Tech Notes
System Calibration
Because it is difficult to deduce exact levels from the LEDs, we recommend calibrating your system based on electrical input levels to the 3D. Using a 500 Hz test tone, an input level of 0 dBV (1 Vrms) produces 124 dB-SPL. Figuring from that reference, the Perform Mode threshold of 105 dB-SPL is produced with a 19 dB lower input of -19 dBV (112 mVrms), and 85 dB-SPL is produced from an input of -39 dBV (11.2 mVrms). The sensitivity of the 3D-L with balanced drive is 3.5 dB lower than these numbers at full gain, so the respective input levels will be 3.5 dB (1.5x) higher. Turning down the Monitor gain control from its full clockwise position reduces these sensitivities further, increasing the required drive levels. In the middle of the Monitor gain control's rotation, the sensitivity reduction is about 17 dB, requiring 17 dB higher (7x) drive levels.
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Limiter & LED Behavior
The specified limiter threshold is 105 dBA (85 dBA for the monitor input when in Full Ambient mode). The yellow LEDs, while related to these limiter thresholds, should be considered as indicators of general loudness and not as direct indicators of limiter action. They first start to flicker yellow at about 16 dB below the limiter threshold in either operating mode. They reach what could be called "bright" at the limiter threshold, whether the limiter function is engaged or defeated. About 6 dB beyond limiter threshold, they add a bit more brightness, up to what could be called "maximum brightness". Thus, the LEDs light to indicate signal presence at listening levels (well below the limiter threshold), but go to bright illumination to indicate "loud," with average signal levels in the general range of 105 dBA (Perform) or 85 dBA (Full Ambient), regardless of Mode Switch position.
The 3D system's limiters and "Loud" LEDs are slow, average responding, so short duration peaks can be much louder than indicated, as can bass frequencies, due to reduced limiting action in that frequency range. The SPL indications also correspond to a sound as it would be measured outside the ear, before entering the canal. Due primarily to the effects of the ear canal, for frequencies from 1.5 to 5 kHz, sound levels at the eardrum are relatively higher than at other frequencies (with or without the 3D). Considering all these factors, use of the limiter does not, by itself, guarantee safe monitoring.
NOTE: 105 dBA is not considered a safe level for extended listening. The intention of the limiter is to provide a musically pleasing limiting function while guarding against occasional excessive levels. Normal monitoring levels for extended performance times should not be entering the limiting region.
Battery Removal
To remove a used battery, grasp the base of the battery and push in firmly toward the terminals while lifting upward.
3D Active Ambient Page Links
System Set-up
3D Bodypack Mixers
Internal Controls
3D Earphones
Indicator Lights
Inserting Earphones
Technical Specifications
3D User Guide PDF (456 KB)
Helpful Links
How To Order
Audiologist Referral
Hearing Conservation info
Sensaphonics Audio Seal Test
Got questions? Ask The Sound Guy!
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