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.