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Home > Gaudi > Secrets of Gaudi Sound  2014/08/05 created

Secrets of Gaudi Sound

The highest grade parts are not used in Gaudi, though the horn-loaded midrange drivers are expensive exceptionally. No state-of-the-art technology is employed. No elaborate process, no innovative circuitry nor mechanism is employed. Most parts and components used in Gaudi are old. The oldest one is the power amplifier for the woofers (MA-201C) that has been used since 1974. Many other old components like the analog disc player made in 1982 (PS-104) are used. Many off-brand, cheap parts are used. The speaker cables are made of thin wire that is only slightly thicker than human hair.
Nevertheless, why does Gaudi offer superb sound quality comparable to hi-end audio systems?
I believe the following six reasons are the answer to the question:

Reason #1

The most essential reason is that Gaudi has no major defect that impairs sound quality.

The built-in network of the loudspeaker is the most influential defect in common audio systems. That is a passive filter composed of inductors and capacitors. It handles the signal amplified by the power amplifier, so it cannot be an active filter.
The passive filter does not work as accurate as the active filter, because it was greatly affected by fluctuation of the load impedance (the voice coil impedance). It is highly possible that it passes a certain level of low frequencies to the tweeters and a certain level of high frequencies to the woofers. Phase changes in a complex manner too.
In addition, attenuators are necessary if the sensitivity of each unit is not equal to each other. The attenuator also impairs sound quality.
Moreover, the network is usually incorporated within the speaker enclosure, so vibration from the speaker drivers comes to the network inevitably. It is impossible to prevent vibration from reaching the network. There is no perfect vibration insulator in the world.
On the other hand, every electronic part is more or less microphonic. Especially, the capacitor is sensitive to vibration so that it can be used as a microphone element.
The build-in network spoils the original tonal quality of the speaker drivers.

Fans of full-range driver hi-fi speaker system claim that one way speakers offer sharper stereo imaging than multiway speakers. This claim is based on comparison to multiway speakers with built-in networks. In my experience, the tri-amplified system is better than one way speaker system in stereo imaging. This is probably because the midrange drivers and tweeters in the tri-amplified system cause less distortion and less phase difference between the left and right channels.

Although Gaudi has many minor shortcomings, it doesn't have the major defects like the passive network. This fact leads to the excellent sound quality of Gaudi.

Reason #2

The second most significant reason is simplicity. I always keep it in my mind, "The best is simple". I omit everything that seems to be unnecessary for hi-fi systems.

Obviously, the tri-amplified system is not simple. If there were a true full-range driver (that has flat frequency response with low distortion in the range between 25Hz and 40kHz), I wouldn't hesitate to build a one way speaker system by using it and a mono-amplifier system by using the speaker system. However, there is no such driver in practice.
No choice but a multi-driver speaker system is required for a hi-fi system, and, as mentioned above, the passive network shouldn't be employed. The tri-amplified system is the best choice, though it is not simple.

Though Gaudi is a tri-amplified system composed of many pieces of equipment, each component and cable is utmost simple.
For example, the preamplifier PA-210 Simplicity is a thoroughly simplified amplifier as its name suggests. The selector and volume control are only functions it has. Its circuit is composed of very small number of parts.
Another good example is the network CD-211A A-NET. It has no input/output jacks. The cables are soldered directly to the circuit boards. Even the most expensive plug/jack may impair sound quality (I think the more expensive, the lower sound quality). It's not necessary for the cable to have plugs at the both ends. So the cables connected to CD-211A have a plug at only the other end.
The woofer module of the speaker system SS-309A does not have terminals, either. The speaker cables are soldered directly to the drivers.

Reason #3

The third reason is avoiding excessive margins. Audiophiles and engineers tend to believe the bigger margins are better than narrow ones. But I believe "Too much is as bad as too little."

The best example is output power of the power amplifier. The output power of MA-208, which is the power amplifier for tweeters in Gaudi, is only 10W+10W. It is enough or even too much for the high sensitivity horn-loaded tweeter. Specifying that low output power makes it possible to simplify the circuit, to reduce the number of the parts and to select smaller parts. These lead to the higher sound quality.

"The higher stability of amplifiers, the better sound quality" is a common knowledge in hi-fi circles. But again, I think of "Too much is as bad as too little."
The output waveform of MA-208 shows a little overshoot, when it amplifies square wave into a dummy load of 8ohm//0.47uF (I regard a 10% peak overshoot as allowable). This is because it implements only the lead compensation capacitors to improve stability. If more compensation networks are added, the overshoot and ringing could be eliminated from its square wave response. But I dare not choose that way, because the additional compensation networks may make Gaudi sound 'dead'.
The practical load of MA-208 are only the tweeters and the cables. No other parts such as inductors, capacitors or resistors are never connected. In practice, only capacitive load is stray capacitance of the voice coil and the cable. It may not exceed several hundreds pF. That small capacitance does not make the amplifier unstable, and the overshoot does not occur. So the additional compensation networks are not necessary and shouldn't be added.

In Gaudi, a thin wire whose core's diameter is only 0.4mm is used for the speaker cables. Most audiophiles believe that thicker speaker cables are superior to thinner ones. If it were true, Gaudi's sound quality would be the worst. On the contrary, Gaudi's sound quality is excellent. Consequently, it can be said that it is a superstition that the thicker cables are better. There is the optimum diameter of the wire core.The thicker core than the optimum diameter causes unwanted current flow disturbance and some distortion.

Reason #4

The fourth reason is that the specification of each piece of equipment in Gaudi is specified according to the system design. Each component's spec is specialized for Gaudi unlike commercial audio equipment. This leads to simplification and adequate margins mentioned above.

Reason #5

The fifth reason is the midrange drivers and tweeters, which are the most important parts in an audio system. They are horn-loaded drivers in Gaudi.
I believe the horn speaker is superb in principle. In comparison with the direct radiator, it excels in its presentation of recorded detail thanks to its ultra light diaphragm and voice coil and powerful magnetic circuit. It can reproduce ear-deafening explosion sound as well. In other words, all distortions, both electrical and mechanical, can theoretically be much lower than direct radiators. In addition, its very high sensitivity alleviates the burdens of the power amplifier and the cable.
Nowadays, horn speakers largely disappeared from domestic audio use (except in Japan). But it is not a matter of sound quality, but a matter of cost. Horns are expensive and a bi-amplified or a tri-amplified system is required to bring out their real quality.

30cm (12") woofers are used in Gaudi. I believe 30cm (12") is the minimum size for a hi-fi system. Small woofers, which are mainstream nowadays, cannot reproduce true bass. I once was a regular customer of a certain hi-fi shop (in 2008-2009). I was allowed to try out almost all the speaker systems in the shop. I found no speaker system using (a) small woofer(s) that can reproduce true bass like Gaudi does. Each speaker's advertising statement exaggerated its ability to reproduce bass perfectly, but, in reality, it was not competitive with speakers using a large woofer.

Reason #6

The sixth reason is the principled system design. I have been building Gaudi for the past 40 years without changing it. Meanwhile, I've found a lot of shortcomings and eliminated them. The unchanged system design and the continuous effort to improve resulted in the high tonal quality of Gaudi.

Of course, there have been many innovative advances for the past 40 years: horn-loaded drivers got out of use, and dome drivers prevail instead; high performance small woofers were developed, and smaller or slimmer speakers using them became mainstream; digital media such as CD, DAD or SACD appeared on the market; cassette tape recorders became old-fashioned and were replaced by memory recorders; and PCs became used as audio equipment. The advent of digital revolution brought about drastic changes in the audio industry and hi-fi circles.
However, this technological innovation is chiefly contributed to downsizing, cost reduction and better user-friendliness of audio equipment. I think there have been few breakthroughs for improvement of sound quality. So I haven't thought about a need to change Gaudi's system design.

For example, Does replacing the horn-loaded drivers with dome drivers or replacing the woofers with smaller ones improve sound quality of Gaudi? I don't believe so.

As for the power amplifier, does the class-D amplifier excel the linear amplifier? My answer is 'no'. I already experienced the class-D amplifier cannot be used for the horn-loaded driver, which has very high sensitivity and responds to very high frequencies (for further details, see the section 'Rev. A' of the page of SS-309).

Are the CD and the SACD superior to the vinyl record? The vinyl still sounds better to my ears. It is strange, though, each time I upgrade Gaudi, the vinyl comes to offer more and more superior sound quality to the digital media.

Now Gaudi is about to be completed. I already started working over my plan of Gaudi II, a new my ideal audio system. But there's a possibility that Gaudi II may resemble Gaudi. So far, I haven't come up with a good idea for the superior system to the tri-amplified system using large woofers and horn-loaded midrange and tweeters like Gaudi.




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