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The Celestion SL-600, first of the luxury compact monitors

Earlier, I wrote about the ProAc Tablette mini-monitor. This was a tiny speaker that used generally tried and true technology to produce a fine miniature loudspeaker. A bit later, Celestion came up with a completely different approach to the small monitor, the SL-600. The difference was the technology that was brought to bear. The acquisition of Laser Interferometry equipment allowed Celestion’s designers to examine the action of drivers and what was discovered was that most speaker drivers operated in “break-up mode” through significant parts of their ranges where different parts of the diaphragm were moving independently rather the ideal of “pistonic action”, that is, the driver moving as one piece.

This resulted in development of all new drivers for the SL-600 (and its little brother, the SL-6). The woofer looked fairly conventional, but it did benefit from the new measurement technology. But the really obvious thing was the tweeter. It sported a copper (!) dome and did indeed act much more pistonic than typical domes of the day, at least up to about 19 Khz, where its fundamental resonance resulted in a large peak. In practice, a notch filter was introduced into the crossover to remove this. The copper dome also had another effect. Since it was relatively heavy, it lowered the sensitivity of the tweeter. Enough that, had the woofer sensitivity been lowered to match, the system would have been almost impractically inefficient. So what was finally accepted was a tweeter that was around 2 db down from the level of the woofer. Keep this in mind for later.

For the premium SL-600, there were more tricks up Celestion’s sleeve, mainly involving the cabinet. It was always known that resonances in speaker cabinets had an effect on the sound, but around this time speaker designers started to seriously attack this problem. Within a few years, the Wilson WATT would come out which used methacrylic material to deaden the cabinets and cabinets generally became thicker, heavier and better braced.

Well, Celestion took a different tack. Unlike the SL-6, which employed a more normal MDF cabinet, they decided to design a LIGHTER yet still stiff cabinet using a metal honeycomb material called Aerolam, commonly used in airplanes. The idea was that the material would not store and re-release energy and what resonance they had would be high enough in frequency to be out of the most critical range. They also employed mounting plates to attach the drivers to the front baffle, further stiffening the cabinet. These plates were serrated vertically with small channels to break up sound diffusion off their surface. All in all, it must be said that they started this design off with a clean sheet of paper. So how does this speaker sound today and how successful was its design in retrospect?

One thing the SL-600 was always celebrated for was its disappearing act and disappear it does. The image is vertically challenged as are most small speakers (though not as much as the original ProAc Tablettes), but, beyond that, the images are quite holographic. Mainly, I suspect, because the boxes radiate almost no sound from themselves to confuse the imaging issue. These cabinets also do not have serious resonances that color the sound of the drivers in tonal terms, either. And this results in a clarity through the midrange that is good even by current standards.

But there is another factor, controversial at the time, less so today, that factors into the sound of this speaker. That speakers should not measure dead flat in the treble is a commonly held view today, but back in the ’80’s this was not so much the case. Remember the less sensitive tweeter we talked about earlier? Well this resulted in a response tilted down somewhat from the mids into the treble. So you had a speaker that sounded less bright and more velvety than the norm of the day due to this tilt (and truthfully, by the lack of break-up artifacts in the Celestion tweeter that most tweeters added that contributed spurious treble energy to most conventional speakers). Many listeners of the day rejected the SL-600 for this characteristic, feeling they were slow and dark. Ironically, that “problem” with the tweeter resulted in a speaker more in keeping (in my view) with a natural tonal balance on the largest variety of recordings.

Of course, there are problems here, the worst of which involves the bass/midbass. It’s extended enough for the cabinet size, but sounds a bit vague, as though the woofer runs out of low-distortion steam as you go into the mid-bass. This has the effect of making a discontinuity in the sound, instruments whose fundamentals are higher sound very clear while the lower voiced instruments can sound less so. This is not a world-shattering effect, but it’s there and the louder you play the SL-600, the more this effect can be noted.

Due to the small size of the drivers and the cabinet, dynamics are good rather than great. Here it’s hard to single out the SL-600, most small speakers suffer from this. But some newer designs its size do somewhat better in this area. There is also a bit of a sense of hollowness to the sound, I suspect from the residual cabinet resonances. This is not a severe effect, fortunately. And there is not quite the silken beauty of the best of today’s drivers here.

The intent of the SL-600 at the time was a no-holds-barred assault on the ideal small monitor. It retailed for a high price for its time, but, especially in the context of the mid ’80’s, it was pretty much a successful design. And if you aren’t too troubled by its modest failings, this is still excellent performance in many ways for a small monitor speaker even by today’s standards. Of course, if you are willing to go for the throat, you can certainly outdo the SL-600, but not for near their price on the current used market…


The littlest Pro Ac, the original Tablette or how much bass is enough?

We take for granted the number and variety of small monitors available in the hi-end market today, but it was not always so. Back in “The Day”, small speakers also had to be cheap (who would pay big bucks for a small speaker, the logic went), so you generally didn’t get well-built cabinets or premium drivers and the speakers weren’t usually very good. Unless…

You looked into the pro market at the BBC-designed LS3/5A, which was designed to be, as the Brits’ would say, a “high quality miniature loudspeaker”. It was also designed for what we would now call near field monitoring, but worked OK as a home speaker and increasingly found favor in the hi-end home audio market.

Eventually, the home audio oriented speaker companies noticed this emerging market and started to develop products to cater to it. The ProAc Tablette came along at the right time (early ’80’s) and happened to catch the eye (ear?) of The Absolute Sound magazine and its legendary editor Harry Pearson. Harry gave it a quite complimentary review and ProAc, which previously had only a minimal presence in the US market, was off and running.

After the reviews came out, I made it my business to hear them for myself. I worked in NYC at the time and took the train to the nearest ProAc dealer, a now long gone store in New Brunswick, N.J. Sure enough, quite a nice sound came out of those diminutive boxes. I wanted a pair, but never bought them for reasons lost in the mists of time. A few years ago, a pair of the originals showed up on Audiogon for a reasonable price so I righted that wrong from long ago.

The reason to talk about this speaker (besides its good sound) is its status as one of the first and best of these early mini-monitors (as they came to be called). It can be fairly said that the BBC monitor and the Tablette opened up this market to the mainstream. The premise was that they offered competitively hi-end sound for relatively low-end dollars, assuming you were willing to give up bass and high output levels.

Today, like back in 1981, it’s still amazing to hear what comes out of such small boxes, especially in terms of dynamics and loudness in a reasonably sized room. Obviously, they will not out do larger speakers in some ways, but to me they play just loud enough and have just enough bass to be fairly satisfying on these fronts.

The glory here, as you would hope, is the midrange. Even now, it does a fine job, better than many modestly priced speakers on the market today. As with most small monitors, the imaging is fairly precise, but limited in size and height. The treble is a bit accentuated, but not so much as to scream, at least when played at reasonable playback levels. The drivers show their age a bit, being a bit more rough and ready than the better drivers today. But you don’t get that quality of drivers in modestly priced speakers and you can pick up a pair of used Tablettes for around $300. This math looks good to me.

With mini monitors, bass is always the elephant in the room. Here is where their enclosure size works against the Tabs. Listening to the Decca/Fruhbeck de Burgos Albeniz Suite Espanola, the music is accented by tympani strikes. On a larger speaker (or live music) the tymp powerfully cuts through the orchestra, on the ProAc it sits back as just a component of the orchestra. But it’s there at least, and you can understand the composer’s intent. The lowest open string on the Bass is around 40 Hz and the lowest on the Cello is around 60 Hz, so the ProAc’s in a sympathetic room can at least begin to reproduce these instruments (without really capturing them in full). But it must be said that, bottom line, their approximately 1/3 cubic foot enclosure is just not large enough to get convincingly to the lowest string of the Bass.

A speaker with an enclosure volume of  around 1 cubic foot (3 times as much) is large enough to reasonably get down to that magic 40 Hz figure in room. Again, not to say that response even lower than 40 Hz wouldn’t be desirable, but it’s less of a limitation since that’s mostly the province of the last handful of pipe organ pedals, synthesized electronic music and movie soundtrack effects and the like that are not generally of major musical significance, for classical music especially.

But then again, having the frequencies below 40 Hz also helps bring out concert hall room ambience (which certainly does help create the illusion of a live music venue) and can add to the sense of power on rock music, so they can’t be ignored completely. The problem is, as you descend below 40hz, reproducing this deep bass well becomes expensive, requiring large speakers, large rooms and powerful amplifiers. Sometimes I ask myself if it isn’t more trouble than it’s payoff. But I used to own Infinity IRS V’s, so I guess my arm can be twisted on this point.

Oh well, enough bass theorizing, back to the Tablettes. You can hear why they made waves, both positive and not so positive all those years ago. I do believe that the original Tablette sounds better than the sum of its parts, an example of the magic a wily speaker designer can conjure up.

So I still like them, and with their tiny size it’s no problem to store them when not in use. I guess, truth be told, as my only speaker their limitations would be just too, errr… limiting. Even ProAc eventually increased the size of the Tablettes in their later iterations. Perhaps a comparison between the original and the current Tablette will be possible at some point.

At the end of the day, there are many larger speakers I prefer less despite their low-frequency advantages. It turns out that what the original Tabs do well is not such an easy act to follow.

The Magnepan 3.7 and aspects of reality

It’s almost embarrassing to talk about the basic concepts of the Magnepan line. They have been around for so long (early ’70’s) and have stayed so true to their original concept that it seems almost impossible that anyone remotely interested in Quality Audio isn’t already aware of the company and their products. In fact, if you saw a picture of their original MG-3’s and then pictures of the succeeding models, you would suspect that more has stayed the same than has changed, and there is some truth to that.

Still, there have been incremental improvements since the original MG-3’s, intended to address the original designs perceived weaknesses. The biggest problems were in the area of low-level resolution and detail. One had to play the MG-3’s louder than one would expect for a given level of life and detail. And due to this, dynamics tended to suffer (as did the amplifiers driven beyond their limits in the process).

As the years went by, the succeeding models diminished these problems slowly but surely (by tweaking the mass of the drivers, partly) until the 3.6 were a real improvement over the originals. But some of the problems remained and Magnepan stayed on the case.

It took a while, but the result is the new MG 3.7 which takes an even greater leap towards solving these issues by introducing a wrinkle new to the MG-3 series, the Quasi-Ribbon. This variation on the original planar driver appeared earlier in the smaller MC 1.7, proving to be a significant upgrade for that speaker and it provides similar benefits in the 3.7.

Here are some specs…

Freq. Resp. 35Hz- 40 kHz
Sensitivity 86dB/500Hz /2.83v
Impedance 4 Ohm
Dimensions 24 x 71 x 1.625 inches
Shipping Weight 125 lbs

Well, Magnepan does not exactly overwhelm you with specifications! But the manual tells you most of what you need to know to get the best out of these speakers. I suspect that most folks will use solid state amplification since tube amps with enough power and quality to get what the Maggies have to give would be expensive beyond what most would pair with an under $6000 speaker. In a moderate size room, you may be able to get away with a good 100 watt amp, but I would think a 200 watt amp would be more appropriate. I used the fine Rogue Medusa to good effect. Other equipment included a Motif MC-8 preamp, a Yamaha GT-2000 turntable with Koetsu Black phono cart, Pioneer PD-9D SACD/CD player and an Apple Mac Mini based server.

One of the glories of the Magnepan line has been their true ribbon tweeter. The deployment of the Quasi-Ribbon has brought the rest of the speaker more in line with the outstanding tweeter. Coherency top to bottom is better and the speaker sounds much better when played at lower volumes than its predecessors. And since one can listen at lower levels without losing the Maggie quality, in a backdoor way the demands on the amplifier are lessened (as are the demands of ticked off neighbors).

The presentation of the MG 3.7 is different from typical box speakers and how you react to that will go a long way to determining how you react to this speaker. The tall line-source style radiation results in taller images and the dipole figure 8 radiation interacts with the back walls of the room (though lessens the involvement of the side walls) to make larger sounding images in general. Of course, this is a bit of an artifact, the sound of your room superimposed with the sound of the hall as captured on the recording. But it can be argued that this “artifact” replaces the aspects of the original hall sound that mics just don’t capture, enhancing the sense of the Gestalt of a concert hall, if not the concert hall. This subject is worthy of a longer write-up (and will get one eventually in the Philosophy section of this log), but hopefully, you get the idea.

This presentation is tailor-made for some music. For example, The Legendary Pink Dots “The Whispering Wall” sounds as large and atmospheric as this music would seem to demand. Pink Floyd’s “Echoes” benefits similarly. Here, the sounds were engineered in the studio and there is no “original venue” to deal with, so all is well with regard to the soundfield presentation.

With acoustic music, things are less straightforward. Here there is often an original venue to deal with, and the Magnepan’s interaction with the room has a significant effect. But, to me, this does not at all disqualify the 3.7 from doing well on this music. First of all, I have never heard music live in the vast majority of venues, so I have no idea how live music sounds in them to know how severe the dual venue effect for a given recording really is. And recordings do not really capture the sound as it would have sounded for a listener at the recording session in all its aspects, so the added room sound, it can be argued, may add back some of what was lost.

Tonally, the Magnepans do pretty well. To get what they have to offer here, one has to take some care in room placement (distance from rear wall and toe-in). Treble balance can be adjusted by using a feature that allows a resistor to be inserted in the path to the ribbon tweeter. A shorting wire can be removed from the appropriate terminals mounted on the speaker wire connection plate on the lower rear of the speaker and an included 1 ohm resistor put in its place to lower the tweeter output a bit. I preferred the sound in my not overly live room with this resistor in place, deader rooms may benefit by leaving the short in place and very lively rooms may benefit from larger value resistors. A bit of experimentation is the byword here.

If you demand absolute faithfulness to the recording above all, it must be said that the Maggies play a bit fast and loose, not providing the more completely flat monitor sound that some speakers can exhibit under ideal conditions. But these other speakers arguably fall short on providing the concert hall Gestalt mentioned earlier and, as these things go, the 3.7 are still pretty good tonally providing this enhanced sense of venue without too much collateral damage.

Overall, the MG 3.7’s are a lot of speaker for a moderate price. If you have the room, and you like their general presentation, they are hard to beat. I am not the first to proclaim them a relative bargain in today’s market place, but so they are.

The Harbeth Monitor 40

If time-tested tradition is important to you, the Harbeth M-40 will have a leg up right from the start. It is largely an improved descendent of the BBC LS 5/8 and, more so, the Spendor BC-3 dating from the mid 1970’s. Well in the grand tradition, and veddy British.

It should be mentioned up front that the M-40’s have been replaced by the M-40.1. According to Harbeth, the change was necessitated not so much by any pressing need to improve the speaker, but by the original woofer being discontinued. At the same time, the midbass was tamed a bit, to make the speaker a bit more friendly to typical domestic rooms and the midrange driver changed to the newer Radial2 material, which should also be an improvement (in theory). I haven’t heard the new version, but according to word on the street, it’s better but not wildly different. So assume the new version is somewhat better than my review indicates.

These are relatively large stand-mount speakers and are not of a style that is currently in fashion, being wide and chunky. I like their purposeful look, but many may not. At any rate, the wide baffle is integral to their performance. All and all, a well thought out design where form follows function.

No discussion of Harbeth would be complete with out a discussion of Radial material and owner Alan Shaw. The Radial material is their trump card. Developed by Harbeth, its successor (Radial2 material) is employed as cone material in all their current speakers, as the midrange driver of the M-40.1 and the woofers of the rest of their line. It is well suited to the purpose. It has low coloration compared to most of the plastic and paper woofer/midranges generally found in contemporary speakers and its only current competition as a low coloration cone material may come from some of the recent high-tech sandwich cone materials now available.

It’s pretty apparent that Alan Shaw is the main auteur of the Harbeth designs, being responsible for the design and voicing of the line. Actually, he might object to the term voicing, since his goal is a speaker largely without “voice”, one that substantively reproduces the signal applied to its terminals. He has succeeded to a great degree and I suspect what you will hear is his personal philosophy on how music should best be reproduced.

These are relatively large stand-mount speakers and are not of a style that is currently in fashion, being wide and chunky. I like their purposeful look, but many may not. At any rate, the wide baffle is integral to their performance. This is a well thought out design.

There performance is from the general “reproduce the recording” school. You won’t find the expansive images or enhanced sense of image height that planars provide (or some of their coloration, either). You will get the sense that what you are hearing is generally what is on the recording, but with some alterations relating to how recordings tend to be made and the characteristics of real-world rooms.

Most of these deviations are intentional. The transition from the midrange to the treble tilts down a bit, not a bad choice considering that most recordings are made up close and can easily become bright sounding. And the midbass to bass transition has a bit extra, again not unreasonable considering the effects of floor bounce (but see my article “John Dunlavy and the Room” for more on this). In many rooms, depending on your point of view, this may result in a pleasing sense of warmth or a bit of a plodding bass (I come down on the side of the warmth, myself).

There are also some unintentional things, mainly a bit of congestion from the cabinet. As well tuned as its “lossy design” is, its effect can be heard as added thickness on some instruments and male voice. But I think it’s not severe and can be safely filed under the category “nothing’s perfect”. Many other speakers have cabinets with effects much worse and further up in frequency where those effects are more noticeable.

Listening to a few of the Mercury Living Presence series recordings, the somewhat forgiving top end of these speakers did not invite them to produce ear-biting strings. The Merc’s treble emphasis is less in evidence on the Decca/Fruhbeck de Burgos Albeniz Suite Espanola. In either case, the imaging was good if somewhat limited in height and depth and the tonality quite fine.

The vocals on the SACD of Beck’s “Sea Changes”  track “Already Dead” were commendably smooth and the guitars tracked in both channels rang out convincingly if with out the very last word in transient attack. Pink Floyd’s “Echoes” also came through beautifully but, in my view, suffered somewhat from the smaller soundstage that the M-40’s (and, to be fair, most other cone/dome/box speakers) produce. Here a planar can produce a more etherial sound that, to me, is more appropriate to this atmospheric piece.

As associated equipment, I used the Lectron JH-50 (tube) and the Electrocompaniet Ampliwire  (SS) amplifiers and the Motif MC-8 as preamp. For vinyl playback, the Goldmund Studio TT with Well Tempered Arm and Clearaudio Goldmund cartridge was employed. The Ampliwire usefully controlled the bass better, but the JH-50 sounded a bit better overall with a bit more flow and beauty. But overall, both circa 50 watt amps handled the speaker well and the difference in amps was more a difference in “seasoning” rather than any fundamental difference. I suspect that the M-40 would respond to even better amps in kind.

Of course, the Harbeths M-40’s were not cheap and the new 40.1’s are now priced at almost $13,000 (and require stands). But in my view, these are one of the best speakers that espouse their philosophy of music reproduction and one of my personal favorites (For whatever THAT’S worth…). They are what I call an “accountant audiophile” type of speaker, taking only a few liberties and producing a sober, predictable sound that, while it may not completely spark the imagination in the short-term, provides much of the inherent beauty of music in the long.