Infinity 255a owner manual I N S T A L L A T I O N c o n t i n u e d, S E T T I N G D B O

I N S T A L L A T I O N ( c o n t i n u e d )

4.Using the Weco 5-pin connector, connect a blue wire from the source unit’s remote connection to the REM terminal. Depending on polarity requirements (see Figures 1 through 3 on pages 3 and 4), connect speaker wires from

the subwoofer(s) to the L and R (+ and –) terminals, as required by your system plan.

5.Make sure the wires are firmly seated in the Weco 5-pin connector and that each screw is completely tightened. Insert the wired Weco 5-pin connector into the SUBWOOFER socket (on the amplifier’s rear panel). Press it in until it stops.

6.Using Weco 4-pin connectors, connect speaker wires from the front and rear speakers to the amplifier. Depending on your system plan (see Figures 1 through 3 on pages 3 and 4), match the polarities on the L and R (+ and –) terminals.

NOTE: In 3-way applications, the rear amplifier provides bandpass channels to drive midrange or midbass speakers.

7. Make sure the wires are firmly seated in each Weco 4- pin connector and that each screw is completely tightened. Insert the wired Weco 4-pin connectors into the FRONT and REAR sockets (on the amplifier’s front panel). Press each one in until it stops.

8.Connect RCA cables from a source unit to the L /R, FRONT/REAR INPUT jacks. If the source unit has subwoofer outputs, also connect a pair of RCA cables from those jacks to the SUB INPUT jacks and set the SUB INPUT switch to EXT (see Figure 7).

S E T T I N G T H E C R O S S O V E R S . . .

1.To use the Kappa 255a in a front/rear system, set the CROSSOVER controls to frequencies recommended by the speaker manufacturer (see Figure 7). If the value is unknown, set the control midway.

2.For a 3-way system, set the OUTPUT and REAR INPUT switches to create the appropriate bandpass filters (see Figures 2 and 3 on pages 3 and 4).

S E T T I N G I N P U T S E N S I T I V I T Y . . .

Initially, turn the front and rear input sensitivity GAIN controls to their minimum (counter-clockwise) positions (refer to Figure 7).

1.Reconnect the (–) negative lead to your vehicle’s battery. Apply power to the audio system and play a favorite music track from CD or tape.

NOTE: After the source unit is on, green LEDs (on the top panel) will illuminate, indicating the amplifier is on. If not, check the wiring, especially the remote connection from the source unit. Also refer to “Troubleshooting” on the next page.

2.On the source unit, increase the volume control to maximum position. Slowly increase the Front and Rear GAIN controls (clockwise) towards three o’ clock and, at the same time, listen to the quality of the reproduced sound. At some point, you’ll hear distortion on the music peaks. Stop the adjustment and turn it back slightly.

S E T T I N G D B O . . .

Dynamic Bass Optimizer (DBO) is a new approach to enhancing low-frequency reproduction in a vehicle. Conventional bass boost controls add bass at a fixed frequency and cause the amplifier to consume considerable power. DBO conserves valuable power at the lowest frequencies and allows you to adjust the level and “character” of the bass sound, instead of just the amount of boom.

Since a subwoofer in a tuned box is given to overexcursion below the tuned frequency, set the FREQ control below the box’s resonant (tuned) frequency (see Figure 8 on the next page). Power typically wasted in this region will now be conserved and instead be available for frequencies the enclosure will reproduce. Use the Q control to boost the bass at the set frequency by as much as 12 dB (at MAX position – see Figure 8 on the next page).

For sealed enclosures, use DBO to enhance the output so it sounds more like a tuned box. This is a result of 12 dB of rolloff being added to the enclosure’s rolloff and a flattening

x15

x1

32Hz

320Hz

LP

HP

FLAT

FRONT

C	9V		G
			A
R
			I
O	.25V
S			N
S
O			32Hz
V		M
E	BR
R		O	320Hz
O	ST	D
		E	LP
U

THP

UFLAT

	REAR			SUBWOOFER
C	9V		G	9V	G
			A		A
R
			I		I
O	.25V			.25V
S			N		N
S				20Hz
O
V		M	D FREQ
E	BR
R		O		80Hz
	ST	D	B
O				MIN
		E
U			O	Q
T
P
U				MAX
T			INT		SUB
			EXT		INPUT
			X	32Hz
			O		60
			V

of frequency response (at the curve’s knee) when Q is boosted.

For infinite baffles, set the FREQ control to the speaker’s Fs value (to keep the subwoofer from trying to create bass below the resonant frequency) and adjust the Q control according to personal taste.

I N S T A L L I N G T H E C O N T R O L C O V E R . . .

After wiring and testing the Kappa 255a amplifier, install the control cover using the enclosed machine screws to deter tampering and help seal out dust.

NOTE: Do not over-tighten the machine screws. Doing so may

50W X 4

+

200W CLASS D

DIGITAL SUBWOOFER

AMPLIFIER

E		Hz
R	320Hz
EXT		REAR
FRONT LP		INPUT

crack the cover.

Figure 7. Kappa 255a controls for crossover, input, output, and DBO (Dynamic Bass Optimizer).

Owner’s Manual/Installation Guide – 7