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Infinity Beta Series Speakers: 50 Towers, C360 Center, ES250 Surrounds, and CSW-10 Subwoofer

Part II

February, 2005

Colin Miller


The Towers

The Beta 50s are a 3-way design, with one 1” tweeter, one 5” midrange driver, and two 8” woofers, loaded in a bass-reflex system with a port to the rear. As with all speakers using rear ports, give them at least 6 inches or so away from the wall behind them. Otherwise, the nearby boundaries might inadvertently change the reflex system’s tuning frequency.

It is entirely possible that we might want them even farther into the room for other acoustic reasons anyway, but consider that distance a minimum, particularly if the speakers are running ‘full-range’ to a substantial degree, i.e., not benefiting from bass management.

The Beta 50 towers are rated to 35 Hz –3 dB, 30 Hz – 6 dB. Loudspeaker specs provided by manufacturers are probably the numbers I take least seriously, as low frequency extension, or for that matter the speaker’s in-room response, will vary considerably with the specifics of placement and acoustics. Still, 35 Hz can provide some satisfying bottom end, almost what you could call a ‘full-range’ loudspeaker, but you bass aficionados will not be assuaged, and will want a subwoofer to handle that last octave, if not the bottom two, as well as a half octave below that for you infra-freaks.

With the Beta 50, as with all of the speakers, I applied an 80 Hz crossover frequency in the bass management setup, as whatever the Beta 50 could do, the CSW-10 subwoofer could do better, particularly if the R.A.B.O.S. happened to be good for the room acoustics scenario, but we’ll get to that.

The Beta 50 towers also offered binding posts that make bi-wiring and passive bi-amping an option, though personally I wouldn’t recommend bothering with either. If you’ve got some otherwise good amps with limited current delivery capacity that you prefer to keep for sentimental or financial reasons, I’ll sign on to passive bi-amping. As to the bi-wiring thing, if anybody can track me down at CEDIA next to a white board, I can show how bi-wiring might make a difference under certain unlikely conditions, and why you wouldn’t want that unless you like oscillations or peaks at the crossover frequency. But hey, if you like it, you can do it!

The Center

Not only does the C360 have a handy adjustable leg on the back of the enclosure to optimize the downward angle where the speaker is placed substantially above the listening height, it is also a good example of a center channel driver array done correctly.

The most typical MTM (Midrange Tweeter Midrange) type center channels, though aesthetically pleasing in their slim profile and symmetrical layout, more often than not suffer horizontal off-axis lobing in the midrange spectrum, as the output of each spaced midrange driver is significantly delayed relative to the other when listening to the side, and we get selective cancellation at frequencies where the resulting phase shift is close to some iteration of 1800 (5400, 9000, 12600, etc), and we thereby find comb filtering that shifts in nature as you move, resulting in dialogue difficult for those seated at the side of the couch to understand.

The C360 is instead a 3-way design, with a vertical, closely located midrange and tweeter assembly (one 1” tweeter with one 4” midrange driver) that will have just as even, if not more even dispersion than the Beta 50 towers. That arrangement is then augmented by two 6 ½” woofers to keep the single mid from heaving large amounts of air with its wee cone. At lower frequencies, even as high as 200 Hz, the wavelengths are long enough that the degree of spacing between the woofers doesn’t result in substantial cancellation, even 450 off-axis.

For instance, if the drivers are spaced even two feet apart (in the C360, they’re only about 1 ½’), that results in a 1.4’ distance difference when listening 450 off axis, which is an extreme example. At 200 Hz, our wavelength is about 5.5 feet, resulting in about a 900 phase shift, not enough to cancel, but rather theoretically just a 3 dB dip due to the lack of constructive summing. A 3 dB variation at 450 off-axis isn’t bad at all. Other examples are illustrated in the table shown below.

Ft/Sec Hz Wavelength Distance Percent Shift Phase Shift (Deg) Relative phase
1100 200 5.5 1.4 0.3 92 92
1100 250 4.4 1.4 0.3 115 115
1100 300 3.7 1.4 0.4 137 137
1100 393 2.8 1.4 0.5 180 180
1100 786 1.4 1.4 1.0 360 0
1100 1179 0.9 1.4 1.5 540 180
1100 1572 0.7 1.4 2.0 720 0
1100 1965 0.6 1.4 2.5 900 180
1100 2358 0.5 1.4 3.0 1080 10
1100 2750 0.4 1.4 3.5 1260 180
1100 3143 0.3 1.4 4.0 1440 0
Big Dips (most cancellation)


Peaks (most not cancelled)

As the frequency increases, you can see that you’ll get really steep dips at 393 Hz, 1,179 Hz, 1,965Hz, and 2,750 Hz. You’d also, as a result, have relative peaks (simply not cancelled output) at 786 Hz, 1,572 Hz, 2,358 Hz, and 3,143 Hz. Certainly not a smooth listening experience. But, anyway . . . .

Going much higher in frequency with relatively wide spacing shows the problems with a horizontal MTM array, where spaced midrange drivers operate over a much wider range. Granted, 2 feet is relatively wide, even for an MTM, and 450 off axis is on the edge of expected listening areas, and 1100 ft/second is just an approximate speed of sound (which will depend on atmospheric pressure and humidity), but it illustrates the point of what could happen over the working range of a hypothetical midrange driver in such a scenario.

The Surrounds

As surround speakers, the ES250 speakers don’t look unusual. There are two sets of drivers oriented front/back, as many others, to potentially provide a more diffuse surround field. Like the Beta 50 towers, the ES250 speakers have dual binding posts, but not for the typical bi-wire/bi-amp options, but rather to make use of the little switch on the other side. That switch allows the speakers to operate in a bipolar mode (both sets of drivers in-phase), dipolar mode (theoretically one set of drivers out of phase with the other, though I suspect that they just switch the polarity of one tweeter, as woofers out of phase would nullify almost all bass response), or as a monopole (just one set of drivers working).

When using any of these modes, you keep the shorting straps connected between the binding posts. However, should you put the switch into bipolar mode and remove the shorting straps, you can use the single speaker as two, to either use a single pair as both surround and rear speakers, or to use a single speaker as the rear pair in a THX EX or Dolby EX mode, or whatever other purpose we can find useful. I settled on the simple bipolar radiation pattern for my needs, directional enough for a specific pan, but spread enough to keep things from clumping, though mileage will certainly vary with preference, placement, and environment.

Getting to the Bottom - The CSW-10

The CSW-10 (which is not formally part of the Beta series) is incredibly heavy for its size. The cone is pretty with its big fat light gray rubber surround. The amplifier is listed as capable of delivering 650 watts to the driver, though when you’re talking about a whole amplifier/speaker system, the rated amplifier power doesn’t really mean a whole lot without knowing the efficiency of the rest of what it’s driving.

The CSW-10 is a relatively small sealed system. Sealed systems are great in many ways, but unlike reflex systems, the entire air displacement must be fronted directly by the driver, and as such sealed systems generally have less maximum output when compared to reflex systems at or slightly above the tuned frequency of the particular reflex-based unit. In most cases, I’ve preferred sealed systems for sound quality, in part because of the shallower roll-off that tends to complement room gain to deliver good output below the listed –3 dB cutoff spec, and that it’s inherently easier to deliver tight, controlled, smooth bass. However, there are always exceptions on both sides of the fence, and I’ve certainly had the pleasure to witness some excellent bass reflex subwoofers as well, so don’t take my comments too seriously.

Where the CSW-10 actually starts to get more useful than your average bear, in terms of features, is R.A.B.O.S. This nice collection of capital letters stands for "Room Adaptive Bass Optimization System". When speaking to people I’m not trying to impress, I would call this a notch filter and some dealie whops, such as an SPL meter, a circular variation of a slide ruler to derive settings from a plotted curve, a CD with test tones, and some paper to plot your room response. Basically, it means that you place the subwoofer and plot the response using the test tones on the included CD. If the arrangement results in any substantial room response peaks that makes for ‘one note’ booming bass that lacks definition and poise, either plug in your numbers on the Infinity web site, or adjust the sliding dial so that the curves fit the plot, and you get your settings for the notch filter. This is a truly handy and useful feature.

This round, I didn’t have any use for the offered room compensation system, but I can attest to the value of well-calibrated notch filters with subwoofers to address problematic acoustics. I currently control room resonance and minimize cancellations with multiple subwoofers. In fact, with my current arrangement, a single subwoofer just won’t work at all with my combination of available locations and listening position, the very reason I insisted on two CSW-10s or none at all.

However, there was a time when I had a pretty hefty spike at about 44 Hz with a different room orientation and a single subwoofer, which made the bass unbearably overwhelming and distracting, regardless of the subwoofer channel level. When I finally got the notch filter depth and width adjusted on the Anthem AVM-20, it made a world of difference. Where before the bass response was bloated, fat, subjectively slow, and lacking in control, the result after applying the notch filter was exactly the opposite. Bass was tight, lean, clean, but mean, subjectively ‘quick’ in character, putting forth well-defined attacks with little perceived overhang in sounds.

Even though I don’t currently have use for notch filters, I advocate their use handily when subwoofer placement options don’t suffice in controlling ‘room boom’. One thing about this variation that I thought quite neat was the fact that when the R.A.B.O.S filter attenuates the peak, it also compensates the broadband level so that the average amount of bass won’t decrease. Of course, you could always recalibrate the level after flattening the response, but I thought it was nifty nonetheless.

Back to the Whole of It

While I’ve always been most critical about music listening, these days my A/V gear does more children’s movies than anything else. Many of these soundtracks are entirely deserving of good equipment, and occasionally demanding.

Overall, I would say that the first thing I noticed about the sound was how little I noticed. Any flaws inherent to these loudspeakers sit on the subtle side. The sound overall is smooth, but not smeared, the tonal balance is even across the entire range, as opposed to thick and chesty or bright and spitty, and the transition between each speaker across the soundstage is gradual, consistent, and seamless.

With the pair of CSW-10 subwoofers, I never found the amount of extension lacking, or their dynamic capabilities limiting under normal use. The quality of the sound doesn’t hit your face and scream, “Hey listen to me, I’m a subwoofer”, but rather does what it should, simply put the sound into the room such that one might just think that the Beta 50 tower loudspeakers had ridiculously good bass extension, or better yet let you forget about the speakers and listen to the performance. While the CSW-10 isn’t an Atlas compared to the bigger Velodyne, M&K, or SVS units, it’s no miser on performance, and when it belts it out, it's utterly sweet, and even seismic in measured amounts. Whether during the more infrasonic-heavy scenes of Finding Nemo, or in the beginning of Toy Story 2 when Buzz Lightyear breaks into Emperor Zurg’s Fortress, the CSW-10 delivered the goods in the lowest registers.

The C360 and the Beta 50 towers formed an impressive front array. Even though I’m generally an advocate for identical speakers for the left, center, and right channels, as I commented before, the blending of the whole system was just fine across the front, and around the rears the character remained constant, with even, smooth pans from front to rear or left to right.

In terms of articulation, I never felt myself straining to understand dialogue, especially in Chinese (Hero is a fantastic movie, and fantastic-sounding, I must buy!) My neighbors commented more than a few times how much they liked it as well. These Betas certainly passed the pet test, perking the ears of my cutie pie Rottweiler whenever sounds of dogs or wolves came up, for whatever indication that might make. My dog is pretty old.

When it comes to dynamic limitations, assuming adequate amplifier power, these things will play most anything loud enough to cause hearing damage without serious subjective distress. I don’t generally listen very loud, and am of the ilk who thinks that with most material, if somebody thinks that reference level is anything other than ‘show off your hardware for a few minutes’ volume, they’re nuts, and probably on their more rapid way to at least partial deafness. But, with loudspeakers, headroom is nice, as it means less dynamic compression and distortion at any level, and when you get near the upper end of the SPL range, it’s always nice when things don’t sound loud, in that horrid shrieking way, regardless of the decibel level.

It’s hard to say a whole lot about movies. I tend to get distracted following the story. Not surprisingly, I didn’t realize how truly good these speakers were until I seriously took some time for myself to have at ‘em with some good music.

Music Listening Notes

Roxy Music - Avalon, "Avalon".  Rounded but controlled bottom, good sense of space, not as precise in localization as my S-150Ps, but altogether open without being whacked out all over the place. Nice balance, able to hear the recording, but not assaulted by it.

John Fogerty - Déjà vu All Over Again, "Déjà vu All Over Again". Nice plink in the strings of guitar, kick drum good and thumpy without getting fat, but easy to hear the nature of decay. Vocals clear, not overly spitty or laid back. Proximity of the microphone was easily apparent, but by no means dominated the focus of attention. Overall, the panorama flowed rich, with a vibrant presentation, but absolutely non-fatiguing. Even the somewhat obnoxious and uber-compressed "She’s Got Baggage" was enjoyable enough to sit through its entirety, almost. I skipped to "I Will Walk With You" with its occasionally complex harmonies of lilting guitars and bass backup to lyrics, and "Rhubarb Pie", a banging folksy down home treat, during which I thought to myself, “Man, I like this bass,” but was also happy to just sit and enjoy the music between occasional notes.

Ben Harper - Burn to Shine, "Suzie Blue".  The ‘Voice in an old box and noise’ recording, vs. the subsequent ‘outing’ had a degree of contrast, though the ‘in a box’ sound wasn’t as contained as I like it, and as such not as dramatic when it opens up. Still, the staging had a nice blend of instruments without blurring. Horns and woodwinds maintained a natural character. Banjo, suspiciously but positively ‘over there in the corner’ behind and beyond the physical loudspeaker. Vocals less well-placed, kind of floating ambiguously, in part due to the more ‘open’ and ‘tall’ soundstage, but in part due to the nature of the recording, with little reverberant context given to the vocal track. Following, "Steal My Kisses", begins with a ‘spit box’ performance accompanied by an awesome bass assault. Clean attack lines, clean delineated percussion, cymbals didn’t have quite as much zing as I sometimes like, though I prefer a little softness in the treble compared to obviously too hot. Besides, it didn’t sound rolled-off at all, just a wee reticent.

Diana Krall - Love Scenes, "All or Nothing At All". An audiophile favorite, was rendered in full glory. Open, expansive, ‘you are there’ kind of presence. With a wonderful voice, great instruments, and a superb recording, it was an absolute pleasure, even if not nearly my musical favorite.

Bjork-Selmasongs, Music from the Motion Picture Dancer in the Dark, "Overture". Easily heard people breathing, speakers were able to convey depth behind them simultaneously portraying the most immediate. In the following track, "Cvalda", machinations of industrial sonics sewn and thrust together in an audio paella with Bjork’s incessant and exquisite vocals, pulled some soundstage and bottom-end tricks that actually colored me startled. The mix, though vivid and wild, is in many regards a complete mess of carefully tossed chaos, but I suspect that much of it is the point. A lot of what’s happening is absolutely nuts, with very complex passages and orchestrations, and the Beta 50s put that through without dumbing it down to a homogenous mush.

Bjork- Gling Glo- "Kata Rokkar". I had not an iota of a hint of what she’s saying, but through this entire Icelandic Jazz album, some of her recording of vocals and instrumentation is fabulous. Bass was naturally fat, piano lively and open, percussion entirely natural and unrestrained.

During "Pabbi Minn", brushes on the drum skins were great. Heck, this whole album is fantastic, and the Infinity Beta 50s and the CSW-10s didn’t seem to be holding anything back. When I first listened to the Debut album back in school, I don't think I would have believed anyone who would have told me that I was likely to enjoy Icelandic Jazz. I’d venture so far to say that if you at all like anything Bjork has done, you MUST get the Gling Glo album! As far as this relates to a product review, the Beta 50s and the CSW-10 subs did it magnificent justice.


Before there were diapers filled up to little belly buttons with mess, before I had to scramble to pay a mortgage and all of those annoying bills that seem to come with it, before sharing feelings and thoughts with someone you loved was a responsibility and compulsion, I used to just sit for hours listening to music, a facet of my life I looked forward to daily, often at the exclusion of almost anything else. That is why I got into Hi-Fi. The Infinity Betas are something I could easily live with on a long-term basis, and one of the better offerings I’ve had the pleasure to get my hands on in some time. Truly fine products, indeed. If you’re in the market, don’t mind looking in the mainstream, and have a good dealer handy, I certainly do recommend a test drive, preferably at home!

- Colin Miller -

Relevant Equipment used for this review and comparison.

Anthem AVM-30
Anthem MCA-50
Technics DVD-A10 DVD-V/DVD-A player
M&K S-150P Monitors
M&K S-250P Surround Monitors
SVS B-4 (parted into 4 individual sealed systems)
Crown K-1 power Amplifier (Subs)

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Primer - Speakers



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