JBL SC305 User Manual

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Congratulations on choosing JBL Series loudspeakers. Their highly accurate, uncolored and balanced sound character will greatly increase your enjoyment of recorded music. JBL speakers are built with careful attention to detail, using only the highest quality materials. They will provide many years of excellent performance.

Speaker is the result of concentrated efforts to combine traditional JBL performance values with elegant contemporary appearance. Some of the engineering features of the SC305 are:

Smooth, extended response:

The 14mm Titanium Laminate dome tweeter, dual 5" polymer laminated cone drivers and carefully designed dividing network deliver the clear, crisp, quality sound reproduction needed to deliver the accurate, intelligible vocal information required by a center channel speaker.

High Quality Crossover Network: the computer-optimized dividing network employs up to thirdorder (18 dB per octave) crossover sections. JBL's use of high quality capacitors and low-loss/low-distortion inductors assures freedom from phase or amplitude distortions.



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To connect the SC305 to the center channel output of your AV receiver or amplifier, use two-conductor insulated wire. Your JBL dealer can recommend suitable cables, or you can buy wire at most hardware stores. We recommend #16 AWG wire as a minimum size. If your speaker is more than 30 feet (10 m) from your AV receiver or amplifier, use larger diameter wire. Connections are made at the terminals located on the back of the SC305 speaker. The terminals accept bare wire or dual banana plugs, either of which will provide easy, secure connections.

Preparing the hookup wire

1.First determine the distance between the most distant speaker.

2.Now make the hookup wires for both speakers this length, even if one loudspeaker is much closer to your amplifier than the other. This will help maintain proper signal balance.

3.Strip off 3/8" of insulation from both ends of each conductor.


4.Twist each set of thin wires into a tightly-bunched spiral.

5.At this point you need to identify a visual difference between the two conductors of each molded pair of speaker wire. Differentiating marks can be a different color wire (copper or "silver"); a strand of yarn in one conductor; thin, raised ribs on one part of the outer insulation; or a printed "+" marking on one of the insulators. It does not make any difference which of the two strands of wire go to (+) and (-) on the speakers and amplifier, as long as both speakers are connected identically. Push down on the button below the terminal and insert the wire, or the banana plug, through the hole (see Fig. 3).


Blk Red

(-) (+)




• •

AV Receiver

• • Center

(-) (+)

Fig. 3

The red terminal on the loudspeaker should be connected to the red or (+) center channel connection terminal on the AV receiver or amplifier, and the black to the black or (-). Connecting the loudspeaker in this manner ensures that it will be in phase; that is, work together rather than in opposition to the left and right channel speakers. Connecting loudspeakers out of phase will not damage them, but will result in less bass and poor imaging.

Using the controls on your center channel AV receiver/amp, adjust the center channel level (volume) control so that the sound from the center speaker is the same level at your normal listening position, as the sound from the left and right front speakers.


Thanks to its high efficiency, the JBL

SC305 loudspeaker will produce reasonable volume levels in a room of moderate size with very little amplifier power.

However, using a small amplifier to obtain the desired volume listening levels may lead to overdriving the amplifier. This will generate high distortion levels and may cause damage to your loudspeaker. For the best performance, an amplifier should be selected with an output rating that is greater than the maximum power that will be used. This margin of reserve power will ensure that the amplifier will not attempt to deliver more power than its design allows. However, the amplifier's power rating per channel must not exceed the maximum recommended amplifier power for that specific loudspeaker model. Please see the specification section for details. Following these guidelines will provide virtually distor- tion-free sound reproduction and long loudspeaker life.


The vast majority of new speaker "malfunctions" end up being traced to connections or switch settings. Check the following tips first, before requesting service.

No sound at all or very faint sound from the center channel speaker

1. Speaker wire has become disconnected.

2. One of the connections between sound source and AV receiver/amp is faulty or has become disconnected.

3. AV receiver/amp center channel mode not selected. Please select a mode that activates the center channel.

4. AV receiver/amp "audio direct" switch is activated. This switch should be off to activate the 5 speaker surround mode.

5. Sound source (VDP, VCR,CD,cassette deck, turntable) not turned on, not activated, not hooked up or not selected on AV receiver/amp front panel.

Speaker plays at low volumes but shuts off as volume is increased OR sound turns on and off intermittently

A few strands of speaker wire may be shorting out. Recheck the connections.

Recheck the impedance of the amp.



The grille is held in place by pins near the edges. To remove the grille, grasp it by both top and bottom edges and pull gently. To replace grille, re-position it carefully and press gently at the corners. Do not push on the center area of the grille.

The loudspeaker cabinet may be cleaned with a slightly damp cloth. To remove dust from the grille cloth, use a vacuum with a brush attachment. Spots may be removed with a commercial spot remover. Do not use any cleaners or solvents on the speaker drivers themselves.


Should your loudspeaker ever need service, return it to the JBL dealer from whom it was purchased. If for some reason this is impractical, in the United States, call 800- 336-4JBL for your nearest warranty station. Military personnel who purchased from authorized military outlets should return them to a similar outlet or contact:

ALA Associates Enterprises 985 Ponce de Leon Avenue Atlanta, GA 30306

Phone: 800-875-4252

FAX: 404-873-3592

If purchased outside the United States, contact your local distributor to make arrangements for repair service. Do not return products to the JBL factory without prior authorization.



High Frequency Dome Transducer

14mm Titanium Laminate

Low Frequency (High Polymer Laminate)


Crossover Frequency

2.7 kHz

Frequency Response (- 6 dB)

100 Hz to20 kHz

Sensitivity(1 Watt/1 meter)

87 dB

Nominal Impedance

8 ohms

Recommended Amplifier Power*

10 to 100 Watts

External Dimensions (HxWxD)

7"x 20"x 6-1/2"

External Dimensions (millimeters)


Weight (each)

15 lbs (6.8 kg)

Shipping Weight

18 lbs (8.2 kg)

*Undistorted continuous power per channel.






JBL continually strives to improve its products. New materials, production methods and design refinements are introduced into existing models without notice as a routine expression of our design philosophy. For this reason, JBL loudspeakers may differ in some respect from their published specifications and descriptions, but will always equal or exceed the original specifications unless otherwise stated.

JBL Consumer Products, Inc.

240 Crossways Park West

Woodbury, NY 11797

8500 Balboa Blvd.

Northridge, CA 91329

800 336 4JBL

Part No. 75993