Debunking the myth that multiple speakers per "rank" are necessary

[David Pinnegar]

Hi!

Elsewhere there has been much recent controversy as to how many channels an electronic organ should have. It has been asserted often that it's better to organise an instrument so that different notes come out of different speakers on account of "beat notes", the difference of the frequencies between the notes. It has been said so often that people have believed it, including myself, that the beat note resulting from two notes would be more prominent when the notes came out of one speaker rather than coming out of seperate speakers.

This evening I did the experiment:
http://www.youtube.com/watch?v=ntPblldKpBw

Best wishes

David P

[dragonser]

Hi,
I always thought the reply to the question was " as many as reasonably possible " !
an interesting experiment  .....
I'm going to listen to the you tube clip again when I am less tired.

regards Peter B

Hi!

Elsewhere there has been much recent controversy as to how many channels an electronic organ should have.

Best wishes

David P

[David Pinnegar]

Hi!

After doing three YouTube video recordings on this subject, I have concluded that multiple speakers do no more than give illusions of space in a home environment.

What really causes the unpleasant sounds of beat frequencies is volume - on quiet instruments and quiet stops, one hardly hears them - one only hears them when one is very close to the sound source and at a high sound intensity:
http://www.youtube.com/watch?v=XmCgZq6Lmm0

I'm going to put more into the temperament thread about this . . .

However, in the nature of realism, just as it would be ridiculous to take the sound of the Albert Hall organ and squeeze it through a keyhole, likewise it's ridiculous to sqeeze it through perhaps 8 inch cylindrical holes which are what loudspeakers can be compared to.

One might therefore toy with the idea of a rule to determine the minimum number of speakers necessary to make an electronic organ sound natural in a large environment. Perhaps one might look at the vibrating area of a pipe in terms either of its mouth opening or of its diameter, or a combination of the two. In this way, at Tenor C one might expect an 8 inch loudseeaker to reproduce two 8ft Diapason pipes and a 4ft Principal. Perhaps at middle C, three 8ft Diapasons and a couple of 4ft Principal pipes. An octave above treble C, perhaps it might reproduce a dozen pipes naturally. Perhaps 16ft bottom C needs a 12 inch speaker all to itself . . .

However, certain speaker constructions force a speaker to fire through a slot, compressing the air, and one can compress with a ratio of up to 4:1 without distortion occuring. For this reason, one might be able to compress up to 4 times as many pipe areas per speaker, multiplying up the numbers suggested above.

If such a rule is followed, then one is going some way to the concept of shifting air in terms of the vibrations of organ pipes.

Best wishes

David P

[revtonynewnham]

Hi

Interesting demonstration.  Obviously, the results for those of us listening on home computers will be compromised because what we're hearing will be modified by the speaker & room characteristics - and where 2 sound sources are used, the sound we hear is electronically mixed by David's camcorder mics.

That said, I could hear most of the beats, and on some demos, there was a noticeable difference between single and dual source (although as was pointed out, some of this is down to the relative distance of the speakers used from the mic).

I suspect though that the real differences will not show up until a significant number of notes & stops are drawn - and that's going to very difficult to demonstrate.  It's well known that the softer stops on electronic organs work well and (usually) sound good, but that things fall apart with larger combinations, and empirically, multiple loudspeakers and hence acoustic mixing of sounds does make an improvement - I guess partly because the inevitable intermodulation distortions of a typical moving coil loudspeaker attempting to follow a complex waveform are much reduced, as each speaker has less work to do.  Potentially also any intermodulation distortion in the amplifiers will have less effect.  Conversly, because the sounds are now added acoustically, the characteristics of the space will have a greater influence, as early reflections will vary in timing and angle of arrival depending on which speaker(s) are producing the various sounds.

An interesting topic.

Every Blessing

Tony