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A bolt-on transformer enclosure module, the MTC-CBT-70T from JBL is designed to adapt CBT 70J-1 and CBT 70JE-1 (and CBT 70J-1/JE-1 arrays - all sold separately) for use on distributed loudspeaker lines. It allows for a single distributed system amplifier channel to drive multiple speakers, as well as the capability for long cable runs. It features transformer taps for 120W, 60W, and 30W for 70V and 100V distributed lines, plus 15W for 70V only. Customer-supplied cable to screw-down terminals within the enclosure are the method of connection. It comes with 2 gland nuts – one for the cable into the enclosure from the amplifier and one for the cable from the enclosure's terminal strip to the loudspeaker's input terminal. These gland nuts make for a water-tight seal when used with round-jacketed cable with outside diameters of between 0.16" (4mm) and 0.36" (9mm). The transformer's tap selection is achieved via the terminal connection of the cable from the power amplifier to the appropriate terminals on the enclosure's internal terminal strip. Additionally it includes mounting holes that fit via two 6mm screws to any of the two side-by-side insert points on the back of the CBT 70J-1 or CBT 70JE-1 cabinet (both sold separately).


  • 1x MTC-CBT-70T bolt-on transformer enclosure module for CBT 70 models
  • 2x 6 mm (x 15mm length x 1.0 thread pitch) bolts, flat washers, and lock-washers


  • Adapts the CBT 70J-1 (and 70JE-1) for Use on Distributed Speaker Lines
  • 120W, 60W, 30W for 70V or 100V (plus 15W for 70V)
  • Bolts onto Back of CBT 70J-1 or 70JE-1 Speaker
  • Gland Nuts Provide Watertight Seal


  • Transformer Taps: 120W, 60W, 30W (and 15W at 70V only)
  • Connection: CE-compliant barrier strip terminals. Terminals accept up to 8mm outside 4mm inside open-lug (#6 or #8) plus bare wire up to 2.5mm² (12 AWG).
  • Terminals:
    • Terminal 1 = Common (black wire from transformer)
    • Terminal 2 = 120W @ 70V, N/C @ 100V (orange wire from transformer)
    • Terminal 3 = 60W @ 70V, 120W@ 100V (purple wire from transformer)
    • Terminal 4 = 30W @ 70V, 60W @ 100V (blue wire from transformer)
    • Terminal 5 = 15W @ 70V, 30W @ 100V (white wire from transformer)
    • Terminal 6 = N/C (no wire from transformer)
    • Terminal 7 = + Output to loudspeaker + terminal (yellow wire from transformer)
    • Terminal 8 = – Output to loudspeaker - terminal (green wire from transformer)
    • Maximum Insertion Loss = Less than 1 dB at any tap.
  • Gland Nuts: Two total. One gland nut by the transformer selection terminals for cable from amplifier and one gland nut by the transformer secondary terminals (green and yellow wires) for output to speaker terminals. It is recommended to orient gland nuts toward bottom of enclosure.Watertight seal requires round jacketed cable with outside diameter between 0.16" (4mm) and 0.36" (9mm).
  • Mounting to Speaker Cabinet: Two holes in the back of the enclosure 2.75" (70mm) apart. Insert included 6mm screw from inside MTC-CBT-70T enclosure, using 1 flat washer and 1 lock washer, into the side-by-side M6 insert points on the back of the CBT70J-1 or CBT70JE-1 cabinet.
  • Enclosure Material: Fiberglass filled ABS.
  • Environmental Capability: IP-55 rated, per IEC529. UV, moisture and salt-spray resistant.
  • Agency Rating: Transformer UL registered per UL1876, Isolating Signal and Feedback Transformers for Use in Electronic Equipment.
  • Color: Black
  • Dimensions (H x W x D):
    • Including gland nuts: 6.2" x 4.5" x 3.4" (157 x 114 x 86mm)
    • Enclosure only: 5" x 4.5" x 3.4" (128 x 114 x 86mm)
  • Weight:
    • Net: 2.5 lbs. (1.13 kg)
    • Shipping: 3 lbs. (1.36 kg)
  • Note: The MTC-CBT-70T extends 86 mm (3.4") from the back of the CBT cabinet.

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