How it Works
BOSE
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181816
Schematic
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Table of contents
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BOSE 181816 Schematic

Table of Contents
FreeSpace Business Music System Manual pn 181816
ELECTROSTATIC DISCHARGE SENSITIVE (ESDS) DEVICE HANDLING.................................................... 2
SAFETY INFORMATION................................................................................................................................... 3
IDENTIFICATION OF UNIT UNDER TEST....................................................................................................... 4
SPECIFICATIONS............................................................................................................................................. 5
THEORY OF OPERATION................................................................................................................................ 7
DISASSEMBLY/ASSEMBLY PROCEDURES................................................................................................. 11
Main Assembly Procedures ....................................................................................................................... 11
TEST PROCEDURES..................................................................................................................................... 18
PART LISTS AND EXPLODED VIEWS........................................................................................................... 21
Figure 8. Flush-mount Loudspeaker Packaging Illustration........................................................................28
FreeSpace®6 Electrical Part List, PCB P/N 177300, Revision 0 .............................................................. 31
FreeSpace
SCHEMATICS AND PCB LAYOUTS............................................................................................................... 49
6 Electrical Part List, PCB P/N 177300, Revision 1 .............................................................. 40
1
ELECTROSTATIC DISCHARGE SENSITIVE (ESDS)
DEVICE HANDLING
This unit contains ESD sensitive devices. We recommend the following precautions when repairing, replacing or transporting ESD sensitive devices:
• Perform work at an electrically grounded work station.
• Wear wrist straps that connect to the station or heel straps that connect to conductive floor
mats.
• Avoid touching the leads or contacts of ESDS devices or PC boards even if properly grounded. Handle boards by the edges only.
• Transport or store ESDS devices in ESD protective bags, bins, or totes. Do not insert unpro­tected devices into materials such as plastic, polystyrene foam, clear plastic bags, bubble wrap or plastic trays.
CAUTION: THE FREESPACE®6 BUSINESS MUSIC SYSTEM CONTAINS NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE.
PROPRIETARY INFORMATION
THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF BOSE® CORPORATION WHICH IS BEING FURNISHED ONLY FOR THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED FOR ANY OTHER PURPOSE.
2

SAFETY INFORMATION

1. Parts that have special safety characteristics are identified by the symbol on schematics or by special notes on the parts list. Use only replacement parts that have critical characteristics recommended by the manufacturer.
2. Perform leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit before returning the unit to the customer. Use the following checks to perform these measurements:
A. Leakage Current Hot Check-With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Do not use an isolation transformer during this test.) Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI) C101.1 "Leakage Current for Appliances" and Underwriters Laboratories (UL) 1492 (71). With the unit AC switch first in the ON position and then in OFF position, measure from a known earth ground (metal waterpipe, conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket, metal cabinet, screwheads, metallic overlays, control shafts, etc.), especially any exposed metal parts that offer an electrical return path to the chassis. Any current measured must not exceed 0.5 milliampere. Reverse the unit power cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZARD THAT MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO THE CUSTOMER.
B. Insulation Resistance Test Cold Check-(1) Unplug the power supply and connect a jumper wire between the two prongs of the plug. (2) Turn on the power switch of the unit. (3) Measure the resistance with an ohmmeter between the jumpered AC plug and each exposed metallic cabinet part on the unit. When the exposed metallic part has a return path to the chassis, the reading should be between 1 and 5.2 Megohms. When there is no return path to the chassis, the reading must be "infinite". If it is not within the limits specified, there is the poss­ibility of a shock hazard, and the unit must be repaired and rechecked before it is returned to the customer.
3

IDENTIFICATION OF UNIT UNDER TEST

When servicing a FreeSpace®6 take notice of the following attributes:
• PC Board Part Number
• Revision Level Number of the PC Board
• Unit's Voltage Variation Type (100V,120V, 220V, 240V).
There are two types of FreeSpace 6 units manufactured. If the unit you are servicing has a switch denoted by surface/flush mount speaker icons in block 12 of the front panel, then you have a 2 EQ unit. If not, then you have a 1 EQ unit.
The EQ changes are represented on page 56 (Sheet 7, PCB Tone Control and Surface EQ) of this manual. The 2 EQ unit will have all optional components (OPT) populated on the I02 board. The 1 EQ unit will be depopulated.
Refer to the applicable part list and schematics as follows:
• There are two Electrical Part Lists, one for Revision 0 and one for Revision 1 of PCB
177300.
• The PCB Schematics and Layout views supplied with this service manual are applicable
for Revisions 0 and 1 of PCB 177300.
NOTE: The PC board revision level number is marked on the PC board as follows:
1
4

SPECIFICATIONS

Dimensions Module 4.0" H x 7.5" W x 15.0" D (10.16 x
19.05 x 38.10 cm)
Flush-mount Speaker Assembly: Flange Dia.: 6.25" (15.9 cm)
Hole Dia.: 5.75" (14.6 cm) Depth: 6.5" (16.5 cm)
Surface-mount Speaker Assembly: 3.3" H x 7.6" W x 6.4" D (8.3 x 19.3 x
16.33 cm)
Weight Module: 11.3 lb. (5.14 kg.)
Flush-mount Speaker Only: 2.1 lb. (.97 kg) (Including Mounting Hardware): 4.2 lb. (1.9 kg) Surface-mount Speaker (Including Mounting Hardware):
Driver Flush-mount & Surface-mount Speaker: 2.5" Full-range Driver Beamwidth Flush-mount & Surface-mount Speaker: 150° @ -6 dB
2.5 lb. (1.2 kg)
Performance Specifications
Input Sensitivity Music Input: 200mV
Page Input: 20 0 µ V
Power Output 16W into 2Ω load Power Requirements 120V or 220-240V ~ 50/60 Hz Remote Volume
Control Value Music Input Impedance Channel A: Balanced: 32kΩ
Channel A: Unbalanced: 11kΩ Channel B: Unbalanced: 10kΩ
Page Input Impedance Balanced: 9kΩ
Unbalanced: 1kΩ
Page and Line Output Impedance
Page Gain 0dB to 80dB adjustable Frequency Range 80Hz - 16kHz Noise (line into loudspeaker outputs): 20Hz - 20kHz bandwidth; -65dBV at
Frequency Response 20Hz - 20kHz, ±1dB, referenced to
10kΩ, Audio taper
400Ω
20dB gain into 10kΩ load
1kHz at line outputs
5
Performance Specifications (Continued)
Maximum Acoustic Output
Opti-voice® Paging Circuitry
82dB-SPL in 20,000 cubic feet room with a speech band RT
Ensures a constant paging level over a 30dB dynamic range by compressing the page signal. Music gradually returns to original level after page.
60 of 0.5 secs
6
THEORY OF OPERATION
1. OVERVIEW
®
The FreeSpace cial environments. The FreeSpace 6 components have been engineered to work together as a system. The electronics have separate compressors for music and paging sources that de­crease the dynamic range of the audio signal, thereby increasing the audibility of musical passages and paging anouncements. A protective compressor in the power amplifier prevents audible overload distortion if the user attempts to play the system too loud.The system has the following features:
• High-fidelity sound over a large area
• Active equalization, music compression, and system overload protection
• Opti-voice® circuitry for high quality paging capability
• Remote control of volume and source selection
The circuit descriptions that follow are grouped according to the PCB section and sheet num­ber of the schematic.
2. IO1 PCB
2.1 IO1 PCB Schematic Sheet 1
6 business music system delivers high-fidelity music and paging in commer-
Music Input A is routed through a differential input amplifier (U4) which accepts balanced sources or unbalanced sources. The amplifier output is passed through a gain trim pot and presented to the Music A/B selector. Music Input B is fed directly to a gain trim pot and then to the Music Input A/B selector.
Music Selector A/B is a 2P2T analog switch, implemented with a special switching op amp (U11,U12)). The op amp is controlled by the signal SELECTB.
The Music Selector Interface is a two transistor circuit that normally selects Music Input A. With the Remote Selector switch open, transistor Q2 is on, which turns on D4, the Source A LED, pulling SELECTB low. This turns off Q1, keeping its LED off. When the Remote Selector switch is closed, Q2 is turned off, allowing Q1 and D3 (the Music B LED) to turn on. This moves SELECTB high and turns off the Source A LED. When SELECTB is high, current is no longer sunk from U11 and U12’s SW pin, and they select Music Input B.
2.2 IO1 PCB Schematic Sheet 2
On their way to the compressor, the left and right music signals pass through a stereo/mono switch, S1. After the compressor (U7 and part of U6), the music signals leave this sheet. The compressor is enabled by a logical function of SELECTB, Music Compressor A, and Music Compressor B enable switches. The logic (U8) determines that the compressor will be enabled only for a music source if that source is the one currently selected and if it has been enabled for compression via its switch (S2 or S3).
The compressor offers a maximum gain of about 20dB for very low level signals and operates at a 2:1 slope. It slowly raises the level of quiet musical passages, and quickly reduces the level of loud passages. The two channels are cross coupled to maintain a centered stereo image. By selecting the rectifier input source as a DC current, the compressor is disabled (U9).
7
The two sections of U15 are used to control a bi-colored Music-Compressor LED, D2. As long as the compressor is enabled, the LED glows green to indicate how active the compressor is. Whether or not the compressor is enabled, the LED is also acting as a watch dog and will flash red if the signal presented to the music compressor is too great for it to handle.
2.3 IO1 PCB Schmatic Sheet 3
The Page Input is presented to a differential amplifier (U2) that can handle a wide range of source voltages, as well as balanced or unbalanced sources. S5 determines the gain of the first stage (0dB or 30dB). The page signal next passes through U2, where it can be given a gain of 0 to 30dB, as determined by R1. At S4, the page signal is routed either through
another variable gain stage (U2, gain adjustable from 0 to 20dB), or through the Opti-voice
®
compressor. The Opti-voice compressor (U5 and part of U6) provides anywhere from 20dB of gain to 10dB of loss, depending upon the signal level.
Finally, the output of S4 is passed through the Page Muting stage (part of U10, Q3, and Q4), in which it is muted unless the page trigger circuits have detected a signal. The Page Output connector (J2) is driven by part of U10, acting as a buffer stage.
The two sections of U3 are used to control a bi-colored Opti-voice Compressor LED, D5. As long as the compressor is enabled; the LED glows green to indicate how active the compres­sor is. Whether or not the compressor is enabled, the LED is also acting as a watch dog and will flash red if the signals at U2’s outputs are too great for the compressor to handle.
2.4 IO1 PCB Schematic Sheet 4
The Page Trigger circuits first offer a user sensitivity adjustment, via R3, then provide up to 26dB of gain for the trigger signal. V13, Section B acts as a threshold comparator and a peak hold circuit. For signals exceeding the threshold, the circuit changes state rapidly, and holds the new state long enough to ride through syllabic and inter-word pauses in paging. The two remaining sections of U13 provide a fade-back time constant for the music and adjust the control voltage levels to suit the muting transistors Q3,4,5,6 and 7.
Two sections of U14 mix the music and page signals, while the other two sections of U14 provide the mono versions of the music signals and the music+page signals. Switch S9 en­ables paging in the signals fed on to the speaker outputs. R2 allows for adjustment of the page level relative to the music.
3. IO2 PCB
3.1 IO2 PCB Schematic Sheet 5
S7, the Line Output Mode switch, selects the signals sent on to U200 and the Line Outputs. Relay K1, controlled by Q201 and Q200, mute the Page and Line Outputs during power on and power off transitions to prevent glitches from reaching the outputs.
8
3.2 IO2 PCB Schematic Sheet 6
The remote volume control function is implemented on this sheet with a dual VCA, IC U201, and its buffer, U202. (An alternate part could be used in U201A, but this is a manufacturing alternative, not a field service alternative.) U201 is controlled by a current sourced into the signal VCA, coming from Sheet 7. When VCA is about 2mk, gain is at its maximum, which is unity (0dB). When the current into VCA is zero, the gain is essentially off (-80dB or so).
S4 and its related components are factory set gain trims.
3.3 IO2 PCB Schematic Sheet 7
Transistors Q202, Q203 and related components transform the variable resistance of the remote volume control into the current source that feeds signal VCA, on Sheet 6.
U205 is a conventional bass and treble control, while U203 is an equalizer stage intended to
®
provide the EQ adjustment needed when FreeSpace
6 systems are configured with Surface-
mount loudspeakers (as opposed to the Flush-mount FreeSpace 6 speakers).
4. Power Amplifier PCB
4.1 PA PCB Schematic Sheet 8
U301, part of U300, and U302 implement a acoustically correct low frequency compensation for more natural bass. The other two sections of U300 process the signal CD-DIA (“clip­detect-diagnostic”, see Sheet 10) into a control signal that is sent through P2A, remote volume control circuit on Sheet 7 . CD-DIA becomes active when the power amplifiers are driven into clipping. This in turn causes the remote volume control circuit to be turned down so that clip­ping ceases.
4.2 PA PCB Schematic Sheet 9
U303 combines the low frequency compensation signal with the full range signals and then equalizes them to compensate for room acoustic and speaker driver characteristics.
4.3 PA PCB Schematic Sheet 10
U304 and U307 are power amplifiers with differential outputs. Both amplifier outputs can deliver 16 watts into the nominal 2 ohm load of a pair of FreeSpace 6 speakers. The CD-DIA pins are pulled low when the amplifiers begin to clip. This is used to control a compressor implemented on Sheet 9 and Sheet 7.
D306 develops the DC power supply for the power amplifier. Q305 and associated compo­nents constitute a shunt voltage regulator which only conducts in the unlikely event of both a high power line voltage and a low or no signal output case. It holds 18V maximum which is presented to U304 and U307.
D305, U305, and U306 are the +/-15V supply for all the circuits except for the power amplifier. The power transformer secondary plug can be inserted two ways; one way will handle a nomi-
nal 120VAC main, the other a nominal 240VAC main. The two orientations of this plug are noted on the PCB.
9
5. Remote PCB
REM PCB Schematic Sheet 11
The circuits on this sheet are contained on a small PC board inside the remote control. The potentiometer is wired as a 10K ohm rheostat and controls the remote volume control circuits on Sheet 6, while the SPST switch controls the Music Selector on Sheet 1.
10
DISASSEMBLY/ASSEMBLY PROCEDURES
Main Assembly Procedures
Note: Certain parts will be referred to in
these procedures. The numbers in paren­theses represent individual parts called out in Figure 1. The callout numbers corre­spond to those on the part lists.
1. Chassis Cover/Top Cover Removal
1.1 Place the amplifier flat on the work-
bench with the Bose corner.
1.2 Detach the chassis cover (1) by holding both corners and pulling upward. Once the cover is loosened, slide the bottom tabs out and away from the unit.
1.3 Use a phillips-head screwdriver to remove two silver screws (2) securing the chassis top cover (3).
®
logo in the upper-left
2.2 Align the screw holes of the top cover with the screw mounts located on the base. Also align the four metal tabs on the base with the tab slots on the cover. There are also six metal tabs located on the bottom edges of the cover that must be aligned when the cover is finally seated.
2.3 Slide the cover down over the base until the screw holes are aligned and all tab slots are locked into place.
2.4 Secure the chassis top cover (3) by tightening two silver screws (2) with a phillips-head screwdriver.
2.5 Position the three bottom tabs on the chassis cover into the slots located in the chassis base. Press the chassis cover down over the chasis-top cover to secure it.
3. Amplifier PCB Removal (Chassis Base)
1.4 Gently lift the right side of the chassis
top cover up at a 45° angle and pull to the right and up. This is done to clear the left screw mount away from the Amp PCB (8) when the cover is lifted off.
IMPORTANT: Be careful not to pull the three cables connected to the Amp PCB (8)
assembly. They must be disconnected before final removal of the chassis-top cover.
2. Chassis Cover/Top Cover Replacement
2.1 Place the chassis-top cover (3) over the
chassis base (4). Align the cover so that the left-side screw mount of the chassis base will slide between the IO1 PCB (8) and the inside surface of the chassis-top cover. Otherwise there will be difficulty securing the cover.
3.1 Remove the Chassis Cover/ Top Cover (Procedure 1) .
3.2 Separate the chassis-top cover from
the base by disconnecting both two-pin cables from the Amp PCB's (8) P3A and P3B connectors. Disconnect the eight-pin cable from the Amp PCB's P2A connector.
3.3 Disconnect the following cables:
• Disconnect the transformer's five-pin primary cable from the Amp PCB's P7 connector.
• Disconnect the transformer's five-pin primary cable from the Amp PCB's P4 connector.
• Disconnect the main power two-pin primary cable from the Amp PCB's P4 connector.
IMPORTANT: Be sure to notice the orien­tation of the transformer's five-pin primary cable. Pin 1 is keyed to pin 1 of Amp PCB connector P6 (or P7 depending upon the unit's applicable voltage rating).
11
CHASSIS COVER
1 
2
CHASSIS TOP COVER
COUPLER BAR
3
IO1 PCB
7
8
6
IO2 PCB
8
8
AMP ASSY
5
9
P3B
P2
P5
P3A
5
10
12
5
CONNECT
TO P3B BLU./GRY.
CONNECT
TO P3A RED/BLK.
PRIMARY
5
2X
11
CONNECT
TO P5
CHASSIS BASE
4
SECONDARY
13

Figure 1. Main Disassembly/Assembly Exploded View

12
3.4 Remove two black screws (5) from the
Amp PCB (8) and three black screws (6) from the Heatsink (7).
3.5 Remove the Heatsink/Amplifier PCB Subassembly from the chassis base.
3.6 Place the subassembly on the work­bench with the heatsink (7) fins down.
3.7 Remove three black decoupler bar screws (5) that connect the heatsink to the Amplifier PCB.
3.8 Remove the Amplifier PCB (8) from the heatsink.
4. Amplifier PCB Replacement (Chassis Base)
IMPORTANT: Thermal grease should be
applied to the heatsink before seating the PCB.
4.4 Connect the following cables:
• Connect the main power's two-pin cable to the Amp PCB's P5 connector.
• Connect the tranformer's secondary five­pin cable to the Amp PCB's P4 connector.
• Connect the transformer's primary five-pin cable to the Amp PCB's P7 connector.
IMPORTANT: Pin 1 of the transformer's five-pin primary cable is keyed to pin 1 of Amp PCB connector P6 (or P7 depending upon the unit's applicable voltage rating).
4.5 Install the Chassis Cover/Top Cover (Procedure 2).
5. Transformer Removal
5.1 Remove the Chassis Cover/Top Cover (Procedure 1).
5.2 Disconnect the following cables from
the transformer:
4.1 Place the Amplifier PCB (8) onto the heatsink (7). Align the coupler bar (9) screw holes with the screw holes of the heatsink. The PCB should be component side up with the power devices resting on the inner side of the heatsink.
4.2 Secure the coupler bar and Amplifier PCB to the heatsink by tightening three black screws (5).
IMPORTANT: Make sure that the coupler bar does not make contact with the metal tab of transistor Q305.
4.3 Place the Heatsink/Amplifier PCB subassembly solderside down into the chassis base. Secure the upper-left hand corner of PCB onto the standoff snap. Secure the subassembly to the chassis base by tightening two black screws (5) on the Amp PCB and three black screws (6) on the heatsink.
• Disconnect the transformer's five-pin primary cable from the Amp PCB's P7 connector.
• Disconnect the transformer's five-pin primary cable from the Amp PCB's P4 connector.
5.3 Remove transformer cables from cable clamps (12) and lift the transformer from the chassis base (4).
6. Transformer Replacement
6.1 Place the transformer (10) into the
recess of the chassis base and align it with the chassis base mounting holes. Make sure that the primary side is facing the IEC Connector Assembly
(13).
6.2 Place the two transformer clips (11)
over the transformer's mounting tabs. Secure the transformer to the chassis base by tightening the two black screws (5).
13
6.3 Connect the following cables:
• Connect the transformer's five-pin sec­ondary cable to the Amp PCB's P4 connec­tor.
• Connect the transformer's five-pin pri­mary cable to the Amp PCB's P7 connec­tor.
IMPORTANT: Pin 1 of the transformer's five-pin primary cable is keyed to pin 1 of Amp PCB connector P6 (or P7 depending upon the unit's applicable voltage rating).
6.4 Install the Chassis Cover/Top Cover (Procedure 2).
7. IO1 & IO2 PCB Removal (Chassis Top)
7.1 Remove the Chassis Cover/Top Cover (Procedure 1).
8. IO1 & IO2 PCB Replacement (Chassis Top)
8.1 Connect the 12-pin cable to connector
P1A on the larger board.
8.2 Carefully align both board's connectors into the chassis top cover and snap them onto the chassis standoffs.
8.3 Secure the two-pin and the eight­pin cables into the cable clamps (12).
8.4 Replace six black screws (5) and tighten to secure both boards.
8.5 Install the Chassis Cover/Top Cover (Procedure 2).
7.2 Remove six black screws (5) from both
Amplifier IO PCB's (8). Remove the IO2 PCB board first. Grasp it by the top cor­ners, lift up and off the chassis-top's stand­offs. (Note: The IO boards are connected by a 12-pin cable. Do not attempt to sepa­rate until both are removed).
7.3 Remove both two-pin and eight-pin cables from the cable clamp (12) from the inside of the chassis-top cover.
7.4 Grasp the IO1 PCB board by its top corners, lift up and off the chassis-top's standoffs. Position the board at a 45° angle and carefully pull it back so that the I/O connectors clear the top cover.
7.5 To separate boards, disconnect the 12­pin cable from connector P1A on the larger board.
14

Flush-Mount Loudspeaker Procedures

1. Flush-mount Loudspeaker
NOTES: Certain parts will be referred to in
these procedures. The numbers in paren­theses correspond to the individual parts called out in Figure 2.
C. Use Procedure 1.2 to return the grille to the enclosure.
1.5 Terminal Cup Removal
A. Use a phillips-head screwdriver to
remove one screw (7) from the junction-box cover.
1.1 Grille Removal
To remove the grille (Not Shown) take a scribe or a small flat-head screwdriver to grasp an edge of the grille. Gently lift the grille out from the enclosure (2).
1.2 Grille Installation
Push the grille into the enclosure (2) until it is flush with the rim of the enclosure. Orientation of the logo is not necessary.
1.3 Driver Removal
A. Use Procedure 1.1 to remove the grille from the enclosure (2).
B. Use a phillips-head screwdriver to remove four screws (3) securing the driver (4) to the enclosure's baffle (6). Carefully lift
the driver from the enclosure and cut the wires as close to the terminals as possible.
1.4 Driver Replacement
A. Strip the terminal wires from the terminal
cup (5) and connect them to the replace­ment driver (4). Connect the red wire to the + positive terminal and the black wire to the
- negative.
B. Swivel the junction-box cover out to expose the terminal cup (5) in the recess of the speaker enclosure (2).
C. Use a phillips-head screwdriver to remove three screws (3) that secure the terminal cup to the speaker enclosure.
D. Use Procedure 1.3 to remove the driver (4) from the speaker enclosure (2).
E. Disconnect the terminal wires from the
driver and remove the faulty terminal cup.
1.6 Terminal Cup Replacement
A. Use Procedure 1.4 to connect the replacement terminal cup (5) to the driver (4).
B. Place the enclosure (2) on its side. Fit
the terminal cup into the slot at the back of the enclosure. See Figure 2 for the proper orientation of the terminal.
C. While holding the terminal from the inside of the enclosure, tighten three screws (3) with a phillips-head screwdriver.
D. Use Procedure 1.4 to secure the driver (4) to the enclosure.
B. Align the driver so their four screw holes
align with the screw holes of the enclosure's baffle (6). Secure the driver to the enclosure (2) by tightening four screws
(3) with a phillips-head screwdriver.
E. Use Procedure 1.2 to secure the grille
to the enclosure.
15
Junction-Box Cover
7

Surface-Mount Loudspeaker Procedures

1. Surface-Mount Loudspeaker
3
NOTE: The Surface-mount Loudspeaker
8
has only two removable and replaceable parts, the grille and the grille's scrim cloth. Refer to the Surface-mount Assembly Part List for the grille and scrim cloth's order
2
numbers.
1.1 Grille Removal
5
Red
4
Black
The Baffle is
6
Adhered to Enclosure
3
Item 1 on the  Packaging Part List
Figure 2. Flush-Mount Loudspeaker
Exploded View
Grasp one edge of the grille with a small scribe and gently pull the grille from the
enclosure. The grille's scrim cloth is behind the grille.
1.2 Grille Replacement
1. Place the scrim cloth inside the grille.
2. Place the grille over the twiddler section
of the enclosure (Refer to Figure 3 for the correct orientation). Press the grille until it snaps into place.
16
Grille

Figure 3. Surface-mount Loudspeaker

17

TEST PROCEDURES

Main Assembly Test Procedures

Test Set-Up Parameters
Switches
All switches are referenced by their block diagram location on the top of the unit. Set them according to the table below.
Block
No.
10 Line Output Mode center(Music
Switch Description Setting(s)
1 Page Source Gain left (0dB) 2 Optivoice Compressor left(off) 5 Page Enables Left and
Right
7 Music Compressors A
and B
9 Music Input Mode rear(stereo)
right(on) forward(off)
+Page)
Input Connections
Page Input Connect the positive (+) side of an oscilla-
tor to the positive input terminal. Connect the negative (-) side to the negative (-) and common input terminals. Do this using quick connectors (P/N180094) supplied with the unit.
Music RCA Inputs A, B (Left and Right) Connect the positive (+) side of an oscilla-
tor to the positive input terminal on the RCA jack. Connect the negative (-) side to the negative (-) and RCA jack ground sleeve.
Output Connections
Page and Line Outputs (Left and Right)
Potentiometers
All potentiometers are referenced by their block diagram location on the top of the unit. Set them according to the table below.
Block
No.
1 Page Source Gain 3 Page Trigger 4 Page Mix Trim cw(max)
6 Music A and B Source
12 Treble and Bass Trim center(flat) 13 Volume Trim Right cw(max
Pot. Description Setting(s)
ccw(0dB)
Trim
cw(max)
Level
cw(max
Trim
gain)
gain)
Connect the positive (+) side of the test equipment to the positive (+) output termi­nals. Connect the negative (-) side to the negative (-) output terminals. Do this using quick connectors (P/N180094) supplied with the unit.
Speaker Output (Left and Right) Use the same output connections as above
with a 2Ω/50Watt resistor as a load.
All test equipment should be isolated from ground (floated).
18
1. Page Input To Page Output Gain
6. Noise
1.1 Apply a 5 Vrms, 1KHz signal to the
Page Input.
1.2 Measure the Page Output. Should be
4.22 Vrms (+ .78 Vrms/ - .67 Vrms).
2. Page Input To Line Outputs Gain
2.1 Apply a 5 Vrms, 1KHz signal to the
Page Input.
2.2 Measure the left and right Line Output. Should be 4.22 Vrms (+1.09 Vrms/ -.87
Vrms).
3. Music Input A to Line Outputs Gain
3.1 Apply a 500mV rms, 1KHz signal to the
Music A left and right input.
3.2 Measure the left and right Line outputs. Should be 4.47 Vrms (+.84 Vrms/ - .71
Vrms). Note: Repeat this test for Music Input B.
To select Music Input B, short the remote select input.
4. Music Input A to Speaker Outputs Gain
6.1 Set the volume control to Max.
6.2 With the source off, measure the left
and right Speaker output. Should be
mVrms.
7. Full Power Distortion
7.1 Apply a 130 mVrms, 800 Hz signal to
the left input.
7.2 Measure the distortion at the left Speaker output. Should be
7.3 Change the frequency to 95 Hz and adjust the applied signal to get 5.66 Vrms at the left Speaker output.
7.4 Measure the distortion at the left Speaker output. Should be Note: Repeat this procedure for the right channel.
8. Separation
8.1 Apply a 100 mVrms, 800Hz to the right
Music A Input. Terminate the left Music A Input with a 50
Ω resistor.
≤ 1% THD.
≤ 2 %.
≤ 5.6
4.1 Apply a 10 mVrms, 2KHz signal to the left and right Music A input.
4.2 Measure the Speaker output. Should be 290 mVrms (+54mVrms/ - 46mVrms).
5. Frequency Response
5.1 Apply a 10 mVrms, 2KHz signal to the
left and right Music A Input.
5.2 Reference a dB meter to the Speaker output and set level to 0 dBr.
5.3 Change the signal to 12.5 KHz.
5.4 Measure the left and right Speaker output. Should be 5.1 dBr (
± 2.0 dB).
8.2 Measure the left Speaker output. Should be Note: Repeat this procedure for the right channel.
19
≤ 10 mV.
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