Cabasse Sloop 500

Product: Cabasse Sloop 500 loudspeaker
Manufacturer: Cabasse - France
Approx. price: 2,150 US$/2,150 Euro (ask your dealer for details)

Cabasse are French. They're based in Brest and have been making speakers for nearly 50 years. During this time they've remained primarily a family concern despite becoming the second biggest speaker manufacturer in France, sort of an audio equivalent to Peugeot :-) At this point it's worth pausing to think of other big names in the audio world that have a similar record - no nor can I...

Over all those years Cabasse have maintained a quality image, with unbeaten product support, rather as Quad has done in Britain. All speakers carry a lifetime guarantee, and that means your lifetime... On a recent visit to the research base in Brest I was shown the servicing department where veneer from the 1950's, and drive units from the same era nestle against the latest triple concentrics. Yes - triple concentric. Cabasse may be traditional, but their commitment to pushing back the boundaries of the dynamic loudspeaker, are second to none.

Over the last few months I've been using one of their cheaper floorstanders, the Farella 401, and very nice they are too, but what I really wanted to try was one of their concentric driver speakers, just to see what their research department could come up with when they put their mind to it. So a couple of weeks ago Christophe Cabasse turned up for a morning and left behind a pair of their new Sloop 500's fitted with the BC12 Dual concentric tweeter/upper midrange unit- yummy!

Construction

Technology

Now the unconventional. Firstly the bass/mid driver. This is an 8 inch unit, with a very substantial alloy chassis and hefty ferrite magnet. It's real claim to fame is the cone material. Where others have gone for aerogel, aluminium or carbon fibre in search of a hi-tech solution to making the ideal light stiff speaker cone, Cabasse have taken a radically different approach. They are made from a copolymer foam. In the raw state this comes as a sheet looking rather like thin expanded polystyrene. It is however much harder and stiffer. This sheet is then pressed between two heated cones, each with a complex profile. The heat seals the surface and compacts it so it looses its air pockets, becoming solid and hard. The core remains alveolar - the result being very like the structure of a birds bone, very stiff and very light. By varying the shape of the two moulding cones the profile and thickness of the speaker cone can be tightly controlled. This process has to be done individually and takes 15 minutes per cone. Each is then weighed and if it is 0.5 gram over spec it is discarded. For the 8 inch driver cone I saw the target weight was 14.5 grams. To put that into perspective, the weight of a Bandor 6 inch spun aluminium cone - claimed to be lightweight - is 24 grams, however that of a Lowther is 6.5 grms...

Though to the casual glance the Sloop appears to be a two-way, it is in fact a three way. What appears to be an odd looking tweeter is a dual concentric 'super tweeter' with a frequency response rolled off at crossover at 1200 Hz. This has two advantages. Firstly the Bass/mid driver can be optomised for a fairly narrow bandwidth compared to a two way - secondly the BC12 Dual concentric tweeter/upper midrange unit acts as a point source in the range of hearing where we are most sensitive to direction and phase, all important for image depth...

Here I think a little discussion on the virtues of the 'point source' would be helpful. Stereo works by having two channel sound, each channel being different. By dint of different levels and phase, an illusion of not only left to right, but depth and height imagery can be portrayed. But if each stereo channel is split into high and low frequencies, which are then emitted from different points, the sound levels and phase will alter depending on where the listener sits. As an extreme example if you had a floor stander with the tweeter at the top and the bass driver at the bottom there could easily be a metre between the two. If you sit low on a chair the woofer would be closest to you, stand up and the tweeter might be 50 cms closer than the woofer. You can imagine what that would do to the tonal balance let alone things like imagery! This is why manufacturers pack mid and tweeters as close as possible to reduce it's effect. They will also tune the crossover and driver position so that they are in phase when listened to from a certain position. However though this may give a 'hot spot' of good imaging the illusion will be destroyed if the listener moves.

The answer is of course obvious, make all the frequencies come from one place, i.e. a 'point source'. There's nothing new in this, full range drivers such as Lowthers have done this for years, but the most common modern solution is to put the tweeter at the centre of the mid/bass cone. Tannoy did it 50 years ago with their pressure loaded horn tweeter, and KEF and Seas make drivers where a small dome tweeter nestles at the centre of a conventional cone.

Cabasse have taken a radically different approach where a dome tweeter sits in the centre and round it as a concentric ring sits the upper mid driver. In their three-way concentric there is a third ring which handles upper bass taking the concept still further. The reason for this departure is that by making the ring have a domed, rather than cone profile, the dispersal characteristics are far more evenly matched. A cone has a completely different pattern so off-axis listening will alter the tonal balance of the speaker, one of the reasons for going the 'point source' route in the first place. It also allows for the source to be a point in space, most dual concentrics have acoustic centres in slightly different positions front to back, not so this driver. In the BC12 driver the inner dome is a plastic laminate and the outer ring the same copolymer as the bass driver.

One last thing before the listening session. These speakers, like all from Cabasse are very efficient. At a time when most speakers are in the mid to high 80's the Sloop manage 94.5 Dbl. This is getting close to horn territory. True they are rated at the continental 4 ohm standard, but my Audions had no problems with them on the 8 ohm tap, though I often used the 4 ohm simply to give the volume control more travel! To put this bluntly, my 30 watt monoblocks wasted most of their watts, I'd suggest that in a normal room 10 watts would give good party levels. The one proviso is that like all ported speakers the Sloops have a double humped impedance curve that may be upsetting, but certainly my own amps had no problems.

Listening to the Sloop

Now a month has gone past and as the speakers have broken in I think I've worked out what they are all about... As I said at the outset these came in to replace a pair of Cabasse's own Farella 401's. I'd liked these but they did have their own character as with all speakers. That was a forward well-projected midrange, good top end and a tuneful but dry bass quality. The Sloops continued this family sound, and if you only had ten seconds to hear each you might find them hard to tell apart. This I consider a good thing - If a manufacturer thinks music should be presented in a certain way, all their speakers should share a 'voice'. If a two speakers from the same manufacturer sound completely different you have to doubt either their design consistency or their commitment...

But after 10 seconds the differences become immediately apparent. The Farella's have a slight grainy quality in the treble that I'd not noticed until they were replaced, and though they image well for a big bluff box the Sloops really showed their superiority very convincingly. Take the first track on Chesky's sampler - "Sex Without Bodies" by Dave's True Story. Here the female vocal clearly stood out in front of the plane of the speakers with the percussion well back in the sound stage (in a drum booth by the sound of it...). Walking from the centre of the room, parallel to the plane of the speakers, to right in front of the left-hand speaker had unusual results. Generally doing this, even with speakers that image well, makes the sound collapse towards the left-hand speaker. Almost all sound seems to come from that one side and the front back imagery compresses to the plane of the speaker. With the Sloops the front back distance remained constant though of course it now appeared as if the singer was directly in front of the speaker and the drummer behind. It was a very impressive demonstration of the dual concentric principle. Also because of the ideal dispersion characteristics the Sloops could be pointed straight up the room without problems, a minor cosmetic point but significant nevertheless.

As references I had my own two pairs of home-made speaker to hand, an 11 ltr pair of Morel based, ported standmounts and a hefty pair of metal coned transmission lines, both with driver line-ups that are seen in commercial speakers at around 1000 pounds sterling or more. The Morel based speakers are pretty good at imaging, being small and with the midbass and tweeter drivers actually touching each other, but those big floorstanding Cabasses really showed them how it was done. The transmission lines just go soooooo low, flat to 40 hz and with window rattling output below, but the Sloops made them sound heavy and leaden, smothering fine detail. However the Sloops did lack their sheer slam. Take the opening of Nirvana's 'Nevermind' where the massive drumkit explodes from behind the speakers. The Sloops were so fast! Whack! Whack! Whack! Enough to make you blink, but the TL's were Wham! Wham! Wham! Enough to make you dive for cover. Now we're not talking musical subtleties here, or perhaps truthfullness, but certainly that massive impact was lacking and I missed it badly. The same with Verdi's 'Dies Irae' where the basses in the choir (much better placed in the case of the Sloops) lacked the weight and presence to make you think the walls were caving in. Make no mistake, what bass there was was tuneful and fast with no 'one note' effect.

Much of this can be explained by the frequency response curve of the Sloops. Cabasse take great pride in their speakers measuring well, and the Sloops are very flat from 100 to 20,000Hz. Below 100 Hz they begin a gentle roll off. At around 80 Hz, where most manufacturers engineer a bass hump to give warmth and bass slam the Sloops are slightly down. My tiny Morel based speakers had more warmth and the illusion of bass weight due to the same port reinforcement at around 80 Hz. If you design a ported speaker with this kind of hump the response then falls off rapidly, whereas the Sloops have a gentle slope not unlike a sealed box. The result being that they do produce very deep bass, bass you can feel. There is no denying though that the dryness in the bass will be the one thing that puts some people off. At first it did me too, but after a few days I became used to it and the other speakers began to sound artificial and 'tailored'. It also means that they are less likely to upset 'boomy' rooms and that they are happy being placed close to a rear wall. The Farella's shared this dry quality and yet I was not too troubled when they were taken away - I felt my own speakers were certainly in the same ball park though very different - the Sloops were a different matter entirely...

So apart from the imaging (which to be frank isn't my personal no.1 priority), why did I become so enamoured with the Sloops? I suppose it could be summed up with my experiences with two rather unusual discs. For a while now I've used the CD of Dave Brubeck's 'Time Out' as a reference. It's a typical top quality late 50's jazz recording. Simple, sparse, pin sharp and not 'buggered about with' in the studio. It's the sort of thing that makes you wonder what the music industry has been playing at for the last forty years... OK so I played it on the Sloops, yup, very nice, perfect imaging etc etc. I then went out to a car boot sale and picked up the vinyl version for a quid. Completely knackered, mucky and scratched I washed it using the (ESSENTIAL!) record cleaner and put it on for a laugh. The expected hail of clicks was followed by music. When testing stuff I'm always leaping up and down and changing things, but here I was riveted to my chair for the whole side. It was awesome! Take the first track 'Blue Rondo al la Turk'. Joe Morello plays various bits of tin in the background all though. With the CD that’s just what it sounds like. On the Gyrodec you could see what he was hitting, see the way he hit them, no doubt a drummer could instantly tell exactly what each instrument (bells, cymbals, hi-hats etc) was and probably who made them - it was that good. The CD just wasn't in the same ballpark. In case you think I've lost the plot here the point is that my speakers didn't show this, only the Sloops allowed the attack and decay of each strike to come across - wonderful...

The second disc was a CD made by a friend of mine John McInyre with his band Jarka. It's lovely folk blues, mostly acoustic and like many of these short run recordings it was done in a day. Thus it has a live feel. You see - John is a very good friend. I know his spoken and singing voice as well as my own. I know where the recording was made, I've been there many times, I know what it's like. Last night John and his band were in my room, no question. Previously the disc had always sounded very nice on my own speakers, and some people would prefer their presentation to the Sloops - but I know the truth...

Conclusions