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Studio Monitors PA Class

Before I tell you what studio monitors "PA Class" (the term of the author of the site) means, you should be acquainted with the scheme of multisystem sound signal amplification, a short (PA). PA term means increasing the volume or amplification defined as Professional Audio - That is a sphere of activity in which the studio monitors disappeared. Necessary condition of those sound amplifying system architecture is to completely exclude the passage of the signals on the head, which is not intended to reproduce such a signal. Standard passive switches have the following side effects:

  1. Even the most complex passive crossovers are not able to completely exclude the presence of the signal at the dynamic heads, which are not projected. They are structurally unable to reproduce such a signal because it is not inappropriate for them. For example, even the most powerful HF head will instantly burn out, if it receives a LF signal. In other words, the wide frequency signal always goes to all heads, although it has low amplitude after the frequency division bands points.
  2. Dynamic heads have a lot of areas of common frequencies around the points of signal division crossover. This leads to breaking the integrity of sound picture and distortion of the common frequency range during the playback. Therefore, it is impossible to manufacture passive acoustic systems which have more than four frequency ranges, cause that is how the entire frequency range is turned into a zone of shared frequency reproduction.
  3. In filter there are radio elements with reactive character power supply (inductance coils and condensers), that leads to the sudden appearance of parasitic current flows and the rapid increase of voltage during the filtration, division wide pass signals through them.
  4. Sophisticated high order crossover, not to mention the improved model with corrective notch links, have rapid fall of signal round the filtration points and can even align the frequency response. But these crossovers are very heavy load for an amplifier and lead to an increase in its level of distortion and require specialized technical solutions. These speakers have very poor sound quality, as in the filters gives rise to large phase delay between the speakers. Sound image in this case turns into a mess. The stereo effect and localization of sound images are very poorly expressed. This is due to the complex psychoacoustic nature of human hearing. If judged only by the amplitude-frequency response graph and characteristics decreasing of sound signal in the crossover, these speakers look very decent, but they sound very bad.
  5. The quality of the amplifier sound depends largely on the type and number of applied crossovers and number of bands in specified acoustic system model, because the parameters of the amplifier only measures and norms to a nominal active load. In other words, the same amplifier can run completely different when it is joined to various acoustic systems. Remember - testing the amplifier in audiophile magazines are performed only on one particular model of speaker and amplifier gets the best rating if it has most suitable reactive nature of the specific speaker loads.
  6. It decreases the damping factor of the amplifier, which is standardized to a certain nominal resistive load. At this point the low frequency sound becomes resounding and prolonged.

Systems of PA class do not have such disadvantage, because instead of a passive crossover they have active. They are made as separate device with its enclosures, power supplies and a variety of settings. Audio output device for audio playback (CD, DVD player, sound card) is connected to an active router, not the amplifier, as before. They have one pair of inputs (stereo) and few pairs of outputs for each frequency band, but these should be equal to or greater than that of the connected speakers. You don’t usually see the crossover with more than four frequency belt. The division of signal is performed using transistors. Active filters have variable frequency divisions with a certain step and a possibility of the slope signal reduction to 48 dB. It is very convenient because it allows the selection of the division points based on a hearing or on the results of distortion measurements, with a purpose to distribute a maximum efficiency range between drivers. It is necessary to regulate the volume levels for each input, which allows aligning levels of AFR drivers, if they have different sensitivities and phase control for each band to achieve in-phase work of drivers in the points section, which is especially important when using subs.

But such crossovers have their disadvantages, during the analog signal processing, the own interference, noise, distortion and reducing of the dynamic range recording are unavoidable. Particularly this effect is seen when using external models, with their own chassis, power supplies, connection cable length, the contours change settings and preamplifiers in front of each output. Nonetheless, this spurious contribution to the sound is very small and becomes critical only in the most expensive sound systems. This drawback can be eliminated using digital crossovers, working with the original digital form of signal and they have several great opportunities compared to their analog counterparts.

Now you only need to connect to the outputs of the crossover stereo amplifiers, one for each frequency band, and the amps sound drivers without any filters. Drivers will then operate only in strictly designated frequency bands and for the amplifier it would be almost linear load that will minimize the distortion of the amplifier.

Analyzing the above we can say that the PA amplification scheme differs from simple wideband with its complexity, and most importantly, a much higher price. The financial side issue is related mainly to the amplifier, because you should buy them as many belts in the acoustic system. However, the use of "branded" digital crossovers, their value may exceed even the very value of the amplifier. But that is a unique way of obtaining the highest quality sound reproduction.

When I asked for information on the studio monitors and during the reading of a web page, I became aware how little I know on this subject. First thing that lead me to that conclusion is the fact that well known companies such are: Quested, ATC, PMC produce the multisystem monitoring systems. Such a principle they used in earlier models of their main-monitors. Second fact was that only few studio monitor manufacturers use in their products sound drivers of their own production. Others use for example: Accuton, Eton, Precision-Devices - ADAM company. Volt products can be seen in the most three-way system monitors like: Quested, PMC, Genelec, K & H. Beyma Company and Walt. They have a series of sound driver models under the striking name of"Studio". Who can distract you in the intention to buy the same or much better sound drivers for your own purposes? The third thing - electronics, which is found even in good three-way system speakers do not have such a high level of quality and elemental base, unlike its prices . When I saw the interior of an expensive studio monitors, I began to doubt the "optimization of the blocks to each other," because they looked very primitive. This small circuit board could not be compared with the internal composition of ordinary studio amplifiers (do not mix with professional). Fourth - the monitor signal passes dividing, correction and smoothing phase in the analog form. This means that the loss of sound is inevitable, even during the active division, as I said earlier. In the case with PA systems can use digital crossovers, which have not only a higher cutoff slope, making all the operations division in the digital signal, but still allow themselves to be used as a DAC. Fifth - the fact that in the seventies and eighties there were only PA studio monitors, and their modern versions of "All In One" have begun to emerge only from the mid-seventies in very small print runs. Unique goal of this approach was the posibility to make a compact and mobile monitors with complete electronics "inside". Of course, we can not know what manufacturer has built in, and that often components are not of the higher class ... Sixth - Price . Price of the PA monitors components typically do not exceed the price of ready-made acoustic system.

The biggest advantage of this approach to studio acoustic systems lies in the full freedom of choice of components of known characteristics and the possibility to make a monitor that suits individual needs. You have the right to choose the number of bands in the projected sound system, its power, to determine its size, the number of drivers, their characteristics, materials, diffusers, acoustic design. Scope in the choice of amplifiers is also huge.

But you can set up a completely logical question. 1: "Is it necessary, if there are already ready-made good quality characteristics with high power, four-way design, and connected at the same PA scheme?". That is the main idea of the whole site. Do not make similar or identical monitors, as well as those manufactured in factory, but monitors with unprecedented level of sound reproduction, which still does not exist.

The question number 2: "If not, has the market for studio monitors reached the highest level of sound reproduction?! Where else is better? How it is possible to build something that does not exist?" - Yes, there are not ready-made products but for the independent production of such acoustic systems, fortunately there is still all and it is produced by a number of companies. These are not the averages crossovers, loudspeakers and amplifiers, which are present today in the market or professional studio acoustics, these are - the best of the best, most well-known manufacturers (though not necessarily) that survived till the present day. Some of them have a worldwide reputation and long history of several decades, while some are not well known or appeared only recently. Such firms are only few, so it is impossible to get confused in choosing the right one. Only thanks to them the concept of Ultimate Studio has the right to live.


Basics of studio sound reproduction

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