Linkwitz Orion speakers: 7-yr itch?

MikeC's Audio Craft

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.

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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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