Would you use this _real_ Leslie? AUDIO DEMO

[Hink]

It's just a whole lot cheaper and better to have moving reflector. I think a stepper motor could do this, and if the stepper motor was under VST control, that would be brilliant. I've suggested this idea on another forum a long time ago, and got zero interest and much heckling.

reflector=delay (very small)...might work, might be mud

[guitarzan]

It's simply sound panning - which is nothing like the beautiful Leslie chorus effect. There would be zero pitch bending, therefore zero chorusing. All you would have is a stepping volume attenuation, with stepping phase issues. If the goal is to have something like a home organ consol, it might be interesting - if disturbing. But if the goal is to then re-record it, and sound somewhat like a Leslie, it would be complete failure.

A better compromise might be to use the VST to apply the missing doppler shift, and send this to stationary speakers.

But wouldn't you have doppler shift - the sound is actually pointing in every direction, not modeled. It really is rotating outward about a common axis. You are catching the part about the speakers being grouped together pointing outward, right? The motion would be real - just accomplished a different way than with the magical mystical organically grown by elves electric motors - right?

Isn't a rotating baffle thing already available, or is the reflector idea something different?

[Hink]

It's simply sound panning - which is nothing like the beautiful Leslie chorus effect. There would be zero pitch bending, therefore zero chorusing. All you would have is a stepping volume attenuation, with stepping phase issues. If the goal is to have something like a home organ consol, it might be interesting - if disturbing. But if the goal is to then re-record it, and sound somewhat like a Leslie, it would be complete failure.

A better compromise might be to use the VST to apply the missing doppler shift, and send this to stationary speakers.

But wouldn't you have doppler shift - the sound is actually pointing in every direction, not modeled. It really is rotating outward about a common axis. You are catching the part about the speakers being grouped together pointing outward, right? The motion would be real - just accomplished a different way than with the magical mystical organically grown by elves electric motors - right?

Isn't a rotating baffle thing already available, or is the reflector idea something different?

a baffle deflects sound doesn't it?

[pj geerlings]

First draw a 5 cm diameter circle on a piece of paper - let the center of the circle be point "C". Draw a point somewhere outside the circle - call it "E". Put your pencil on a point somewhere on the circle - call that point "H". You can measure the distance from H to E with a ruler and it turns out it is not too hard to write an equation for the distance from E to any arbitrary point "H" on the circle based on the angle of HCE.

Now consider two fixed sound sources. The distance from these two sound sources to any arbitrary fixed point (like E above) is constant. No amount of panning between these two points will change the actual distance the sound has to travel.

A moving horn is exactly like the first example - there is a Doppler shift because the sound source moves. As the angle of the horn changes the distance from the Horn to the Ear actually changes. There is no Doppler shift in the second case because the sound source is static. There will be an interesting (even if more-or-less fixed) comb filter effect as the signal is panned between the two speakers - but absolutely no Doppler Shift.

What a Leslie Speaker does to an otherwise static sound is amazing! Most of it is multiple Doppler shifts as wall reflections are combined with direct signals - it's like a symphony. Add another Leslie and you have sonic heaven.

BTW, the reason there are multiple Doppler shifts going on is that the relationship of an arbitrary wall to the horn is different than the relationship of the listener's ear to horn. As the horn is moving towards the ear (and the pitch is moved slightly sharp) the horn is moving away from at least one wall (and this pitch is moved slightly flat) - the net result is that these two sounds (and every other possible reflection path) are combined into the magic that is Leslie.

peace,
pj

[Hink]

of course from within a leslie cab is also coming reflections as well that I'm sure lends charm to the true leslie sound as well...

[guitarzan]

Surely I did some confusion speaking about emulation, IRs and so on...

I would focus on the main part:

replace a rotating horn with four fixed loudspeakers. Each louspeaker pointing from the center to one 90° section. On a cross for 360°.
Then calculate vector projection to fade from only one loudspeaker to only the adjacent one.
I.e.:
speaker1: 0
speaker2: 0
speaker3: A sin(angle)
speaker4: A cos(angle)

where angle goes from 0° to 90° and so on

Nothing more than this. With the hypotesis that we can set good relative phases among speakers, shouldn't this be like a rotating horn?

Please don't get me wrong, consider that any criticism here is _more_ than welcome

From this point everything could be added: IRs, external case, original variations, etc...

Two loudspeakers are enough for emulation, but for this vectorial combination you need 4 orthogonal ones...

And yes... if ever this will seem like an interesting thing I'll build it

It's 4 speakers, clustered in an array around a common axis pointing outward - the physical distace from your ear would be changing, right??

[pj geerlings]

Surely I did some confusion speaking about emulation, IRs and so on...

I would focus on the main part:

replace a rotating horn with four fixed loudspeakers. Each louspeaker pointing from the center to one 90° section. On a cross for 360°.
Then calculate vector projection to fade from only one loudspeaker to only the adjacent one.
I.e.:
speaker1: 0
speaker2: 0
speaker3: A sin(angle)
speaker4: A cos(angle)

where angle goes from 0° to 90° and so on

Nothing more than this. With the hypotesis that we can set good relative phases among speakers, shouldn't this be like a rotating horn?

Please don't get me wrong, consider that any criticism here is _more_ than welcome

From this point everything could be added: IRs, external case, original variations, etc...

Two loudspeakers are enough for emulation, but for this vectorial combination you need 4 orthogonal ones...

And yes... if ever this will seem like an interesting thing I'll build it

It's 4 speakers, clustered in an array around a common axis pointing outward - the physical distace from your ear would be changing, right??

The difference in speaker location would contribute to the nature of the fixed comb filter (only). The speakers must move to achieve Doppler Shift or the software must vary the delay to simulate it.

[guitarzan]

Well all righty then!

[FR3Qz]

Oh Yes!!!
(Old Guy answer here bro...) I own a 1973 Leslie 90 - with the 12 inch original woofer,
still intake...(yes, I am the ORIGINAL OWNER!!)

If anything, Plllease, please be sure you can stick with the MONO version, and its
eq range is TOTALLY between 136K to 12k ... Ive checked it on a specktrum, and also
done a Phyco-acoustic analisis of it, for the range. the rotor otself, spins at approz.
255 rpm . So, If you delvelope this thing, and want TRUE spec'z or would like nice real
dry sample of it using either my tele or strats, Id be MORE then happy to Oblige!!

Just lemme know, Im excited.

Ive use the Centrifuge v1.0 which kik'z ass , but its NOT my Leslie cab. Its just NOT
there.....

Kick it in ass bo, I WANT THIS THING, Im very interested!!!

THX!!


FR3Qz!

[Kiwburger]

If you own a Leslie, then i'm very sure that you won't want this thing as proposed ...

PJ is totally correct. Without an actual moving speaker, you just won't get the good effect you want.

The Leslie uses a horn for the highs and a rotor for the lows. The horn is what you would expect it to look like. There are two, but one is only for balance. The rotor is basically a baffle. In both cases, the speaker is stationary, but the sound is directed into a moving circular path, more or less.

In both cases, when the sound is comming towards you, the velocity of the horn/rotor is added to the sound, which squeezes up the wavelenght, increases the frequency. As the sound is going away from you, the velocity is subtracted from the sound, so the wavelength is stretch, deceasing the frequency.

VST plugins do a very good job, in my opinion. A speaker switching arrangement would be nowhere near as interesting. The potential for glitches and for an obviousl 'stepped' sound could be a real problem too.

[michu]

quinto,
2 speakers should be more than enough to get this effect, 2 other would be projecting into the wall...
and if let's say you'd use like 10 impulses for rotating morph, then impulses would be like 36 degrees from each other, and no, crossfading between 2 filters won't give the same result as sweeping frequency of one filter between 2 values

[AdmiralQuality]

Just occurred to me, switching successively between a series of static phase shifts is exactly how scanner vibrato works.

Though the scanner vibrato has more than 4 taps (which equate to our speakers in this example) Still... it might do SOMETHING. Subtle I'd bet, but I'm thinking now it might actually do SOMETHING... Worth a test at least.

Another thing to try would be a crossover to isolate the "rotor" (highs) and "drum" (lows) signals and pan them out of the speakers at independent "angles" and "rotation" speeds.

Still, it's going to be VERY dependent on the acoustics of the room. Normally you don't want a lot of reflection but in this case, you'd probably hear very little effect at all without a hard wall behind your speakers.

[asseca]

One small advantage of a physical multi-speaker setup is that you get the directional acoustic filtering "free".

Most leslie sims still miss this filtering ...

Explanation:
The high frequency response will change slightly as the horn rotor rotates through 360 degrees. The horn will have the best high frequency response when pointed toward the listener, and will be the worst when the horn is pointing 180 degrees away from the listener ...

[michu]

Admiral Quality,
we are talkin about more than 4 taps here, Quinto has morphing convolution technology, the question is how many impulses it would take for convincing result...
another interesting trick that could be possible would be rotating cabinet besides rotating speaker

[C00kie]

... or swing a mic around in front of a static speaker, gives a simular effect.

You can swing your acoustic guitar, can't do that with a 250kg Hammond organ