Overnight SensationS Maxx

I don't know why I never thought of it before.

I have had many, many discussions with Meniscus (RIP), DIY Sound Group (now Cinergy), and various builders over the years about the limitations and complexity of the B3N version of the Overnight Sensations Center Channel. We all made the best of it, and I saw a lot of really nice builds of them out there. But there was no getting over the fact that the HiVi B3N, while being a spiritual cousin to the B4N, never could keep up in terms of SPL and bass.

Finally, one day Erich at DIY Sound Group said, "I don't know why you never did an MTMMM or MMTMM version of the Overnight Sensations, using the B4N." And the truth is, I didn't know why, either. But at that moment, I knew it needed to be done. I just made so much sense!

Now, like most clever ideas, actually bringing this design to life came with its own set of puzzles to solve, but I rarely back down from a creative challenge!

Enclosure Design

Tower Version

There's a bit of a paradox here. What we essentially have is a large, small speaker (or maybe a small, large speaker). On the one hand, it is relatively thin, and is made up of small, 4" drivers. On the other hand, it is 40-42" high, which is a bit on the tall side for a "small" floorstander. With all that said, however, I think it would blend well in the vast majority of people's living rooms (or bedrooms, or home theaters, or home office, etc), because of the thinness of the baffle and the handsome bronze cone of the B4Ns. As soon as I set them up in our living room, my wife immediately said, "These look really nice. Can we keep these around longer?" My tween-age son also took an immediate liking to their looks.

The internal volume is pretty much right at 30 Liters (or just over 1 cubic foot). The vent is 2.5" dia x 5.75" long, which tunes the speaker to 40 Hz. This gets us a -3 dB point (F3) around 39 Hz--pretty cool. For the vast majority of rock, pop, hip hop, or country, the bass should sound and feel nice and deep. However, for the lowest of Low-Frequency Effects and sub-bass, keep in mind that this is a 4" driver, and you may want to augment your setup with a dedicated subwoofer.

The cabinet can be built with either 3/4" or 1/2" stock. The cabinet has some bracing throughout to keep panel vibrations down, and the walls are lined with "eggcrate" foam.

Center Channel

Finally, after over 15 years, we have a dedicated Center Channel that is a perfect sonic and aesthetic match to the Overnight Sensations family. Again, nothing against the OS CC with the B3N, but that little 3" bugger is somewhat limited in sensitivity and total output. Now that problem is gone. A quad set of B4Ns is the perfect complement for any and all of the Overnight Sensations family.

The cabinet uses some simple bracing to tie the walls together, and, unlike the tower, is a sealed cabinet.

Crossover Design

In relation to the crossover topology of the rest of the Overnight Sensations, you can see the family resemblence here. The tweeter filter is almost identical to the one in the TM, MTM, and TMM; a few values were tweaked here and there to blend with the increased output of 4 woofers.

The woofer circuit has a few unique features, though. First, I went for 3rd order filter (instead of my normal 2nd order with a "tank" filter, as I did with all the other Overnight Sensations). Second, the astute of you may notice that C4 and R3 create a Zobel filter. I did this because I found that having this many "simple" voice coils at the same time was causing the impedance to rise too quickly through the passband, and making it hard to accurately filter it how I wanted. (In somewhat plainer English: a Zobel filter takes the impedance of a driver from a steep mountain climb down to a gentle stroll across the prairie.)

Finally, another quirk I did here was to add C5 as a "tank" filter to the bottom 2 woofers, because I found they were leaking too much treble without it.

This design is what is considered a 2.5-way speaker, where the top 2 woofers carry midrange and bass duty, while the bottom 2 only are supposed to play bass. I've done a fair amount of 2.5-ways in my day, and I've never had to filter it quite this aggressively before. In the end, it's all good; the net result is all about keeping tight control of these drivers, and making sure they all stay in their lane, and play their best.

Frequency Response

Forgive me for cropping the bass frequencies out of the graph here. However, I'm tired of explaining how MLS cannot measure below 300 Hz. The important things to notice here are that the upper Mids and Tweeter cross right around 4000 Hz, and the lower Mids start rolling off around 800 Hz, and are way out of the picture by the time it comes to playing treble. This helps keep imaging tight, and prevents "smearing" of the soundstage.

Impedance

The impedance for the Overnight Sensations Maxx is very benign. You should be able to play them through pretty much any old amp. Personally, I have been using a little Fosi Bluetooth amp on mine, which is great, because it completely hides out-of-sight, and my family and I can connect to it at-will from our phones or computers.

Listening Impressions

The goals for this project were the following:

Use the same drivers as the rest of the Overnight Sensations family
Make it look cool
Keep the same "3D imaging" from the rest of the Overnight Sensations, so it matches sonically--yet can stand on its own
Make sure it can play nice with whatever hi- or lo-fi equipment and music styles the DIYer likes
Keep it fun, inexpensive, and easy to build like the rest of the series

I believe it has hit all those marks. This is the "final form" of the Overnight Sensations. This pushes the parts and the design as far as they will go, and the results are fun as hell. From quiet, after hours listening sessions, to cranking it for fun, to watching a movie, the OS Maxx will deliver on all fronts.

by Paul Carmody | this page was last updated November 15, 2025

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