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  • Positional Sensing Woes

    I posted a thread a bit ago about my struggles with positional sensing on my new-to-me td-12. I've tried everything short of building a new trigger. Some background, I have drop-in cake pan triggers using 35mm piezos for head and rim. I'm using the octocone from UFO drums and at this point I think this is the problem. I've tried cone heights from less than 1/16 to almost 1/4in above the rim. I've tried all tensions from fairly loose to very tight to the point that it sounded like I was hitting the cake pad itself when I hit the head. I've also tried switching the polarity numerous times. With the black on the sleeve I only get outside hits and with the red on the sleeve I only get center hits. Now I am thinking it is the cone itself. I've attached a picture to show this. There is not a line cut out from the base of the cone for the wires which puts a slight bend on the piezo. This is for all my drums which none of are getting PS. My next stop is to get cones from the canadian peeps and try that out. Any other suggestions?

    File_000 (11).jpeg
    Last edited by Aka Wayne; 02-14-19, 02:14 PM.

  • #2
    Hi!

    PS is dependent on these things:
    • A center mounted piezo
    • the size of the Drum - bigger = easier to detect PS. I would say you need 12-14Ē to make it to fire.
    • Polarity - the ps function looks on the first positive half wave...and a drum hit canít start with a negative first half wave...then the PS function is lost.
    • The TD-12 supports PS on the snare, toms and ride inputs. Not all sounds on TD -12 supports PS. Most snare sounds have ps support on the head sound. The Tom sounds seems to have PS attached to the rim...(!) Strange...
    Best regards

    Anders / www.zourman.com
    Last edited by angr77; 02-14-19, 11:04 PM.
    Pearl CrystalBeat and Sonor Safari, Roland CY-14/13R/15R/12CR, RT-10x,2xBT-1,VH-11/12/13 & KD-10, Quartz, Pintech Dingbat, Triggera D14,D11, ATV AD-h14, 120MHz MegaDRUM with PS board, 2box 5&3, dd4SE, TD-9, Addictive Drums 2.1.8. All ADpaks, Microsoft Surface PRO, Macbook, Pearl Throne Thumper, Zourman HH & Ride Conv Kit www.zourman.com

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    • #3
      Thanks for the response! I have a center mounted piezo, a 14in a-to-e snare and have changed the polarity many times to no avail. I'm thinking it might be the not so cone shape of the octacone or that small gap you see between the cone and the piezo caused by the wiring. I'm pretty stumped.

      Another weird thing. I can't get any rimshot sounds on my toms. Only the rim click. And the pos meter doesn't move at all for my toms either. Is the rimshot sound for toms dependent on the rim positional detection working?

      I appreciate any and all input. Thanks!

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      • #4
        One other thing. Has anyone gotten positional detection to work on an a-to-e cymbal? I know it is not easy to achieve due to the unpredictable vibrations of a dampened acoustic cymbal but figured someone on here has gotten it to work.

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        • #5
          Have you tried asking Mitch about whether the octacones work with the positional sensing? Heís usually pretty helpful.

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          • #6
            I posted a question on his website and have not gotten a response.

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            • #7
              More testing and more confusion... It finally dawned on me to plug the snare input into my converted 16in floor tom that uses a quartz trigger harness. This I thought would allow me to test the cone theory. Turns out ps worked right away with the stock pd125 settings. I was excited and took the harness off the floor tom and moved it to my aluminum 14in pearl sensitone elite snare with the prism mesh head. And... no positional detection. The only difference besides size between these set ups now would only be the drum head. The snare uses the prism and the floor tom uses a go edrum head that is clearly made from a different type and weave of mesh. Now I just got a 15in cake pan to use for the floor tom so that he harness can be for the snare and am thinking about getting a new head that has been proven to work with positional detection. There is a good review for jobeky heads on vdrumtips and I know Roland and drum-tec are good but expensive. Are there any other options from proven brands?

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              • #8
                A tough one. I have tried cheaper heads without success. That actually means I was getting odd ps so I never knew what was being triggered. I did get a drum-tec head and it works fine. I have the design series which are very close to Roland type mesh. The ones that struggle are the material type mesh heads. I also tried a zed head which was like a trampoline until I put foam round the edge of it to kill it a bit. Someone else must use another make that works with ps? Anyone?
                Roland TD30 module on TD20 kit SD3 with various kits. Pearl Masters Kit, Yamaha 9000RC original natural wood finish. Cymbals from Zildgian Pasite and Sabian. Loads of percussion bits. Cubase and Wavelab always current versions.

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                • #9
                  Thanks for the information. What do you mean by material type? The prism mesh has a cross weave type of mesh. I think it was stated to be 3 ply. Here's a photo.
                  image.jpeg
                  Last edited by Aka Wayne; 02-18-19, 05:21 PM.

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                  • #10
                    Yes thatís the type of head that I couldnít get ps to work with. I tried different tensions but the ps was just all over the place when monitoring the screen on my td30. Iím not sure why but that type of head just doesnít work.
                    Roland TD30 module on TD20 kit SD3 with various kits. Pearl Masters Kit, Yamaha 9000RC original natural wood finish. Cymbals from Zildgian Pasite and Sabian. Loads of percussion bits. Cubase and Wavelab always current versions.

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                    • #11
                      Thanks MKOK!!! I think I'm finally on my way to getting this to work!

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                      • #12
                        So I finally got the drum tec reel feel heads. I got one for my snare and one for my high tom. I love them so much! It has totally evened out trigger response across the head and greatly reduced hot spotting. It just seems so much more sensitive and life like than my prism heads. Plus they look and feel (rebound) amazing.

                        But..... I am still not getting reliable positional detection. It will transition to the out side only if I hit very hard right at the bearing edge. Then it goes right back to center; there is no in between. I now have a reel feel head on a 14in aluminum snare that is triggered with the quartz harness trigger. As far as I know all of these items have been used for DIY to achieve positional sensing. The one thing I can think is that I have a 35mm head piezo and I read that roland uses 27mm. Could this be the difference?

                        I'm also going to continue messing with trigger settings but I don't have too much time on my hands these days to fiddle around with settings. I will check my current snare settings and update them later. I also did a factory reset with little change.

                        One last thing. I don't seem to get any rim dynamics (on any drum) or rimshots (at least on my high tom for sure). No matter how hard I hit I only get rim clicks. Are rim dynamics determined by the rim or head piezo? If there is something not right with my head piezo sensing will that make rim dynamics work incorrectly for my snare and toms? Thanks for any info and help. This is painful but I think I'm getting somewhere.

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                        • #13
                          In a nutshell: you've been doing it completely wrong. Here's why:

                          Judging from your first pic with the cone on top of the piezo, and the cushion underneath, it's no wonder to me that the triggering is sub-optimal. Been there, done it...
                          This is a common mistake, and it becomes clear when you think a bit of how piezos work.They turn pressure force into voltage, where the crystal structure needs to be bended out of its natural form.
                          Best is to think of it is a trampoline: imagine you're standing on one, right in the middle. Now, would you expect your own movement to be stable and predictable when the trampoline is not rigidly tied along the rim? What would happen if it would stand on a thick gymnastic mat? That is the problem; the waveform you apply from the top overlaps with the excursions in the lower cushion, and the result is an uncorrelated combination.
                          [When doing serious piezo DIY, a scope IS mandatory, otherwise it's hit & miss without knowing what's going on!]

                          The cushion underneath has become 'the norm' since one would normally try to decouple external vibration from the shell on to the cone. That's okay for simple DIY, but it needs to be done differently when you want precise readouts. Positional sensing works by detecting the slew rate, not simple zero crossings of an arbitrary waveform over time.
                          The problem is pretty similar to decoupling a drum kit from the floor: you need mass in order to make dampening effective (-> inertia).
                          Suggestion: Have a rigid central platform, whatever kind. Then, put some dampening at the center, like poron or any sort of cellular silicone (needs to have as low memory as possible). But not too thick. Then (and this is important!): put a rigid surface on top, like a stack of big iron washers or so.
                          The piezo itself shouldn't be applied directly to the washers then. I'd advise to have them 'float' over a ring in a way that an air gap is left underneath. Some piezos like Murata have a plastic ring around the rim, I'd go for those as you can apply them right away. This way, the piezo can do its maximum excursion without being limited by external braking forces, thus no overlapping patterns in the waveform.
                          Of course the cone on top mustn't overlap then. The way you have it in the picture above is way too large. The cone must only be applied to the inner region of the disc. Again the trampoline analogy: would you enjoy jumping along the edge of it? Certainly not, the most fun is in the center. With the piezo, the voltage amplitude is ideal in the center, and the waveform is also the 'purest'. The more you go towards the edge, the more reflexions will pollute an otherwise intact transient impulse.
                          Last edited by sascha; 03-12-19, 03:56 AM.
                          MarkDrum YES e-kit highly modified (DIY hall-sensor based hihat, low-volume trigger cymbals, 16" DIY kick, 12" DIY snare + tom 3), Triggera 10" splash
                          Gibraltar 9607NL-DP Legless Hi Hat, Intruder Double Pedal
                          Shure SE215 in-ears w. CustomArt silicone tips

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                          • #14
                            Originally posted by sascha View Post
                            Of course the cone on top mustn't overlap then. The way you have it in the picture above is way too large. The cone must only be applied to the inner region of the disc. Again the trampoline analogy: would you enjoy jumping along the edge of it? Certainly not, the most fun is in the center. With the piezo, the voltage amplitude is ideal in the center, and the waveform is also the 'purest'. The more you go towards the edge, the more reflexions will pollute an otherwise intact transient impulse.
                            I really enjoy reading the theory about these kinds of things, thanks for that. The only question I have is in regards to this section. Roland triggers, and many others, don't follow this rule and yet they get perfectly usable results with the positional sensing. All the Roland cones I've seen cover the surface area of the entire piezo. Is there an explanation as to why it works fine for those builds versus your suggestion here? Thanks.

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                            • #15
                              Wow that is great information thank you so much! I made my original cushion based off of other builds I have seen. The cushion just covers the ceramic and allows the brass edges to be deformed by the edges of the cone. From what you're saying this is opposite of what it should be. You are saying to support the edges and allow the middle to flex, like a trampolin? So are you saying the harness style trigger that Quartz sells does not provide an adequate structure for the base that would result in good positional detection?

                              So back to rebuilding.... I have a solid platform base already. For my drop in cake pans I use a metal electrical cover and for the quartz harness it is a hard plastic base. I'll make a thin ring of foam dampening on the center (1/16th in ?). Ill put some washers on top for mass then cut a doughnut shaped cushion on top of the washers to support the outside edges of the piezo. Finally, place the cone only over the center (ceramic) of the piezo. Do you have a picture of a build that demonstrates this? I will upload a drawing of what I come up with later

                              One more thing, all cones I have seen are designed to go to the outside edge of the piezo. Do you custom make cones to have a smaller base diameter? Thanks so much for the insight!

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