Jump to content

through-zero doppler


Recommended Posts

  • Members

Originally posted by Walters9515

Do u want me to insult u becaues your asking for it?

 

 

You can't insult me since I never take this stuff personally. Were we in the same room together I highly doubt you would have the gumption to say such things to my face. So you see, you lose before you begin.

 

But if you wanna waste your typing on insults....all you have to do is open the door.

Link to comment
Share on other sites

  • Replies 172
  • Created
  • Last Reply
  • Members

Originally posted by Walters9515

Why do u have 7 leslies do they sound different? and Why do they sound different is it because they cabinet material shape,size,woods? Why did u change it to solid state power amp?

 

 

I said "I've owned several". Not seven. And 'owned' is past tense. I no longer own them.

 

One was a single rotor Leslie, installed in an L200 Hammond (from memory - i've owned several organs and sold or given them all away too). That small one sounded great. I think the bigger cabinets sound a bit crap.

 

The others were the big standalone horn and rotor cabinets. There was time in the 1990's where I would buy any Leslie because they were old and rare, and at the time nothing digital was good enough. They were usually faulty, or the amps were noisy, and I just prefered to remove the original amps and install 1/4" jacks direct to the speaker drivers. Then you could choose what amp to drive them, but I usually used a solid state stereo power amp.

 

I have lots of rotary speaker plugins, and my favorite isn't for sale but it's good enough for me to give away my last Leslie.

 

I don't care for the motor noise, or the speakers they used, or the cheap MDF cabinets, or the lousy styrofoam rotors.

 

I intend to build my own, smaller, rotary cabinet. I'll probably use quality plywood, and probably midi controlled stepper motors and quality guitar speakers (Celestion V30 or something). I'll probably use sheet aluminum for the rotor and horns, which should direct the sound a bit better than styrofoam.

 

As a temporary measure, you could probably get an old record turntable to drive a plastic bucket with a hole cut out of it, and mount that over your guitar cab.

 

I just don't like the noise and crap sound from typical Leslie speakers. I know the originals set the standard, but they don't sound modern anymore. I love old sounds, but you have to bring them into this Millenium somehow.

Link to comment
Share on other sites

  • Members

The big problem with most motors is gearing them down to the slow speeds needed for a rotary speaker. And you need a bit of torque to overcome air resistance.

I haven't tried it yet, but I think a stepper motor would have the torque to drive a rotor or baffle directly. That makes it easier - and i'm hoping it will be a lot quieter.

It should be possible to write a VST plugin that controls the stepper motor, and that means you can do cool stuff like having it synced up to host tempo, and have any speed you like, and any acceleration or deceleration you like.

With some nice speakers, I think it would sound better than any Leslie i've owned.

Link to comment
Share on other sites

  • Members

acceleration or deceleration depends on the R/C time constant Timer inside the leslie cabinet and motor
most motors just have 2 speeds like a transmisson in a car

synced up to host tempo

Its the same thing like CV voltages sync the midi box thats converters midi to CV the motor can be the CV voltages turned into midi you don't need a stepper motor

Link to comment
Share on other sites

  • Members

I'm not sure where you get this stuff from ..

Acceleration/deceleration in a real Leslie is simply natural intertia of the spinning hardware, controlled by brake tension as well. The motors are basically two seperate motors for fast and slow, and you just switch on the one that you want. No R/C timers involved. I just used a relay, and switched between fast or slow with an external switch and battery.

You're right that midi data could be turned into continously variable voltage (or 128 steps anyway), and that could be used to control a motor that doesn't have to be a stepper motor.

But my interest in stepper motors is their high starting torque, and no need for a reduction gearbox. Also, the synchronisation could be extremely accurate. Not just getting the speed synchronised, but the actual position. You could decide in your DAW exactly where the zero crossing would be - I think that would be extremely cool.

Switching polarity of the speaker or mic doesn't affect the dopper effect. Only switching the polarity of the motor would reverse the doppler effect.

To reverse the doppler effect, you would have to make the baffle come towards you when it normally would have been going away from you, and go away from you when it normally would have been coming towards you.

In other words - reverse the rotation. It's not rocket scientology.

Thinking about it - I put you wrong about switching the polarity of your software. Reversing Left & Right might be more like it, but the Doppler part of the model is the rising and falling in pitch.

Just playing the game.

Link to comment
Share on other sites

  • Members

"DAW exactly where the zero crossing would be - I think that would be extremely cool."


What u mean by zero crossing the leslie motor?



"No R/C timers involved. I just used a relay, and switched between fast or slow with an external switch and battery"


I was thinking about adding a R/C timer so when u switch from the slow motor to the fast motor the R/C timer is in the middle hooked up to the voltage line and will delay or ramp the voltage to give a slope.


"To reverse the doppler effect, you would have to make the baffle come towards you when it normally would have been going away from you, and go away from you when it normally would have been coming towards you."


The only way to do this is to mic the leslie in "Stereo" one mic on the left and the other on the right then Reversing Left & Right on the console or mixer or DAW so the Left mic is on the right channel and the Right mic is on the Left channel

I don't think reversing the motor direction would do anything
but maybe a subtle difference

Link to comment
Share on other sites

  • Members

Originally posted by Walters9515

Reversing the direction of the motor is not going to give you "Negative doppler time"


TZF= negative delay time,Zero point, positive delay time


Doppler TZF= negative doppler , Zero point, Positive doppler time


Zero point is when the motor is in the middle and have "Braked or stop"

 

 

Now to me (as an organist) this makes sense. You do not get negative doppler (or Leslie) effect by reversing the motors.

 

Zero point is indeed where the Leslie rotors are either 'braked' or stopped. Unfortunately there is no way to guarantee exactly where the rotors will stop every time.

 

Now granted, I still don't know what it is that walters is asking for - but this part of this thread actually makes sense.

 

FWIW, most organists agree that Leslies have their particular sound because the top rotor spins counter-clockwise, and the bottom spins clockwise. If you change either of those, it no longer sounds like a Leslie. There are other factors involved, of course.

Link to comment
Share on other sites

  • Members
Originally posted by Kiwiburger

I just don't like the noise and crap sound from typical Leslie speakers. I know the originals set the standard, but they don't sound modern anymore. I love old sounds, but you have to bring them into this Millenium somehow.



I have to go home and lie down.

A Hammond/Leslie combination sounding "modern"?

NOOOOOOOOOOOOOOOOOOOOOOOO..........! :freak: :freak:

Link to comment
Share on other sites

  • Members

Happy Christmas Dougb. I can't agree with you - you seem to be displaying Walters logic.

At what point did I say that a Hammond/Leslie combination sounded modern? We have been talking about Leslies, or rotary speakers in general. Not Hammond organs - that's your own personal mindset showing.

I don't know how I could have expressed this clearer. I stated directly that a conventional Leslie doesn't sound modern - which is why I am considering building a better rotary speaker device with a stepper motor and DAW control via midi. Does that sound like anything that exists yet?

And although I love Hammond organs - I have sold all mine. Rotary speakers are useful for guitars and vocals and all sorts of other applications that haven't been tried yet.

And your understanding of the Doppler effect (a small component of the Leslie sound) is just as as flawed as Walters.

The Doppler effect is a pitch shift - up or down, caused by the addition of velocity to an acoustic waveform. The only way to "reverse" a doppler effect is to reverse the direction of the applied velocity. In a rotary speaker, that means reversing the direction.

I was simply answering to the faulty logic that suggested you need time travel of something similar to achieved a "reversal" of the doppler effect.

Logically - what is the reverse of a drop in pitch? Obviously an increase in pitch. No time travel needed - just reverse the doppler effect by reversing the direction.

The confusing thing is that rotary speakers are not just a doppler effect. And the doppler componant is alternating - so most people won't hear the difference if the motors are reversed.

This is a typical Walters question - calculated to confuse intelligent people. Whether that implies Walters is extremely clever, or extremley simple, is wide open to debate.

Link to comment
Share on other sites

  • Moderators

When the rotor is moving toward you, the apparent pitch increases. When it's moving away from you, the apparent pitch drops. At the tiny instant when the functioning half of the rotor is pointing at you there is zero Doppler shift.

Am I wrong about this? :confused:

Terry D.

Link to comment
Share on other sites

  • Members
Originally posted by MrKnobs

When the rotor is moving toward you, the apparent pitch increases. When it's moving away from you, the apparent pitch drops. At the tiny instant when the functioning half of the rotor is pointing at you there is zero Doppler shift.


Am I wrong about this?
:confused:

Terry D.



Nope -- I mean nope you're not wrong about that (or at the tiny interest when the horn is pointed away from you)

but as you mention it's a tiny instant...really a point...infinitely small in pure math terms (but in physical terms we've got "enriching factors" such as room reflections, the sine nature of circular motion makes the doppler shift low "around" that point, etc)

I think Walters has just started reading about delay applications (maybe craig's old handbook -- "doppler" was used in terms of modulated delays seemed common during that era) as he was asking about multitap delays too

Walters -- it's a bigger deal with flanging
1) b/c the flange is created with a delay mechanism (either a recording of a delay device)
2) there is interaction between 2 signals

Link to comment
Share on other sites

  • Members

I must admit it's a little disappointing, Walters is obviously looking at delay processing in general and flanging particularly (as shown by his flanging post in the FX forum) so I do find his question ingenuine...worse, "the act" is inconsistent...it's poor performance art and, like bad slight-of-hand the illusion is broken b/c the performer isn't watching his angles

too bad, the convo coud be good -- in fact, the discussion among the other contributors is good!

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.




×
×
  • Create New...