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.
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| 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.
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| PCB Crossover for Overnight Sensations |
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| 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.
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| 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.
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| Partsexpress Heavy Posts |
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| 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.
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| Wires running from the PCB |
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| 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.
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| 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.
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| 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.
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| 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!
