PSB Synchrony B600 Bookshelf Speaker Review

PSB Synchrony B600 Introduction

PSB Speakers has been an audio industry stalwart for over 50 years now, and they have to be doing something right to last that long in this business. Much of their success is undoubtedly due to the high praise they have garnered in review after review of their products. In the past, Audioholics has found their products to be excellent, but it has been a long time since we have last had our hands on one of their designs, and we figured it would be a good time to see what they have been up to. That brings us to today’s review of the PSB Synchrony B600, their highest-end bookshelf speaker. At $2.8k/pair, they aren’t the cheapest speakers around, so what can PSB do to justify that kind of price for a pair of medium-sized bookshelf speakers? That is the question we will be asking in today’s review. Let’s dig in to find out…

Appearance

While the B600 speakers look good, the styling doesn’t break any new ground with respect to high-end loudspeakers. They are basically oblong boxes that are made to look as nice as oblong boxes can look. It’s like functionality came first on these speakers, and then they were handed to industrial designers who had to work around a set design. There is no cabinet curvature here, so they can’t really escape their boxiness. The edges aren’t really beveled or shaped, although there is a very slight rounding in order to keep them from becoming hard angles. The units that I received came in the gloss black finish, and it was nicely done with no irregularities or orange peeling that I could see. The B600s also can be had in a satin walnut finish. The most notable visual feature is a brushed black aluminum plate on the front baffle that holds the drivers. The aluminum plate does have a slight beveling which lends the B600s a somewhat stately demeanor. There is also a smaller aluminum plate on the rear panel that holds the port and binding posts. Since the rear is usually out of sight, PSB didn’t really have to do that, but it does lead to an aesthetic symmetry that I can appreciate.

One slightly unusual touch is that the tweeter is mounted below the woofer instead of above as on most two-way bookshelf speakers. That is unlikely to bother anyone, and audio hobbyists are probably the only ones who would notice. At just a glance, they might think that the speaker has been placed upside down, but the PSB badge does indicate the B600’s correct orientation. This can all be hidden by the magnetic grille, which is just boring black fabric draped over a frame. Of course, the grille considerably dulls the appearance of the B600s, and when it is attached, the speakers look like a featureless black box. I think that the B600s look much better without the grilles, but some people just cannot abide by the appearance of exposed drivers. The woofer has a cool-looking carbon fiber weave, and the tweeter is a normal-looking aluminum dome mounted in a shallow waveguide. Even without the grille, the B600s have fairly restrained styling, so the vast majority of people aren’t likely to object to their appearance.

Design Analysis

The B600 is a two-way bookshelf speaker that looks like a fairly traditional design on the surface, minus the lower-mounted tweeter and upper-mounted woofer, but there are some design touches that promote this speaker above typical two-way bookshelf speakers that do lead to its higher pricing. Let’s start our discussion of its design with the tweeter. The tweeter is a 1” titanium dome mounted in a shallow waveguide with ferrofluid cooling. As a tweeter diaphragm material, titanium is substantially more expensive than aluminum, but it is twice as strong as aluminum while being only 60% heavier. That means that a titanium tweeter can either have the same stiffness as an aluminum tweeter but be lighter, which would make it more sensitive, or it can have the same weight but be a stronger diaphragm which means non-linear ‘break-up’ modes can be pushed up to higher frequencies away from humanly audible ranges. Titanium is an excellent thermal conductor too, so it should be able to quickly transfer heat away from the motor and reduce thermal compression artifacts.

The tweeter motor uses ferrofluid in the gap. Ferrofluid is common but still a welcome attribute because it has some real advantages. One advantage is thermal transfer; it draws heat away from the voice coil which, again, decreases thermal compression and increases power handling. It also helps to center the voice coil in the gap, and this leads to better reliability, where the voice coil is less likely to make contact with other metals in the gap which can knock it out of alignment. It can also help damp resonances in the tweeter’s response. The B600 uses a neodymium magnet in the motor. Neodymium is much more powerful than iron ferrite, on average 10 to 15 times stronger, so a little neodymium goes a long way, but it is also a lot more expensive. One disadvantage of having a smaller magnet is that it cannot radiate heat as efficiently as a large one, so the use of ferrofluid and a titanium dome is a good assist in thermal management. 

The tweeter is mounted in a small conical waveguide, and this should help control the directivity of the sound, especially at the lower end of its bandwidth. That is a good idea when mating a 1” dome tweeter with a 6.5” woofer. The combination of a 1” dome tweeter with a 6.5” woofer is very common with two-way bookshelf speakers. However, the fact is that they don’t normally have perfect directivity matching, because the woofer will start to narrow its dispersion at any usable crossover frequency for a typical 1” dome tweeter. The directivity mismatch between these driver sizes is not usually a major audible flaw, but it can cause irregularities in the off-axis that a waveguide can prevent. A phase lens is built into the waveguide that covers the center of the tweeter dome. The purpose of a phase lens is to block sound from the raised center of the tweeter from reaching the listener, as its forward distance will cause it to be slightly out of phase with the lower edges of the dome. Such a small distance difference will likely only make any difference in very high frequencies. Another advantage is that the phase lens could offer additional protection against anything striking the fragile metal dome.

The woofer cone is made of carbon fiber, a very light yet tough material, but, as anyone in aerospace or automotive engineering will tell you, also a bit expensive. The high stiffness should allow the cone to play up to high frequencies without running into nasty ‘break-up’ modes where the rapid motion of the cone can cause it to bend. This bending is very audible and can sound awful, so the more it can be filtered out, the better the sound. The light weight of carbon fiber allows it to be moved without needing a ton of wattage, and this will increase sensitivity as well as dynamic range. The woofer is mounted in a cast aluminum basket, and the motor uses a shorting ring to suppress induction-based nonlinearities. 

The tweeter is crossed over to the woofer at 2.2kHz in a Linkwitz-Riley fourth-order that also factors in the acoustic slopes of the drivers so it is not a fully electric crossover. A full fourth-order electric crossover would have a ton of elements and would barely fit in a medium-sized bookshelf speaker. The crossover circuit uses high-voltage film capacitors and high-current inductors. PSB claims that this all adds up to a phenomenally flat response of +/-1.5dB from 55Hz to 20kHz, and we will see how close those claims match reality when we take a look for ourselves in our measurements. With two sets of binding posts, the B600s can be bi-amped or bi-wired, and this is an absurd feature on a medium-sized bookshelf speaker with a 150-watt power-handling spec. There is no real advantage in this unless you happen to have two lower-powered stereo amps instead of one good amp, but how often is that the case? PSB should just have just saved the money and gone with a single set of binding posts instead of catering to ridiculous audio marketing checklists.

The enclosure is a fairly solid MDF construction. PSB claims there is extensive bracing inside, but I wasn’t sure I could remove exterior elements without damaging the speaker, so I wasn’t able to see that for myself. The hefty 23lbs. weight of each speaker does suggest some serious cabinetry. The front-mounted 5mm thick aluminum plate is decoupled from the MDF of the cabinet, and to describe in greater detail, I will quote PSB’s data sheet: “The aluminum plate on the baffle has threaded pins on the rear that grab six small isolation cups, three on each side, which suspend the aluminum plate between the two sidewalls of the enclosure. The aluminum plate has contact with the cabinet only around its perimeter. The isolation cups decouple the aluminum plate from the enclosure, another measure that helps preserve fine detail.” I have to wonder about the measurable, let alone the audible, advantages this would actually yield, but it is an interesting design detail that shows PSB is trying to make a really high-end loudspeaker. A more effective idea might have been to mount the tweeter and woofer frames directly to the aluminum baffle, and that way the baffle can help to serve as a heatsink thereby keeping the drivers in an optimal operating temperature for longer.

The feet were designed by IsoAcoustics and are based on their Gaia III isolators. While they seem like perfectly competent loudspeaker feet, I definitely do not buy the claims that they would offer any “improved micro-detail, clearer transients, a wider soundstage, and more precise imaging.” This is nonsensical. All feet need to do is keep enclosure vibrations from audibly reacting to whatever surface they are resting on. These feet seem to do that, but to suggest they do more than that is nonsense, in my opinion. The B600 has a rear-mounted port that has a 2” diameter and a 6” depth and is flared on both ends. Those dimensions suggest a moderately deep tuning frequency for a bookshelf speaker of this size, but we will see for ourselves in the listening and measurements section. The magnetically attached grilles are just fabric draped over simple frames. The grille frames are a tad blocky and would lead to some slight diffraction, so these speakers would technically be better performers with the grilles off, but I doubt that there would be a significant audible difference either way.

The binding posts look cool but are a hassle to use. They are usual 5-way binding posts but covered in some kind of transparent plastic shell that blocks several points of connectivity that a 5-way binding post could have. Bare wire is tricky to thread through the metal post hole because it is partially blocked by both the plastic cover as well as the jumpers. Spade connections cannot be used because that is blocked by the jumpers. In order to use banana plugs, you have to pull some plastic inserts out of the top end of the binding posts, and they don’t come out easily. Of all the binding posts that I have dealt with, these are among the worst.

The overall design and construction of the B600s promise a very high-fidelity sound, but is that what they actually deliver? Let’s take a listen to find out…

Listening Sessions

In my 24’ by 13’ (approximately) listening room, I set up the speakers with a few feet of stand-off distances between the back wall and sidewall and equal distance between speakers and listening position. I angled the speakers to face the listening position. The listening distance from the speakers was about 9 feet. Processing was handled by a Marantz 7705, and amplification was handled by the Monoprice Monolith 5x200. The speaker stands were some Monoprice Monolith 24-inch Steel Stands. Equalization was used but not automated room correction equalization. A subwoofer, the Hsu Research VTF-15h mk2, was used when noted.

Music Listening

A fantastic new recording for exhibiting vocal reproduction is “Her Greatest Moments at the MET,” a new album I found on Qobuz’s Discover page. This album features live recordings of acclaimed opera singer Renée Fleming at The Metropolitan Opera. The Grammy-winning Fleming has performed there more than anywhere else and considers it her artistic home, so this recording is a celebration of her many performances there. There are songs taken from a variety of performances such as “Faust,” “Don Giovanni,” and “La Traviata.” As a compilation of highlights, this should be classical music fireworks from beginning to end, a terrific demo album for audiophiles. This late 2022 release from the Decca label was streamed in a high-resolution. 

When I first started listening to “Her Greatest Moments at the MET,” I thought I had set up the speakers incorrectly, even though they sounded fine with content I had listened to previously. The imaging was slightly odd. I double-checked the setup, and everything looked fine. I realized it was the recording, and these live performances at the MET had to keep the microphones out of the way and probably used overhead microphones that might not have had the most optimal locations for natural imaging on a playback system. This is a subtlety that might not have been readily apparent on another loudspeaker system. In live opera performances, the performers can be in a variety of locations on the stage, and the B600s imaged that with precision; I could hear exactly where the performers were on the soundstage. Instrumentalists were imaged nicely as well, and this recording put the listener in the middle of the orchestra rather than as a more distant audience member. The B600s wrapped the orchestra around the listener with an enveloping staging. Tonality was very good with both singers and instrumentalists, and I didn’t notice anything that seemed exaggerated or curtailed. Fleming’s soprano voice was built for opera, and her more dramatic moments demonstrate a talent that is almost inhumanly good. One highlight is the selections taken from “Manon” where her mellifluous voice soars amidst the orchestra yet without being piercing or searing. This album should be given attention by every opera lover, and hopefully, they will have a loudspeaker system as good as the B600s if they give it a listen.

Another new release I found via Qobuz’s Discover was “Phoenix” by Lakecia Benjamin. Lakecia is an accomplished saxophonist who has toured with a long list of major artists, and “Phoenix” is her fourth studio album. It is on the energetic side of jazz with intricate compositions and lots of accompanying artists. Her sax leads her regular quartet which features piano, bass, and drums, and she is often joined by many guests including singers, string trios, and trumpeters, among others. The recording quality is first-rate, and I won’t be surprised if this album is an early shoo-in at the Grammys for jazz instrumental album. This hi-res album is sure to make any good audio system shine. 

Much like I heard with other content, the imaging was excellent, with Benjamin’s alto sax emanating from a pinpoint position squarely in the center of the soundstage. The drum set was clearly close-mic’d, since I could hear various percussion instruments spread out over the soundstage. Trumpets closely flanked Benjamin’s sax on the left, and piano and electric keyboard could also be heard to have close miking. As with many other studio recordings, the intended effect is to have a ‘they are here’ quality rather than ‘you are there.’ On this count, the B600s executed that intended effect nicely and brought Benjamin’s band into my living room as though this were a private performance arranged for me alone. The instruments all sounded very natural, although one peculiarity I heard was that Benjamin’s sax was a bit more recessed than would be expected considering that she is the lead player for much of this album. This seemed like a choice by Benjamin in order not to overshadow her bandmates, but in a real jazz band, that sax would be significantly louder than it is on this recording. The B600’s low-frequency extension was capable of reproducing the bassist and percussion on this album in full, and I didn’t feel the need to bring subwoofers in at all. The bass from these average-sized bookshelf speakers was quite impressive. “Phoenix,” as heard on the B600s, was a terrific listen. The ability of these bookshelf speakers to effect the sound of a full jazz band was phenomenal. I think that jazz aficionados would love “Phoenix” as well as the B600s.

For something radically different, I loaded up “Quantum Gate/Quantum Key” by Tangerine Dream. This 2017 album was the first put together after founding member Edgar Froese’s passing. Froese had been the one constant in the group from its inception in 1967, so his death in 2015 couldn’t help but have a profound change on the music that they would create afterward. “Quantum Gate/Quantum Key” retains much of his musical spirit since it was created using ideas and sketches left by Froese. Nonetheless, it does have a different sensibility from previous albums, but that is no surprise since Tangerine Dream has been through many different phases in its 55+ year history. I think that this post-Froese period has produced some fantastic albums with their cleanest productions so far, and they definitely kill with a competent sound system, so I decided to see what the B600s could bring to this music.  

This album opens with an electronic bass sequence with some notes that plunged fairly deep in low frequencies. The B600s rendered this bass line so capably that I literally got up to check if any of the subwoofers were also playing the music back somehow; they were not. As futuristic electronic music, the imaging could take many forms, from pads that encompassed the width of the soundstage to leads that had laser-like precision. The B600s could actualize whatever was called upon from the album. Imaging seemed to extend well outside of the width of the speakers’ placement at times. Many of the tracks in this album are very densely layered with a profusion of different electronic instruments, but the B600s managed to keep them all distinct and identifiable instead of blurring them into a confused jumble. An example of this can be heard in track 6, “Non-locality Destination,” a composition as intricate as anything I have heard from Tangerine Dream. The various synths were distinguishable yet integrated into a cohesive whole as a song. Track 9, “Genesis of Precious Thoughts,” brought in some very low-frequency percussion and bass. The B600s were handling the bass on that track very well, but I thought I would bring in a subwoofer to see what the audible difference would be. The sub did lend the sound more gravitas and oomph, but it didn’t uncover something that the speaker wasn’t already playing. In other words, while the addition of a sub did improve the experience, it wasn’t as if the B600s were missing anything. They still delivered a full sound, and this album could still easily be enjoyed without a sub on these speakers. “Quantum Gate/Quantum Key” was sheer ear candy to hear on the B600s, and anyone looking for bookshelf speakers that could handle elaborate electronic or pop music has a superb option in these speakers.

To see how the speakers operated under a bit more pressure, I threw on Starkey’s “Ear Drums and Black Holes,” a 2010 album that has to be regarded as a classic in the genre of dubstep at this point. While this album applies most of its pressure in low frequencies, it also has a lot going on in mids and treble. At high volumes, “Ear Drums and Black Holes” can function as a good stress tester on any loudspeaker. Massive bass, sharp lead synths, and prominent percussion make for one banger after another. It would be the tool I would use to see how hard the B600s can rock.

Kicking off the first track, an easy-going tune with a thick bassline, again I had to wonder if the subwoofer was on. I knew that it wasn’t, but these bookshelf speakers were so competent in low frequencies that anyone who didn’t know better could easily assume there was a sub in action. To see what the difference was, I again brought in a sub. At low to medium volume levels, the sub did give a bit more definition to the lowest notes, but the difference was not huge. At higher volume levels, the sub did provide more thump than the B600s was capable of, but it was impressive how much bass the B600s could deliver even when pushed harder. I backed off the volume when I saw the woofers really moving since they must have been at or near the limits of excursion, but that was at a pretty high loudness level. Bringing in the sub and high-pass filtering the speakers definitely enabled an overall increase in headroom and significantly calmed down the motion of the woofers. While I wouldn’t try to use these speakers to power a house party, I think they could get more than loud enough for any user with reasonable expectations. Kick drums and toms landed with a hit, and the lead synths cut a crisp, well-defined path. Bass lines were beefy, even without a subwoofer, but at high volumes, the B600s couldn’t give any real muscle to the very lowest notes. Keep in mind, this is electronic music with deep bass, and the B600s’ bass extension would suffice for any acoustic music except perhaps for those pipe organ recordings from massive organ installations.

Movie Watching

One movie I had been meaning to see for a while was “Nocturnal Animals,” a 2016 psychological thriller starring Jake Gyllenhaal and Amy Adams. The plot is about an art gallery owner that discovers a manuscript written by her ex-husband that contains a very troubling depiction of their marriage. This ignites deep regret about both her ex as well as her present husband that creates fissures in her life. I was intrigued by what I knew about the movie, and I figured that would be a good opportunity for the B600 to demonstrate what it could do for the sound mix of a big-budget Hollywood drama.

“Nocturnal Animals” turned out to be an engrossing movie. It was stylish visually as well as aurally but tastefully so, It had a minimalism and restraint instead of dazzle or extravagance. Much like the movie, the sound mix was very clean and sharp, so the precision of the B600s was a perfect fit. The mix was mostly dialogue based, but some ambient noises and music were used to express emotions that the characters would not exclaim aloud. The music was a sparse, moody score by Abel Korzeniowski, and it sounded terrific on this sound system. The music was exquisitely reproduced, and the dialogue was all crystal clear. With such a clean and uncomplex sound mix, there is not much else of note to say about the B600s’ reproduction of this movie, except that I thought it was terrific and didn’t lack much. The inclusion of a subwoofer might have given some of the orchestral work slightly more low-end heft but not much. I would recommend “Nocturnal Animals” to anyone who wants to see an unconventional noir, and even though it does not have a very rambunctious sound mix, it still deserves to be seen with a competent sound system like what PSB has provided me here.    

One movie I was excited to see was a new horror film from Niel Marshall titled “The Lair.” Marshall directed a slew of terrific genre movies in the early 2000s, “Dog Soldiers,” “The Descent,” and “Doomsday.” He turned his attention to television series and directed what are considered some of the best episodes of “Game of Thrones,” “Westworld,” “Hannibal,” and “Lost in Space” but then had a fairly high-profile failure with the reboot of “Hellboy.” Since then, he has returned to smaller-scale horror films, the latest of which, “The Lair,” concerns an air force pilot who crashes in a remote, hostile region of Afghanistan. She takes refuge in an abandoned bunker and stumbles upon the grotesque monsters that inhabit it. Horror movies can very often be a good vehicle for crafty sound mixes, since much of the tension is usually generated by sound rather than sight.

Compared to Marshall’s earlier efforts, “The Lair” was rather schlocky, but at least it was fast-paced and action-packed. The characters were thin, but the action scenes were plenty, giving the B600s a lot to work with. There were multiple battle scenes of US and British soldiers facing off against unearthly monsters, and the B600s did a fine job relaying the mayhem of human firepower versus alien melee attacks. Light arms such as rifles and handguns had a satisfying popping and snapping, and the Humvee-mounted .50 BMG had a thunderous roar as it took down Taliban and alien creatures alike. The aliens’ screeching and shrieking were exuberantly reproduced on the B600s, and it matched their repulsive appearance appropriately. One memorable aural moment was the obligatory autopsy scene on one of the creatures, a mandatory trope of this genre. The gooey sounds of the removal of the alien’s internal organs was given a sickening articulation by the B600 speakers, and every gruesome detail was vividly reproduced. The energetic score by Christopher Drake is a combination of orchestral clamor for the action scenes and sci-fi synths for the suspenseful scenes, and the speakers recreated the scope and tension that the music intended to convey. The B600 speakers’ bass performance was admirable in the absence of a subwoofer and certainly much better than would be expected from mere bookshelf speakers. While a sub would have given the movie more grunt and thunder, the speakers still managed to add some rumble and depth to the action. “The Lair” wasn’t a great movie, but it was watchable, and the B600s helped to make it quite entertaining by giving its vibrant sound mix a lively reproduction.

PSB Synchrony B600 Bookshelf Speaker Measurements & Conclusion

The PSB Synchrony B600 was measured in free air at a height of 7.5 feet at a 1-meter distance from the microphone, and the measurements were gated at an 11-millisecond delay. In this time window, some resolution is lost below 250 Hz and accuracy is completely lost below 110 Hz. Measurements have been smoothed at a 1/24 octave resolution.

The above graph shows the direct-axis frequency response and other curves that describe the R80 V2’s amplitude response in a number of ways. For more information about the meaning of these curves, please refer to our article Understanding Loudspeaker Measurements Part 1. The results here are not perfect but pretty darn good. The only flaws are the dip just above 1kHz and the drop just above 4kHz. Neither are major and aren’t likely to lend serious coloration to the sound. There is some unwieldiness above 15kHz but that isn’t a big deal since most people can’t hear that high with much acuity and there isn’t that much recorded content that high anyway. This speaker is a lot closer to neutral than not. Something which also helps here is that the directivity indexes are both very flat, and that means this speaker retains its tonality across a very wide angle. Therefore, the B600 would be easy to equalize because whatever changes are made are going to carry over across all angles in a consistent manner. This is the kind of loudspeaker that auto-EQ systems such as Audyssey love because it will conform to in-room target responses beautifully.

The above graphs depict the speaker’s lateral responses out to 90 degrees in five-degree increments. More information about how to interpret these graphs can be read in this article: Understanding Loudspeaker Review Measurements Part II. There isn’t a lot to see in these graphs that weren’t already seen in the previous graph. We do get a better look at just how high the correlation that the off-axis responses have to the on-axis response is. We also get a better look at the wooliness in the high treble region. I would guess that a lot of that has to do with the phase lens that is placed over the center of the tweeter. Again, unevenness above 15kHz is unlikely to manifest in anything audible unless it is extreme. The overall story here is that the B600s should have a nicely linear sound both on and off-axis.

The above polar map graphs show the same information that the preceding graphs do but depict it in a way that can offer new insight regarding these speakers’ behavior. Instead of using individual raised lines to illustrate amplitude, these polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is they can let us see broader trends in the speaker’s behavior more easily. For more information about the meaning of these graphs, we again refer the reader to Understanding Loudspeaker Review Measurements Part II.

The B600’s dispersion pattern as displayed by the polar map is not great but not terrible. The energy at off-axis angles tends to become a bit uneven outside of the 30-degree angle, but at least the response shapes don’t change from one angle to the next, and that is the reason for the flat directivity indexes. Within the 30-degree angle from the on-axis angle, the amplitude is fairly even and should yield a fairly neutral sound. The vast majority of listeners will be within a 30-degree angle, so that shouldn’t be a problem. Outside of that angle, there will be recessed output above 5kHz, and that will make the speaker sound a bit veiled for anyone listening at such a far off-axis angle. 

The above graph illustrates the difference that the frequency response takes when measured level with the woofer and measured level with the tweeter. Since the tweeter is the lower driver on this speaker, the woofer is more likely to be the driver at ear level, and when we look at the response measured on the woofer’s plane, it turns out to be a bit smoother in the treble range. All of the above graphs were made using the tweeter as the reference axis, but they would have been somewhat flatter were the woofer used as the reference axis. Tonally, there probably wouldn’t be a big difference in sound between the two, but it’s interesting to observe nonetheless because normally measurements conducted at the woofer level are less linear, but in the B600s, the woofer level is more linear, at least in the treble. The moral of this story is that for the most neutral sound from these speakers, listen with woofer at ear level, not the tweeter.

The above graph shows the B600’s response behavior along its vertical axis where zero degrees is directly in front of the tweeter, negative degree values are below the tweeter, and positive degree values are above the tweeter. Here we can see the crossover null encroach on the off-axis responses, but the good news is that the vertical off-axis response isn’t nearly as acoustically important as the horizontal. The B600 has about a +/-10 degree vertical angle from the tweeter before the null starts to kick in. That is enough to encompass any reasonable listening position, so users don’t need to worry about the exact millimeter of height to elevate this speaker on a stand.

The above graphs show the Synchrony B600’s low-frequency responses that I captured using groundplane measurements (where the speaker and microphone are on the ground in a wide-open area). The low-frequency response shown here is well-controlled and has a surprisingly deep tuning frequency, with the elbow of the curve happening at 40Hz. That is deep enough to catch most of the bass in acoustic recordings, and plenty of electronic ones as well. PSB characterizes the extension as 50Hz in a +/-3dB window out to 20kHz. That may technically be true, but I think that is actually a conservative take on the low-frequency extension of the B600. There is very clearly usable bass below 50Hz. It may not have tremendous output in that range and could compress at a lower amplitude level with respect to higher frequencies, but at nominal levels, it is there. Depending on the content and the listening conditions, users may not need a subwoofer with these speakers.

A port tuning frequency this deep also has an advantage when paired with subwoofers: there will be less interference from the port with the integration with the sub. There is typically a full period of phase rotation at the port tuning frequency of any ported loudspeaker because the woofer’s motion is a cycle ahead of the port output. It can be difficult to integrate a sub with speakers near port tuning frequencies because of this; the acoustic phase of the speaker is swinging wildly at this point, so getting the sub phase-matched in this region can be tricky, even for advanced auto-EQ systems. By moving the port tuning so low beneath traditional subwoofer crossover frequencies, the user can cross the subwoofer in a much more manageable range of phase behavior. So the transition from sub to speaker will be smooth and not plagued by nulls or peaks.

The above graph shows the electrical behavior of the PSB Synchrony B600. PSB specs this speaker to be 6 ohms nominal with a 4-ohm minimum. This should really just be considered a 4-ohm speaker. While most of the range stays well above 5 ohms, the speaker does dip to 4 ohms around 200Hz along with a fairly steep phase angle. Any decent amp should be able to handle that load just fine, but that might be pretty taxing for a cheap amp if you are really blasting these speakers. We can see from the dip between the low-frequency resonances that the port tuning frequency is about 45Hz. We can also see from the right-side peak being so much higher than the left that the resonant frequency of the enclosure is much higher than that of the driver. That is what I would expect since I doubt this 6.5” woofer’s resonance is anywhere near 45Hz.

I measured the B600’s sensitivity to be 87.2dB for 2.83v at 1 meter. This is close to PSB’s spec of 86dB anechoic, but they don’t give any specifics beyond that. 87dB is fairly good for a medium-sized bookshelf speaker with such a low-frequency extension. This is not a high-sensitivity speaker by any means, but it is higher than expected given the size and bass extension. I would recommend at least a 100-watt amp for a medium-sized room. I wouldn’t recommend that these speakers be used to fill a large room or listening distances further than a few meters.

Conclusion

Let’s bring this review to a close by briefly surveying some of the strengths and weaknesses of the product under review, and let’s start with the weaknesses as we always do. There aren’t really any serious weaknesses with the PSB Synchrony B600 at all. Everything about it ranges from competent to extremely good. The only part that PSB really should consider changing is the binding posts. Those are not good, but binding posts are a small matter. Once you have the speaker hooked up, it's all good news from there. 

That brings us to the B600’s strengths, the foremost of which is its sound quality. Its tonal accuracy is evidenced by its measured response as well as any extended listening. Its directivity makes it a cinch to equalize to any target response, which, as we mentioned before, makes these particularly amenable to auto-EQ systems like Dirac and Audyssey. Its dispersion pattern is good for both the horizontal and vertical axes. This leads to the superb imaging that I heard from them. It has enough dynamic range for any reasonable listening level in a medium-sized room.

Its low-frequency extension is particularly good for its size and form factor. With real extension to 40Hz, these can project a pretty full sound by themselves and won’t need the assistance of a subwoofer for a variety of content. If you don’t have room for tower speakers or a subwoofer but still want a sound system that can produce some bass, the B600s are a great choice. This also makes them good for a desktop speaker system (for those who have desk space for these speakers). It’s not that they can offer some real bass without a sub in a desktop environment, but if you choose to add a sub with these speakers, they can accommodate a lower crossover than the traditional 80Hz. That goes a long way toward eliminating subwoofer localization, and subwoofer localization is a bigger problem in a near-field system like a desktop system than in a typical in-room setup. Indeed, I used the B600s as desktop speakers for a while and thought they sounded terrific in that role.  

Aside from the sound, the B600s look the role of a luxury product, although it is pretty restrained in that respect. Buyers who want something more ostentatious for their money have better choices, but the B600s do look tasteful without being boring. These speakers look well-built, and that is not an illusion, because their build quality is very good. The enclosures have a nice sense of solidity and inertness, and the 23 lbs. weight is indicative of their beefy cabinetry. The drivers are no joke; with titanium dome tweeters and carbon-fiber woofers, PSB isn’t cutting many corners with the B600s. 

I don’t have a lot else to say about the Synchrony B600s. They are well-designed and well-built, and they look nice and sound great. However, I would hope as much since we are dealing with two-way bookshelf speakers that cost $1.4k each. There are a lot of well-known good recipes for two-way bookshelf speakers, and PSB has decided to adhere to a fundamentally good design with some embellishments to justify the higher price tag. What can I say: it works, and PSB has a genuinely good loudspeaker in the B600. I could very easily live with a pair as my primary sound system, and those who do choose to incorporate them into their sound system for either a two-channel setup or as a part of a larger-scale system will have made a great choice.

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
• — Very Good
• — 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