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High Power Cardioid Subwoofer Speakers Pro Audio DJ Passive 3600W 21" PA Sub boxes

Categories Subwoofer Speakers
Brand Name: RKB
Model Number: INF-21
Certification: CE / ROHS / SGS
Place of Origin: China
MOQ: 8 pieces
Price: Negotiable
Payment Terms: T/T, Western Union
Supply Ability: 500 pcs per month
Delivery Time: 5-15 working days upon receipt of payment
Packaging Details: Hard carton box or Flight case at extra cost
Components: 2 x 21" front + 1 x 21" rear
Frequency Response: 27Hz - 90Hz(±3dB)
Sensitivity(1W/1M): 106 dB
Peak SPL: 144 dB (Front); 141 dB (Rear)
Rated Power: 2400W (Front); 1200W (Rear)
Peak Power: 9600W (Front); 4800W (Rear)
Impedance(Ohm): 4 ohm (Front); 8 ohm (Rear)
Cabinet Finish: Germany Water Paint
  • Product Details
  • Company Profile

High Power Cardioid Subwoofer Speakers Pro Audio DJ Passive 3600W 21" PA Sub boxes

High-Power Cardioid Subwoofer Design Pro Audio DJ Passive 3600W 21" PA Sub boxes with high strength plywood black

Model number: INF-21


  • Triple 21" passive subwoofer speaker, front: 2400W RATED/9600W PEAK POWER, Rear: 1200W RATED/ 4800W PEAK POWER.

  • Voice Coil of the 21” driver is 6 inches. PHT voice coil wire inside and outside rounding and BAF voice coil bobbin, can endure high temperature. (VC: 152.4 mm ; Mag: 330.25 mm)

  • The cone papers and spiders are imported from UKM.

  • Cardioid dispersion pattern avoids unwanted energy behind the system.

  • Greatly reduces the reverberant field at low frequencies, providing highest accuracy in low frequency reproduction.

  • Selecting Hypercardioid mode in the amplifier optimizes the tuning of front and rear channels for a maximum rejection at the left and right sides behind the cabinet

  • Wooden lid for front grill is provided, as well as wheels at the rear side is included.





2 x 21" front + 1 x 21" rear

Frequency Response

27Hz -90Hz(±3dB)


106 dB

Maximum Peak SPL

144dB (Front); 141 dB (Rear)

Rated Power(RMS)

2400W(Front); 1200W (Rear)

Peak Power(RMS)

9600W(Front); 4800W (Rear)


4 ohm(Front); 8 ohm (Rear)



Dispersion Angle (-6dB)



1xNL4 Speakon

Enclosure Material

High-strength Plywood

Cabinet Finish

Germany Water Paint

Dimensions (W*D*H)

685 x 1180 x 1040 mm

Net. W.

150 kg


  • Large Scale indoor or outdoor concerts / Shows
  • Large theaters / Auditoriums
  • Large touring sound system

Competitive Advantage:

21" Cardioid Subwoofer

The INF-21 is a triple 21" cardioid Subwoofer for Installation Applications, incorporating excellent patented loading principles, designed for use in applications requiring accurate and powerful reproduction of low frequency energy at very high levels.

It has two bass-reflex chambers containing three 21" drivers, two facing forward in one chamber that are driven from one channel of amplifier and one facing backwards driven by another amplifier channel.

Product Display:

what applications is a cardioid subwoofer configuration appropriate for?

There are several situations where cardioid configurations can be useful.

For instance, when using conventional subwoofers with a wall behind them, the back wave will bounce back and cancellations will happen at the front (That’s because the subwoofers radiate in all directions). In this case, a cardioid configuration will radiate very little pressure backward, hence minimizing that effect.

When using conventional subwoofers off the stage, the singer/ talker will be affected by the subwoofer frequencies. Cardioid subwoofers will help the sound engineers to clean the subwoofer frequencies and clarity will be grained on the stage.

Introduction of the company:

With 15 years experiences of manufacturing sound products, Guangzhou Hongxiang Audio Equipment Co., Ltd, is growing up so fast these years. Our Brand - RKB AUDIO is now well-known to everyone domestic and overseas. We take great pride in providing clients all over the world with the most competitive sound products and the most excellent services. We always concentrate on designing and manufacturing the best sound system at prices that fit everyone’s budget.

With 30000 square meters work plant, and with 200 talented employees and leading technology, RKB AUDIO manufactures and supplies a wide range of professional sound system, including line array speakers, subwoofer speakers, full range speakers, stage monitor speakers, and professional power amplifiers. All our products are widely used in the applications below: touring, rental market, fixed installations, indoor or outdoor events, multimedia halls, concerts, theaters, churches, etc.

We will not tell you how good our R&D and production team is, and we will not tell you that how we sell our products to over 88 countries abroad, but we will sincerely invite you to try our sound products to find out the answers. Now you've got talent, and you’ve got the market. All you need now is the best pro audio equipment to show your skills.

We firmly believe that, with your continuous support and our unremitting pursuit, Germany RKB AUDIO must be always standing high in the Reinforcement Kingdom, and we are sure that you will enjoy our great sound and service. (OEM/ODM is welcome.)

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