Cabinet Design

The cabinet for the Overnight Sensations can be built with ½” or ¾” MDF or plywood.  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.

Notes On Ports

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.

Crossover Design

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.

Listening Impressions

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.

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