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Linkwitz Orion speakers: 7-yr itch?

Before I could embark on any turntable projects, I had to clean out the garage, and get rid of the parts for a speaker project I started seven years before. It turned into a 4-month job and I ended up with a tidy garage full of tools, and a speaker system better than anything I’ve had before.

Some of you have undoubtedly seen or read my Introduction
to this section and the Blond Baltic Birch Lenco
. What I didn’t tell you
there is that my desire to remake Lenco turntables could not be realized without
some preliminary tasks. There were several, all to do with the workshop in the
garage:

1. The garage had to be cleaned out. This meant sorting through and either
discarding, selling off, or otherwise dealing with a dozen cartons containing
all manner of parts, doo-hickeys and other gems from my audio store days.
My ’80s audio venture had a full service/repair section, and its inventory
somehow befell me when the store closed. Also in the garage was a huge pile
of odds and ends from house renovation projects, cartons containing SPCR reviewed
goodies going back a decade, and other stored and discarded paraphernalia
of “modern life”.

2. There was a pile of Baltic Birch plywood of various thickness, a big box
of 10 speaker drivers, an 8-channel Rotel amplifier, a custom 3-way stereo
electronic crossover, and other sundries which represented 95% of the parts
and supplies needed to build and drive a pair of Linkwitz Orion speakers.
I had purchased and stockpiled these back in 2007, with a total expense exceeding
$4000. What with the pell-mell pace of life and the demands of SPCR, I somehow
never found the time to embark on this project.

3. A new table saw was needed, along with a good router and a compound mitre
saw. Then a sawdust collection & air filtration system to reduce the risks
to my (and others’) respiratory system. All of the above needed to be cleared
to make room for these tools, and for working space around them in the garage
space.

Only after these prerequisites could my Lenco projects begin.

It took over two months to accomplish the first step, by which time, I was
near exhaustion, but finally there was room enough to get some of the new tools
into the garage… new for me, at least; some were used, but in good condition.

The next obvious step was to finally build those Orion speakers and make yet
more room. It was a roundabout way to finish a project initiated seven years
earlier, but life often takes us on odd twisting journeys.

MY ORION 3 SPEAKERS


Finished, in LR with 8-conductor 12-gauge speaker cable in background,
near Rotel 1048 8-ch amplifier. Each speaker requires four separate channels
of amplification: One for the tweeters, one for the mid, and one each
for the two 10″ bass drivers.

There are two tweeters, one firing forward & one backward. They
are wired in parallel, in reverse polarity from each other. The midrange
and bass drivers are not enclosed; they are supposed to radiate equally
in both forward and backward directions, although the basket or frame
of the driver prevents the back wave from being identical to the front.

The curves on the side panels are mostly cosmetic. The original design
called for a more rounded look. I elongated the curves slightly to make the speakers
look taller and less tubby, on request by my beloved, Betty, who thinks the original curves make them look like penguins.

You see the full driver complement from the rear. The Peerless woofers
are quite massive, and they are wired out of phase so that their cones
move in the same direction. This setup is meant to cancel out whatever
vibrations are created in the woofer frames. An 8-conductor Speakon connection
eases hookup, but both the female and male sides of this connection were
complete pains to solder up.

An electronic crossover, which I purchased fully assembled from Linkwitz,
divides the stereo signal from my preamp (or sound card or DAC) into three
bands for bass, mid and treble for each channel. The crossover points
are roughly 120 Hz and 1440 Hz with fairly steep slopes (24 dB/oct). Each
of the woofers gets a single channel of amplification to itself. The direct
connection between each driver and its amplifier assures the best, most
direct signal transfer and minimal loss.

This is a fairly late stage in the 6-7 week building process. The bass
driver mounting structure has been assembled and painted, along with the
mid/treble baffle, and the side panels have been cut and attached. Those
curves were difficult to replicate exactly on on four separate boards.
Almost all the wood is 3/4″ Baltic Birch plywood. Note the solid
block of wood on the left “box”, with a metal rod sticking out.
More on that below.

Internal frame, and a template jig for the side panel cut from pressed
board on the left.

The midrange driver, an aluminum cone 8″ Seas, is not attached
to the front baffle at all. Its flange rests lightly against a weatherstrip
foam around the mounting hole. The real support is the block of solid
wood. A threaded steel rod is used to clamp the speaker tightly to the
wood block, which is glued and bolted very securely to the top of the
bass “box”.


Here’s how that midrange driver is mounted. The copper phase cap in front
screws into the speaker. On its flat back side, the copper phase cap has
a threaded hole which matches the threaded rod that is securely attached
to the aluminum block, which again is solidly anchored to the front of
the wood block. The pole piece and magnet is vented with a hole, and the
steel rod goes through it to the front. When the copper cap is screwed
in place tightly, the speaker is firmly supported by the wood block. It’s
only after the speaker was bolted to the wood block that the wood block
was affixed permanently to the top of the bass box.

All this is to prevent vibrations in the front panel from reaching the
midrange cone and vice versa (midrange driver vibrations from getting
into the front baffle and affecting the tweeters). Of course, some vibrations
from the bass box also have to be reaching the midrange driver through
the wood block, but the midrange driver frame is much less likely to ring,
clamped as it is to the wood block.

 


The source of the system is a Window 7-64 PC running JRiver, a music player
software. All 33,000 music files are on a 2 TB WD Red hard drive barely
half full despite the presence of many 24/96 and higher res pieces, backed
up to the network server. The signal path: PC/JRiver >> external
DAC >> electronic crossover >> 8 channel amplifier >>
Orion speakers. The big LCD TV, bought used at modest cost, is simply
a monitor for the PC, on only when the audio system is used.

How does the system sound? It’s still not the same as live, but the illusion
is better and more authentic than anything I’ve ever had in my home before.
The high quality of the sonic reproduction is easily perceived by everyone who has heard
them. Occasionally, people come to my door when the system is playing music upstairs, and many ask, “What is it you have playing up there? It sounds so amazing!”

SIEGFRIED LINKWITZ & THE ORIONS

Siegfried Linkwitz, who worked as a test equipment design engineer with HP,
was also an avid audiophile and tinkerer. He’s been seriously involved in his
avocation since the early 60s. I first came across his name in the byline of
an article about a sophisticated DIY 3-part speaker system with time delay and
electronic crossovers, first published in Wireless World magazine in 1978, then
reprised a couple years later in Speaker Builder magazine (to which I also made
a few minor contributions). Copies
of both articles
are available on the linkwitzlab.com web site. The speaker
system SL described was extremely advanced in its day, especially for a DIY
designs, and it could still be considered advanced today. His work with crossover
design led to the naming of one particular type as Linkwitz-Riley, which is
known to virtually any consumer (never mind student) of serious speaker systems;
Riley was the name of one of his long partners in audio.

So when I came across references in the mid-2000s to a new DIY speaker design
by Linkwitz, I was intrigued. The Orion veered significantly from his 1978 3-enclosure
design, but it had some of his trademarks: Electronic crossovers and multiple
amplifiers; steep crossover slopes, and electronic equalization to smooth frequency
response; a focus on controlled directivity and top quality drivers. The most
significant change was an open baffle, dipole design. For full details about
the Orion design, I refer you to the source at linkwitzlabs.com,
but I’ll try to summarize here.

THE BACK WAVE

Some background: A big part of loudspeaker system design (not drivers
but speaker systems, which usually includes several drivers in an assembly
or enclosure) can be summed up in one question: What to do with the back wave?

Almost all speaker drivers radiate sound in two directions, forward and backward.
The sound in those two directions is 180 degrees out of phase; the “back”
wave” is always half a cycle behind the front wave. A full single cycle
(ie, think sine wave) of a sound involves the speaker cone going forward, then
backward and then stopping at its neutral center point. Where (and when) the
two opposing out of phase signals meet, there is a null, or cancellation. It
happens more at lower frequencies, which radiate at wider angles. As frequency
increases and wavelengths shorten, cancellation reduces and it disappears altogether
by say 5 kHz or so. Below 200 Hz, the cancellation is much more significant
and very audible.

The simplest way to deal with the bass-killing back wave is to prevent it from
meeting the front wave. The very first speaker systems did this by mounting
on a large baffle. Make the baffle big enough and the time it takes for the
back and front waves to meet is long enough that the note has already decayed
and dissipated, thus minimizing any cancellation effects. In early audio days,
this concept was stretched to an “infinite baffle” where the speaker
was mounted in the wall, and the back of the speaker faced another room sealed
acoustically from the listening room. Workable in big houses with lots of rooms
(where the upper crust audio enthusiasts of the day resided), but not so workable
today. The term infinite baffle came to mean any sealed box with a very large
volume (compared to the volume of the air the speaker could move).


The last successful classic open baffle speaker system was probably
the smallest: Wharfedale SBF/3. SBF = Sand Filled Baffle. Dry sand sandwiched
between two sheets of plywood.

Shrinking the big baffles and enclosures was a major concern to make audio
hifi more user friendly. The Wharfedale SFB/3 introduced in 1956 was probably
the last successful classic open baffle speaker and about the smallest, but it
was still nearly a meter wide and 80cm tall. The bass reflex or ported enclosure
was one of the paths to reducing enclosure size. In essence, this design uses
the back wave of the driver to reinforce the front wave with a tuned resonant
port. The acoustic suspension sealed box was another way to shrink the box.
The driver needed to be very compliant and have a low resonant frequency, and
mounted in a relatively small sealed box, typically under 2 cubic feet. The
air in the enclosure would become a spring controlling both forward and backward
excursion of the driver and “stiffening” suspension of the driver
(hence the term acoustic suspension). I only mention a couple other enclosure
designs without delving into them, horns and transmission lines, because neither
really did much to shrink the size of the speaker system, except with small
drivers and/or the folded horns.

Today, outside the stratospherically priced exotica in high end audio, virtually
all consumer speaker systems are either ported or sealed enclosure designs.
Their relatively small size, simplicity and ease of simulation
with computer modelling have allowed these designs to dominate.

INTERNAL PRESSURE

One of the big complications with enclosing the driver, especially a bass driver,
is that the whole box as well as the cone itself is subject to pressure from
the movement of the driver. When the cone goes in/out, there’s air compression/expansion,
which pushes and pulls against the driver cone itself and subjects the entire
enclosure to vibration. The need to minimize this effect is what drives high
end speaker system makers to use heavy, stiff, dense materials braced extensively,
with heavy damping on the inner walls, etc. The materials designers have used
to try and keep the enclosure inert include MDF, sand filled plywood panels
(Wharfedale), aluminum honeycomb composite panels (Celestion), concrete/fiberglass
(B&W), all-aluminum (YG Acoustics), and mystery composites (Wilson Audio).

In contrast, an open baffle speaker driver is completely free of pressure against
its “natural” movement other than the air in your room, and only its
baffle needs to be stiffened or braced against unwanted movement and vibration.
Leaving the drivers unenclosed dispenses with all the convoluted, expensive
engineering to keep cabinet resonances and vibrations down.

Back to the Orion speaker system: What are the reasons for Mr. Linkwitz’s move
back to the ancient open baffle design? Well, there’s the pressure issue I just
described, for one. And many others.

MODERN OPEN BAFFLE, DIPOLE DESIGN

Many significant changes have occurred since the first realization of open baffle
speaker design a century ago:

  • Speaker drivers have become far more powerful and efficient. They can play
    louder and survive more electrical power than ever before.
  • Amplifiers have become many times more efficient, powerful and clean. They
    can deliver enormous amounts of power to the speakers with vanishing distortion
    levels.
  • Electronic crossovers, which divide the audio band before the signal
    is amplified, and send them to separate amplifiers for bass, midrange and
    treble drivers. They provide a level of precision that is difficult to achieve
    with conventional passive crossovers that sit between amplifier and speaker.
    Electronic crossovers also allow precise tailoring or equalization of the
    signal for all kinds of audio compensations.
  • The narrow baffle allows for better dispersion at higher frequencies.
  • The dipole characteristic extended up to the entire audio band allows natural
    rear reflections that can greatly enhance the illusion of depth and space
    and sonic “imaging”.

The Linkwitz Orion speaker system takes advantage of all of the above in a
well-integrated package. When set up optimally in a room that’s large enough
to allow plenty of space around, and especially behind, the speakers, with proper
amplification and sources, the sound a pair of these systems can project is
instantly engaging. They sound pretty good at low levels but like all systems
worthy of the term high fidelity, sound best at levels closer to the original
performance (which usually means pretty loud).

An aside: After a lifetime of listening to both live and canned music,
I’ve come to the realization that authentic reproduction of music cannot ignore
volume. There is simply no way that even a single violin or singer can sound
authentic when played at 70 dB for background music in a living room. A live
violinist or singer can easily produce 90+ dB in an instant, then drop down
to a bare whisper in the next instant. The dynamic quality of the music cannot
be reproduced if the peaks are held to say 80 dB, which forces the pianissimo
to barely audible levels. Volume defines scale, and without scale, there can
be no authenticity.

The Orions are superb speakers, the best I’ve had in my own home system, but
they are not flawless, perfect or ideal for every setting. Naturally, I have
some other speaker projects in the works.

* * *

SPCR articles of related interest:
MikeC’s Audio Craft:
An Introduction

Paradigm Millenia HT
Speaker System
Squeezebox 3 Digital Music Box
Audioengine A5+ Speakers
and Wireless Audio Adapter

AudioEngine
A2: Little Big Speakers

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