Are Two (sound) Heads Better than One?

[Steve Klare]

I present to you the example of an Elmo ST-800M:
.

-a single track machine, yet with two soundheads.

I used to think maybe one was a recording head, but the other was playback only, The problem with that is given the maybe three or four frame separation between the two heads, there would be a built in loss of sync. between record and playback.

I'm working on a new idea that the upstream head is a demagnetizer so that when a fresh soundtrack is recorded, the stripe has no remnants of old recordings and other noise under the new track. In this case, playback and recording are both through the downstream head.

-any better ideas?

[Nantawat Kittiwarakul]

To my understanding, yes...that's the case.😀

Essentially this is more or less the same as usual 2-head cassette recorder/player. The first/upper head is the erase head which stays idle when in playback mode. The lower one will serve double purpose as recording/playback head. Besides the head most of the components also serve dual function too by means of recording/playback switch. Therefore anyone capable of servicing cassette tape player should have no problem fixing audio board in most super8 sound projector - at least in theory.

[Joerg Polzfusz]

Or your projector supports special sound-fx like „sound on sound“ = mixing existing sound (played back from head 1) with additional sound (from microphone/LP/MC, recorded on head 2)?

[Joerg Polzfusz]

But it looks like it’s one eraser head and one recording head - like on the Elmo ST1200D (see attachment).

[Steve Klare]

Thanks Guys!

-this is interesting.

[Rob Young]

Steve, your assumption is correct. It's an erasing head. Without it, every time you record something, the old recording would linger there too, as Nantawat says, like a tape recorder.

I recall you have a twin track Elmo ST1200? That has 2 erase heads prior to the main 2 playback heads too. So the question is when are 4 heads better than one.

Sound on sound works by allowing the user to vary the level of erasure taking place by the erase head, thus letting you "add" new sound on top of the existing recording. I always found the problem was that, even with gentle settings, the original sound lost most of the top end as a result of being partially erased.

Without an erase head, all super 8 projectors would be sound-on-sound, on-sound, on-sound...

On the Beaulieu 708el, there is the addition of a second set of replay heads after the main heads, so that you can actually monitor the recording as it happens, albeit a few frames late...so the question with a Beaulieu is, when are 6 heads better than one.

[Steve Klare]

I do have an ST-1200HD-M, but I think the math on that would be "Are Four Heads Better than Two?"😊

I never realized the sound on sound function worked that way: it makes sense!

[Rob Young]

Well now...come to mention it...the sound-on-sound feature of super projectors works in practice by turning an input pot up or down from the new source.

Hmmm...I used this a lot as a kid mixing my home movies. I always assumed it altered the erasure level as well as managing the input gain of the new sound...but, does it actually vary the level of the erase head, or simply disengage it entirely and allow the user to vary the overlay recording from 0 to 100 percent, thus still leaving the original track in there somewhere...

I can vouch that over use pretty much destroys the original track, especially in the high fidelity, but I now wonder if this was simply the result of inputting a full on signal on top of the original track...

Crickey, you lot make me re-think my entire childhood sometimes!

EDIT: Wait, of course I must be wrong. With sound-on-sound the erase head must be disengaged completely as it is either on or off. The newly added sound is simply a user level of variable modulation added over the existing recording.

When I stop and think, I know this, because when I do a re-recording using my Goko editor, I always give the film a run through on full record / erase to "clean" the original track away, as when using the mixing facility to re-record (even at full level), the original track will lurk there somewhere unless gone completely.

Doh..so, sorry Steve, sound-on-sound must work by disengaging the erasure head. Whereas a new recording in full on record mode uses the erasure heads to wipe the original sound just prior to the new recording taking place at the sound head. SOS allows the user to simply vary the incoming modulation over the original track...my bad!!!