Is a LOOP essential ?

Sorry if this is nonsense (I don't know much about the technical aspects of how theremins work), but couldn't you make a "fake" loop?

I mean, you could have your metal rod sticking out of the theremin, but insert that metal rod into something that would look like a loop.

Something like this (sorry for the horrible paint skills): http://imgur.com/jnYOL2r

"The plate antenna is the kind of brilliant idea engineers come up with when they do not consult with experienced musicians who play at the professional level." - Coalport

My first theremin experiments used plate antennas - That was before I knew anything about theremins or linearity or any of the other things that differentiate between a musical toy and a musical instrument.

From an engineering perspective, the plate at first seems like the obvious route - I would not be at all surprised if Lev explored this first (although he may not have - the idea of flat 'plate' capacitance sensors is perhaps more in our minds these days than back then, when there were no capacitive sensors - back then their focus was on radio, where antennas were the focus).

But one quickly finds the flaws - The major obvious flaw being that having both hands moving on the same axis causes interactions - The next (less obvious and more difficult to explain) is that (particularly for pitch) linearity from a plate does not seem as good as from a longer rod antenna.

The "fighting gravity" reason is not one thats obvious to me - but I accept it (since my heart failure, I find playing pitch and extending my arm for any length of time, is as exhausting as running up stairs - I do not have this problem with moving my hand up and down) I also find that it is far easier to control pitch using finger movement with a vertical antenna than with a horizontal plate (a plate utterly restricts ones fine tuning - the only way I have been able to somewhat compensate this is by using sideways horizontal movement of the hand for fine tuning when using a pitch plate)

Personally, I will never be able to play any conventional theremin.. I have my own personal project going to greate a theremin-like instrument I can play - this uses a capacitive "ribbon" I can slide my hand along.

The only reason I continue developing conventional type theremins is that I have invested so much R+D into them that I cannot just cut my losses and move on - Some sort of OCD stuff is probably in there as well - I set out to make the ultimate theremin, and cannot walk (or at least not voluntarily) away until I have at least produced something really good and brought this to market..

But, although I continue on this road, my heart is not in it the way it once was - I will never be able to play "my" theremin in a way that does it justice, it will never earn me real money, and I think the theremin concept is, and always was, complete folly.. I should be spending my time developing my theremin-like instrument which has a sane interface. Fortunately, much of my R+D applies to my new instrument, so its more of a parrallel road rather than a complete change in direction.

So all I want to do now is to close this chapter - get what I have been foolishly blabbing and boasting about for years, onto the market (ideally sell it lock, stock and barrel to someone else to manufacture and market) .. Perhaps continue supplying new designs to said manufacturer (here I go, leaving a crack in the door, LOL .. Who am I kidding? Can I actually turn this page? ;-) .. Or ideally, get EPE or Elektor to publish the design (discussions to this end are underway, and this is another reason I must complete a full prototype)..

Fred.

"Sorry if this is nonsense (I don't know much about the technical aspects of how theremins work), but couldn't you make a "fake" loop?" - AIKhwarizmi

What an extremely interesting idea!

Somrthing like that could probably be moulded quite cheaply in plastic (might even be able to make it from plastic tube bent when heated), could push over the volume rod, so it could be supplied as an accessory for those who wanted it, and would work with left or right handed configurations..

If made of a light material (thin ABS or perspex pipe, or perhaps even stiff closed-cell foam rubber) it could be cheap and cheerful. Those who never wanted to swap antennas from left to right could glue this fake loop on the rod, so that the directional sensor side was fixed to point to the player..

Only the rod section of the loop would be sensitive, so it wouldnt function exactly like a real loop.. But I think that the directional nature of the volume rod inside it would give a reasonable approximation of a loop.

Real interesting idea! Thank you verry much!

Fred.

AIKhwarizmi' picture:

 "sorry for the horrible paint skills"

Nothing horrible here! - You conveyed the idea clearly, far better than many words could!

I'm glad you like the idea! I feared that it might not be doable for some technical reason.

The melodia doesn't have a volume anything... Rob loves it :)

I thought it would be strange playing the Melodia, however the technique and attack is almost the same as though a loop was there.  

Particular thanks to AlKhwarizmi for his idea and Thierry for his feedback, and to everyone for your comments / suggestions. Due to these I have redisigned a bit, thrown out the idea of having the option of two horizontal antennas, and come up with this:

1.) Original concept of vertical pitch with horizontal rod volume antenna, but option for horizontal pitch antenna removed, and "fake loop" option (which can be fitted over the volume rod) shown:

2.) An "extended pitch arm" option is added - When no antenna is plugged into the top of the theremin, this is detected, and the side connecting sockets are re-assigned (and the tuning reconfigured) so that these sockets accept a pitch extention arm into which the pitch antenna is plugged.

This "reconfiguring" also activates an internal "invisible loop" so that the top of the theremin becomes the volume antenna.

Mechanical details are something of a headache, and I am planning to put a microphone stand connector on the bottom of the extention arm under the antenna for optional added stability.. But at present my focus is on tyhe electronics.

Fred

Photo below shows where im at - mess of cables etc, but directional antenna behaving itself under test.. It really doesnt see anything behind it..

Another variant on the above (one I like) - Having an additional pitch antenna extension socket at the back of the theremin, this connects via a lead on the ground to a pitch antenna mounted on a seperate microphone stand..

One then has all the above options as well - except that I probably wouldnt have a socket for a stand on the bottom of the pitch extension arm.. In fact, I wonder if the pitch extension arm is redundant.. I for one would much prefer a seperate, stable free-standing pitch antenna to an arm which can be bumped and prone to wobble.

Edit >> I am actually wondering if the above is all that is needed.. Does one actually need the option of a pitch antenna on the top with a volume arm sticking out the side? -

This construction would be far simpler, left or right handed defined by where you place the antenna, stable pitch antenna, stable volume antenna you can rest your hand on if you wish, automatic attenuation / muting when adjustment is made to the theremin, less problem of pitch interaction from a headphone lead, the pitch controls could be fitted into a pitch antenna mounting box, so one never accidentally de-tuned the theremin when adjusting something else..

Any comments welcome - but this will be my first implementation because its the simplest.

The wonderful thing about the traditional loop antenna is its negative space - that is, the hole in the middle of it. 

You have probably noticed that the volume hands of many thereminists dip and dive and flutter around the volume antenna. The traditional antenna is designed so that it slopes downward on an angle TOWARD the player, and is bent into a loop so that it does not form an obstruction. You can sail right into the middle of it, but you never touch it and it is never in the way.

The problem with a plate, or with using the top of the instrument as a volume antenna is that the empty space is no longer there. That large, flat surface area is going to impede free flight of the volume hand, and it is going to get touched.

Over the years, I have seen many people attempt to improve upon Leon Theremin's original designs. They reposition and reconfigure the antennas, they reverse the response, they do all sorts of things without realizing that all these "improvements" were experimented with extensively back in the 1930's and, for one reason or another, rejected.

I like the idea of having a separate pitch rod, despite meaning that two mike stands are required. Firstly it means I can adjust the distance between the pitch and the volume electrodes to my liking, and secondly, from a performance point of view, part of the thrill of playing live is how exposed the performer is to the audience - this arrangement removes the last obstacle between audience and performer. Thirdly it is good for both left and right handed use.

With regard to the volume, I do feel, as Coalport does, that a loop is a good idea. (If for no better reason than to stop me slapping the top of the unit when i get overly enthusiastic.) Perhaps AIK's idea of a false loop could be adapted to this be putting a plastic ring supported on pillars above the top of the theremin to give the player something to aim at.

"Over the years, I have seen many people attempt to improve upon Leon Theremin's original designs. They reposition and reconfigure the antennas, they reverse the response, they do all sorts of things without realizing that all these "improvements" were experimented with extensively back in the 1930's and, for one reason or another, rejected". - Coalport

I accept this - I am sure that Lev did extensive evaluations and that the way the theremin (and particularly its physical form) came to be was no accident.

I think that these "refinements" Lev introduced are possibly of vital importance for the few truly precision thereminists on the planet, but probably of little or no importance to the vast majority of theremin players - for this majority, I suspect that other constructions could be advantageous.

The technology to implement a seperate relocatable pitch antenna was not directly available to Lev (it would have meant building two seperate instruments - one for pitch and one for volume) and in fact has not really been easily available for modern theremins - although having seperate pitch and volume sections is simpler to achieve with solid state than with valves -

"With regard to the volume, I do feel, as Coalport does, that a loop is a good idea. (If for no better reason than to stop me slapping the top of the unit when i get overly enthusiastic.) Perhaps AIK's idea of a false loop could be adapted to this be putting a plastic ring supported on pillars above the top of the theremin to give the player something to aim at." - Gordon.

Thanks for confirming my fears, Gordon! ;-) -

It seems that the loop must stay - The "false loop could be adapted to this be putting a plastic ring supported on pillars above the top of the theremin" might be a good idea, but it would still be different..

So I will play safe.. the "design" I have shown above could easily have a conventional loop stuck into the socket on either side - extending the loop on an arm would not be needed as the pitch antenna can be moved to an appropriate distance - If the loop is conventional (non-directional) then the same loop can be swapped to left or right hand sides

The only disadvantage in the whole scheme that I can see is the need for a seperate stand for the pitch antenna if this mode is used, but for performers this could be an advantage "from a performance point of view, part of the thrill of playing live is how exposed the performer is to the audience".

So at present, I propose the following options:

1.) Theremin unit with antenna mounted on its top, having volume antenna rod plugged into either side, and option of "dummy loop" on the end of this volume rod.

2.) Seperate relocatable Pitch antenna, Theremin unit with "invisible" volume antenna on its top face.

3.) Seperate relocatable Pitch antenna, Theremin unit with conventional volume loop plugged into either side.

All of these options would be available from a standard build - Thereminists could choose a "real loop" or a "rod loop" as extras - The pitch antenna being operable on top of the theremin if a rod-loop is used, otherwise as a seperate microphone stand mounted antenna used with either the hidden loop, or with a real loop.

Thank you all..

As to when and if this will ever materialize, I cannot say -

I need to (am being forced to) move out of my home in the near future, and unless I can find a way to move with enough space to continue my "business" and get finance to put the stuff into production, my "journey" is over.. At present I cannot even see a way to survive and get accomodation for myself, let alone do any manufacturing.. So its all looking really grim.

I hope to build one prototype in the next few weeks if lifes other major traumas dont prevent this.. then perhaps try to sell this complete with all the designs and data and hope someone will buy the package and put it into production.. I am in the process of doing my final accounts to close my business (or perhaps put it into suspension).. Unless fortunes face looks my way in the very near future.

Fred.