Stereolith Loudspeakers Question

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Elias

Elias

Member
Joined 2003
Hello,

Stereo signal from one loudspeaker is an interesting idea.

I would like to keep it dipole to avoid the problems associated to the box.

How about something like this. Two dipoles cross each others. The other is fed R+L signal and the other R-L signal.

Red indicates the radiated signal at the given direction. Here we can have L+R directly towards the listener. R and L signals are pointing 45 degreed sideways which means they can be reflected from side walls to the listener. 'Surround' signal L-R generates 'ambience'.

Any experience of this, anyone?

- Elias
 

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Elias

Elias

Member
Joined 2003
A variation. Cross at different angle and feed R and L signals. This will produce same radiated signals.

I think in practise the first version might be better because direct signal comes from one speaker (L+R), but in theory they are the same.

- Elias
 

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simon dart

simon dart

Member
Joined 2004
Very interesting Elias: M+S Stereo! ( Mid and Side) I had this thought too.

I used to work in broadcast sound in the BBC in the 90s where we used to use this system for originating sound for TV. The great advantage with it is you can vary the image width to suit by altering the gain of the S signal. This would surely be a worthwile experiment. I don't have any dipoles to try it though.

:(
 
Elias

Elias

Member
Joined 2003
Hello,

simon dart said:
...
M+S Stereo! ( Mid and Side)
...
I used to work in broadcast sound in the BBC in the 90s where we used to use this system for originating sound for TV. The great advantage with it is you can vary the image width to suit by altering the gain of the S signal. This would surely be a worthwile experiment. I don't have any dipoles to try it though.
Click to expand...

Very interesting. I suppose it was studio environment you used to listen? How about in normal reverberant living rooms?

There must have been good reason for BBC to use this system, can you reveal what was it? Anything related to perception of image or similar reasons?

You can do a dipole by placing two monopoles back to back and driving in opposite phase. For the system I draw, you need then four small boxes. Like a cube, speaker element on each horisontal side.

Tell more of your listening experience on this! :)

- Elias
 
D

david yost

Member
Joined 2005
Very interesting discussion, all.

Elias: I have a pair of old Epicure M400+ speakers that are somewhat like the dipoles you describe in that they are a 40" tall square box with a 2-way speaker system on each of the 4 vertical faces--an early 70's omni. I may try your proposed connection and will report on sound. Unfortunately, all of the woofers share a common volume, so bass alignment will be shot to hell.
 
simon dart

simon dart

Member
Joined 2004
Sorry Elias, I should have explained more clearly. My experience with M/S Stereo was a coding technique as applied to microphones and post production, not reproduction through speakers, monitoring was always matrixed back to conventional L-R stereo.

Link

Making a loudspeaker to work in a suitable room using M/S is not something I've seen done before, but as suggested by you, it makes perfect sense to me.

The mono component would be reproduced by the dipole facing the listener free from typical stereo phase confusion. The difference component by the other dipole exciting the room boundaries. The percieved image width could be manipulated very easily by altering the gain of the S component to match the room.
 
graaf

graaf

Member
Joined 2007
interesting Stereolith-related patent:
http://www.patent-de.com/19971023/EP0677234.html

unfortunately (for me) description is in German, quite long and complicated, a lot of technical language, I am not able to grasp it

can anyone help?

here are alternative English summaries:

Abstract not available for EP0677234
Abstract of corresponding document: WO9415439
A process is disclosed for producing polarized acoustic fields. The directionality thereby obtained in a very wide auditory range, even with a very small monolithic, purely passive system, results in a subjectively unusually broad spatial stereo effect. The ability of bodies (acoustic "conductors", including "insulators" or action reflectors for mirror sources) to create at least one spatial preferred direction for the wave progression by means of internal structuring, special geometries and surfaces is exploited to this end (polarization). Longitudinally structured bodies, especially clusters of capillary tubes, have this ability and favour one longitudinal component of the acoustic progression. The record-side acoustic 3-D space appears to be reproducible in phase using acoustic transducers according to the process to a large extent without electronic aids. However, active smoothing of frequency-response and phase-response advantageously compensate for certain system-related features. Electronic delay units simulate the behaviour of the enclosure of a system according to the invention and improve its characteristics.
Click to expand...
see: http://www.freepatentsonline.com/EP0677234.html

Abstract of CA2152611 Described is a process for the generation of polarized acoustic fields: By way of directivity, an unusually broad, spatial stereo effect is created in an extremely large listening area, even with very small monolithic systems. The ability (internal structure, geometry, surface, resonance) of bodies (acoustic "conductors", including "insulators" or "reflectors") to form at least one preferred spatial direction is utilized (polarization). It appears that the acoustic 3-D space on the recording side can be reproduced in an equiphased manner with process-conforming sound transformers, already largely without electronic aids. However, the latter, in the form of propagation time elements or active frequency or phase response smoothers, favorably compensates for system-specific peculiarities.
Click to expand...
see: http://www.wikipatents.com/ca/2152611.html

judging by what I can undestand and by patent drawings available at "freepatents" I suppose that it was applied in 1990's Grundig "Space Fidelity" music systems

I once had opportunity to examine such "Space Fidelity" thing speakers section
it was horizontally placed aluminium alloy tube 60-70 cm long with small about 10-cm midbass drivers pointing to the sides (mono woofer was installed in separate section) and small dome tweeters also pointing to the sides but slightly toed in towards listener
the two midranges shared common volume (the tube was not divided in two) but there was a kind acoustic resistance "thing" in the middle, of fine tubes type
whole "Space Fidelity" music system as such was awful ugly junk BUT the speaker section worked (in terms of spatial reproduction of sound) as advertised and very similar to Stereolith

they later discontinued "Space Fidelity" loudspeaker setup completely and turned to "Magic Fidelity" ;) ;)
"corporate product policy" ;)
I think that "Space Fidelity" setup was undeservedly trashed together with those failed miserable ugly music systems

the patent looks serious

best regards!
graaf
 
graaf

graaf

Member
Joined 2007
Elias

Elias

Member
Joined 2003
Hello,

Stereolith = a tube in which both ends attached elements sharing same volume produce L and R signals in addition some "propagation time elements or active frequency or phase response smoothers" i.e. a passive cross-over/equalizer to compensate for "system-specific peculiarities"?


- Elias
 
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