The Perlisten S4b speakers were 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 speakers’ 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. As we have come to expect from Perlisten, the S4b speakers boast a magnificently neutral response. There is hardly anything else to say; this is an accurate loudspeaker. All of the ‘flaws,’ such as the slight dip at 600Hz and the tapered treble above 17kHz, are well below audibility. The smoothness of the early reflections curve and the directivity indexes indicate that this speaker has a high correlation of the off-axis responses to the on-axis and listening window curves, so the S4bs can be equalized with very predictable audible results. They should have the same tonal balance over a wide area in front of them. What is more, with such ideal off-axis behavior, these speakers won’t require much in the way of acoustic treatments for a great sound.

The above graphs depict the S4b’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. Here we get a more in-depth look at the S4b’s terrific off-axis response. Many of these curves maintain a smooth shape out to the “listening window” of a +/-30-degree angle from the on-axis response. The response does fall off a bit after that, at least above 2kHz, but the tight amplitude grouping within that angle ensures a very accurate sound over a good-sized area. Here we also get another look at how tightly these responses hug the 90dB line. That is a beautifully flat response family.

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 of 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.

In these graphs, we get a better look at the width of the S4b’s horizontal dispersion. I have included the 180-degree graph so we can better see how the midrange dispersion relates to the treble range. As we saw in the previous graphs, the strongest and most even response occurs from the on-axis angle out to 30-degrees. Within that angle, you will be met with an accurate, neutral sound. The dispersion does tighten up a bit above 2kHz, but directivity control is still quite good overall. You do not need the S4b’s to be aiming right at you for an optimal sound, and they have quite a bit more flexibility than that for placement, at least on the horizontal axis. There is a lot of room to play for toe-in angles.

The above graph shows the S4b’s speaker’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.  It should be said here that the vertical response isn’t as critical as the horizontal response, so an imperfect vertical dispersion is much less of a problem. We can see here that there is a good amount of symmetry between the upper and lower angles of this speaker, thanks primarily to the beamforming array. To get a better understanding of how it works, let’s take a look at it in a polar map view…

Here we can see how constricting the beamforming array is on the midrange/tweeter band. It doesn’t extend to the woofer’s band of 1kHz and below since there is only one woofer which is not enough to form an array. The Perlisten S7t tower speakers used their four bass drivers down to 300Hz. Nonetheless, this tight beam of vertical dispersion is much better controlled than pretty much any other bookshelf speaker in this class. The best sound coverage occurs at +/-15-degrees, so if these speakers are placed anywhere near ear height, you will be met with a smooth response. With so little output at far off-axis vertical angles, acoustic treatments aren’t all that beneficial for these speakers, so don’t worry about using a heavy rug or ceiling diffusers for bettering the sound; the S4bs don’t need that. The symmetry of the response from the upper angle to the lower angle is remarkably, again better than most loudspeakers in this class. There is only one small asymmetry of note in the upper angle of around 30 to 40-degrees at 1kHz that is a crossover cancellation. It is a very mild null for crossover cancellation which is evidence of a highly optimized crossover circuit with steep filter slopes.

The above graphs show the S4b speaker’s low-frequency responses that I captured using groundplane measurements (where the speaker and microphone are on the ground in a wide-open area). Here we see an extremely flat response that tapers off to a textbook sealed roll-off slope. If used in a small room or near a surface, the low-end will get a boost, so users can probably expect to get usable bass well below 80Hz. However, these speakers were made to be used with subwoofers and will likely see an 80Hz crossover frequency in most cases. An advantage of the sealed design is that there are no port-related phase rotations that complicate the integration of a subwoofer nor are there any port-resonances that bleed into the lower midrange that can often be seen. The S4b could have been a ported design with more lower bass output, but it would likely have needed a larger cabinet for that (i.e., more difficult to mount and more expensive), and it wouldn’t have done much good anyway since these are likely to end up in systems with subwoofers. Going sealed was the right call for this speaker.

The above graphs show the electrical behavior of the S4b speakers. This is a fairly easy load that is not especially taxing anywhere. Perlisten rates the S4bs as 4-ohm nominal which is about right but it should not present any difficulty to all but the cheapest amplifiers. We can see here that the resonant frequency of the bass driver in this enclosure lies just below 50Hz. I measured the sensitivity of the S4b as 86.5dB for 2.83v at 1 meter. This is slightly higher than Perlisten’s sensitivity spec of 85.4dB for 2.83v at 1 meter. That is about what should be expected given the size and design of this speaker. It is not especially high not is it especially low but rather fairly normal. The S4b’s can get loud, but they do need some wattage to get there. I would look to be powering these with at least 100-watts or so to exploit their dynamic capabilities.

Conclusion

Before bringing this review to a close, let’s quickly go over the strengths and weaknesses of the product under review, and, as usual, we will start with the weaknesses. The problem with discussing the weaknesses of the Perlisten S4b is that there aren’t really any significant weaknesses. It does everything well, and the one area that anyone might criticize it for, low-frequency extension, was a matter of a very logical trade-off. Anyone dropping $8K for a pair of bookshelf speakers has a right not to receive speakers with any significant deficiencies, and with the S4bs, that is what they get. They have to be some of the best bookshelf speakers in their price range. If I had to stretch to criticize them for something, I would say that Perlsiten might have tried for a more attractive grille solution. That is just a nit-pick though, since the S4b grilles, unlike many other speaker grilles, do a good job in protecting the transducer diaphragms. 

Now let’s talk about their strengths. As with their bigger floor-standing brothers, the S4bs have a much wider dynamic range than almost any bookshelf speaker in their size class. If you have the power on tap, they can deliver dynamics that one might expect from tower speakers rather than bookshelf speakers. They also have a unique control over their vertical dispersion that can’t really be had by any other bookshelf speaker in its size and pricing. If you don’t want to have to worry about how your bookshelf speakers will react to floor and ceiling reflections, there aren’t any other bookshelf speakers in their class that can do what the S4bs can. As was previously mentioned, less vertical reflections might have soundstage benefits, and the S4b speakers served up a superlative soundstage indeed. Their frequency response is tremendously flat, and that, in addition to their controlled off-axis response, makes them a very tonally balanced and accurate speaker. They have a flatter frequency response than most studio monitors that I have measured, indeed, they could be used to mix and master sound in a studio capacity without any problems. If you are looking for a high-performing passive studio monitor, they are a great choice. They reproduce the incoming signal with little very coloration, in other words, they reveal the truth of the recording. Wide dynamic range, neutral response, and superb directivity control all add up to outstanding sound quality. 

In addition to the sound quality, the build quality is excellent- as it should be for the pricing. The S4bs have an exceptional solidity, and the “knock test” of rapping on the cabinet with knuckles is like tapping a boulder. It is a luxury item and has the appropriate feel of one. Along with the build quality is the styling; the S4bs look cool. Some people might be divided over their non-traditional drivers and layout, but it looks upscale and high-tech but without being overly stylized. As was mentioned before, the grilles don’t help their appearance, but I think nine times out of ten, they will be used without grilles. They are pricey, but they do look the role. 

At the beginning of this review, we asked whether the S4b speakers could deliver Perlisten’s signature technologies in a speaker of a much smaller form factor than their S7t flagship towers, and the answer is yes! The S4bs do not have the extension or dynamic range of the towers, but they are the “S7ts” among bookshelf speakers. What the S7ts do so well in their class of loudspeaker, the S4bs also do in theirs. The shame of it is that the S4b speakers will probably very often be used as a surround speaker in a Perlisten S-series system. If you ask me, that is a bit of a waste, and these speakers deserve better. Not much is ever asked of surround channels, and not much attention is ever given to surround channel sound, regardless of many popular claims to the contrary. To be honest, you could use a much lesser speaker in a surround channel role, and most people would never notice. But, if you want an absolutely premium, perfectly matched speakers with no compromises, they are what should be used in a Perlisten S-series system. However, if you want a first-class system that is based around stand-mount front left/right speakers, these can foot that bill with aplomb. Highly Recommended!