way a driver actually sounds. That you must do
by ear, either by persuading manufacturers to donate freebies for
testing, or by listening to speakers that contain drivers on your
candidate list.

The maths itself is pretty straightforward, and the computer
programmes are really not much more than a convenient and pretty front
end. You can do the sums and produce graphs in a spreadsheet very
easily once you have read up on the theory.

I dare say there are programmes that delve rather more deeply into the
physics and mechanical properties of drivers and cabinets, but my bet
is that these are proprietory to manufacturers, and they won't let you
have a copy.

d

Pearce Consulting
http://www.pearce.uk.com


  #6   Report Post  
at
 
Posts: n/a
Default Using computer progs to design speakers?

Thank you very much for your thoughts. This is excellent advice.

Thanks!

-at

"Dick Pierce" wrote in message
om...
"at" wrote in message

...
How good results can you get by using computer programs to design

speakers?
There are many such progs available. How much trust would you place into

the
results? If you make a cool design by a program and build it, what can

you
expect in reality?

Can you recommend some good progs that would work? What are the most

useful?
And how can you get most use of them?


The accuracy of these programs is limited by a number of contraints:

1. Your understanding of the limits of the model. Any program based
on, for example, the Thiele-Small model will work well (given
other contraints listed here) in predicting the resulting response
with in the piston band of the system, but will not include
diffraction and baffle effects. If you expect the predicted
response of a 12" woofer at 800 Hz to be accurate, you WILL be
disappointed because you did not understand the limits of the
model.

2. As in all such excercises, garbage in give garbage out. And that
means if you plug in driver parameters from a catalog or a spec
sheet and expect the results to reflect reality you WILL be
disaapointed, because you failed to account for the fact that
there can (and often is) large variations in the operating
parameters of drivers AND differences between the specs and
purchased reality. Similarily, the performance and drivers
changes with conditions, and if by not accounting for these
changes you design a system that violates the constraints, you
WILL be disappointed in the results.

3. The sophistication of the model and the accuracy of the model
description. If you make assumptions about some of the detailed
parameters of the design, you WILL be disappointed. For example,
you design a system which assumes perfect absorbtion in the
enclosu if your design depends upon that assumption, you WILL
be disappointed in the result, because you made unrealistic
assumptions

Now, notice that all of the above comments have the operative word
"you" as the agent of failure. This is based on my experience extending
over 30 years of doing this wort of work, more importantrly, of watching
many others do it. My observations show clearly that the discrepancy
between the predicted design and implemented reality is due almost
entirely to the program user: that person's failure to understand
what the model does and what its limitations are, providing unrealistic
parameters to the program, and making unrealistic assumptions about
the design. I have seen a half dozen speaker design programs take the
same garbage data and result in the same garbage design, and those same
half-dozen programs take the same good data and operating under the
same reasonable contraints spit out a VERY competent and realizable
design.

Now, beyond that, there's another factor you didn't ask about. While
all of the programs, within their constraints, do a very reasonable
job, some of them a simply miserable to USE because the person who
wrote the program spent most of their time working on implementing
the math and NO time on dealing with simple usability issues. What
good is the most sophisticated, realistic modeling program if you
end up being so frustrated using it that you're ready to shoot the
computer followed by yourself? This problem, regrattbly, plagues more
programs than it should, and it's not just limited to speaker
software, to be sure.

An example of this are the older versions of LMS. It's a VERY good
mathematical model under the hood, but it has a LOUSY user interface.
I don't know if they've cleaned it up or not, but it was bad enough
that I found it difficult to recommend even considering the sophistication
of the model. It also was buggy in the sense that you could see gross
mathematical truncation or roundoff errors occuring in plots.



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Peter Larsen
 
Posts: n/a
Default

at wrote:

Hi,


How good results can you get by using computer programs to
design speakers?


The designer still makes the choices.

Can you recommend some good progs that would work?


CALSOD

What are the most useful?


I don't know, there are others. Some probably have steeper learning
curves than others, all are highly likely to require that you can design
loudspeakers without them.

And how can you get most use of them?


Climb the learning curve.

Any thoughts? Info much appreciated.


A good design will help you get it simple. Rethink if it has to be
complicated. Learn what imperfections to accept and what to worry about,
some imperfection is unavoidable in a practical design, the art of the
designer is (also) the art of choosing wisely.

-at



Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************


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