Hsu Research CCB-8 Bookshelf Speaker Review

HSU CCB-8 Introduction

The Hsu Research CCB-8 is not your typical bookshelf speaker, and it only takes one glance at it to make that determination. Those folks who are not acquainted with the diversity of driver layouts (you know, ‘normal’ people, as opposed to us speaker nerds) might be wondering where the tweeter is on the CCB-8, since only the woofer is visible on the exterior. The CCB-8 uses a coaxial driver layout, meaning that the tweeter is centered in the middle of the woofer itself. This design decision carries with it a host of advantages that we will discuss when we get to the design overview section. When I asked the CCB-8’s designer, Dr. Poh Ser Hsu, what prompted the design and production of the CCB-8, he told me that me had always been impressed by the holographic imaging of point-source design such as coaxial speakers. He also said he wanted to address the problem of lobing that occurs with horizontally-oriented drivers that is very common on center channel speakers, and that a coaxial design is a perfect way to solve that issue. So now that we have a set of CCB-8s in house, this brings us to the question: how well do they achieve the objectives Dr. Hsu set out to accomplish?

Unpacking and Appearance

The CCB-8’s come packed in a heavy-duty cardboard box and sandwiched between two thick foam pieces. They are wrapped in a plastic bag on the outside and a cotton bag on the inside, to protect them from both moisture and scuffs and scratches. The owner’s guide is fairly standard, but it does include some good advice about placement. Due to the unique design of those speaker, some attention should be given to placement and positioning section of the manual, since their advised positioning differs somewhat from traditional bookshelf speakers.  

The appearance of the CCB-8 speakers is a bit unusual from ordinary bookshelf speakers. A yellow cone with a black dustcap set against a fine satin-black cabinet begs a visual comparison with some kind of mechanical eye. The black metal grille does temper that likeness a bit by dimming the yellow. The grille is attached magnetically, so no grille guides clutter the front baffle. The CCB-8 is on the large side of bookshelf speakers, with a 15” height, a 10.5” width, and a 12” depth. Anyone intending to use these with bookshelf speaker mounts will need a heavy-duty mount, not just for their size but also their 22 lbs. weight. The satin-black finish is sleek, and, with the addition of the rounded edges, do lend the CCB-8s a sense of style beyond mere utilitarian. However, this speaker, without its grille, is not a conservatively styled speaker. It has personality, and it will clash in a home with traditional decor. That can be alleviated somewhat with the optional rosenut finish which does take the edge off the yellow cone and makes the CCB-8 look more refined. The bottom line is that it is a speaker with a peculiar style that is bound to turn some people off. Personally, I like it, however I like it when speakers have character. I prefer it when speakers look like speakers and do not pretend to be an innocuous piece of furniture.

Design Overview

Clearly, the chief distinction of the CCB-8 is the use of the coaxial driver. As mentioned before, the coaxial driver arrangement places the tweeter in the center of the woofer. In the CCB-8’s case, the tweeter is sunk back behind the motor of the 8” woofer. The tweeter is a 1” aluminum dome that uses the pole piece and polypropylene cone of the woofer as a waveguide. This design is seen mostly in live sound applications and professional, high-powered sound installations but is seldom used in home audio, although notable exceptions are the higher-end speakers from Tannoy. Since the tweeter is embedded deep behind the woofer, the ‘horn’ of the pole piece and woofer should contract the dispersion of the tweeter for a tightly-controlled spread of sound; this is called a constant directivity dispersion pattern.

One of the advantages of coaxial designs is that the acoustic center of the woofer and tweeter remain the same irrespective of where you are in relation to the speaker – above, below, left, right, or center of the driver. That means once the drivers are time aligned on axis, they are time aligned at any off-axis angle. With a typical speaker where the tweeter is above the woofer, that is not true. When the speaker is time aligned on tweeter axis, standing above the speaker will place you closer to the tweeter, so the woofer and tweeter are no longer time aligned as the sound from the tweeter will arrive first. This affects the phase matching between the drivers and causes peaks and dips in the response. And, of course, the same is true if you are below the speaker, but in reverse; since you are closer to the woofer, the sound from the woofer will arrive first and is no longer time aligned.

Since there is very little distance between the woofer and tweeter in a coaxial driver, time-alignment is a problem that is easily solved, especially since the distance difference only occurs as a very small matter of depth, rather than a significant height or width difference as is the case with most speakers. This is one of the reasons they are called coaxial drivers, since the term ‘coaxial’ means ‘having a common axis.’ They are also sometimes called ‘coincidental’ driver, since their time alignment is so close (‘coincidental’ defined as ‘occurring at the same time’), and ‘concentric’ drivers (concentric: sharing the same center).

Most speakers are point-source designs, meaning that the sound is intended to act as if it is emitting from a single point. That point is called the ‘acoustic center’ and usually is at some imaginary point near the tweeter in normal multi-way speakers that have drivers spread out over the front baffle. There are tricks that speaker designers can use to align the drivers to conform their operation to that acoustic center, but many of these measures aren’t needed with coaxial drivers, since the acoustic center of the overall speaker is so close to the acoustic centers of the individual woofer and tweeter.

Given these advantages, one would expect coaxial speakers to be more prevalent, but, as with all design decisions regarding speakers, there are trade-offs. One drawback is the cost-complexity of manufacturing coaxial drivers. Indeed, Dr. Hsu tells me that the coaxial driver used in the CCB-8 costs six times as much as the tweeter and woofer used in Hsu’s HB-1 mk2 bookshelf speaker.

A part of the challenge of producing a coaxial driver is matching the directivity of the pole piece/cone horn for the tweeter to that of the woofer itself. In other words, the lower frequencies produced by the woofer itself has to ‘spray’ sound outward at the same angle as the higher frequencies being directed by the waveguide formed by the pole piece and cone of the woofer. Towards this end, Hsu Research contracted the legendary speaker scientist Don Keele, Jr. Among many of Keele’s achievements is being one of the developers of constant directivity horns in the mid 70’s, which provided a basis for many future horn designs. Hsu Research would have been hard-pressed to find a more qualified engineer for this task.

Looking under the hood of the CCB-8, we see a relatively elaborate crossover board for a two-way bookshelf speaker. Dacron or Polyfill line the interior panels. The cabinet panels are a beefy 1” thick MDF, but there is no cross-bracing to speak of. Perhaps Hsu thought that with such thick sidewalls, more internal bracing was not needed. The CCB-8 is vented and has two ports on the rear panel. Port plugs are provided, and these ports can be sealed to change the tuning point of the speaker if the user wishes. In our measurements and analysis section, we do show the effects on frequency response of sealing the ports. In the rear, we also see a terminal cup containing a pair of stout 5-way, gold-plated binding posts. There are no feet affixed to the CCB-8, since it is intended to be placed on any of its sides.

The woofer itself sports a cast aluminum basket and a good-sized magnet. The inverted surround is made from treated cloth, and the spider looks to have a healthy diameter for the size of the driver. The 2” diameter, edge-wound voice coil is large for a 8” midwoofer, but it needs to be since the throat of the horn for the tweeter may be too constricted otherwise. The tweeter itself has an aluminum heatsink mounted on the back. That, combined with the ferrofluid cooling, should do a lot to keep thermal compression at bay. These extra cooling measures might be required by the coaxial design, since the driver motors are so close to each other. The acoustic load of the horn allows for an unusually low crossover point of 1.5 kHz for an aluminum dome tweeter. The CCB-8 woofer and tweeter can be protected by the grille, which is a sturdy steel perforated metal screen. It really does protect the drivers from anything hitting them. As mentioned before, the grille attaches magnetically, but it does not come off easily. 

It should be noted here that in theory the design of the CCB-8 should allow it to work nearly as well on its side as it does standing upright, since there should be no off-axis lobing patterns. In fact, the CCB-8 should have superior off-axis dispersion to traditional center speaker designs, which usually suffer from interference patterns where the horizontally aligned drivers cause cancellations in the frequency response. Audioholics has a host of articles discussing the trade-offs of traditional center-speaker designs such as: Vertical vs Horizontal Center Speaker Designs, Center Speaker Design Additional Considerations, and Vertical vs Horizontal Center Speaker Designs - An Alternate Perspective. Hsu Research sells the CCB-8 as a singly-packed center speaker as well as main speakers for these reasons.

Another advantage of the coaxial design is that since the sound of the tweeter and woofer come integrated ‘right out of the gate,’ so to speak, they should be able to be used as near-field speakers, if one so desired. Most other speakers need some distance before the sound of their individual drivers ‘coalesce’, or properly sum in phase, so you can’t simply use any bookshelf speaker for near-field listening, at least if you don’t want to hear the drivers fighting around the crossover frequency. Due to their near-field phase coherence, a design like the CCB-8s can be used as desktop speaker, if one had desktop space for such large bookshelf speakers. However, as with all speakers used on a desktop, the user should try to elevate the speakers as far off the desktop itself as possible while keeping the tweeter at ear level. Desktop reflections, or any nearby surfaces can cause unpleasant spikes in mid bass and upper bass frequencies. If the user can not prop a desktop speaker up off the desktop surface with something like a desktop speaker stand then they should be ready to measure the frequency response and equalize down any severe reflection peaks.

Placement Considerations

One peculiar feature of the CCB-8 is the recommendation by Hsu to toe the speakers in front of the listener where the listener ends up 15 degrees off the direct axis. In fact, the CCB-8 is engineered from the ground up to be listened to off axis around a 15-degree angle. The reason for this is because Hsu is leveraging a phenomena known as ‘time-intensity trading’ to create a strong stereo image across a wider listening area, so that listeners do not have to sit in a single position to experience good imaging. Time-intensity trading is, in very simple terms, when our perception of hearing can be fooled into thinking something sounds closer to us than it actually is, because it is louder.

The two primary ways that we determine the location of a sound is the differences in the time arrival of the sound between both our ears and differences in amplitude of sound (that we perceive as loudness) between our ears. If we hear something sooner in one ear than the other, the origin of the sound will be perceived to be in the direction of the ear which first sensed the sound. If we hear something louder in one ear than the other, the origin of the sound will be perceived to be somewhere in the direction of the ear that sensed the sound to be the loudest. That, of course, is a very simple explanation of these seemingly common-sense aspects of our hearing, which are called Interaural Time Difference (ITD) and Interaural Intensity Difference (IID), respectively.

In normal stereo speaker systems, the closer you are to one speaker, the more the stereo image shifts in its direction, so the imaging will very often be heavily weighted toward the speaker that you are closest to, and this is due to ITD and IID. It is because of this that the listening position of a stereo system is always right between the speakers, usually forming an equilateral triangle with the speakers themselves, and with the speakers toed-in to face the listener directly. But what if you could alter that effect by compensating the time arrival difference between right and left ears with the amplitude difference between right and left ears? This is the logic of the 15-degree inner toe-in of the CCB-8s. If you are sitting off center in a system that is built for such an arrangement, the speaker facing you will be louder, but that isn’t the speaker that is closest to you and so will have a later time arrival. By balancing time arrival with loudness, we can preserve a sharp stereo image, even when we are sitting off the “sweet spot.’ The is the effect achieved with time-intensity trading, and it is something that a constant directivity design like the CCB-8 should excel at; in fact, a wide-dispersion speaker would not work well for this kind of setup. For a more comprehensive guide on time-intensity trading in speaker placement, read Bill Waslo’s article: Setup of Controlled-Directivity Waveguide Speakers.  

Hsu Research CCB-8 Bookshelf Speaker Listening Tests

In my approximately 24’ by 13’ listening room, I set up the speakers with the approximate stand-off distances between the backwall and sidewall suggested by the owner’s manual. This left a roughly equal distance between speakers and listening position, with tweeter at ear level and the speakers toed-in in front of the listening position for a roughly 15 degree angle facing the listener. A Pioneer SC-55 receiver was used in ‘Direct’ mode, so no tonal processing would interfere with the speakers’ natural sound. Subwoofers were used when listening to these speakers with crossover frequency set at 80 Hz. These speakers are intended to be used with subwoofers. Speaker distance from listening position was about 10 feet.

Music Listening

I always try to start listening to a review speaker by using a cleanly recorded vocal track, because that is typically where problems can most easily be noticed on a speaker, since human hearing is so heavily ‘tuned’ for the sound of a human voice. For this review, I procured a copy of Rebecca Pidgeon’s ‘The Raven,’ a classic album that is now a part of the set list of any audiophile demonstrating the verisimilitude of their system. ‘The Raven’ is folk music with some jazz sensibilities that is mostly a showcase for Rebecca’s clear and smooth soprano delivery. As with all albums produced by the Chesky label, this album is impeccably produced and has a superb level of sound quality. 

Of course, the fidelity of an album cannot sound better than the system that it is being reproduced on, and I am happy to report that ‘The Raven’ sounded terrific on the Hsu CCB-8 speakers. Rebecca’s voice was rendered with exceptional clarity. What struck me right away was the outstanding imaging. The positioning of the vocalist and the instrumentalists had no ambiguity. The soundstage was broad but still extremely well defined. The illusion of a full band from just two points of sound always impresses me, but I have to say the CCB-8s do take that ‘aural holography’ to a level I have not previously heard in my own system. Other aspects of the sound produced by the CCB-8s were fine and left me with nothing to complain about, but their imaging was so uncanny that it what held my focus for the duration of the album. After listening to ‘The Raven’ on the CCB-8s, I am left eager to hear the other albums I have queued up for these speakers.

For something on a less intimate and far grander scale, I turned to ‘Mythodea,’ an epic choral symphony recorded in 2001 that has an enormous scale. The music was composed by Vangelis and performed by the London Metropolitan Orchestra, the Greek National Opera, two Greek percussion ensembles, additional performers such as vocalists Kathleen Battle and Jessye Norman, and, of course, Vangelis himself on keyboards. Altogether, well over 200 performers were used for ‘Mythodea.’ ‘Mythodea’ was used to celebrate the 2001 Mars Odyssey’s orbit of Mars, and the album was released on the same day that the Mars orbit was achieved. The sound of this recording is immense, as one would expect. It is a sweeping, spacious sound that was recorded at the Megaro Moussikis concert hall in Athens, which is renowned for its acoustics.

As with every other aspect of this recording, the sound engineering is top-notch, and this makes ‘Mythodea’ good for demonstrating the dynamic range and soundstage of a sound system. The CCB-8s had no trouble keeping up with the bombast of ‘Mythodea.’ The design of the CCB-8s suggest a higher than average dynamic range for bookshelf speakers, and here it was proven. The CCB-8s brought this enormous ensemble of performers into my family room with visceral power and precision. The sound was larger than life. The Greek National Opera towered above all and were foremost in the soundstage, but the orchestral elements did not get lost amidst the furor. If you do not have room for 200 plus musicians and performers in any one of the rooms in your home but still want to experience Mythodea, my experience was that a pair of CCB-8’s and a capable subwoofer will do nicely as a substitute.

Moving back to a simpler music, I decided for a solo instrumental album, and one could hardly ask for a purer sound than that of the harp. One harp recording that comes highly recommended is ‘Fantasies and Impromptus,’ performed by acclaimed harpist Lavinia Meijer, which, as the title suggests, is a collection of fantasies and impromptus. Fantasies and Impromptus are musical composition styles that have a sense of improvisation even though they are prearranged compositions. As such, they lend themselves to a playfulness that has to be very attractive to a harpist. The recording quality is extremely good, as one would expect from a SACD of performances from one of the world’s foremost harpists. Lavinia’s performance can be dazzling, with dizzying glissandros and powerful, fierce crescendos. Her mastery over this archetypal instrument is clear in this recording. 

This lovely album sounded exquisite on the Hsu CCB-8 speakers. It was easy to discern the close microphone placement in this album, and the resultant sound was as though the listener was seated only a couple meters away from the harp. One striking thing I did not expect from a solo harp recording was the tremendous dynamic range in the recording, perhaps as a consequence of the vast dynamic range of the SACD format. Perhaps I am too accustomed to those harps recordings that only serve as mood music for relaxation, whereas the arresting dynamics of this serious performance demand attention. The harp as recorded here could be soft and subtle and also powerful and resounding. The string plucks can have a striking attack, and the harpist controls the decay which can be made to either linger or suddenly cease. This dynamic range combined with the sharp attacks of the harp showed off the razor-sharp transient abilities of the CCB-8. If you are looking for background music, this recording is certainly not that; the CCB-8s brought this harp performance to the fore with a terrific energy but without losing its subtlety. 

Turning to something closer to how pop or rock music would be mixed, in other words, something with a lot more instrumentation, effects processing, and compression, I loaded up L.S.G.’s electronic music masterpiece ‘Into Deep.’ ‘Into Deep’ is one of those albums that is meant to be listened to in it entirety, from beginning to end. The music itself lands somewhere between ambient and techno; it is a melodic, psychedelic journey that drifts back and forth from mellifluous, spacious sweeps into hard-driving thunderstorms of percussion. Analog synthesizers have their day in ‘Into Deep,’ as the album is almost entirely composed of the warm, otherworldly sounds save for some sampled percussion instruments and some sparse female vocals.

While I have listened to this classic album many times over the years, I haven’t quite given it the kind of presentation that I listened to with the CCB-8s. I had only ever listened to it on headphones, desktop computer speakers, bedside speakers, and so on. Now, on a serious, full-range system in a properly-setup room, I was giving this album the treatment it deserved, and it was as though this old favorite had been completely remastered. I had never heard this album with any real imaging before, due to the systems I had previously heard it on, and the difference was stunning. I will say that the CCB-8s knocked this particular piece of music out of the park. The soundstage was wide and enveloping, but imaging was still precise when the recording called for it as it was on the percussion and vocals. I didn’t feel the dynamics were hindered even when I cranked it for moments of heavy percussion. ‘Into Deep’ was a great album to revisit, and hearing it on the CCB-8s setup in a suitable environment allowed me to hear elements that I had not noticed before.    

Film and Television

One film that I used to look at the CCB-8’s dynamic range is the 2011 movie ‘Drive.’ While that might not seem like anyone’s first choice to evaluate a speaker in that respect, I think ‘Drive’ is a superb movie for this, because dynamic range means the difference between loud moments and quiet moments in a sound mix. Some of the movies that are used to demonstrate dynamic range are always loud, but in reality that is a poor choice because there is no contrast against quiet or medium loudness levels. Similar to compressing a song recording for radio, if the loudness level stays relatively constant, the dynamic range has been squashed. In comparison, ‘Drive’ has stretches of quietude punctuated by bursts of some kind of violence. This is a great movie to watch loud as a result, since when something does happen, it can be quite startling.

The CCB-8 speakers proved to be a good fit for the ‘Drive’ sound mix. They were able to match the large swings in dynamics without any problem that I could hear. The retro-80’s synth pop music sounded great as well as Cliff Martinez’s brooding electronic score. The car chases roared to life on the CCB-8s, and the gunshots were jolting. Dialogue intelligibility was never a problem. I did not feel this terrific sound mix was held back in any way by these speakers.

Another movie I decided to watch was ‘Oblivion,’ the 2013 Tom Cruise science fiction vehicle. This movie looks and sounds great. There are a host of neat elements in the sound mix, but what really stands out for me are the robot sounds of the combat drones. For me, that is the best part of the movie, and it cannot be played loud enough. It isn’t just the robot sounds themselves, it is the way they are incorporated into the sound mix. It is a really bizarre and quite wonderful sound creation. The rest of the sound mix is fine too. The score is quite derivative of the ‘Tron Legacy’ score, and you can just hear the producer or director telling the composers to make the music like ‘Tron Legacy,’ since that turned out to be such a popular soundtrack. It isn’t bad at all, just not very original. However, as far as I am concerned, the ‘Oblivion’ sound mix belongs to the robot.

I cranked the volume for ‘Oblivion,’ and the CCB-8 speakers were up to the task. In a very diverse sound mix, thought the CCB-8s acquitted every element of it well. Airships flying through thunderstorms, drone laser blasters dueling against .50 cal machine guns, nuclear explosions, and giant alien robots: all sounded convincing however far-out the movie scene was. ‘Oblivion,’ as a movie, sounds big and cinematic, and the CCB-8s were able to convey that effect. As loud as I pushed the volume, I did not run into anything I thought was distortion. While these speakers would doubtlessly run into distortion if pushed hard enough, I think that for most people’s tastes, they are able to stay clean at louder levels than most would ever run them at. As I heard with the ‘Mythodea’ album, the CCB-8s can scale to immense soundscapes as well as well as softer and more intimate scenery.

For a sound mix of more conventional television programming, I decided to give season 2 of ‘Fear the Walking Dead’ a go. I had the blu-ray set kicking around for awhile but had not come around to watching it yet, and I guessed it would be a good demonstration of dialogue intelligibility, music, and effects sounds that are typical for a television show. I was certainly correct about dialogue, since ‘Fear the Walking Dead’ season 2 was rather talky for a TV show about a zombie apocalypse. The music was mostly atmospheric pieces for establishing mood by ex-Tangerine Dream member Paul Haslinger, but the score was sometimes punctuated by a pop or rock song from the likes of David Bowie, Surfer Blood, and even Patsy Cline. The Hsu CCB-8s were not challenged by this sound mix. Dialogue was always perfectly clear as was music and action. Dialogue was not washed out by groaning zombies, although it could be argued that the zombie groaning itself is also dialogue. The occasional bouts of action sounded spot-on; zombie skulls getting bashed in had a nice, sickening crunch. The opening titles music had a jarring buzz noise, which the CCB-8s recreated with sufficient alarm. Overall I was hoping for more actual zombies than what ‘Fear the Walking Dead’ season 2 delivered, but I have no complaints about the sound reproduction by the Hsu CCB-8 speakers. The show sounded great with them.

Since the coaxial design promised a good near-field sound, I tried the CCB-8s as desktop speakers. As expected, they sounded fine as desktop computer monitors. They sound as good at two feet as at ten feet. The desktop surface does change the sound character, but that would occur to any speaker from changing the acoustic environment. Most people likely would not have desktop space for such large speakers, but for those who want extreme overkill desktop speakers, these do work in that application. As mentioned before, care should be taken to eliminate acoustic reflections off of the desktop surface itself for any speaker used in that setting.

Hsu Research CCB-8 Bookshelf Speaker Measurements and Analysis

The Hsu Research CCB-8 bookshelf speakers were measured in free air at a height of approximately 9 feet and gated at 14 ms. At this window gate, some resolution is lost below 140 Hz, and accuracy is completely lost below 70 Hz and so that range should be ignored. The microphone was placed 1 meter away from the speaker at a height level with the tweeter. All measurements are unsmoothed.

Hsu Research CCB-8 bookshelf speaker response curves

The direct-axis frequency response curve for the CCB-8 is not perfect but it is not bad either. It should be kept in mind when viewing these curves that this speaker was not intended to be listened to on its direct axis, but around 15 degrees off axis. The 100 Hz bump is more of a measurement anomaly than the speaker’s actual low frequency performance. Up to 10 kHz, the response is respectable, if imperfect. It stays within a +/- 3 dB window, although we do see a slight bump and dip near the crossover frequency of 1,500 Hz. These narrow ripples and dips are imperfections, to be sure, but the overall response stays within a baseline amplitude, and, in terms of audibility and accuracy, this is much more preferable to wide bands of elevation or depression. Once we hit 10 kHz, the treble hits some spikiness on direct axis that rapidly falls down as we go off axis, although there is still some of it at 10 degrees off axis. If listened to on its direct axis, this is likely to make the CCB-8 a bright speaker, but we see in the directivity indexes and sound power that this elevated treble is very directional. One interesting feature that can be gleaned here is to see how the horn affects directivity above the crossover point, where the dispersion becomes much more restricted.

Hsu Research CCB-8 Bookshelf Speakers horizontal frequency response +/-90 degrees from axis: 3D view

Hsu Research CCB-8 Bookshelf Speakers horizontal frequency response +/-90 degrees from axis: 2D view

The above graphs depict the CCB-8’s axial response out to 90 degrees in 10-degree increments. As was alluded to by the directivity indexes, the CCB-8s rapidly narrows its dispersion pattern above the crossover point. The dispersion of treble frequencies is tightly contained. We also see the high-frequency response above 10 kHz has come down substantially at 20 degrees without heavily impacting the rest of the response. This speaker’s most neutral overall response looks to be between 15 degrees and 25 degrees, and it is at this angle that it is best listened too. While our measured response at 15 degrees is not bad, they do not match Hsu’s claims of +/-2dB from 50 Hz to 20 kHz. Those who suffer from high-frequency hearing loss (a huge chunk of the older adult male population) might benefit from listening to the CCB-8s on the direct axis, but most listeners would be more comfortable listening at the said 15-25 degree angle.

 

Hsu Research CCB-8 Bookshelf Speaker Polar Map

 The above polar map of the horizontal dispersion of the Hsu CCB-8 speakers depict the same information as the two waterfall graphs above it, but tells the story in a different way that can offer further insight regarding its behavior. In this graph we get a better idea of the kind of controlled directivity that is occurring at high frequencies. Dispersion is kept nicely uniform above 5 kHz. Below 5 kHz there is some broadening to the mids, and that looks to be the horn’s way of controlling the tweeter’s output. The dispersion seen here overall is not as broad as other speakers I have measured, which is exactly what one would expect from a constant directivity design. As we saw with the waterfall graphs, the most linear axis looks to be around 15 to 25 degrees.

Hsu Research CCB-8 Bookshelf Speakers vertical frequency response +/-90 degrees from axis: 3D view

 The above graph depicts the CCB-8’s frequency response behavior on the vertical axis. As one would predict by its design, there is not much difference in performance between the vertical and horizontal axis. Orientation does little to affect its performance, so it can be used on any of its sides without any serious acoustic penalty. This can be handy for those who want a powerful bookshelf speaker but have a height restriction of less than 11.” The absence of any lobing artifacts demonstrates why the CCB-8 makes for a good center channel speaker. On traditional center speakers, woofers are aligned on a horizontal plane, and this will cause cancellation artifacts off-axis, sometimes as close as 10 degrees off-axis. This can result in an erratic sound for those who have to sit off to the side of the direct axis of the center speaker. The Hsu CCB-8 has none of these drawbacks. One drawback that it does have is that, since the upper treble on the direct axis is elevated, users may want to aim the tweeter above or below the listening position by 15 to 25 degrees. In my own listening, I aimed the tweeter over my head when seated at the listening position for an approximate 15-degree angle. 

 

Hsu Research CCB-8 Electrical Impedance and Phase

The impedance profile of the CCB-8 doesn’t exhibit anything problematic. We can see that the port tuning frequency is just above 60 Hz. That was performed with two ports open, and if we sealed a port, that saddle shape would move down in frequency. Hsu states the nominal impedance of the CCB-8 to be 6 ohms, and that looks to be correct. Our measured impedance minima shows 5 ohms, but Hsu states 4 ohms in their specifications. No reasonably engineered amplifier would have a problem with this load, and even budget AVR amps should be able to handle this without too much of a problem. The toughest part of this profile would be the 5-ohm dip just under 200 Hz, but the phase angle is not very steep here.

Hsu reports the CCB-8 sensitivity in half-space at 94 dB at 1 meter for 2.83v, and our measurement of 93.8 dB largely agrees with their specification. Of course, half-space sensitivity converted to full-space sensitivity means a drop of 6 dB, which puts the CCB-8 at 88 dB sensitive full-space by their own specifications. That is above average for a bookshelf speaker, but do not mistake its half-space spec to mean it is a high-powered speaker that can handle THX Reference levels in a large room. The half-space sensitivity specification is simply the result of the setting it was measured in. In a medium-sized room, the CCB-8s can get louder than most people would ever want, but those who like loud-listening in a large room are going to need some much larger speakers. 

 

Hsu Research CCB-8 port sealing effects 

We did groundplane measurements to gauge the effects of sealing the ports on the CCB-8. Sealing the ports will only affect the low frequencies, so we restrict our window to that region. Leaving both ports open gives a slight rise at 90 to 100 Hz of almost 2 dB. Sealing one port gives the CCB-8s the most neutral response and also a bit more low-frequency extension. Sealing both ports effectively rolls off the response at a gradual 12 dB/octave slope starting at 100 Hz. Those who like beefier bass would be advised to leave both ports open, and this configuration necessitates a subwoofer crossed over at 80 Hz. While the use of a subwoofer is recommended with the CCB-8s, if no sub is available, sealing one port would be the preferred mode of operation, since it provides the most deep bass at tangible levels between all modes. Those who want the flattest response should also run the CCB-8s with one port sealed.

Hsu Research CCB-8 Bookshelf Speaker Conclusion

The CCB-8 speakers are the kind of addition to an audio setup that makes you want to re-listen to your music collection to see how it sounds on this new gear. Their holographic imaging is the best I have heard in my own room to date. It is eerie how precisely sounds seem to emanate from specific locations over the soundstage. It is not just center imaging either, which I have heard lots of speakers do well (although few do this as well as the CCB-8s); it is over the entire soundstage which the CCB-8s stretch out as a large swath extending well outside their physical locations. As I type this, I am listening to the CCB-8s in my home theater room. I normally write on my desktop computer, because it is easier to write there, but I wanted to listen to the CCB-8s some more, and it is worth the inconvenience of writing on this laptop to hear their magic on my old albums (by the way, current album: William Orbit’s ‘Hinterland’ under his ‘Strange Cargo’ moniker).

To be sure, the CCB-8s are not without their eccentricities. Their direct axis response is bound to be rather bright. But, I cannot fairly hold this against them since they are intended to be listened to at a 15 degree angle with the speakers toed-in in front of the listener. However, a lot of buyers will likely end up disregarding the positioning instructions in the manual and aim the speakers directly toward the listening position. On direct axis, their hotter response above 10 kHz will cause some sibilance in the ‘S’ sounds in dialogue and lyrics. I am not sure if it is possible to bring down the direct axis treble energy while keeping the same energy off-axis, but if that can be done, I think it could be an overall improvement. However, if it is not possible without lessening their superb imaging, then I would say that is not a worthwhile trade-off.

One change I want to see is the use of some bracing on the cabinet. While I did not sense any resonances, I would love to see some window bracing in there, if only for peace of mind. Yes, the sidewalls are thick and sturdy, but even just a little bracing can do a lot to impede any panel resonance. The ‘knock test’ doesn’t provoke any obvious decays or ringing in the CCB-8, but that is hardly a comprehensive test of cabinet resonance.

Something else Hsu would do well to consider is altering is the appearance. One person I showed the CCB-8s said they looked like “owl eyes.” As mentioned before, the yellow cone color is a bit loud. A more conservative cone color would give these speakers a much higher living room acceptance factor. Something else that might help is different cabinet colors. One color scheme I suggested to Dr. Hsu that I think would be cool is a solid maroon cabinet with maroon cone. Seriously, that would look wicked against the black surround and black dustcap. Everyone reading this review needs to take a moment and send Hsu an email imploring them to build a CCB-8 with maroon cone and cabinet. With enough social pressure, they may cave in!

Going back to the CCB-8s positives, I should also mention their imaging off-axis. As discussed before, the inward toe-in of a constant directivity speaker does a good job of holding a stable center image when listened outside of the central listening position. This doesn’t really hold out to extreme angles, but it does work over typical seating areas in front of the speakers, and it makes a phantom center speaker much more viable than it normally would be. Phantom center speakers are when the front left and right speaker simulate the presence of a center speaker, but the problem with that is on conventional designs if you are not sitting equidistant from the left and right speaker, then the soundstage can become heavily weighted toward the speaker you are closer to. With the CCB-8s and their recommended toe-in, traditional center channel content can still sound like it is anchored in space between the speakers, even if the listener is seated off to the side.

Other positive attributes of the CCB-8 is its above-average dynamic range. The large woofer magnet, 2” voice coil, horn-loaded tweeter, and healthy-sized cabinet all add up to give the CCB-8s punch beyond that of typical bookshelf speakers with 5” and 6” woofers. Furthermore, the ability to use the CCB-8s on any of their sides without any audible penalty gives them a bit more placement flexibility than normal bookshelf speakers. Their dual use as a center channel speaker gives you the advantage of a fully matched front stage speaker system. This is in opposition to many speaker product lines where the center speaker has such a different sonic fingerprint than the left and right main speakers due to different driver positionings that they can hardly be considered to be a matching set, at least from a sonic perspective. Moreover, there are no off-axis lobing artifacts in the CCB-8 that are found in almost every other conventional center speaker design. It is also worth mentioning once more that they can be listened to up close as well as far-field. Distance from these speakers does not alter their sound, only their loudness. Large though they are, they can be used as near-field, desktop speakers.

Along with the performance advantages, buyers also get Hsu’s highly-regarded customer service, a 7-year warranty, and Hsu’s swift shipping and good packing 

Final Considerations

To wrap this review up, I enjoyed listening to the CCB-8s and wish I had more time with them. I have heard much, much more expensive speakers that could not image nearly as well, and I do intend to eventually procure a pair of my own as a reference set for their extraordinary imaging abilities. I think those who purchase a pair for stereo listening and take the time to set them up properly will find themselves rewarded with exquisite imaging, good spectral balance, a rich, full soundstage, and sharp, punchy dynamics. A surround sound set would make for an excellent home theater system as well. When considering how well they perform, I think that their cost is modest, and I think a pair will find a permanent place in my home in the near future.

Hsu Research CCB-8 Bookshelf Speakers and Center Speaker Review
MSRP for Hsu CCB-8 Bookshelf Speakers in satin black finish: $699 per pair or $ 369 per single
MSRP for Hsu CCB-8 Bookshelf Speakers in Real Wood Rosenut finish: $859 per pair or $449 per single

Hsu Research
985 N. Shepard Street
Anaheim, CA 92806

www.hsuresearch.com

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
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• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Imaging
Dynamic Range
Fit and Finish
Performance
Value