DIYstompboxes.com

I was sure I posted this the other day, and again today, but I can't seem to find a trace of it here, so here goes again.

I'm about to acquire a small Leslie speaker from a local guy (actually RE-acquire; I had one just like it but sold it in 1980 and I really miss it), and it got me to thinking about simulating rotating speakers.

Authentic simulations require one to consider the quirks of the device being simulated and going beyond merely the first thing you can find that sounds sort of like it.  In the case of Leslie speakers, our attention is drawn most to the notches created by the Doppler effect and to the cyclical nature of it.  So, some folks found an effective simulation in LFO powered bandpass filters (the PAiA Synthespin), then phasers (P90), and finally flangers near the upper end of their delay range.

The thing of it is, though, that although a spinning spekaer or speaker baffle produces swirly notches, that's not ALL it does.  As it points away from you, it also produces a slight modulation of both timbre (less treble when not facing you) and amplitude (louder when pointed at you).  So, what I'm thinking of is whether any of the existing rotating speaker sims factor in the "throb" of a real rotating speaker.

In principle, one could easily whip up a "throb simulator" module that could tack on to a basic design the way that RG Keen's LERA (at www.geofex.com) mimics the ramp-up/down time of rotor motors.  A couple of optoisolators could easily be used to gently modulate level and treble cut, and the LED half of the optoisolator can be yoked to the on-board LFO.  The nice thing is that since the notches themselves are generated internal to the flanger, the throb generator can be tacked onto the output without having to monkey around too much on the internals.

The thing I am having a difficult time wrapping my head around is the relationship of LFO polarity to throb. What *should* happen is that at the same time:
- the volume takes a little dip
- the treble is rolled back a bit
- the delay time is at maximum in its sweep (not maximum delay possible from the device)

Bear in mind that both treble trimming and notches will already create the impression of slightly reduced amplitude, so whatever amplitude modulation is imposed on top of that will have to be subtle.  Still, my guess is that you'd need to top off what the treble trim and notches do with a modest volume reduction.

Make sense?

Incidentally, it is the moving notch and treble trim that make the phasefilter mod on phasers so interesting.  I've only ever heard it on 4-stagers, and since I know from Mike Irwin's demonstrations that 12-stage phasers sound a lot more flanger-like, I'm wondering whether a 12-stager with the last 2 stages converted to lowpass (5 notches and a 2-pole lowpass filter) might do a passable Leslie simulation.

My low-rent approach to this is to use both phase and tremelo, *synced* by ear (or eye). I use a DOD 201 and Fulltone Supa-Trem. The Fulltone has a flashing rate LED and I added this feature to my DOD 201. The throb added by the trem makes for a nice effect. The other thing to keep in mind is that, as far as I know, Leslie cabs don't have very much high frequency response. I usually roll off a bit of treble.

Kerry M

Hi Mark,

I think that i must not tell you something about the Rolls RFX-147

Munky has the schematics for Dynacord CLS-222

http://www.geocities.com/munkydiy/schematics.html

and here you can find the Korg CX-3 Leslie part

http://home.germany.net/100-235778/richy2001/circuit/s3.gif

If you have problems with specific values I have an original copy and i can tell you from that. Maybe this gives you some inspiration.
I think its not necessary to explain to you the function of the Korg CX-3, but if you have any questions feel free to ask

analogguru@hotmail.com

Funny you should post this Mark as I was working on something similar a few weeks ago (still am, but I’m taking a breather - read I’m sick of the sight of it!).  From what I’ve read the Leslie's throb is frequency dependant, i.e. lower notes receive the lion’s share of amplitude modulation.  Conversely, the doppler  effect is more prominent at the higher end of things.  

So far I’ve got pretty reasonable results following a phase-splitter vibrato input stage with a frequency selective tremolo.  I used a p-channel MOSFET inserted between the input resistor and -ve input of a inverting op-amp set up for just above unity gain.  The MOSFET’s source connects to the inverting input and the drain to the input resistor.  There’s DC bias on the FET so that the channel is fully conducting and the LFO pulls down on the gate thus attenuating the signal.  By placing a cap from drain to source, amplitude modulation is frequency selective with the lower notes getting the full throb.  I use a 5V regulator for the op-amp and MOSFET bias so that the circuit remains unaffected by supply variations.

The whole effect is quite subtle and definitely gives a more Leslie type vibe (pun shamefully intended) to things.

Thanks for the feedback and links, guys.

I guess it is worth noting that mimicking a Leslie is not one single thing.  Though the sound of a rotating speaker is clearly distinctive, there is more than one rotating speaker design.  More specifically, there are single and multi-rotor versions.  The one I'm about to acquire is a single rotor version with just one measly 8" speaker and a styrofoam "cheese-wheel" rotating baffle.

Of course, whether you have a single full bandwidth rotor or band-splitting  or multiple rotors, the fact of the matter is that low frequencies, by their nature are less directional, and unless one had some means of using a flawlessly sealed cabinet that restricted audible speaker output to ONLY what came out of the rotor/baffle, chances are that it IS, as noted, mostly the mids and highs being thrown around the room while the lows are more or less omnipresent and omnidirectional, like a subwoofer signal.  So, because the lows aren't efficiently being thrown around by a rotor, there is less doppler-related cancellation in that part of the spectrum.  Indeed it may be the shifting phase/time relationship between fundamentals and harmonics that makes rotating speakers sound as interesting as they do to our ears.  It's "semi-patterns" that draw our attention (read Bernie Hutchins article on "fat sounds" in JAES, 1981 for a further articulation).

Of course, what this suggests is that some sort of gentle frequency-shaping of the "straight" signal might make flangers or chorusses more interesting.  One idea that springs to mind is a simple shallow lowpass/highpass network, not unlike the famous BMP tone control.  The highpass gets mixed in with the time-delayed signal at one mixing stage, and then all of that gets mixed in with the lowpass signal at a second mixing stage.

I will have to look at the Rolls circuit again, and spend a couple of hours with the Dynacord one as well.

Mark,
When you study the Rolls circut,  I think it's a lesson in "How to Not do it".
As that box was a "miss" not a "hit".
Which bothers me a little,  because it's one of the few Leslie Sim  circuts I can understand.
Ed R.

Well, you're right about the Rolls unit being easy to follow.  I took a brief peek at it and was just about to post some comments, when I saw your note.

Unlike the Korg and Dynacord units linked to at Munky's site, the Rolls does not employ separate time-delay for the low end.  Rather, it uses what amounts to a 2-stage Small Stone circuit (2-stage OTA-based allpass) to modulate the bass.  Of course time and phase are related but not the same thing, and the same absolute time difference results in a much greater phase difference the higher up you go in frequency.

Other than simply not "nailing" it, what is it about the Rolls you don't like?  I'd be curious for opinions on analog simulators that DO nail it well.

I have heard good reports about the H&K tube unit. I think Steve Aloha has some sound clips of it. But I'm not real familiar with these things.

Doug

Boy I hate the "Invalid session" thing!!!!
Type for 20 minutes and it's gone!
What a waste of time- I gotta go cool off.

Aron- If you see this message- see if you can do something about that problem........

Ed R.

I copy the text i just wrote before submitting anything. Keeps my blood preasure at normal levels ;)

Quote from: Ed RemboldBoy I hate the "Invalid session" thing!!!!
Type for 20 minutes and it's gone!
What a waste of time- I gotta go cool off.

Aron- If you see this message- see if you can do something about that problem........

Ed R.

Unfortunately there isn't much Aron can do about that one. It's an inherent problem with the phpBB design. If you run your own server, you can adjust a value that helps out greatly, but running on a commercial host leaves you out in the cold. :(

There is a work-around :), OK actually two of them.

(1) The easiest way is to make your reply in a word processor, and then paste it into the post box. Don't open the posting form until you are really ready to paste.

(2) Every 5 minutes or so, press the preview button. That will refresh the session.

I know it's a pain, but eliminating it from the system would take some major work unfortunately.

Take care,
-Peter

I think a major problem with trying to recreate a 'rotating speaker' sound is that when one is actually in front of a rotating speaer, the sound reaching each ear is coing from a slightly different path. So I would be thining that you really need to make TWO circuits. As a test, see whether you are happy listening to a recording of a leslie in mono, as opposed to stereo.

I wonder what methods do those programmers of soft synths/virtual instruments and VST plugins use in some "Leslie" or whatever rotary simulations...some of them sound very convinsing...maybe you could turn them back to analog...you could call it analog copy of digital copy of analog.

I just fixed my self-made mixer in working order (with duct tape), I have left-right difference amp in it, maybe I should listen what the stereo part of the rotary sim sounds have in it, when the juice is extracted...

I agree Paul.  The compression from that OC20 rectifier, and the boxy acoustical properties of that wretched old cabinet, and listening right in front of it, gave you that sweet quality.  When you get all of those things down, then you have a leslie sim!!! I miss my old 145. I was the only guitar player in NW Ohio that would haul one around to gigs!  The first gig I used it, my bandmates were scratching their heads.  They thought putting a plant on it for decoration was a good idea, until I played "It Don't Come Easy", then they changed their tune. :)  

Ahh..  the memories. :cry:

There's plenty of stuff out there on the Leslie, but here's a nice overview - should get some of you scratching your heads!

http://theatreorgans.com/hammond/faq/mystery/mystery.html

Oh, and then there's that oil hole!!! Gotta be apart of the sound!!!  :lol:  :lol:  :lol:  sorry... :mrgreen:

Quote from: DavefxOh, and then there's that oil hole!!! Gotta be apart of the sound!!!  :lol:  :lol:  :lol:  sorry... :mrgreen:

No, the oil hole doesn't affect the sound.  The oil you put in it mind...well, that's another story!

Maybe you want to build the real thing:

http://mad.topnet.com.au/~hairbear/page.2e.htm

a friend of mine has an Allsound-Leslie (German) with independent Bass- and Treble-Rotor for sale, i don´t know the price yet, if there is interest, i can ask him.

analogguru@hotmail.com

another one:

http://mad.topnet.com.au/~hairbear/page.2f.htm

analogguru

Well I have an H&K Tube rotosphere and I think it sounds almost dead on for Leslie.  There are lots of stressfull things to think of with a real one.  Micing that muther ain't fun.  Read an article once where Gilmour said they 7 mics on a Leslie and dialed in the perfect sound on the mixer.  Just get the H&K!  No it is designed to try and sound like a leslie not a univibe or a glorified chorus phaser pedal.  Hint though, I tried 7 of them and picked the best from the 7.  That is truly the best way to shope for new pedals.  Just hit your local GC or other large retailer and line up all of their stock and give them a go until you find that magic one.  It sounds dead on for that "Badge" sound and damn damn close for "Something in the Way"  I will say it seems to like single coils for tone.

I have a software leslie simulator on my PC, so I did some quick listening tests what it does. I fed it with basic organ tone that had no vibrato or any modulation or delay or reverb in it, but some harmonic content so I could hear the effect of each parameter adjustment of building blocks. I suppose what makes it tick or sound as it sounds could be done with hardware. However we are talking about very complex design with many building blocks.

My quick guess what could be the building blocks of this software leslie emulator:

- cross-over filter for divide signal to low and hi rotors
- "tube-sound" overdrive/distortion (maybe two channels?)
- separate amplitude and freq modulators for Hi horn
- amplitude modulator for Lo horn
- phase shifter (maybe you could adjust it near like chorus and flanger too)
- LFO s for all those, with pre-set speeds and some of them might need be in sync together, and those start/stop speeding/slowing up sims
- some magig circuit that simulates angle and distance of the mic that is used to pick up the sound
- somewhat complex mixing system to mix this together, and in stereo

"Tube-sound" overdrive/distortion does not need explanation, but not just any distortion works in this situation. Maybe pre- and post eq requirements are different than guitar pedal ones. There is more complex processing in Hi Rotor channel, of course. Amplitude and freq modulation sounded sinusoidal, and if you adjust anything "too much" it does not sound "natural". In its own, any element was not so special, but with right mixing level and adjustment of each parameter it did sound much like rome recordings made with "real thing".


Here is some list about this software sim controls (Steinberg Rotary, made by mda?)

6 rotary pots, value range from 0 to 720, propably adjusts the speed of rotary horns, or are pre-sets for fast/slow settings when controlled with midi? Must check, named like this:

Hi Slow
Hi Rate
Hi Fast
Lo Slow
Lo Rate
Lo Fast


9 slider controls:

Overdrive
Crossover freq
Mic Angle
Mic Distance
Low Rotor Amp. Mod.
Low Rotor Mix Level
Hi Rotor Amp. Mod.
Hi Rotor Freq. Mod.
Phasing

Mix and Gain level

Some presets named this:

147 slow
147 fast
147 stop
slow flanger
analog chorus
dirty les
horn mic

Sounds like you guys are trying to come up with the pedal I have been searching for ever since I had to sell my huge Yamaha amp (combo higher than a half stack and about twice as deep!) with TWO build in rotating speakers ! :cry:

Even if it is kept down to earth as in Marks post (volume- and treble-dip and a touch of doppler-delay) it's there. Surely these three effects can be synchronized ?

I agree with Paul on his point on stereo. But if we can make a tremolo go ping-pong-pan, I believe this can work as well.

I'll be folowing this thread closely, this is THE effect I've been waiting for !

Some interesting and provocative contributions here, and I'm pleased to see the accumulation of info as the thread progresses.

Rotating speakers are probably the only "natural" post-production effect that exists for guitar.  I'd describe it as "post-production" because it is mapped onto the guitar signal after it has gone through the entire signal chain: the effects, the preamp, power-amp, output transformer, and speakers.  As such, it processes all of the various characteristics accumulated along the way, including the assorted forms of distortion imparted by each of those components.  The typical forms of Leslie simulation are inserted en route, although I imagine that outside of the gigging context, plenty of folks do attempt to mimic "Leslification" of an existing mic'd amp.  What that means is that, for most guitarists in most instances, stompboxes or modelling devices will tend not to live up to their experience of using a true end-of-chain rotating speaker.

As is appropriately noted, the spatial aspect of rotating speakers is an instrinsic aspect of their attraction.  Other than the time the nurses gave me Atavan when my kidney-stone attacks were making me a little too unruly for their liking, I think the closest I have ever come to a true drug experience was playing a gig where I was centred between a Leslie and another separate amp set to a slow tremolo.  In that context I think I would have been unable to remember the lyrics to Speed Racer or that supermarionation nugget "Stingray"!

Still, despite the obvious pleasure of a live 360-degree Leslie experience, listen to "Badge" or any comparable tune through the 3" speaker of the cheesiest $9.95 mono clock-radio and it is clearly different than a flanger, chorus, or any number of other attempts to fake it.  For me, what all of this means is that although there is added value in the spatial aspect (and that deserves its own software solution for emulation purposes) it is superimposed upon some very basic aspects that exist in mono or any non-mono format.  And that is more or less what I'm trying to nail.  The ramp-up transition-time, as noted, is one of the aspects that needs attending to, but so does the modulation of bandwidth and amplitude.  

Think of it this way: if you had 20 mics spread equidistantly around the path of the spinning speaker you wouldn't actually *hear* any cancellations and probably wouldn't get any rotating speaker effect at all.  Ergo, part of the *heard* effect comes from being off-axis as listener, and it is those off-axis aspects that I think are the missing link between flangers, et al, and more authentic rotating speaker emulation.

I don't understand most of what you guys are talking about, but by the time you get it all figured out, I hope to.  8)   I would love to build a pedal like this! Of course, whoever does get it right, could probably go into production with it.

i am tired now. but i think with enough **GREEN SMOKE** we could get anything spinning..   lol... sleep deprivation

prayer for the sleep deprived

now i drag my weary ass out of bed,
althogh it feels as if i'm dead
doing fine alas its sh*tty,

thought i had a heartattack
but stepped on my titty

It's easy to 'overmystify' the Leslie experience. Fundamentally, what we have is a number of speaker-t-listner audio paths, that are changing in length periodically. Which path variations are causing phasing & level & frequency fluctuations.

Quote from: BluesgeetarWell I have an H&K Tube rotosphere and I think it sounds almost dead on for Leslie.  There are lots of stressfull things to think of with a real one.  Micing that muther ain't fun.  Read an article once where Gilmour said they 7 mics on a Leslie and dialed in the perfect sound on the mixer.  Just get the H&K!  No it is designed to try and sound like a leslie not a univibe or a glorified chorus phaser pedal.

The Rotosphere!?! Keep in mind that this is my opinion but I think that its a horrible sounding simulator. Yeah its not a univibe but mind you most univibe clones aren't not trying to sell themselves off as lesilie simulators anymore but as univibes. It sounds like and is in fact a glorified chrous pedal. I have several other complaints about it but I'll leave it at that.

Once again this is just my opinion. If the thing works for you then more power to ya. :)

I do think there are some spatial effects that come from a lesile that are nearly impossible to recreate in a flat mono enviroment. I have done some playing around with interesting results but the physical aspect can almost never be duplicated.

If you want to a get a leslie sound you can hang an amp from the ceiling using rope and just spin the thing. I did. hehehe

Andrew

What about the Option 5 Destination Rotation pedal? Many claim this is THE pedal that comes closest to the leslie>>>

http://www.option5-online.com/option5.html

I've got a Leslie 22H and as far as my jaded opinion goes.... any pedal simulation is like cheap hamburger comparred to filet mignon.

-Peter

Tone God, If you would have read my entire post with comprehension you would have seen that I recommended he try a whole slew of Rotospheres if at all possible.  I did and me and many other pro players around Seattle agree the little pedal has got some magic.  But I did not come by this by just taking the first one they threw in front of me.  Mass produced pedals as I have seen stated here many many times all sound different from pedal to pedal.  I have heard vintage FF anf TB that sounded like crap and others that sounded like a dream even though they looked to be the same circuit and tranny types.  Most importantly, what your ear hears is not what you will get in the recording.  A nice real leslie is great but your only allowed so much room for the leslie in the mix.  So unless your gonna just make recordings of just a leslie being played or are just hearing it for your own personal pleasure I still recommend trying a slew of rotospheres until you find the right one.  Everyone I know with a decent ear likes my sound.  I also am not a shallow guitarist in the fact that I love to tweak knobs.  If you plug a guitar into a real leslie you will get instant gratification.  If you want to do it the the pedal way you will have to do some tweaking and trying out different amps, pickups and preamps and so on.  I don't mind doing it that way but most guitarists can't stand to turn a knob and actually tweak and craft a sound out of equipment, they want instant rock stardom with no work.  So again I recommend go to GC and try as many Tube Rotospheres as possible and then go to another GC and do the same until you find that perfect one.   I'm sure all the famous players that use the H&K TR don't just take the first one.  They do just like Eric and send out a tech to try as many Fuzz Faces or whatever as possible and buy the best sounding one. :D

Pete Snowberg said: "I've got a Leslie 22H and as far as my jaded opinion goes.... any pedal simulation is like cheap hamburger comparred to filet mignon."

That's my traditional view as well, but the fact of the matter is that the first step to effective simulation is a more thorough description.  If one follows the history of recorded sound, improvements in sound quality have stemmed largely from people comparing real in-person sound against better and worse approximations and conceptualizing what the gaps were, then translating that into technical parameters that could be explored and manipulated.  People would be startled by the advances, but after a while would come to the conclusion that there was still something "missing", and in identifying more of what was missing move another step, then another, then another.

In the case of rotating speakers, there are a number of different aspects to the "real deal" (some of which are specific to certain categories of models, and others of which are generic to all such devices).  Over the course of pedal history, attempts at simulation have tried to encompass some but not all of them.  And certainly, when you try and stuff it all in a little box and bring it in at a reasonable price-point, more aspects are bound to receive short shrift.  Nasse's posting makes it fairly evident the large number of factors/parameters one might be obliged to play with to mimic a rotating speaker, even his listing (courtesy of Steinberg) may well be insufficient.

I guess what prompted this thread was the desire to move beyond a simple tweaked flanger (which is of course what the overwhelming majority of guitar players would use to inexpensively fake that which they cannot own or lug around) to something that wasn't several orders of magnitude more complex or costly, but a few solid steps closer.

It is worth pointing out that, unlike something "easy" like an amp simulation, such a simulation has to reproduce the characteristics of accelerating motors and physical positioning.  That's a bit more complex than a steady state electronic device, and as such I'm more patient than impatient with respect to what can be done through either hardware emulation of DSP/software approaches.

If I may be so bold as to use a sexist metaphor: it's a bit like the difference between a CG depiction of a "hot-looking" or beautiful woman, and an engaging one.  Mimicking the interactive aspects is a whole lot more difficult to render than simply drawing a more detailed cartoon picture with skin-mapping.  Rotating speakers are more like the latter, and amp sims are more like the former.

Elabortating on the filet mignon to burgers, let me say this, i'd rather carry a burger to a sleazy club than the salmon, its just easier to carry and keep intact...The option five costs more than some leslies, my friend got one for 150, its a matter of convenience

My 2 cents: Leslie sim sounds are worth pursuing. I LOVE the fact that guys like Mark Hammer are at the problem.   I can't think of a tastier effect.  It's what got me interested in diy.  Since then, I've done what bluesgeetar did and got a RotosphereII (actually my wife got it for me - no she doesn't have any single sisters).  Now I'm building  all kinds of OD/dist tone toasters instead.  How's this for a slightly OT thread: favorite Leslie song (guitar).  Candidates : Badge, Presence of the Lord, Let It Be ?

I have 2 leslie cabs, I know of some pedals that can give a version of the leslie tone, but non that compare's equally, a Magnatone M-20 with both cab's spread about 12 ft. apart and the amp set on vibrato which is done with varistor's and the Fender style tremelo set at a slow throb can be very breathtaking the first time if you have never heard one, most people do not know that on the M-15 A and the M-20 Stereo they came stock with both, vibrato and tremelo, my M15 A has both.
the Fender Vibra sonic is another style, it has it's own way of making a different sound but simular to a leslie.
I am very excited to read this thread, I have a project I'm working on now that involves a Peavey Mace, VT serie's amp, it's 150 watt 6 X 6L6 power amp with a J-fet preamp, there are 18  8 holed socket's on this thing, 3 or 4 of these have house #'s on them, a few are 4558's, the rest or TL072 dual J-fet's, the part I found very interesting about this Amp beside's being an ungodly Big Mutha, is, it has built in phase that had me thinking about a foot controller for the speed and depth, which, if some good mod's were incorperated into the circuit, maybe you could get a simular type sound that would sub for a leslie in a live situation, i know it would probably fall short of this sound but it is a nice dream at this moment, if you would like to give me some input on this I would be very grateful, the schematic to the preamp can be found at this link.
JD                                    http://members.tripod.com/NatCade/pages/peavey.html

hi there JD: do you happen to know, which is the principle in the Fender Vibrasonic`s modulation? (I do know the Magnatone-thing...)

Puretube, Can you say Optoisalator, LOL ! all the Silver Face amps had this Topoligy, the version that sounds best to my ear's is the tweed vibralux cicuit, probably 1958'ish, this circuit is totally different topoligy, but when adjusted properly can sound very good.
JD

I wondered more if it does pure amplitude modulation, or if there is a phase-variation implied, or a timbre/volume modulation?

I think you mean this schem here:
http://www1.korksoft.com/~schem/fenderamps/bandmaster_6g7_schem.pdf

Puretube, I'm no engineer so don't get me to fantasizing, I'd only Fibb to ya, but these are simple, Yes, No and Yes, theory on these subjects though I will leave to Guy's like Peter, Aron, RG., Both Doug's, these are the guy's that can give you answers to engineering, I'm a doer, not a designer, LOL !
JD

:) if Constantin`s schem is that of a "vibrasonic" (?), it`s all I wanted to know...

Has anyone ever used or done a mod of  the DOD Vibrothang? For a cheapo pedal it does the Leslie thang fairly well. The biggest problem I have with it is the loss of my high end frequencies.

Quote from: quainttwangHas anyone ever used or done a mod of  the DOD Vibrothang? For a cheapo pedal it does the Leslie thang fairly well. The biggest problem I have with it is the loss of my high end frequencies.

From my limited experience, actual Leslie cabs are not known for extended high-frequency response, so this would be *realistic*. I've heard keyboard players complain about too much top end from Leslie sims.

Kerry M

I hear ya bwanasonic. I really like the pedal, but it sucks all the "tone" out of my little Blues Jr. (most noticeably the highs). I've searched the forums and haven't been able to come up with much. What I need is an "Unreal Realistic Vibrothang Tone Mojo Mod".