There are two kits available of the Overnight Sensations.
1. A kit from Parts Express, which includes drivers, electronics, and CNC-cut flat packs. This version uses the Dayton ND20FA-6 tweeter.
2. A kit from Meniscus which only includes drivers and electronics (you supply the cabinet). This version uses the HiVi T-20 tweeter.
This is a sort of generic writeup, which covers the basics of how the Overnight Sensations work.
I wish I had a time machine. I would go back to my bedroom when I was in Jr. High or High School and give these to myself. These are the little bookshelf speakers I imagined I had: huge soundstage, deep bass, tiny box. In reality, back then all I had were some impish Minimus-7s. Sure, they had a "tiny-but-mighty" quality about them, but come on, who was I kidding?
The "Overnight Sensations" were designed to be just that: a quick, economical build that could put out a surprisingly-big sound in a small box. Could be a weekender project for an addict, a gift for a teenager (see above), or--in my case--a set of small, full-bodied monitors that I could listen to while I graded papers. (Ironically, I have found that if the music sounds too good while I am trying to concentrate, I get distracted and get no work done.)
The cabinet for the Overnight Sensations can be built with ½” or ¾” MDF or plywood. The advantage of using thinner stock is that the cabinet is smaller and lighter. However, some prefer the added rigidity of thicker stock. If you use ¾” material, you should chamfer the woofer hole on the backside of the baffle using a router or file to give the cone some breathing room; this is not necessary with ½” material
One should be able to build a pair of these using only one 24”x48” "handypanel" of MDF or plywood available at your local home improvement store. You could probably also get away with doing something this small out of hardwood--and it would look really excellent--but please be mindful that hardwood does shrink and expand with the weather, so detachable baffles would probably be smart.
For this project, I decided to keep things simple, and did not countersink the drivers. The HiVi and Dayton drivers both have attractive, unobtrusive frames, so I just cut a simple 3 5/8" hole for the woofer and a 1 5/16" hole for the tweeter. The first one could possibly be done with a hole saw or jigsaw, should one not have access to a router. The tweeter hole can be done with a 1 1/4" forstner or spade drill bit and a bit of extra filing. Then again, if you want to properly countersink the drivers like a good cabinetmaker (and you have the tools), please do so.
The interior volume of the box is about 4.5 Liters. It is vented, and tuned to 53 Hz, which gives a -3 dB point in the mid 40 Hz range. The vent should be mounted on the back baffle, located somewhere behind the tweeter. Its exact location isn’t critical, as long as the vent openings are at least 1” away from any other surface inside or outside the cabinet.
In order to clear up confusion about the vent for the Overnight Sensations, I am spec'ing that one use the 1 3/8" ID Adjustable Port available from Parts Express. Simply glue the sliding portion so that the total vent length is 6". These are easy to mount and give a clean, professional look.
However, if you insist on saving a few bucks, you can use a piece of 1 1/4" SCH 40 PVC pipe. (Whose inner diameter is actually 1 3/8". Why? I have no idea.) This is available at any hardware store. The total vent length is 6" and must include the back baffle.
I should also add that this vent from Parts Express has been used by some builders. Due to its reduced diameter, the stock length of 4" is actually right on-target, so no cutting is required. The downside of this vent is that it's pushing the limits of port velocity. However, there are several very nice builds of the Overnight Sensations out there that use this port, so it must be OK.
The crossover for the Overnight Sensations uses a 3rd order electrical filter with an L-pad on the tweeter. The woofer uses a 2nd order electrical filter with C3 acting as an Elliptic notch filter. The acoustic slopes are fairly standard 4LR, and cross around 4000 Hz.
In a word: "big." The bass these little HiVi drivers can put out is tremendous. They throw out a very large soundstage and can actually fill a medium-sized room very well. I originally built these to sit on my desk, but since they have very full bass (or as some might say "full BSC"), they sounded best put up on a little stand or risor. Once I did that, I absolutely fell in love with listening to them in the nearfield. They image very well not only from left to right, but also in front of, and far behind the speakers. Although the frequency response looks pretty flat, the midrange is voiced with a very subtle droop; I did this out of concern that the metal-cone driver might get fatiguing or annoying after a while. The end result is a speaker that sounds good on most styles of music. Really bad recordings will be evident, but overall it's a pretty forgiving speaker.
One of my favorite uses for this speaker has been for those "wee hours" listening sessions, where it's not feasible to listen at full volume. What I mean is that, at softer listening levels (75 dB or less), large speakers tend to sound sort of unbalanced across the spectrum and thin in the bass--whereas small speakers seem to sound their best at quieter volumes. At these quiet listening levels, the wide and deep soundstage of the Overnight Sensations was still there in full form, letting me enjoy my music while my wife and neighbors slept.
Maybe it's just the belt-tightening economy, but this project seems to be one of my most popular. Some people have gone the simple route with construction (as the project was originally intended), while others have showed amazing attention to detail to make a tiny speaker that you can't help but marvel at.
First up is the highly-skilled woodworker and photographer Bill Schneider. His ability to plan steps ahead and problem-solve is very evident. His use of jigs and precision measurements is exemplary. This is DIY with machine-shop tolerances!
These came to life after playing with the stuffing. I put in about a fist-sized fluffed-out piece of stuffing near the back plate directly behind the woofer, and that did it. These things sound Way, WAY, WAY bigger than their small size would suggest! Paul nailed it - they would be perfect as the only speakers in a room with space limitations. They filled my medium sized listening room with BIG sound, and at one time, I had to check the switch to verify that they were the speakers playing instead of my main set.
If someone builds these, play the Reference Recording "Fiesta" to see how much of the lower registers they fill. These little things defy physics, and I'm tickled to have them!
Read the full version of his well-documented build thread here.
Next up is Mark [WWWJD] from the Parts Express board. He put everything and the kitchen sink into his version, and it's amazing! First of all, Mark constructed the speakers as "curvy" cabinets, using thin plywood bent around a frame. He then used a small amp kit from 41Hz.com and incorporated it (and volume controls, and LEDs) into the cabinet. To top it off, he used a beautiful quilted maple veneer on the sides.
Sound: Incredible, room filling; a bottom end that is impressive... I don't know all the words to use to fill in the blanks, but I'm stunned. I lucked out on the gains with the 50k pots and 10k mixing resistors... with the iPod wide open, more than enough volume with ZERO distortion that I can detect. First listen was Alice In Chains Unplugged.. Oh my! I have a huge list of others, but I had to quit so I could post this thread up.
Paul? Hats off brother. These little speakers pack a quality that's difficult to describe. I've listened to passages from Alison Krauss, Celtic Women.. Dark New Day.. Hans Zimmer.. Sting.. Dave Matthews.. George Straight.. AHH!! The list goes on and on... and these speakers sing. They literally have the ability to move me... you know? Ever listen to a song and feel it in your gut? Holy crap man. You've nailed DIY.
Read Mark's build diary here. He certainly took on a lot of unfamiliar territory--and succeeded. Great job!
Another build of the Overnight Sensations I found interesting was done by [djg] of the Parts Express board. He built a small 5.1 system, meant to shame the HTIB (Home Theater in a Box) systems they sell at the big box stores. It incorporates the work of 3 different designers to make the system. He used the three Overnight Sensations for mains and center, Zaph's B3N single-driver design for the surrounds, and RJB's Cerberus sub. The system was custom-built for a 13 year-old relative, what a lucky kid!
Link (The blog is in French, by the way)
here. Who knew DIY speakers could bring about family harmony?
this thread, which could be helpful regardless of woodworking skill.