SoundQubed HDX4 Series 12" 2000W RMS Subwoofer

  • Sale
  • $599.99
  • Regular price $699.99
Shipping calculated at checkout.

Woofers use a mechanical suspension, the main component being the spider(s) attached to the speaker frame and the voice coil. The spiders are made from fabric layers that are saturated with resin, making the cured fabric harder. The resin in the fabric breaks down over time, which makes the fabric less hard. This process is what is termed: Break-in.

This hardness will resist motion from the voice coil, compressing the input signal. When power is applied past this compression point, the stress is directed to the glue joints on the coil and frame, as well as heat build up in the coil. This added power does not increase the sound output from the speaker due to the power compression from the suspension stiffness.

As the resin breaks down, the spider(s) soften and excursion naturally increases. As a rule of thumb, never apply more power than the hardness of the suspension allows in cone movement; when the cone movement stops increasing, stop applying power, or you will break something.

Most of the break-in will occur fairly rapidly, in the first month of playing, you will notice cone movement increases, bass will become louder and the resonant frequency of the sub will drop. Break-in will continue but slow down, as the fabric and roll geometry in the spider layers becomes most of the suspension resistance.

If you don’t have the set up to do a continuous break-in period, where you can monitor cone movement versus power input, keep gains low while monitoring the above process. If playing for only an hour or so a day then the break in may take a couple months.


The HDX line of subwoofers builds upon the HDC line, with design changes geared toward recent shifts in source material and the mainstream frequency tuning of our customer’s cars. All elements of the HDC subs were scrutinized for better performance at lower frequencies. The resulting HDX line is more efficient, plays lower, sounds better and sets a new bar for performance and value.

Lower frequency use requires an increase in excursion. We started with a new cast basket which allows larger diameter spiders to be used, provided more excursion room for both the cone and spider travel while providing open airflow path for increased heat dissipation.

New spiders were tooled to take advantage of the increased suspension travel, the number of rolls increased along with the roll heights. This extra material in the spiders increases the freedom of movement, lowering the Fs but allowing a high layer count for long term durability.

The surround profile was increased in height which, along with the new spider profiles, reduces material stress while increasing excursion ability. Cone area and moving mass remain virtually the same as opposed to inner-tube surrounds popping up here and there.

The extra throw places more demand on cone strength, the HDX now use a cone pulp reinforced with fiberglass strands and formed in a non-press method to increase the cross section area of the cone walls. This increases the rigidity of the cone without adding extra mass. The material cost and forming time go up, but the overall efficiency of the subwoofer is increased.

The voice coils in the new HDX have been strengthened in every way. The aluminum formers are thicker and black anodized to increase thermal transfer from the coil wire. USA wire and adhesives are used to increase the thermal working range of the coil.

This HDX overhaul increases the low frequency pressure that can be tuned into a system without sacrificing the impacts and brutal power that SQ subs have been known for. The .X subs give you more freedom to explore design choices with high efficiency, making the most of amplifier power and electrical resources.

NOTE – Rated power handling is after break-in period.

Order Processing is Two Days

HDX3 Series
RMS Power 1500W
Peak Power 4500W
Magnet Weight 300oz
Coil Diameter 3"
Coil Length 50mm
Usable Throw 68mm
Model HDX312 HDX315 HDX318
Woofer Size 12" 15" 18"
F(s) 26.92 Hz 26 Hz 27.59 Hz
Impedance D1 / D2 D1 / D2 D1 / D2
Z(max) 70.16 Ohm 63.8 Ohm 55.47 Ohm
Q(ms) 4.95 4.847 5.777
Q(es) .3409 .3665 .4724
Q(ts) 0.3189 0.3408 .4367
V(as) 28.59 Liters 78.08 Liters 168.6 Liters
n(0) 15.6% 33.96% 71.46%
M(ms) 440.9 grams 472.8 grams 410.9 grams
C(ms) 0.079 0.082 .081
Sensitivity 1W/1m 84.03dB 1W/1m 87.41dB 1W/1m 90.64dB 1W/1m
BL 31.45 30.49 25.14
Xmax 36mm 36mm 36mm
Sd 0.051 m2 0.082 m2 .121 m2
Displacement .13ft3 .17ft3 .23ft3
Mounting Depth 8 7/8" 9 1/2" 10.5"
Circle Cutout 11 3/8" 13 3/4" 16 9/16"