The acoustic spectrum is extended by very low frequencies 20Iz and reaches as the 20000Iz in high frequencies. In the low frequencies is degraded the sense of direction. This reason us leads to the utilization speaker for the attribution of very low frequencies. The manufacture that to you we propose distinguishes these frequencies, in order to him we lead to the corresponding amplifier. The acoustic filters are met in various points in the sound systems. The knownest application they are the filters baxandal for regulating tone low and high frequencies and filters crossover where the acoustic region is separated in subareas, in order to it leads the corresponding loudspeakers. The application that to you we propose is a simple filter of region that limits the acoustic region (20-20000Hz) in the region 20-100Hz.

With the manufacture that to you we propose you can make a active filter in order to you lead a loudspeaker of very low frequencies. With this you will place one bigger speaker between the HIFI speakers of you. In order to you have a complete picture of sound you will need also the corresponding amplifier. In the entry of circuit you will connect the two exits of preamplifier or the exit of line of some preamplifier. The circuit of manufacture allocates a exit in order to is led means of circuit of force subwoofer. If for some reason you do not have space in order to you place the third speaker in space of hearing, then you can select smaller speaker. The output will depend from the type of music that you hear.

Theoretical circuit

In first glance we see three different circuits that are mainly manufactured round two operational amplifiers. This circuits constitute mixed, amplifier with variable aid and a variable filter. The manufacture end needs a circuit of catering with operational tendency of catering equal with ±12. the operational amplifiers that constitute the active elements for this circuits of are double operational type as the TL082 and NE5532. The operational these amplifiers belong in a family provided with transistor of effect of field IFET in their entries. Each member of family allocates in their circuit bipolar transistor and effect of field. This circuits can function in his high tendency, because that they use transistor of high tendency. Also they have high honor of rhythm of elevation (slew rate), low current of polarization for the entries and are influenced little by the temperature. The operational these amplifiers have breadth of area unity gain bandwidth 3MHz. A other important element for their choice is the big reject of noise, when this exists in the line of catering.

The price of reject is bigger than 80dB, their consumption is small, from 11 until 3 mA. They are internally sold in nutshell with eight pins and allocate two operational amplifiers, In the same line in nutshell 14 pins they incorporate four operational, In the trade they are sold with code TL074, TL084 and TL064, In nutshell with eight pins they are sold operational amplifiers TL061 TL071 kajTL081. In the manufacture we used the TL082 that has two operational. First operational from the TL082 it works as amplifier and mixed for the two channels, In his negative entry he exists one small mixed with two resistances. A potentiometer in this rung determines the aid of circuit. In the point this left winger and the right channel of preamplifier they are added means of two resistances. En continuity the operational strengthens signal with aid made dependent from the price that has the potentiometer.

The place of runner is proportional with the aid of circuit. The second operational amplifier is the filter of manufacture. The filter of is acoustic frequency of second class and he is made with the materials that are round the operational amplifier. The filter of is low passage with variable frequency of cutting off. This frequency can be altered and take prices from very low frequency the 30Hz or still exceed 150Hz. The frequency of cutting off of filter depends from the prices that have the elements of circuit. Altering the values of elements we can have frequency of cutting off 150Iz, 130Iz, J00Iz, 7Ïz, 6Íz even 3Íz, this prices they can be achieved with the simple rotation of double potentiometer. The circuit of filter has been made around one operational’ that it has completed TL082 that is double operational amplifier. In the exit of filter we will link the plug of expense where is connected the amplifier. In the exit of circuit is presented, the limited as for the breadth of frequencies, signal that we apply in the entry of circuit.

Manufacture

Parts
R1 = 39 Kohm
R2 = 39 Kohm

R3 = 47 Kohm
R4 = 10 Ohm

R5 = 22 Kohm
R6 = 4,7 Kohm

R7 = 22 Kohm
R8 = 4,7 Kohm

R9 = 10 Ohm
R10 = 220 Ohm

C1 = 39 pF
C2 = 0.1 uF

C3 = 0.1 uF
C4 = 0.2 uF

C5 = 0.4 uF
C6 = 0.1 uF

C7 = 0.1 uF
IC1 = TL064

Description
The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don’t build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this case, you should directly connect the signal to C7.

Circuit diagram

Layout of board

printed PCB

Parts
R1=15k C1= 3k9 U1= TL081
R2= 150k C2= 100u D1= 1N4148
R3= 2k2 C3= 22u CN1= SIL6
R4= 820 C4= 4u7
R6= 10k C5= 470u
R7= 10k C6= 10u
P1= 1M C7= 100n
C8= 47u UNIPOLAR

Cross-over they are netting usually with passive materials that have aim to separate a region of frequencies in smaller. Cross-over the manufacture that to you we offer it separates the acoustic region in two sub areas in order to we lead two loudspeakers for the high frequencies and for low.

Cross-over they are essentially for the operation of combination of loudspeakers. Without them, two things happen: on one side are led all the frequencies simultaneously to different loudspeakers and otherwise is consumed pointlessly force in loudspeakers that cannot him attribute rightly. Cross-over depending on the number of loudspeakers that leads they are distinguished in two streets and three streets, even if they can result also complexes. The each region is figuratively named street, through which will pass the corresponding region of frequencies in order to it leads the corresponding loudspeaker.

The simpler system is that of two streets. In that acoustic region it is separated in two sub areas with two filters: one of low passage and one high. The filter of low passage leads the loudspeaker for the low frequencies and the filter of high frequencies the loudspeaker for the high frequencies. The loudspeaker for the low frequencies is known as woofer and the loudspeaker for the high frequencies as tweeter.

The loudspeakers are distinguished by various characteristics that him make distinguish between them. That characteristics that us interest for the manufacture that we make, are their complex or more simply resistance and diagram that us gives the relation of attribution of sound as for frequency (sensitivity).

The resistance of loudspeakers is characterized in a frequency depending on the destination and their press. Loudspeakers are distinguished, as for the destination, in loudspeakers of low frequencies, woofer intermediate, mid-range and high tweeter. Their resistance in W is 4W, 8W and 16W. Cross-over that we present it is intended for loudspeakers 8W.

Theoretical Circuit

The theoretical circuit appears in form 1. The manufacture uses passive materials of mediocre dimensions. In order to you make a cross-over you need printed circuit. Observing theoretical circuit we see that it has a entry and two exits, In the entry connect the exit of amplifier and in the exits the loudspeakers. In the one the loudspeaker of high frequencies and in the other the loudspeaker of low frequencies. The way from the entry to the loudspeaker of high frequencies is not anything other, despite a filter of high frequencies. Respectively, the way to the loudspeaker of low frequencies is a filter of low passage. The filter of low passage consists by inductor L2 and the capacitor C2. The inductor is en line with the circuit and the capacitor at the same time with the loudspeaker.

The complex resistance of this elements changes, associates the price of frequency. The price of complex resistance of inductor of is proportional frequency and capacitor of reversely proportional frequency. As long as increase the frequency, the self-induction acquires bigger complex resistance and the capacitor smaller. This, in combination with their provision, prevents the high frequencies to reach in the loudspeaker. In the way of high pass filter to the loudspeaker of high frequencies the provision of elements is reversed. En line we place capacitor, a C1 and at the same time inductor L1. In this provision as long as is increased the frequency, is decreased the complex resistance of capacitor while his inductor that is at the same time with the loudspeaker is increased. As long as it increases the frequency, so much facilitates the capacitor the passage of frequencies and so much least it absorbs the inductor force from them.

Apart from the elements of filter in the circuit, existence resistances and capacitors that stabilise the behaviour of loudspeakers. An additional resistance, R3, offers a particular operation. This resistance is always shorts from a safety. If for some reason it passes big current, then is in danger is burned loudspeaker of the high frequencies. Rather the loudspeaker is burned the safety. Then is presented en line the resistance and is decreased the sound level.

Manufacture

In order to you make the manufacture you will need the PCB that appears in form. In this mount materially that exists in the theoretical circuit, according to form. The montage of materials will begin from the resistances and flowingly will place the capacitors and finally the self-induction. The inductors for the cross-over, if him you find in trade you cans him order from us. In order to you try the cross – over apply in the exit for the each loudspeaker a resistance 8W. In the entry you will connect a small amplifier with which you will strengthen the signal of acoustic generator. The generator him you will put it produces sine’ signal. Altering the frequency we observe the each expense in an oscillograph. If all have well, then when is increased the frequency and approaches the price 3,5kHz, the tendency in the exit for the loudspeaker of low frequencies falls and the other increases.

Parts
R1 = 10
C1 = 3,3 uF
L1 = 0,82 mH

R2 = 3,3
C2 = 4,7uF
L2 = 1,2 mH

R3 = 33
C3 = 10uF

R4 = 10