A pair of
dual concentric Tannoy drivers have been on my
wish list for a long time. Try Google "tannoy
monitor gold" and you will be flooded with web pages
describing aural nirvana from these drivers. Read here: http://www.hilberink.nl/speaker.htm
I rush to tell that I did not become a Tannoy owner this
time due to price. Something in the range of 2,000 USD is
serious money and possibly the price is right, but this
was not the time to invest in speakers that wouldn't be
my main speakers anyway.
Fortunately we have a "Mister
Tannoy" here in town and a call provided me
with two 100 litres closed cabinets and 5 x 15"
Monitor Gold drivers plus a box of crossovers. "Take
your pick! And be sure that you will never hear what the
Golds can do from these 100 litre cabs, they rather need
150-175 litres - or even better, 250 litres!"
Initially I asked for some 12" drivers, HPD 315, but
the face of "Mister Tannoy" went pale and his
quick advise was to forget all about anything other than
the Golds - and preferably the 15" drivers being
superior to the 12" Golds!
250 litres is definitely
into red WAF zone, but who knows. So, I took the whole
lot home and started measuring the SPL response of the
bass and compression driver without any crossover
attached, trying to pair two drivers - because these
35-40 years old drivers do not necessarily measure the
Left: These 15" MGs are huge! Here on
top of ScanSpeak SP38 speakers. Right: No, this is not
how my test cabs looked, but surely some of these vintage
cabs are beautiful.
Vintage drivers and what can be
Left: Apparently the HPDs
are from a period where everything at Tannoy went wrong.
The factory moved to Scotland with major start-up
problems. The membranes got thinner in order to maintain
efficiency from new and poorer magnets, the outer
surround was made from rubber rather than corrugated,
coated paper; the compression driver phase plugs were
sometimes badly machined, etc., etc. All adding to poorer
performance compared to the golden age of Tannoy, the
Sixties and early Seventies. I found this picture on the
web from a HPD driver, and yes, this phase plug is a
Middle: Actually one of
the units had the compression driver voice coil stuck at
one side in the magnet gab - and this driver has probably
been delivering the "Tannoy sound" for decades
with a major 10 dB dip around 2 kHz as can be seen below.
This was how the pole piece (= phase plug) was centered:
Right: The aluminium dome
of the MG15.
Above is seen the impact
on frequency response from various settings of the
"level" knob on the crossover and yes, if I put
the "level" on maximum and "roll-off"
on maximum, I could get a profile that started looking
reasonably linear, but this was not how the MG was meant
to be! This driver was over and out. So, even if you're
buying MGs, be prepared for a bad day in the Sixties at
the assembly line of Tannoy. I have to tell I once owned
a British car build early Seventies, and it wasn't until
I bought a Honda Civic that I found out that cars could
start every morning for ten consecutive years! Hmm...
Hard to believe that this driver was not rejected in some
quality check procedure. These drivers were big money
even at that time. Eventually I found two drivers and two
crossovers that seemed to work properly for initial
listening tests. Crossovers? Yes, these were anything but
consistent in performance. Here's a picture of the
Most of these components
are of good quality and the reason for serious deviation
from target is the electrolytic capacitor in the bass
lowpass section. I measured from 13.3 to 24 uF (!) for
the intended 16 uF. The lowpass section is simplicity
itself: a choke and a capacitor (1.2 mH and 16 uF). 12
dB/octave and a point of crossover around 1200 Hz.
Late MG 15 crossover:
Left: Rear panel with terminals and rotary switches for
adjusting tweeter level and tweeter roll-off.
In this late - and very well kept - version of the MG15
crossover, the electrolytic cap is replaced by a new
capacitor, most likely made the same way as film caps,
only here from etched foil based on physical dimension.
Also for the tweeter section new - and better - caps have
I can only admire the nice wiring job done here. All in
best of order with twisted wires and secured leads. It
takes time to make a crossover like this.
MG15 Crossover Up-Grade
Left: Click image to view large. Right: Up-grade
kit finished. Click image to view large.
Left: MG step response.
As can be seen, the tweeter is connected with inverted
polarity. Actually it's connected with positive polarity,
but being mounted with the inverted dome facing the horn,
the output comes out inverted.
Right: Above is seen a nearfield
measurement of bass/mid and tweeter. Point of crossover
appear to be around 1200-1300 Hz. Very steep slopes
despite the 2nd order crossover. Based on medelling the
sloped are close to LR4. A nearfield bass driver reading
producing a flat response down to 50 Hz is not an
everyday sight, I can tell. And a nearfield reading is
highly dependent on where you actually place the
microphone, so don't pay too much attention to dips and
bumps. The Tannoys do not measure nice, but as seen from
a lot of other big speakers, this does not seem to
compromise sound. Another example of not putting too much
into FR readings of loudspeakers. It tells very little of
how they actually sound. So, with this fine-tuning I
could start listening - and what a sound!
It's hard not to be
completely swept off your feet when you first time
connect these monster drivers. Every time I hook up a new
pair of speakers I run a test CD to check left-right,
polarity, etc., at it's not often you actually hear
"something" from the 31 Hz warble tone on the
test CD, but here it was.
I had never thought my Copland could provide the speed
and transient attack as it appeared connected to these
drivers. 90-92 dB sensitivity and 6-8 ohms impedance is
yummy to most 2 x 50 W valve power amps - and the Copland
I have never been able to hear female vocalists this loud
without serious distress to the ear (= distortion) and
I've never heard applause from an audience from live
recordings this clear. Acoustic bass starts getting the
right proportions and a full drum kit from these speakers
is aural nirvana. No doubt about it.
That's not to say the MGs
like to be played loud, they are very good too at low
volumes and don't need a whole lot of power to be
In my listening room I have the speakers on the long
side. Usually 1 metre from the rear wall and with 1.8
metres to the sidewalls. Use to work fine and so did the
Tannoys - except that they simply appear to be too large
for listening at 2-2½ metres distance. The very first
thing that came to mind when I played music on the
Tannoys was my earphones. Listening nearfield to these
drivers is like putting on a giant pair of earphones,
except that you now can actually feel the bass.
I'm certain the earphone association came from the
coherence of the sound coming from these drivers. This
dual-concentric principle is a little wonder but I have
always been suspicious about the integration of a 90
grams heavy paper cone and a "no-weight",
horn-loaded compression driver. How can this go well? But
it mostly does here. I guess that the large radiating
area of the horn driver - actually of exactly the same
size as the paper cone, as the paper cone is the
horn - is part of the explanation why it performs so
This does not imply that
the Tannoys do not have a "sound" - they very
much do so. When it comes to midrange transparency and
neutrality they are somewhat behind the Acapella SE
set-up. The Acapella SE has a much more neutral midrange
presentation and much better pin-point imaging compared
to the MGs.
Pin-point imaging: Well, we would think that the
dual-concentric principle would make a further
contribution to the overall coherence and seamless
integration of midrange and treble, enhancing pin-point
imaging, but this was not my experience. Sitting at 2½
metres distance I sometimes found it hard to render the
same ease of localisation of vocals and instruments in
the acoustic scenario. These membranes are so huge that
vocals seemed to come from all over the place. I've
experienced the same thing with panel speakers and I
guess that's part of the reason Peter Walker added the
delay lines to the famous QUAD ESL63. To get better
dispersion and to target a point source radiator. So,
we're back to the discussion from the "Infinite
Baffle Speaker" file on pinpoint imaging, and again:
"Narrow speakers with a very wide radiation include
more of the listening room and help create an illusion of
bringing the musicians into the room; while more
directional designs like horns and dipole panels give a
precise view onto the recording itself.
The Tannoys are to my experience quite directional
speakers. I have measured the horizontal dispersion - no
need to do a vertical dispersion here as it will be the
same due to the dual-concentric principle - and it is
very good. You measure the same FR all over the
place, but when listening in stereo, they are quite
directional and you move the speakers around and you move
your head around to find the best position for stereo
integration. These speakers need large rooms and a
listening distance of 4-5 meters to perform the best. Not
my cup of tea for near-field monitoring. I guess the
12" or 10" would be better suited for this
situation but with sacrifice of deep bass.
Monitor Gold Type LSU/HF/15/8
From the frd and zrd files of bass and
tweeter I modelled a new crossover trying to get as close
as possible to the 1.2 mH and 16 uF used in the original
low-pass section. This persistently came closer to a
point of crossover around 2 kHz against the claimed 1 kHz
point of crossover. Measuring all the drivers -
original crossover - there appear to be a major overlap
in the crossover region and no matter what polarity was
given to the tweeter, the nulling effect wasn't visible
at all. The phase-tracking between these two drivers is
indeed very poor.
The weird thing about the MG is that the coil in the LP
section can be varied a lot without affecting the
midrange much, this partly due to the impedance profile.
And this driver is so big that measuring the FR at 1
metre distance is really too short. We're getting into
near-field conditions and these drivers should possibly
be measured at two metres distance, but my workshop won't
allow this and I didn't have time to take the drivers
outside for proper measurements.
However, with 1.2 mH and 16.4 uF+2R2 a reasonably flat
response could be achieved with a point of crossover
around 2 kHz. In fact the same I measured from some of
the drivers fitted with the original crossover. The
compression driver however, seems to target a point of
crossover around 1.2 kHz but due to the drivers being out
of phase the overall result is a reasonably flat response
when the "level" and "roll-off"
setting is used properly.
Left: The measured FR is close to the predicted.
Disregard actual dB level. This reading was not generated
with 2.8 V input.
Right: MG/original crossover (red) compared to Acapella
SE (blue, only midrange+ribbon).
The frequency response
(FR) of these Tannoys looks awful! Why is it this doesn't
leave this driver useless? I've seen FR from
electrostatic speakers that look even worse and yet these
speakers sometimes deliver the best of sounds. After
delivering back the Tannoys I connected the SP38s again
and yes, these speakers are much more well-balanced, the
dispersion is much better - it's simply a more truthful
presenter - but it can never deliver the bass punch and
hard beat of the snare drum that hits you like a bullit
from the MGs.
So, what's to be learned
from these Monitor Golds? Well, sensitivity is an
important parameter and they tell you that most of
today's speakers really do not have the transient
response capability of these ancient drivers. I read that
a lot of enthusiasts using single ended amplifiers will
use high sensitivity speakers in order to cope with the
sometimes very few watts available from these amps. We
see 15" coax Fane drivers used with 5 watts SE amps,
but 15" Fanes are meant for PA application and not
for hifi. Aren't we getting back to some JBL sound - for
better or for worse - in order to provide the necessary
sensitivity? Where is the smooth, well-balanced sound
from high sensitivity speakers? Where are the high
sensitivity speakers that will cope will all sorts of
music and not just trio jazz?
I tried playing some of the old
Beatles LPs with the Tannoys - the very same speakers
that were used for mixing at Abbey Road - and it really
didn't sound too good. I wonder if this was what George
Martin was hearing at the mixing desk.
These medium-sensitivity Tannoys come close in being able
to handle almost anything. I don't find them particularly
transparent but they will for sure tell you that there
are a lot of things your current speakers probably are
I cannot thank "Mister
Tannoy" enough for lending me his wonderful drivers!
Comments from UK reader, who wants
to stay anonymous:
Hello Troels, I enjoyed your story about
the Monitor Golds very much. You ask yourself at one time
after playing Beatles recordings: Is this what George
Martin heard when he was doing the recording? Taken into
account the many variables like room acoustics,
amplifiers etc. It is save to say he probably did.
I used to work with Tannoy 15" units placed in large
Lockwood cabinets at Polygram. These units were used in
many studios around the world during the sixties and
seventies. The sound was not spectacular HiFi nor very
detailed. That is not what a recording engineer is
looking for in the first place when selecting a
professional monitor system. These Tannoys deliver a
reliable sound pattern that allows engineers and
producers to balance the sound and use the large array of
filters and outboard equipment to do a mixdown of a
multitack recording. In studios the HF horn was most
likely to die long before problems with the LF unit would
After we moved to the newly built Wisseloord studios in
1977 the Tannoys were abandoned. At Wisseloord a
completely different system with JBL units was used that
gave a far more detailed sound and better defined spacing
of the instruments. This system was part of the
acoustically designed control rooms.
To double check the voice/orchestra balance we often
used the Philips 9710M units in a realtively small
enclosure. Out of large quantities 9710M frames
selected units were used by Dutch radio to serve as
monitor speakers in broadcast studios. I had the pleasure
of meeting Mr. Koppinga the designer of the 9710M
during the seventies. In Holland there is still a strong
demand for these wideband units after nearly 50 yaers
since their introduction.
With kindest regards.