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Author
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Topic: WOW & FLUTTER
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Chip Gelmini
Phenomenal Film Handler
Posts: 1733
From: Brooksville, FL
Registered: Jun 2003
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posted October 16, 2009 11:42 AM
What I found below is one of the best descriptions of this problem.
Can anyone tell us how playback in the Elmo line of super 8 machines and related print variations causes the problem. I can play some features perfectly, while others have horrible pitch problems.....
Googled (audio flutter) and came up with this:
"Wow and flutter are particularly audible on music with oboe or piano solo playing. While wow is perceived clearly as pitch variation, flutter can alter the sound of the music differently, making it sound ‘cracked’. There is an interesting reason for this. A recorded 1 kHz tone with a small amount of flutter (around 0.1%) can sound fine in a ‘dead’ listening room, but in a reverberant room constant fluctuations will often be clearly heard. These are the result of the current tone ‘beating’ with its echo, which since it originated slightly earlier, has a slightly different pitch. What is heard is quite pronounced amplitude variation, which the ear is very sensitive to. This probably explains why piano notes sound ‘cracked’. Because they start loud and then gradually tail off, piano notes leave an echo that can be as loud as the dying note that it beats with, resulting in a level that varies from complete cancellation to double-amplitude at a rate of a few Hz: instead of a smoothly dying note we hear a heavily modulated one. Oboe notes may be particularly affected because of their harmonic structure. Another way that flutter manifests is as a truncation of reverb tags. This may be due to the persistence of memory with regard to spatial location based on early reflections and comparison of Doppler effects over time. The auditory system may become distracted by pitch shifts in the reverberation of a signal that should be of fixed and solid pitch."
Chip G
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted October 17, 2009 05:41 PM
In my experience, Elmo machines are susceptible to WOW. It seems to be associated with the small diameter of the brass sound capstan and variations in the wind-up tension on the rear spool. Both my GS 1200'S will exhibit wow on certain sections of certain films, other films being seemingly wow free. This is one reason I like Eumigs. I have never heard wow on any Eumig projector, be it series 800 or series 900. If you look at the Eumigs, the sound capstan diameter is much bigger than the Elmo's and the rubber roller is much larger and is really sprung down hard, very effectively clamping the film agains slippage. I think the Elmo's are really susceptible to variations in the coefficient of friction of the film, which of course is really influenced by film lubrication products.
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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj
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