In this extended On Test article Julian tries the flagship of the Genelec The Ones series of co-axial monitors - the 8361A. Find out why he thinks these unusual monitors are the perfect example of a focused design.

Form should follow function and The Ones series of active monitors from Genelec are a perfect example of that. They take an old solution to an old problem and refine it. If your initial response to The Ones is “Why do they look so different?” Then this article will help. We look at the biggest of the range, the 8361A, look at its design and evaluate its performance. So taking things back to first principles - What is a speaker trying to achieve anyway?

Speakers should reproduce their input signal accurately. The 8361A achieves this using a three way point source design. That an ideal speaker should perform as a point source is consistent with this goal of accurate reproduction because traditional speaker designs with multiple drivers at multiple points in space inevitably have multiple path lengths to the listener’s ear - A source of distortion. How much this matters depends on the frequencies and distances involved and it is definitely possible to get excellent performance from a well designed 2 or 3 way monitor with multiple drivers but all other things being equal it is hard to see why a designer wouldn’t go with the option of having the entire frequency range originate from the same point in space. More on that point later.

The problem is that this is hard to do without introducing other compromises.

The Ideal Speaker

An ideal speaker should be full range and capable of reproducing everything from the deepest bass to the highest treble at any desired volume. Single drivers which are small and light enough to reproduce very high frequencies can’t reproduce bass frequencies loudly enough to be useful at distances greater than those found in headphones. To be effective at reasonable distances drivers have to become larger. As driver size increases so does weight and with it inertia, affecting high frequency reproduction, and that’s without getting into the effects on directivity which start to happen as wavelength is reduced below the diameter of the driver reproducing it! Directivity is an important factor here too as however hard it is to design a speaker with an accurate response across the full range of human hearing, it’s much harder to design one which can do that from all angles rather than just from directly in front.

Whether or not a speaker should sound the same from all angles is up for debate. However if the sound changes off-axis, ideally it should do so smoothly and evenly across all frequencies. If the room they are in is reflective then an accurate off-axis sound becomes very significant as if indirect sound differs dramatically from the direct sound then the sound at the listener’s position will become coloured, if the room is less reflective, then on-axis sound can dominate more but even so, inaccurate off-axis sound still affects the size of the sweet spot between the speakers. Given the challenges it is amazing that speakers work at all!

Introducing additional drivers solves many of these issues but of course introduces new ones, particularly the issue of different drivers at different points in space, but also the complexity of crossovers and matching the performance of multiple drivers. So is there a way to spread the load between multiple drivers so that reproduction can be flat, loud and full range while also keeping the drivers in the same point in space? There is and its been around a long time: The co-axial monitor - mounting the HF driver in the middle of the bass driver.

Co-Axial Monitors

The physics of this 2 way dual-concentric arrangement is seductive but it’s not without issues. In this arrangement, the cone of the bass/mid driver is also the waveguide of the coaxially mounted HF driver. At short wavelengths, small discontinuities in the typically smooth surface of a waveguide cause diffractions and re-radiation. A second issue is that of doppler shift causing modulation of the HF driver’s output. This doppler modulation is an interesting case as it is inherent to the design of a two-way dual concentric driver. If the waveguide of the HF driver is moving backwards and forwards as the tweeter’s output propagates across it, it will cause a pitch modulation. For example, if you were to play a 10K tone and a 40Hz tone simultaneously from a 2-way dual concentric driver the 10K tone would be heard to have a 40Hz vibrato applied to it! This issue becomes more pronounced as lower frequencies are reproduced.

There is an alternative approach where an HF driver is mounted in front of a bass driver, either on a separate baffle or with a rigidly mounted horn. The issue with this approach is that while it does reduce intermodulation, the discontinuities found at the edge of the baffle or horn cause edge diffractions which cause reflections off the bass driver.

This is where the wisdom of this three-way design of the 8361A becomes apparent, the doppler modulation caused by the deep bass issue can be avoided by using a 3-way design. With all the bass information below around 320Hz being handled by the twin 5”x10” oval bass drivers, the modulation issues can be solved. While it’s true that the midrange driver will still move and potentially modulate the HF, with the frequencies all being above 320Hz the issue is effectively gone.

The 8361 is the largest of the The Ones series. Compared to its siblings it is physically large (approx 23”x12”13”) and heavy (just over 30KGs) but in spite of its size being close to that of a large midfield monitor, its performance is closer to a main monitor. It has a short term max SPL of 118dB SPL and a frequency response of 36Hz - 20KHz (+/- 1.5dB) and 30Hz - 43KHz (-6dB). So it’s full range and it can go loud. But the important thing here is that it promises consistency, particularly in terms of where you are in your room and how your room will interact with it because it has been designed very specifically to have consistent temporal and directional characteristics. 

The DCW Waveguide

It’s easy to think of this monitor as a clever way to create a three way coaxial monitor  - which after all is exactly what it is. But after researching this speaker I’m struck as much by the care which has been taken to ensure consistent directivity across all three of the drivers. A consequence of this design is that the waveguide fills the entire front of the speaker and is shared by both the HF and midrange drivers. This waveguide is as big as those found on the largest main monitors and the bigger the waveguide the lower its effect extends. In this case the Directivity Control Waveguide extends down to 300Hz on the longest dimension. Once you appreciate that the spacing between and arrangement of the dual woofers hidden behind this waveguide is specifically chosen to match the directivity of the combined contribution of the HF and midrange drivers then the clarity of purpose behind this design starts to hit home.

This Waveguide is only as effective as it is because Genelec have taken a long hard look at previously existing designs and dealt with the biggest issues. A three way design is an effective solution to the doppler shift issues referenced earlier. Most concentric designs have sharp edges, or discontinuities between the edge of the HF driver and the cone of the midrange driver and between the surround of the midrange driver and the baffle. Genelec have created a driver assembly which uses an elastic membrane coating to smoothly bridge the gaps between the HF driver and the midrange driver. This system is called Minimum Diffraction Coaxial (MDC) Driver Technology . The hard dome tweeter common to all Genelec products is surrounded by a midrange cone which underneath the elastic coating is actually aluminium.

The dual bass drivers are out of sight but are 5”x10” oval, or as Genelec call them “racetrack”, planar drivers with a honeycomb construction. They are hidden behind a big, cast metal baffle with exit slots at the top and the bottom. Considering the crossover frequencies are 320Hz and 2.8KHz you might imagine that placing a bass driver which goes as high as that in a small cavity with a narrow exit might have issues with resonance. You would be right but Genelec have compensated for this in the design by including specifically designed cavities filled with absorbing material to alleviate this. These dual 5”x10” bass drivers have a similar surface area to a round 10” driver so there enough surface area to move the required air. When discussing The Ones series its definitely worth also mentioning their companion for truly full range performance, the advanced and rather exotic W371A SAM Woofer system which is a very clever device which is beyond the scope of this article but integrates perfectly with these monitors.

The 8361As are big enough to fill larger control rooms, there is enough level for them to be used at a distance of 5m but they are still particularly well suited to nearfield applications. The advantage of nearfield monitoring is that if you work close to your monitors, the direct sound dominates making the contribution of the reflected sound from the room less important, very useful for less than ideal spaces. As has already been mentioned, the way the off-axis sound of these monitors is so well matched between the drivers and across the spectrum makes them very well suited to less forgiving rooms but if you want to get really close, usually a larger monitor isn’t the best choice as the distances between the separate drivers becomes proportionally more significant the closer you get to the speaker. This issue doesn’t exist in a co-axial design and the 8361A is unusual in that is it a big monitor you can work very close to.

With so much which is unusual its easy to overlook the normal stuff. The cabinet are the cast aluminium style familiar to most Genelec products and have all the rounded edges of a sucked sweet. They are mounted on the rubber iso-pods common to the rest of the 8000 series products and the cabinets are a rear ported design. Genelec are always install-friendly and there are threaded mounting points on the rear along with dip switches for manual set up and dual network ports for detailed setup using GLM software to access the built in DSP for these SAM Smart Active Monitors. An analogue in accompanies an AES in and thru and power is via an IEC. It’s only when you go back to the front of these monitors that you are struck all over again by the unblinking cyclops of these monitors. A bit like HAL in 2001… The only other feature on the front panel apart from the Genelec logo is a green power/status LED which varies in colour to warn of overloads and standby status.

8361A In Use

For what are definitely pro monitors I decided to listen to them at Cube Recording, an excellent studio local to me In Cornwall. They have just commissioned a beautiful new third studio and the 8361As looked extremely at home between soffit mounted 3 way 1038As and the Avantone Mixcube “grot boxes”. Behind the (gorgeous) new SSL Origin the monitors were around 3 metres away from the listening position and as part of getting to know his new room studio owner Gareth Young had concluded that because of sight lines, whatever he settled on for monitoring in that room was going to have to be a portrait as opposed to a landscape model. Luckily with the 8361A they can be either. The listening was the part of the test I expected to be most straightforward but the experience is a good illustration of why it is so important to have a known reference when evaluating monitoring. The room is brand new, as in not quite finished new. The room is unfamiliar as are the main monitors which have been in storage for some time. Having a pair of second pair of “unknown” monitors doesn’t really help!

After a surprisingly quick calibration using the extremely useable GLM4 speaker calibration system we were ready to run some audio. I’ve used older versions of the GLM software before and found it effective but rather joyless. Software designed by engineers, for engineers wouldn’t be unfair. GLM4 is a much more polished affair. The new room definitely has some tuning yet to be completed, there’s a lot of bottom end in that room and some more trapping and tweaks to the monitors will be necessary. Bearing in mind that I was there before the room was finished does have to be kept in mind here. The soffit mounted big Genelecs sounded very bass heavy indeed and their delivery was light through the midrange too. By contrast the first play through with the 8361As sounded very mid forward indeed - Shouty and light through the bass. Something wasn’t right. The truth clearly lay somewhere between the scooped bassiness of the 1038As and the midrangeiness of the 8361As. I suggested running both pairs at once to get back to flat and I was only half joking!

Monitor Tweaks

Enlisting the help of the carpenter and his mate who was still on site (I said the room wasn’t quite finished) we tweaked the settings on the big 3 ways. Dipping the HF by 1dB and the bass by 4 got much closer to something which sounded subjectively flat. A few minutes running pink noise through them and running SMAART confirmed that while they were still a little enthusiastic below 80Hz things were much improved. I’m at a loss to explain how we got something as simple as calibrating a pair of SAM monitors using the GLM measurement kit and the GLM 4 software wrong but a second pass restored the bass we had managed to completely eliminate on the first pass. The software had correctly identified a couple of significant issues at the bottom end, including the generous bass performance of the room but the first profile was just plain wrong. I suspect user error.

After this second calibration and having manually balanced the response of the mains we were in the territory of useable monitoring. The 1038As are old style “big Genelecs”. Though far from the biggest of that range they have the easy, room-filling character of soffit mounted mains but while they sounded really nice, they did feel like they were lacking some detail through the midrange (plenty of client-pleasing bass though, maybe leave that?). While their modern equivalent the 1238A SAM can be tuned using GLM4 this isn’t an option here so a third party solution might be in order. The 8361As were making a lot more sense now and I could hear what it was that had prompted several people whose opinions I trust to make very positive noises about these monitors.

The overwhelming impression is one of detail. I actually find it quite reassuring when I hear some good quality monitors and I find myself thinking that I don’t like the sound of them. I first experienced this when working in a mastering studio on some big ATC SCM110s, a nice setup. It’s sobering to hear your stuff sounding that rough. Check your test tracks playlist and they sound a bit ropey too. This is a good thing but always a shock. Really good monitors tell it like it is. That’s what they are for. The 8361As don’t flatter, nor should they and while they did sound pretty mid-forward, that was in comparison to some monitors which in truth were probably sounding a little scooped. Keeping my earlier comment about how the combination of a new room and two new set of monitors can leave you without a reference you can probably see how this was panning out.

With the setup now much better we settled down to some listening and a little experimental mixing. My regular test tracks were dusted off and beyond the extreme detail, particularly through the midrange, I was also struck by just how clearly I was hearing reverb tails and rather oddly, I still can’t make sense of this, I was hearing pitch modulation on instruments much more clearly. No idea how that was happening but it was. The other big impression I was left with after spending some time with these monitors is how well they perform off axis, both horizontally and vertically I found them extremely tolerant of movement. If you find yourself instinctively crouching to put your ears vertically on axis when standing in front of nearfields you’ll find that you don’t really need to. And because of the work which has been done to control the directivity so that any change is even and smooth the sweet spot is huge and imaging is pin sharp.

Return Visit

A single listening session isn’t enough, particularly one which ended up being as confusing as our first was so I returned to Cube a couple of days later. Gareth had exclusively been using the 8361As the previous day on a mix and told me he had found the experience very positive. I sat down for a return visit with fresh ears and found them better than I remembered. My initial impressions of detail, resolution, distinct stereo imaging and a wide sweet spot held true and my concerns that they were shouty through the upper mids and lacking bass were unfounded. They probably are a little hot through the upper mids compared to many monitors but I’m perfectly happy to believe that this is a sign that many monitors are a little shy through that crossover region. Another test I ran was for consistency across a range of playback levels. As long as enough headroom is available I don’t really care about how loud monitors can go. As long as you can run an uncompressed kick drum at a good level without bothering the limiters I’m happy but performance at the other end of the dynamic range was where these monitors really shone. I was too far away from them to pick up even the slightest hint of hiss from the monitors but I was struck by exactly how quietly I could monitor without losing important information. Turn them down and they sound the same but quieter. That should be the case for any monitor but in my experience it often isn’t.

Conclusion

So what do I think of the 8361A? I think they are such a coherent design and so well executed that its hard to find any reason to criticise them. They are every bit as efficient in their intended goal as you’d expect a flagship Genelec monitor to be. There’s something about Genelec monitors which is both reassuring but also a little conservative. Of course they sound great, they are Genelec. No drama, they do what they are designed to do excellently. If that sounds like a criticism then I’m not sure why that should be. Full disclosure, I’ve been a Genelec user for 20 years!