Electro voice 12 trxb owners manual

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SWMrZ'E ENGINEERING

Incorporating all the design advantages of the famous ElectroA
Voice RadaxQCoaxial principle, the Electra-Voice Model
12 TRXB integrated 3-way loudspeaker includes, also, the
latestdevelopments in the reproduction of the highest audible
frequencies through the use of an integral Super Sonax VHF
driver.

The 12TRXB employs the Mode] T3513 VHF driver. Bass
response is excellent, affording pleasing musical balance
without the masking effects previously experienced from ex-
tended high frequency reproduction

SPECIFICATIONS

35 to 18, 000 cps
Integral 3500 cps

Frequency Response:
Electrical Crossover:
EIA (RETMA) Sensitivity
Rating: 52 db
Power Handling Capacity:
Program Material 20 watts
Peak 40 watts

Nominal Impedance: 16 ohms
Voice Coil Diameter: Woofer 2-1/2 in.
Tweeter l in.
Magnet Weight: 1 1b. , 9.16 oz.
Gauss: Woofer 12,000 G
Tweeter 9, 000 G
Size: 12-1/4 in. dia. x 7 in. deep
overall
Mounting: Four 9/32 holes on an 1171/2 in.
circle
Baffle Opening: 10-1/2 in.
Net Weight: 11 lbs
Shipping Weight: 15 lbs.

THEORY OF OPERATION

The 12 T'RXB loudspeaker is designed to meet optimum
lismning requirements; latest developments incorporated
insure even. smoofli coverage of the entire listening area
The engineered features of the Electro-Voice integrated
3-way speaker system include true concentric mounting
of all reproducing elements; augmented balanced bass re-
sponse in conjunction with smooth, extended high frequency
reproduction, carefully tailored mid- range characteristic to
provide realism and a considerable degree of presence"at
usual sound levels. The 12TRXB incorporates in the high
frequency section the Sonophasthhroat design. Fig. No. 2
shows the cross-section of a conventional high frequency
driver. Response is flat up to 4 or 5 kc, after which de-
structive interference results from inability of the diaphragm
to act as a piston. Increasingly higher frequencies cause
the phase of sound produced at the diaphragm peripheryto
shift with respect to soundproduced by the diaphragmcenter
- this being due to diaphragm deformation (see Fig. 3). In
the Sonophase design, Fig 4, sound from the central portion
of me diaphragm is delayed by the longer path length, re»
storing proper phase relationship and level as the frequency
increases. The importance of the Sonophase throatdesign
is paramount above 12 kc, where sound must be takenirom
the center of the diaphragm and the outer periphery simultane-
ously; in this design this is accomplished withoutdestructive
interference or cancellation wimin the sound chamber. At

FEATURES
0 Massive dieecast frame
0 Viscous damped cloth suspension
3 Ceramic magnet

o Integral Sonophase VHF driver

lower frequencies, where the diaphragm is a piston, and no
phase shift is required in the path configuration, the longer
central path length does not appreciably change the phase
due to the longer wave lengms involved. Further benefits
are afforded in the high frequency section of the Electro-
Voice integrated 3-way speaker systems by the incorporation
of Electra-Voice developed diffraction horns as the method
of achieving the best dispersion. In stereophonic use
especially, a 3 db concentration of sound in one portion of the
room is sufficient to cause an apparent displacement ofthe
subject, with the resultant distortion of the solid or stereo
effect. An adjustable "brilliance control is incorporatedto
allow matching ofresponse to room acoustics, compensating
for high frequency absorptive effects of heavy drapery and
softfurnishingsgerossover network with full 12 db per octave
slope minimizes distortion; edgewise-wolmd aluminumvoice
coil design affords 18% more efficiency and consequentdamp-
ing of transient distortion,

IN STALLATION

Unusually good bass response with the Electro- Voice 12 TRXB
integrated 3-way unit is obmined in the Electra-Voice
Aristocrat, Marquis, and similar enclosures. Where a
baffle is available of the "infinite" type, such as a closet or
a wall with a large volumetric capacity available behind the
cone, excellent results will he obtained in the bass range.
The ideal volume is 20 cubic feet or more; for with this
volume, the low free space resonance of the bass cone be-
comes me controlling factor in achieving the lower octaves
of sound. The response in such an application will extend to
35 or 40 cps.

Where restrictive space of only 3 to 5 cubic feet is avail-
able for housing the speaker, bass response will suffer and
the low range will be compressed. This deficiency may be
offset somewhat by reinforcing the bass through the incor-
poration of a frontal port (bass reflex enclosure). More
accurate design data on this form of enclosure is available
from the Consumer Products Division of Electro-Voice and
in the many articles on enclosure design now published,

MOUNTING THE SPEAKER

Cut a circular hole 10-1/2" in diameter, Four 1/4" mount-
ing holes are provided on the outer periphery of the speaker
frame. Use four No. 12 x 1-1/2" long wood screws, or
preferably drill four 1/4" holes spaced 90°apart on a 11-
1/2" circle (see Fig.1) and employ four 3/16-inch carriage
bolts, 2 inches long with nuts and washers. Secure the
speaker to the front baffle, making certain that the very high
frequency driver horn slit has its long dimension vertical.
This will insure widest dispersion of the high frequencies in
the horizontal plane. Tighten the remaining screws just
enough to compress the speaker gasket.

ADJUSTMENT 0F LEVEL CONTROL: Perfect musical
balance to match the acoustic conditions in any room may be
made by the proper setting of the "brilliance" control. Rooms
having large amounts of overstuffed furniture or thick rugs
will require an advanced setting of the brilliance control of
about 3/4 clockwise rotation (3/4 fully open). Rooms with

12TRXB INTEGRATED
3-WAY SPEAKER

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little absorptive material or of small size and having high
reverberation characteristics, will give best musical balance
when the control is set at abouthalf open. In order to achieve
correct setting for any particular room, rotate the control
while playing a comprehensive musical passage and by cars-
ful listening, youwill have no difficulty in obtaining the correct
balance- the highs and lows will come into balance, placing
the sound "in focus"

CONNECTIONS: No. 22 fixture wire or larger can be used
to connect the 121100} integrated 3-way repreducer to the
amplifier. Connect the two terminals, black and red, on the
12ml! to the"16-ohm" and"Common" output terminals on
your amplifier. The 16-ohm impedance of the 12 TRXB is a
standard nominal EIA rating. A mismatch by as much as
40% may be made without affecting the reproduction of the
unit. If only an B-ohm tap is available on the amplifier, a
loss of loudness will be barely noticeable. A loss of overall
loudness will result from connection to a 4vohm tap.

FUTURE EXPANSION OF YOUR SYSTEM
The 12TRXB integrated 3-way system may be expanded by
the addition of a separate midrange or treble driver. 0n the
JZTRXB a third terminal has been added in facilimte this
addition. To use the speaker alone, without the mid-range
driver, strap the two terminals having red washers. The
chart in Fig. 5 will give details of the exact unit: which are
compatible widi both systems. The Electz'o-Voice Building
Block plan has been devised to make these units available in
a convenient package complete with accompanying levelcontrol
and all necessary wiring harness, enabling installation to be
made with a minimum of inconvenience ordisturbsnce of the
existing system. Detailed insmllstion instructions to enable
the additions in be made are given with each Building Block
and little wchnical knowledge will be required to effect this
modification.

CAUTION NOTES
POWER HANDLING CAPACITy; In program material
feeding through a «lo-watt amplifier, only occasional peaks
actually approach a full 40 watts. The average power is
much less throughout the musical range. Less than 8% of
the mail energy in comprehensive musical passages lies
above 3500 cps. This energy is composed of transient sig-
nals which are never sustained for long periods. Accordingly,
it will be seen that the loudest passages above 3500 cps
seldom reach a total of one watt. The lowest frequency re-
production recommended for the VHF driver in the lZTRXB
is 3500 cps, and attenuation below this point should occur
at the rate of 12 db per octave. This attenuation is afforded
by E-V crossover networks, integral in the lZTRXB.

TEST PRECAUTIONS: A sustained tone from an oscillator
such as is used for test purposes may be employed on the
units for short periods with up to 5 or 7 watts of power, but
at the end of five minutes or so. tremendous heat buildsup
in the sensitive driver and damages the coil. For this reason.
such tests must be of short duration. Naturally, sustained
signals of this kind are never remotely approached in pro-
gram material.

PRECAUTIONS IN TAPE MACHINE OPERATION: If the
speed of atape machine is advanced beyond the normal speed,
high-frequency power is increased at the rate of 6 db per
octave over normal for each doubling of tape speed. 0n fast
forward or rewind supersonic energy of greatmagnitude may
be generated. even though the head gate is open. Always re-
duce volume during this process, even though the signal is
inaudible. This is especially important in fast editing pro-
cedures, where the gate is frequently only partially opened
so that the tape traverse can be cued audibly.

UNSTABLE AMPLIFIERS: Supersonic oscillation may occur
in an amplifier whereby high power inaudible sine wave signals
may generate damagingheat in the driver units. Such oscil-
lation may be detectedwlth an oscilloscope,orby the presence
of heat in the driver unit by feeling the pot structure of the
driver. This can be corrected in some cases by using low-
capscity television twin-lead between the amplifier and
speaker system.

CHANGING TUBES WHILE ANEPLIFIER IS ON: Anodier
cause of excessive power application is the changing of ampli-
fier tubes inlow-level stages while the system is operating,
when the volume control is advanced. The removal or plug-
in of the tube generates a tremendous surge, manytimos in
excess of the rated amplifier power. This will damage
sensitive VHF driver units, treble drivers, andsometimes
cone speakers. Defective switching units in the amplifier
can cause a similar effect.

FEEDBACK: Feedback frequently occurs when the input and
output leads of an amplifier are brought into proximity with
each other. This feedback, inaudible because it occurs at
supersonic frequencies, may cause high overloads. Pre-
cautions should, therefore. be taken to prevent it.

Acoustlc feedback should also be avoided. This condition
may be the result of a speaker feeding back into a microphone,
or itmay be caused bythe oscillations given off by a" micro-
phonic" electronic tube; anodiar common cause is the mechani-
cal vibrstion from a speaker adjacent to the phono pickup or
turntable. Feedka of this nature will build up at a con-
tinuously accelerating rate until some link in thereproducing
chainfails, the amplifier"flat tops", or the power is reduced
below the point of critical excitation. Because damage to treble
and VHF units may occur. due caution should be exercised.

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Fig. 1 - Dimensions Figure 2

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Figure 3
am: To complete a
Full Range 2-way system.
System add the VHF Driver add the Mld- -Rangl Drlvnr

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51,153 TloA/EHD
121')le (rnx swim Already Are 33)
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12'1RX (IRX Speakers Already Are (BB-i)
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Figure 5

Part No. 53281