On Speaker Setup Options…

By Bryan Geyer

Revel M106 (grille off)

In 2012, we decided to “downsize” our retirement life. So we sold our house overlooking the bay and moved inland. We found a suitable 2 BR condo, set off-street, that was right in the downtown hub of a nearby coastal town. Of course, this downsizing process implied abandoning our existing audio system. Our big floor-standing full range loudspeakers and related 200 Watts/channel stereo power amplifier were too massive for our new condo—a consequence of great joy to our grandson. An all-new and much more compact system would now be necessary.

Our new condo LR was tight. Small bookshelf-type mini-monitor speakers would likely be necessary. Clap tests indicated favorable acoustics—the 10 foot ceiling and partially open back wall was clearly a benefit—so maybe I could rig something tolerable. Strictly as a test, I tried a pair of 4 inch desktop-type speakers, driven by a tiny 15 WPC class D power amplifier. The sound was promising. The room acoustics were clearly good enough to warrant serious effort.

Addressing what to get as the main speakers came first. There really wasn’t enough open front space to accommodate speaker stands; they’d be an obstruction. So any new speakers would either have to sit atop the brick fireplace mantle (just 8.5 inches deep) or get bolted directly to the brick facing below the mantle. The classic acoustic guideline about pulling the main speakers away from the front wall simply couldn’t be applied; it didn’t fit our layout. So I chose to use the mantle as the speakers’ shelf. I bought a pair of little BBC-type monitors—Spendor S3/5R2 (now superseded). They had a 5 inch Ø woofer and a 0.9 inch soft dome tweeter in fully sealed enclosures; weight 10.1 pounds each. A review is here…https://www.stereophile.com/content/spendor-s35rsup2sup-loudspeaker#1i6C3c8Fzmprgukb.97. The size is 6.4” wide x 11.2” high x 7.4” deep; street price $1,500/pair. These minuscule monitors have proved to sound truly excellent when not pushed beyond a sound pressure level = 83dB (C-weighted)* at the listening position. That’s pretty loud, but it’s certainly not audiophile “demo-level” loud. You need some +6 to +8dB more dynamic boost to reach that sacred listening level, and that’s definitely beyond what these small speakers can comfortably reproduce.

As anticipated, the bass response was marginal, so I had to augment the bottom with a pair of larger and more costly self-powered subwoofers. The subwoofer addition would have proved necessary with any mini-monitor speakers of this size, as 5 inch Ø woofers in a sealed enclosure will fall off rapidly from about 90Hz downward. (OK, 75 to 80Hz if they’re in a ported enclosure, but these were fully sealed.)

Placing the subwoofers didn’t pose a problem. The best location under these circumstances is generally in the two front corners, sitting very near the floor, with some angled toe-in, and that placement worked well in our LR. It’s best to apply fully sealed subs, not ported (and no passive drone cones), when they’re placed in this manner. Small enclosure size was desired, and we selected JL Audio E-Sub type e-110 self-powered subwoofers; refer…https://www.jlaudio.com/products/e110-ash-home-audio-e-sub-powered-subwoofers-96276. There’s a technically astute review here…https://www.audioholics.com/subwoofer-reviews/e-sub-e110-e112. This sub consumes some 1.8 cubic feet, and weighs 53 pounds each. They are the smallest fully-sealed high performance self-powered subwoofers that I have been able to find that also feature a continuously variable phase angle control in addition to a fully variable input level control. These two controls are absolutely vital in order to facilitate accurate phase angle matching of the subwoofers with the main speakers at the precise point of crossover. You cannot accurately match the waveform phase at the crossover frequency if the built-in delay option in the subwoofer provides only a 0˚-180˚ polarity inversion switch.

Given the small mini-monitors in use, I choose 96Hz as my crossover frequency for the main speaker/subwoofer split, and I used an external active crossover controller (Marchand XM66, refer…https://www.marchandelec.com/xm66.html) to apply Linkwitz-Riley full 4th order (-24dB/octave) filter slopes for both the low-pass and high-pass outputs. (The subwoofers’ internal crossovers were placed in bypass mode.) The use of this external active crossover control unit assures a level of accuracy, adjustment range, and setting convenience that’s not possible when using the subwoofers’ internal passband filters.

Gain matching and phase coherency matching of the subwoofers/mini-monitors is best done at the crossover frequency. This can be assured with precise visual accuracy by using the instrumented means described in this paper: https://classicalcandor.blogspot.com/2019/03/optimizing-subwoofer-integration-part-2.html.

So what’s significant here? Well, I found that the sound of my new compact system was better than I’d ever done before with big full-range main speakers. The articulation and clarity in the mid-to-upper bass octaves was now more apparent, presumably because that driver was no longer burdened with the need to handle any power-hungry low bass. And the liberated low bass now seemed more extended and authentic than I’d ever experienced when using my full-range speakers. Good subwoofers can woof!

Equally instructive was the new revelation that good sound doesn’t automatically mean big main speakers. Dumping those 5 foot tall floor-standers was a welcome reward. I never liked staring at them, and I was tired of the intrusive prominence that they presented in our main living room.

The only aspect where my mini-monitor setup falls short is in the ability to reach that last level of loud. You might not want to stretch all the way to the 90dB SPL (C-weighted) realm often, but it’s certainly nice to get there, cleanly, when you want to go full throttle. To reach 90dB+, use these speakers…https://www.revelspeakers.com/products/types/bookshelf/M106-.html?cgid=bookshelf&dwvar_M106-_color=Black-GLOBAL-Current.

These Revel M106 speakers are fairly hefty, at 18.5 pounds each, but just 8.3 inches wide by 15 inches tall. They’re 11 inches deep, so these speakers can’t sit on a mantle. I’ll mount mine a bit lower, on the brick fireplace facing, using these unobtrusive and capable brackets…https://www.rockvilleaudio.com/RHSB8/, and mate it to the brick via 1/4–20 machine screw anchors. These speakers are still of modest size, but they utilize a 6.5 inch Ø driver (see photo), so a 90dB SPL (C-weighted) target will be well within reach. The M106 is rear-ported, and ships with optional port plugs. In my intended mounting position the ports will be plugged. You can see a Stereophile review of the Revel M106 here…https://www.stereophile.com/content/revel-performa3-m106-loudspeaker. A more comprehensive review (by widely regarded design engineer David Rich) appears here…https://hometheaterhifi.com/reviews/speaker/bookshelf/revel-performa3-m106-2-way-bookshelf-monitor-loudspeaker-review-part-one/.

After all these many years (my hi-fi interest sparked in 1949, and I began to install home audio systems in 1955) I’m now certain that big floor-standing full-range loudspeakers are not the ultimate keystone anymore. Paired (or more) subwoofers, plus modest-sized main speakers, when managed by an external active crossover controller, promises a more compelling means. This latter approach presents a potentially more effective way to resolve some of the bass response limitations implicit with small room acoustics, and it materially improves your home decor freedom by eliminating the need to place two big monkey coffins in your face forever. Do consider this option when planning any audio system upgrade.

                                                                   

Bryan Geyer (January 2020)

*SPL as read on Nady DSM-1 digital SPL meter, slow-mode, averaged mean level, fixed-mounted on stand, at ear level, normal listening position.