Re: What's difficult in DIY audio?



Andre Jute wrote:

Ian Bell wrote:
Andre Jute wrote:



But the most difficult thing of all, akin the frustratingly complex
transfer functions of tires in automobiles, is speakers. Whereas
almost anyone with the brains to get into a good college can design
and build a good power amp, given only a few years of hitting the
books and experimenting on the bench, it is really awesomely difficult
to build a better than mediocre speaker, and it is virtually
impossible to predict in detail how a speaker you intend building will
behave. I include bought speakers in this: the best speakers on the
market fall short of that theoretical adequacy daily exceeded in amp
design by margins that would get an amp designer laughed out of the
trade.


How speakers behave is determined more by the room than anything else. Very
few people acoustically treat their rooms and many treated rooms are done
so poorly.

All of this is true, Ian, but before you can determine how your
speaker reacts in any room, however treated, you first have to build a
good speaker, and in order to build a good speaker, unless you're
coincidentally also in the firewood business, you need to know how the
notional speaker will react on y parameter if you change element z. In
that perspective, the science of loudspeakers is a magnitude (or
probably more) less precise than the science of amplifiers.

There is no magic to building speakers, just a large number of
variables.

Superficially true, and then only to people who have never tried to
build a fullrange horn or a large electrostat. Even with multiconed
speakers there is still more magic than science, compared to say
amplifiers.


I won't dwell on the science and calculations that need to be considered
for ESL
or horns because -4 ppl worldwide are interested.

99% of diyer efforts are for dynamics, and a lot of work needs to be put
into making boxes of the right sizes,
well damped, internallt braced, baffled, wooled, and ported.
This is done in conjunction with driver selections.

Calculations have to be made for dynamic drivers intended for use when
in the boxes.
Impedances must all be measured, graphed, and equalizing networks
applied after calcs,
then speakers re-checked and Xover load values calculated.

After making the xover coils with several taps to allow for tweaking
a purchase of a range of bipolar electros is made, soa range of C values
can be tried.
Never think your are finished until you really have.

The xovers cannot be guessed. the response cannot be guessed.

The chance of guessing a good sound after guessing RLC values and box
and drivers and everything
is ZERO within a lifetime.

So one has to learn basic LCR theory, and set up a measuring system,
perhaps at least get what's offered at
http://www.testaudio.com/testaudio/

Please feel free to copy the designs of my speakers shown at
http://www.turneraudio.com.au/loudspeakers-new.html
http://www.turneraudio.com.au/loudspeakers-diy.html

There's a catch!
The crossover details are missing.

Price for a free design is that you have to learn about LCR basics.
Its a cruel price to have to pay, really, and I am a sod for leaving out
important details,
but why not, everyone bold and brave enough to make something
should be made to understand what they are doing, and never need spoon
feeding
once over the age of 18.

Instead of making plain boring looking rectangular boxes for speakers,
try always to excel my making things more difficult to gain the tiny
sonic benefits
by means of having sloping sides to all boxes.

Tip for the day :- speaker boxes should be sonically as lively as a dead
cat.
second, really fabulous veneer or cabinet work with rare exotic timbers
won't make the sound
the slightest bit better over using crude plywood/mdf composite with a
coat of acrylic
semigloss housepaint rolled on with a little roller.
Don't forget to fill and sand all the poor joints in the woodwork.
( people then say "gee what lovely plastic speakers you have"




Check out RDH which has some excellent design guidelines.

RDH4 is not bad on speakers, but we have had Theile and Small since
then,
and a potpourie of dynamic speaker driver makers who have saved us from
failed DIY horn, ribbon and ESL projects.
They have presented us with what 1957 could never give us.
Few amps existed that could drive what needed to be invented, and
pay packets of Joe Average and Mr Ordio Nutter were very lightweight.
Loungerooms were grubby places with screaming brats throwing biscuits
around,
and grumpy drunk husbands a bit miffed that the missus was damn
pregnant, again.
The family room, quiet listening room and Home Theatre were in the
distant future
awaiting invention and take up by the brats when they grew up.


Thanks for the tip. I check it immediately. For a giggle see the
reprint of my neddy guide to making the RDH digestible for you'n'me,
originally published in Glass Audio, at:
http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS%20RDH.html

Read all the articles in Wireless World / Electronics World on audio
since 1917,
and you will know a lot about amps and speakers and stuff.
This grand old mag is as good a read as RDH4.

Lots of challenging incomprehensibles.

Patrick Turner.



Ian

That reminds me. A good place for people who are starting on speakers
from scratch and need an overview to commence reading is the BBC man
Vivian Capel's An Introduction to Loudspeaker and Enclosure Design,
published by Babani and available at every WHS for a pittance.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
.

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