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A CONVERSATION
WITH
RETHM SPEAKER'S JACOB GEORGE
by Constantine Soo
August 7, 2004
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Rethm Headquarters, India
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Jacob George is the creative force behind Rethm Loudspeakers, which was founded in
1998. Despite his relatively light background in speaker designs, JG’s highly sculpted
creations were envisioned to incubate a new level of fidelity, and the drivers he adopted for
realizing his vision are the Lowther’s. JG’s Lowther DX4-equipped 2nd Rethm is being
reviewed by DAGOGO.
JG spilled substantial ink in sharing his vision with visitors on the Rethm website. But what he
opined in a conversation with DAGOGO will show readers additional insights and thoughts
the Rethm creator has been holding dear to his heart.
Constantine Soo:
Please share with us what you think the best loudspeaker should accomplish.
Jacob George:
It should reproduce live music as accurately and as realistically as possible. This is, naturally,
the aim of every audio designer in the industry, and my answer, therefore, is in no way unique.
The differences come about when we start exploring how each of us goes about trying to
achieve this goal.
Constantine Soo:
Your designs represent some of the most unique thinking in the industry. Tell us about your
background in this industry.
Jacob George:
I do not claim to be an "audio guru" of any sort as I believe I am rather inexperienced in the
field, having been in the business for just about 4 years now, and started seriously dabbling in
loudspeaker design just 2 years prior to that. But I had very definite ideas about what live
music and instruments sounded like.
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Fifth Rethm prototype with stand
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At the age of 9, I was trained to play the violin, and played for our school orchestra -- where,
over many years, the sounds of the different instruments were ingrained into me at close
quarters.
Constantine Soo:
Tell us about what you look for in your designs.
Jacob George:
Apart from the right tonality, which I believe everybody would agree is the fundamental quality
that any serious speaker must have, the things that matter to me are dynamics, transparency,
cohesiveness, the ability to bring out detail, and the ability to soundstage/image effectively
and expansively.
If a speaker did these things well, it would be realistic in its portrayal of music. And I realized
very quickly that only the very high efficiency speakers had the ability to reproduce dynamics
realistically (at both the macro and micro levels). This is one of the main attributes of live
music -- its phenomenal dynamics.
Constantine Soo:
Could you elaborate on the aspect of dynamics in your designs?
Jacob George:
No speaker in existence can reproduce dynamics realistically; but we try to reproduce it as
closely as we possibly can.
Transparency is largely a product of the ability of the cone to react speedily to the signal -- so
speed is of great importance. Cohesiveness is what one gets when one uses a single driver
instead of multiple drivers -- there is a "wholeness" to the reproduction that is very difficult to
put into words.
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Second Rethm 1st prototype
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Fourth Rethm prototype
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This cohesiveness is both the result of not having multiple radiating sources with all the
inherent wave interference problems, and not having multiple drivers with unmatched
tonalities. Matching the tonality of any 2 or 3 or 4 drivers of different sizes is quite an
impossible task, it is like having you and me, both of us, sing middle C, and hoping that we
sound identical – and we will not.
Portrayal of detail is again, I believe, a consequence of speed and transparency, and this is
essential for filling in the finer nuances of a performance.
Many people do not think that soundstaging or imaging is important. I do. For me, this is
what gives the performers "life" -- the 3rd dimension. And this is the one reason why I
became a fan of valve amplification. Good solid state can match almost everything else that
valves do, but I have yet to hear a solid-state amp doing the 3rd dimension. Sure they can
soundstage well, with good depth and so on. But individual performers lack that 3rd
dimensional realism. Through solid state electronics, the performers almost sound like 2
dimensional cardboard cutouts arranged on a stage.
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Constantine Soo:
Before deciding on adopting the Lowther DX 4, have you experimented with others? What is
your opinion on loudspeakers using Kevlars and other exotic materials?
Jacob George:
Before getting into the question of the drivers, I have one more thing to add on the matter of
the "cohesiveness" of single drivers -- and that is that the one other thing that it eliminates are
"phase shifts" between multiple drivers.
There are very few loudspeaker designers who actually design "phase coherent" multiple
arrayed loudspeakers. I believe Vandersteen is one. But the down side of this is that the
crossovers become rather complex -- a simple crossover is bad enough, and a complex one
robs the signal of its "immediacy", potentially adds further colorations, and curtails efficiency
even further.
Now, to the question of drivers. I have heard only a few drivers in my enclosures -- several
models of the Lowthers (DX2, DX3, PM2A, and finally the DX4), the AER, and the Supravox.
I have heard several other full-range drivers, but not in my enclosures -- the Fostex, the Loth-
X, the Phy-Hp (sp?), and some of the Tannoy Dual-Concentrics™. I have actually
experimented with one of the smaller Tannoy’s in my 3rd Rethm enclosure.
Lets just say that they did not impress me enough for me to want to use them in my
enclosures. It is possible that I was making faulty assessments by not hearing them in my
own enclosures, but I think I do have enough of an aural "feel" for my enclosures’ performance
to know their potential even otherwise. Of course, I am open to the fact that I could be
mistaken.
One driver that DID impress me, however, is the "Manger", a very unusual design from
Germany. Although it is not a "cone" but a flat diaphragm, I believe it is still a dynamic driver
rather than a planar. Regrettably, I don't have enough of a feel for it to comment at length on
its relative strengths and weaknesses in comparison to the Lowther’s.
Of the drivers that I did try in my enclosure, I felt that the Lowther’s were potentially the best,
despite their problems in the original, unmodified form, i.e. the midrange and upper midrange
peaks in its frequency response. The AER was certainly a smoother driver, with much less of
this "peakiness" -- but it was also less dynamic (one may be the result of the other).
However, I have just been told that they have a new model out, with a more powerful magnet,
that addresses the issue of this relative "softness". Unfortunately, they are not inexpensive.
And the Supravox just has a very different frequency balance -- one tilted in favor of the lower
end, i.e., it has a fuller mid-bass, but lacks the "sparkle" at the top.
Here it becomes a matter of personal taste, because I know of many people who have opted
for the Supravox over the Lowther, which is the version of the Rethm sold in some parts of
Europe. For me -- I want that upper-end extension. The Supravox does not have a whizzer
cone -- and this may be responsible for both the lack of high-frequency energy, and the lack of
the upper-midrange peakiness. And, they are not inexpensive either!
I opted for the Lowther, and decided that I would take up the challenge of modifying them such
that its strengths were retained, while eliminating the problematic peaks.
I am afraid I do not have any experience with man-made materials/composites, and therefore
shall refrain form commenting on this area. What would obviously be different between
drivers made of different materials would be the harmonics that accompany the principal
sounds. It would have been an interesting exercise to compare the various materials in
otherwise identical drivers -- but impractical in the real world, unfortunately.
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Second Rethem 3rd prototype
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Third Rethem prototype
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Constantine Soo:
Would you like to elaborate on the characteristics of the Lowther DX4 driver that you have
adopted for your 2nd Rethm, and what you have done to satisfy your design goal?
Jacob George:
The DX 4 is the Lowther driver with the most powerful magnet.
Actually, this is probably not strictly true -- as I think they do have another driver with an even
higher flux density among their Alnico magnets, but the magnet is the size of a football, and
weighs a ton. Not very practical to handle. All the DX series drivers have the same
diaphragms, and it is only the flux density that changes. Higher densities allow greater control
of the driver, thereby enabling a tighter, more detailed presentation, with better extension at
both extremes, and a more accurate recreation of ambient detail.
The DX4 still retains the "flaws" of all Lowthers -- namely the two "peaks" in its frequency
response -- one between 1.5kHz and 3kHz, and another one between 5kHz and 8kHz. These
are pretty nasty peaks of about 6dB. My job, really, was to try and "tame" these without
loosing the upper-end 'sparkle" of the drivers.
The Lowther’s do not go on forever into the 30-40khz regions, like some tweeters do. They do
start rolling off gently at about 16khz, so I was unwilling to give up even the tiniest bit of its high
end, as that high-end sparkle is important to me. There have been many mods to the Lowther’
s over the ages...but most of them ended up throwing the baby out with the bathwater.
My first "production" mod was to float a thin rubber foam cone between the main cone and
the whizzer cone. I offered this model for more than 2 years, before dissatisfaction got the
better of me, and realized that I needed to get closer to the ideal. Just coming up with this
new mod was a full 4 months worth of work. I had to try about 150 different cones -- of various
sizes, angles, shapes, and hole patterns; and of the combinations between the one on the
diaphragm and the one that is fixed to the phase plug. It was a very trying period of my life!
Constantine Soo:
In the midst of your ongoing design efforts, is there a single aspect in stereo reproduction that
you find most thought provoking?
Jacob George:
Interestingly, you know, there are many people who talk about being able to "emotionally
connect" to the soul of the music if a particular system is doing things right. This may be true,
at some level......but I have seen people connect emotionally to music being played on the
most horrendous transistor radios, leave alone bad stereo systems. In India, where many
people do listen to the classical forms of Indian music (carnatic and Hindustani), the quality of
sound is, surprisingly, irrelevant to their listening pleasure!
This has often made me wonder what we are trying to do. Actually, even I have to admit that
some of my most moving musical listening experiences have occurred while listening to my
rather pedestrian car audio system! Of course, this does not stop me from trying to design
the best sounding loudspeakers possible -- and trying to sell them.
Oh yes, I am also of the opinion that different people hear differently even with the same
equipment. I attribute this to the fact that each of us have differing geometries to the
architecture of our ears (both inner and outer) . Corroboration on this fact was very effectively
supplied by you -- when you told us that you wife finds some speakers "uncomfortable", which
is why I believe there is no such thing as the "perfect" piece of equipment -- because
"perfection" lies in the ear of the beholder.
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