Introduction to the DC-1
Lexicon
The key to our perception of the acoustic space we inhabit lies in the lateral sound field – the sound which moves from side to side in the room. The two front speakers used in conventional two channel stereo do not adequately excite these lateral fields in a playback room. The speakers are too far forward, and the ambient information in the recording is often masked by the music itself. The DC-1 extracts or synthesizes the ambient information, and uses additional speakers along the sides and rear of the room to create a lateral field which closely emulates the original. If the system does not have side or rear loudspeakers the DC-1 can use panorama technology to simulate them.
The object is to generate signals for the sides and rear speakers which recreate the lateral sound missing in conventional stereo. The most basic approach to this is to analyze the incoming material and extract from it the information which should be reproduced from the sides and the rear. As this is also the object of any standard matrix film decoder, one might think the technology for doing this was well understood, but it is not so easy. Matrix film decoders evolved from early Quad decoders and are limited to four decoded channels: front left, front center, front right, and rear. When the single rear channel is reproduced from multiple speakers in a small playback room, the sound from the different speakers interferes with itself, creating a non-enveloping soundfield with an unpleasant timbre. Although there have been decoders in the past with the ability to separate directionally encoded effects into more than four directions, they have all suffered from reduced separation of the rear channels during playback of music. The DC-1 solves this basic problem with a new idea: a 5 or 7 channel decoder which is completely compatible with a standard decoder for any directionally encoded effect, but which maintains the maximum difference between the left and right side/rear channels at all times.
This new technology is available in the THX and Dolby Digital versions of the DC-1 in several effects. The basic effect for films is Logic 7, and the basic effect for music is Music Surround. All the new 5 and 7 channel effects extract the spatial content hidden in two channel recordings and spread it convincingly around the listener. All DC-1 matrix decoding algorithms also include Lexicon’s patented correction circuits for balance and azimuth errors in the original source material, which make our decoders the most accurate in the industry. The difference between the new 5 or 7 channel technology and the older 4 channel technology (also present in the DC-1 as the Pro-Logic effect and the standard THX Cinema effect) is easily heard through the increase in envelopment with music or the environmental sound of any film, and through the increased listener area and spaciousness on a music CD.
Logic 7 technology also lets us reproduce directionally encoded effects with left/right separation in the rear. Thus even with a conventional 4-2-4 matrix-encoded soundtrack (Dolby Surround, Ultra*Stereo, etc.) a sound effect which pans from left to rear will decode in the DC-1 first from the left front speaker, then from the left side speaker, and finally from both rear speakers. The results on a film with a good soundtrack are spectacular.