Re-enclosed JBL SB210 Subwoofer

Unsatisfied with my JBL SB210 low frequency, I designed and built replacement enclosures. 

The SB210 is a dual 210mm subwoofer, using ceramic cones in a polymer enclosure.

Specifications of JBL's original SB210 are 

  • 48Hz (-3dB)
  • 42Hz (-10dB)

My redesigned enclosure offers

  • 29Hz (-3dB)
  • 16Hz (-10dB)

The first hurdle was the absence of datasheet for the speakers themselves, as they were never distributed outside of the SB210 system.

After contacting JBL Professional, they were kind enough to provide me with the data.

  • Fs : 25.38 Hz
  • VAS : 73L
  • Re : 3.32 Ohms
  • Qms : 3.31
  • Qes : 0.470
  • Sd : 340.00 cm2

These specifications were entered in Dominique Petoin's database and you can now find it there. As I was trying to reach lower frequencies, the bass-reflex architecture was the obvious choice. 

Multiple tuning were possible, and I chose to go with the Bessel alignement which offered a gentle dropoff curve.

The simulation gave 

  • @92 dB ±2.13 mm of membrane travel
  • 103.0 dB @1m for a single subwoofer (but I built two)

Enclosure specifications

  • Volume : 65.4L (net), 70.82L (raw)
  • Reinforcement : 164cm (5x5cm)
  • Volume renforts : 4.1L
  • Frequency tuning : 19.9Hz
  • Bass-reflex vent : ø 9.4cm (in), ø 10cm (out), 72cm (length)
  • Top/Bottom : width 33.4 cm x depth 38.4 cm
  • Front/Rear : width 33.4 cm x height 76.5 cm
  • Sides : depth 34.0 cm x height 76.5 cm

I used 38mm thick MDF, as it is a very "deaf" material, fairly inexpensive and extremely sturdy in this thickness. 

I didn't have speakon terminals so I went with a ghetto solution in the meantime.

Notice how the vent is glued with Polyuerthane to the structure as to avoid any parasitic noises.

Listening & Conclusion

I can't stress how much I love those subwoofers. They are ungodly and extremely heavy but the sound... They go as low as you might ever want a sub to go, and are able to keep up with high powers. Not the slightest resonance or airflow sound can be heard.

At the time, I actualy discovered a spectrum of bass I didn't know even existed in some tracks. Quality headphone can reproduce down to 20Hz, but I would say that the 20 to 40Hz range needs to be felt with actual speakers.

Currently they are in the house, fed by a Crown CT8150 with active filtering using the MiniDSP 10x10 HD. They are filtered to reproduce anything below 50Hz.