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In article <1e95llINN9gt@saffron.csv.warwick.ac.uk> maufd@csv.warwick.ac.uk (Mr J S Graley) writes:
>I am trying to design loudspeakers from fundemental aucoustic laws. This has
>been a harder task than I seemed initially. Most books on speakers skirt 
>around the neccesarry explainations and simply give you final designs with
>formulae for dimensions, but deducing the theory from this evidence is a
>near herculean task!
>
>I wonder if any people in the know about this could either post or email me
>information or easy to obtain (eg in England) sources of info?
>
>I interested in the following effects:
>
> Exponential horns
>
> Ported cavities
>
> Level of airload at various frequencies
>
> Effect of airload on driver efficiency

Much of the information you are looking for (at least on a theoretical
basis) is available in two relatively significant works:

    N. W. McLachlan, "Loud Speakers: Theory, Performance, Testing and
       Design," Dover, New York 1934 (1960 ed.)

    L. L. Beranek, "Acoustics," American Institute of Physics, New York,
       1954, 1986

There are also the landmark articles by A. N. Thiele and Richard H. Small,
available from the Audio Engineering Society Journal between 1971 and
1973. These are probably the most relevant sources for theory on how to
make the damn things work.

Unfortunately, as the vast market of mediocre to bad speakers illustrate,
it takes a lot more than this to design good loudspeakers. (actually, it
takes a proper understanding of this information to make things work,
something which the vast majority of engineers to not posess!).

-- 
|                Dick Pierce                |
|    Loudspeaker and Software Consulting    |
| 17 Sartelle Street   Pepperell, MA  01463 |
|       (508) 433-9183 (Voice and FAX)      |

Can you explain your goal a bit more?  What do you mean by "design
a loudspeaker from fundamental acoustics laws"?

For example, suppose your primary goal is to reproduce the same
music in your listening room that you heard in a concert hall.  
Your first step would then be to build a model human head with a 
microphone in each ear socket.  You would then take this to your
concert hall and make the recording.  Unfortunately, when you play
that same music through your loudspeaker at home, the room acoustics
cause the sound you hear to be different than what was recorded in
the concert hall.  Thus, no loudspeaker design can achieve exact
reproduction of sound without first controlling the room acoustics
(i.e. use a pair of good headphones).

If your primary goal is to build a loadspeaker that creates an
acoustic sound pressure wave that is equivalent to the applied
voltage, you must first realize that speakers are mechanical devices.
Any real mechanical device has non-ideal (and non-linear) properties
that prevent the speaker from operating perfectly.  Of course,
the defects may be so small as to be imperceptible to the human ear.

As I say, I am not sure what you mean by "design a loudspeaker from
fundamental acoustics laws".   Can you be more specific about your
request for info?

In any case, I also recommend Beranek's book on Acoustics.  The
modeling techniques can be applied to any system.  At MIT, we use
these techniques in Bose's Acoustics class to model loadspeakers as
well as ported speaker designs (as well as many other systems).

Neal Lackritz

I entirely agree with Pierce's comments, and I want to reinforce the book
choices.  The book by McLachlan "Loud Speakers" is excellent, but very
hard to find.  The 1960 Dover edition is the one you want so you will have to
scour used book stores for it because it is out of print.
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	R   2	      Real Monza	     kdrolt@athena.mit.edu
	|___|					grad student !!
	|   |	'64 Corvair Convertible      mit ocean engineering
	1   3					underwater sound
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>I am trying to design loudspeakers from fundemental aucoustic laws. This has
>been a harder task than I seemed initially. Most books on speakers skirt 
>around the neccesarry explainations and simply give you final designs with
>formulae for dimensions, but deducing the theory from this evidence is a
>near herculean task!

>I wonder if any people in the know about this could either post or email me
>information or easy to obtain (eg in England) sources of info?

>I interested in the following effects:

> Exponential horns

> Ported cavities

> Level of airload at various frequencies

> Effect of airload on driver efficiency

There is a book on speaker design by David Weems (sp?) which I found 
very usefull.  Has theory and examples.  Title is something like
"Designing Speakers" or something like that, I don't remember exactly.
                                            DHP

Look for a book by Harry(?) Olson.

When he was at RCA around WWII, he did a good job at describing the practical
amenities of loudspeaker design.


Other than that, keep in mind that all you are trying to do is to drive a
parcel of air at an audio rate, with a plate (or horn) large enough to produce
the sound power you want without nonlinear effects due to the compressibility
of air.  (196 dB = 1 atmosphere).

Most popular way has been a lightweight solenoid driven by reaction in a
magnetic gap--- the common loudspeaker.

Enclosures are merely to enhance the radiation over the lower range of
frequencies, the higher being effected by direct radiation fron the driven
plate ('cone').


Good luck!

In article <1992Nov19.233034.25857@magnus.acs.ohio-state.edu> acampane@magnus.acs.ohio-state.edu (Angelo Campanella) writes:
>
>Look for a book by Harry(?) Olson.
>
>When he was at RCA around WWII, he did a good job at describing the practical
>amenities of loudspeaker design.
>
Yeah, he did a pretty good job. Except he was wrong about how bass reflex
systems work. And he was wrong about how passive radiator systems work,
and we was basically a few bricks short of a chimney describing sealed-box
direct radiators. He was dealing in an era where the understandings of
driver materials, radiation pattern, mutual driver-vent-cabinet
interactions, crossover netaorks and radiation patterns, cabinet
coloration, and so forth were either inheard of or, at best crudely hinted at.

Other than the fact that he got most of it wrong, yeah, he did a good job.

Let's not be to hard, though, on old Harry, he was one of the more
knowledgeable people of the day. But we have learned a hell of a lot since
his time. Yeah, the McLachlan book I recommended is from the same vintage,
but his is a hell of a lot more in terms of theory than Olson's, which is
what the original poster was looking for. And the very basic theory still
stands reasonably well.

>Other than that, keep in mind that all you are trying to do is to drive a
>parcel of air at an audio rate, with a plate (or horn) large enough to produce
>the sound power you want without nonlinear effects due to the compressibility
>of air.  (196 dB = 1 atmosphere).
>
>Most popular way has been a lightweight solenoid driven by reaction in a
>magnetic gap--- the common loudspeaker.
>
>Enclosures are merely to enhance the radiation over the lower range of
>frequencies, the higher being effected by direct radiation fron the driven
>plate ('cone').

This is a tremendous oversimplification of the real problems at hand but,
I presume (or I sincerely hope) they are, in fact, stated as such
intentionally.

By the way, I wouldn't sweat trying to reach 196 dB. That's the sound
pressure level of a Saturn V launch AT THE PAD. (Saturn V's were spec'ed
at producing about 6 million whats of acoustic power at sea level,
equivalent to about 189 dB SPL at close range. Might make for an
interesting surround-sound demo, though!)



-- 
|                Dick Pierce                |
|    Loudspeaker and Software Consulting    |
| 17 Sartelle Street   Pepperell, MA  01463 |
|       (508) 433-9183 (Voice and FAX)      |