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Topic: Sound Heads
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Maurizio Di Cintio
Jedi Master Film Handler
Posts: 977
From: Ortona, Italy
Registered: Jan 2004
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posted July 18, 2004 07:56 AM
In my personal experience based opinion:
a) regular sound recorders have much stronger heads than any S/8 projector, but keep in mind that at an early stage of wear only a very careful ear may perceive it.
b) recording produces wear (mechanically wise) because you often have to re-record in case of mistakes; apart from that the process of recording per se doesn't affect wear more than playback does.
c) both recording and playback can produce a state of permanent magnetization on the heads: this increases hissing noise and reduces high frequency output; in the long term it can demagnetize the soundtrack too, resulting in a loss of the higher end of the sound spectrum. Solution: demagnetize them on a regular basis (usually every 20-30 hrs) with a proper tool or, in case you don't have it, putting the projector in the recording mode (trick control, if any, set at normal rec), for about ten seconds, projector running with no film. It works because the Bias current from the heads accomplishes the same result as a profesional demagnetizer.
d) Sad to say but no matter how careful you are with your projectors: sound heads do wear out in time. Of course this is a more or less 'fast' process depending on a few factors: the force applied by the pressure pads onto the heads; the resiliance of the heads (GS1200's have the hardest ones followed by Sankyo's 300-800); the type of soundstripe: usually paste stripes are more abrasive than laminated.
Plus the shape of both heads and pressure pads may result in a wear more or less noticeable.
The Goko RM 8008 Sound Editor features the same sound head as the Elmo GS 1200, but the pressure pads are less gentle: I had to replace them several years ago.
Here is my directory of sound heads resiliance:
1) GS 1200 (this machine has a type of head made of sendust alloy which is extremely hard and performing: no other Elmo machine has something like that)
2) Sankyo (all models) and Fumeo heads,the latter made by Photovox
3) Eumig (Series 800)
4) Bauer/Beaulieu (heads made by "Woelke" of Munchen, Germany)
5) Eumig (Series 900: models 905-940, with the exception of models 932, 934, 936, which have different and harder heads)
A suggestion: Sankyo heads have the exact dimensions of Elmo heads, so if you only use your precious GS 1200's for playback, it might be useful to replace the head with one taken from the higher end (dual track) Sankyo machines, such as models 700 or 800.
Hope this helps
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Maurizio
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Tom Photiou
Film God
Posts: 4837
From: Plymouth U.K
Registered: Dec 2003
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posted July 18, 2004 02:23 PM
That was good info, Mikes right, that would make a good techy bit so do send that in, Mike, your right about the Eumigs, My Brother reminded me that back along he had to have second hand Heads put into his 810D, as i understand it Eumig heads are quite soft, I did have an 840 Multiprocessor heavily used for recording and one track of the heads gave up. At least the Elmos's are easy to get to for cleaning. I do posesss a set of 4 pressure pads and springs for the heads of my 1200HD but i reckon,(fingers crossed) i'll never need them. I do treat the heads like a set of teeth,regular and gentle cleaning, don't let the dirt build up and you should be ok ![[Wink]](wink.gif)
Some of you blokes out there do have superb info on the electricle sides of the projectors and im sure there are many people who would appreciate you sharing through the FFTC mag, i'm a little limited on what i can do, mostley basic's but if someone could do a few it would fill some more pages. ![[Razz]](tongue.gif)
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Maurizio Di Cintio
Jedi Master Film Handler
Posts: 977
From: Ortona, Italy
Registered: Jan 2004
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posted July 19, 2004 12:02 PM
Thanks, folks, for your praises. Indeed I do write articles on several S/8 related topics, but in Italian only. Maybe one day I'll manage to translate them into English... We'll see.
As for the 940 haeds: I wouldn't be surprised if the sound head for track 2 stopped working for first. Being much thinner than the main track head, they are much weakier too. It's a real pity that these otherwise wonderful machines have such a weak part. On the other hand they are made of permalloy, a magnetic alloy which has excellent sound transmisison properties, though not so hard as sendust. This account for the excellent sound quality of almost all Eumig Series 900 machines. Fortunately the sound assembly of these projectors are very easy to open and clean, differently from the previous series. It is possible to remove the whole pressure pad system for cleaning. By using a curved small mirror (like the ones used by dentists) you can easily look at the heads and clean them. And after everything has been reassembled, there is absolutely non need to tune the pads whatsoever: very ingenious.
Finally another tip: since, as we have seen, the head for track too is so "softer" than the other one, it is really worthwhile to have two different sound pressure pads cartridges: one with all four pads working, the other one with the two pads relative to track two removed: in this way, no mechanical stress will be endured by the weakier heads when screening mono sound/striped films. Believe me, if you use the track 2 just when needed, this sound head will last much longer.
Cheers.
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Maurizio
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted July 19, 2004 01:47 PM
Hi Maurizio,
What a terrific tip about the 900 series sound head pads! I have two Eumig 926GL stereos, and one Eumig 938 stereo. The Track 2 head of the one 926GL has pretty well gone, as I used it for about 10 years befoe I got my Elmo's. However the other 926, which I only use for re-recording, is just fine. Also the 938 heads are like new, because I limit the play time on it because of the soft heads. I will now take the pressure pad off the old 926 and trim away the track 2 pads, and use that pad whenever I am showing just mono prints on the 938. I agree with you about the terrific sound quality of the Eumig 900's- about the best I have heard. I am a big enthusiast of the 938/940 machines. The stereo quality you get from dubbing from DVD with these machines is unbelievable.
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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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