Classic monitor designs?

Steve, last week I re-read that same interview with Joachim Gerhard in which he made some telling observations, like this one:

- Many "old" paper woofers still sound astonishingly good compared to modern drivers?

- Oh, yes. We have not always went to the better. What many driver manufacturers have done the last years, is to increase the damping to make the frequency response more flat. But some old drivers, like the famous 6,5" paper woofer that Jan Paus at Seas made several years ago, (The Seas CA 17 RCY, ed. note) was optimized for low loss. So they made a compromise between frequency response and sensitivity. This driver was very good, and was used by Wilson Audio for many years. Later, in the 80's, manufacturers started to add more mass, they added more damping, and they made surrounds with high loss. That gave an extremely flat frequency response, but also a lot of energy storage. This compared, the old drivers were much quicker. They had some resonances, but you could get rid of that in the crossover. It was this run for flat response that gave a lot of modern drivers this dull, uninteresting sound. And you can also measure higher second and third harmonic distortion in some of them. If you compare the on-axis response between an old and new driver; you will see that the energy in the treble is far higher than in the new drivers. These so-called "modern" drivers often has a Qms of maybe 0.8 or 0.6. The old drivers had Qms values of maybe 5 to 7! We found that drivers with a very high mechanical Q sound more open, more clean and dynamic. And when you look at it, you find it is very simple, because they have less loss. The surround is easier to move, the spider is better constructed, they have better air flow, higher sensitivity. So a high mechanical Q is a very good indicator of energy storage behavior. This is one of our secrets. One of the many!
 
These Hemp Coned Audio Note drivers with Alnico magnets (OEM manufactured by SEAS) are very nice indeed, as they should with prices starting at £1,452.00 each ;)

I completely agree on the 2- versus 3-way statements, but I am somehow fascinated by the simplicity of 2-ways.
More (on this, in light of this topic) to follow...

10 years ago, I paid 15 euro for a pair of (vintage) KEF's Ditton 15 as a gift to a friend of mine. Beautifully finished in oiled walnut and in excellent technical condition. The cloth of the removable grille needed some re-glueing to the frame, but she has been enjoying these ever since.
 

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As promised, some product highlights from 3a (text edited from french vintage hifi)

The photos of the catalogues from 1977 and 1980 respectively show the success and the growth of the 3A range of speakers. Interestingly enough, they both use what was considered like one of the largest anechoic chambers in Europe at the time, although my suspicion is that KEF had a much better one with better test equipment (HP - Siegfried Linkwitz...)

In the beginning of the 70s, Daniel Dehay, an electronic engineer starts 3A with the help of Alain Guillaud and Max Chalambeau.
Their first model was the 3A ARIOSO in 1972/73, which cabinet was built by GUY.HF. It was equipped with a 38 cm Fostex, a 12 cm midrange from Siare and a compression tweeter from Fostex. about 5000 were built in the first two years. Not bad for a start up...


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The second model was the 3A ADAGIO, an easy rework of the ARIOSO, with the same midrange, a 30cm woofer from Fostex and an ITT tweeter.


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Several versions of this model would follow over the years with many driver configurations, including the latest version in the 1980 catalogue which uses 3A made drivers, favouring the midrange dome instead of the 12cm Siare paper cone. The 3A tweeter claims to reach 30KHz, but I am not sure it could be measured up to that frequency at the time, using the Bruel & Kjaer equipment shown in the catalogue...


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Very interesting thread! Back in the 70's when I was young and broke I would hear of an older young man who had gone ahead and bought monitors. "He's got a set of monitors!" But hey: weren't they built more to hit the listener over the head than for accuracy? I remember going to a high fidelity expo then and some of them literally caused pain. Every decade back in time is worse in general. If you hear a really good remaster of an album from the 60's through a really good contemporary speaker system, you are hearing it better than the artist in the monochrome photograph pensively listening to the playback.
 
In the late 70s and until the demise of the company in the early 80s, 3A designed and manufactured a series of interesting drivers. 25 and 21cm for the woofers and dome speakers for the midrange and tweeters. Focal bought the moulds for the woofers chassis and it is easy to spot them in the early JM Lab productions as well as many other French speaker designers.
The drivers were manufactured in a dedicated factory in Lussac-lès-Chateau.

The most popular product made by 3A was the 3A APOGEE, with a 25cm woofer from Fostex and the same ITT tweeter as in previous models. The Apogee became so popular that 3A had three different cabinet makers and had a production line at GUY HF to assemble them and ship them from a central location.
Later Apogee models featured 3A's own drivers. The attached images feature an early version and 2 later models (with the same frame as the JM Lab Electra 920).
 

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Very interesting thread! Back in the 70's when I was young and broke I would hear of an older young man who had gone ahead and bought monitors. "He's got a set of monitors!" But hey: weren't they built more to hit the listener over the head than for accuracy? I remember going to a high fidelity expo then and some of them literally caused pain. Every decade back in time is worse in general. If you hear a really good remaster of an album from the 60's through a really good contemporary speaker system, you are hearing it better than the artist in the monochrome photograph pensively listening to the playback.

Paul, your experiences in the past with (studio) monitor speakers are probably shared by many of us. Are monitor loudspeakers today, on average, much better than they were 30-50 years ago? Probably, but....
I think we should distinguish between dedicated studio monitor loudspeakers (either nearfield, midfield or far field = large format & full range) and 'monitor type' of loudspeakers. The first category are specifically developed for recording/studio use and therefore should translate the audio signal as 'true to the original' as possible. The exact ingredients of the 'original signal' are very hard, if not impossible to verify and would deserve a (long) thread of its own.

So far, this thread is about (classic) 'monitor TYPE loudspeakers', which may (or may not?) be defined as: 'loudspeakers which share certain technical aspects with dedicated studio monitor loudspeakers and could (limitations considered) be used as such'.

These are just my thoughts. Do not hesitate to shoot!
 
In a nutshell (and therefore oversimplified):
In general 'true professional' studio monitor loudspeakers are not designed to give a pleasant musical experience over long listening hours. Which is NOT to say 'they all fail in this respect'.
'Monitor type' loudspeakers are designed with the same fundamental principles(s) in mind, but not at the price of 'extended listening fatigue'.

Some (full range) professional monitor speakers are used both professionally as well as domestically.

An example:
A local former artist (of world fame) who nowadays is producer of a considerable number of artists uses Genelec studio monitors in his studio.
Before the final mastering he verifies his efforts on vintage JBL 4350b's in order to fine tune tiny details in the mix. According to him: the vintage JBL's are better in retrieving details on (old) LP's and essential in the creation of a final mix that 'won't collapse in the real world' (outside the studio).


genelec_1238apm_1238a_tri_amplified_sam_monitor_1076129.jpg



f11427ef5f8ae281d29b46d23a92b381.jpg
 
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Let's continue and finish the story on 3A...


Probably the most famous product made by 3A was the ANDANTE, one of the very rare electronic feedback speakers of this era (Philips started the trend...). 3A called their system "Acoustic Pressure Feedback" and used a 125W amplifier and associated circuitry to claim a lower limit of 32Hz in a 20 litres cabinet! It made the hifi headlines in no time for sure:
"The Andante won our Compact Quality Award on the basis of its superb sound for its size. It also deserved the award for solid construction. It was organ music that demonstrated best the amazing deep bass of this small speaker...we were astonished to find that the pedal notes of organ, the earth shaking were as loud and clear on the Linear as on a speaker about six times its size". Extract from the 1980 catalog, with no source noted...This was the 1979 version.

The original 3A ANDANTE "ELECTRONIC"

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The 3A ANDANTE LINEAIRE with 3A proprietary drivers in 1979

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Close up view of one of the 3A servo amplifiers. Note all discrete transistors and components

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The 3A ANDANTE in its original form used a 25cm SIARE driver and a compression tweeter from Fostex, as per previous models, then it evolved into the 3A ANDANTE LINEAIRE using three 3A proprietary drivers. The cabinets were still made by GUY HF, 3A being their biggest client at the time. It is not clear who was manufacturing the amplifiers, but they ended up being very unreliable. I guess the combination of low quality, huge investment in manufacturing their own drivers and electronics, as well as the demise of some very large retailers who were the primary output for the sales of 3A speakers had a large influence on the eventual bankruptcy of the company. Interestingly enough, GUY HF was not one of the casualties of this debacle.
3A closing their doors was big news at the time and coincided with the rise of JM LAB/FOCAL who became in time the largest client of GUY HF and eventually buying the business.
Another factor in the failing of the business was the plethora of models and the incessant redesign of successful speakers with new drivers and various revisions of the same models.
 
Later versions of the Adante were actually used in several recording and broadcast studios, according to 3A brochures.

At least during these years, Daniel Dehay did obviously not suffer from a lack of an inventive/scientific spirit with regards to acoustics and loudspeaker technology. He applied several acoustic inventions in 3a products ranging from double bass reflex enclosures (Doublet Acoustique), to phase linearization (Phase Plus) to the development of 3A's proprietary ribbon/planar drivers (Equiphase). These ribbons were used throughout the product range of 3A during its last years from the Adante monitors to large (very high-endish looking) multi-driver towers.

Despite its short existence 3A left a substantial legacy.
For those interested, there are 2 dedicated websites dedicated to 3A and the works of Daniel Dehay:

3A - Art & Acoustique Appliquée

http://www.acoustique-3a-by-daniel-dehay.com

During the last years of 3A's existence Dehay launched a series of loudspeakers under the 'Masters' moniker.
These were obviously developed with professional applications in mind.

After the demise of 3A, Daniel Dehay went to Switzerland to develop his next brainchild: Reference 3A.

I think the (Reference) 3A Master series deserve their own (final) chapter.
 

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This is the post to catch up with my earlier post in which I attached an image of something that looks surprisingly identical to a waveguide... At least from a distance.
Evidently, It is a hyper-exponential cone, made of pure carbon fiber and developed by Daniel Dehay during the final years of 3A.

After the bankruptcy of 3A, Dehay started 3A Audio Design (1985-1990) and then moved to Switzerland to continue 3A Innovative Acoustic (1990-2000). During these two episodes he decided to shift his focus on a small range of high end loudspeakers based on the 3A Master Series.

Why dedicate a 'chapter' to a specific range of loudspeakers?
Because, in my opinion the (Reference) 3A Master-Series embody a pinnacle of monitor loudspeaker design.
Contrary to many later 3A designs, Dehay apparently had clear objectives in designing the Master Series. His experience and some clever engineering culminated in what I would literally consider his Master Piece.
Sloped baffle, off-center positioning of tweeters, 1st order, high sensitivity compared to similar sized monitor loudspeakers, wide range (40->20kHz) in a compact enclosure. High quality of components and materials.
Pièce de résistance of every Master loudspeaker up to today is the |Hyper-Exponential Carbon Fiber Mid Low Woofer.

Development started in 1976...
 
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The research for the Phase Plus induced 3a to find better woofers in order to eliminate the filter and improve phase behaviour with other drivers. During lab tests it became evident that most mid low woofers suffered from undesired resonances, distortion and non linearity causing interference.

As was customary in loudspeaker manufacturing, 3A's (own) woofer cones were made from rigid paper (see Fig. 8).
Efforts to improve these cones made clear the desired performance could not be achieved with the paper cones (available a the time)

At the same time as 2 other french manufacturers: Audax and Siare, Daniel Dehay decided to explore alternative cone materials.
Several materials were tested: aluminium, PVC, Teflon and Kevlar.

Eventually a moulded cone from woven carbon turned out to provide the desired stiffness combined with low mass.
Moreover, the carbon cone is fabricated by 'hot moulding' and therefore leaves a number of choices with regards to cone size and shapes, as well as to the composition of the carbon fiber.
The differences between carbon and paper cones became immediately apparent.
There are hardly any, or no, oscillations between 1000 and 4000Hz. Bare in mind: these tests were done with analog test equipment, like HP spectrum analyzers.

The stiffness of the carbon did pay off, but came with a collateral and undesired rising response above 1000Hz (Fig. 9).
Thus, further studies were done in order to reveal the source of this behaviour. Experiments with dustcaps, phase plugs and additional (secondary) cones showed significant changes in the response behaviour of the cone. This lead to the conclusion that the geometry (shape) of the cone has considerable impact on the response.

First test: cone y = e (exp * x), with power output x = 2,72. This is a (regular) exponential cone (see Fig. 9)


The result is clearly visible; the curve shows a minor resonance which can be easily filtered out. Additional tests between the exponential and regular cone shapes yielded inconclusive results.


Subsequent experiment: hyper exponential cone of type y = 1,5 with output x (see Fig. 10)

An important discovery was made: The behaviour of this cone was near perfect, without oscillations/cone break-up, linear up to 1000Hz and with a smooth roll off thereafter: -3dB at 2000Hz, -6dB at 4000 Hz.



Explanatory notes


  • Fig. 1
    Regular conical shaped cone of PVC (polyvinyl chloride)

    Fig. 2 & 3
    3a Hyper Exponential Carbon Cone

    Fig. 4
    Different Cone geometries (shapes): Conical (C),
    Exponential (E), Hyper Exponential (HE), hypo Exponential (hE)

    Fig. 5 & 6
    Cross-section view of the 3A Carbon Fiber Cone (HE y=2x3 exp x)
    Exponential Cone (E) and three hypo Exponential Cone geometries.

    Fig. 8, 9 & 10
    Comparison of response curves form an Exponential Paper
    Cone(8), Exponential Carbon Fiber Cone (9) and a Hyper
    Exponential Carbon Fiber Cone (10)
 

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Over the past few decades a lot of research has gone into development of all sorts of (fiber enriched) papers and appropriate coatings (by Dr. Kurt Müller et al.), which have resulted in much better paper cones, compared to what was available in the 1970s.
For this and other reasons, I would personally never choose other materials besides paper for mid low duties. For subs its another story, but then again, I am not a fan of subwoofers for listening to music at home.
 
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In 1981 the first range of Master Series loudspeakers were launched, starting with a small M(idi)M(aster) to bigger multi ways.
The MM has become the classic of the range and this tiny monitor certainly lived up to the expectations. This quote from Ultra High Fidelity Magazine is illustrative:

"We first heard this model's ancestor, the 3a MM, in 1989 at CES in Las Vegas, where French designer Daniel Dehay was drawing (and keeping) large crowds with his new line of speakers. We would eventually adopt one of them, the MS5, for our Alpha reference system, but it was the MM that triggered the incredulous stares. One skeptical visitor accused Dehay of having hidden a subwoofer among the speakers. Without a word, Dehay picked up one of the MM's, still playing, and dropped it onto the visitor's lap.
It wasn't just the MM's explosive dynamics that retained attention either. The price was astonishing, at a mere C$1200 (US$1100). Naturally, the importer sold as many speakers as could be made, and Dehay had to pick up an investor so he could expand. But the bean counters took over, and moved production to Spain, to be done by workers who seemed to believe wires were made in two colors for purely decorative reasons. The company soon collapsed.
Dehay eventually turned up in Switzerland, where he set up Reference 3a. He had long complained that his distributors concentrated on selling his low-cost speakers because that was easier. He found a solution: he would make only high end speakers. His new line began at a pricey C$6500, soaring to more than C$16,000. The latter price was for the Suprema, the speaker we wound up adding to our new Omega reference system."
 

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It has been a while.

Although this thread appears to evolve into a monologue, I have collected quite some info which may be of interest to at least a few readers.
It is my intention to add a dash of 'diy' to the 'monitor mix'.

So, next up:
 
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