Review: Spread Spectrum Technologies Trinaural Processor Surround Pre

Category: Preamps

This thing really works!

There is a school of thought that, quite apart from multichannel audio, a third, center, speaker improves playback of 2-channel recordings. I happen to belong to this school, and have used a center speaker for decades. In my case I was more or less forced to do so by the layout of my room, which puts stereo speakers too far apart. I have used many methods for deriving the center channel signal. Until now the best was one that I think I invented...invert the signal of one channel and bridge the stereo amp with the center speaker. This does put an awfully low impedance load on the power amps, but surprisingly I had no problems in this regard.

The Trinaural processor is designed to generate three line level signals from normal stereo recordings. I will not try to describe it in detail because the Spread Spectrum Technologies website does that. Actually, not all that well, but worth reading.

I firmly agree that two channel recordings are best played back with three speakers, but that argument is not my concern at this time. I am talking to people who have a good multichannel audio system, who still own and like to play 2 channel recordings. The problem is that when your speakers are set up for multichannel, the front left and right are too far apart. You need to light off that center somehow. For CDs with digital output I have used Dolby PL3 channel, with not very satisfactory results. With SACD and DVDA you don’t get digital data, and a surprising number of supposedly multichannel discs do not use the center channel, and some are only stereo from the get go. This fact drove my decision to buy the Trinaural.

I installed the Trinaural between my Rotel 1066 Prepro and the Behringer DEQ2496 equalizer, going out to my electronic crossover and power amps. The input to the Trinaural is single ended. Outputs are provided both single ended and balanced. I used the single ended because I already have RCA to XLR interconnects, and the run is only three feet. The Trinaural has a switch that selects either multichannel inputs, R,C,L,SW, or L,R. When the multichannel inputs are selected no processing is performed, but the signals are not passed through, untouched, but go through the input and output circuitry. This may be useful to convert from single ended to balanced if the following equipment cannot work with single ended. Unless this is needed, a hard bypass with relays or switches would be theoretically better. (In the Behringer DEQ2496 such a hard bypass occurs if AC power is lost or turned off). But this is theory, and in practice I find no fault with the Trinaural sonics.

First I evaluated the Trinaural in the role for which it was designed, 2 channel recordings.
Sony SK44922, Chopin Piano concertos, RCA 2272-2-R, Tonight in Person..The Limelighters, and RCA 09026-61266-2, the Sir Thomas Beecham 1959 recording of Handel’s Messiah (the so called “Big Band” performance).

With the Chopin there was a dramatic improvement with processing. The piano became much better defined, and separated from the orchestra which was arrayed with a very convincing panorama. Somehow pulling the soloist out of the ensemble seems to broaden and enliven the panorama.

The Limelighters recording was made at a live performance at Ash Grove, Hollywood, July 1960, and has lots of good ambience. This too was beautifully enhanced by the processing. The three performers were solidly located in their different places, and again the acoustic environment was vividly recreated.

I have always thought that Beecham’s Messiah was the best performance (out of hundreds) but the LPs were cut at so low a signal level that noise was intrusive. The CDs avoid this problem, but this is a piece of music that cries out for multichannel. (I have a multichannel version, but the performance is not to my liking). Now with the Trinaural the Beecham Messiah becomes sonically superb.

So for any 2-channel guys who are still out there, I do think that the Trinaural will improve your system. However…a word of warning. I found results with an LP were (in a word) lousy. The processing seems to emphasize signal that is out of phase between channels, and this signal, vertical groove modulation in a LP, is greatly inferior to the common mode signal, horizontal groove modulation. So vinyl people are out of luck for this device. Perhaps a better LP playback system might work better, but you have been forewarned. I found similar problems with FM radio. Again, the differential multiplexed signal is inferior to the mono one. And this was with a fairly strong radio signal. Using CDs I compared the Trinaural processing with Dolby PL3 channel and the Trinaural was clearly better.

On to Multichannel recordings. PentaTone PTC 5186 114, Rachmaninov Piano Concerto 2, and Sony SS89649 Brahms Violin Concerto, Hilary Hahn.

The PentaTone recording is one of a series that was originally made for release in a four channel open reel tape format. The format died, but the excellent master tapes are still with us. The producers of these discs deliberately chose to retain the old four channel mix although the SACD media would permit a mix providing a center channel. This is the kind of “Multichannel” recording that led me to buy the Trinaural. Again, a great improvement over the 4-channel playback.

The Hilary Hahn violin concerto recording is one that really got me mad! Although it does use the center channel it fails to place the soloist in it, with the result that (as I have said before) “poor Hilary is chopped in half and dumped in the corners of the room”. A mix disaster, IMHO. Using the Trinaural to synthesize a center signal from the left and right signals gave me about 18 dB higher average center signal level than the center signal on the disc. Nothing of any significance was lost by completely discarding the disc center channel signal. If this were not the case, the disc player could be told that there was no center speaker, and it would have mixed the center into left and right, from which the Trinaural could have recovered it. (I didn’t try this yet).

In summary, I think that the Trinaural brings 2 channel recordings very close to the multichannel spatial effect, and perhaps better for those folk who can’t tolerate sound from behind them. It makes 2 channel recordings playable with the widely spaced speakers of a multichannel system, and enhances some multichannel discs. Of course it does nothing about the sonic imperfections of the 16 bit 44 KHz CD…if that bothers you go buy DVDA and SACD.

Associated gear
Denon 2900 Disc Player (Underwood mod)
Rotel 1066 PrePro
Behringer DEQ2496 Equalizers (2)
Ashly electronic crossover
Channel Islands D-200 amps (3)
MG1.6 main speakers (3)
Custom SW system (3)
CarverPro ZR1600 amps for subwoofers (3)

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This is pretty interesting concept and piece of equipment. Thanks for posting your review.

Do you feel that the benefits are really for large listening rooms, where there is a great distance between the left & right speakers; or would there be noticeable improvments using this configuration in a small setting as well?

Eldartford, just curious, what are the distances between the L/R mains and to your chair (and is your center recessed to maintain equal distance)? And how are the 3 subs positioned?
The benefits of the Trinaural are obviously greatest for a system which has the speakers spaced far apart, and this is not always necessary in a large room. I can recommend it for any system configured for multichannel, regardless of room size. For a two channel system in a large room it would permit the stereo speakers to be moved further apart, which is probably a good thing. For a 2 channel system in a small room I don't think that the benefit would justify the cost (but that all depends on how righ you are).
Zaikesman...My Left and Right speakers are about 15 feet apart. This is dictated by the room which has two french doors in the wall, leaving three pieces of wall. The subwoofer enclosures are embedded in the wall behind each Maggie.

The center is not recessed, but I use the delay feature of its Behringer DEQ2496 to compensate. I could do this compensation using the "speaker distance" (delay) feature of my disc player, but then it would only apply to the disc source.

One feature of my rig, with three planar speakers in a fairly large and open room, is that the sound field is very uniform throughout, and I listen from whereever I happen to sit. Generally it will be more than about 12 feet from the center speaker. Of course, having that center speaker avoids the need to be equally spaced from Left and Right so as to preserve an image of the center.