Hughes & Kettner Rotosphere

[axg20202]

Is it just me or do people simply choose to ignore that the rotating speaker cabinet was NOT developed under the presumption that it would be moved on a regular basis.  That's why they weigh so much.

Indeed. I guess Leslies were designed to be installed in churches and pretty much left alone other than perhaps moving it around on castors. Also, as an owner of a 147 Leslie myself, there's a lot of energy in those rotors when the Leslie is switched from Chorale to Tremolo. With no mass in the cab it would be moving all over the place! The 2 drivers, tube amp chassis and 2 motors add a lot of weight before you even factor in the bulky cabinet. I prefer the larger (taller) cabinets like the 147 because they have a better bass response than the shorter equivalent model, the 145, and don't care about the size and weight. Basically, if you want THE sound there is no substitute for the real thing....you just have to live with the size and weight, record with it (recording a Leslie is great fun!) and only gig it if you really have to and/or have a roadie...
I haven't really liked any of the Leslie stompbox effects, but then I've been spoiled by having the real thing - it is very difficult to model a truly 3-dimensional sound like a Leslie with fewer dimensions!

[Fredenando]

Here are some specification data over some real Leslies:

[Mark Hammer]

And that's why people have roadies.

[Taylor]

Well, 162 ain't so bad (unless that's kilos!  ) compared to lifting a B3. 

Or even any bass cabinet made before 2000. You guitarists have it easy.

[MR COFFEE]

For those who care to look into the CLS-222, you'll find it not only uses delay lines (aka Chorus-type circuits) for the upper and lower bands, but also varying lowpass filters to model the tonal change as the speakers rotate. And there are two LFOs that model the treble roto-horn and bass rotor speed changes with different speed up and slow-down ramps which are pretty well set to mimic the real deal. There is also a switch that allows a few different mixes of the emulated rotor outputs into two stereo outputs which actually does a really good job of making your ears think you are listening to a real rotating speaker. Doesn't appear to be present in the Rotosphere from what I see in this thread.  The CLS-222 sold for around $600 in their day iirc and were pretty full rack-mounted boxes. A *big* PCB.

No moving parts, so if the Rotosphere is a nearly exact copy, the reliability issue is either related to build quality and/or simply the fact it is a pretty darn complex circuit so there is more to go wrong. I figure a DSP version could probably be done in a SPIN chip or two, although it might be worth the additional complexity of doing some of the speed-up and slow-down of the LFOs in analog because I think the modeling of that is pretty important to get that Leslie sound, especially when it is slowing down. FWIW.

Might make a good DIY project if somebody worked it out and did a PCB. 

[DougH]

IIRC, one of the things I thought was cool about the CLS-222 (from a schematic perspective) was the use of a quadrature LFO for doing the stereo. But I could be wrong, might have been something else I was looking at but I thought it was the 222.

[Mark Hammer]

The rolls unit is also thoughtfully designed:  http://hammer.ampage.org/files/RFX147.gif

Whether it sounds great, I can't say.  Never heard one.

[Fredenando]

Cool Mark, here are an original manual, including a better scheme:

http://www.rolls.com/pdf/M_RFX147.pdf

[MR COFFEE]

Mark,
Thanks for pointing out the Rolls schematic. Looks like it uses only one BBD, though. Probably sounds better than the old standby Rotovibe everybody still raves over because Jimi had one back in the 70's.

Doug,
You're right - the Dynacord used two VCAs in each control oscillator (one oscillator for each "rotor" simulation), and the design took two different outputs from each oscillator in order to model more accurately the more complex phase relationships between delay time variation(for pitch change) and lowpass filtering and left-to-right panning changes (for spatial perception of movement within the room) of the emulated "rotor" signals just like the real deal. And two separate speed-up and slow-down circuits for each "rotor". There are simple mods floating around that make the high speed to low-speed transition faster for an even more realistic emulation of the mechanical cabinet behavior.

I haven't heard a leslie sim that comes close since. 'Course it cost $600 in 1980 dollars. And honestly, I don't hang out in music stores up and down the east coast anymore either.

I *am* surprised somebody hasn't done a DSP implementation of the algorithm implemented in analog circuitry in the CLS-222 and just blown the analog competition away.

I think prr is right on target in supposing a really good DSP implementation is within reach.

I really think the SPIN chips could model it economically and very realistically with a really good programmer. It might take 2 of 'em, but a little analog support and it could probably be done on one chip. At <$10 each, add in a little analog support circuitry and there you have it. No 20 analog building blocks on a PCB the size of Brooklyn. Sounds feasible to me.

Wish Keith Barr would show us how it's done <grin>

How many people here would jump at the chance to buy a two-rotor leslie sim stompbox for < $160?   

[12Bass]

Tech21 is coming out with a new emulator called RotoChoir. There's a picture in this TalkBass thread.  Oddly, it doesn't have stereo output.

http://www.talkbass.com/forum/showthread.php?t=728032

[Mark Hammer]

Interesting.....in a number of different ways.

It uses a wood-grain graphic, which mimics the wood-grain graphic on the Roto-Machine.  No big whoop, or copyright infringement, but just an....observation.

It also overcomes one of the things I find a limitation of the Roto-Machine.  As I've noted here on several occasions, the inability to adjust the output level of the RM, when the drive control is in different settings, is frustrating.  Tech21 has seen fit to include a level knob.

[12Bass]

Interesting.....in a number of different ways.

It uses a wood-grain graphic, which mimics the wood-grain graphic on the Roto-Machine.  No big whoop, or copyright infringement, but just an....observation.

Frankly, I'm a bit worried about their wood selection.  That particular piece has pretty nasty knot in it.   

Tech21 seems to have a thing for analog circuits (and shuns digital), so it will be interesting to find out what's inside (a couple BBDs?).  The form factor is shared with their recent Character series pedals.   

[12Bass]

RotoChoir demo.

http://www.youtube.com/watch?v=kiKMjrm9Ld4

[MR COFFEE]

Maybe it's my laptop speakers, but I don't hear any dual rotor sounds. If you've heard the CLS-222, you'd know it's the gold standard for simulating a real dual rotor leslie cab. Sounds better through a PA than the real deal miked up on a stage IMHO.

The "position" control reminds me of lesson 101 for leslie miking, don't stick a mike right up to the louvers <grin>

[DougH]

RotoChoir demo.

http://www.youtube.com/watch?v=kiKMjrm9Ld4

The distortion sounded cheesy and that made the rotating "phasing" effect sound cheesy IMO. Nice brake function but you have to give up the fast speed to get it. Some of the "biamp" stuff reminded me of the MFOS auto-panner. The auto-panner does the stereo pan with high and lo speeds and logarithmic spin up/down. (Incidentally, that might make a good starting point for a diy leslie effect too.)

[Earthscum]

...Oddly, it doesn't have stereo output.

In the demo, it is stereo... maybe single stereo jack on the output.

[12Bass]

Maybe it's my laptop speakers, but I don't hear any dual rotor sounds. If you've heard the CLS-222, you'd know it's the gold standard for simulating a real dual rotor leslie cab. Sounds better through a PA than the real deal miked up on a stage IMHO.

The "position" control reminds me of lesson 101 for leslie miking, don't stick a mike right up to the louvers <grin>

Didn't have sound when I found the link.  Now that I've listened, I'm hearing what sounds like a mix of flange and chorus.  Perhaps not the most accurate emulation.  Must be using a stereo output jack.

The Ventilator sounds better, IMO: http://www.youtube.com/watch?v=rrtjcHtY8MQ

[12Bass]

Related thread with schematics for MKI: http://freestompboxes.org/viewtopic.php?f=1&t=11817

[MR COFFEE]

Hey 12bass,

The link got truncated. Wanna try again?

Thanks

[Fredenando]

Hey 12bass,

The link got truncated. Wanna try again?

Thanks

Here is the link: http://xurl.es/2pee5