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OPERATION

Setting the Controls

Turn the Power On

4. Turn on the entire audio system and play any music

source.

5. Turn the Volume control to its mid position. If no sound

emanates from the subwoofer, check the AC line cord and

input cables. Are the connectors on the cables making proper

contact? Is the AC plug connected to a “live” receptacle?

Adjusting the Volume

6. Set the overall volume control of the preamplifier or stereo

to a comfortable level. Adjust the subwoofer's Volume control

until you obtain a pleasing blend of bass. Bass response

should not overpower the room but rather be adjusted so

there is a harmonious blend across the entire musical range.

Many users have a tendency to set the subwoofer volume too

loud following the belief that a subwoofer is there to produce

lots of bass. This is not entirely true. A subwoofer it there to

enhance bass, extending the response of the entire system

so the bass can be felt as well as heard. However, overall

balance must be maintained; otherwise, the music will not

sound natural. An experienced listener will set the volume of

the subwoofer so its impact on bass response is always there

but is never obtrusive.

The Crossover Frequency Controls (BU120

7. The Crossover Frequency control sets the high-frequency

roll-off, adjustable from 50 to 150Hz. Where you set this

control depends on the low-frequency capabilities of your

satellite speakers, system placement, and other factors

affecting the mid-bass region. Turn the control UP

(clockwise) until you feel there is too much mid-bass

information (around 100Hz), then back the control down a bit

until that area sounds more natural. To hear more low bass,

turn the Crossover Frequency control DOWN a bit and the

Volume control UP by about the same amount. This will

increase low bass while leaving the mid-bass sounding the

same as it did before the adjustment. To reduce low bass

without changing midbass, turn the Crossover Frequency

control UP and the Volume control DOWN. Switch the Phase

switch between “NOM” and “REV” positions while listening to

music. The selection that sounds the best is the correct

adjustment for your system.

Room Placement

8. The room placement of the subwoofer is the most critical

aspect of its installation. It will be necessary for you to try

various locations in your listening room before you choose

the final location. Some possible starting points include:

behind the right channel satellite speaker, along the back

wall between the satellites, along a side wall (but not too

close to a corner), or behind a couch or a chair.

In general, the closer the subwoofer is to wall and corners,

the greater the effect of low-frequency enhancement.

Experiment with the Crossover Frequency and Volume

controls in different locations until you are pleased with the

result you obtain from your particular application.

A Word of Advice

The Low-Frequency Roll-off and Volume controls may be

set anywhere within their rotation. However, it will be a most

unusual circumstance if you have to set the Volume control

completely clockwise. This may indicate an unbalanced

condition in your system (too much bass) or an especially

large room, or room placement may not be correct. Try

several other locations before concluding that the Volume

control must be set at maximum.

A Word About Tone Controls

The tone controls on your electronic components

(preamplifier, receiver, etc.) should be used with the utmost

discretion. Excessive boost can create severe power

demands on your power amplifier. Maximum bass boost

can create a demand for literally hundreds of watts in the

bass region, whereas in the “flat” position, or with the tone

controls switched out of the system, your average listening

level may be impressively and realistically loud at less than

10 watts. The remaining power capacity required is on

reserve for power peaks on sharp transients and powerful

crescendos.

1 1

Amplifier/Subwoofer

BU-120/HTS-20

1. Initially set the subwoofer's Volume control to the minimum

position.
2.  BU120 - Initially set the subwoofer's Crossover Frequency

control to 12 o'clock.

HTS-20 - If you are using a receiver or surround processor

containing a Dolby Digital and/or DTS decoder, set the 

crossover bypass switch to "On". If you are using a stereo

or Dolby Pro logic receiver, set this switch to "Off"; this places

the preset roll-off crossover frequency point at 100Hz.

3.  Set the subwoofer's Phase switch to the "0" position.

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Summary of Contents for HTS-20

Page 1: ...Infinity Systems Inc 250 Crossways Park Drive Woodbury N Y 11797 1 800 553 3332 A Harman International Company Rev G 6 2001 BU 120 HTS 20 Powered Subwoofer SERVICE MANUAL...

Page 2: ...re due to internal cabinet pressure and vibration C6 10uF 50V electrolytic radial BU120 and HTS 20 rev A only S53AMI or CN1 Power output module Use only factory replacement Faceplate Faceplate Use onl...

Page 3: ...5 TECH TIPS 16 BU 120 HTS 20 PACKING CABINET ASSEMBLY 17 BU 120 HTS 20 AMPLIFIER ASSEMBLY EXPLODED VIEW 18 BU 120 HTS 20 rev A PCB revision 3 52 Component Side Trace 20 BU 120 HTS 20 rev A PCB revisio...

Page 4: ...minal Freq 1 input driven Line Input 63 mVrms 2dB To Rated Power Vol Max 1 input driven AP source Z 600 ohms Speaker Hi Level Input 4 8 Vrms 2dB To Rated Power Vol Max 1 input driven AP source Z 25 oh...

Page 5: ...zero ohms source impedance Signal Present LED Yes Bi Color LED green signal red no signal Signal Present Input Freq 100 Hz functional Nominal 200uF Series Cap on PCB Signal Present Level 35 mV functi...

Page 6: ......

Page 7: ...of each stereo pair of leads to the preamplifier s left and right outputs and connect the other end to the corresponding left and right LOW LEVEL INPUTS 1 on the subwoofer If you are using a tube pre...

Page 8: ...air See Figure 3 Figure 3 Use this method when using a single subwoofer output or two subwoofers The subwoofer may be connected to your system using the HIGH LEVEL INPUTS 4 on the plate located on the...

Page 9: ...ting one subwoofer to satellites Depending on whether you are using one or two subwoofers connecting your satellites can be accomplished in one of two ways If you are using a single subwoofer with a p...

Page 10: ...trol depends on the low frequency capabilities of your satellite speakers Adjust this knob to the lowest frequency that you satellite speakers were designed to reproduce refer to Operation step 7 1 0...

Page 11: ...djustment for your system Room Placement 8 The room placement of the subwoofer is the most critical aspect of its installation It will be necessary for you to try various locations in your listening r...

Page 12: ...NOTE When testing the BU120 HTS 20 amplifier a load must always be connected to the output terminals whether the woofer or a 4 to 8 ohm resistive load...

Page 13: ...1 3 Amplifier Subwoofer BU 120 HTS 20 BU 120 HTS 20 POWER AMP MODULE TESTING FLOW CHART HTS 20 rev A only...

Page 14: ...should be able to remove the amplifier far enough out of the cabinet to service it without removing the woofer wires 4 Locate the Power Amp Module it is the large gray component with a metal case On...

Page 15: ...47 1 4W resistor R23 20k 1 2W resistor used only on models BU120 HTS 20 revA BU80 HTS 10 BU120 HTS 20 General reference for location only not all parts or designators may conform to these drawings FO...

Page 16: ...e all knobs nuts and Philips screws from the outer control section of the amplifier faceplate 5 Locate the sealed cover on the inside of the amplifier faceplate see illustration the bead of adherent m...

Page 17: ...12 WOOFER BU 120 HTS 10 rev A 200300 HTS 20 rev B 090 312000 000 CABINET NOT FOR SALE AMPLIFIER ASSEMBLY SCREWS 8 TOP STYROFOAM RAIL PADS 2 per carton 200360 PLASTIC BAG BOTTOM STYROFOAM RAIL PADS 2...

Page 18: ...er Subwoofer BU 120 HTS 20 BU 120 HTS 20 AMPLIFIER ASSEMBLY EXPLODED VIEW E E D D C C B B A A 7 7 6 6 5 5 4 4 3 3 2 2 1 1 BU 120 HTS 20 Amplifier Assembly Exploded View 6 20 18 6 1 19 20 18 19 20 6 HT...

Page 19: ...and HTS 20 rev A ONLY 12 083 041802 017 Power cord 2 conductor SAFETY PART 1 HTS 20 rev B ONLY 13 80106 Fuse PCB complete with connectors SAFETY PART 1 BU 120 and HTS 20 rev A ONLY 13 011 080203 000 F...

Page 20: ...2 0 Amplifier Subwoofer BU 120 HTS 20 Revision 3 52 Component Side Trace Layer 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G BU 120 HTS 20 rev A PCB Component Side Trace...

Page 21: ...2 1 Amplifier Subwoofer BU 120 HTS 20 Revision 3 52 Solder Side Trace Layer as viewed through the board 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G BU 120 HTS 20 rev A PCB Solder Side Trace...

Page 22: ...2 2 Amplifier Subwoofer BU 120 HTS 20 BU 120 HTS 20 rev A PCB Component Side Trace Revision 3 53 Component Side Trace Layer 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G...

Page 23: ...2 3 Amplifier Subwoofer BU 120 HTS 20 BU 120 HTS 20 rev A PCB Solder Side Trace FANCY 3 53 Solder Side Trace Layer as viewed through the board 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G...

Page 24: ...38 20K 0 25W 1 metal film 1 Crossover 40425 50k 1 4W 10 Double Log Pot 1 Level 40402 5k 1 4W 10 Single Linear Pot 1 Capacitors C1 2 30706 4700uF 50V 4 Electrolytic Radial 2 Safety part C3 30514 47nF 5...

Page 25: ...All AC powered test instruments meters oscilloscopes etc must have a floating ground i e be connected to an isolation transformer 3 Align and position the Amp Module before soldering 4 Attach the amp...

Page 26: ...2 6 Amplifier Subwoofer BU 120 HTS 20 BU 120 HTS 20 rev A SCHEMATIC 1 of 2 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G BU 120 HTS 20 Schematic 1 of 2...

Page 27: ...fier Subwoofer BU 120 HTS 20 5 5 4 4 3 3 2 2 1 1 A A B B C C D D E E F F G G BU 120 HTS 20 Schematic 2 of 2 See page 15 Service Bulletin INF2000 01 BU 120 HTS 20 rev A SCHEMATIC 2 of 2 Later revs valu...

Page 28: ...esistor 220K 1 4W J R122 1 020 270697 120 Carbon resistor 270K 1 4W J R116 1 020 300497 120 Carbon resistor 3K 1 4W J R16 1 020 330497 120 Carbon resistor 3K3 1 4W J R33 1 020 330597 120 Carbon resist...

Page 29: ...0697 120 Carbon resistor 100K 1 4W J Taping R2 1 020 100797 120 Carbon resistor 1M 1 4W J Taping R10 1 020 220397 121 Carbon resistor 220R 1 4W J Taping R6 1 020 330497 120 Carbon resistor 3K3 1 4W J...

Page 30: ...P N 052000W1G Red Wht JK102 1 072 040032 000 Terminal P 3 96 3P CON3 1 072 040039 000 Terminal PCB TYPE PC205 t 0 8mm T205MA J101 102 2 074 030002 000 Toggle sw P NL101 sw101 102 2 091 000143 000 EMI...

Page 31: ...31 HTS 20 REV B CIRCUIT BOARDS...

Page 32: ...32 HTS 20 REV B CIRCUIT BOARDS cont...

Page 33: ...C119 033u R122 220K R129 47K D121 1N4148 10K 1 4W R124 R126 1K5 1 4W 0033u C130 R130 22K 68K R5 10K R6 R2 820 5W R1 820 5W 4 7R R4 C6 1u 63V 4700u 50V C2 4700u 50V C1 D4 15 3 D3 15 3 C7 1u 6 2V 1N5234...

Page 34: ...3 2 IRF530 Q2 1 3 2 Q3 IRF530 10 R11 1 2 U2 A 74HC14 R12 10 13 12 74HC14 U3 F 1 2 U3 A 9 8 U3 D 6K8 R1 C10 100U 16V R1330K FB 820 R14 ZD2 15V ZD1 15V IN 15V S D 15V 6 5 7 LF353 U1 B C8 1000p 3 4 U2 B...

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