• Home
  • blog
  • Soundscience Rockus 3D | 2.1 speaker system

Soundscience Rockus 3D | 2.1 speaker system

blog image

Our review of the Soundscience Rockus 3D | 2.1 by Antec is the first time that the acoustic analysis capability of the SPCR anechoic chamber and advanced acoustic analysis tools have been used for speaker testing. Happily, the test results have been helpful, shedding light on subjective impressions and putting the review on a more empirical footing. It was also a good excuse to revisit the AudioEngine A2 speakers, reviewed just before the anechoic chamber came into service.

Antec Sound Science Rockus 2.1

February 8, 2011 by Mike Chin

Product
rockus 3D | 2.1
Powered speakers with subwoofer
Supplier
Street Price
US$250

Diversification is the name of the game as the computer industry continues to morph and expand into a blurred convergence with all kinds of consumer electronics. There are many examples, and several distinct waves of diversification over the past decade. One of the most obviously successful was the iPod, which started the transformation of Apple into the most visible, celebrated consumer electronics brand of the early 21st century. Less visible to the average consumer but significant among PC brands was the diversification by memory and cooling companies into the retail power supply market, with Corsair probably the most successful in this sector. Another arena is solid state drives, now being supplied by many brands never before associated with digital storage.

Over the past year, audio accessories and components have become one of the hot grounds for diversification among many computer-related companies. Arctic Cooling, a cooling solutions provider, began marketing a big line of earphones and headphones last year. Zalman has also moved in that direction in recent months, now offering soundcards, headphones, and even amplifiers. Silverstone and Scythe both offered amplifiers for the PC for a while, and the latter now offers speakers as well. Aforementioned Corsair also jumped in recently with gaming headsets and speaker systems for PCs. Remember how computer audio began — a 1.5" throwaway speaker slapped somewhere in the chassis to beep codes, mostly about errors — and you’ll have to agree, things have come a long way… even though $4.99 at Newegg can still buy you a pair of "350W Multimedia Speakers Powerful life like Sound Quality Connects to Any Computer, TV, Boom Box, Shelf System, CD player, Windows 95, 98, 2000, XP and windows NT compatible."

Almost every reader knows that Antec has been a major case and power supply brand for over two decades. Even with all the new competition in the crowded retail case and power supply space, Antec still has strong market position and distribution in North America. But with the acceleration of mobile computing and the slow growth in traditional (read: ATX) desktop PC sales, it is no surprise that Antec, too, is branching out.

Antec’s move into audio seems to be a bit more focused and perhaps more cautious than most other IT brands. Soundscience is a new brand created for Antec’s audio line, and for the past couple of months, only a single product has been offered: The rockus 3D | 2.1 powered speaker system. The latter part of its name describes it as a 3-component system — left and right speakers with a center bass speaker that also holds the electronics, including the crossover, controls and amplifier.


Antec soundscience rockus™ 3D|2.1 official glamor shot.

In a recently launched Antec blog, Ryan Richards, Product Manager for Sound Science, wrote strong words about the rockus 3D | 2.1:

In the beginning I envisioned our first speakers as the perfect audio system to pair with our gaming and performance enclosures. What I ended up with, the rockus 2.1 system, not only accomplishes that goal but works equally well as a small home theater setup or a gaming console companion. The result? A sleek, well-balanced compact speaker system solution that’s easy to use and delivers a crisp, powerful audio experience to a wide-range of users.

In the process of developing the rockus speaker system, I relied heavily on our core expertise in enclosure engineering as well as PSU design. The years of making PC enclosures with a heavy focus on quiet acoustic performance (Sonata, Performance One) gave us a unique perspective on speaker design. Certain materials vibrate or rattle easily, which can cause distortion and a loss in audio quality. To avoid this, I chose very early in the development process to construct the rockus satellites entirely out of anodized aluminum – something no other PC speaker manufacturer does. Our experience with power supplies, like the EarthWatts series, helped us create an amplifier that is both powerful and efficient.

It is noteworthy that Antec set up a floor booth at the 2012 CES last month, with an enclosed room of perhaps 10 x 12′ size set up as a small living room, with a rockus™ 3D|2.1 speaker system providing sound for a big screen TV. This was after a 10-year hiatus from the CES show floor; Antec relied exclusively on demo suites at nearby hotels and catered mostly to corporate buyers, distributors, other existing customers, and the press. Our familiar Antec reps informed us that the main reasons for the change was to celebrate the start of Antec’s 25th year, and to provide exposure for the new Soundscience brand and Rockus speakers to the non-IT crowd. Remember that computers represent only a portion of the Consumer Electronics Show. TV, video, other home electronics, and audio — general home, car, mobile, PC-based, and high end — represents a big slice of the audience.

At the asking price of $250, it may be a little pricey compared to $5 next-to-monitor speakers, but this is still not a product that’s going after the high end. (What is high end audio? How about… "audio for the crazy and/or rich"? I did hear in a large Venetian Hotel demo room at CES a $105,000 pair of speakers powered by about the same value of electronics and source gear.) The angled design of the rockus satellites tells us that it is optimized for the intended applications identified by Ryan Richards: Atop a desk, on either side of the monitor or on the low, wide cabinets that big screen TVs are placed in most homes. The satellites tilt up at about a 30° angle, which points them to about the right height for a person at a desk, or for people sitting in lounge chairs 6~10" away from the TV. Pop music MP3s, gaming sound effects, and TV, movies, and home video sound is what these speakers will be asked to produce. The audio signal will likely come through a PC sound card, a gaming console, or TV.


Soundscience Rockus 3D | 2.1 speaker system comes double-packed.

Soundscience Rockus 3D | 2.1 Features
Feature Our Comment
Anodized aluminum satellites reduce vibration and minimize distortion, resulting in clear mid and sparkling high-range sound. Plus 3D-tuned drivers deliver audio optimized for soundscience’s 3Dsst™ technology. Aluminum cylindrical enclosures, OK. But 3D-tuned drivers? Uh… duh… yeah, sure! Give us a break!
Active Subwoofer with Passive Radiator creates an extended low frequency response, producing deep bass from a compact subwoofer enclosure, eliminating the need for a larger, bulkier subwoofer. Big claims for what looks like a 7" driver in a 18-liter box. Subwoofer suggests response down below audibility. Be real: It’s a center woofer.
Remote Control Pod – Easily adjust volume, 3D/music mode selection, muting and digital/analog input selection. It is wired, though.
Optical (TOSLINK) Input allows for direct connection of digital audio outputs on video game consoles, home A/V components, CD players, DVD/Blu-ray players, and more. No mention of D/A specifications anywhere.
Soundscience Rockus 3D | 2.1 Specifications
Dimensions Subwoofer: 13.8” (H) x 7.7” (W) x 10.6” (D)
350.5 mm (H) x 195.6 mm (W) x 269.2 mm (D)
Satellite Speakers: 5.7” (H) x 4.7” (W) x 6.3” (D)
144.8 mm (H) x 119.4 mm (W) x 160 mm (D)
Weight 8.5 kg / 18.7lbs
Output Total: 150W
Satellite Speakers: 25 Watts/each
Subwoofer: 100 Watts
Maximum SPL: 95dB
Inputs Analog – 3.5mm, RCA
Digital – Optical (TOSLINK)
Freq Response 10 Hz – 20 kHz
Box Contents 2 satellite speakers, subwoofer, remote controller
3.5mm to 3.5mm cable
speaker cable – 2 x RCA to open end
RCA to 3.5 mm cable, remote cable
Box Dimensions 13” (H) x 10” (D) x 21.6” (W)
330.2 mm(H) x 254.0 mm (D) x 548.6 mm (W)
Warranty 2 Years

The specifications don’t really tell much, though the maximum SPL of 95 dB is somewhat useful — I presume this is measured a meter from the system. There’s also no mention of Dolby, THX, DTS, SRS, etc: This system does not do this kind of signal decoding. Without any details, the power ratings are most likely peak numbers, not RMS or continuous. The one really glaring bunk is the specified low frequency limit of 10 Hz, which is patently absurd… unless it is 50 dB below the midrange signal level. For a speaker system to achieve 10 Hz response at 95 dB@1m, it would require something like multiple 18" woofers in giant enclosures and perhaps 500W to drive each one of them.

Never mind. There are always holes in tech marketing specs for consumers. Maybe it’s just a typo. Time to open up the package and take a closer look

A CLOSE LOOK


Tidily packed and protected in blocks of dreaded, eco-unfriendly styrofoam. Call this an official start to our anti-styrofoam packing campaign: I will point out and diss every product package that features materials that are not recycled and recyclable. This is especially disappointing, coming from a company whose PSU products are generally packed almost entirely with recycled cardboard.


The components consist of the center bass/amp box (with unremoveable grill cloth in front), the two satellites, a control knob, and cables to run the little parts to the center box. There is also a short user’s guide.

The speaker cables are phono plugs on the satellite ends and tinned bare wires on the center box end. For those who are unaware, phono plugs were originally designed for low level signals (like between preamp and amp, or source component to preamp) rather than the higher currents between amplifiers and speakers. Admittedly, they are in wide use among computer multimedia speakers, and these particular plugs and cables (18 gauge?) look reasonably hefty enough to handle 25W peaks.


The back side of the center unit (really hard to call it a subwoofer) is made of metal and has all the inputs, and outputs. The metal sheet doubles, most likely, as a heatsink for the electronics inside. It has to have three amps — 25W peak each for the left and right satellites, and 100W for the woofer, which is visible behind the slot grill. The passive radiator is apparently on the front. 3-conductor mini-plug and phono plug analog inputs or on the right, above the optical TOSLINK. Below that is a 3-position Bass Level switch, whose function is obvious. The plug for the wired knob remote is below that. Left and right spring loaded wire terminals run along the center. On the other side is the power switch and captive AC cord. It runs on 100~240 VAC, 50~60Hz. A notice on the right states maximum power consumption (AC) is 150W. There are some felt pads on the bottom panel that act as feet.


The remote control is actually a fairly large knob about 2" in diameter and almost as tall.

The remote is more sophisticated than it looks. To enable/disable the optical input, you press the little mode button on the side for three seconds when the system is powered on. There are LED indicators: Digital indicates engagement of the optical TOSLINK input (or not — LED goes off if not engaged), music for normal stereo, 3D for 3D effects, and Mute. The system always powers on in Mute. Pressing down on the top of the big knob unmutes it; pressing it again re-mutes it. When the big top knob is used as a volume control, there is no natural stop, it will spin as long as you keep turning it… but the volume doesn’t get any louder beyond a certain point. Does this controller work in the digital domain? Probably not.

The cable for the remote is about 5′ long, the same length as the speaker cables. At a desk, these cable lengths are fine, but with a big screen TV, they seem too short. Normally, the center bass unit would have to go to one side of the TV/cabinet. For the far satellite to reach the other side of the cabinet of a big TV (say 50" or bigger), the 5′ cable is not long enough. The speaker cables were too short for the 55" TV I tried it with. The center unit had to be left in the center, rather in the way. If the system was going to be installed permanently, at least one speaker cable would have to be replaced with a longer one.


The satellites are unique looking.

The satellites are an interesting design. The enclosure is a short aluminum extruded tube, nicely painted or anodized a slightly textured dark grey. Each speaker weighs 0.65 kg, and feels reasonably solid, with no rattles when it is shaken. The back end piece is made of plastic, though it took some effort to confirm, and there is a recess in the center for the phono jack input. Four Allen-head screw give it a very sturdy look. The shiny flange in the front suggests horn loading, but it’s only cosmetic, and it’s plastic, though the illusion of metal is pretty good. Looking past the thin weave cloth, you can see a hex-pattern grill beneath which the cone of the full range driver is visible. This hex-pattern grill is probably plastic and meant to protect the cone of the driver, but it does look rather obtrusive to use as a speaker grill: It is well known in audio circles that early diffraction of sound waves emanating from a speaker driver can lower sonic fidelity.

LISTENING IMPRESSIONS: AT THE DESK

A couple of years ago, I disclosed in the only other speaker review in SPCR before this one, that I hadn’t had speakers connected to my PC for at least five years. This is not true any more. I have had a single AudioEngine A2 speaker hooked up for a while — to hear the sound of various online videos, for the first listen of a downloaded song, quick check of an audio recording for posting up to SPCR, etc. The other speaker has been left disconnected, on a nearby shelf. It’s small and does not take up much desktop space… but I just didn’t feel the need for it.

Let me explain again: I’ve lived with high quality music playback systems all my life, and at some point along the way, I chose consciously not to subject myself to the painful limitations of computer speakers — not when there was a fabulously good sounding audio system in my living room. When I feel like listening to music while at my computer, I simply turn the stereo upstairs up to a fairly high level and keep my downstairs office doors open. I have remote access from my desktop PC to the Squeeze Center software that feeds uncompressed CD or higher quality music in FLAC format into the upstairs stereo. The sound that flows down from the upstairs stereo is much better and more natural than I have got from any speakers ever hooked up directly to my computers. Hence, any computer speakers are up against my "audiophile" snobbery, my lack of exposure to other PC speakers, and my natural bias against speakers at my computer desk.

The Soundscience Rockus 3D|2.1 were up against it, too.

They were duly hooked up via the analog input to the PC equipped now with an Asus Xonar Essence STX, a very nice 196 kHZ / 24-bit sound card. Satellites atop, center woofer under the desk, to the left of my feet. After my experience with the AudioEngine A2 speakers, I instinctively angled the Rockus satellites inward so that their central axes intersect in front of me. This would mean that both speakers would be laterally off axis. It is the same basic setup that I use for the front speakers in my home theater room, as it provides a sound stage that’s stable as one moves laterally (very nice on the sofa across the room). They were turned directly at me for a little while, but as expected, that made the sound much too "in my face."


Rockus satellites angled so their central axes intersect in front of the seated listener.

The Rockus speaker system was left hooked up there at my desk for a week, used willy-nilly, as I would have used the single speaker in the past. Here are some notes jotted randomly during this period:

  • Listening to stereo speakers on the desktop is so immersive, so nearfield! It’s almost like listening to headphone sometimes. Hard to have music just playing in the background… Duh! They’re in the foreground 2-3′ from your ears dummy!
  • When my feet touch the center speaker under the desk, the bass can feel kind of neat. Buzzes the toes. lol!
  • The speakers are sometimes too toppy — bright at the very high end on some material when there’s sound up there. A little thin in the midband sometimes.
  • Lots of detail… clear… no audible distortion.
  • Pulling down the top octave bar in the equalizer on MediaMonkey helps tame it. A little boost on the 250 and 500 Hz bars helps too.
  • It can play pretty loudly — but then I’m so close to them. Should be easy for any speaker to play this loud.
  • A movie is watchable with these on the 24" 1920×1200 monitor.
  • The 3D mode is sometimes OK with movies but don’t like it on music at all. Any kind of music. Sounds "phasey", too bloated or resonant in the midrange on lots of music.
  • 3D mode can make game sound effects more dramatic.
  • The remote control is handy. Just grab it and push or turn. No searching for the volume bar with the mouse… or reaching behind the satellite.

In summary, it was a more satisfying experience than I expected. Desktop listening is very different than what I am used to with my conventional aging high end stereo upstairs. Rather than an illusion of a stage on the side of the room where the speakers are, with desktop speaker listening, it is a much more immersive experience, kind of like headphones. I could get used to it… and the Rockus speakers do enough things right and few enough things wrong that they don’t get in the way of the sonic material most of the time. The upward angle of the satellites’ integral stand helps it a great deal. Listening on axis generally ends up sounding a bit too bright on some music, but that’s easy enough to avoid. The tone controls or equalizer settings available in any software music player also makes it easy to tame the top if it sounds too hot.

After this week of intermittent listening at the desk, I had a long phone chat with Han Liu, Antec’s primary product development manager, who was deeply involved in the Rockus project. I’ve known Han for years, back before the P180 case project which I worked on with him. Han confirmed that…

  • The Rockus is optimized for nearfield listening in a smallish room, and for use with a HTPC or big screen TV.
  • Its upper treble has been deliberately boosted to help compensate for the typically duller sound of typical high compression MP3s used by so many people to maximize the number of songs in their MP3 players. The high res FLAC files and low compression MP3s in my collection, Han felt, is probably representative of only a small portion of the potential user base of the Rockus speakers.
  • A satellites + center box speaker system is far easier to set up (and gains domestic acceptance far more easily) than full 5.1, 6.1 or 7.1 types of speaker systems. Just the number of speakers that have to be placed, and the cables that must be routed to them are enough to discourage many potential users/buyers — I can confirm with personal experience.
  • The D/A converter is from D2 Audio, running at 16-bit / 44.1 Khz. It accepts only PCM signals.

VERSUS AUDIOENGINE A2 AT THE DESKTOP

Since the sample speakers from two years ago are still kicking about here in my office, it was natural to run a comparison between them. The Rockus speakers were put aside, and the A2s put in their place, set up as shown below in that review.


The AudioEngine A2s angled so their central axes intersect in front of the seated listener… back in place after a week with the Rockus.

The contrast/comparison was interesting. Here are some of my notes from the couple of days spent again with the A2s.

  • The mids and highs are smoother on the A2s, but perhaps a bit more closed in.
  • Richer mid-band, voices usually sound more natural.
  • Bass is too fat sometimes, a bit artificial, doesn’t go as low as the Rockus.
  • The whole desktop resonates more than with the Rockus; must be because A2s are producing bass on the desktop. With the Rockus, the satellites are not producing any bass, Almost all of it is coming from the woofer box at my feet.

This last phenomenon made it less pleasant to turn up the volume at the desktop with the A2s than with the Rockus. Audioengine now offers a desktop stand made for these speakers that do pretty much what the Rockus satellite stands do: Tilt them up a bit. Being made of silicone rubber, maybe it reduces the bass/vibration coupling to the desk, too. This is something I need to try. Without the ADS1 stands, the A2s aren’t quite as good as the Rockus for desktop music listening.

LISTENING IMPRESSIONS: HOME THEATER

The Rockus speaker system was hooked up to the TV/HTPC in two different ways, over a period of three weeks. First from the analog output of a Samsung PN58C6400 58 inch Plasma TV, then from the analog output of the high quality onboard sound of a HTPC. This is in a lightly furnished, 12′ x 12′ den. The sound quality of the TV’s audio circuits and speakers is very good, but sometimes lacks clarity for dialog to be easily understood without turning the volume up.

As mentioned earlier, the speaker cables were too short to be placed on either side of the TV with the center woofer on one side. The center unit had to be left in the center in front of the TV stand, rather in the way. If the system was going to be installed permanently, at least one speaker cable would have to be replaced with a longer one.

Each speaker was set next to the TV, again, angled inward so that their central axes intersect in front of the easy chairs 2m directly opposite the TV at the same plane as the screen, about a meter apart, and a foot from the back wall.

The sound of the Rockus was much clearer than that of the TV, all around. Dynamic impact, bass weight, drama imparted by the musical score in movies — all of these aspects were improved. Dialog was easier to follow than with the TV speakers even at lower volumes. These observations held true whether the source was the TV or the HTPC. The system could play loud enough to overwhelm the room and listeners’ eardrums before clipping distortion set in.

The 3D mode enhanced sound effects in high action programming, and sometimes boosted the midband so that dialog was more prominent. In general, my preference was for the music mode, which seemed more natural and more compatible with a broader range of program material.

Again, the AudioEngine A2s were brought up to compare/contrast with the Rockus. The differences were interesting. The Rockus often sounded a bit more raucous, but they generally improved clarity, while the A2s did not always do the latter. Bass impact was better with the Rockus on dramatic material, and dialog was usually easier to follow. AudioEngine A2s were usually smoother sounding, and sometimes better with music in the program. Not exactly a total win, but the nod here goes to the Rockus.

AGAINST GOLIATH

It was a middling high end audio system 15 years ago… It’s probably nowhere near high end today, but it still sounds very good. The source is mostly uncompressed digital audio files from the network fed via a SqueezeBox, then converted to analog by a MSB Technology LINK DAC-III 24/192 outboard D/A converter. Amplification is a Linn Kairn preamp and Linn AV5105 power amp. The speakers are NHT 2.9, a 4-way stereo pair one step down from the brand’s then-top 3.3 model — now long discontinued like all the other equipment I’ve described. Here is how my reference system sounds:

The overall sound is affected far more by the recordings and the music than any signature the system imparts. Most listeners describe the sound as very lively, clear, dynamic, detailed; smooth and soft when the music is smooth and soft, and raucous and loud when the music is raucous and loud. A notable quality for me is that when a good recording of a smallish band (say under 5~6 instruments plus a vocalist) is played fairly loudly, sitting in the kitchen through the open doorway at the far end of the house, it is not hard to imagine that the performers are actually there playing, albeit more softly than in a lounge bar. Bass extension is excellent. It also sounds very good at low volume, detailed and clear. In terms of weaknesses, on some recordings, there can be a lack of "bloom" in the midband and the overall "sense of air or space" a bit constricted. Bass can also get a bit "fat" sounding with some recordings, though many listeners like this quality.


Rockus satellites laid on their sides so as not to be shooting up toward the ceiling.

The room is quite large and lively, 30′ x 13′ x 8′; it’s a living room that continues into the dining area. The NHT 2.9 speakers are about 1.5′ in front of a wall that is mostly sliding glass doors to the front deck.

The Soundscience Rockus 3D | 2.1 satellites were perched atop the NHT 2.9 speakers, with the center woofer between them. The system was connected directly via phono cables to the outputs of the MSB Technology D/A outboard converter. Only the SqueezeBox was used for sound sources. As the photo below suggests, it is an absurd David-Goliath comparison, and the Rockus speakers are not intended for use in such a big room.

The sound of the Rockus speakers in this setup was pretty good, clear but a bit thin. The system could be heard straining as volume reached upwards of 85 dB from 3 meters away in this large room. Up to moderately loud volume (say up to ~80 dB peaks at 3 meters), with a wide range of music, the Rockus sounded better than expected, but not quite as convincing as the Audioengine A2s which were compared in the same way before. The window to the music was too small for anyone to be fooled into thinking the NHTs were playing.

Against the big NHTs in this big room, in the "traditional stereo" role, the Rockus speaker system fell short of the AudioEngine A2s, whose smoothness and richer mids made it a bit more convincing. This, despite less bass in the A2s. Remember, neither the A2s or Rockus speakers are meant for this role, and I would not accept either of them in this setup for long.

TESTS IN THE ANECHOIC CHAMBER

So far, this review has not been that different from other subjective reviews in tech hardware review sites. Impressions, descriptions of perceived sounds, subjective assessments of the listening experience. Is that enough for a review of a $250 speaker system for the PC or TV?

Consider — There are probably more 3-piece stereo satellites plus woofer speaker combinations on the markets than anyone really knows. Such 3-piece speaker sets have been around for home audio for at least three decades, long before they became popular for computers. Now, with PC-oriented systems also in the picture, the numbers have to be astronomical, especially if you also include simple stereo speakers that don’t use a discrete center bass driver. Every audio component brand and just about every computer component brand has some kind of speaker on offer.

So how can anyone make a valid, useful assessment of one of these systems in reasonable context? This is always a challenge with audio gear — especially speaker systems — because even basic parameters such as frequency response cannot be tested without sophisticated, expensive equipment and a good quiet room whose acoustics characteristics can be removed from the equation. This is a major challenge for any audio equipment review, and only a tiny handful of long-established high-end audiophile publications have the right test gear to validate manufacturers’ specifications. Even when such measurements can be made, the results are hard to put in perspective without running the same tests on half a dozen other similarly priced and/or configured speakers. No one does such tests in reviews of $250 speaker systems.

Fortunately, SPCR is a couple of major steps ahead of almost all other PC hardware review sites in acoustics metrology. We have…

  1. our own home-built, hemi-anechoic chamber, an environment that is extremely quiet and almostly completely without reverberation above ~150 Hz.
  2. a lab-reference calibrated, ultra-low noise microphone with ruler-straight frequency response that cost over $2,000
  3. a sophisticated PC-based sound measurement system whose capabilities have barely been scratched in the 2+ years since initial use

SPCR’s audio measurement system can be employed to provide basic loudspeaker measurements such as on/off axis frequency response, maximum SPL, and total harmonic distortion. The audio measurement / spectrum analyzer system consists of…

For testing loudspeakers, a signal generator is needed to drive the speakers. As the speakers have built-in amplifiers, this was provided with software via the integrated sound card of a second PC, a silent PC with no moving parts, inside the anechoic chamber.

NOTES on MEASUREMENTS and TEST CONDITIONS

1. SPL: The sound pressure level at which measurements are done is extremely important. A common procedure is to provide the sensitivity with 1W input, and also test the frequency response at the same power input. For a typical passive speaker (one that does not have a dedicated amplifier built into it), this might be something like 90 dB/W, which means when driven with 1W input at, say, 1 kHz or with white noise, the speaker output measures 90 dB SPL one meter away. In fact, 90 dB@1m is a fairly common level for frequency response measurements.

Two considerations:

  • What is the right SPL as a baseline for PC speakers? The Rockus speakers are meant for use in a small room, or under nearfield conditions with a single listener a meter away. It has a stated maximum SPL of 95 dB, so anything close to 90 dB seems too high a level. 90 dB is much louder than you might think: Typical SPL scales suggest that 90 dB is about what you hear from a diesel truck 10m away, inside a moving subway train, or from a food processor directly in front of you.
  • What is a realistic volume for actual use? A check of SPL levels was done at the desktop playing a variety of music at various volumes. This was repeated in front of the TV (with the seated position 5~6′ from the speakers), during movies, TV shows and other program material. The results are summarized below.
Measured SPL @ 1m, Typical Use w/ Rockus 3D | 2.1 speakers
At PC/desktop Pop music, background 70~75 dB
Pop music, "loud" 80~90 dB
Other music, background 65~75 dB
Other music, "loud" 75~90 dB
Various online videos 75~85 dB
With TV Drama 70~85 dB
Action 75~90 dB
Documentary 75~85 dB
*Other Music: Jazz, Classical, Folk, etc.

It was extremely rare for the volume level to exceed 90 dB@1m in any application. Even 85 dB@1m was fairly uncommon, reached only during brief peaks. This could be simply a reflection of my listening habits, but spot checks with other family members, friends and visitors more or less confirmed that this is fairly typical: Few people actually listen to music at their desktop or watch videos on their TV with higher volume than indicated above. There are always exceptions; remember, we’re just trying to establish a reasonable baseline here.

So it was decided that for small, PC-driven speakers, 85 dB@1m would be the white noise SPL at which frequency response is measured. There are many good reasons for choosing this reference level:

  • It’s on the loud side of typical music listening done with PC speakers.
  • It is probably not too loud for any speaker to achieve without overload.
  • It’s not too loud for me to bear for long testing periods.
  • It’s at least 40 dB above the noise floor in the chamber at any time, yet not too intrusive outside when the chamber door is closed. This means testing can done pretty much any time.

2. Frequency Response: As mentioned earlier, this is the single most widely cited specification in audio, especially with mechanical devices like loudspeakers, which traditionally have the greatest deviations from flat frequency response. It is best shown in a frequency vs sound pressure level graph. In the simplest terms, frequency response tells the ability of an audio device to reproduce sounds of different frequencies at the correct relative levels (loudness). A perfect device has a frequency response that looks like a ruler straight line; hence the term "flat" (not flat as in B-minor flat.) Alas, there are many complex issues around this much-cited parameter.

  • It is highly dependent on the acoustics of the room, the position of the speaker(s) in the room, and the position of the microphone. If this test is performed in a live room, then sophisticated calculations must be used to remove the effect of room reflections (echoes). Otherwise, it must be performed in an anechoic chamber.
  • Frequency response of a loudspeaker generally does not stay constant with loudness level. Typically, there is a range of SPL in which a speaker is most frequency-linear; go outside this range, especially above it, and the speaker will exhibit frequency non-linearities that lower fidelity.
  • Frequency response also changes with the angle of perception, both vertically and horizontally. How smoothly the frequency response changes as one moves off axis is a key to better sound loudspeakers.

Given the complexities, dozens of frequency response graphs could be plotted and posted… but their usefulness would be questionable for most readers. So… this is the procedure established for frequency response testing:

  • Place the speaker at the front edge of the 28.5" (72cm) tall table in anechoic chamber.
  • Place the microphone 1m directly in front, at the same height.
  • Set the output level to 85 dB@1m SPL using white noise.
  • Capture the frequency response graph at 1m distance, on axis, and at 30 degrees laterally off axis
  • If there are any bass or treble controls (such as bass level), engage them to show the response variations
  • Treat one satellite + center woofer as a single speaker, with bass unit directly under the satellite.

NOTE: Only a single speaker (or single speaker + center woofer) is tested, as there are many complications that arise when trying to measure a stereo pair together at the same time.

3. Harmonic Distortion: This is a relatively easy parameter to measure. A pure sine wave tone is fed into the speaker, and the spectrum analyzer sums up all the aspects of the signal that are not this pure tone, expressed in a percentage of the total signal. Harmonic distortion is not particularly important, however, as it occurs naturally in music and is thus difficult to perceive. Even 10% THD at 50 Hz is probably not audible to most people if it occurs in the context of music — and I am not talking here only about a heavy fuzz bass guitar. Amplifiers and other electronics are capable of miniscule levels of harmonic distortion (say 0.01%), but it is much higher in mechanical devices like speakers, especially when large cone excursions are involved (necessary for high volume at low frequencies). Again, the SPL at which HD is measured has a serious impact on the result, as does the frequency. Simply put, the louder and lower the test tone, the harder a speaker has to work to reproduce it. Longer cone excursions almost always result in greater signal anomalies.

After much experimentation, this is the procedure established to test for harmonic distortion:

  • Place the speaker at the front edge of the 28.5" (72cm) tall table in anechoic chamber.
  • Place the microphone 1m directly in front, at the same height.
  • Set the output level to 85 dB@1m SPL using white noise.
  • Leave the gain unchanged while running test tones at the following frequencies: 10kHz, 5kHz, 2.5kHz, 1kHz, 500Hz, 250Hz, 100Hz — and lower, to the lowest frequencies where distortion does not exceed 20%.
  • Tests were kept as short as possible: It is easy to damage speaker drivers with steady state pure tones, even at low power levels!

OTHER TESTS?

There is no shortage of tests that can be run on speaker systems. These include impulse testing, intermodulation distortion, resonance/decay testing of the enclosures, phase response, etc. With time and effort, all of these tests can probably be brought to bear on SPCR speaker reviews. The real question is, for what benefit? For the class of product the Soundscience Rockus (or AudioEngine A2, from the one other speaker review) represents, there is little benefit. Once the basics of frequency response, dynamic volume capability and distortion are covered, in-use details and good subjective descriptions should be more than adequate for a buying decision. This class of speakers will never be used by anyone to seriously replicate a live music listening experience.

Finally, keep in mind that speaker measurements are not infallible, nor do they tell the whole story. Like careful listening with the right ancillary equipment, acoustic measurements are tools by which the performance of a speaker system can be more fully understood.

ANECHOIC CHAMBER AUDIO ANALYSIS

1. Frequency Response – We begin with a frequency response graph showing one satellite + center woofer combined, on axis with the satellite, and off axis by 30 degrees. This is with the bass level set to 3, for the highest bass output. As mentioned earlier, it is not useful to test the frequency response of both left and right speakers together, due to measurement complexities.

Click for large view
Frequency response graph of the Rockus 3D | 2.1 – click for larger view.

Looking first at the on-axis response: From about 100 Hz to 4 kHz, which spans over five octaves, more than the entire range of human voices, the overall response is pretty good, excepting three dips. The first, centered around 300 Hz, is most likely some kind of interaction / cancellation effect related to the woofer and satellite combination, and/or reflections from the mostly undamped floor of the hemi-anechoic chamber. The second dip, at 500~600Hz, is more difficult to explain. Finally, there is another sharp dip around 1 kHz. None of these dips correlate well to what I heard in the listening sessions, except perhaps the ~300Hz dip, which might correlate to a slight thinness sometimes heard in things like male vocals.

It is the higher frequency peaks that are more problematic: In the octave 4~8 kHz, there is a broad peak of 5~7 dB, followed by a sharp dip around 10 kHz, then another even sharper peak at 11~16 kHz. Those peaks are responsible for the over-brightness heard with some program material, especially music that has high content in those last couple of octaves. The off-axis curve shows why the Rockus generally sounds better off axis: The entire range above ~3 kHz is reduced in level so that it is closer in level to the midband, say 500~1000 Hz. The greatest change off-axis is at 10~15 kHz; with music that has a lot of constant high frequency content, moving one’s head could cause audible shifts in the sound balance.

Contrast/compare the above with the frequency response of the AudioEngine A2. Yes, since they were here, and these labs tests were never done for the A2s (as the anechoic chamber was not put into service till several months after that review), they got whisked in for their time in the lab.

Click for large view
Frequency response graph of the Rockus 3D | 2.1 – click for larger view.

The overall curve is smoother, and except for narrow dips that are probably inaudible in actual use, above ~400 Hz, the only significant departure from flat response is a broad dip at 3~6 kHz. This might be what makes the speaker sound smooth, yet a bit lacking in sparkle sometimes. The top end is very well behaved on or off axis, extending out to past 15 kHz before sloping off. Then there is the artificial rise in the low end which starts around 300 Hz and peaks some 5 dB higher at 180~200 Hz. This is responsible for that over-rich mid-high bass. As you can see, output drops off pretty steeply below that… looks like around 12 dB/octave. There is little useful output below 100 Hz, so the surprising bass it does manage to convey is very much a clever illusion.

2. Effect of Bass Level Switch – This is straightforward: On-axis graphs showing the response with the bass level switch in each of the three positions. You are advised to start with level 2 and set the position up or down in accordance with your tastes, room acoustics, etc. Once set, it is usually best to leave it alone.



Rockus 3D | 2.1: Effect of Bass level switch – click for larger view.

3. Nearfield Frequency Response Measurements – This technique places the microphone within an inch or so of each driver. The other drivers are turned off if possible or muted by putting them farther away and muffling them physically. It shows us the sound emanating from each driver.

A somewhat different picture of the satellite’s frequency response emerges, with a broad dip between 2 kHz and 4 kHz. This may also be responsible for some of that thinness in the sound on some music. That top octave peak remains unchanged.

The crossover in the Rockus cuts the signal to the satellite below 250Hz at a very steep slope, most likely 24 dB/octave. The high filter for the bass driver is about as steep, dropping some 20~24 dB between 110 Hz and 220 Hz. Although the crossover details are not detailed, a spec of 24 dB/oct @180 Hz would be fair. This is a very safe crossover for this type of system, as it ensure the little satellites will never be exposed to high power bass signals. The signal is already 30 dB down at just 180 Hz. It is possible the bass signal is cut off at too low a frequency; this may explain the dip around 300 Hz seen in the other frequency response curves.

The nearfield measurements also explain clearly why the Rockus satellites did not have the problem of vibrating the entire desktop; the higher excursion bass notes simply don’t come from the satellites, so they don’t excite the resonances in the desktop.

The tweeter and woofer in the A2 speakers are so close together that I could devise no practical way to measure each driver output separately.

4. Harmonic Distortion

As with all the other tests, the output level was set to 85 dB@1m with white noise. Sine wave tones were then run, for harmonic and intermodulation distortion to be measured with our SpectraPLUS audio analyzer. This test was doen with both the Rockus and AudioEngine A2 speakers.

Measured Distortion, Rockus 3D | 2.1 speakers
Test Tone
Rockus 3D | 2.1
AudioEngine A2
SPL (dB)
THD
SPL (dB)
THD
10 kHz
78
0.38%
78
0.15%
5 kHz
84
0.64%
84
0.36%
2.5 kHz
77
0.21%
77
0.28%
1 kHz
78
0.68%
78
0.39%
500 Hz
81
1.20%
81
0.60%
250 Hz
70
4.80%
78
0.76%
100 Hz
85
4.90%
79
5.90%
80 Hz
88
16.40%
72
8.10%
70 Hz
72
13.20%
69
12.40%

The harmonic distortion figures look pretty much as expected: They are low at the higher frequencies and increase steadily as frequency drops. In the Rockus, that the distortion is higher at 80 Hz than 70 Hz suggests the passive radiator has a bigger role at the lower frequency. Distortion at 80 Hz is lower in the A2, but note that the Rockus is a whopping 16 dB higher in level. At higher frequencies, the superiority of the A2’s tweeter asserts itself. The satellite driver in the Rockus has to do a lot more, extending all the way up beyond 10 kHz.

POWER MEASUREMENTS

This is SPCR; it is a long established tradition to measure and report power consumption whenever possible. They are difficult to do while the speaker/amps are actually working to produce sound, but much easier in static mode.

Audioengine A2
AC Power & SPL Measurements
State
Rockus 3D | 2.1
Audioengine A2
AC Power
SPL (dB)
AC Power
SPL (dB)
Off, plugged into AC.
4W
0
1W
0
On, volume control at MUTE
7W
0
4W
0
Playing music at desktop, modest volume
7~12W
60~70 dB@1m
4~6W
60~70 dB@1m

TV programming sound, moderately loud

12~24W
60~85 dB@2m
4~20W
60~85 dB@2m

Playing music in large room, just below overload

20~44W
60~85 dB@3m
15~30W
60~85 dB@3m

The differences are not large, but the smaller AudioEngine A2 has an edge. It should; the Rockus has more powerful amplfiers, and there are three of them, compared to the A2’s two.

FINAL THOUGHTS

This review of the Soundscience Rockus 3D | 2.1 speaker system has been an interesting project on several levels. It is the first time that the acoustic analysis capability of the SPCR anechoic chamber has been used for speaker testing. Happily, the test results have been helpful, shedding light on subjective impressions and putting the review on a more empirical footing. It was also a good excuse to revisit the AudioEngine A2 speakers, which were reviewed just before the chamber came into service.

At least one test result provided a better understanding of why desktop speakers generally sound as poorly as they do, and how they can be made to perform better. The desktop is much like a large sounding board. Placing any speakers capable of significant bass on such a sounding board couples them mechanically, which ensures all kinds of deleterious sonic effects. The simple expedient of keeping low frequencies out of the desktop satellites makes the Rockus substantially more listenable at higher volumes than the AudioEngine A2s, despite the latter’s smoother overall performance. It may well be that the new silicone rubber stands made for the A2s can limit the bass coupling to the desktop significantly; this is something I will try to find out soon.

A few more compressed MP3s were used to check Antec’s position that such source files need a bit of boost in the treble to sound better, but this test was not conclusive, as some highly compressed MP3 music files just didn’t sound great no matter what was done to doctor them up. Our position is simple: Why bother with such compromised files in this day of proliferating cheap digital storage? I am of the opinion that Antec could make a substantial improvement by taming the too-hot top end in the satellites. Hopefully, Soundscience will take a product development approach which emphasizes refining and improving existing products rather than starting scratch every year. Especially in audio electro-mechanical design, there is much to be gained from such an approach.

It is clear that Antec’s first entry into PC audio is a strong contender, though not without some weaknesses. (It is hard to imagine how any $250 powered speaker system could actually have no flaws.) The overall performance of the Soundscience Rockus 3D | 2.1 with music at the desktop is clear and detailed, with good bass weight and extension, lively dynamics, and the ability to play quite loudly without overload. The brightness that shows up with some program material is easy enough to tame with equalizer controls on many software music players. In the role of a TV or HTPC speaker system, it also fared well, providing improved clarity of dialog and dramatic sound effects over typical TV speaker systems, but without the complexity and bother of the too many speakers and wires everywhere (needed for 4- or more channel home theater sound). Whether the Rockus is a better performer than other PC speakers in the same price range is not possible for us answer without more extensive investigation, but the review findings suggest that it merits your serious consideration. For now, the review Rockus sample will remain on my desktop.

Our thanks to Antec / Soundscience for the Rockus product sample.

POSTSCRIPT – For audio/modding diehards, the article continues on the next page with a detailed look Inside the Rockus satellite.

* * *

Articles of Related Interest
AudioEngine A2: Little Big Speakers
Squeezebox 3 Digital Music Box
Scythe’s Kama Bay Amp

Xonar HDAV1.3 Deluxe: Asus HTPC sound card does Everything

* * *

Discuss
this article in the SPCR forums.

POSTSCRIPT: INSIDE THE ROCKUS SATELLITE

As soon as I discovered that this satellite driver is a single paper 2.75" cone, I became interested in a very personal way. I’ve been fascinated by music and sound all my life, and messed around with audio gear since preteen years when Father brought home a then-high end Sony 7" reel-to-reel stereo tape recorder from a business trip to Hong Kong and passed it on to me the next day… realizing he didn’t have the dexterity to thread the damn tape. That got me started. I’ve collected umpteen pieces of gear, thousands of albums, worked in a handful of audio stores, including some very high end ones. Finally, designing, buidling and fine-tuning speakers has been a hobby for the better part of three decades.

In the vast majority of speaker systems, a midrange driver is not asked to extend up to the last octave of audibility, and for good reason. A drive that can handle the all important midband where the bulk of musical fundamentals lies is usually too big to have good dispersion, with too much mass for smooth extension. That is why tweeters were developed in the first place: Small diameter for better dispersion of the short frequencies up there, very low mass for quickness and linearity. However, there has always been a faction in the audio community pursuing the holy grail of a single full range driver that does the entire audible range without crossovers. Some of these devices, just the raw drivers, cost upwards of $1000 each. Fostex, Seas, Lowther, Jordan — these are some of the names that command awe among full range speaker enthusiasts. Am I one? Well, no, I have not been convinced, but then perhaps I just haven’t heard the right driver in the right design, yet.

In any case, the driver in the Rockus satellite had to be examined. A close look at the satellite showed only four hex-head bolts or screws on the back side. Time to dig through the Allen wrenches. It did not take long to remove them. There is a gasket with glue used as a seal around the rim.


Rockus satellite back panel + stand removed.

A close look into the cylinder showed thin foam damping glued to the aluminum wall, the back of the driver magnet, and four philips head screws. Careful not to let the magnet pull the long screw driver where it might damage something, I removed those screws. They turned out to hold down the flared rim in front, along with the hex-pattern cover over the front of the driver cone.


Driver cone revealed: An ordinary surround, paper cone.

Removal of the screws holding down the speaker driver had to be done with a lot of care to ensure the screw driver did not puncture the cone. When it was done, the driver could be examined in its entirety. Leads from the input terminal are soldered, not just clipped, to the driver terminals.


It’s a pretty big magnet for the size of speaker. The suspension feels nice and supple, but it’s difficult to see any mechanical reason for the top octave peak. I am almost positive that the boost is accomplished electronically within the electronic crossover/amp section of the system.

A close examination of the baffle/cover made me shake my head. Surely something with less impedance could have been used. This is in stark contrast to the AudioEngine A2, which dispenses with any grills over the drivers, and uses rounded, smooth contours around the edges of the openings for the driver to keep diffraction to a minimum.


This is the cover for the cone. It protects the cone, for sure, but cannot help the sound, which is guaranteed to be diffracted right at the source.

For the past week, I’ve been using the Rockus satellites at my desk with the grills removed. Do they sound better? I think so… smoother, cleaner, with less "venetian blind" effect when I move my head. You can see this in the on/off axis frequency response curves below.


Compared to the response with the grill on below, the lines for both on and off axis without the grill are smoother. They are also more similar to each other, 1~10 kHz.

Click for large view
Frequency response graph of the Rockus 3D | 2.1 – click for larger view.

So there you have it. My warranty-busting "upgrade". Should you wish to try it, I take NO responsibility for the results of your actions.

* * *

Discuss
this article in the SPCR forums.

Leave a Comment

Your email address will not be published. Required fields are marked *