Positional Sensing?

Discussion in 'Electronic Drum Zone' started by Cableaddict, Aug 23, 2017.

  1. Cableaddict

    Cableaddict Member

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    I have been using a partially-electronic kit in my studio since 2003. I am extremely confused about the concept (and technical implementation) of "positional sensing." I hope someone can clear up the fog:

    I have a set of HART pads purchased in 2003. I just use 2 kicks, 4 toms, and an auxillary snare. All have Harts TE3 technology (has to do mostly with the backplate, for even response) - But they don't have the TE3.2 technology. I used to think the TE2 denoted dual triggers, and hence positional sensing, but I recently read that no, the 2 denotes a change in how the sensor was mounted. (Using a base inside the drum, and a short piece of foam underneath.)

    According to my notes, Peter Hart once confirmed to me that my toms do support Full positional sensing, but they only have one trigger. HART is out of business so I cant ask Peter a followup question. I've read different views online about this. Some say you need 2 sensors, while others claim you only need a single sensor, in the center of the head, in conjunction with a compatible module.

    Since my DDrum2 brain did not react to such pads, (I dont THINK) I never worried about it.

    Im now considering upgrading my brain, and so I want to have positional sensing, if possible. Perhaps I have it & dont know how to use it, or perhaps I can modify my pads? SO:


    1: How does positional sensing actually work? That is, how are the pads designed, and how does a module interpret that signal? Can you really use just one sensor, with a mono cable?

    2: What about the snare? It DOES have two sensors, but one is for the rim.

    3: If I do NOT have positional sensing, does anyone know of a way to convert my pads, instead of selling / replacing them? I really like how they look & feel.

    4: Once you DO have both pads & a brain that does positional sensing, if you want to use VSTi generated drum sounds instead of whats in the brain, how do you set up sounds so that they, also, respond to this information? I am so lost on this it isnt funny.

    5: AND FINALLY: For those that have played systems with & without this technology, other factors being reasonably close, how important is it to have this? On the snare? On the toms?


    - THX.
     
  2. TDM

    TDM Yapping Internet Mutt

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    As far as positional sensing is concerned, the majority of the processing happens in the module. Roland uses both the center-mounted head piezo and rim piezo for the computations, as there is quite a bit of cross-talk between the two piezo elements. The module expects this cross-talk and if it isn't there, the triggering (and especially positional sensing) do not work properly.

    Your single piezo pads likely won't give Roland flagship modules what they need for positional sensing. Also, you must have one of the Roland flagship modules (TD-12, TD-20, TD-30, TD-50) as these are the only modules that support positional sensing. The TD-30 and TD-50 greatly improve on the positional sensing provided in the TD-20. For example, in the TD-20, only the snare drum input has positional sensing. On the TD-30 and TD-50, the snare, ride cymbal, and toms all have positional sensing (for head and rim), however, only the ride and snare have sounds in the module that react to the positional sensing data. The TD-30 and TD-50 do react to positional sensing tom data in a minimal way; they have different rim and rim shot sounds for deep, medium, and shallow rim shots. That said, despite being output over MIDI, the head positional sensing data for toms is ignored by the internal internal sound generators.

    VST drum libraries typically do not provide positional samples, so you're somewhat stuck with the positional sounds generated by the module. As I understand it, Roland has multiple patents on their positional sensing technology, including patents on mesh heads and the various algorithms and processing they do with the two piezo system. This is why you won't see this technology used (yet) by Yamaha and others. Roland's patents are running out fairly soon, so this may open up the market in terms of products that provide this kind of positional sensing.

    There are other positional sensing technologies, such as the membrane technology used in the Mandala Drum. The Mandala Virtual Brain software provides positional samples, so if you really want an electronic drum instrument that provides high end sounds along with positional sensing, this would be one way to get it. Also, Mandala Drums themselves (no software needed) output MIDI over USB, including note, velocity, and position (controller) data. Thus, you can use Mandala Drums to trigger any software on your computer that accepts MIDI input. The Mandala's 128 zone positional sensing far exceeds the seemingly limited three to five zones Roland gets from their approach.

    In general, for sonically convincing traditional drumset style playing, positional sensing is less important than having high resolution velocity response. Along with velocity response, having high quality, massively multi-layer, round robin, velocity responsive samples is critically important - at least this is what I've found for traditional drumset style playing. It's in this later aspect that most drum modules utterly fail, including all of Roland's flagship modules. The internal sounds in the module do not provide enough velocity layers and do not provide enough pseudo-random round robin samples (if any). The only modules I know of that approach what you'll get (sonically) from massively multi-layer VST drum libraries are 2Box DrumIt Five, 2Box DrumIt Three, and Pearl Mimic Pro.

    Ironically, the instruments in the Mandala Virtual Brain are limited to three velocity layers, but this is per zone. Consequently, unlike a Roland module where the head represents a single zone with perhaps three to five velocity layers, the Mandala uses three layers for each of many zones across the head. This means the Mandala actually provides many more velocity layers than Roland. So, the Mandala has more velocity layers and far superior and more detailed positional sensing.

    In case you are not familiar with it, here are some links to the Mandala Drum:

    Mandala Drum Manufacturer Synesthesia Corporation
    http://www.synesthesiacorp.com/

    Mandala Drum Demo by Jason Chumley
    (http://()
     
    Last edited by a moderator: Oct 12, 2018
  3. TDM

    TDM Yapping Internet Mutt

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    Should have done the following in my initial reply! Answers to your questions:

    "1.1) How does positional sensing actually work? That is, how are the pads designed, and how does a module interpret that signal?"

    Roland's positional sensing uses a mesh head, a center-mounted head piezo, and a side-mounted or center-mounted rim piezo. In the case of the center-mounted rim piezo, the piezo is isolated several inches underneath the head piezo and receives its vibrations from the cake-pan style basket cupping the rim. That same basket holds both head and rim piezo elements, but the head piezo receives most of its vibrations directly from the head (through a foam coupling) whereas the rim piezo receives no direct vibrations from the head and gets most of its vibrations from the basket itself.

    There is a lot of cross-talk between the two piezo elements. In other words, when you strike the head, the rim piezo sees a lot of the same vibrations through the basket. Similarly, when you strike the rim, the head piezo sees a lot of the same vibrations because the head is still set into motion. The module determines which piezo has greater amplitude and uses this to decide whether a rim or head strike occurred. Also, using the wave shapes from both piezo elements, the module determines where the strike occurred.

    Roland's positional sensing algorithm is an even more complex than my previous paragraph alludes, because you can strike the rim and head together, and the algorithm figures this out (too) and generates the appropriate rim shot sound accordingly. So, you get pure rim sound with positional sensing, pure head sound with positional sensing, and rim shot sound (head and rim sound simultaneously) with positional sensing. Where the algorithm utterly fails is if you strike the head and rim together. Meaning, not a rim shot with a single stick, but rather a rim strike with one hand / stick and a head strike with another hand / stick, and both of these strikes happen simultaneously. The algorithm does not account for this and outputs either a rim sound, a head sound, or nothing.

    While the Mandala Drum has vastly superior positional sensing for its head, it does not have any of Roland's integration of head, rim, and head and rim simultaneously. Mandala really has no traditional concept of the rim. The way one gets rim sounds from a Mandala Drum is by assigning rim sounds to the outer most zone. If you strike the outer most zone and press on the pad surface with your hand at the same time, this produces cross-stick sounds, which are modifiable based on where you place your hand on the pad surface. All of this introduces new ways of getting and playing rim sounds, but it is nothing like playing the rims of acoustic drums. If you want rim and cross-stick playing that is more like acoustic drums, Roland's triggering and positional sensing approach provides this much better than Mandala.

    "1.2) Can you really use just one sensor, with a mono cable?"

    Roland's positional sensing requires both head and rim piezo elements and a stereo connection. Single zone, monophonic pads will not work properly and are not supported for positional sensing. You could try plugging in one of your single zone pads and see what the module does. My guess is you'll get significantly downgraded positional sensing response, if any at all. Roland's positional sensing depends on the cross-talk that occurs from the head and rim piezos.

    "2.) What about the snare? It DOES have two sensors, but one is for the rim."

    If your snare pad uses Roland-style head and rim piezo elements, then it should work fine for positional sensing on a Roland module. There are many, third party, dual zone, Roland-style pads that work fine.

    "3.) If I do NOT have positional sensing, does anyone know of a way to convert my pads, instead of selling / replacing them? I really like how they look and feel."

    You can add rim piezos to the shells of your pads. The rim piezo does not need to be center-mounted. You'll need to wire a stereo connection for each pad and, as I recall, Roland inverts the polarity of the rim versus head piezo. With some experimenting, I see no reason why you could not get similar response to a Roland pad. The parts (piezo, wires, stereo output jack) are very inexpensive. However, one limitation is those Hart pads are very shallow. You may not have enough room to mount a full size piezo element inside, on the side of the shell. Still, you can probably get smaller piezos that produce similar output.

    "4.) Once you DO have both pads and a brain that does positional sensing, if you want to use VSTi generated drum sounds instead of whats in the brain, how do you set up sounds so that they, also, respond to this information?"

    To the best of my knowledge, no VST drum libraries support positional sensing. Roland modules do send out positional sensing data over MIDI, but VST drum libraries ignore this data. To date, in a VST drum library, I've never seen any mapping facility for positional sensing data. And indeed, I don't know of any VST library that provides positional samples. For the most part, VST drum libraries are far more advanced than and far superior (sonically) to drum modules. However, positional sensing is one area VST drum libraries have yet to address. Side note: the Mandala software does provide positional samples, but the software only works with Mandala pads.

    "5.) For those that have played systems with and without this technology (Ed: positional sensing), other factors being reasonably close, how important is it to have this? On the snare? On the toms?"

    There is no question that positional sensing opens up a world of creative possibilities. It is certainly nice to have on snare drum and ride cymbal, and I use it on toms too. I have a Roland TD-30 module and while the module only has full positional sounds for snare and ride, and limited rim positional sounds for toms, none-the-less, I use positional playing techniques frequently. Unfortunately, Roland's positional sensing approach is quite limited (overall) in that it seems to provide about three to five zones of position detection. Contrast this with a real drum or real cymbal, where there are thousands upon thousands of positional expressions, and the Roland approach seems entirely inadequate.

    The flip side is the velocity layers in Roland modules are extremely limited (again, maybe three to five layers) and machine gunning is also a significant problem. Contrast this with VST drum libraries that provide many more velocity layers, higher quality samples, and pseudo-random and round robin techniques that eliminate machine gunning. I'll take the VST sounds over Roland's positional sensing because the VST sounds are vastly more expressive; VST sounds are not as expressive with position (there is none), but they are HUGELY more expressive with velocity.

    The new drum module from Peal (Pearl Mimic Pro) has no positional sensing, but it incorporates VST quality samples directly in the module. Pearl partnered with VST developer Steven Slate Drums. The software inside Mimic Pro is essentially a VST drum library along with all the same algorithms; it's Steven Slate Drums 5. Take a listen to the videos below. There is no positional sensing, but the sonic result is vastly superior to all of Roland's modules, including the latest TD-50 flagship module.

    Drum-tec Mimic Pro Preview
    ()


    Drum-tec Mimic Pro Demonstration
    ()


    Drum-tec Rocks out on Mimic Pro
    ()
     
    Last edited by a moderator: Oct 12, 2018
  4. Cableaddict

    Cableaddict Member

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    Wow, thanks for the intense responses!

    I've been slammed with work, so not yet able to respond, but I'll definitely have some followups & alternate views soon.

    Much appreciated !!!!!!!!!!!!!!!!!!!
     
  5. TDM

    TDM Yapping Internet Mutt

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    You are most welcome. My posts are essentially brain dumps as I considered your questions. They are not well summarized. Sorry about that. Hopefully some of the ideas are of use to you. :)
     
  6. vinito

    vinito Well-Known Member

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    Just so those that don't already know are updated, the new Superior Drummer 3 now does support positional sensing and it looks to do a good job too (link to a demonstration video I found)
    So you can now use VST with modules that support positional sensing, including MegaDrum with appropriate p.s. board added (which hopefully works well since that's the module I'm aiming at).

    I'm still at the beginning, cutting-teeth stage of putting a DIY setup together and learning about all this, but I'm looking forward to getting SD3 someday and taking advantage of this, as well as all the rest of it.
     
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