FROM THE PAGES OF

Acme Sound Low B-2 and B-4 Enclosures
"...you may never go back to your old cabinets again."

"If you’re a 5-string player, you can now fully realize the potential of your instrument thanks to a speaker with incredible speed and tremendous power handling. No longer will you have to forsake your lowest half-octave for the convenience of a compact enclosure. Nor will you need to carry a second, larger cabinet to produce low frequency fundamentals that you can feel as well as hear."

Sounds too good to be true, doesn’t it? Can you get big low-B tones from a cabinet as small as a 2x10? Acme Sound’s Low B cabinets are intended to do just that: cleanly reproduce the fundamental of a B string. “These speakers are designed to be very neutral-sounding,” says Andy Lewis, designer of the Low B system. “They won’t add a ‘tone’ or ‘character’ of its own to the signal.”

There are two main ingredients in Acme’s tone recipe. The first is a custom 3-way speaker system. Both enclosures use special 10” woofers designed to have a lower resonance (frequency), a deeper voice coil (for less distortion in the lows), and a longer excursion (amount of back-and-forth movement) than standard 10s. However, since these speakers are wound to go low, the trade-off is a dip in upper-midrange response. To counteract this, Acme uses a special 5” midrange driver that fills in the missing upper-mid details. (Another disadvantage is the amount of power required to drive the 10s. More on this later.) Further clarity in the highs is provided by a shallow-horn tweeter. When these components are combined via a rugged crossover, this full-range system produces bass down to 31Hz (the fundamental of the open B string) and highs up to 22kHz.

The second ingredient is a specially built Thiele-Small-aligned enclosure. By taking advantage of the “stressed panel” construction technique used in building aircraft, the cabinets have a very high stiffness-to-weight factor. Here’s how this works: The cabinet is built from birch plywood that’s held together with glue and screws. Then, braces of 2”x2” pine are placed inside the box at strategic points and small wedges of wood are hammered between the ends of the braces and the inner walls. This means the braces are actually pushing out on the inside of the shell. Why do this? “Stressing increases the stiffness of the panels so they won’t resonate,” says Lewis. “Basically, you want the resonant frequency of the enclosure to be as high as possible so it won’t interfere with the bass response of the woofers. If you look at the sides of enclosures, you can actually see the panels bowing out in the middle from the internal pressure.”

Stressed-panel construction not only has structural and sonic benefits, it keeps the enclosures light and portable. Most 4x10s use heavier plywood to produce the same level of stiffness, and they can be a bear to lift. But it’s easy to carry an Acme box, thanks to their light weight and perfectly placed handles (high and towards the front). These small, recessed handles may not be the most comfortable we’ve felt, but there’s a reason for that, too. “Cutting big holes in the sides of the box for large handles lowers the resonant frequency of the enclosure,” says Lewis. “Ultimately, the best handles are no handles at all.”

Do the Low B’s perform as promised? To test their limits, we set up both cabinets in our Sound-lab and connected them to a Demeter VTBP-201 tube preamp and Hafler Pro 5000 power amp. Our array of test basses included two 35”-scale 5-strings: a Modulus Sweetspot Custom SPi and a Lakland Deluxe 5. Other testing was performed in a live situation with a Gallien-Krueger 2000RB (1,000W RMS bridged mono) and an Eden WT 400 Traveler Plus head. We were especially skeptical about the 2x10, but this little guy filled the room with punchy, balanced bass all the way down to B. Witnesses were amazed that a 2x10 could put out so much clean low end. (“It sounds three times its size,” said one listener.) The 4x10 was especially beefy; since the mids are handled by a separate driver, they speak with a more robust quality than is heard with most two-way cabinets. They also disperse much more smoothly. Overall, the Acmes are very warm-sounding boxes without the usual spikes in the midrange and top end. The 2x10 is fat enough for small- to medium-sized gigs (a pair in stereo would be a great setup), while the 4x10 offers more volume.

These cabinets are an acquired taste, though. If you’re used to hearing your bass with lots of speaker coloration, you may find them a bit soft-sounding, even with the mid and high attenuators cranked. Rock and metal players who play with a pick, for instance, may miss the upper-end aggressiveness of “modern” 4x10 boxes. But jazz, fusion, and funk players will love the Acmes for their fast and-flawless sound. R&B, country, and reggae players will also dig their round and tubey tone. (A vintage P-Bass sounded great through the 4x10-perfect for blues.)

These cabinets do have a healthy appetite for power, though. We found we had to set the volume controls at higher than-normal settings, and the power amps tended to clip very easily. The 4x10 ate every last drop of our Hafler’s bridged-mono 900 watts. Even at this power level, the amp clipped with certain playing styles, such as slapping. Any distortion in the preamp or power amp will show up as nasty farting in these speakers—they’re not very forgiving. “As a general rule,” says Acme, “when distortion is heard from these speakers, it will be eliminated by increasing amplifier power. This is the unfortunate price we pay for a compact enclosure with extended bass”. Acme recommends an amplifier with at least 200 Watts RMS of power, although we’d suggest at least 350 watts (or more) for maximum headroom. In fact, the more power you apply to the speakers, the punchier they are. (The 4x10 handled the G-K’s 1,000 watts with ease!) Also, you have to rethink your approach to setting up your tone controls. It’s best to experiment with the mid and high attenuators on the back on the cabinet, rather than crank up the controls on your amp or bass. In general, the less EQ with these cabinets the better, as they don’t need the low-end boosting most cabinets require.

Want to try a Low B cabinet? Since the company sells only direct, you won’t be able to test one in a store. However, Acme does offer a two-week, no-risk trial period. And at less than 600 bucks for the 4x10, it’s hard to imagine a better deal on quality, well-built bass gear.(Shh... don’t tell Andy his cabinets are underpriced!)

The Acme Low B-2 and B-4 enclosures do require gobs of power for peak performance, but the end result is a rock-solid bottom end that will drive just about any band. And once you get used to hearing the true voice of your bass, you may never go back to your old cabinets again.

By Scott Malandrone (c)1996 Miller Freeman, Inc.
Reprinted from the November 1996 issue of Bass Player with permission.
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