The Legacy of Dr Bauer

[Soundfield]

https://en.wikipedia.org/wiki/Matrix_decoder^^^
Position Encoder
An N/2 encoder that encoded every position in a 360° circle - it had 16 inputs and each could be dialed to the exact direction desired, generating an optimized encode. (best description I've read so far)

Really? It's the worst single line 'description' I've ever seen as the author fails to identify whether "it" was a theoretical construct or a real world piece of equipment. The phrase "generating an optimized encode " is particularly misleading as the only real world example of this type of equipment (the CBS 4212) merely enables an optimised encode to be produced when connected to an SQ encoder.

 

[kfbkfb]

AFAIK, the 4212 is a standalone device (does the entire SQ encode, additional equipment isn't needed), maybe this thread will help explain:

https://www.quadraphonicquad.com/forums/threads/buddy-rich-sq-encoded-laserdisc.14897/

Kirk Bayne

 

[par4ken]

I don't see as a 'simplification' as that box performs those two functions. You could show those in dotted boxes inside the SQ Encoder if you wanted to, but that doesn't change the physical implementation (in terms of equipment boundaries). Anyway the whole point of this argument was to dispel the false idea that the Positional Encoder was the unit in which forward and backward SQ encoding was conducted!!

The simplification is that it shows only four inputs to the encoder. It sounds like the 4211 could/would be used as a position encoder already. Yes the Positional Encoder appears to be nothing more than a panning controller box.

 

[Soundfield]

AFAIK, the 4212 is a standalone device (does the entire SQ encode, additional equipment isn't needed)

"AFAIK" - so is what you 'know' based on some robust engineering information regarding the build of the CBS 4212 Position Encoder? If so I hope you will share it with us.

 

[par4ken]

I have just realised that the CBS Position Encoder was not an SQ Matrix Encoder and was used earlier in the production chain. The use of the term 'encoder' in two different contexts is rather confusing.

View attachment 68518

The "Postion Encoder" didn't really encode anything. It was what we in the engineering trade would have called a "bodge box"!

Just wondering about the source of the diagram that you posted.

While it appears that the 4212 is really just a panning controller that outputs it's signals to the 4211 encoder. Some descriptions say that the 4212 outputs phase shifted signals (which implies some kind of encoding action) and that the 4213 removes the phase shifting for the discrete output. Not all of those statements can be correct.

Again I would love to see the schematics of the actual equipement to be able to make sense of the many conflicting statements.

My idea of a "Position Encoder" would have separate inputs for each position and maybe but not necessarily one or two pan pots.

 

[kfbkfb]

No, I have a photocopy somewhere that shows the Lt and Rt amplitude/phase info for (IIRC) each of the (4212) 16 position selections, I worked thru the equations many years ago just to see what the improvement was as compared to a regular (4200) SQ encoder.

(I'll see if I can find my photocopy and scan it [I know, I said I'd do that before])


Kirk Bayne

 

[Soundfield]

Just wondering about the source of the diagram that you posted.

While it appears that the 4212 is really just a panning controller that outputs it's signals to the 4211 encoder. Some descriptions say that the 4212 outputs phase shifted signals (which implies some kind of encoding action) and that the 4213 removes the phase shifting for the discrete output. Not all of those statements can be correct.

Yes they can. The position encoder introduces phase shifts where necessary to force positional outcomes from an SQ encoder (that would otherwise be imprecise, ambiguous or not permitted) such that a downstream decoder could reproduce them in the intended location. They apparently caused audible artefacts which had to be removed for non-SQ encoding (i.e. discrete) purposes. All tricks just necessary because of the severe failings of a non-regular matrix encoding technique of course.

 

[par4ken]

Yes they can. The position encoder introduces phase shifts where necessary to force positional outcomes from an SQ encoder (that would otherwise be imprecise, ambiguous or not permitted) such that a downstream decoder could reproduce them in the intended location. They apparently caused audible artefacts which had to be removed for non-SQ encoding (i.e. discrete) purposes. All tricks just necessary because of the severe failings of a non-regular matrix encoding technique of course.

It would have made more sense if the 4212 outputted non phase shifted signals as well, already mixed to discrete quad, rather than to have to remove them with yet another module! If the phase shifts are merely phase inversions for some positions the sonic impact wouldn't be too bad, but if it adds more all-pass circuits then why would the unit not be designed to output a fully encoded SQ signal, to still require further encoding makes no sense at all!

 

[Soundfield]

Just wondering about the source of the diagram that you posted.

As attached-

 

[MidiMagic]

Note that adding phase shifters in the position encoder does not give the same output as using two encoders (forward and backward). This is the result of a signal being psi-shifted twice with a position encoder that shifts phase too.

I also noticed that the diagrams for the forward-oriented and backward-oriented encoders were accidentally traded in the article. They are not traded in the copy I have (which came directly from Mr. Bauer, not from AES .)

 

[kfbkfb]

Here's the vectors for the 4212 SQ Position Encoder (Lt and Rt content for optimum SQ encoding):

The numbers are a little hard to read:
1.00 0.71 0.92 0.38


Kirk Bayne

 

[Soundfield]

Here's the vectors for the 4212 SQ Position Encoder (Lt and Rt content for optimum SQ encoding):
The numbers are a little hard to read:
1.00 0.71 0.92 0.38
Kirk Bayne

No. Those are the vectors that are produced by the 4211 SQ Encoder having been fed phase and amplitude optimised signals from the position encoder.

In fact, that very HFN/RR article of March 75 (written by Bauer) gives further proof that the Position Encoder was not itself an SQ encoder and one or more of them had to be connected to an SQ Encoder to produce a matrix encoded output. He makes this entirely clear in the first part of the article on the previous page where he describes the 4212 Position Encoder as a “convenient accessory” to the 4211 SQ Encoder:

Note in particular that he says that it is the 4211 SQ Encoder that "delivers two coded signals, LT and RT" (and he does not say this is of the 'accessory' position encoder).

The differences between the two bits of equipment highlight their different functions. Clearly the Position Encoder (fig.2b) wasn't capable of being used as an SQ encoder in a studio environment as it doesn’t have level meters (and in fact it doesn’t even have an on /off switch – I think it might be entirely passive). Contrast this with the facilities on the actual SQ Encoder, the 4211 (fig2a):

 

[kfbkfb]

https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1973-07.pdf#page=20
Looks like the 4211 Encoder Module is a universal (SQ encoding) device, it can be used to encode a previously mixed Quad master tape (via the 4 corner inputs) and accept 4212 (outputs) for new Quad mixes.

It makes no sense to further process (change amplitude/phase) the outputs from SQ position encoders, so maybe the 4211 acts only a summing device for 4212 outputs.


Kirk Bayne

 

[Soundfield]

https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1973-07.pdf#page=20
Looks like the 4211 Encoder Module is a universal (SQ encoding) device, it can be used to encode a previously mixed Quad master tape (via the 4 corner inputs) and accept 4212 (outputs) for new Quad mixes.

It makes no sense to further process (change amplitude/phase) the outputs from SQ position encoders, so maybe the 4211 acts only a summing device for 4212 outputs.


Kirk Bayne

The article you attach once again makes it clear the 4212 is simply a box of phase / amplitude pan pots.

The only CBS unit with an SQ Encoding function is the 4211. As I have shown earlier it has four inputs that may be fed from a four track tape or from a number of 4212 Position Encoders. The outputs from the four track tape are not SQ encoded , nor are those from the pan pots in the Position Encoder, that is the very reason why they can be summed at the input stage of the SQ Encoder. The combination then being SQ encoded to give Rt and Lt.

 

[par4ken]

I don't like to keep beating a dead horse but actually the Audio article is perhaps the clearest of them all, It would appear that the 4211 is the real position encoder. The 4211 contains forward and backward oriented encoders and is capable of doing diagonal splits. Yes with the 4211 a discrete mix can be encoded directly (in forward oriented mode). The so called position encoder contains pan pots but it would require more than four outputs to the 4211 encoder to work. That was even shown in one of Soundfield's diagrams, it showed eight outputs, one set to the forward oriented encoder and the other set to the backward oriented encoder. The discrete module has to convert the multiple outputs back to a four channel signal, in order to create a discrete master. If the the position encoder outputted only four signals there would be no need for the discrete module at all.

 

[Soundfield]

The so called position encoder contains pan pots but would requie more than four output to the encoder to work..

Why do you say that? The AES paper shows pan-pots having four outputs connected to the SQ encoder-

 

[par4ken]

Why do you say that? The AES paper shows pan-pots having four outputs connected to the SQ encoder-
View attachment 68988

You are only showing half of the circuit. Look back to your's and Midi-Magics previous posts.

 

[Soundfield]

You are only showing half of the circuit. Look back to your's and Midi-Magics previous posts.

Of course I am - but the second half is identical for the backward encoder - it also only has four inputs.

You said you would require more than four pan pot connections to an encoder. That could be said to be true but only if you choose to consider, for no apparent reason, the two encoders in the 4211 as a single encoder with 8 inputs!

The discrete module has to convert the multiple outputs back to a four channel signal, in order to create a discrete master. If the the position encoder outputted only four signals there would be no need for the discrete module at all.

No, I think not. The Discrete Module is not used to change the number of signals lines (it is four) but to remove the phase changes added by the Position Encoder to "optimise" the performance of the SQ encoder:

 

[par4ken]

Of course I am - but the second half is identical for the backward encoder - it also only has four inputs.

You said you would require more than four pan pot connections to an encoder. That could be said to be true but only if you choose to consider, for no apparent reason, the two encoders in the 4211 as a single encoder with 8 inputs!



No, I think not. The Discrete Module is not used to change the number of signals lines (it is four) but to remove the phase changes added by the Position Encoder to "optimise" the performance of the SQ encoder:

View attachment 68992

I believe that to be incorrect. Look at pan pot S5, it connects to both the forward and backward encoders, that's the only way it will work. The original article is showing how the panned signals are connected, the black dot indicates the signal position. As I said before many articles and sometimes even information from the manufacturer is dumbed down in a effort to explain the operation to non-technical people. You have to wade through many different sources to get to the truth, Again the actual schematics would reveal exactly what is going on and eliminate all the speculation.

 

[kfbkfb]

Yes, I have nothing more to add to this SQ encoding topic, other than to 2nd the idea that the schematics of the 4211 and 4212 would reveal the truth.


Kirk Bayne