GR Research LGK 1.0 Full Range Speaker

Every now and again I take a break from building cables and amps to build a speaker. Your better half will typically notice a speaker sneaking into the house a little more reliably than an amp or cable, so be forewarned ;)

Since I don't own a table saw or have anywhere to even put one, I enjoy building speaker kits where the MDF/pine or other wood is pre-cut by CNC machine. The industry nomenclature for pre-cut wood for speakers is a "flat pack". You still get to treat the cabinet interior, fit the crossover, and glue everything together, so you don't miss out on all that fun.

The last flat pack speaker I built was the Frugel Horn from Planet 10 Hifi, which was a simple to assemble back-loaded horn which could house a Planet 10 treated driver, or a stock driver from Fostex or MarkAudio. The speaker build this post will be covering is the GR Research LGK 1.0 Full Range Speaker kit.

The LGK 1.0 uses a 3" driver made by GR Research. Yes you read that correctly... 3 INCHES! Many may think three inches is inadequate, but it's all about how you use it (a-ha). This particular LGK driver is happily seated in a very solid 8"x 4.5" x 12"cabinet that's cut by Subassemble.

LGK Flatpacks made by Subassemble

The rest of the parts for the LGK can be procured from Danny at GR Research. The kit from Danny includes a number of nice quality parts, including Sonicaps, Mills resistors, Erse Air core inductors, Electra tube connectors (which serve as the speaker connectors), No Rez, and other minutia including ports, screws, wire, solder, and heat shrink.

The first part of the process is to cut up the No Rez, which is a thick damping material specially designed for loudspeakers which adds mass and reduces resonance and internal waves. The thicker, bottom portion of the No Rez closest to the adhesive takes a little bit of elbow grease to cut with a razor blade. Remember to change out the blade before you start grumbling under your breath.

Mapping out the cuts of the No Rez

Once the cuts have been made, the CNC cut wood pieces are laid out and the No Rez applied after to ensure it won't bump into anything during final assembly.

No Rez lined up on the side panel

I added a bit of sealing caulk around the edges to prevent air from escaping anywhere but the port. The No Rez needs to be trimmed a little bit to allow clearance for the speaker, port and crossover.

Caulking the edges for a good seal

The next task was to assemble the very simple crossover, which acts as a baffle compensator to help boost the bass. The three parts are soldered in parallel. The part values are proprietary per GR Research so I can't share them unfortunately.  

Crossover parts

I cut two pieces of FRP material and mounted some turrets so the parts could be mounted cleanly, with zip ties holding down the inductor. The board is then mounted to the top wood panel with caulk.

FRB Boards fashioned for the crossover

Once everything is in its proper place and you've tested to ensure everything is working, the speaker is then sealed up with your favorite wood glue and clamped from every angle. Excess glue is removed with a damp paper towel. Don't soak it or the MDF will expand, and no one likes wet, expanded MDF.

Speaker clamped down to dry

Here's the speaker cabinets after drying, right before getting a sand with 60 grit sandpaper. A basic electric sander is pretty affordable and save a lot of effort at this step (if you don't already have one).

Unsanded Cabinets

Below is the difference between sanded and unsanded cabinets. Any gaps in the wood should be filled with wood putty, or if you are going to be painting the cabinets with Duratex, you should use drywall spackle per the directions for better adherance. For the corners, I sanded them lightly with 3-4 quick passes, some people like to round them a bit more, or route them.

Unsanded vs. sanded

The next step is to finish the cabinets. You can stain the cabinets, metal leaf them, paint them, veneer them, the sky is the limit! I chose an interesting finish (which GR Research carries) called Duratex. Duratex, which could be the name of a manufacturer in the family planning aisle, is a lot like a truck bed liner paint, it's durable and creates a very dimensional texture. This is especially great if you screwed up somewhere along the way and need to hide your mistakes or you're a sanding slacker ;) 

Duratex, check out that texture!

Duratex requires two coats, you can vary the texture with the included roller a little bit for either a smoother or rougher texture. When the solution is rolled on, it creates bubbles which pop, adding to the unique finish. 

Next the ports should be installed, there is a small ring around the cork cap which is recessed to allow you to put some caulk down to seal it in.

Sealing up the ports on the back

Now the cool little Electra Tube connectors can be soldered on. These are pretty unique connectors; they have a patent pending from what I understand. They are low mass, so they only use the amount of metal necessary, and allow the internal wire to be very close in proximity to the wire within their proprietary banana connector. The nice thing is that I've found they work with standard banana connectors as well, so they shouldn't affect your speaker resale value much if someone is married to their particular Kimber/Nordost/etc. speaker cable. One of the nicest things about these connectors is you just hammer them in with a rubber mallet. The installation couldn't be simpler. 

Electra Tube Connectors soldered in place

Soldering the driver in is a simple affair. Just two wires to worry about. Note the bottom of the driver cutout has clearance for the solder posts. 

LGK driver before installation

You may have to do a bit of Dremel sanding if the driver doesn't fit perfectly due to paint getting in the routed area. Once in place, you can drill a set of pilot holes, then screw in the four screws. All done!

So if you have three Benjamins, don't have a lot of space to spare, and are looking for a pretty resolving desktop speaker, the LGKs are a great bet. You'll note some very impressive bass response and nicely resolving treble. I have a slightly larger full range speaker with a Fostex driver and baffle compensation "crossover" and I like each of these for different reasons. The bass response and treble energy on the LGK is better, and the Fostex offers slightly better presence and midrange.

Overall a great project and a great speaker. Looking forward to see how Danny incorporates these drivers into other designs.

Need some speaker cables for your LGKs or other speakers? Contact Zynsonix Audio for some great sounding options.

The Fine Print:

The above steps detailing the building of a speaker are for entertainment purposes only, and are not intended to be used as instructions. Zynsonix Audio LLC and DIYAudioBlog do not have any affiliation with SubAssemble or GR Research. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. Please keep this in mind.

Xtension Retro Arcade Cabinet - SNK Neo Geo Edition

Given that you’re on this page, you likely spent a good portion of your childhood in the 80s and 90s. There are few things more nostalgic than a standing arcade cabinet, perhaps running a classic like Galaga, Pac Man, Street Fighter II, or something else from the canon of truly awesome arcade games. With arcades now being few and far between, you may be reminiscing about “the good old days”. Now you could plan out your own cabinet, however not all of us have the time or the tools necessary to create the panels to assemble an arcade cabinet. Fortunately, there are few companies out there that will help give you a relatively authentic arcade experience back without breaking the bank.

The company that I’d like to single out is RecRoom Masters. This is a small, bustling company that is constantly bringing new products to the market. There is a large range of pricing and cabinet sizes so you can purchase based on your budget and the amount of space you have available. Wayne Scheiner at RecRoom Masters and I exchanged numerous emails so I could get a good feel for the decisions I needed to make so that the product came out the way I wanted. Even though I already settled on the larger Xtension Arcade with the 27” screen, I had to decide if I wanted to light the top, if I wanted a coin door or a cabinet drawer, if I wanted graphics on the sides and over the stick, and if those graphics would be vinyl or a more permanent adhesive.

When I was younger, one of the most exciting cabinets to find at an arcade, bowling alley, or restaurant was an SNK Neo Geo Multicade MVS System. The Multicade would usually be stocked with 2-4 different games like Samurai Shodown, Sengoku or King of Fighters. The Neo Geo home system, which was famously expensive when released ($650 for the system and $200+ for each game), was out of the price range of anyone I knew, so the only opportunity to play many of these classic releases was on an MVS System. Now that a couple of decades have passed, the only time I see an MVS is occasionally at a convention.

A few iterations of the MVS Multicade Cabinets

For the sake of nostalgia, I decided that I wanted my Xtension arcade cabinet to have the same look and feel as an SNK MVS, in all its red and white glory. I opted to have RecRoom Masters apply the permanent stickers on the side panels, and prepare me some stickers and vinyl for the front of the cabinet and the Tankstick, which is X-Arcade’s larger joystick with the trackball in the center for playing bowling, golf and marble games. (As an aside, X-Arcade and RecRoom masters are two different companies, RecRoom Masters fashions their cabinets so the X-Arcade sticks can be dropped in quickly and easily.)

The X-Arcade Tankstick

The X-Arcade Tankstick is built like a … well you know. It has a nice heft to it, the finish feels durable, and accessing the interior doesn’t require much effort. Spending some time reading the reviews online, most people like X-Arcade offerings, but don’t care as much for the included joysticks, which are actual X-Arcade branded units. Many suggested switching over to Happ branded units as they tended to be more responsive. Since purchasing a pair of these would only run about $20, I decided to take the plunge. The HAPP units feature Cherry switches, and are actually easier to install and uninstall because of their smaller girth around the bottom.

The Happ versus the XArcade Joystick

Switching out the joysticks in the Tankstick requires you to pull the little rubber nubs out from the center of each rubber foot, then unscrew the screw under each one.

You can then access the interior, which may look like a rat’s nest of wires to the uninitiated, but it isn’t too hard to visually follow each wire. I took a photo of the interior for a reference of the color coding, then unclipped the leads, unscrewed the bolts, removed the spring clip at the base of the x-arcade joysticks, and removed them from the unit.

Stock X-Arcade Stick

Removal of the existing joystick

The Happ sticks have the same hole pattern and are easy to drop into place. 

Installation of the Happ Joystick (note I like zip ties!)



Another consideration while the joystick was open was wiring up the coin door on the unit so dropping a quarter in would actually register in-game. The Happ coin door from X-Arcade has a pair of leads that you wire up to one of the buttons within the joystick for that purpose. I decided I would be fancy and sleeve this lead with Techflex sleeving rather than leaving the white and green wire exposed. Now that the joystick was all set, I could concentrate on the Xtension cabinet.

Coin door leads needed a good Techflexing

Tankstick Interior

The Xtension cabinet comes in three relatively large boxes that have a good heft to them. If you’ve ever purchased set of shelves to assemble from a department store, that would give you a good idea of what to expect. Upon opening the boxes, everything was well packed with lots of foam and bubble wrap. Putting together the unit is largely like putting together furniture from Ikea, just follow the diagrams and put in the bolts, pegs, etc. While the directions could have been slightly more explicit in a couple of places, I’d give them a solid rating.

Below are some photos of the base of the cabinet being assembled:

Base with coin drawer opening facing front

Interior support for X-Arcade Stick

This little board helps keep the joystick in place during play

The left side being fitted in place

Adding the bolts before standing up

And finally standing up

Dropping in the Happ coin door didn't require much effort. Six metal pieces are screwed in place and that's all she wrote. The unit has an LED that lights up, this needs to be plugged into an electrical socket.

Back of the coin door

Open the coin door for access to the interior cabinet

Joystick Sitting on Base

One of the trickier parts of the build was getting everything situated in the small marquee area. I mounted a GE metal body light that was a bit less deep than the GE light that comes with the unit so I could allow room for a pair of speakers.

GE Metal Body 24" Under Counter Light

Mounted to backboard

The speakers are a pair of MarkAudio full range CHR-70 4” drivers, full range meaning that they’ll reproduce the whole frequency of sound. These are popular units in the DIY world, you’ll see them being used by Planet10 hifi and other full range enthusiasts. If you like the Fostex sound you’ll probably like these.

MarkAudio CHR-70 4" full range drivers

Adding Dynamat damping around drivers

Wiring up the Kimber TCSS to the speakers and 4 pin XLR

I mounted the MarkAudios behind the routed holes in the board behind the marquee, dampened the board with Dynamat Xtreme, and then mounted a 4 pin XLR above the light and ran Kimber TCSS wiring from the speakers to it, that way it’s one quick, easy locking connection to attach a 4 pole speaker cable to the back rather than four binding posts... it's just a cleaner look with less fuss. Below is the rear of the marquis area with the four pin XLR connector and a handsome litz braid of Kimber TCSS wire. The wire is 19 gauge thick, which is is ample for the application.

Custom 4 pole speaker cable connected via XLR

Once all these items were secured in place, getting the plexi and graphic to stay put as I closed the unit was a doozy. I ended up putting very small pieces of electrical tape on the top and bottom of the plexi glass to hold the pieces sandwiched together, then slowly slipped them into place. The tape is hidden by the routed wood area, so no worries there.

Testing the backlight on the marquis

The monitor was the last think I needed to situate before pulling everything together. RecRoom Masters recommends a 27” monitor that has screw holes facing the back and connectors that face downward for the sake of clearance. You could obviously use something else if you wanted, but you’d have to modify the board that it mounts to. I chose a Viewsonic VA2703 monitor, it was the only one I could find that fit all the criteria. You can find these going for as low as $180 refurbished to $230 new, so not a tough investment.

Once the top part of the cabinet has all the goodies in place, it can be a bit heavy. I’d recommend a second hand to help pick it up and put it in place, then do some final tightening of the bolts (but not too tight, they can cause the graphics to buckle).

One everything is put together, you have ample cabinet space in the back to put a PC and whatever else you need. I added a little wifi antenna unit and my purpose-built Gainclone amplifier and USB DAC, who’s switches are easily accessible from the front of the unit when opening the coin door.

Below is my hand-built Gainclone amplifier from ChipAmp based on the LM3886. I built this nice and small specifically to go into the arcade cabinet. It puts out 68 watts which is more than ample for the 4" Mark Audio drivers. Within it is a USB DAC (the GrubDAC) which converts a USB digital signal to analog before the amplification stage. I installed a little switch and pair of RCAs so analog inputs could be used as well. To see more about this build, go here.

Hand-made Gainclone / Chipamp 68 watt amplifier

The PC inside uses a small form factor case by Rosewell - The Legacy U3-B, with a low power Intel i3 so it doesn't generate too much heat. You can see more details on the case and PC here.

Rosewill Legacy U3-B

Below are photos of the completed cabinet in all its glory:

Keyboard drawer open

Below is the slide-out keyboard tray that holds a full-size keyboard and mouse. I chose a Corsair Raptor K30 which has the nice light-up red keys, and the mouse is a laptop wireless unit from Microsoft. You can actually control the cursor using the track-ball, but it's a little slow. 

Close-up of the keyboard tray

With keyboard tray closed

Opportunities for tweaks

For the cost, the Xtension is amazing. You’re not going to find a better product out there for the price. That being said, there are a couple of areas that you could make some tweaks or mild improvements if you wanted to put a little more money into the project. I picked up a longer 24” light for behind the marquee that was less deep to give more room for the speakers.  I also mounted a small black kitchen knob on the keyboard area, as it can be a little stubborn to open without one. Another thought is that you could mount a higher end drawer slide that extends a bit further for better access to the keyboard.

Hope you enjoyed the post. As always, if you are in need of some custom audio cabling to take your rig to the next level, contact Zynsonix Audio. Custom work is a Zynsonix specialty, even if you need a 4 pin XLR speaker cable for the back of an arcade cabinet ;) 

The Fine Print: The above steps detailing the building of an arcade cabinet are for entertainment purposes only, and should not be used as directions / instructions. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. Zynsonix Audio does not have any affiliation with X-Arcade, Recroom Masters, or any of the other companies mentioned above.