PLAYBACK: BG Radia BGX-4850 THX Ultra2-certified subwoofer system

BG Radia BGX-4850
PLAYBACK: BG Radia BGX-4850 THX Ultra2-certified subwoofer system


About two years ago, I got a call from THX’s PR representatives asking if I’d like to take part in a briefing on the world’s first THX Ultra2-certified in-wall subwoofer system. Core technologies for the system, I was told, were being developed by THX chief scientist Laurie Fincham (perhaps best known for his achievements as the former Technical Director for the British speaker-maker KEF), while the resulting subwoofer system would be manufactured by BG Radia, of Carson City, NV. I was eager to learn what Fincham and BG Radia would do when given the freedom to create a world-class sub, so I signed up for the briefing and was soon introduced to a radical new woofer system design that breaks all the established rules, and for all the right reasons.

Let’s play a word association game. If I say “state-of-the-art subwoofer,” what thoughts first come to your mind? My bet is that you are picturing a big, honkin’ precision-made woofer (or two) loaded into a beefy, bank-vault-like enclosure and that is powered by a take-no-prisoners amplifier with enough output to propel a hybrid car. Well, apart from the amplifier part of the equation, let me tell you that the BGX-4850 subwoofer system ($6995) is nothing like that.

Flying in the face of tradition, Fincham and the BG Radia team have developed a multi-component woofer system comprised of four extremely compact yet very high output in-wall woofer modules that are—get this—inherently vibration canceling, plus an outboard controller/amp module to power them. Interestingly, Fincham never saw the in-wall aspect of the system as a performance-limiting factor. On the contrary, he felt the size constraints of an in-wall sub compelled him to think—quite literally—“outside the box” to create new woofer technologies that offer a fundamentally better-sounding way of reproducing bass frequencies. To appreciate the true character of this BG Radia woofer system, then, don’t think of it as an in-wall product, per se, but rather as a world-class sub that also just happens to support in-wall mounting.

Specifically, the BGX-4850 subwoofer system is meant to address five specific design goals:

  • Provide THX Ultra2-certified output capabilities.
  • Achieve well-distributed and extremely evenly balanced bass response throughout the listening room.
  • Deliver excellent low-frequency extension with exceptionally fast transient response, great pitch definition, and terrific timbral purity.
  • Achieve all of the above in a compact and virtually invisible in-wall format.
  • Achieve all of the above in a design that cancels out woofer cabinet vibrations, thus minimizing problems with resonance and vibrations in wall studs and/or sheetrock panels (problems that can crop up with high-output subs of any kind).

As the THX/BG Radia press briefing came to a close back in 2007 I expected that a production-release version of the BGX-4850 system would appear within a few months, but it was not to be. When manufacturers are chasing state-of-the-art performance it can take longer than you’d think to get those final few product details just right, which was certainly the case with BG Radia’s new super woofer. Trade shows came and went yet the final production version of the BGX-4850 system remained tantalizingly beyond reach—until just recently. But as you’ll see in a moment, it was worth the wait.


Consider this subwoofer system if: you judge subs by their sound, not by their looks. (BG’s system looks fine, but—in in-wall form—is essentially invisible). This system performs exactly as advertised; it provides high output, deep bass extension, lightning fast transient response, great pitch definition and timbral purity, and evenly balanced bass output all over the room. Unorthodox though it may be, this is one of the two or three best subs I’ve heard at any price.  

Look further if: you want massive “trophy subs” to show off to your buddies (the BGX system duplicates the output of two conventional 18-inchers, but is low on “bling factor”). Look further, too, if you are cost conscious or require an in-room solution (BG’s in-room enclosures won’t be available ‘til later this year). The only serious omission is lack of a built-in room/sub EQ system—a touch we would certainly expect in a woofer system in this price/performance class.

Ratings (compared to other top-tier subwoofers):

  • Bass Extension: 10
  • Bass Pitch Definition: 10
  • Bass Dynamics: 10
  • Value: 7



  • The BGX-4850 subwoofer system consists of five main components: four SM-1250 in-wall woofer modules (with grilles), and a standalone, rack mountable, remote controlled BGA-2104 subwoofer amplifier.
  •  THX Ultra2 certification guarantees low frequency extension down to 25 Hz (or better) at -3dB, and assurance that the sub is capable of THX Reference Level output in rooms up to 3000 cubic feet.
  • Billed as “the world’s first THX Ultra2 in-wall subwoofer,” the BGX-4850 system’s compact woofer modules comfortably fit within the stud spaces of interior walls framed with 2” x 4” studs. Alternatively, the woofer modules could be mounted in a ceiling, or even slipped under couches or shallow cabinets.
  • BG’s SM-1250 woofer enclosures use proprietary THX Balanced Bass-line technology to cancel out woofer cabinet vibrations. Fincham’s ingenious, “boxer-style” enclosure features two sets of six drivers that are horizontally opposed and arranged so that their diaphragms pump inward and then outward in unison, so that vibration forces exactly cancel out. Sound is output through a forward facing slot that measures roughly 2” x 22.5”. Even when the woofers are playing loud and low, the enclosures housings exhibit virtually no discernible vibration.
  • BG’s multi-woofer module format allows modules to be positioned within as many as four wall surfaces for exceptionally even and well-balanced in-room bass response. (Example: in the Playback lab the system delivers bass response of 18Hz to well over 100Hz, ± 2-3dB, across multiple listening locations at once).
  • The BG Radia system uses a total of 48 small-diameter 4-inch drivers (12 in each woofer module) that are light, fast, and responsive—yet that offer bass extension below 20 Hz. The upshot is a subwoofer that is powerful and goes deep, yet that sounds audibly “faster,” more nuanced, and more transparent than most. Interestingly, BG’s 48 small drivers have the combined radiating area of two conventional 18-inch woofers, so high output is never a problem.
  • BG Radia offers separate in-wall mounting kits for both new construction applications and retrofit applications. Recognizing, however, that some customers will require an in-room solution, BG Radia has teamed with acclaimed industrial designer Allen Boothroyd (co-founder of Meridian Audio, Ltd.) to develop a combo on-wall/in-room enclosure for the SM-1250 woofer modules. The in-room enclosures are slated for release later this year.
  • The electronic “heart” of the system is BG Radia’s BGA-2104 Subwoofer amplifier with provides 2200 watts of power, extensive control functions including DSP and a remote control.



Not long ago, I met with BG Radia National Sales Manager Tony Weber to talk about (and install) the BGX-4850 subwoofer system, and one of Weber’s first comments was that it was a “subwoofer that doesn’t sound like one.” By this Tony meant that the system does all the things you would normally want a subwoofer to do (i.e., it goes very low, plays loudly without distress, and offers good, smooth in-room bass response), but without incurring any of the undesirable side effects most subwoofers typically impose. What side effects are those? 

Well, to be blunt, many subwoofers impart a subtle (or perhaps not-so-subtle) quality of sonic “thickness,” as if the system is becoming progressively less nimble and articulate as frequencies drop lower and lower. Many listeners, in fact, describe this as a problem with “slow” bass, or complain that there are audible discontinuities between their main speaker system and subwoofers—especially in terms of transient speed (that is, the ability to respond rapidly to fast-rising bass notes) or textural definition.

For obvious reasons, the “holy grail” of subwoofer performance is to be able to play loudly, smoothly and with terrific bass extension, yet without introducing any problems with bass “sluggishness” of any kind, and in a nutshell this is precisely the balance point that the BG Radia system addresses as well if not better than any other subwoofer system I’ve heard. The BGX-4850 can do the “loud-‘n’-low” thing with the best of them, but where it really shines is higher up in the crossover region where output transitions from the sub to the main system. The BG Radia system is easily one of the (if not the) fastest and most articulate subwoofer systems I’ve heard at any price. In fact, in the critical upper bass region, it is one of the few subs that might actually sound clearer and more articulate than some of the main systems with which it could be used.

How can this be? The answer involves two important BG Radia design decisions. First, by using many small bass drivers (48 x 4-inch units) rather than a few much larger and more massive woofers, BG Radia has produced a woofer that not only moves huge quantities of air at low frequencies but that—quite remarkably—offers flat frequency response all the way up to about 4.5kHz (a claim few if any other subs can make with a straight face). Second, BG Radia’s THX Balanced Bass Line cabinets effectively eliminate problems with cabinet resonance, which can be a huge problems with many box type subs. Even when the BGX-4850 is belting out powerful deep bass, you can put your hands on the BG woofer enclosures and pretty much feel, well, nothing at all. Though I admit that it initially seems a bit strange, it’s a wonderful thing to experience powerful and articulate bass with no cabinet shakes, quakes, or bad vibes of any kind.


I’ve experienced many good (and some great) subwoofers that would play loud-‘n’-low when movies soundtracks so required, but I don’t think I’ve ever experienced a bass system that combined output, extension, speed, and clarity as effectively as the BGX-4850 does. And on some soundtracks this proved an out-and-out revelation. Long term Playback readers know that I’m fond of using The Strangers as an A/V test disc, but once I plugged the BGX-4850 rig into my reference system the BG Radia woofers started revealing things I’d never heard before (at least not so clearly) in the film’s soundtrack. For instance, in the “Back Again” sequence, when Kristen McKay (Liv Tyler) is left alone in the summer home and confronts the creepy return of the strangers, the sound designers symbolize the immediacy of the threat through the hard, sharp, low frequency sound of loud knocks on the front door in the middle of the night. These the BG Radia system reproduced with startling acuity and force. But to suggest the mounting eeriness of the whole scenario, the soundtrack also presents richly textured very low frequency “washes” coupled with the mysterious, deep ringing sounds of what appear to be giant temple bells or gongs.  The sounds are fairly loud but also so low-pitched that some subs miss them (or at least their lowest layers), but through the BG system they were oh-so-clear and dark, deep and ominous enough to send chills up my spine. 

Another film that I find provides a great subwoofer workout is Clint Eastwood’s classic Sands of Iwo Jima. I’ve often commented on the visceral power of the scenes where Japanese soldiers are hunkered down in their island caves while we hear American artillery shells exploding overhead. These scenes have always been effective in the past, but rose to a whole new level of excellence with the BG Radia subwoofer in play. Here’s why. Normally, with standard subs in the Playback reference system, you’ll hear the “boom” of a shell going off followed a split second later higher pitched textural sound of dirt and debris raining down from the roof of the cave. This is all well and good, but what I had not realized—until the BG Radia system came along—was that there was something missing: namely, the abrupt, ultra-low-frequency, slap-in-the-face concussion that results when any explosion occurs. With the BGX-4850 system in play, though, I could not only hear but feel the concussive jolt as shells landed, followed in infinitesimal split-second by the booming after report of the explosion. This may seem a small distinction, but it’s one that shows how the BG Radia system’s combination of raw power and transient speed can dramatically enhance realism.



In many cases, I suspect, audiophiles are inclined to dismiss in-wall subwoofers as inherently flawed designs, which make it all the more ironic that BG Radia’s in-wall subwoofer system has proven to be one of the most musically satisfying audiophile-grade subs I’ve ever heard. (Two of my other favorites are the critically acclaimed JL Audio Fathom-series subs, which Playback uses as its reference, and the Wilson Benesch Torus Infrasonic Generator). What makes the BGX-4850 system click, really, is again that mellifluous combination of bass extension, power, resolution and speed.

In may cases, audiophiles prefer to cross in subs (if they use them at all) at very low frequencies, so that the subs won’t spoil the timbral purity of their main speakers and you can use the BGX-4850 system in that way and with excellent results. But frankly, BG Radia’s system is so fast and transparent sounding that you can also use what are, by audiophile standards, much higher crossover frequencies—such as 60 or 80Hz—without losing bass clarity or focus. As an experiment, I tried using the BG-Radia system with both low and high crossover points, and got very good results in both cases. 

I put on the third “Volcano” movement of Hovhaness’s Mount St. Helens symphony [Telarc, multichannel SACD] to listen to the eruption passages and was floored (almost literally) by the tautness of the BG Radia’s sound as it reproduced the low percussion drum thwacks the composer uses to symbolize the violent force of the volcano’s self-destruction.  Many good subs can capture the bass weight and impact of those drums, but few can do what the BG Radia system did, which was to go further to capture rippling “skin sounds” of the drums along with the booming body of their notes. As the eruption unfolds, Hovanhess introduces a low brass theme while keeping the bass percussion motif going to suggest the downhill flow of lava and debris. Even when reproducing multiple layers of complex bass content, the BG Radia system kept things clean, clear, and well defined (a feat not many subs could duplicate).

Similarly, on the “Blues for Junior” track from Ray Brown, Monty Alexander and Russell Malone’s eponymous album [Telarc, multichannel SACD], there is a wonderfully expressive Ray Brown bass solo where Brown walks up and down his instrument’s fingerboard creating runs of notes that, as it happens, pass up and down over the crossover point between the subwoofer system and the main speakers. What wowed me about this solo was how beautifully integrated the subwoofer sounded, so that there were essentially no textural discontinuities to be heard (though in truth, if I had had even more time to play with very small phase adjustments, I think I might have been able to achieve an even tighter sense of bass focus). But even as things were, Brown’s solo bass exhibited a pleasingly balanced, “cut-from-whole-cloth” sound that is very difficult to achieve with most subs. And that’s where the BG Radia system really proved its merits.


In writing this review, one of my fears was that readers would come away thinking, “’sounds like BG Radia’s subwoofer system is pretty good—for an in-wall design.” It is a great in-wall design, but the fact is that it goes much further than that. In truth, the BGX-4850 system is a world-class subwoofer that just happens to also comport with in-wall form factors. This sub does it all: deep bass, high output, terrific definition and clarity, and smooth and even distribution of bass throughout the listening room. Even though the BG Radia system’s form factor is unorthodox, I would encourage anyone seeking a top-tier subwoofer system to hear it before making a final purchase decision. It’s that good.


BG Radia BGX-4850 THX Ultra2 subwoofer system

Driver complement: Four SM-1250 in-wall woofer modules, each with twelve 4-inch, long-throw bass drivers.
Outboard power amplifier: 2200 watts
Dimensions, SM-1250 woofer module (HxWxD): 26.75” x 14.5” x 3.5”’
Dimensions, SM-1250 grills (H x W):  28” x 7” (new construction grill), 29.5” x 15” (retrofit grill)
Dimensions, BGA-2104 subwoofer amplifier (HxWxD): Not specified
Weight, SM-1250 woofer module: 30 lbs., ea.
Weight, BGA-2104 subwoofer amplifier: 20lbs.
Warranty: Lifetime, parts and labor, for the woofer modules; five years, parts and labor, for the subwoofer amplifier.
System price: $6995

(775) 884-1900

blog comments powered by Disqus

Featured Articles