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.


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.


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.


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 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 are easy to lose. 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.

I worked first on the stylus (unmodified original shown on the right) 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 rear of the stylus.

Most airbrushes use a rocking lever assembly, which is why I chose to mount a trigger assembly from an old Passche airbrush on top of the original lever. See my Custom AB post for comparison with the image above. This actually works better for me because the trigger puts my finger in a relaxed position above the stylus on a single pivoting button instead of an elongated fulcrum/button I have to drag my finger across to toggle internal buttons at both its opposite ends.

It turns out that any type of metal covering the front of the stylus interferes with signal reception, so I covered the front of the stylus body with a strip of leather from an old wallet interior. Behind that I used permanent black ink to mask the original color of the light gray plastic. I was able to use a gilding process at the tip using 24 carat gold leaf without any signal compromise. The assembly required precise cutting of the stylus body, leather, and brass tubing, plus the manufacture of a brass strip to cover the rocking button.

At the opposite end of the stylus I sacrificed eraser functionality for a bit of decorative metallic flair. The decoration at the end of the stylus is a gold plated band from a 1930’s fountain pen and a finial from a Schatz German table clock. The parts were merged together with threaded brass parts and some foil tape 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 wooden, brass, and glass parts for the tablet’s body and drawing surface.



How to Produce Invisible Digital Watermarking in Photoshop Without a Plug-in

How to Produce Invisible Digital Watermarking in Photoshop Without a Plug-in

Where is the watermark?

Digital watermarking is often seen as a light but visible mark within an image, and can include a logo or URL to show copyright ownership. It is there for everyone to see (and remove). Invisible watermarks take this concept a step further and make the watermark less obvious and harder to remove. Digimarc is an invisible watermarking filter for Photoshop and is automatically included as a default. It is supported by a third party, Digimarc, and requires a subscription to take full advantage of it’s features. Its purpose is to embed an invisible watermark into an image to protect against copyright infringement and track the use of the image on the web. Digimarc works on two fronts. It embeds an invisible (strong) watermark into an image by encoding information (Author name and creation date) into a noise tolerant image’s least significant bits. That information is also stored in a database and can be cross-referenced against other copies of the same image all over the web. If an unauthorized use is discovered, the original author can prove who they are beyond any reasonable doubt and call out the infringing party.

I had a problem with copyright infringement of my own and thought Digimarc might be a perfect solution, but discovered that Digimarc’s service would not access the virtual world server where my texture images were stored. This roadblock inspired me to come up with my own type of invisible watermark using Photoshop to regain control over both the stored data, storage method, and file format. It is also important to note that the Digimarc filter can still be used to embed a second watermark into the same image if needed for distribution on the web.

Here are the steps I use for invisible digital watermarking in Photoshop:

  1. Give the original image a New Channel for encoding information. This converts it to a carrier file.
  2. Generate a second black and white image of the same dimensions and place multiple copies of a QR code in it. This is the information file which can carry contact information, a URL, or any message.
  3. Run a Gaussian Blur on the QR code to soften the edges so it will blend well with the carrier file image. Test this with a code scanner, then Copy and Paste it into the New Channel in the carrier file.
  4. Select part of the carrier image using the newly created Alpha Channel, Copy, then Paste it as a New Layer. This produces a second layer with only the coded portion of the image. It should be completely invisible at this point.
  5. To embed the code as imperceptibly as possible, run a Hue Saturation adjustment (altering the image hue by no more than five steps) and add 3% noise into the image with a noise filter. More alterations can be added if needed, but the general idea is to cover the coded layer with noise that uniformly alters the pixels slightly through all colors and shades.
  6. If the effect is too harsh the Opacity of the layer can be reduced to make the effects more subtle.
  7. Copy Merged, Paste the coded image into a New File, Flatten it and Save it to any popular file format (JPEG, PNG, Targa)
  8. Calculate the Difference between the original master file and the encoded file, Copy Merged, Paste into a New Layer. Run an Equalize adjustment on that layer to reveal the code again.
  9. To make the code readable under higher compressions, copy and compress the master file, then repeat steps 7-8.

This steganographic method may not be as sophisticated as Digimarc’s, but works for my application needs and gives a stealthy tracking mechanism for policing my work on a virtual world server hosting lossless JPEG 2000 file formats. It also survives moderate resizing, cropping, and compression. Best of all, it can be done entirely within Photoshop’s tool set without need of a third party add-on or a subscription.


Cat Image


Coded Cat Image

QR code Image

Raw extracted QR code

Enhanced QR code

Extracted and enhanced QR code (scans well) Receives an Upgrade Receives an Upgrade

The old has a new face on the web. The URL is the same, but new content is better integrated with the major social tools we all use, as evidenced by this post (published @ and distributed to various social platforms through WordPress). This upgrade will allow Rossman Art to easily reach out to and build upon an existing audience without the added burden of maintaining and propagating  isolated content. Credit for the back-end development goes to Elegant Themes for their Divi theme using the WordPress content management system. The major portion of the site still remains a portfolio showcase, but new sections have been added for a Blog and custom curated Newsletter (through I visit this newsletter daily to keep up on the latest trends in science, technology, and art. The site is open to subscribers, so anyone can can join to receive updates whenever new content is posted. Those interested in contributing content can contact Rossman Art and ask to have their subscriber status upgraded to Contributor, or Author.

I hope everyone enjoys the new and responsive look of the site!


Jeff Rossman

Customized Paasche AB Turbo

Customized Paasche AB Turbo

An Overview of the Customized Parts on My Paasche AB:

This is an old how-to I resurrected from two previous generations of It’s been informative to people in the past, and also explains a bit how I use this device.

PeelerPatNo-256852-Pg1For those unfamiliar with turbine driven airbrushes, it all started over a century ago in 1879 with an invention by Abner Peeler called the Paint Distributor. This was a system that delivered paint into an airstream on the end of a reciprocating needle. Others developed Peeler’s original design into the lighter and smaller instrument seen here. Thanks to Jens Paasche, the modern AB made its debut in 1904, and little has changed with the version still produced today. Most airbrush designs opt for a simple linear mixing of paint and air, but a modern AB remains true to the original design of Peeler’s, and has few rivals when it comes to finely controlled paint dispersal. This is a testament to the genius of the AB’s design.


Costomized Turbo_top_In_Hand


A normal AB has better control over paint flow than most other airbrushes, so why mess with it?*

The AB’s only flaw is its temperamental behavior due to the complexity of its moving parts. This is the reason I chose to modify my own AB. The three main controls , trigger, speed regulator, and stipple adjuster all need regular fine tuning to maintain top performance. Simply put, I wanted finer tuning and better performance, and was going to do whatever it took to get it. I started by making small changes to some of these control variables to fit the AB to my illustrative technique. The first thing that I changed was the long red stock AB handle. I replaced it with a much shorter rubber insert (an eye dropper bulb) seen at #4. Holding the AB this way felt more natural to me. Other modifications followed. Hopefully this tacit knowledge will inspire other AB users with a wish to tinker.


Customization Overview*

Here is a general overview of the five areas of my AB that I have customized for comfort and better performance . (1) A Sharpened needle tip to take advantage of the trigger’s precision control. (2) A Low profile grease cup screw (not shown) for comfort. (3) Custom blast jet to narrow the air blast for better performance with a sharper needle. (4) Shortened handle for comfort and easier handling. (5) Dual trigger assemblies: The short one, shown here for comparison. The longer one allows for finer needle control.


The Trigger Assembly*

I use this extended trigger assembly for better control when moving the needle in front of the blast jet. With a longer lever the thumb/finger must travel a greater distance to move the needle. This simple change is a borrowed trigger assembly from another Paasche V airbrush. It is very easy to switch between this and the original short trigger by tightening each assembly by hand. This allows for easy loosening and doesn’t strip the delicate brass threads. I rarely use the short trigger any more, so this one stays put.


Needle & Customized Blast Jet*

The combination of a smaller blast hole and sharpened needle is key to my AB’s performance enhancement. These two changes alone will significantly enhance a factory model AB. They are examples of what I term “the Maker mindset” – a DIY way of using existing tools to make better tools. My custom blast jet produces a stream of air about half the diameter of the factory supplied blast jet. I made it from a .125″ solid brass rod using a jewelers motor, sharpening stone, and micro drill bits. A tighter spray diameter coupled with a sharper needle produces a very thin line. The airbrush needle needs perfect alignment with the front of the blast hole for this to work. Also, I run the air pressure slightly higher than the recommended 25-35 PSI, but no more than 50 PSI to compensate for the narrower blast.



Front view of the customized blast jet*

This angle shows the sharpened needle extended in front of the custom blast jet. There is a narrow window of tolerance where the needle performs best in front of the blast jet. This is all fine tuned by adjusting the needle bend & sharpness, needle bearing, and angle of the paint cup. As long as there is little impact to the airbrush or damage to the needle or walking arm, these adjustments only need setting once until the needle needs replacement.


Sharpening a needle*

The taper on an original needle lengthens by sharpening its tip. This allows for greater control of the spray diameter over a greater distance of needle travel. This graphic shows the difference in a hairline spray diameter between a standard needle and a sharpened one. The red arrows indicate the area of increased performance. The dotted black arrows indicate the effective spray area along the needle. I use a sharpening stone with a jewelers motor to sharpen my needles. However, 1500-2000 grit sand paper also works well. I use this kind of sand paper often to polish and remove dried paint from my needles. This sharpening technique is also documented in “The Complete Manual of Airbrushing” by Peter Owen & Jane Rollason (now out of print, but available through Amazon). I highly recommend getting it if you own an AB.




Document icon*DO NOT modify your Paasche AB airbrush as described above if you don’t have experience maintaining it! Always consult the official AB instruction manual and parts list before attempting any adjustment or alteration to your AB!