The Cabinet & the Subwoofer Page 2

Sean Hotchkiss, technical director at Grand Home Automation (in Hudsonville, Michigan), told me that although the company prefers to install architectural subwoofers in their clients’ walls whenever possible, they regularly hide subs in cabinets, too. Rather than attempt to isolate an in-room subwoofer, they often mount in-wall subs into the cabinet’s structure. One way to do this, he mentioned, is to use Triad’s InCabinet Sub Adapter. According to Triad, the InCabinet Sub Adapter is a special bracket (for use with the company’s InWall Series subs) that’s designed to fit “between the subwoofer and the cabinet base and is primarily used when down-firing the subwoofer through the cabinet. The MDF adapter mates with the speaker box and provides needed isolation to prevent buzzing and unwanted noise.” If down-firing the sub through the cabinet’s bottom isn’t an option, Hotchkiss explained that you can mount an in-wall sub into a side of the cabinet in much the same way you’d install the sub in a wall.

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Near the end of our conversation, Hotchkiss stressed that airflow is important for another reason—one that people often forget or don’t realize. Powered subwoofers, he told me, like any other component in your system, generate heat. Heat, of course, can change the nature of how a component performs. Perhaps more important, it can also dramatically reduce its life span. So you have to take care to provide enough airflow around the integrated electronics to keep the heat from building up inside the cabinet.

Location, Location, Location
Dangerously armed with a little knowledge and a lot of overconfidence, I was ready to fire up the chain saw, strap a caulking gun to my belt, and basically re-engineer any nearby piece of furniture in my house. Fortunately, the kitchen cabinets and the piano were safe because BDI had shipped two cabinets my way for the express purpose of sneaking subwoofers inside. BDI’s Novia 8426 cabinet, as a matter of fact, was specifically designed to house a sub in a large hidden cavity located on the left side behind a shallow media storage area. The wide, quad-door Corridor 8179 wasn’t specifically designed to conceal a subwoofer, but we chose it because the internal cabinet sections are large enough to house a relatively hefty sub. By chance, I had two subs available as well: a $350 Atlantic Technology SB-900 (8-inch front-firing driver, ported, 125-watt internal amplifier) and a $999 GoldenEar ForceField 5 (12-inch front-firing active driver plus a 12.75 x 14.5-inch down-firing passive radiator, 1,500-watt switching amplifier).

As I mentioned, a subwoofer’s placement in the room has an enormous effect on its performance. Unfortunately, whereas you can work on rattles, resonances, and airflow in a cabinet, there’s usually little you can do about its location. Curious as to how much difference it would make, I listened to each of the subs in three locations: 1) at each sub’s individual optimum placement in the room; 2) inside each cabinet; and, in order to determine how much of an effect the cabinet itself had on the sub’s performance, 3) sitting next to each cabinet. I primarily used music tracks with hard-hitting bass and lots of dynamics, such as “Lemme Try Your Bass (Interlude)” from SMV’s Thunder, the Jennifer Warnes classic “Way Down Deep” (The Hunter), and selections from Pink Floyd’s The Dark Side of the Moon, among many others. In addition to music, I fed a sweep tone through the subs to pinpoint and isolate the rattle and resonance locations and attempt to fix them.

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It might surprise you to find out that the hidden-in-the-cabinet location wasn’t always the worst performing. In some cases, the subwoofer sounded better inside the furniture than sitting next to it—although I could never get an in-cabinet sub to sound as good as the same sub in its optimum room placement. One example came with the Atlantic Technology SB-900 sub in the BDI Corridor 8179 cabinet. The SB-900 was compact enough to test in several different orientations, including firing forward through the slotted door, firing backward toward the wall (with the cabinet’s back panel removed), and firing down through the large vent holes in the bottom of the cabinet with the sub propped up on squares of Acoustics First’s Vib-X Vibration Isolation Pads.

Firing back toward the wall was unbearable because, in addition to sounding boomy, the sub rattled the crap out of the wall. Situating the SB-900 so that it fired forward into the room produced reasonably respectable bass, certainly nowhere near as boomy as what the backward orientation generated. After I listened with the cabinet door open and then closed, I noticed that the door itself was restricting a small amount of the sub’s energy and dulling its character ever so slightly. Interestingly, the best bass performance came with the SB-900 firing down through the pre-cut holes in the bottom of the cabinet. (Since the cabinet sits on legs that raise it about 4 inches off the floor, I didn’t have to worry about venting toe kicks.) With the sub in this position, the bass output became much tighter and a bit deeper. It wasn’t the absolute best that the SB-900 could sound, but it was more than acceptable—much better than the sloppy, tubby bass from the sub sitting next to the cabinet, and for sure a hell of a lot better than it would sound in other locations that people might be tempted to use.

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My experience with the GoldenEar ForceField 5—one of the most impressive under-$1,000 subwoofers I’ve heard recently—was a bit different. The 18-inch depth of the sub prevented me from upending it and firing the active 12-inch driver down through the vent holes of the BDI Corridor 8179 cabinet. But I did test it facing into the room as well as facing toward the wall, with the passive radiator facing down in both instances. Once again, the wall-facing position battered the back wall mercilessly. The ForceField 5 performed better firing forward, but it lacked the dynamics and near-bowel-movement-inducing deep-bass output this sub creates in its ideal room placement. Placing the sub in the cabinet raised the radiator a good 6 inches from the floor boundary and changed its character significantly. Placing the sub next to the cabinet brought back some of the depth, but the overall sound was weak and failed to energize the room.

That’s not what happened with the BDI Novia 8426, however. Since that cabinet is designed to cover the subwoofer, I was able to place the GoldenEar ForceField 5 directly on the floor, with the active driver firing through the slots in the side of the cabinet. The bass regained some of its depth and fullness, but it still couldn’t rival what I knew the sub was capable of in the right spot. Atlantic’s SB-900 sounded pretty much the same inside the Novia 8426 or next to it on the outside; yet, as with the ForceField 5, the SB-900 still suffered from being “out of place.” One advantage of the Novia 8426’s design, however, is that I was able to set the SB-900 on top of one of Auralex Acoustics’ original SubDude models. The interesting combination of raising the SB-900 up off the floor approximately 2 inches along with having the acoustic isolation provided by the SubDude served to noticeably improve the nature of the sub’s sound. The SB-900 still sounded a bit tubby, but it gained control and texture.

Meeting Bass to Bass
What is there to conclude from all this moving and shaking of subwoofers and cabinets? The first rule of thumb for hiding a sub in furniture is that there is no first rule of thumb. There’s really no way to determine ahead of time the subtler aspects of how good a particular sub will sound in a certain cabinet at a set location in a given room. On the other hand, if you’re OK with sacrificing a little performance in return for making a sub disappear, and you’re willing to spend a little time experimenting plus a little cash chasing rattles and dampening resonances, it’s most definitely possible to get respectable performance out of a sub hidden in a piece of furniture. And if you choose the furniture wisely (see “Construction So Good, It Hertz”), you’ll minimize the effort required to adapt it for this role. As the Rolling Stones might have said it, “You can’t always get the bass you want. But if you try sometimes, you just might find, you get the bass that you need.”

Resources
Triad Speakers • (503) 256-2600 • triadspeakers.com
Acoustics First • (804) 342-2900 • acousticsfirst.com
SnapAV • (866) 424-4489 • snapav.com
Auralex Acoustics • (800) 959-3343 • auralex.com
BDI • (703) 803-6900 • bdiusa.com
Grand Home Automation • (616) 896-2010 • grandhome.com
Atlantic Technology • (781) 762-6300 • atlantictechnology.com
GoldenEar Technology • (410) 998-9134 • goldenear.com

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COMMENTS
Manbat's picture

VAF of Australia produce such a sub called the Platform:
http://www.vaf.com.au/picture-gallery.asp?dialog=true&file_id=34&folder_...

and
http://www.vaf.com.au/detail.asp?audio=Subwoofer&grunt=s200r26747

They can custom design the size of the unit. Cheers!

JayhawkLaw's picture

I'm no engineer, but am I'm I way off base in thinking that a lot of the problems associated with in-cabinet subs be at least alleviated by using a sealed sub like your recommended SVS SB-13 Ultra?

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