KLH Nine User manual

to ••• •
The performance of
a loudspeaker system
depends as much
on the care with which
it is produced
as on the
design principles
by which
it operates .
•.
•
KI.H RESEARCH AND DEVELOPMENT CORPORATION
30 CROSS STREET, CAMBRIDGE 39, MASSACHUSET I1i
I
INSTRUCTION MANUAL
KLH RESEARCH AND DEVELOPMENT CORPORATION
30 CROSS STREET, CAMBRIDGE 39, MASSACHUSETTS

,
\
TABLE OF CONTENTS
INTRODUCTION Page 1
INSPECTING FOR DAMAGE Page 2
GENERAL Page 3
OPERATION
Setting Up .' Page 5
Placement Page 6
SIGNAL POWER REQUIREMENTS Page 9
SERVICING Page 11
SPECIFICATIONS Page 12
WARRANTy Page 13
•
I
..
INTRODUCTION
Your KLH Model Nine con-
sists of a balanced pair of full-range,
bi-laterally symmetrical electrostatic
loudspeakers. It is intended to be
used in stereo systems, but can also
be used with a monaural electrical
signal source by connecting the sig-
nal input terminals in parallel. Care-
ful design, frequent and critical
testing, and the use of only the finest
materials insure prolonged physical
integrity and trouble-free operation.
The best overall performance ob-
tainable from this extraordinary
pair of loudspeakers will be most
likely to ensue if you will read this
instruction manual carefully.
1

INSPECTING FOR DAMAGE
Your Model Nine is shipped in two separate cartons,
the larger of which contains the two speaker panels, two
AC cords, a set of two brackets, and two sets of wood
screws (20 small brass screws for attaching brackets, and
12 large ones for mounting power supplies on the bases of
the speaker panels). The smaller carton contains the two
power supplies.
DO NOT THROW AWAY THE CARTONS OR
PACKING MATERIALS. They should be saved in case
the speakers should ever have to be returned for repairs,
or transported elsewhere.
When you unpack your Model Nine, inspect it for
damage. Each Model Nine leaves the plant in perfect con-
dition. Therefore, any visible damage must of necessity have
occurred in handling after it left our shipping platform.
If any damage is evident, the following procedure should
be followed.
1
If the Model Nine was received via public transporta-
tion, please read the SERVICING SECTION of this man-
ual, and follow instructions for returning equipment to
the KLH factory for repairs.
2
If the Model Nine was received directly from a dealer
(if it was not shipped to you via a public transportation
agency), it should be returned to him for inspection and
possible replacement or repair at KLH .
•
2
______ 1
.s
GENERAL
Each of the two full-range loudspeaker systems that
comprise the Model Nine is different from all other loud-
speakers, including other full-range electrostatics, in that
it operates as a dipole acoustic source over the entire
audible frequency range. In practical terms, this means that
in comparison with other loudspeakers the acoustical
properties of the listening room are less important in de-
termining the overall response of the system that includes
the pickup, amplifiers, loudspeakers, and listening room.
The unique performance of these loudspeakers is, how-
ever, only partially attributable to this particular property.
It is due to the magnitude of their radiating areas as well,
which are large compared to all other loudspeakers, and
to the absence of electrical, mechanical and acoustical reso-
nances. The present design embodies a high degree of
refinement of a number of new concepts, which originated
with acousticians who are now at KLH. Some of these con-

cepts were used in the first full-range, push-pull electro-
static loudspeaker capable of producing high acoustic
pressure levels, which was exhibited during a meeting of
The American Physical Society in January, 1953.
The Model Nine introduces almost no distortion at
all in the process of converting electrical signals to acoustic
signals, throughout its very wide frequency range, and
therefore tends to emphasize deficiencies in the performance
of associated equipment. It is incumbent upon the user to
employ only very high quality auxiliary equipment, and to
insure that program material is of commensurate quality,
if optimum enjoyment is to be derived.
NOTE
Low-frequency noise (turntable rumble, tape flutter, record
thumps ), even if it is inaudible, must be kept to a minimum.
Whereas such noise will cause the voice coil of a good electro-
dynamic woofer to wander or bob around within its air gap,
in the Model Nine it will tend to saturate the core of the signal
step-up transformers. The acoustic result in both instances is
the same, i.e., the response at low audible frequencies tends to
become intermittently non-linear, and audible distortion tends
to occur on high-level passages, when these include low-fre-
quency components.
All parts of the Model Nine will operate satisfactorily and
continuously under normal conditions in the home or studio.
Care should be taken, however, not to expose any portion of
the system to temperatures in excess of 110
0
Fahrenheit for
prolonged periods of time. None of its component parts are
affected by the moisture content of the air except when the
relative humidity approaches 100% at temperatures near
100
0
Fahrenheit. Any Model Nine so exposed may suffer a
temporary degradation of performance, but generally will need
only to be left in a suitable environment for a short period of
time to regain fully its original performance.
N. B. - Do Not expose the Model Nine to spray of any kind,
including the mist from aerosol bombs or manually sprayed
cleaning agents, insecticides, deodorizers, etc. 1f the rear grille
needs cleaning, it should be done only with a damp cloth .
•
4
.,
OPERATION
Figure 1: Installing the power supply on the terminal
board at .the base of the panel. Both locating pins
(indicated by arrows) should be engaged at the same
time.
Setting Up
A medium-size Phillips-head, and a small Phillips-head
screwdriver are the only tools required for assembly. After
each panel has been laid face down on a non-abrasive sur-
face, such as a rug, so that the terminal board on the black
base faces UP, the black satin-finish can which houses the
bias supply and step-up transformer network can be installed
with the large round-head wood screws that are packed
within the top of the large carton.
NOTE
The power supplies are interchangeable; however, the
proper installation of the cans on each panel is such that the
labels identifying Right and Left face UP when the panel
is in an upright position. An inspection of the geometry of the
base terminal board and the terminal boards in the cans will
disclose clearly which panel is to be equipped with the can
labelled Right and which one is to have the can labelled Left
installed on its base. The mating of the plugs and sockets of the
two terminal boards is automatic when the locating pins are
inserted into the second hole from the upper end of the flange
on each side of the can. Make sure that BOTH locating holes
are over the locating pins before lowering the cans into place.
DO NOT PLUG IN THE AC CORDS TO ENERGIZE THE
BIAS SUPPLY UNTIL AFTER THE CANS HAVE BEEN
INSTALLED ON THE BASES OF THE PANELS.
5

Placement
The set of brackets
packed in the larger car-
ton are to be used in at-
taching the pair of panels
to each other in a flat 'V',
The long, narrow bracket
('boomerang') is installed
on top of the frames, by
using the pilot holes that
are to be found on one of the upper corner edges of each panel. The
nearly-square, bent bracket ('rooftop') is attached to the rear of the
inside, adjacent ends of the bases, Such a 'V' formation provides a
high degree of physical stability, which may be desirable in the
presence of children or in other situations in which there is a proba-,
bility that isolated panels might be knocked over. '
Although the 'V' arrangement provides good stability, most
purchasers of the Model Nine will probably want greater physical
separation between the two sound sources, to achieve a more enhanced
stereo effect. Experience indicates that NO SPECIFIC PAIR OF PO-
SITIONS SHOULD BE EXCLUDED, The optimum positions of
the panels can be ascertained only by experimentation, It will depend
on a number of factors, among which are the size and configuration
of the room; the type, amount, and location of acoustically absorbent
materials; the position of
the listener within the
room; the type of pro-
gram material, and the
techniques used in re-
cording and transmission;
and very importantly, the
individual preferences of
the listener. In arriving at
the best positions for the
panels, it should be kept
Figure 2: Brackets for joining the two panels
in a flat 'Y'.
~
Figure 3: The 'boomerang' bracket (arrow) is
mounted on the tops of the panel frames, using
predrilled holes.
•
6
in mind that the angle of each panel with respect to the listener is as
important as its location,
A support is available on special order which provides greater
stability when the Model Nine panels are separated.
Placement of a panel parallel with and close to a wall causes
a loss of low-frequency response, This is usually, but not necessarily,
undesirable, If the panels are set into a wall, however, with the back
blocked, the response is necessarily degraded to such a degree that
no reason other
than appearance
could be advanced
in argument for
the purchase of so
expensive a loud-
speaker system,
On the other
hand, if the pan-
els are set into
walls (or a single
wall) in such a
way that each
speaker is free to
radiate both to
the front and to
the rear, without
encumbrance,
there is no degra-
dation of response,
.
n
')
I
___ I
Figure 4: The 'rooftop' bracket (arrow) is mounted on the
rear of the panel bases using predrilled holes.
NOTE
Although no special precautions need be taken other than
those ordinarily imposed when high-impedance devices are
placed in operation, it should be pointed out that the panels
should be located so that they cannot be reached by rain or
salt spray, For other essential precautions, see note on page 4,
7

When a first approximation to final loudspeaker place-
ment has been made, connect the RED and BLACK input
terminals of each can to the 16-ohm and ground (or com-
mon) terminals respectively of the stereo amplifier or
amplifiers. For monaural operation, tie RED to RED and
BLACK to BLACK, and connect to the 8-ohm output
terminals of the amplifier, with BLACK going to ground
(or common). When practicable, both AC cords, after
having been plugged into the motor base receptacles located
near the signal input terminals, should be plugged into a
common extension cord, which in turn should be plugged
into one of the switched outlets on the preamplifier or power
amplifier. When this is not practicable, both cords can be
plugged into the nearest outlet and left plugged in perma-
nently. PLUG INTO 110-120 VOLT 50 to 60 CYCLE
AC only. Within a very short time after turn-on the Model
Nine is ready to operate.
30· ,/
,/
r-'
0.7: 0.3
width ; - -Iength
Of[J of rrn.
30';- ,
Figure 5: Diagram showing positions and angles of the
two panels in a typical listening room for best stereo
performance.
When the Model Nine is used with a low-level phon-
ograph pickup (this is the case in most installations), a
wire should be run from the preamplifier chassis to a good
earth ground. A radiator, water pipe, or grounded electrical
conduit will do. The wire need not be heavy or insulated.
Its function is to prevent electrical feedback from the
loudspeaker to the pickup circuit. Its installation is gen-
erally desirable regardless of the type of loudspeakers used,
•
8
I
but the probability of its being essential to the optimum
performance of a system is greater when electrostatic loud-
speakers are used, since they contain an additional stage
of electrical amplication in the form of a signal step-up
transformer.
A choice for the final placement of the two panels
can be made by playing program material that is repre-
sentative of that which will ordinarily be listened to. In
general, if the panels are separated, the area of good stereo
effect can be enlarged by toeing in , as indicated by the
sketch of a typical installation in Figure 5.
NOTE
Since each panel of the Model Nine operates uniquely as
a dipole acoustic source throughout its full frequency range, the
area in a given room within which a good stereo effect is pro-
duced is much greater than is the case when conventional non-
dipole loudspeakers are used, and toeing-in merely serves
further to enhance this effect.
Signal Power Requirements
A peak acoustic pressure level of approximately 105 db,
which corresponds to the maximum level heard in about
the fifth row of the orchestra in Symphony Hall in Boston,
Mass., U.S.A., can be produced with a Model Nine in a
room that is moderately lively, i.e., equipped with only
a rug and drapery along one wall, having a volume of ap-
proximately 3,000 cubic ft., when each panel is connected
to the 16-ohm output terminals of an amplifier that is
capable of delivering 40 rms watts of undistorted output
power into a 16-ohm resistive load. With this particular
set of conditions as a reference, estimates of power require-
ments for one's individual taste can be deduced by con-
sidering that power requirements rise and fall with the
required acoustic pressure levels, with the amount of
acoustically absorbent material in the room, and with the
9

volume of the room. For each 3 db increase in required
pressure level, the input power must be doubled; and a
corresponding doubling of power is required, if room vol-
ume is doubled and a 3 db decrease in listening level is to
be avoided. The quantitative effect of absorbing materials
is less susceptible of definition. Because its effect is fre-
quency selective, and because most absorbent materials are
most effective in the upper regions of the audio spectrum in
which the music power density is not a maximum, the
presence of such material may require the careful setting
of tone controls, but in general will not require an increase
in power input.
NOTE
UNDER NO CIRCUMSTANCES SHOULD A POWER
AMPLIFIER CAPABLE OF DELIVERING IN EXCESS
OF 100 WATTS RMS (200 WATTS PEAK) INTO A 16-
OHM RESISnVE LOAD BE USED ACROSS THE INPUT
TERMINALS OF EITHER PANEL OF THE MODEL NINE.
ALTHOUGH GENERALLY NO DAMAGE WILL OCCUR
EXCEPT TO THE WIRING (WHICH IS NOT DESIGNED
FOR EXCESSIVE VOLTAGES) WHEN VOLTAGES IN
EXCESS OF THE IMPLIED 40 VOLTS RMS (56 VOLTS
PEAK) ARE APPLIED, THE NECESSARY REPAIRS
WOULD REQUIRE THE RETURN OF THE PANELS
TO KLH. REGARDLESS OF POWER AMPLIFIER CAPA-
BILITIES, NO SINUSOIDAL SIGNAL IN EXCESS OF 12
VOLTS RMS SHOULD BE APPLIED FOR PROLONGED
PERIODS ACROSS THE INPUT TERMINALS OF EITHER
PANEL, SINCE THE CROSSOVER NETWORK COMPO-
NENTS ARE NOT DESIGNED TO OPERATE WITH AN
AVERAGE POWER INPUT IN EXCESS OF 10 WATTS
(12 VOLTS RMS).
•
10
I
SERVICING
If upon delivery the Model Nine seems to be undam-
aged but fails to operate when set up in accordance with
the foregoing instructions, please return it to your dealer
for inspection and possible replacement or repair at KLH.
However, if it was delivered to you via a public transpor-
tation agency, please follow the instructions given below
for returning the system or parts thereof to the factory for
repairs.
If your Model Nine works properly when first installed
but appears to become defective at a later time, please
re-read the OPERATION section of this manual. If the
manual does not provide a clue to the cause of poor per-
formance, or if the system has been damaged during
or after installation, or does not work at all, please follow
the procedure outlined below:
1
If the apparent defect occurs within the two-year war-
ranty period, please write to KLH for a RETURN AUTH-
ORIZA TION. Our service department will promptly send
you either an authorization to return the system or portions
thereof for repairs, or advice that will result in the remedy
of your difficulty.
All repairs that fall within the scope of KLH obliga-
tions under the terms of the warranty will be made free
of charge. If our inspection clearly determines that any
necessary repairs are not covered by the warranty, a mini-
mal charge will be made. When such a repair charge cov-
ers damage in shipment, your claim for damage should be
submitted to the shipper by following his instructions (see
the INSPECTING FOR DAMAGE section of this manual) .
11

2
If the apparent defect occurs after the end of the two-
year warranty period, KLH will make repairs at a minimal
charge if the system or portion thereof is shipped prepaid
to our Service Department.
3
To insure freedom from damage in shipment, the sys-
tem should always be packed as it was when it left KLH.
If the original carton, liners, and polyethylene bags are
available in good condition, ship the system or parts thereof
in the original cartons. Our RETURN AUTHORIZATION
will show the proper arrangement of the components and
fillers in the carton. Ship by Railway Express, United Par-
cel Service, or other agency recommended by KLH. DO
NOT SHIP BY PARCEL POST.
SPECIFICATIONS
A completely electrostatic loudspeaker system
consisting of two complete full-range loud-
speakers with built-In power supplies and
step-up transformers. To insure adequate
reproduction of very low frequencies, a total
radiating area of 28 square feet is used (14
square feet in front and 14 square feet in the
rear); a systematic reduction in area occurs
automatically at higher frequencies to preserve
an appropriate directivity at each frequency.
Solid hardwood frames are less than 3 deep.
Grille cloth is of unobtrusive natural boucle.
Impedance is nominally 16 ohms, and is
primarily resistive in audio range; max. 30
ohms, min. 16 ohms. Recommended amplifier
power per section: at least 30 watts. Size:
70 H x 231,1, W x 21'8 D each section.
Shipping weight: approx. 120 lbs.
I • . -
12
1
-:t
I
W ARRANTY
The Model Nine Dual Full-Range Electro-
static Loudspeaker was designed and built
entirely by the KLH Research and Develop-
ment Corporation. We warrant this system to
be free of defects in performance, materials,
and workmanship. KLH will replace free of
charge any defective part and correct any
defect in workmanship or performance with-
out charge for labor. The obligation of KLH
under the terms of this warranty is effective
only if the defect develops in a normal
installation and under normal use and serv-
ice, and if the entire system, or such portion
authorized by KLH, is returned intact to our
factory at 30 Cross Street, Cambridge 39,
Massachusetts, within two years from the
date of purchase. KLH's obligation to repair
without charge is effective only if the war-
ranty card that accompanies this loudspeaker
is mailed to KLH with a postmark dated not
more than a week after date of purchase.
This warranty is effective only if the
receiving system is properly installed and
used in accordance with our written instruc-
tions. This warranty does not cover abuse,
neglect, or accidental damage, and is void
if our examination discloses wiring not in-
stalled at KLH or if any part of the loud-
speaker has been taken apart, repaired, or
altered outside our factory.
This warranty supplants any other stated
or implied warranties.
13