Overnight Sensation DIY Speaker Kit Assembly Step by Step

In this post I’ll be building Paul Carmody’s Overnight Sensation DIY speakers from a kit. The Overnight Sensations are an extremely popular DIY bookshelf speaker for a few different reasons. One, cost; they are a mere $120-140 a pair at the time of this writing. Two, they sound great. It’s hard for me to recall hearing such dynamic sound from a diminutively sized form factor. Three, the build is super easy. If you have some basic tools and know how to solder, you’re all set. This post is going to be written for a beginner in mind, so if you are already experienced feel free to skip along.

There are three places I know of to get a kit. Partsexpress which includes the full kit with wood panel flatpack and accessories, MeniscusAudio which does not include the flatpack but comes with tweeters with screw-in frames, which I feel is preferable should one need to replace them down the line, and DIY Sound Group, which appears to have a similar kit to Partsexpress.

A typical Overnight Sensation kit

What will you need besides the kits? Each one is a little different, so pay attention to the parts list, but you will likely also need a set of binding posts, 5/8” black wood screws, sandpaper, wood glue, wood filler, and solder. Optionally, you will also want sealing caulk, polyfill or similar solution, and either paint or staining supplies depending on how you’d like to finish the speaker. Tools you will need include bar clamps (or trigger clamps), soldering iron, electric sander, and a power drill.

If you don’t already own clamps, they are going to be a bit of an investment. You ideally need 6 or so and they run about $15 each, so potentially check with a friend to borrow a set if that’s a problem. If you decide to buy a set, get a couple that are longer than you need as well so they’ll be around when you go to make a bigger speaker later 😉   

If you purchase a unit with a flat pack, the wood will be trimmed for easy assembly. You will simply add wood glue between the joints, clamp the enclosure together, and wipe away any excess wood glue with a wet paper towel. Ideally you will leave one side open so you can finalize the internals before sealing it up. Some people also prefer to only screw-in the rear panel with a few modifications, that way you can get in there later if need be. If you follow this route, be sure to find a good solution to seal the edges so only the port is allowing air out of the chamber. Some people also like to mount the crossovers outside so they can modify them later. If that floats your boat, the world is your oyster.

For my assembly, I found a set of crossover PCBs on eBay which I believe are made by DIYSoundGroup. They are very reasonable, and I highly recommend them as they make things so much faster and easier than drawing out the arrangement from the schematic, figuring out a good layout, gluing the parts in place and then wiring everything point to point. 

PCB Crossover for Overnight Sensations

Populated Crossover

That being said, there is absolutely nothing wrong with going that way, and you have more freedom to use larger caps if desired. Some will also say point to point sounds better than going through PCB traces, but that subject is better left for squabbling on audio forums somewhere.   

For my build I chose to assemble the crossover first and mount the PCB on the bottom panel. The Dayton caps are solid and work perfectly well here. I prefer Mills wirewound over sandcast resistors, they're worth the extra if you can swing it, and I had a pair of surplus Mundorf capacitors for the 0.22uF position, but sticking with all Dayton caps is fine too. This is a budget build so you won't get too much yield from bumping up the parts quality. The interior of the other panels is adorned with Dynamat-like sheets for internal damping. There are plenty of brands out there at different price points, but try to get thicker ones for the purpose of adding mass. I personally like to use a staple gun to really keep the sheets on there. Not necessary, but low cost insurance they won't move. It’s important to not completely cover the panels as wood glue, then later caulk will be used to ensure all the corners of the cabinets are sealed. 

Once the panels are all prepped, then they can be glued and clamped. The low-cost Titebond wood glue in the red and clear bottle works well and is inexpensive. For clamps, generally I like to leave them on overnight while the wood glue completely dries, however with most brands you can disassemble after about a half hour or so, so long as you aren’t putting any pressure on the panels.

The more clamps the better!

I left off the front baffle so I could get my hands in for the removal of excess glue and caulking of the corners. The binding posts I’m using are Partsexpress’ gold heavy duty ones along with the nice-looking mounting plates. Normally I use Cardas copper billet posts however this is a more affordable build, so I wanted to keep it that way. Most binding posts are gold plated brass so will sound pretty similar; however, you don’t want anything flimsy that will fail overtime or loosen up inside as once the speaker is sealed. Once it is, you’ll have trouble getting back in there to fix anything.

Partsexpress Heavy Posts

Measure before drilling as the plate takes up some real-estate.

Also, while the speaker is still open, I ran wiring from the PCB to the areas where the drivers and binding posts will be. Again, it’s important to get the lengths and connections right as it will be difficult to access later. You don’t need thick wire as the lengths are going to be short so the resistance is minimal. I used 19 gauge for the tweeter and 16 gauge for the woofer and binding posts.

Wires running from the PCB

Note placement of damping sheets

When everything is ready inside, the front baffle can be glued and clamped in place. 

Once dry, now is a good time to sand where the panels meet to ensure the transitions are smooth. Start with rougher grade sandpaper (60-80 grit) and working your way up. Using finer than 100 grit can sometimes cause issues with this type of wood taking stain, so consult the kit manufacturer if you are staining the wood. There will be small gaps in some cases where the wood touches. This is fine and can be fixed by using wood filler. There are plenty of varieties out there like Elmer’s, Minwax, DAP, etc. and all work well, but if you are staining, you will want a stainable filler.

Sanded down after filler has been added to gaps

Given I hardly have time for personal projects these days, getting the finish done quickly is a major boon. I like to use a product called Duratex from Acry-tech. This is a paint that’s similar to truck bed liner and covers up any surface imperfections with a texture. It dries quickly (about 3 hours) and provides a durable finish. Two to three coats are all that is needed and there is no sanding required between coats. Because these speakers will be in my workroom, there isn’t much point in giving the speakers a museum grade finish, but the Duratex looks nice and is very serviceable. You can either buy Duratex from Partsexpress or directly. Custom colors are available direct, like this nice bright orange.     

Speakers with a few layers of orange Duratex coating

If you’d like to add internal fill, now is the time to do it. I used two handfuls of fluffed Acoustastuf per speaker. The drivers can now be soldered in and placed. The HiVi mid-drivers come with foam surrounds that stick in place, be sure to use these for a good seal. The tweeters will require a little bit of effort to do right and should be handled carefully. First, if any paint or stain ended up in the cavity for the tweeter, you may need to lightly sand to ensure clearance as the fit is very tight. The tweeters do not include a foam surround so a very thin layer of caulk should be placed between them and the wood cabinet to create a seal. On the back the binding posts can be soldered and the plate can be drilled in place.

Drivers soldered in place

Finally, we can plug them in and have a listen. Most speakers have a little bit of burn-in time where the drivers settle in. This is highly dependent on the driver. I found the Overnight Sensations didn’t need much time at all to sound great. The sound is fun and large, full, and on the warm side, but there is a good amount of detail. Given the cost, these are insanely good. Despite a sensitivity rating of 83/dB, they are sensitive enough to get quite loud with my Dynaco ST-35 running in either 17.5 watts per channel push-pull or ~9 watts triode mode in a smallish room.

At the end of the day, there are plenty of great sounding speaker kits out there, and many will sound better than the Overnight Sensations, however I think the price-to-performance ratio and ease of the build makes them a tremendous introduction to first time speaker builders who are looking to get their feet wet in the space. If you’re looking to add some handmade speaker cables, try out some silver-plated PTFE surplus wire, it’s a nice value. 

As always, thanks very much for checking out the blog. If you are looking for custom audio cables, headphone cables, and line or headphone switchers, please check out Zynsonix.com. Until next time!

The Planet10 Frugel-Horn mk3 Backloaded Horn

While high-end audio may be a niche following, there are further sub-niches for products that have a specific appeal within the marketplace. Most speakers on the market are a 2-way design, meaning they make use of both a woofer for the low-frequencies, a tweeter for the high frequencies and a passive internal crossover consisting of a network of inductors, resistors and capacitors that splits up the frequency range between the two. You may have seen 3-way speakers that add a midrange to the mix, or other more complex designs that split up the range across many drivers such as a line-array. Then we have the full-range speaker, which makes use of a single driver to reproduce as much of the audible frequency range as possible. This design does not make use of an internal crossover, leading to what listeners feel is a more natural sounding response, but often times this particular design sacrifices the highest and lowest frequency response.

There's a solution to this issue by making use of technology that stretches all the way back to the mechanical gramophone in 1857; the horn. Thanks to the advent of computers and more advanced sound modelling technology, horn development has really come a long way in recent years. For full-range drivers, the horn attaches at the rear of the driver, allowing the front of the cone to radiate the high-frequencies directly. The level of the lower frequencies are increased to the same level as midrange and treble by making use of the horn. Because bass frequencies have a long wavelength, the length of the horn needs to be fairly long  to cover the low frequencies. A completely straight horn would be obtrusively long, so they are usually folded to take up less real-estate. The Planet 10 team, which includes David, Chris and Scott, has been working on a number of back-loaded, folded horn designs, the latest iteration being the Frugel-Horn mk3, with special help from Ron Clarke who designed the signature curved mouth opening.

One of Planet10's original Frugel Horn Designs

The Frugel-Horn mk3 can house a variety of full range drivers. Candidates include the Mark Audio Alpair 7, CHP70 & EL70, CHR70, Fostex FE126e, and 126En among others. The carefully calculated design is simple but elegant. It's apparent that Planet10 was concentrating on making the design as simple to assemble as possible while still maintaining the performance aspect of the speaker. All the wood panels have been CNC fabricated, so the dimensions are much more exact than if you were cutting by hand.

I began my journey into backloaded horns by purchasing a Frugel Horn "flat-pack" from Planet10, along with a set of his matched and modified Fostex full-range drivers. A flat pack is a stack of CNC cut wood that's ready to be glued together. It's pretty much essential to have this wood pre-cut because the design would be quite difficult to fabricate by hand.

The assembly process began by checking the fitment of the wood boards and lightly sanding as necessary. Titebond wood glue was then placed in the recess and wood boards fit in place. A small spacer piece was glued and added, the boards were checked to be level and clamps were put in place.

First step assembling the Frugel Horn

Next came the placement of the front baffle.

Gluing the baffle in place

Followed by the top, which required pressure in a number of dimensions.

Fitment of the top of the speaker

And finally the bottom piece.

Gluing the bottom in place

Another perspective

Once everything had ample room to dry, I applied silicone sealant to the interior edges to prevent air from escaping. Then came the process of adding the damping to prevent reflections around the driver.

Internal damping within the Frugel Horn

I used approximately 1/5 of a pound of Acousta-Stuf from PartsExpress for each speaker to line the interior horn area. The batting had to be appropriately "teased" to fill the opening adequately.

Acousta-Stuf filling

Before the final wood panel would be glued in place, a set of holes were drilled to allow for "hurricane nuts to be inserted on the inside. These would connect to either carpet spikes or out-triggers. Wood glue was then placed generously as the excess could be wiped away with a damp towel and sanded later. All the clamps I had available were used to compress the speaker together during the initial placement. 

DAP stainable Plastic Wood was used to seal up any small gaps in the final fitment. Once the Plastic Wood has dried, it is sanded down smooth.

Once all the surfaces were sanded down smoothly with 180 and 220 grit sandpaper, the staining process could begin. I decided early-on that these would be a nice deep red finish, something hopefully similar to the sweet looking Zu "Sangria" finish. Since there aren't any off-the-shelf solutions for oil-based red stain at the local hardware store, I procured some water-based clear tint base that I would be tinting red. Bright Red Trans Tint was used for this purpose. Water-based stain has it's own set of products for pre-stain prep and finish, which you can see in the below photo.

The initial prep includes a pre-stain layer, which is followed by a light sanding. This prevents the grain for raising inopportunely during the staining process. This is followed by the wood stain. The TransTint is to be mixed at a half bottle per 32 ounces; in this case the whole bottle was used for a deeper, more saturated tone. Four coats of this stain were applied to get the wood evenly dark. Finally, three layers of water-based satin Polycrylic are brushed on to seal up the finish. It's a relatively long process going through all these coats, but if one takes their time, it's worth it in the end.

There were a few nice adornments that were planned for this speaker to give it a more professional look. I created some custom art files and had them engraved on plates for the front and back. The back plate would cover the circular hole on the back that was designated for a basic set of terminal posts and house a pair of bare copper Cardas posts. I find these to be the most attractive posts on the market, albeit a bit expensive.

Custom engraved speaker back plate

On the backside of the engraved plate is a circular piece of Dynamat Extreme to help prevent unwanted sound reflections in this small concave area. Cardas 15.5 gauge litz wire was used for the speakers internal wiring. A foot of red and a foot of black for each speaker was more than sufficient. Heatshrink was used around the soldered areas for a clean look.

Rear of the back plate

A healthy amount of speaker caulking was used to seal the area between the plate and the speaker opening to ensure a proper seal. Once the plate was set, a small brass wood screw was placed in each corner. The speaker caulking was then compressed and smoothed by hand around the back opening from the inside. 

Installation of the back plate

Fully installed

The front also had a smaller decorative plate made with a cute little horn icon.

Detail of the Planet10 FE126eN EnABLed driver

A beautiful set of Frugel Horns

In the interest of providing the Frugel Horns with a wider and more sure-footed stance, some outriggers needed to be fabricated. I chose to order a set of ten-inch wide aluminum bars that would attach to the speakers at the bottom and hold a carpet spike at each end. 

Bare aluminum bars to be used as outriggers

Each aluminum bar had four holes drilled, two for the outer carpet spikes, and two to run screws through to attach to the hurricane nuts in the speaker. All edges were sanded down to avoid a "barefoot surprise". Once sanded, they were given to the powdercoater for a matte black finish. A set of low-cost carpet spikes were selected from Partsexpress to mount to the newly painted outriggers. 

Black carpet spike from Partsexpress

Once these were mounted, the outtriggers could be mounted to the bottom of the speakers using 1/4-20 brass bolts which screw into the hurricane nuts that were mounted previously.

Outriggers mounted to bottom of speaker

The Frugel Horn is now finally complete.

The completed Frugel Horn

 

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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 Planet 10 Audio or Fostex. 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.