LH003Wideband two-pole high-pass filter

The circuit provides a 10MHz cutoff frequency. Resistor R3 ensures that the input capacitance of the amplifier does not interact with the filter response at the frequency of interest.

Digitally tuned low power active filter

This constant gain, constant Q, variable frequency filter provides simultaneous low-pass, bandpass, and high-pass outputs with the component values shown, the center frequency will be 235 Hz and 23.5 Hz for high and low logic inputs.

TL081 Tunable notch filter

This narrow-stop-band filter can be tuned by the pot to place the notch at any frequency from 45 to 90 Hz. It attenuates power-line hum or other unwanted signals by at least 30 dB Because the circuit uses wide-tolerance parts, it is inexpensive to build.

SSM2044P Voltage Controlled Filter

At this circuit the SSM2044 IC is used, a 4 pole voltage controlled filter designed for electronic music applications. On-chip voltage control of resonance allows direct and easy interfacing with programmers and controllers. The IC features extended control range, low noise, and high control rejection. The filter can also be used as a low distortion sinewave oscillator.

NE602 Voice Scrambler/Descrambler

This circuit uses an NE602 as an inversion mixer. U2 is set to run at about 2.5 to 3.5 kHz. U3 drives a loudspe

XR-13600Universal active filter

The circuit as shown gives the bandpass operation the transfer function calculated from FBP(s) = where = 1 + s/Qo>0 + s2/w02. The cut-off frequency, 0, and the Q-factor are given by 0 = g/C and Q = gR/2 where g is the transconductance at room temperature. Interchanging the capacitor C with the resistor R at the input of the circuit high-pass operation is obtained. A low-pass filter is obtained by applying two parallel connections ctf R and C as shown in Fig. 2. The low-pass operation may be much improved with the circuit as given in Fig. 3.

Subwoofer music system

What is a subwoofer think many people know, but not everyone knows the true meaning of the word. Subwoofer - woofer reproducing frequencies below those that reproduce the work in conjunction with him broadband speakers. Consider how the subwoofer is integrated into the audio system.

System without a subwoofer. 

Initially there is a stereo signal source output (player CD, DVD, etc.). (I will talk only about the stereo recording, because of their absolute majority.) So this stereo signal is input to a stereo amplifier and its output signal is amplified by broadband speakers. With this implementation, the sound channel signal passes through a minimum number of components, and in the most pure form is served in the SS.

System with subwoofer. 

There are different options.

Stereo signal is fed to a stereo amplifier and subwoofer filter thus comes full on AC signal source and the subwoofer comes LF component of the signal from both channels.

Stereo signal is fed to the subwoofer filter, which separates it into two bands LF and MF / HF. With filter MF / HF signal is input to the amplifier front stereo speakers SAT and LF signal is input to the subwoofer amplifier. In general there are other options but they all boil down to the fact that the front speakers are fed either a full range signal or MF / HF component.  So in the first case is meant to use as front speakers powerful broadband systems, and the subwoofer is used as additional support for the front at the lowest frequencies. In the second case as the front speakers do not apply SAT large size and power, and low signal spectrum is reproduced only subwoofer. This approach enables us to create a system featuring a wide frequency range and low price is not large dimensions. In such systems do not bypass the subwoofer for how any suitable frequency range of the system as a whole. This solution is typical for budget systems are not high.

Now let's look at what gives us the use of a subwoofer in your music system. 

Adding a subwoofer to your system can significantly increase its dynamic range, its lower cutoff frequency, a higher level of volume without distortion, as in the case of an active subwoofer improve playback MF / HF by offloading stereo amplifier for the front speakers, and speakers themselves. Additional amplifier and woofer system can increase the maximum sound pressure level, and the removal of the LF signal from the front improves midrange sound, because Woofer does not oscillate with a large amplitude, and operates at a lower power level signal, clearly and not purely practicing greater levels of MF and HF signals.

And now let's look again. (Bucket of tar) 

Practice shows that the use of a subwoofer music system often reduces the quality of the sound. This is possible with the poor quality of the subwoofer, or it is not properly configured to work in a particular system, or what he intended to play every bass effects, explosions, etc.systems for DC transmission and not subtle shades of music.

Now let's think about why this is happening? 

To begin with it is worth noting that the use of a subwoofer always brings in additional electronics tract. Not the fact that the filter of the subwoofer is a high quality, it will make more noise and distortion to the original signal. But this is not the worst. 

Quality subwoofer can be initially low. You can certainly suggest the use of high-quality subwoofer, but there are very few, and they cost a lot of money. Most on the market subwoofers are dull, sluggish, boomy bass. They are clearly oriented to application in theater systems as a source of low frequency noise, and Bukhov Bach. This sound is very difficult to be heard is a clear height of individual notes (usually it looks like a bass boom on one note) on these subwoofers bass sound indistinguishable from the sound of bass. Very rare models differ musicality, high articulation, clarity of bass. While broadband quality outdoor speakers mostly possess such qualities to the full.

There is also a very serious problem of matching the front speakers with a subwoofer. The sound of the lowest sounds reproduced subwoofer may differ in character from the middle and lower sound upper bass front speakers. The result is a strong homogeneity of the sound is not the low frequency range. That is why it is imperative a coordinated subwoofer usually subwoofers should be used from the same family as the broadband speakers, and certainly one manufacturer. This greatly increases the chances of finding the same sounding pair.Naturally that the application of quality broadband speakers such problems simply do not.

The problem of reconciling the sound level of the front and the subwoofer is solved easily, but many exceed the level of the subwoofer above optimal, without noticing. This sound quickly tires, and do not know everything on what is happening. In qualitative broadband speakers, this problem is solved by itself, their design based on the maximum flat frequency response. 

We should not forget the problem of phase matching of the subwoofer with the front. On some subs have phase control, which partially solved the problem, but many cheaper models provided similar adjustments. And not all users can precisely adjust the phase of the signal, while clearly noting the difference between well-tuned subwoofer and tuned at all.

Just filling space subwoofer deep powerful bass, can provoke a resonance phenomena, very spoiling sound. This is manifested in the higher volume of individual notes in mumbling, sluggish and not dynamic, not a clear sound. Therefore it is extremely important to position this source LF energy. You can not just throw subwoofer in a corner and hope that he's accustomed. In a system with two or more sources of bass this problem easier solved by correct positioning systems not only space but also with respect to each other. 

All this is compounded by the fact that many people tend to install the excessive level of the subwoofer, so the sound is "more powerful bassist, cooler" and even then it is necessary to hear the work order for which they were paid not small money. Highest subwoofer will compliment what is its contribution to the sound is not audible on the line, he must harmoniously complement the front speakers sound without attracting attention. Only in this case it does not spoil the picture of the sound system.

CONCLUSION: Rare subwoofer does not impair the overall picture of the sound system, having a good, dense, collected, accurate, clear, resilient, fast bass, good sound with broadband agreed upon by the AU.

Now let's think, and whether to bathe with subwoofer choice for your system, overcoming problems. This will require a lot of time for not hasty careful, thoughtful otslushivaniya huge number of sets of speakers / subwoofer. Most records are not really in the frequency spectrum below say 40Hz. No such compositions certainly is, but not so much so that you can limit the requirements for the lower boundary frequency at 35-40 Hz. As for the necessary power here a lot has already been written, and I will not repeat myself, except to say that for a home system, even when listening to heavy rock songs in a decent size room enough power on the order of 100W. The most demanding music lovers who love to listen to classical pieces may need all 200W peak. But there are not many. And in most contemporary compositions dynamic range is lost after mastering, and he in such works do not quite large, and therefore do not need to twist the volume knob all the way to hear so quiet tone.

And what do we observe? Not that exorbitant demands to get to our ideal source LF energy. J Most floor systems not even the highest class easily meet the requirements. And many soundly designed broadband speakers from well-known brands, to easily surpass any subwoofer sound quality. So why need extra hemo ** th which inevitably appears in the application of Saba? By increasing the level of components in a pair broadband speaker / subwoofer certainly problems becomes smaller, but the quality of the speakers is increased by so much that it becomes just do not understand, why there wormed subwoofer? And in the case of floor-standing speakers of the highest class, all doubts about what you need assistance in the low frequency range just disappear by themselves. (For the most vocal opponents of my approach will give a concrete example (not advertising) Legasy focus 20/20. Those who have remained any doubts after reading this article, simply advise you to read the description, and even better test of these systems, and I'm just your doubts fade and you will be happy.

Original sourse cxem.net