JBL Professional Control 321CT - 12″ Coaxial Ceiling Speaker with HF Compression Driver and Constant 90° Coverage (70/100 V)
The JBL Professional Control 321CT is a coaxial point-source in-ceiling loudspeaker designed from the ground up to deliver high SPL , excellent intelligibility , and extremely consistent 90° coverage in professional installations. Its shaped metal baffle acts as a large-diameter waveguide : the 300 mm (12") cone itself guides the high frequencies to maintain consistent directivity across the broadband and a uniform timbre throughout the listening area. The assembly combines a Kevlar-reinforced woofer with a 50 mm voice coil , a 25 mm compression driver (1" exit), and a steep crossover network , resulting in smooth midrange response and superior clarity for speech and background music.
The CT version integrates a 68W multi-tap transformer for 70/100V lines (68/34/17W and 8.5W at 70V outlets), with a typical loss of ~0.9 dB . Its performance meets the demands of challenging projects: 34–18 kHz (−10 dB) , 47–16 kHz (±3 dB) , 94 dB sensitivity (2.83 V/1 m in half-space), and a maximum SPL of 118 dB average / 124 dB peak . The 366 × 366 mm square baffle incorporates EZRail™ for easy mounting on the optional MTC-300BB12 backbox (3 ft³), with a 378 × 378 mm ceiling cutout. It is plenum compliant when installed with a UL-listed backcan.
Main features
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90° conical coverage and constant directivity over a wide bandwidth: fewer points for the same area.
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Premium coaxial system : 12″ Kevlar woofer (VC 50 mm) + 1″ compression driver with titanium diaphragm.
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High performance : sensitivity 94 dB , 250/200 W IEC (2 h/100 h) and 118/124 dB (average/peak).
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Integrated 70/100 V transformer : 68/34/17 W sockets (and 8.5 W at 70 V ), low saturation.
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Professional Installation : EZRail™ , screw barrier connector and MTC-300SG12 contemporary grille option.
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Plenum & regulations : suitable for air handling spaces with MTC-300BB12 (UL1480, UL2043, NFPA-90/70; DoC Control 300).
Product benefits
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True uniformity of level and off-axis timbre; improves intelligibility with fewer unwanted reflections.
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Lower installed cost : controlled coverage allows reducing the number of speakers per zone without sacrificing quality.
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System versatility : native at 70/100 V ; transformer bypass capability for low impedance operation by qualified personnel.
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Quick and clean installation : assisted assembly, robust connectivity and official accessories for back can/grilles.
Use cases
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Retail, restaurants and hotels with background/foreground music and clear advertisements in large areas.
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Corporate, education and healthcare with priority given to uniformity of coverage and plenum compliance.
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Convention centers, museums and airports that require high SPL, high intelligibility and discreet aesthetics.
Frequently Asked Questions
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What are the transformer's power ratings? 70 V: 68/34/17/8.5 W ; 100 V: 68/34/17 W.
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Can it be used on 8 Ω? Yes, the 321CT allows transformer bypass following the manufacturer's procedure (use by qualified personnel).
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What back can and grille does JBL recommend? The MTC-300BB12 (3 ft³) for plenum and bass response, and the MTC-300SG12 square grille as an aesthetic option.
Project description
JBL Control 321CT coaxial ceiling speaker, 90° coverage; frequency response 47–16 kHz (±3 dB) / 34–18 kHz (−10 dB) ; sensitivity 94 dB (2.83 V/1 m in half-space); Q 8.7 , DI 9.4 dB ; max SPL 118 dB average / 124 dB peak . 70/100 V transformer with 68/34/17 W taps (and 8.5 W @ 70 V ), typical loss ~ 0.9 dB . Crossover 1.8 kHz (HP 18 dB/oct + conjugate / LP 12 dB/oct). Transducers: LF 300 mm Kevlar (VC 50 mm) + HF compression 25 mm (1″ exit). 366 × 366 mm baffle, depth from the back of the baffle 240 mm ; 378 × 378 mm ceiling cutout with MTC-300BB12 ; suitable for plenum with UL listed backcan.
