Genelec 8351B Review

Genelec 8351B Review

"The Ones and Only"

The world market leader in studio monitors has always fascinated me. At LowBeats I entered the Finnish world of sound with the Genelec One (see test)  and recently I was fascinated by the 6040R  . And yet when you look at the Finns' portfolio, the series called "The Ones" stands out from a technical point of view, because they are technically the most advanced coaxial loudspeakers. The second largest model in the series, the Genelec 8351B, has been in my listening room for a few weeks - and hopefully for longer.

In principle, the point sound source is the declared optimum for the music reproduction of sound recordings in living or listening rooms and a coaxial loudspeaker is already close to it. Why? Here's a brief digression: In comparison to multi-way speakers with spatially separate sound sources from woofers, mid-range speakers and tweeters, the sound generation with the coax happens at one "point" for all the chassis involved - ideally at the same time. This type of driver thus delivers a radially symmetrical radiation and consequently all early reflections show a frequency curve similar to the frequency response measured on axis - as long as the bundling is not too strong and the room acoustics allow it.

Since we perceive the sound of a box not only through the direct sound, but also through all reflections in the room, this balanced property contributes to the good sound. The classic multi-way speakers, on the other hand, show strong vertical interference, i.e. cancellations and increases in the frequency response, and therefore very different transfer functions via the room reflections to the listening position, due to the different locations of sound generation depending on the room angle. Here the reflections have a different “sound”. "Constant directivity" is the keyword. A measure of good constant directivity is the measurement of the sound power, so to speak a frequency response that represents an average of all frequency responses measured in solid angles.

In recent years, there has been a trend towards improving this "constant directivity" in traditional multi-way loudspeakers by means of a short sound path in front of the tweeter. This works quite well, but the problem of interference in the transition area between the spatially separated drivers remains.

There aren't many designers/manufacturers building speakers with coaxial drivers. Perhaps because they are more expensive and difficult to manufacture. Above all, this requires a certain level of vertical integration in the company if you want to do it right. KEF, for example, is committed to the coax and has continued to improve the principle over the years. As is so often the case, the devil is in the detail.

A major difficulty is not to place any stumbling blocks in the way of the gentle sound waves of the tweeter. Because every small edge shows irregularities in the frequency response, especially when measured off-axis. The oscillating mid-range driver also represents a kind of modulating baffle for the tweeter. Furthermore, it must be ensured that the contour of the mid-range driver - i.e. the shape of the membrane - has sufficient stability on the one hand and is not too funnel-shaped on the other hand, which in turn greatly increases the bundling of the tweeter would. As you can see, there are some conflicting requirements here, which makes the design very complex.

Genelec 8351B: The Concept

Genelec has dedicated itself to all these problem areas and perfected them in detail.

The picture is worth a thousand words here: The beads of the 25 millimeter dome and the 13 mm midrange driver are flat, which shows a seamless contour with a continuation in the baffle shape - perfect.

Due to the use of the mid-range driver down to just 320 Hertz and the associated small stroke, the tweeter does not “see” any significant modulating baffle.

The highlight of the compact 8351B is the arrangement of two woofers behind the baffle. Together, the two oval woofer cones result in an area comparable to that of a 25 bass. The radiation of the deep tones is guaranteed by slots above and below the baffle. This expands the point sound source to the low-frequency range, and even the constant directivity continues downwards within certain limits.

Thanks to cast aluminum as the housing material, this optimized shape can only be achieved in the first place. In addition, despite the low wall thickness, the housing is very rigid and the gross volume is kept low at the same time.

As usual with Genelec, the 8351B is also active. This means that each driver has its own power amplifier behind it and the division of the work areas is taken over by a digital crossover. A full 250 watts of Class D are available for the bass drivers and 150 watts of Class D for the midrange and tweeters. The crossover frequencies are 320 and 2,800 Hertz. A pair of 8351Bs achieves an enormous peak level of 123 dB for a short time. 32 hertz and 43 kilohertz are the cut-off frequencies. So much for the prospectus data for the sake of completeness.

The speakers, which weigh a little over 14 kilograms, are placed on so-called Iso-Pods. These are soft rubber-like feet that decouple the speaker from the ground and also allow the Genelec to be aligned vertically. The feet can also be attached to the side, so that the 8351b can be operated horizontally without any tonal restrictions - see symmetrical radiation characteristics above. The Iso-Pod fits both on the sides and below the box - thanks to the almost point-symmetrical radiation of the coax chassis, no significant differences in sound are to be expected. Cool solved. There are also countless stands and adapters for wall or ceiling mounting as accessories for all conceivable installation variants. Not a matter of course for such professional tools:

Once measured, the correction curves can be stored in the loudspeakers.

Genelec 8351B in practice

When it comes to the listening room and the set-up, Genelec or the 8351B offers another treat: "SAM" stands for Smart Active Monitor. And that means nothing more than the possibility of measuring the loudspeakers to the room or the listening position. The optionally available GLM set can also be purchased (390 euros). The set includes all the necessary cables, the GLM adapter (GLM = Genelec Loudspeaker Manager) and a measurement microphone.

In order to establish contact with the loudspeakers, the network cables are connected from one box to the other and on to the GLM adapter. After downloading the free GLM software and connecting the computer to the adapter via a USB cable and setting up the microphone at ear level in the listening position, the calibration can begin.

In the software, you first use drag and drop to define which of the boxes is on the left and which is on the right. If any Genelec subwoofers are recognized by the software, they can also be placed in the virtual room. You can choose between one or more measurement positions around the listening position. If you choose the latter option, the degree of equalization is less extreme due to the averaging of the measurements, which is usually preferable.

Basically, I don't choose the isosceles triangle from the listening to the speaker positions to be very extensive in order to keep the ratio of direct to reflected sound high and thus reduce the room influence in the listening test. The 8351B stood on solid, sand-filled stands and, thanks to Iso-Pods, were aligned at microphone and ear level. If you start the measurement, after a few seconds a diagram appears with the measured transfer function, the correction curve calculated by the software and the corrected transfer function. After clicking on "Confirm", the adjustments can finally be saved in the loudspeakers, so that you are independent of the computer and the GLM software.

However, if you want to switch between uncorrected and corrected in the hearing check, the software must be active. If you find that there is still a need for action here and there, you can use the "Sound Character Profiler" to fine-tune it with additional shelving filters, for example, or vary the existing correction filters in their characteristics

As a streaming source I use the Roon Nucleus or a Tidal account. The digital audio data finally finds its way via a Mutec MC3+USB to the digital input of an 8351B. The second loudspeaker receives the data via a digital audio line. I also tried the analogue variant, D/A converted via a preamplifier and then analogue to the Genelecs. To anticipate: I didn't hear any significant difference.

Experience has shown that a degree of directivity that is as constant as possible, or at least constantly increasing with the frequency, is responsible for good sound. Ideally, the dark green area – i.e. the angular range in which the sound pressure deviates from the axially measured frequency response by no more than three decibels – should run as a straight “tube” from left to right. In other words, the speaker would concentrate equally well over the entire frequency range and radiate equally wide. Due to the placement of the two woofers, a slight bundling up to about 200 Hertz can be seen vertically.

So let's get down to business: Diagram 1 shows the measurement at the listening position, right box (red), the calculated equalization (blue) via GLM and the frequency response (green) after equalization. Even in a listening room with unfavorably distributed room modes (see red curve below 150 Hertz), the automatic calibration shows a well-dosed correction. The resonance peaks are mainly contained, sound pressure sinks are only slightly increased for a reason - see correction curve blue. Background: The dips in the bass range are sound pressure minima due to the position in the room. If you try to fill up these minima, the sound pressure in this position remains largely unchanged, but at other points in the room you would measure and hear significant level increases and the drivers would quickly be overwhelmed.

hearing test

First, I check whether everything is connected with the correct polarity – which is not necessary with the active 8351B, however. So are the singers standing correctly in the middle or are they floating diffusely in the room? Then the tonality in the important midrange is up for assessment. Do voices sound nasal or grumpy in the lower range? Are they more prominent or perceptible further back?

"Big in Japan" by Ane Brun is always good for a first check. Ad hoc it is noticeable how precise voice and instruments are placed. If the recordings are good enough, this should continue in the further listening test. The S-sounds are slightly emphasized, the e-guitar has shine and bite - I thought maybe a bit too much. Finally, the 8351B was angled relatively strongly towards the listening position. So I rotated the speakers a few degrees further out. Lo and behold, now the tonality was completely balanced. I was immediately interested in how the Genelec sounds calibrated. The singer takes a step forward and the stage is presented even more tidily. Above all, however, what is presented sounds audibly more structured in the bass, adjusted for mode.

Take the Fairfield Four's "The Bones," for example. Without correction, the depth gradation is perhaps a little better. The comparison with and without correction brought mixed feelings: In Ain't No Sunshine with Buddy Guy and Tracy Chapman, for example, the bass and drums with correction seemed much more differentiable, but at the same time somehow slowed down. The beautifully captured voice of Ariana Savalas on "One Man Show" sounds well present and clear with equalization, but also a bit more two-dimensional, without being a little more plastic, but with a slight emphasis in the middle voice range. In this context, I find it interesting that the sometimes strong emphasis in the bass range is subjectively not necessarily found to be immensely annoying.

Whether you use the correction function or not depends on how good your listening room acoustics are and how long you take the time to adjust the boxes to find the best listening position. Because one thing is for sure: the Genelec 8351B in itself is a well-tuned speaker, but unfortunately the room acoustics determine what comes out of it. Poor listening room acoustics degrade even the best speaker. A mode correction with steep-edged filters is always only the second-best solution.

Still, after listening to it for a while, I ended up liking the corrected rendition better overall. In any case, with correction, for example in Brad Mehldau and "Henri's Lament", the bass can be better differentiated tone by tone and there is no pressure on the ears as soon as a bass mode is stimulated.

Also very nice is Otis Taylor's "Resurrection Blues" — with the guitar clearly outlined slightly left of center and Otis' husky voice right in the middle. Also Hans Theessink with St. James Infirmary conveys a phenomenal plasticity with the voice again clearly in the middle. Anyone who has heard Brian Bromberg's "Blue Bossa" through the Genelec 8351B should be completely convinced of the qualities of the Finnish speakers - I have never heard any other speaker that reproduces the plucking of the acoustic bass and the after-vibration of the wooden body so realistically. Terrific!

The ability of the Genelec exceptional monitor to present any acoustics of the recording rooms is very cool. During the first few seconds of Demian Dorelli's "Pink Moon" I really jumped because I thought someone was walking through my listening room - the footsteps of the leather soles on the floorboards sounded so real. The superbly “captured” piano on this recording also left no doubt about it: excellent loudspeakers are playing here. Finally, Dominique Fils-Aime' with "Birds" was a must for me. At that time, bass, percussion and voice were optimally pressed into digital data here by the sound engineer. It's amazing how casual and at the same time high resolution the music is presented.

Speaking of bass: what about the depth and in relation to the level stability? There is nothing to complain about in terms of depth. A lower limit frequency of around 30 Hertz is a statement, especially for a speaker of this size. In a monitoring situation like in my case, with a side length of about two meters of the listening triangle - i.e. tending to be more of a near-field situation - there were never any restrictions in terms of level stability, let alone intervention of the limiter. A subwoofer is recommended for those who want to enjoy the lowest-frequency music at excessive levels in large rooms and at large listening distances. Of course, there are suitable components from Genelec and, of course, technically sophisticated bassists that can be easily integrated thanks to GLM. I only think of the W371A,

Genelec 8351B: the conclusion

What else remains to be said: The Genelec was conceived for the studio, but it also makes perfect sense for the audiophile music listener. In any case, I haven't heard any moving music in my listening room. The 8351B achieves this through a superior design and a multitude of adjustment options. Or to put it another way: The Ones – set the note one and enjoy. In any case, I will have to talk to the German Genelec distributor about whether the monitors can remain in the listening room as a reference for a while longer...

Genelec 8351B Specifications.

Genelec 8351B

Technical concept: Active box with clever coax

Power of the power amplifiers: 1 x 250 watts, 2 x 150 watts

Particularities: 2 x oval basses (21.5 x 10.0 cm)

Particularities: location filter

Inputs analog/digital:

Analog In: 1x XLR, 1x XLR; Digital In: 1x XLR Out digital, 2x RJ45

Colors:

Black + White

Dimensions (H x W x D): 18" x 11" x 11"

Weight: 14.3 kilos