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Akai SS-1 Universal Synthesizer

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chucky3042

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Its an indicator, recon thats why the blend (subtraction) is done with the high step up ratio transformers to minimize the distortion it would cause. Really crap design!
 

chucky3042

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And now we are talking the very early "teen age" beginnings of the Surround Master (shameless promotion mode enable). My next attempt at surround was at around the age of 13 in 1971 with an Electronics Australia project (really great magazine died eventually and sorta became the vastly inferior Silicon Chip Magazine) with a simple transistor circuit. This is not exactly it as I would need to dig into my archive of magazines going back to 1969 and I am too lazy. But broadly this is the same sorta thing, I bet this is similar to the circuitry of the Akai SS 1.

View attachment 55642
Actually its a really carp circuit as there inter channel mixing, weird
 

Soundfield

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I've thought multiple times that a fun little project to build would a simple decoder with complimentary or push/pull control of the blending coefficients. In other words turn the pot to one extreme & you get un-altered stereo in front, full L-R in back. Go the other direction & have full mono blend in front & full stereo in rear. Obviously this could not be used to correctly decode QS/RM because at the mid point the blend would be matched but .5.
Reading the user manual that Chucky posted I think that's more or less what the SS-1 did - would be very interesting to see the circuit diagram, but I can't find it
 

Soundfield

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Hey chaps, I really have gone nuts on this. Here is a transistor based SQ decoder, be fun to try!!!


View attachment 55647
That's very much the style of decoder that Sony used in their very first outboard decoder boxes, with the classic 10-40 ratio blend resistors. They performed so badly it almost killed SQ off at birth!
 

Soundfield

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Here is one more if you guys get bored, non SQ
View attachment 55649

The blend ratios are all wrong!
I don't see any blending, just a load of largely unnecessary buffer stages and a unity gain summing amp for the (pointless) centre and a unity gain subtracting amp for the rears. Just a Hafler circuit using more components than required!
 

Soundfield

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Pretty sure it used the good ol,l wiring trick with a pot....the Hafner Dynaco style and yes that was my first surround system at around 12 years of age, so it was the first Surround Master!!!!!!

View attachment 55640
The trouble with the Dynaco style of 'speaker matrix' adapters (and their ilk) was that they really only worked properly if you used single drive unit (i.e. full range loudspeakers) for the rears. Theses adapters put the rears in series and hence any crossovers they had would also be put in series!! I think that's why a lot of people might have tried them with their fancy multi-drive unit speakers and thought it sounded terrible (which it would of course) and blamed the whole quadraphonic concept !
 

par4ken

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The trouble with the Dynaco style of 'speaker matrix' adapters (and their ilk) was that they really only worked properly if you used single drive unit (i.e. full range loudspeakers) for the rears. Theses adapters put the rears in series and hence any crossovers they had would also be put in series!! I think that's why a lot of people might have tried them with their fancy multi-drive unit speakers and thought it sounded terrible (which it would of course) and blamed the whole quadraphonic concept !
The reason for low bass output from the rears is due to the fact that bass is mono on most recordings and cancels out. Using identical speakers places crossovers components in series but the drivers are in series as well so the frequency response should not change. Results vary recording to recording with this system, sometimes amazing sometimes terrible. Play mono recordings through it and hear only noise from the rear.
 

MidiMagic

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The reason for low bass output from the rears is due to the fact that bass is mono on most recordings and cancels out. Using identical speakers places crossovers components in series but the drivers are in series as well so the frequency response should not change. Results vary recording to recording with this system, sometimes amazing sometimes terrible. Play mono recordings through it and hear only noise from the rear.
Not quite true. Notice the resistors to ground in the back circuits. this changes the decoding angle so it is not just L-R. There will be a lower level sound of the mono source in the back speakers.

This also happens in the EV, QS, SQ, and SQ 10/40 blend.
 

Soundfield

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The reason for low bass output from the rears is due to the fact that bass is mono on most recordings and cancels out. Using identical speakers places crossovers components in series but the drivers are in series as well so the frequency response should not change. Results vary recording to recording with this system, sometimes amazing sometimes terrible. Play mono recordings through it and hear only noise from the rear.
I have not heard a low bass output criticism of the Hafler system before. By "bass is mono on most recordings" I assume you mean bass is centrally placed. However, I don't know what sort of music / recordings you listen too but on most of my classical stuff the bass is rarely exclusively, or indeed largely, centrally placed, as that's not how orchestras are laid out. I routinely use a Hafler style extractor (at line, not speaker level) and there is plenty of bass content in the rears.

Placing multi drive unit speakers in series is a terrible idea. The frequency response and impedance characteristics are completely screwed up. I don't understand your assertion that the drive coils being in series with the now series connected elements of the crossovers mitigates the problem.
 

chucky3042

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I have not heard a low bass output criticism of the Hafler system before. By "bass is mono on most recordings" I assume you mean bass is centrally placed. However, I don't know what sort of music / recordings you listen too but on most of my classical stuff the bass is rarely exclusively, or indeed largely, centrally placed, as that's not how orchestras are laid out. I routinely use a Hafler style extractor (at line, not speaker level) and there is plenty of bass content in the rears.

Placing multi drive unit speakers in series is a terrible idea. The frequency response and impedance characteristics are completely screwed up. I don't understand your assertion that the drive coils being in series with the now series connected elements of the crossovers mitigates the problem.
Agreed but the common bass signal typically cancelled out L-R so the rear speakers really did not need to be full range making the technique suitable to the satellite speaker concept. A good reason to make bass common in recordings is to get the benefit of 2 sets of drivers working together to push enoigh air to extend the bass, in addition to the wrong myth that bass is non directional below 150 Hz . Our tests showed that on sine wave pure tone bass is actually non directional to 800 Hz but on band limited pink noise was totally directional down to 35 Hz!! Explains why I can always point to where the subwoofer is for the first 30 seconds before my brain masks the position.
 

par4ken

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I have not heard a low bass output criticism of the Hafler system before. By "bass is mono on most recordings" I assume you mean bass is centrally placed. However, I don't know what sort of music / recordings you listen too but on most of my classical stuff the bass is rarely exclusively, or indeed largely, centrally placed, as that's not how orchestras are laid out. I routinely use a Hafler style extractor (at line, not speaker level) and there is plenty of bass content in the rears.

Placing multi drive unit speakers in series is a terrible idea. The frequency response and impedance characteristics are completely screwed up. I don't understand your assertion that the drive coils being in series with the now series connected elements of the crossovers mitigates the problem.
I seldom listen to classical but almost all popular recordings employ mixed bass, especially true in the LP days. Other than perhaps poorer damping I don't see what difference series connecting identical speakers would make, but if you can afford complex multi-driver speakers for the back then you should use a separate amp and decoder/processor anyway.
 
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