HMV Model 328A

Working on the Cabinet

Mounting the Subwoofer

The cabinet has two wooden bars across the speaker opening.  The cone surround of the subwoofer I want to use protrudes beyond the front of the speaker, meaning it would have to be rear-mounted.  Allowing for the thickness of the baffle, rear panel and clearance for the breather hole on the back of the speaker, this massive speaker simply wouldn't fit inside the box!

The only option was to mount the speaker on the back of the rear panel, which is laser cut from 25mm MDF, facing backwards.

Speaker Baffle
Speaker Baffle, 25mm thick.  The sides of the cabinet are only 12mm, but the unsupported surface area is relatively small, so the enclosure should be solid.

Front Panel Design

I decided to replace the original front baffle and grille cloth with a thick clear acrylic panel, so you can see inside.  The speaker is a car subwoofer, designed to look good from the rear.  The Front Panel is actually made up from three layers, totalling 21mm thick.  These panels are also screwed to the ornamental wooden bars running across the front of the opening to help keep the assembly solid.

In line with my design goals, I wanted this thing to look cool and lighting was always a key consideration for this project.  The cabinet design lends itself to concealed lighting effects.

The front 3mm layer is laser-etched on the back with the HMV logo and is edge-lit by a set of red, green and blue (RGB) LEDS mounted on a circuit board.  The HMV Logo Board slides into slots in two wooden blocks inside the cabinet to allow for alignment.  The edges of this layer are covered with reflective foil which helps light dispersement within the layer.

HMV Logo
HMV Logo

The second 3mm layer is laser-etched with four symbols lit by the Standby, Power, Message and HDD LEDs which shine down from above.  These LEDS are much less powerful since two of them are driven directly by the motherboard electronics.  They are carefully lined up to shine directly on these symbols.  The edges of this layer are covered with black tape to eliminate any other light source and reduce internal reflections.

Computer Indicators
Standby, Power, Message and HDD indicators

The third layer is 15mm thick, to give strength and rigidity to the front panel.


When first designing these I didn't know about laser-etching and was planning to get these panels engraved.  Engraving machines behave like a plotter.  They require a vector drawing and cannot work with bitmap images.

Producing these images was a nightmare!  First I had to find bitmap images.  They had to be simplified into black and white line drawings in PhotoShop.  In the case of the His Master's Voice painting, this required manually tracing over the image on a new layer.  I then exported these as JPG files.  These were put into CorelTRACE to produce a vector drawing in DXF format.  Initially, my ancient CAD program (would you believe AutoSketch for DOS!) had trouble importing these files and I had to go back to PhotoShop to simplify them even further, then repeat the whole process.  Even then, some of them were beyond my CAD program and I ended up with an incomplete image.  The next problem was that CorelTRACE produced polyline drawings, unsuitable for engraving machines.  So, you guessed it, I had to manually recreate the drawings yet again on a new layer in my CAD program, using lines, circles and curves!  CAD programs are not really meant for artistic drawing and this process took forever.

Speaker Enclosure Top

The speaker enclosure area needs to be sealed.  This is not as easy as it sounds because the top of the original speaker baffle sticks up past the bottom of the Main Chassis, making sealing the top extremely difficult.  The new clear acrylic Front Panels which will go in place of the original baffle will have to be fitted first, then the top Brace Panel fitted and sealed around it.  And the whole thing is going to have to be removeable, so I can remove the acrylic panels while the cabinet is being refurbished.

Because the Front Panel is now clear, the top 20mm of the opening needs to be blacked out to prevent the Brace Panel from being exposed, since it is below the top of the front opening.  A special laser-cut 2mm black acrylic Spacer Panel was designed to fit behind the Front Panels.  Because this black panel is so far back and the internals of the enclosure will be painted black, it will hardly be noticable.

The original baffle was recessed and the Brace Panel which forms the top of the speaker enclosure area has to fit tightly around the Front Panel, the Spacer panel and the existing internal woodwork.  This is laser-cut from 16mm MDF.

Brace Panel

Cleats attached to the side of the cabinet strengthen the structure and the original chassis supports are bolted to the top of the Brace Panel.

Brace Panel top view
Top view of Brace Panel fitted around the Front Panel, Spacer Panel and original internal cabinet cleats.


After months of producing drawings, the moment of truth has arrived!  Theoretically, I email them off to a supplier and get the completed items delivered in a few days.  If I have made a mistake I'm screwed...

Time passes...

My worst fears are realised when I receive the items and to my horror discover that despite all my hard work and double-checking measurements with printouts of my drawings, I've somehow managed to screw up the three front panels which all came from the one master drawing!  Naturally, these were the most expensive and critical part of the exercise - a problem with one of the other items would have been no big deal.  I'll leave it to your imagination to guess the exact number of expletives that were issued!

Fortunately, I found a way around the problem.  Now that I have finally worked out all the details and made all the fiddly bits, it's time to strip everything out of the cabinet to work on it...

Preparing the Cabinet

Cleats were fitted to the cabinet to support the Speaker Baffle, the speaker enclosure top Brace Panel, the Power Amplifier and some rear cover panels.

To allow clearance for the Computer Power Supply and The Dog Box, part of one of the cleats was attached to the Brace Panel.  (Yes, space is that tight!)  Another cleat secures the rear edge of the Brace Panel to the original cabinet horizontal bar.

I removed a plywood panel which was attached to the bottom of the chassis support bars to cover the bottom of the chassis.  Instead, the Brace Panel will be screwed directly to the chassis supports.

I also removed a bar running across the bottom of the speaker enclosure at the back and fitted this across the middle of the bottom of the cabinet.  An additional piece of plywood covers the gaps between the slats and gives enormous strength to the base.

Apart from the cabinet side panels, the chassis supports are the only things connecting the rear bar to the front of the cabinet and these were loose.  I temporarilly removed the chassis supports.

Cleats fitted to Brace Panel
Cleats fitted to the Brace Panel (bottom view)
Re-enforcing cabinet base
Re-enforcing the cabinet base
Cleats fitted to cabinet
Cabinet stripped with cleats fitted

Bare cabinet rear view
Bare cabinet front view
Final inspection...
Speaker Baffle rebate
Speaker Baffle rebate

The new Speaker Baffle is 25mm thick, but the horizontal bar is only 23mm from the rear of the cabinet.  A 2mm rebate was cut into the top 50mm of the Speaker Baffle to account for this difference.

Before reinstalling the chassis support bars, the Brace Panel and Speaker Baffle were bolted in place to securely position the horizontal bar.  Part of this process was to drill pilot holes for the screws to secure these panels.

After installing the chassis support bars, I poured polyurathane wood glue into the joints to permanantly secure the horizontal bar.  Whilst at it, I poured glue into every orifice inside the cabinet I could find to generally strengthen the joints.

Finally, the entire inside of the cabinet was painted matt black.

Tapping drill holes for front panel
One of the scariest jobs was tapping the pilot holes for the Front Panel Assembly!  Here, the front layer is being used as a template.  The wooden bars and top holes were critical, with very little timber to screw into.
Re-installing the Chassis Supports
Re-installing the original chassis supports

Painting the inside black
Painting the inside black
Paint, glue and elbow grease


Well, that's about all I can think of to do for the cabinet preparation.  Now the cabinet is out of here to get polished.

In the meantime, a bit of work on the cabinet sub-assemblies.
Edu Valk
Meet Edu Valk - master craftsman, otherwise known as Dr. Goodvibe.  Edu has kindly offered his professional services to restore the cabinet.
Polishing the cabinet
The old flakey shellac has been stripped, the highlights repainted and the polishing begins.  Note the colours in the timbers.
Completed Baffle Assembly
It's hard to say whether this is the speaker mounted on the baffle or the baffle mounted on the speaker!  And there's that cat again!
Completed Brace Assembly
Completed Brace Assembly.  The sensor for the TV remote control is cable-tied to a bracket made from a black coathanger and will sit just behind the transparent front panel.

It's back!  And what an amazing job!  It looks awesome!

Now, a final touch-up with the black paint and I will finally be able to put this thing together...
Cabinet finished (bottom view)
Cabinet finished (side view)
The cabinet - finished and ready to go!

Final Assembly

Original 1941 Switch Bezel
Original 1941 Switch Bezel.
Bezel installed in cabinet
1.  The bezel simply pushes snuggly into a 16mm diameter hole.  This actuates a modern momentary switch mounted inside which is the ON-OFF switch.
RGB LED Shield
4.  The RGB LED bodies are wrapped in reflective self-adhesive aluminium foil, to disperse stray light from the sides.  The foil must be kept away from the LED leads!  An overlapping layer of black tape seals off stray light coming from the back of the LEDs.
Cable Duct
2.  Cable duct to get internal cables from one side of the cabinet past the chassis to the other side.
Cabinet Wiring Harness
3.  Cabinet Wiring Harness with fittings attached such as power switch and LED sockets.
Front Panel Layer 1
5.  Front Panel Layer 1 with reflective self-adhesive aluminium foil around the edges to disperse light within the layer.  The break in the foil allows the RGB LEDs to light this layer.
Front Panel Layer 2
6.  Front Panel Layer 2 with black tape around the edges to minimise interference between the icons and keep out external light.  The break in the tape allows the computer and Standby LEDs to light the icons on this layer.
Standby LED
7.  The Standby LED needs to be positioned vertically to target Layer 2, as well as horizontally to illuminate the Standby icon.
8.  Right: Front Panel Layer 3 (15mm thick).  On top of this goes the black Spacer Panel (with the backing still attached in this photo) to mask off the top of the front panel.  The whole thing is then screwed down.
Layers Assembled
9.  Right: A layer of black tape is applied to the edge of Layer 3 to keep out external light.  Also shown here is an additional layer of black tape in the computer icon area between Layers 1 and 2 to stop the reflective tape on Layer 1 interfering with the computer indicators.
Keyboard Sensor
10.  The keyboard sensor is siliconed to the bottom of the speaker enclosure area so that its status indicators (Caps Lock, Num Lock and Function Lock) can be seen.  All cabling in and out of the speaker enclosure area must be in place before the Brace Panel is installed.
Layer edges
Brace Panel installed
11.  The Brace Panel is now tightly fitted around the front panel.  Right: Brace Panel viewed from speaker enclosure area.
Brace Panel installed
Blu-ray/DVD drive
12.  The Blu-ray/DVD drive slides in from the front.  Behind the clear front panel you can see the black spacer panel and the bottom of the Brace Panel.
Blu-ray/DVD drive mounting bracket
13.  Blu-ray/DVD drive mounting bracket.  14.  SATA lead.
Blu-ray/DVD drive ground wire
15.  Blu-ray/DVD drive Ground wire.
The Dog Box
16A.  Mounting The Dog Box.
16B.  Fit lid assembly.
Power Supplies
17A.  Computer Power Supply front mounting screw.  You definitely need a magnetized screwdriver for this!
Computer Power Supply rear mounting bracket
17B.  Computer Power Supply rear mounting screw.
Relay connector
18.  Power Relay Connector (J0) to The Dog Box.
Blu-ray/DVD drive cabling
19.  The Blu-ray/DVD drive cabling is secured with the help of a cable tie and black tape to keep it in place when the Main Chassis slides around it.
Cabinet read to go
That completes the internal cabinet fittings and wiring.  It's now ready for the Main Chassis to be installed.

Main Chassis Installation

Motherboard Main Power connector
20.  The chassis is inserted half-way into the cabinet chassis guides.  With the chassis in this position, the motherboard main power connector is installed.  (I wasn't kidding when I said space was tight in this thing!)
Keyboard and TV Remote receivers
27.  Finally, connect the Keyboard and TV Remote receivers.
Right: Cabinet with Main Chassis and subwoofer installed.  The cables hanging out on the right hand side are for the Amplifier Power Supply.
Blu-ray/DVD drive SATA lead
21.  With the chassis half way out, connect the Blu-ray/DVD drive SATA lead
Cabinet Connector (J3) and Ground Terminal
24.  Connect DB25 Cabinet Connector (P3).
25.  Connect 3 ground cables to the Chassis Ground terminal.
Chassis power connectors
22.  Connect Computer Power Supply Connector (J1).
23.  Connect Audio Power Supply Connector (J2).
Motherboard 12V Power Connector
26.  And don't do what I always do when putting a computer together and forget to connect the motherbord 12V Power Connector and then wonder why the thing won't boot!.
Rear view of cabinet with Main Chassis and subwoofer installed

Adjusting the Lighting

LED circuits #6 - #9 are bounced off reflective tape on the side of the speaker enclosure area onto the rear of the speaker.  LED circuit #10 - yellow - has some extention cables fitted to move the bottom two to the middle front, aimed directly at the front of the speaker, while the top two are aimed directly at the top of the speaker.  This creates distinctly different lighting angles to the other circuits and when alternating between LED circuit #10 and any of LED circuits #6 - #9 a sense of movement can be created.

Complete system
Complete system running Winamp and the Milkdrop visualisation plugin.
Top view of cabinet
Top view of cabinet with the internal chassis lights activated.
Cabinet front view
The System in Standby mode
The System in Standby mode.
Standby Indicator
Standby Indicator
Power Indicator
Power Indicator
Message Indicator
Message Indicator
HDD Indicator
HDD Indicator