Component Reviews 

Dynavector SuperStereo Adapter SS ADP-3

Designed to easily transform any two-channel system into an immersive surround experience from any stereo and even mono sources

Published on August 12, 2005

 
Specs:
Model: ADP-3 analog/digital SuperStereo processor with built-in 20-watt stereo power amp
Impedance: Line In 50K ohms; Speaker 300 ohms
Input Voltage: Line In 1.0 volt
Speaker Input Sensitivity: High 10.0 volts; Low 20.0 volts
Output Voltage: Adaptor line out 4.0 volts
Speaker Impedance: 4 to 8 ohms
Amplifier Output: 4 ohms load = 24w per chan.; 8 ohms load  = 20w per chan.
Mode: 3 SuperStereo modes selectable
Polarity: Reversible against front speakers with switch on front
Power Consumption: 90 VA
Dimensions: 430W x 70H x 282D mm
Weight: 6.2 kg
Provided accessories: AC power cord, speaker cables (2 pairs, 1m & 7m length), Operation manual, Warranty card   Dynavector Systems Ltd., Tokyo
http://www.dynavector.co.jp
U.S. Distributor: Toffco
toffco-usa@yahoo.com
 

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Intro

Since stereo first came on the scene there have been various attempts to gain a more immersive surround sound experience that involved more than just a flat frontal sonic proscenium.  One of the earliest was the Haefler circuit, which basically just tapped the two + outputs on a stereo amp and fed the resulting L - R difference information signal to one or more efficient speakers placed on the sides or rear of the listening area. It didn’t even require another stereo amp. There are current processes which continue this often very effective ploy of achieving surround effects out of two-channel sources, such as NAD’s EAR.  Processors such as Dolby Pro Logic IIx and Circle Surround II start with the same difference information but process it heavily to achieve generally excellent results with most stereo material.

Then there is the entirely different approach of adding various delays and sometimes equalization to the original two-channel signal and then feeding it to additional speakers.  The Audio Pulse was an example of such early devices.  The problem was that the delay was not very adjustable - only in volume level. And in those days of the LP any tick or scratch on a disc was heard not once but twice due to the delay circuitry. Later Yamaha and others carefully measured the reverberation in various sized halls and venues and built these options into their receivers and processors.  One approach was to feed the delayed sounds thru a pair of small speakers mounted high and in front of the front trio of speakers.  Ambiophonics also uses delays and multiple additional speakers to simulate the sonic immersion of the concert hall environment.

Theory of the SuperStereo Approach

The late Dr. Tominari of the Japanese analog tonearm and cartridge makers Dynavector worked for 18 years and received patents on his individual approach to achieving a more three-dimensional sound out of standard stereo sources.  He developed two earlier SuperStereo models and the sophisticated ADP-3 had been produced by Dynavector since his passing.  An important finding of Dr. Tominari’s research was that the low frequencies are not absorbed in a hall nearly as much as the high frequencies, causing them to bounce around many more times and undergo a longer delay. Also, the higher frequencies are reduced and scattered more on their way to the listener. The delay cannot just be turned up, because at around 30 milliseconds it turns into an echo.  This is why a single delay time for all frequencies, as in the Audio Pulse, was unsuccessful.

SuperStereo uses differential time delays across the audio spectrum and the high frequencies are attenuated.  Thus the 30 ms barrier is broken and the third and highest of the ADP-3’s three modes allows a maximum of 343 ms.  As far as I can determine from the extensive white paper on the Dynavector site, the circuitry does not make use of the L - R difference information; it processes the left and right channel signals separately.  That actually qualifies it as what I have ruefully called the Yamaha approach - a “boingerizer.” But wait a minute - the SuperStereo is unique and a great deal more sophisticated in its proprietary processing than the “hall simulators.”

The white paper is titled “Why the Current Standards for Hi-Fidelity Reproduction are Inadequate and How Dynavector’s SuperStereo System Addresses the Problem.”  It speaks about how the goal of high fidelity reproduction has been to realize an ideal transfer function of one (the relationship between the input and output of an audio system).  It says that for the most part the technology has now achieved that with virtually perfect frequency and phase response, but most people would agree that there is still a huge gap between live music and its playback on an audio system.

Dynavector observes that the accepted criterion of high fidelity are only valid in special situations such as an anechoic chamber or an open space outdoors.  In an enclosed environment the propagation of music signal waves is entirely different and much more complex. In real music many signals of many different frequencies occur at the same time. Some differ only slightly from the fundamental tone, thus generating beats due to the frequency differences. The beats tend to propagate differently from the fundamental tone, even to traveling at a different, slower velocity.  The complex sound waves of music are shadowed by these later-arriving beats caused by the side frequencies. Such time misalignment makes the sounds of music in a concert hall more rich, colorful and enjoyable.

Dynavector feels that no loudspeaker can recognize and reproduce separately both the phase velocity and the group velocity from the input signal (which are different), no matter how accurate in frequency and phase it may be. Their opinion is that multichannel surround systems completely ignore this concept. “The character of the sound of music played in a concert hall is very much dependent on the state of the shadows at the listening point...to enjoy the playback of music in a listening room...as if one were at the original concert, the group and phase velocity should be reproduced separately.”

Setup and Controls

And the SuperStereo processor does this by producing from the L and R channel signals numerous group delays thru the entire audible frequency spectrum.  These signals are played thru two additional small speakers which are placed not at the sides or rear of the listening room, or even high in front as with the Yamaha approach, but located at the same height as the two front speakers, a few feet in front of them and to the outside.  The idea is that there is a mixing or interaction acoustically in the room between the front and the additional speakers. (Dynavector calls them sub-speakers, which I find highly confusing.)  While the group delays thus produced in the listening room are not identical to those in the original venue, the feeling of life-life reality is enhanced by the system when playing standard two channel sources, whether they be optical discs, movies, vinyl, cassettes or even FM.

The ADP-3, by including the stereo amp in the processor, is designed to require only the two additional small speakers. I used a pair of the inexpensive Paradigm Atoms on their metal stands, which brought the mini-monitors to exactly the height of the tweeter and the high frequency of the two woofer drivers on each of my Von Schweikert VR-2 frontal speakers.  Due to a tight situation near the picture window on the left, I had to angle the Atoms in toward the VR-2s, which is also suggested as an alternative in the ADP-3 manual. I placed them about 2 12 ft. in front of the VR-2s. The diagram above show the hookup and location of the speakers, although these are not angled toward the main speakers.

I found only the level control really useful in operation. The phase switch always sounded better in phase with the main speakers, and the middle of the three modes nearly always sounded best with most sources.   The first mode is for small group recordings or studios with little reverb and the third mode adds a huge amount of reverb which would only be useful on recordings in a large cathedral where the original two-channel recording probably has plenty of reverb already. There is a red overload LED which never let except when turning the processor on and off.

On the rear of the ADP-3 are line input jacks, which I used from my Sunfire Theater Grand preamp. There are also speaker input terminals if you prefer to feed the unit speaker-level signals. I would think that could only degrade the sound since you are then processing the signal with distortions added by the main amplifier. The ADP-3 also has output jacks for a larger amp in case you want to use some higher-quality, less efficient speakers. It occurred to me that there would be an even better timbre match if I mounted a pair of Von Schweikert VR-1 mini-monitors as the additional speakers instead of the Atoms, and I don’t believe a more powerful amp would be required for them.

A/B Evaluation of the ADP-3 Adapter

I started with some standard stereo CDs I was reviewing.  There seemed to be little effect until the level control of the ADP-3 was turned to about the 3 o’clock position. Then a richness and bloom was added to the sound that made it extremely pleasurable.  A greater feeling of the particular venue’s environment was definitely provided.  With proper setting of the level control - which I arranged close at hand since there is no remote - I was able to obtain a wider soundstage, with more “air” around the individual instruments and a more solid sonic picture. I found a setting around 4 o’clock position to be the most-used.

I was curious if the ADP-3 suffered from the double-click problem of the old Audio Pulse and thus got out a few of my more “actively-appreciated” LPs.  Even on a serious groove click there was not a doubling of the sound - in fact fairly scratchy vinyl sounded less so.  I was also curious about the processor’s effect on mono sources, since a mention of that ability was made in the unit’s manual. I tried a recent First Edition Music reissue of some mono recordings of works by Villa-Lobos: Erosion, and Dawn in a Tropical Forest, with the Louisville Orchestra.  The Louisville series was not known as being in the highest fidelity, and the mono sound was rather dry and dull.  Bringing up the volume control to about the 3 or 4 o’clock position brought a tremendous lift to the music, adding a depth and feeling of the orchestra playing in a real hall.  Few would have been able to identify the recordings as mono.  Dynavector suggests bringing up the level slowly until it is about the same as issuing from the front speakers or even a trifle louder.  It is critical to get the level just right - too little has little effect, and too much buries the music in excessive reverb. The manual says to try the higher and lower positions of the Mode switch after getting the level right, but I disagree.  The lower setting usually needs the level increased and the higher setting has such strong delay that the level has to be reduced somewhat.  Once the mode and level are set for any recording, the main volume control of the preamp or receiver becomes the master level control, obviating the need for remote control of the ADP-3.

The next mono source I tried was one of the very few which didn’t fare well with the ADP-3.  It was the excellent reissue on an Italian label of the mid-1930s Pablo Casals recordings of the Bach Sonatas for Unaccompanied Cello.  No matter what mode or level I selected on the ADP-3 the cello either became much larger than life or sounded like a cello duo - one instrument at the left and another at the right frontal speaker. It also sounded more like a string bass than a cello. Changing the phase made it worse.  I also selected a bunch of vinyl - both mono and stereo - and found all of them benefitted from the SuperStereo treatment when the proper level was achieved.  One of them happened to be one of those “rechannelled for stereo” LPs, and it struck me that SuperStereo creates a 100% better spatial impression out of most mono sources than directing highs to one channel and lows to the other ever accomplished.

I got out a 1989 Philips CD of four Carlos Chavez works conducted by the composer.  These stereo recordings were made on 35mm film by Everest in l958 but had some hiss. Unfortunately this was the first iteration of the No Noise digital noise reduction system, and Philips’ and other label engineers made rather ham-handed use of it - overdoing the reduction of high frequencies to the point of dulling the life out of the music.  Inserting the ADP-3 signal at Mode No. 2 brought life back to the music and made it most listenable. Most of the others in this series were mono and the SuperStereo brought their dead-sounding sonics back to life in every case.

Multichannel Uses

The ADP-3 is designed for two-channel diehards who have a pair of high quality speakers, or at least high enough quality to warrant spending $2000 on a processor to improve their fidelity and create a more natural sonic image.  However, since the improved dimensionally it creates  does not extend much past the frontal soundstage, there is no reason it cannot be added as well to a standard 5.1 surround system, which is what I did.  On many multichannel SACDs it expanded and widened the frontal soundstage and seemed to begin a filling in toward the sides which blended perfectly with the surround speakers - even though mine are a bit further to the back than the recommended 5.1 speaker placement diagram.  I found the best balance was often with the level slightly lower than when using only the front two speakers. Hi-res sources often have more detail in the reverb tails and thus may not require as much of the SuperStereo signal to be mixed in.

There is one problem with using SuperStereo with the normal left-center-right arrangement of the front channels: The addition of the signals from the two additional speakers mixes with the left and right main speakers and thus achieves a higher volume level on those two speakers. Whereas the center speaker has no added effect speaker directed at it, and thus recedes in level compared to the left and right.  Usually being a smaller speaker than the left and right also works against a balance.  I found raising the level of the center speaker in relation to the left and right helped a bit but was not a perfect solution. It is obvious the processor is designed to be used with basically two frontal speakers.

I think the best multichannel use of SuperStereo would be a 4.0 surround system without a center channel.  One extremely welcome feature of the process is a major widening of the sweet spot, which is part of the reason for being of the center channel speaker.  In fact, the sweet spot created is so large that listening in an adjoining area is much more enjoyable than without the SuperStereo.  My dining room area is off my listening room space and the front speakers are at a 90-degree angle to it.  With the ADP-3 I get a greatly improved sound while at the dinner table.  In fact this is the feature I believe I will miss most of all when the unit is returned after reviewing.

The ADP-3 is recommended for use on video soundtracks as well as straight audio, so I used it while viewing several DVDs.   With music DVDs it was as effective as with audio-only discs.  On some I had to raise the level on the surrounds a bit to match up with the higher levels in the frontal area.  However, I found even the Position 1 setting of the Mode control and a fairly low setting of the Level control resulted in an unnatural echo being added to most of dramatic films’ dialog tracks.

Conclusions

The Dynavector white paper states that SuperStereo can improve difficulties in listening room size and acoustics, and that no special room-tuning treatments are needed with it.  I can see that could be true, but I must disagree with their statement that it does not interfere with room decor. I should think the presence of two more speakers on stands placed out into the room some distance in front of the two front speakers with the backs facing the listening area would be considered a major interference by most users - meaning this is not just a W.A.F.  Those proudly owning a pair of really striking and expensive high end front speakers might not be happy to have a pair of underfed monkey coffins on stands facing them. Dynavector reports they have had good results with the small Gallo spherical speakers, which would certainly be less imposing.

SuperStereo does work quite successfully.  I could imagine a staunch two-channel audio buff interested in getting a more natural and immersing effect going for the ADP-3 in a big way.  Especially if he or she concentrates on classical and jazz genres.  I didn’t find the process added that much to most pop music, which is already pretty processed and doesn’t occur in a natural venue with normal reflections of the sounds.  Recordings with natural acoustics provide the very best sources. It also brings new life to old mono recordings for those into historical recordings by past masters in the classics or jazz. I would think an especially synergistic combination would be someone with such a collection and the very specialist Helicon mono-only cartridge - a combination made in heaven!  

But the ADP-3 could transform a very basic entry-level audio system as well - expanding the soundstage greatly and improving the bass reproduction, even without a subwoofer. Even smaller additional speakers could be used facing the main two speakers. The super-wide sweet spot provided by SuperStereo plus the improved sound in adjoining rooms and areas would be other major pluses for the processor. Anyone who appreciates the advantages of surround sound for music but doesn’t want to deal with side or rear surround speakers or the extra electronics involved would find the ADP-3 a much simpler solution whose enhancement to any two channel audio system is certainly not subtle by any means. It would be best to try out the unit with one’s home system first, but unfortunately there are few dealers as yet.

- John Sunier  

on this article to AUDIOPHILE AUDITION!

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