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Sound-drivers are the starting point in projection of any monitoring system. Sound driver inflicted absolute quality of the overall sound tract and are the most critical link of the device. There is a simple explanation for this: the speaker has a few dozen times more distortion than the amp and a few hundred times more distortion than the source of the signal. A typical high quality sound source is 0,0005% distortion, amplifier 0,01%, while the distortion of the highest quality speaker does not fall below 0,2 to 0,4%!

At the very beginning it is necessary to decide on the number of divisions in the acoustic system. Based on their numbers and division points among them, the specific drivers were chosen. Maximum sound quality will have four way system speakers with the following division of the signal: the low frequencies below 200 Hz (usually from 80-150 Hz), low-medium frequency 200-600 Hz, medium frequencies 600-8000 Hz (lower limit may be 500 -1000 Hz, the upper 6000-12 000Hz) and High frequency of 8 000 Hz and more. Such approach to splitting of the signal can be seen at companies Adam and Westlake. The low frequencies here are characteristic for a subwoofer. Frequencies of 200 - 600 (1 000) Hz are transitional zone of low to medium frequency and must necessarily be processed with a specific driver with a diameter of no more than 12". Interval 600-800 Hz is the most critical for the human ear, so must be processed with separate driver, which can be standard conical, dome-shaped or even ribbon. For frequencies above 8 000 Hz special driver is also responsible, which must be ribbon or Hale. For high frequencies it is very important, because the standard drivers are not able to approach closely to sound quality of ribbon and Hale drivers. However, the application of special drivers for high frequency is not required if the driver for the middle frequencies is capable to reproduce sound up to 20 000 Hz without noticeable distortion. In this case, an acoustic system can be even three way system.

Especially we have to mention sound characteristics of subwoofers for low bass frequencies (20-40 Hz). Each subwoofer, even with a resonant frequency below 20 Hz, is able to provide linear amplitude - frequency response up to this limit, due to the fall of sound pressure at frequencies below 30-40 Hz that was followed by large distortions. The lowest bass can be achieved only by using the electronic equalizers, or use a minimum of four such drivers, in the same general case. The level of distortion of woofer section of resonant frequencies can reach tens of percent. It is caused by a large displacement of the diffuser own distorted drivers and complexity of its damping amplifier at frequencies lower bass. In that case, this booming and protracted character of the sound would be detrimental to the entire low frequency band of the AU. Therefore, even in the case of a four-speaker, it is recommended to use a separate monitor infrasonic (MI, Infrasonic Monitor), which should work in mono mode at frequencies below 30-40 Hz. Selection of the division frequency between the subwoofer and infrasonic monitor chooses the beginning of the fall of the first sound pressure. In the professional audio industry is at a frequency drop of efficiency often use restrictive Subwoofer Crossover range, or such a signal is intentionally turned off by electronic equalizer. This prevents playback frequency, which the driver is not able to adequately reproduce and it is indicated at the beginning of the fall of sound pressure. The task of playing such "problematic" tone falls on infrasound monitor. In that case, standard stereo woofer section will have much more dynamic sound articulation and infrasound monitor can work without problem to infrasound frequencies with maximum efficiency, and its distortion will not affect the rest of the range. Usually in such a narrow range of frequencies operate subwoofers with main monitors. A striking example of infrasound monitor is a passive subwoofer RIS-1C Company Rey Audio.

In constructing the acoustic system “from scratch”, it is better to cancel using the infrasound subwoofer by applying big bass speakers of 18” or 21”, with a maximum low frequency resonance with two drivers. On the professional audio market there are not too many of such drivers, but you can find them.

Please note that the tactic for signal separation is based on the separation of low frequency, up to 1 000 Hz, to a special driver. And that is the proper solution. Opposite example, you have the Hi-Fi market, where you can find acoustic systems, with additional ultrasound driver that operates at frequencies which cannot be registered by human ear. At this position it is pointless to talk about high-quality sound reproduction.

About choosing dimensions of woofers depending on the distance to the listener, you've already read. It is necessary to determine immediately, whether to use infrasound monitor or not. If yes, then the subwoofer should have diameter of no more than 15" with maximum low cutoff frequency, than the distortion will be outside the operating frequency of the sound driver. Using the infrasound monitor in this case expands choices of woofers, because they do not require reproduction of the lower bass. If you do not intend to use infrasound monitor, for high quality playback of low frequency it makes sense to use a couple 15" drivers or more, depending on specific situation. Despite the stupid delusion, it is always better to use a single large driver instead of two with smaller dimensions, because large drivers with its large cone can move a huge capacity of air, which positively affects the sensitivity and the panorama of sound. The diameter of mid-woofer is usually smaller than the diameter of woofer, but it is not mandatory, what is important is that diameter is no more than 12", because the 15" driver and more are no longer able to work well at frequencies over 600 Hz. Therefore it is not surprising if the sound cabinets and sound-drivers of woofers and mid-woofers are the same size of 12". Such a construction can bee seen at the studio monitors Adam S4. Such a construction is maybe even better: the drivers of the same diameter and model have less of phase and frequency distortion in the point of signal separation. In the large acoustic systems all mid-woofer drivers, diameter of 12" can be applied.

Nowadays, only few companies manufacture sound drivers, which can compete in quality of sound reproduction with a "masterpiece" of engineering constructions that were present in studio monitors of the 70’ and 80’ of last century. But then they were not more available than now, especially in retail. Such structures were present in the best models of studio acoustic systems as turnkey solutions for monitoring and such models were much more available than nowadays. That liberated the supporters of sound reproduction professional concepts of the long and difficult search, comparison of different sound drivers, because it was possible to buy the ready-made acoustic systems. Such systems had the companies like JBL, Altec, Yamaha, Gauss, Urey ... But even these systems (the drivers) didn’t differ much from the other average models, but they were liberated from so many difficulties during the selection. At the time there were several manufacturers of sound drivers in and acoustic systems the market, whose features like quality of products and sound reproduction were fantastic.

At the time there was company TAD (Technical Audio Devices) – an office of company Pioneer, which from the beginning of its existence, produced exclusive studio line and among other products there were beryllium sound drivers with horns. Earlier there were studio monitors also, but due to a fall of interest for such products, the manufacturer has stopped manufacturing them as well as some of the unique models of sound drivers. Famous company JBL, produces acoustic systems for home use with Beryllium sound drivers of its own production that are practically identical to drivers, produced by a TAD. These drivers are used in models of JBL Everest DD66000, K29800SE and SK2-1000. Stage Accompany produces exelent ribbon drivers, subwoofers and amplifiers with an active damping system. And here we can finish. The sound drivers from other manufacturers can’t properly fit in the Studio Ultimate acoustics. That also stands for ready-made monitors. The worst situation is with drivers. There are good amplifiers and digital crossovers at the market, but the most important component, the suitable drivers are almost exclusively represented by a one company and it was a TAD. So let us pray, that Pioneer does not close its specialized branch which has, since its very beginning, produced the best drivers in the world, thanks to which the concept of Ultimate Studio has a right to exist.

However, it seems that the situation is not so critical. In our time there were very widespread ribbon and AMT drivers, of which the biggest models are able to reproduce the sound of 1 000 Hz, which is slightly above the top midrange up to 600 Hz, but is not that critical value. Every year, these types of drivers are becoming even better. You can see them mostly on the home apparatus market and much less frequently on the professional, where they represented the largest and most powerful models. The best models of these types of drivers with the sound quality even better then beryllium drivers and have excellent impulse characteristics like proper amplitude-frequency response and minimal distortion. Given that the ribbon and AMT driver are capable of reproducing sound over 30 000 Hz, their use in systems Ultimate Studio is possible and in this case the system will be tri-way, and MF (mid frequencies) and HF (high frequencies) will play a single driver.

There is a special group composed of representatives of the so-called Japanese Hi-End. No, this is not the Fostex or something like that. In this category we can put companies such as GOTO, ALE and possibly several other manufacturers, for which I have not heard. Drivers in this category are different from their professional analogues with its very powerful and massive magnetic systems, where the density of the magnetic field exceeds 20 000 Gauss, and the total magnetic flux 2 000 000 Maxwell! The effectiveness of such driver varies between 110 and 115 dB, including the lower tones, and the only representative of this group which uses beryllium membranes is GOTO. It limits the application of these drivers in systems because the driver of the Ultimate Studio costs about 7 500 Euros per peace.

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