From Transmissions In General...
There are all sorts of transmissions. Automobile ones span the gamut from
ironclad to clunky to terminal slip jobs. Radio broadcast transmissions can
slip depending on whether the program director’s creativity sparks or
spasms. With cellular transmissions, it’s a matter of who’s calling,
when and from where. Treacherous instant-on X-band police radar
transmissions? Except for the boringly good types who actually
believe in the speed limit, those are baaad no matter what.
Then you have satellite uplinks to outer space probes that transmit
high-resolution surface scans of celestial bodies light years removed.
Spiritual transmissions from inner space link up devotees with deities and
long deceased masters outside of Space-Time as we commonly perceive it.
Transmissions of potent healing are seemingly at odds with three-dimensional
limitations as well, and ancestral transmissions via dreams and trance
vision cut through the same illusory crap by connecting successive
generations in ‘primitive’ cultures directly with the wisdom of their
forbearers. Lastly, certain dedicated enclaves of our ‘civilized’
society attempt to transmit artistic intent via transparent audio hardware.
Are your brain cells transmitting havoc yet?
McGinty transmitting – anybody listening?
With this latter kind of HiFi transmission,
some musical playback arrives on the scenes of our listening rooms with good
bass, some with bad bass and some with no bass at all. It’s McGinty’s
credo to transmit bass of the forth kind – well damped, articulate,
extended and amplifier-friendly; in so many words, better than merely good.
To chase this elusive rainbow, he’s dedicated his cabinet craft to the
so-called transmission line. We’ll find a fully-fledged TL already
in his very first Meadowlark design, the Kestrel. Since then, this complex
cabinet solution for how to progressively attenuate a woofer’s rear wave
has become part and parcel of Meadowlark’s multi-tiered recipe for sonic
superiority: first-order phase- and time aligned networks; separate sub
chambers for the crossovers; decoupling of baffles, drivers and various
other vital crossover parts; and transmission-line bass loading.
...To
Felt-Lined Transmissions In Particular
McGinty had a highly plausible explanation for
the relative rarity of transmission lines in contemporary loudspeaker art:
they’re fiendishly difficult to design and execute properly. Without
available computer software that could aid an aspiring designer as the
established and proven programs for sealed and vented boxes do, the
blueprinting of the serpentine lines inside the enclosure remains a
time-consuming process of endless prototyping. Despite a name like his,
you’ll never get it down pat. The Patman then quipped that even the
tenth attempt could still rather resemble the work of a lousy marksman.
Faced with such dubious target practice, salaried corporate engineers of
major speaker design houses tend to value their job security over appearing
to fish in the dark. They’d rather not present their superiors with
the twentieth reject cabinet with the feeble assurance of “we’re getting
darn close now”.
Vireo monitor TL
But McGinty the cabinet master straddles a
horse of a different color. He owns his own company. He isn’t beholden to
designing by committee. He doesn’t justify his progress to a treasurer or
managerial inspection team. He builds one-ups until he either gets blue in
the face or nails the bastard – and his successful designs are clear
testament to who eventually wins these design room brawls at the end of the
argument. Of course, accumulated experience over time provides the resilient
with an intuitive feel for his subject matter. It empowers McGinty to now
push the line specifics of a new model’s first prototype enclosure much
closer to the final finish line than when he first embarked on this very
poorly documented process. Still, development time remains far in excess of
standard sealed or vented designs, the amount of throwaway cabinets for
firewood potentially daunting.
How Does A
Transmission Line Work Differently
From A Classic Vented Box?
The job of a speaker enclosure is to convert
the rear-firing half of a driver’s output into heat as effectively as
possible. A vented box goes about this assignment by using its internal air
mass through elastic compression and rarefaction. This works but isn’t
terribly effective. Such a system -- made up of the driver, the trapped air
inside the box and the exit port – is highly resonant: once the woofer
activates them, the resonant frequencies of port and cabinet ring. This
equals a low damping factor or high resonant Q. It shows up on impedance
transfer function plots as the classic saddle of two high impedance bumps
that correspond to the enclosure and the port, the size of these peaks
directly related to the severity of the ringing.
A properly executed transmission line without
organ pipe resonances lowers this Q by eliminating or greatly damping
said ringing distortion. It presents the rear wave with a tunnel whose
absorptive qualities are greatly enhanced, usually by stuffing the line with
Polyester wool or similar filler material. The woofer’s rear radiation is
allowed to run its course through the line to exhaust itself in the process.
In a full-length TL, the extension of this – usually folded – flute
inside the main cabinet equals the wavelength of the lowest frequency the
system can reproduce. Hence, 20Hz full-length transmission line loudspeakers
require very tall or deep cabinets. More sensible for domestic acceptance
are half-length TLs that perhaps don’t absorb their airflow entirely but
certainly go far in attenuating its intensity.
The considerable amount of internal filler
materials in a progressively damped traditional line can result in the dry
and over-damped syndrome of what’s referred to as the classic “British
sound”. The explosive American depletive of f—k is rendered as
the more polite fog. This approach to material damping is also prone
to somewhat haphazard settling and shifting. To avoid either liability,
McGinty eschews filler material altogether. Instead, he damps the sidewalls
of his lines with felt 5/8” thick. This treatment doesn’t seem to impart
the slightly reluctant coloration of stuffiness but retains the natural
decay and dynamically lively sound he favors. It’s also much more
consistent to manufacture.
If you were to use a band saw lengthwise to
slice open a Kestrel or Shearwater along its frontal centerline, you’d see
the heavy felt damping on the sidewalls. You’d also see the elaborate
half-depth braces that alternate between the front and rear panels to create
a zigzag line for the bass wave that eventually terminate in a rear-firing
port. The pictures here clearly convey a sense of this cabinet complexity to
wordlessly explain why most manufacturers would rather avoid the topic of
transmission lines altogether. A natural byproduct of all this internal
bracing is very stout and dead cabinetry.
Kestrel TL
To test the absorptive efficacy of McGinty’s
bass loading, simply play some bass-heavy material. Park your ear at the
rear terminus of the line and compare its output against that of a classic
vented box. You’d surely notice that Pat’s rear wave is heavily
attenuated (hey, some guys are civil and don’t like to fart in public).
Besides more effectively controlling this
output than a vented alignment, a transmission line also smoothes the bass
region impedance curve and thus makes for an easier load that doesn’t
present the amplifier with large impedance swings. Those who proclaim
transmission-lines a bear to drive are cuddling up to the wrong koala (which
ain’t even a proper bear but marsupial to begin with).
Secret Chambers Even Harry Potter
Wouldn’t Fit Into
Driver rear waves are equally as loud as their
frontal halves emitted into the room. However, captured inside a cabinet
whose air volume is positively Lilliputian compared to that of the room,
these internal emissions achieve sound pressure levels far in excess
of what reaches your ears. Put bluntly, the loudest part of the room is inside
the speaker cabinet. And amidst this lethal mayhem of decibel pollution is
where most designers customarily place their crossover networks.
Ever the astute observer, McGinty had noted a
strange phenomenon very early on in his speaker builder career. As speaker
designer are wont to, he had prototype crossovers parts strewn on long
umbilicals across the floor to provide easy access for testing. Once he’d
settle on final values, he’d stuff everything back into the speaker box
for that neat and finished look consumers demand. Invariably, our surprised
designer would now detect a clear deterioration in sound quality. The
speaker with its intestines gruesomely gutted simply always sounded better.
Since messy doesn’t sell but good sound does, McGinty scratched his head
until the mystery evaporated: capacitors are highly microphonic. They’re
susceptible to external vibration and perform more linearly in an equalized
environment.
Heron crossover sub chamber
(note the binding post options to
select from one of three hard-wired
mid/tweeter filter networks)
Thinking about the consequences, Pat quickly
discarded outboard crossover boxes as aesthetic and costly boat anchors. He
also wasn’t endowed with enough Vögel (birds) to believe that prospective
buyers would fancy a very un-Italian spaghetti salad of raw parts strung
like a junkyard collar between their amp and speakers. Perhaps it was then
that every little boy’s fantasy reared its cute head – the fabulous
hidden treasure chamber. Of course McGinty-of-the-slide-ruler couldn’t
people his secret cave with wizards, dragons, damsels in distress or
glinting loot. Instead, he had to fill it with coils, capacitors and
resistors. He integrated this sub enclosure with a false bottom at the base
of all his cabinets. Connected to the main cabinet merely via the hookup
leads whose thru-holes he carefully epoxies for a gastight fit, these sub
chambers not only provide easy access to the point-to-point wired crossover
components but also create the desired equalized environment. The speaker
brain can now perform optimally and unencumbered by the headaches of extreme
decibel levels inside the speaker’s rockin’ upper story.
Sparkling Loot
Besides Auric capacitors, TARA Labs RSC hookup
wire and PerfectLay inductors (now there’s a term worthy of locker room
guffaw), McGinty pointed at heat-sinked Caddock metal-oxide resistors to
underline Meadowlark’s commitment to top drawer parts quality. To make his
point, he then temporarily transformed my slipping grip on Physics into a
ferocious death grasp to explain those miniature heat sinks. He reminded me
that as a resistor’s job is to turn power into heat – that’s how it
resists, after all – heat rises as a squared function of current.
If you’ve noted that difficult passages in large-scale material seem to
momentarily dampen your speakers’ treble energy, that’s because thermal
variations in resistors drive up their resistance values. To insure that
the tonal balance of his Meadowlark speakers doesn’t change when the deaf
get going, McGinty has implemented not only very expensive resistors but
provided a means to guarantee thermal stability.
Kite xover – note its utter simplicity
Excellent Transmission Can Be A Bad If The
Wrong Things Are Being Transmitted
While McGinty is all gung-ho on transmitting
superior bass, he’s heavily opposed to allowing his drivers, cabinet or
crucial network parts to contaminate our listening pleasure with mechanical
vibrations. Every trademark sloped Meadowlark baffle is decoupled from its
main enclosure via a 1/16th layer of Keldamp, a hi-tech material
that converts kinetic energy into heat. A blob of this stuff dropped from on
high onto the floor won’t bounce even once. It’ll just crash like a
broken egg, fully absorbing all mechanical energy injected into it from the
fall. Meadowlark employs the same Keldamp compound for driver gaskets. They
decouple the transducers from the baffle. This twin-decoupling scheme
undermines mechanical intermodulation between cabinet and drivers. The
drivers can’t talk to the cabinet, and the cabinet can’t talk back to
them – the perfect dialogue vacuum of a failed marriage. But then,
divorcing signal and distortion from each other is a good kind of terminal
separation. McGinty even mounts his capacitors on a bed of Keldamp so they
can sleep – ahem, perform -- tightly.
Trading Places
Pat had dreamt for many years of vacating the sunny but overcrowded and
increasingly hostile state of California for a place greener, more lush and,
as of late, without the weekly prospect of being shut down by power
shortages of feuding utility companies. Stemming originally from the Big
Apple, upstate New York beckoned to its wayward son with lakes, wooded and
rolling hills and a sparse population density. With less than 30,000
inhabitants, Watertown still remains a town rather than city and prides
itself on the surplus of its highly skilled labor force. The local main
trade is agriculture, particularly dairy farming, and paper mills. The
nearby 1000 Islands region of Lake Ontario also does a rather brisk tourist
trade. According to McGinty, the quality of life around Watertown harkens
back to the 60s when the daily rhythm beat at a slower pulse. Folks there
still treat each other with courtesy and respect. The word road rage or the
practices of honkin’ car horns and erectile middle fingers aren’t part
of the actual or habitual vocabulary on the streets.
Pretty much coincident with dastardly 911 of last year, the Meadowlark
team thus trekked from San Diego County to the promised land of Watertown.
Meadowlark’s new digs in a pre World War II industrial complex were
originally erected by New York Air Brake but in a very serious state of
decline upon arrival. In the words of its present proud tenant, “our
building was black and pounded to crap, with electrical and plumbing hanging
out of the ceiling and walls”. Industrious McGinty and his merry team
of veterans applied buckets of elbow grease and paint to where their new
production facility -- 150’ long, 40’ wide, even taller than it is wide
-- now provides cubits of natural light for a spacious and friendly studio
loft feel. It even retains its existing indoor lab replete with counter and
floor-to-ceiling glass front, the prior use of which a curious McGinty has
been unable to divine thus far.
Whoa: putting his new router to good use, Pat carved
wave patterns into his custom 6-inch thick ceiling
tiles to optimize his new sound room
To spare his dealers the wrath of production down time during the
relocation process, McGinty and associates had built up plenty of costly
inventory while still in San Diego. He shipped it together with all his
business equipment yonder East, two 50’ tractor-trailers just barely
housing all the essentials. He walked into the new facility October 1, 2001
and was up and running and back in production forty-five days later in mid
November.
A New Way Of Skinning Ye Ol’e Gray Cat
However, back in production isn’t quite the appropriate term.
The new facility pioneers a rather different operational concept than
Meadowlark adhered to before as a matter of necessity. As McGinty explained,
his intent for the relocation had been to double his firm’s product
offerings. He wants to invade the Home Theater arena in a serious way.
Simultaneously, he aimed at cutting inventory requirements by half or
possibly even two thirds. For those unfamiliar with speaker fabrication, the
gigantic at-odds challenges inherent in this two-pronged proposition require
a goodly explanation.
You see, most small to mid-level speaker makers really operate more as
job or assembly shops rather than full-scale fabricators. They rely on
outside vendors, usually industrial woodworking shops, to build their
cabinets. This requires committing to regular time slots, say 4 days of
dedicated company runs every 8 weeks. During these allotted periods, said
shops set up production lines for their particular customer and burn through
sheets of MDF, glue and veneer. A speaker manufacturer’s nightmare is to
run out of cabinets prior to his next scheduled run. Unless he were willing
to suffer exorbitant setup fees that might well force him to sell his
speakers at a loss, he simply can’t call up the shop to order 10 extra
pairs of anything outside his regular advance schedule, should he find
himself short a few boxes to take care of impatient customers.
If you consider a firm like Meadowlark that until recently offered five
floorstanders, one monitor and one center channel in at least four different
veneer options each, you can appreciate the massive inventory necessary to
fulfill dealer sales in a timely manner. Cabinets are by far the most
expensive part of loudspeaker manufacture. Maintaining salubrious inventory
levels of veneered enclosures ties up precious amounts of working capital.
The perilous juggle always becomes to predict how many enclosures to order
in what color and for what model. One secretly hopes that the shifty winds
of fashion and consumer demand won’t turn on a dime and invite dreaded
Murphy to interfere with forecasts. The reader should now readily appreciate
how the planned introduction of just a single new model -- yet again in four
or more veneer options -- becomes a significant financial challenge since
inventory burdens explode exponentially once more. Consider further that a
new model has no prior sales records. Order too many cabinets and watch your
money grow moss and spider webs. Order too few and undermine your marketing
efforts and the good will of developing word-of-mouth. It’s a devious
tightrope act each manufacturer must face time and again when he orders
parts from vendors.
To solve this perennial dilemma of that most severe expense in his chosen
profession, McGinty had decided to create his own fully equipped cabinet
shop. Rather than being tied up in palettes worth of paid for cabinets
produced by an outside supplier, his designs would henceforth exist only as
vaporware. They’d live on a CD/ROM file in his industrial grade CNC
router.
a sheet of complete Heron-i parts
machined to precision tolerances
His only inventory demands would be raw materials –
MDF, glue, drivers, crossover parts, shipping boxes and veneers. In fact,
his veneer options could grow staggeringly complex and his model offerings
truly extravagant. A wild-assed full-length transmission-line subwoofer flat
to 16Hz – by necessity humongous and probably only sellable in very
limited quantities to a few heroic dealers – could now become a reality
should he be thus inclined. Even as a singular and irregular order item, it
could slip into a weekly production schedule. In fact, McGinty is proud
to stress that a dealer can now order a particular Meadowlark model in any
finish on a Monday and have it ready to ship five days later.
The particular math of this surprisingly fleet turnaround works out as
follows: Cut and glue on day 1;
Joe selects and cuts veneer panels
Size and veneer on day 2;
Assemble and test on day 4;
A Blue Heron pair ready for testing
Add one day for slop, unforeseen delays or production
gremlins.
Joyce in various stages of packing
The really exciting thing about Pat’s new operation is that he isn’t
stuck to model-specific production batches. He can schedule mixes in
accordance with actual incoming orders. This fulfills the credo of the
corporate Japanese giants -- “the best warehouse is an empty warehouse”
-- a notion that simply summarizes effective manufacturing protocol: build
to order with very fast response cycles and minimal inventory liabilities.
While certainly not novel as a concept per se, to find it implemented in a
modestly sized enterprise like Meadowlark Audio is testament to the
persistence of a farsighted mind that’s not afraid to tackle serious
challenges.
Fringe Benefits
One unexpected side effect of bringing the complete manufacturing process
from raw to finished goods in-house was a significant rise in build quality.
It resulted from increased glue surfaces, tighter tolerance parts cutting
and a consequent gain in structural stability. To test a growing suspicion
that his new operation built even better cabinets than he had ever been able
to deliver before, Pat performed the famous but staged Kestrel toss of an
earlier photo caricature for real. (The photo depicts the local UPS driver
demonstrating proper delivery protocol by launching a Meadowlark shipping
carton from his van’s loading dock onto the concrete floor.) Pat now
dropped a packed cabinet from his 20’ high mezzanine onto solid concrete
embankment and only busted a corner when the entire cabinet should have
cracked open like a rotten walnut or brain on crack cocaine.
the infamous Kestrel drop (staged)/the crime for real
(note villain Joe Coleman on upper right)
Another perk of building his cabinets on-site is the
newfound freedom to throw truly extravagant veneers at them. Zebrawood,
Blue-stained Maple, Fiddleback Makore, Eucalyptus Pommele or Quilted
Mahogany? - Meadowlark is proud and capable to oblige. In fact, were you to not
find your secret fancy listed in McGinty’s multiple tiers of
progressively more exotic dress options (20 in total!), his website clearly
challenges you to ask since he can probably deliver regardless. This is
about as custom and handmade as you can get shy of commissioning an
exclusive one-up speaker. What cunning from a guy who dreamt of competing
with the big boys and now finds himself in the very thick of it not
by cutting corners but by upping the ante on quality and end user choices!
Figured Anigre
Figured Makore
Sapele Pommele
First Crop Of New Designs
To exploit his new production capabilities,
McGinty foresees a plethora of new products and possible OEM cabinet
manufacture for other speaker firms demanding consistent high-grade output.
For a sampling of new models in the birdman’s private books, watch out for
these pending introductions:
The new Heron Center Channel ($2,750)
employs the identical transducers of the floorstanding Heron-i and
positions its tweeter above the 4-inch Aerogel midrange. The famous 7-inch
Scanspeak carbon fiber woofers flank those while double U transmission
lines terminate in two round and flared ports per side. Even the Heron’s
adjustable voicing (three discrete hard-wired bass filter circuits
accessible via different binding posts that allow lean/normal/fat bass
contouring) is retained.
Two conventionally sized subwoofers powered by a US-sourced
1000-watt Class D amplifier with separate pre- and power amp plates will
go into production soon. As yet nameless, they’ll utilize the custom
8-inch woofer of the new Kite tower or the 10-inch version of the
Nightingale floorstander respectively.
On-Wall rear speakers based on the Kestrel/Shearwater and Heron
with switchable di/bi-polar dispersion patterns are forthcoming as well.
And then there is the Kite (ca.
$12,000), a floorstander only slightly larger than the Shearwater. It sports
a deceptively ordinary 8-inch three-way configuration. Then the word
ordinary vacates your vocabulary when you realize that its woofer offers 1.25
inches of honest excursion.
Kite woofer doing 8Hz @ 200 watts
/Nightingale woofer showing off its assets
A kilowatt on-board amplifier is equalized to wring a true
20Hz flat out of the bass system. Response trim pots can dial the Kite for
an earth-shaking +1dB at 18Hz response. In a canny move, the woofer amp
derives a high-level signal from the end user’s main amp that powers the
anything-but-ordinary 9800-series Scanspeak tweeter and the truly
extraordinary 5-inch Scanspeak Revelator paper graphite midrange. This
hookup scheme assures correct timbre matching since the main amp’s sonic
signature is passed on intact to the integral active subwoofer section. With
its 90dB sensitivity, the passive upper two-way could be powered with a
modestly endowed triode SET. (Tube fiends with a lust for Herculean
bass action; keep your eyes glued to this baby!)
Pat credits Thilo Stompler of San Diego based
TC Sound with the design and manufacture of the monster woofer whose bigger
10-inch cousin, in doubled-up glory, provides the devastating bass impact of
his three-piece Nightingale flagship effort.
End titles?
At the rate he’s going, certainly not – end
titles, that is. At a time when able-bodied males in my local Southwestern
Taos community beg for handouts and economy pundits predict stormy weather
ahead, Pat McGinty of Meadowlark is stubbornly pursuing the all-American
dream of the self-made entrepreneur. At the head of a small but stable
empire erected from scratch with sweat, doggone persistence and ingenuity,
he’s providing jobs for other Americans that get to work in a true
modern-day Craftsman tradition. He offers a fairly priced yet upscale
performing and looking product with more finish options than anyone else I
can think of in this industry. While he’ll never become a fat cat in this
line of commerce, he can stagger to sleep each night deeply exhausted
from an honest day of overtime work. Perhaps he dreams of his carefree days
as a beachcomber and wave glider? He wouldn’t have thought twice then
about remaining entirely unproductive, hanging for months on end as long as
it felt good. Do you think Pat made a fool’s bargain by trading that
existence for the crucible of running his present business?
Heck, at least you get to listen to a cool system
as part of your work schedule…
I think not. They say that Spirit connects with us through our passion.
And true, what fires us up does change over time and in accord with our
station and season in life. The important thing is simply to go for it when
the inner voice prompts you to, to throw your whole weight behind it
no matter what and trust that the outcome will merit the effort. In Pat
McGinty’s case, there can be no doubt that he follows this personal tenet
to a ‘T”. And that calls for applause and admiration whether you’ll
end up becoming a 1st order Meadowlark convert or not. These are
good words to tie up this two-part article and wish Pat, his wife Lucinda
and their crew ongoing success with their venture and new location.
High-Performance Audio Reviews
