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Poor Sensurround Soundtrack
on June 10, 2007
While the picture is beautiful, the new DVD of "Earthquake" completely misses the boat on the Sensurround track and special features. First of all, the so-called "3.1" Sensurround track is nothing but the same, mono, audio fed to the 3 front channels with the 25/35 Hz control tones on the .1 LFE channel - no rumble is there at all. Nothing of the sort was ever heard in theaters, so I don't know why Universal bothered. It's obvious that the Universal tech's in charge of the DVD audio transfer didn't know that the control tones are NOT the earthquake rumble and are NOT meant to be heard! The 5.1-channel remix is problimatical too. Earthquake was the first feature to use the Sensurround Special Effects System (US Patent #3, 973,839). Because, at the time, audio in theaters and on film was in such a primitive state, MCA/Universal engineers designed a sound system to run along side the theaters existing system. Two control tones, at 25 and 35 Hz, were recorded either on the main soundtrack (for optical prints) or, with stereo Magnetic prints, on the redundant optical soundtrack. Their presence and volume controlled the turning on and off of a low-frequency noise (rumble) generator to create the 'earthquake' effects - they also controlled the addition of the "Center Front" channel (or the composite optical) into the Sensurround channel to create "surround" effects. When desired, the two tones could also increase the volume of ALL the speakers in the theater by a desired amount. While the 4-track magnetic soundtrack had a standard "effects/surround" soundtrack (complete with 12kHz CinemaScope switching tone), in Sensurround equipped theaters, the surround mag track was disconnected and not used at all... instead, the Center Front mag channel was connected into the Sensurround channel to create the 'surround' effects when needed. For non-Sensurround installations that used the Magnetic soundtrack, the 4-track mag had the standard surround soundtrack available. Universal's engineers in charge of the new DVD soundtrack remix do not seem to have known this - none of the sounds from the Center Front channel are used at all in the surround channels, nor is any of the Sensurround rumble taken to the back channels as it should be. In addition to the deep rumble, Sensurround was intended to "Surround and engulf you", which the new 5.1 track does NOT do! The composite mono optical prints, or the mag stereo prints, contained all the information the mixers needed, to know when to direct the sounds, and by how much, from the Center Front into the back channels. They only had to listen to and measure the amounts of 25 and 35 Hz tones! Heck, the old MCA DiscoVision laser videodisc release has the control tones present that we can hear, so anyone could have figured it out! Also, it does not appear that Universal used a Sensurround rumble generator - the bass is nowhere near deep enough - I've measured it and it cuts off around 25 Hz! That's a whole octave higher than it should be! The cut-off frequency that was designed for Sensurround was 16Hz. The bass should be played at a level of 110-120db at those frequencies! To replicate the Sensurround soundtrack on DVD, here's what should have been done:
The "main" channels should have been recorded at a much lower level than usual onto the DVD master. The Sensurround rumble should have been recorded at, or as near as possible, to 0db as they could. This would have allowed them to duplicate Sensurround in the home. It would have required the home viewer to raise their main volume control much higher than usual to hear the soundtrack, thus, when the rumble came along, it would be at it's correct, high, level - and the extra headroom could have been used to raise the level of the main soundtrack during the quake as the original presentation called for. The Center Front should have been mixed into the surrounds as required and the original mag Surround track used too. For viewers who don't have the ability to play the Sensurround track at such high levels, the original 4-track master, without Sensurround, should have been supplied at standard volume as an alternate track. The original mono Sensurround-compatible shouldtrack should have been supplied too as a 1.0 Dolby Digital track.
Contrary to what others claim, Earthquake was the ONLY Stereophonic Sensurround release (Zoot Suit doesn't count) - after Earthquake, Sensurround was modified to place all the effects on an optical mono track with dbx Type-II noise reduction. ALL of the other "Sensurround" DVD releases from Universal get the Sensurround track wrong too - Midway, Battlestar, Rollercoaster - all WRONG! The Sensurround, because of the control tones, would pan from the front to the back of the theater, as required - none of the DVD's duplicate this - it gave them a 'surround-type' soundtrack capability from a standard mono-optical print. Hopefully, future HD-DVD relases will get this right - if Universal would only ask me about it! I have extensive documentation on the Sensurround system and am probably the foremost authority on it in the world.
The basic fidelity and seperation of the 3 front channels is quite good, as is the high-frequency response. Unlike other magnetic stereo films of the era, Earthquake was mixed with mono, meaning Center Front-only, dialogue - other films of the time panned the dialogue across each channel to follow the speaker. The DVD replicates this nicely, although I hate mono dialogue.
The image of "Earthquake" has a bit too much edge enhancement, but is otherwise OK. Sadly, there are NO special features at all, which is a pitty, as there was a wealth of material produced for Earthquake. MCA Universal made a "Sensurround Product Demo Reel" to show theater owners how the system worked and why they should install it in their theater - there were film demo reels to show the total image+sound effect - there were Sensurround encoded trailers - there was deleted footage - the LAX restraunt was actually modeled and filmed collapsing, but the footage wasn't used in the film - in addition, around 10 mintues of footage were deleted shortly before the films release - all of this should have been included on the disc along with photos of the incredible Sensurround horns.
BTW, in the Mid-1970's, MCA/Universal was attempting to sell Sensurround as a new, high-fidelity, film sound system - Dolby Stereo had just become available, and there was a general industry-wide interest in upgrading theater sound. MCA positioned Sensurround as a large increase in fidelity with special effects, all from a single, compatible, mono optical soundtrack. When the dbx Type-II noise reduction was added, the specifications of Sensurround were quite impressive:
Frequency Response-16Hz to 16,000 kHz.
All these specs out-did Dolby Stereo at the time. SENSURROUND+PLUS, used on Zoot Suit, was merely the use of dbx Noise Reduction, WITHOUT the rumble, on a 4-track mag stereo soundtrack.
Hopefully, Universal will get it right on the HD-DVD's of the Sensurround films.