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May 4, 2021

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

Partsexpress binding 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!

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