[Tony[_2_]]

When I occasionally feel the need to build a set of pro speakers, it is usually because I
want a light, compact, high power, high efficiency system for the cost of a
box-on-a-stick. I couldn't justify the design time commitment, and most designs I've found
on the www are either innovative but misguided, or simple reflex boxes, and don't help me
at all.

Bill Fitzmaurice (www.billfitzmaurice.com) seems to design speakers whose SPL plots look
useful, but Bill's website gives very little real information, the graphs seem a little
inconsistent, the test facilities seem limited, and he even uses cheap piezo tweeters in
some models, so I'd appreciate hearing from anyone who has experience with them, or has
plans for good light tops (on sticks) and a sub.

The DR-200 and DR-250 are said to offer the absolute best possible performance, but also
the most build difficulty. Maybe they really do need to be complex to get the performance?
Maybe they contain unnecessary complications? Maybe the design hasn't been thought through
properly and optimized for manufacture? Also, I tried tweeter line arrays decades ago and
found the phasing colouration unacceptable for any system, so what might make these
designs any better? Ditto for the somewhat different kind of colouration of crossfire
arrays?

The OT-12 is a much simpler contender, but it would need a complex crossover to avoid both
tweeter damage when driven hard, and a notch around the crossover frequency.

The T-36 and T-HT subs seem to perform very well, but both are far too large for me, and
all the others seem to be aimed at DJ / club applications with good extension to 30 Hz,
but lacking in the 50 Hz region critical for bass and kick drum in bands (my
application). This may also imply that the drivers are not well loaded around 50 Hz,
greatly reducing the available SPL. Maybe the lower resonance (presumably a port) could be
tuned higher to fix this? Or maybe a 6th order bandpass might still be better for my sub?

Without more detail its impossible to judge all these things from the website, or whether
Bill's SPL efficiencies are gained by just omitting the proper damping, or how much the
various SPL plots are averaged. Bill's plans don't cost much, but with so many unknowns
I'd prefer some feedback before buying any.

[Geoff]

Tony wrote:
When I occasionally feel the need to build a set of pro speakers, it
is usually because I want a light, compact, high power, high
efficiency system for the cost of a box-on-a-stick. I couldn't
justify the design time commitment, and most designs I've found on
the www are either innovative but misguided, or simple reflex boxes,
and don't help me at all.

Bill Fitzmaurice (www.billfitzmaurice.com) seems to design speakers
whose SPL plots look useful, but Bill's website gives very little
real information, the graphs seem a little inconsistent, the test
facilities seem limited, and he even uses cheap piezo tweeters in
some models, so I'd appreciate hearing from anyone who has experience
with them, or has plans for good light tops (on sticks) and a sub.


Ah yes, light-weight, easy to build, and inexpensive speakers that don't
sound inferior to good speakers that cost much more.

I wonder why nobody has chanced upon the answer in the last couple of
decades..... ?


geoff

[Chris Hornbeck]

On Fri, 16 May 2008 12:38:03 +1000, Tony wrote:

www.billfitzmaurice.com

The DR-200 and DR-250

The model 200 looks like an array of piezo tweeters with
some un-named other drivers in a ported box. The claimed
104 dB SPL/1W/1M sensitivity is actually possible in this
volume and with the claimed about-190 Hz pole.

It would require lower-range drivers of 98 dB/1W/1M
sensitivity if four drivers were connected in series-parallel,
maintaining the impedance of a single driver and the
ability to connect safely to conventional amplifiers.

Or, it could be made with four drivers of conventional
but high-ish (in this case, 92 dB/1W/1M) sensitivity
connected all in parallel, presenting a possibly
dangerously low impedance to the driving amplifier.

Stick an OhmMeter across the terminals, and report back.
A number around an Ohm will be fine for a pro-sound
amplifier designed for that gig, but death for anything
less.


I can't in good conscience say anything comforting
about the DR250. Too many holes, too bogus. Just my
personal take, of course.

I can almost believe the asymtotic 160 Hz knee in
that size folded horn, but the sensitivity (a *very*
difficult to both measure and, even, to define, number)
of 106 dB/1W/1M is *way, way* biggie big.

To put it in context, the Klipschorn was (pretty much
honestly) rated at 104 dB/1W/1M and the highest
sensitivity drivers made (which closely approach
the theoretical maximum) are rated at an agreed-upon
number of 110 dB/1W/1M. The last number is equivalent
to about 30% conversion efficiency, an amazingly
big number in the scheme of things. And both at
conventional impedances.


Well, you wanted opinions; like assholes, everybody's
got one. Please forgive if mine is too public.

All the best fortune,

Chris Hornbeck
"I have a gift for enraging people, but if I ever bore you,
it'll be with a knife." -Louise Brooks

[BretLudwig]

I've never done any measurements on Bill's stuff BUT everyone who builds
them likes them.

Where IMO they do a good job especially is for electric bass. If you do
not need an extremely percussive and harsh popping sound (which I
personally hate) they are very efficient and give great volume out of
relatively low powered amps.

I wouldn't recommend them for home audio. The K-horn I would, IF you have
the right room. I would replace the vintage ass sucking Avedon T-35 tweeter
with a JBL or Beyma product for sure.

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