3-Way Active Loudspeaker

3_way_active_lsp_crossover.gif (13294 bytes)

After the 2-way active loudspeaker circuit, give a complete electronic section circuit of one 3-way active loudspeaker. The speakerís choice will become from you, because the particular circuit has the driving possibility all almost trade loudspeakers. The choice that made in the crossover stage, is a 3-way crossover [Butterworth] with cut off -point frequencies 200HZ and 3500HZ, with slope -12dB/oct. These frequencies can change and adapted in your own speakerís choice, using the calculation types of Fig.5. Exist the possibility is used other circuit crossover, as the circuit of 3-way active crossover with slope -24dB/oct. The circuit crossover does not exist above in main PCB, but is contact with this via the plug J2A that is applied above in the J2B. This can become if in the place of J2A itís placed a pinhead with 8 pin and PCB crossover put on above main PCB in form sandwich. It can however be placed in other point and with a flat cable to transport the signals and the voltages from J2A in the J2B. Power supply for Ī 15V of the crossover circuits itís found in main PCB. A point that I want to highlight is with regard to various in the calculation values precision and real values of resistors and capacitors. Itís good, if the component value does not exist in standard value to select a combination that us will give value near in theoretical and simultaneously to do the same and in the other loudspeaker, in order that the divergence is same. In the drawing exist parallel combinations resistors, and somebodyís from these are not used if they do not need. With the TR1-2 we adjust the level of high and mid speakers, if it needs.

Part List [Fig.1]

R1=47Kohms R19-20=47ohms C17-18=47uF 25V
R2=1Kohms C1=2.2uF 63V MKT TR1-2=47Kohms trimmer
R3=4.7Kohms C2=220pF IC1=TL071
R4-11-13-15-17=NC C3-4-11-12=100nF 63V MKT IC2-3=TL072-NE5532
R5-6=12Kohms C5-6-9-10=10nF 63V MKT J1=2pin conn. 2.54mm pin step
R7-8=120Kohms C13=6.8nF 63V MKT J2A=8pin conn. 2.54mm pin step
R9-10=220Kohms C14=3.3nF 63V MKT or 8 pinhead 2.54mm pin step*
R12-14=10Kohms C15=33nF 63V MKT
R6-18=33Kohms C16=18nF 63V MKT All Resistors is 1/4W 1%

Typical specifications

Input sensitivity

1Vrms

Input impedance

47K

High Pass filter

20HZ-:-200HZ

Band Pass filter

200HZ-:-3500HZ

Low Pass filter

3500HZ-:-20KHZ

Slope

-12dB/oct

3_way_active_lsp_protection.gif (21482 bytes)

The protection circuit from DC voltages [Fig.2] and  delay connection the speakers is the same with what exist in 2-way active loudspeaker where exists and the relative description. They exist certain various, as has been added a detection stage of continuous voltages and a relay [RL2]. The contacts of RL1 connect the speakers the high and mid frequencies, the two contacts of RL2 are connected at the parallel and connect the speaker of low frequencies in the exit of IC7. Here exist also the stage of Ī 15V supply for the crossover and suffices for each choice of crossover circuit.

Part List [Fig.2]

R1=470ohms 1W C4=10uF 25V IC1=4093
R2-3=1Mohms C5=1uF 25V IC2=7812
R4=22Kohms C6=4.7uF 25V IC3=7815
R5-21=33Kohms C7-8-10-11-13-14=33uF 63V IC4=7915
R6-8-16=15Kohms C9-12-15=22uF 16V Q1-2=BD678
R7-9-17=56Kohms C16-17=2200uF 25V Q3-4-5=BC550C
R10-23-18=56Kohms C22-23=10uF 25V RL1-2=12V RELAY G2R2 [OMRON]
R11-12-19=10Kohms D1-2-3-4=1N4002 J2B=8pin conn. 2.54mm pin step
R14-15-20=3.9Kohms D5=8.2V 1W Zener J3B=3pin conn. 2.54mm pin step
R22=1Kohms D6-7.....26=1N4148 J8A-B=2pin conn. 2.54mm pin step male-female
C1=100uF 25V D27=Led 5mm
C2-3-18-19-20-21=100nF 63V MKT BR2=BRIDGE RECT. 80V 1.5A All Resistors is 1/4W 1-5%

3_way_active_lsp_power.gif (30880 bytes)

In the Fig.3, exist the circuit of power amplifiers that drive the corresponding speakers. The choice are also here the STK4044XI of SANYO with output power roughly 100W each one, power that consider that is very good for the drive the majority of speakers of trade, in high levels. The sound quality that produces is very good. The type choice with clue XI became because it has better and more modern internal designing, as regards types II and V. It can used also other types [ B and V] without exists some problem. Filters RLF1Ö3 are made by a resistor 10R 3W that to around her we wrap roughly 30 coils in three layer, wire from cupreous insulated with diameter 1mm. The capacitors C66Ö. 69 are placed above in main PCB and near in the power amplifiers.

Part List [Fig.2]

R23-33-43-32-42-52=1Kohms RLF1...3=FILTER* See text C32-46-50=1nF 63V MKT
R24-34-44=47Kohms C24-38-52=330pF C33-37-47-51-63-65=100uF 63V
R25-26-35-36-45-46=100ohms C25-39-26-40-54=1uF 63V MKT C34-48-62=220uF 25V
R27-37-47=1Kohms C53=2.2uF 63V MKT C35-36-49-50-61-64=10uF 63V
R28-38-48=0.22ohms 5W C27-28-42-56-41-55=100pF C66-67-68-69=15000uF 63V
R29-39-49=4.7 ohms1W C29-43-57=100pF IC5-6-7=STK4044XI* See text
R30-40-50=56Kohms C30-44-48=15pF F2-3=Fuse 5A Fast 5X20mm+PCB case
R31-41-51=10Kohms C31-45-59=100nF 100V MKT J4A-5A-6A=2pin conn. 3.96mm pin step

Typical specifications

Input sensitivity

1Vrms

Input impedance

47K

Output Power  (0.1% THD)

100W/8 ohm per Band

Power Supply

Ī53V

Block Diagram

3_way_active_lsp_block.gif (16806 bytes)

In the Fig.4, appear a big part of various stages and connections between them. As it appears the speakers are placed in suitable wooden box. In his rear part of box and on a leaf of aluminum are placed the power transformer T1, the power bridge rectifier BR1, the switch S1, the main power plug JF1, fuse F1, the RCA plug JF2 and the indicative led D27. Transformer T1 has two outputs A=2X38Volts and B=2X15Volts. Bridge BR1 clinching above in aluminum so that itís frozen. On a big heatsink clinching the IC5-6-7. In plug JF2 enter the acoustic low level signal from the preamplifier exit. Good itís the crossover PCB itís found far by the T1 transformer.

Part List [Fig.2]

T1=110-230Vac||A=2X38V  >350VA JF2=Female RCA Jack MID=MIDRANGE 8 ohms
                        B=2X15V     30VA F1=FUSE 1.2A SLOW+CASE WOO=WOOFER 8ohms
BR1=BRIDGE RECTIFIER 400V 35A S1=2XON-OFF 15A Switch
JF1=3pin male supply jack TW=TWEETER 8R

Filter_butterworth_12dB.gif (5974 bytes)

Fig.5--Crossover calculation

 

Sam Electronic Circuits 9/02