New Horn Tube Amplifier

This new combo amp in the works is for amplifying stringed instruments. The cabinet follows the construction details of both the Specimen Tube Amps and Horn Speaker bases. It also uses the engine turned sub-plates for convection cooling found on Specimen’s Octoblock and the slotted side panels that were first used on Specimen’s Fifty-watt Tube Amp. You could say it’s a clever combination of several Specimen innovations all rolled into one beautiful package.

This project stemmed from a request to revisit the original Horn Amp Combo I made about fifteen years ago. This model will use the splendid Eminence 8-inch guitar speaker rear-loaded with a vertical horn. The obvious follow up to this project will be a symmetrical pair of hi-fi mono blocks with a 6 1/2″ Fostex speaker.

All that’s left to do is apply the finish to the amp and horn, wire up the amp and machine the back panel. More pics soon!


Gimbal Audio Horn Speakers taking shape, part 3

Since the Gimbal Horns are going to be hanging from the ceiling, utmost care is required for the design of the support mechanisms. Its mounting hardware is machined from aluminum rod stock. Simple details like this contribute to the structural fortitude of the final product.

In order for the mounting hardware to be flush fit to the cylinder, I created a special fixture that cuts the matching radius of the cylindrical compression chamber, ensuring a perfect fit. An indexing plate is attached to one side of the cylinder so that a hardened steel pin can fit through a press-fit bushing in the yoke and determine the horizontal orientation of the horn. Holes are transferred from a template and drilled into their respective parts.

Below is a slideshow of photos taken during the building process. Check our my other Blog posts for more information and photos about this newest Specimen.
Gimbal Audio Horn Speakers taking shape, part 2
Gimbal Audio Horn Speakers taking shape, part 1


Gimbal Audio Horn Speakers taking shape, part 2

The Gimbal Horns are so named because they are adjustable on two axes. They are ceiling mounted and this exploits a part of interior architecture that is often overlooked.

These horns are being made in our usual fashion – bending recycled newsprint over a steaming iron using a mandrel. The panels are then glued together and reinforced with dryer lint. Special alignment fixtures assure correct orientation of the mounting flanges. The cylindrical compression chambers are laminated together using birch wood wrapped inside a jig using an inflatable ball as a clamp. This forms an extremely rigid platform for the driver and horn.

Here is a slideshow of photos taken during the building process. More info and photos about this project can be found in my other Blog posts:
Gimbal Audio Horn Speakers taking shape, part 3
Gimbal Audio Horn Speakers taking shape, part 1


Emerald Deluxe Custom Guitar for Alex Kapranos

My newest guitar is for Alex Kapranos, guitarist for the Scottish band Franz Ferdinand. When Alex and I met to discuss the project, he told me of his life-long fascination with the beetle, especially certain blue-green beetles with their iridescent wings. We decided this guitar would have an entomological theme.

I designed the pickguard using 600 beetle wings, layed up like roofing tiles and embedded in epoxy resin. I posted an earlier Blog post about the making of this pickguard including pictures taken during its creation.

Below is a slide show of pictures documenting several other building processes including: shaping the neck, inlaying custom beetles made from abalone in the fretboard, routing out the body for the pickguard, carving the comfort contour on the back of the body, etc.

You can learn more about this guitar, see photos of the finished instrument, and videos of the band here.


Tube Amplifier Building Weekend Seminar

This seminar will teach the fundamental construction skills necessary to assemble and properly wire a Fender-style tweed tube amp. Utilizing amp kits, students build their own amp all under the helpful eye of the instructor.


This workshop will be divided into part lecture, part demonstration, and part hands-on training. Over the duration of three days, students will observe stages of the kit building process and then carry out the work on their own amps under the supervision of the instructor. While this is not a design class per se, students will obtain a foundation level understanding of the way a vintage tube instrument amplifier functions, stage by stage. Students will also learn the craft of point-to-point wiring and how to modify a circuit to shape its tone by changing component values. Moreover, by building an amplifier, students will begin to develop the diagnostic skills necessary to troubleshoot and repair other amplifiers.

This is an ideal seminar for those working as a guitar technician, roadie, music store employee, touring musician or for anyone interested in working on instruments. Useful handouts will be provided and a Certificate of Completion will be awarded to all students who complete the course. Enrollment is limited to 8 students.

Students have the choice of building one of the following amps:

  • Tweed Champ (10-watt)
  • Tweed Deluxe (15-watt)
  • Tweed Bassman (50-watt)

For first time builders, we strongly recommend the Tweed Deluxe kit. It is the perfect level of involvement for the three day seminar. If you are a first time builder and have your heart set on one of the higher-powered models, simply bear in mind that some additional hours may need to be logged to complete the build.

The kits are supplied by Mojo Music. The parts included are excellent quality and the cabinets are pre-assembled and beautifully covered in authentic tweed fabric (or authentic Tolex for Marshall) . Every aspect of the kits is as faithful as possible to the original design. Each kit comes with its own schematic and layout diagram (there are no assembly instructions included).The legendary circuits used in this seminar are the same ones that have made true “Tweed” era amplifiers so revered among musicians. These amps are bullet-proof workhorses that are easily serviced, modified, and maintained. Through this workshop, students will discover the beauty of cloth-covered wire, heavy transformers, chassis-mounted components, and finger-joined pine carcasses.Click here to visit Mojo’s web site and read more about the kits and their contents. Our kit prices include shipping to the school and the kits Mojo makes for our school include upgrades to certain better quality components and more sensible features. Also the school pre-drills all the chassis and motherboards to prepare them for the seminar.

NOTE: We are combining this seminar with our Hi-Fi Stereo Tube Amp Building Seminar. By combining these seminars, students have the opportunity to learn/observe both traditional point-to-point construction and the classic Fender/Marshall motherboard construction. All the tenets of lead dress (wiring) remain the same regardless of what method is used.

Workshop Materials and Supplies

The school will provide each student with their own individual workstation and all necessary tools. Students can select which amp kit they will be building. The workshop fees listed include the class fee and the amp kit fee. Payments for both the class and the amp kit will be made to Specimen at the time of registration and all amp kits will be shipped directly to our shop.


New Luddite bass guitar in the works

The Luddite Bass is an obvious next step for this growing family of Specimens. It enjoys all of the same attributes as our other Luddites: non adjustable steel truss rod; slotted headstock; 12th fret body join; no cutaway; simple control circuitry. It has a 32″ scale length and Gibson EB-style bass pickups with an additive Jazz bass-style circuit with no tone control.

Lately I have gotten away from plastic binding and begun to use wood. Believe it or not it is actually easier and less stressful to steam bend the wood and glue it to the body than it is to race the solvent-based cement as it melts the plastic binding. Aesthetically it is beautiful as well.

Click on our slideshow below for some ‘under construction’ photos taken of this newest Specimen. By the way, I am looking for a band to equip with all Luddite instruments. I think it would make an excellent stage presence.


Gimbal Audio Horn Speakers taking shape, part 1

The Gimbal Horn is Specimen’s newest horn speaker. This speaker will be mounted on the ceiling and suspended using a yoke so that it can ‘gimbal’ (or rotate up and down and side to side). It seemed to me that the space near the ceiling is underutilized real estate in many architectural interiors. The Specimen Gimbal horn will bring beauty and utility to a part of the room that is often overlooked.

This horn speaker is front loaded and therefore will project in a more direct way than the more spacial sound stage of our Specimen rear-loaded horns like the Little Horn Speakers and Liederhorns. This makes these Gimbal Horn Speakers aptly suited to front of house or PA applications.

The horn will be mounted to an aluminum yoke that suspends the cylindrical compression chamber from the ceiling. The horn can be positioned at any angle or rotated to suit the application of the room. We decided to utilize the wonderful and recently rejuvenated foundry facility at the Memphis Metals Museum. Located right on the Mississippi river bluff, it is the perfect setting for creating something using the age old technology of sand casting.

After making a wooden pattern to mount on either side of a backing board, runners and gates are added to allow the metal to flow and shrink. Sand is then packed into both sides of a two-part flask to prepare the mold for casting. Metal is then melted in a crucible inside a furnace and poured into the mold. Voila! Beautiful aluminum yokes for the newest Specimen Horns.

Below are some photos taken while I was at the Foundry casting the first yokes. Thanks to Doug Barton and Holly Fisher and everyone at the Metals Museum for all their help taking on this special project.

Below is a slideshow of photos taken during the building process. Check our my other Blog posts for more information and photos about this newest Specimen.

Gimbal Audio Horn Speakers taking shape, part 2
Gimbal Audio Horn Speakers taking shape, part 3


Penland School of Crafts – A Mountain Oasis

At the beginning of April, I spent a week at the Penland School of Crafts, where I was invited to be a visiting artist. I have hung out in many foundries and ‘smithees’ in my time, but I have never been a teacher in an iron-working class before. The class was an 8-week concentration, and when I arrived the students were at the mid-way point in an assignment involving gears and a lever—this is why I was brought in.

Even though I am not an iron worker, many of the geometries and design processes of iron work overlap with the discipline of luthiery and kinetic sculpture. Much of the time I spent with the students involved a good deal of mechanical problem-solving and the bringing of wild concepts into the physical world. For example, we logged a few hours pouring over McMaster Carr’s web site shopping for collars and shafts, springs, gears, and other raw materials. And throughout each day, we dove rather deeply into topics such as axles, rotation, spring action, turns ratios, transfer of power, and the animation of sculpted objects. We conjured up shapes and mechanisms together and it was quite gratifying to see the student’s projects begin to take flight. We also found time to make Hornlets which allowed for demonstrations of my processes and work methods.

Immediately upon my arrival, I presented a slide show of my work to an attentive audience, trying to connect the dots between my past and present. In preparation for this, I scanned 38 sketch journals and 800 slides from the last 30 years of my work. This was cathartic, to say the least. As I looked into the past, it seemed so easy to identify the recurrence of themes and shapes that I am still using today. My fascination with the octagon, for instance, began 30 years ago when I was an undergrad at the Memphis Art Academy.

The campus at Penland is like an oasis of so many different mediums: books and paper, clay, drawing and painting, glass, iron, metals, photography, printmaking, textiles, wood, and other media. The collective efforts of the entire community at Penland creates an amazing energy. This was especially evident during mealtimes when everyone stops working and gathers to eat splendid dishes prepared by the students. In the evenings after diner, we would all convene again for a slide presentation of work from various departments and teachers.

Penland is truly a magical place, and on a mountain top to boot! I think I will need to visit again.


Epiphone Zephyr Neck Re-set

This gorgeous instrument is an early one (1940s). It needed a neck reset and a re-fret. There was enough break angle over the bridge and the neck pitch was fine. The problem was that the stock pickup was too tall and non-adjustable. I tried to remove it to sneak a little material off the bottom, but this pickup is a juxtaposition of separate parts sandwiched together by the cover. Age has shrunken some parts together while others are still loose. This created a scenario that severely endangered the bobbin. Because I did not want to destroy this great sounding pickup, I slowly retraced my steps and reassembled the unit. The only solution was a neck reset.

The dovetail was very close fitting and there was hardly room for my steam needle in the joint. It came out well enough after a bit of persistence. I changed the neck angle by re-carving the cheeks and dovetail and re-glued the neck. A complete re-fret was then carried out. The instrument gained even more volume from the enhanced pitch and played beautifully.

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New Video of Upside Down Spinning Double Horn Speaker

This amp looks like it has been in a time capsule. I would guess it is from the early to mid-1940s. Anybody out there have a clue? The tubes are unfamiliar and the socket pin count is squirrel-y, with extra cap connectors on some of the tubes. Each tube also has a three piece “man in the iron mask” shield that clasps around it.

The construction is so bullet-proof that it is no wonder it survived. It has a field coil speaker that predates the common use of permanent magnets. This field coil also doubles as a power supply choke. Ingenious! Beautiful simplicity, and it sounds terrific to boot. Gutsy, yet open.


Making 3-D Checkerboard Binding for Custom Tele

This Tele-style instrument is a commission for a local guitar player. It has an alder body with a book-matched flame-maple cap. We wanted to take this traditional instrument in a special direction so the guitar will feature custom-made checkerboard binding, square fretboard inlays, orange-into-walnut sunburst, and Lindy Fralin pickups with a 4-way circuit.

To create the binding, I first made up checkerboard tiles from rosette sticks. I ripped two different sized slots in a solid chunk of Teflon (even super glue is reluctant to stick to this material). After staging my sticks strategically in the Teflon slots, I impregnated the bundles with super glue. After it set, I managed to remove the logs. Then after sanding them, four quarter logs are placed in the larger slot and the process repeated.

I used a small mitre box to cut 2.5mm tiles from the logs. These are then individually tapered in order to negotiate the guitar’s curves. There is actually a hidden inner rivulet of alternating cubes inside the checkerboard.

Below is a slideshow of images detailing the binding process.


Making Custom Beetle Wing Pickguard for Alex Kapranos’ Guitar

[F]or an entomological bent on this very special commission for Alex Kapranos of Franz Ferdinand, I created a pickguard using 600 emerald beetle wings infused with urethane resin. The process is very involved and required making many test samples before embarking on the final form.

The first consideration was how to juxtapose these wings. The thickness and curvature of the pickguard shape posed a challenge. I didn’t want to break apart the wings as they would lose their identity. Topologically, they resemble miniature ceramic roof tiles, so I decided to interlay them just like roof tiles to form a continuous covering. Perfect!

I embedded the beetle wings in epoxy resin using a vacuum pump. Once in place, a perimeter mold is cut out and screwed down onto a Formica platter with mold release compound on it to ensure separation at the end of the process. Cup by cup, resin is catalyzed and put in a vacuum chamber to de-gas it and remove all the tiny bubbles. It is then carefully poured over the wings.

The overall thickness of the pickguard grew to a formidable 3/4″. Since I wanted to keep the guitar a regular shape so it would feel ‘normal’, I had to rout the body and deeply embedded the pickguard into the guitar’s body (another engineering challenge!). Once installed, only 1/8″ of pickguard protrudes above the body’s surface where it is beveled like an ordinary pickguard. This overall effect gives gives the pickguard a three-dimensional wing-scape.

Below is a slideshow of images showing the pickguard making process.

Check out my other Blog post documenting other building processes. You can read more about this guitar, see photos of the finished instrument and videos of the band here.