Triggers sense vibration from one of three places: directly from the head, from the rim, or from the drum shell. Beyond that, there are two basic trigger construction types, those that stick to the head or shell with an adhesive (“head contact triggers”), and those that use some sort of housing to mount to the rim and then press the trigger assembly against the head (“rim mount triggers”).
All of these triggers use piezo crystal technology. Piezo technology isn’t some big mystery – we have piezo crystals all around us daily. Any piece of electronics that beeps, like a microwave, is probably using a piezo crystal as a speaker. When a piezo crystal has voltage applied to it, it vibrates, creating the beep sound. In drum trigger land, the crystal is used in the opposite direction. When we hit the drum, the head (or shell) motion vibrates the piezo, which creates a small amount of voltage that is sent to the trigger-to-MIDI converter. The trigger interface turns this voltage spike into MIDI information (note number, velocity, MIDI channel, etc.), and the MIDI information is sent to make the sound source play a sound.
Fig. 3. Generic head contact trigger
There are many drum trigger manu-facturers, and most sell head contact triggers (see Fig. 3). These are the generally the least expensive drum triggers, but also the most fragile. Since they permanently mount to the head with adhesive or double-stick tape, they usually stay on the drum all the time. As you can see, the sensor, exposed wire, and jack arrangement leaves it open to damage, most often pinching the wire where it passes over the rim. Don’t get me wrong, many professional drummers use this kind of trigger. They work great, but you have to take care of them.
Another trigger arrangement is the rim-mount trigger. The major players are ddrum, Roland, and Trigger Perfect. The ddrum rim mount trigger has been around longest. This trigger works very well, although it doesn’t have any sensor height adjustment to compensate for varying rim heights. Depending on the drum rim it mounts to, it may not even reach the head if the rim is very high, or in the case of low rims, may muffle the drum by pressing down on the head a little too much. This trigger also requires a XLR-to-1/4" cable to connect to the drum module, a cable you’ll be hard pressed to replace right before your 9:00 p.m. start time. That being said, all in all this is a good trigger.
I must put a disclaimer here. The next trigger is from Trigger Perfect, a company that I started in 1987 and sold a number of years ago. I designed and hold a patent on their rim mount trigger, but I’m doing everything to be objective. Honestly, I am.
Trigger Perfect’s rim-mount trigger offers performance similar to ddrum and Roland triggers. It also mounts on the rim, but has a number of improvements over the ddrum. Most notable is the trigger element height adjustment. This adjustment allows the trigger element to be pressed against the head no matter what the rim height is. There is also very little of the sur-face area of the sensor (trigger element) actually touching the head, thereby eliminating nearly all muffling of the drum. Like most other drum triggers it uses a standard guitar cable (1/4"-to-1/4") to connect to the drum module or trigger-to-MIDI interface.
Fig. 4. Roland RT-7K kick trigger
The last rim trigger is the newest (see Fig. 4). Roland’s RT-Series drum triggers draw design elements from all the triggers that have come before them. Not only do they have adjustable sensor elements (kick and snare), Roland has also cleverly applied the sensor design of the mesh headed V-Drum pads to the kick and snare trigger. The inverted cone trigger element assembly doesn’t muffle the head, and it also helps dampen false and double triggers. It’s important to note that the RT-3T tom trigger doesn’t even touch the head, it senses the head vibration through the rim, so we can have tom ring for days.