Subtly Steampunked CBT36 line array

Subtly Steampunked CBT36 line array

Left Channel (5′ full height)

This is a CBT36 line array speaker. It was built from a kit that contains unfinished speaker cabinets, drivers, and electronic components suppied by Parts Express. The design is by Don Keele of Audio Artistry and is unique in it’s use of five shaded line array banks that produce an impressively even stereo image throughout the listening room. “CBT” stands for Constant Beamwidth Transducer. The “36” refers to the number of 3.5″ full range drivers in the speaker pair. Each speaker contains 90 drivers (18 x 3.5″ full range drivers and 72 modular tweeters). The speakers are bi-amped, running off of a modular set of four 250 watt amplifiers and a programmable external speaker management system for cossovers between the tweeters, full ranges, and subwoofer.

Most of my custom work focused around custom cabinet finishing and hardware. All of the examples I found of finished CBT36 cabinets showed glossy coats of paint on the front panels, which didn’t appeal to me. I wanted more of an old school look with mahogany and brass bolts. I stained and buffed the wood veneer with fine grit sanding, steel and carnuba wax. The end result looks sort of like shiny brushed copper at a distance.

Unfinished cabinets

The unfinished cabinets are shipped with the front panels bolted on for safer shipping. The undersides of the front panels are extremely delicate where they have been precision machined to accept the tweeter arrays at very tight tolerances. In some places the MDF is no more than a millimeter thick, and can be easily damaged by pressing too hard into it. Luckily, these parts of the front panels get protected both by hardware and the fact that they are all internal structures.

Notice I received two identical right enclosures. Parts Express was extremely helpful with resolving this issue quickly so that I could start the project as soon as possible. Although the front panels are interchangeable (before mounting), the cabinet enclosures are not. Left and right cabinets have pre-drilled holes and hardware attached at specific locations so that the full range drivers line up inside the tweeter arrays. This becomes important for Phase correction when the external crossover is calibrated for left and right speaker arrays.

Cabinet bottoms

This angle shows the pre-drilled holes at the bottom of the cabinets which will mount the speaker cabinets to thier bases. Inside each cabinet is permanently fixed hardware that accepts the bolt threads for all the attached components (mounting brackets, cable routing, and panel bolts). Also visible are the internal walls that isolate the internal tweeter sections from the full range driver sections. This is needed so the air pressure generated by the full range drivers does not interfere with the operation of the tweeter modules. The final cabinets use additional sealing foam (provided in the kit) to completely seal off the airflow between the two sections after the front panels are re-installed with all the drivers attached.

The kit also suggests using speaker putty to seal the cable routing holes, but I substituted hot glue instead because I have had problems with speaker putty staying put and giving an airtight seal if there is no compression involved.

Veneering process

The front panels have to be completely finished before any of the speaker work starts. My veneering process involved a bit prep work before that could begin. I created a guide for outlining each of the 36 circular panel inserts for the full range driver openings. The work surface, materials, and tools for doing this are seen here. The adhesive mahogany veneer can be ordered through Rockler Woodworking and Hardware. I applied a heat source after mounting to cure the adhesive to the porous MDF. The bladed compass scored the veneer surface before cutting with the Exacto blade. The razor blade was used to trim the veneer after mounting it.

 

Front veneer cutting

The rest of the veneering was prepared by transferring the front panel hole positions to the veneer using an airbrush.  I sprayed black ink carefully around all of the holes with the panel in a flipped position. To keep the panel firmly applied to the veneer while spraying I used a series of 10lb lead weights I could move and position as I sprayed without shifting the panel.

I cut slightly inside the transferred pattern on the veneer to keep some excess material for mounting. This allowed for small corrections in alignment during mounting and final trimming. Notice the six uncut tweeter holes in the bottom left of the image. These show the airbrush pattern that was transferred before cutting. I used the red hole punch to make the smaller cuts for the tweeter holes and bolt holes, and the Exacto blade to make the larger cuts for the full range driver holes. The Optivisor was handy for precision work. The blue towel protected my hand from the bolt at the top of the hole punch handle. Typically the hole punch is struck with a hammer, but I got better results through applying even downward pressure with my body.

Trimming process

This is a close up of the trimming process I used for the internal circular veneer sections on the front panels. I had to carefully follow cuts perpendicular to the grain of the wood so as not to cut into the MDF. As I approached the midpoint where the grain aligned with the cut I had to use extra caution not to overcut the veneer and damage the MDF. This is where I relied upon my Optivisor and a steady hand to methodically complete each cut. The second cut to the interior of the veneer was even trickier because there was no flat surface to brace the cutting tool against, so I had to make each of those cuts with the Exacto blade instead of the razor blade. A portion of a fully finished cut can bee seen in the upper right of the image. Each section took approximately 30 minutes to complete, so all 36 sections represent about 18 hours of work. I didn’t have to worry about rough edges at this point because the top veneer would cover the cut edges of the circular sections.

Trimming pt2

The mounting and trimming of the front panel veneer was done in the same fashion as the circular sections. Also notice that I folded the veneer around the edge of the front panel to follow the rounded cut on the edge of the front panel. A hot iron was run over all surfaces to cure the veneer adhesive, especially along the rounded edges to relax the bend and keep the veneer from splintering at the fold. All trimming was done with an Exacto blade because I could not rest the blade or the panel on a flat surface to make accurate cuts. All rough edges can be seen because I have not done sanding on any of the surfaces at this point. This trimming process also represents about 18 hours of work.

Grinding

The smaller tweeter holes allowed for a faster edging process with a power drill and grinding bit. I used the grinding bit to remove the excess veneer on each of the holes, enlarging them to the point they were before the veneer was mounted. This grinding process also had the added benefit of pushing the veneer edge down into the holes to cover the interior MDF. Extreme caution needed to be used to avoid punching completely through and removing too much material, so I took my time on each speaker hole (about 5 minutes). Five minutes may not seem like a lot of time, but it added up to about 12 hours work for 144 holes, and was the most nerve racking part of the prep stage because it was very tempting to rush through this part. I had already invested about 50 hours and a considerable amount of money on the kit and materials at this point. One mistake on any tweeter hole would have ruined the entire project.

Sanding

Here is a close-up of a panel section after a few passes in the sanding process. Most of the rough surfaces have been removed and I have begun to smooth over the seems to blend them as much as possible into one another by removing any material that visually shows any edge overlap. There was not a lot of risk at this stage because no power tools were used. A simple sanding block took care of the flat surfaces and the rest was done with hand sanding.

Staining

The final finishing stage involved a light staining of the mahogany to bring out the texture in the woodgrain. That was followed by a pass of clear poly coat that I took all the way back down to bare wood with 600 grit and 1200 grit sand paper. The poly coat still filled the pores in the woodgrain so that final sanding could achieve as smooth and uniform a natural surface as possible without a loss of grain texture, which I didn’t want. Final buffing of the wood surface was done with carnuba wax. This is typically used to protect pool cues, which need to be clean and smooth for best results. It makes any wood surface slippery to the touch, and protects it from dirt and dust. It also gives the wood a very pleasant camphor smell to it.

Driver installation

At this stage the front of the panels are completely finished and flipped over. I have transferred them to another workstation with a felt surface that protects them from damage or abrasion as I work on mounting and wiring all the driver arrays. The kit comes with a manual and wiring diagram, seen in the center, so I’ll skip over most of the wiring and speaker installation process since it can be read in the manual. The local electronics store also gave some great advice for quick release connects that may come in handy if I ever have to do any maintenance work on these beasts.

Hot glue substitute

The CBT36 Line array manual instructed me to use hot glue to route wires and mount resistors on the sides of driver magnets and circuit boards, but I read in some forums that a better and more secure way to do this was with zip ties and and mounting brackets. The whole idea behind this type of mounting is to eliminate any type of vibration in any of the components that might interfere with playback. I took this a step further and mounted adhesive speaker foam in between any hard surfaces that could transfer vibration and loosen components.

Final touches

The black bolts that came in the original kit I noticed had a very narrow flange and bit into the MDF they were holding down. I didn’t want to damage the work that I had done on the front panels by installing them, so I found replacements at Home Depot that had a much wider flange and the added bonus of the brassy finish I was looking for. Additionally, I added a rubber gasket under the flange to prevent loosening, air leakage, vibration, and biting into the wood. The gasket compresses, filling the area between the hole and flange with a protective air tight seal. The painful part of this hardware substitution was that all 40 bolts had to be ground down to the proper length, so they didn’t bottom out inside the cabinet. That involved about 12 minutes of work on 40 bolts for about 8 more hours of work. With everything added up, it probably took me about 200 hours of work to complete the project including speaker testing.

Speaker testing

Here is a final image of the left CBT36 Line array being tested with a 150 watt test amplifier and my iPad running a frequency modulation and testing app. Not all of the front panel bolts are installed because I was still making final checks in wiring and enclosure testing before sealing up the cabinets permanently.

Steampunk Wacom, Part 1 (The Stylus)

Steampunk Wacom, Part 1 (The Stylus)


The inspiration for this Steampunk Wacom stylus (and soon to be completed tablet, Part 2) was born out of two events that coincided a few years ago. One was the fact that every so often I need to upgrade my equipment to support new software and features. The other was a chance find of an antique lap desk at the local swap shop (technically, the dump) around the time my Intuos 2 became a dust gatherer. I hate getting rid of graphics stuff like this so “What to do with it?” was top of mind.

A lap desk is a throwback to a Victorian era travel necessity for any well connected globe trotter that needs to keep up with correspondence. Perhaps a lap desk could be considered the laptop of the 1800’s. It certainly makes sense based on name and function. The surface layout of a Wacom tablet (especially an Intuos 2) is remarkably similar to the divide between the richly veneered wood and felt on the business surface of a lap desk. There are also cool compartments that come along with a lap desk design that can serve as storage space for a stylus and those tiny tips that I keep losing. Although in disrepair, I didn’t want to cannibalize the lap desk for parts since it was nearly intact and a little on the small side. Instead I began a slow and methodical process of selectively collecting objects and materials I could use and re-manufacture into like components, all from recycled parts of course!

 

Original Intuos 2 Stylus

Original Intuos 2 Stylus

I worked first on the stylus (unmodified original shown on the left) knowing that this would be the most intricate work. Must-have materials in any good Steampunk creation are always brass, wood, and leather.  This led me to work out a design for the stylus based off of airbrush, fountain pen, and clock parts which I had lying around. The stylus has three controls other than the tip. The rocking button in the middle of the stylus looks like a single slim button, but once one gets into the guts of the stylus it is clear that the button design triggers two independent toggles on the internal circuit board. The third control is the digital eraser on the back end of the stylus.

 

Trigger assembly close-up

A rocking motion is an ideal movement for dual trigger mechanisms found on most airbrushes which is why I chose to modifiy the rocking button assembly by mounting a trigger from an old Passche airbrush on top of it. See my Custom AB post for comparison with the image above. This actually works better for me since the trigger puts my finger in a more relaxed position above the stylus, and I don’t have to move my finger to opposite ends of a button bar to toggle the two controls. Instead I just use the trigger’s rocking motion the same way I would control paint flow on an airbrush. Coincidentally I also happen to own an airbrush version of the Wacom stylus which is even more awkward to use than a traditional button stylus. I was always baffled by Wacom’s choice of a hybrid mouse wheel over a traditional airbrush trigger on that device. Wacom built pressure sensitivity into the stylus tip. Why not do the same for virtual paint flow on a trigger?

 

Tip assembly close

I chose 1/2 inch brass tubing for the stylus body and discovered early on that any type of metal at the front of the stylus interferes with the signal reception at the tip. I changed my design as a result of this, and decided to modify and cover the existing stylus body with non metallic materials. In this case, I used a strip of leather from an old wallet interior applied with a strong cyanoacrylate adhesive, and behind that, permanent black ink from an overhead projection marker to mask the original color of the light gray body. I was able to get away with a gilding process at the tip using 24 carat gold leaf probably because its such a thin metal. The important thing is that it works! The assembly required precise cutting of the stylus body, leather, and brass tubing, plus the manufacture of a small brass strip to cover the rocking button.

 

Finial assembly close

At the opposite end of the stylus I sacrificed the eraser functionality for a bit of decorative metallic flair. I never got used to flipping my stylus around like a pencil when I could instantly toggle the eraser by moving the function to the back toggle on the trigger. The finial at the end of the stylus is a decorative gold plated band from an old 1930’s fountain pen and a finial from a Schatz German table clock. Those parts were merged together with a few threaded brass parts I had laying around (not sure where they came from) and some foil tape typically used for masking photo slides. The foil tape was used to help non-threaded parts like the pen ring fit snugly over the other brass parts. This one detail makes the design LOOK Victorian.

Stay tuned for Part 2 of this post, where I will discuss the process I went through in finding and assembling recycled parts for the tablet’s body.

Upcycling An Antique Mirror Into a Steampunk iPad Frame

Upcycling An Antique Mirror Into a Steampunk iPad Frame

Steampunk iPad Conversion:

Steampunk iPad picture fame

Steampunk iPad picture fame

To build this steampunk iPad frame I found an old brass mirror in an antique store and took the frame along with my iPad to a framing shop. I had the framer custom cut beveled mattes to frame the iPad and used those precise matte measurements to build a foam core backing for the iPad to sit in. The mirror frame backing included threaded screw inserts for holding the original mirror in place so I used these inserts to secure a custom-built brass band and quick release for the iPad. I cut rounded bevels into the front of the matte for the button and camera and treated all bevels with gold paint to accent the edges and match them with the brass frame. The backing was also cut to accept the charging cord. Click here, or on the image to see a close up of the frame and iPad.

The original function of the antique mirror is also preserved in the front camera feature on the iPad; However, it is much more practical to use it for hands-free Skype or Facetime chat with a friend. To be honest, it was the mirror that inspired this project, and not the iPad. If it had been the other way around I probably would have been searching much longer for the perfect mirror/picture frame.