Hertz Active Subs

Want to enhance your listening with impressive sub-bass but unwilling to give up all of your luggage space or invest in a separate amplifier? Then, an active subwoofer could be the way to go.

Hertz Active Subs

Want to enhance your listening with impressive sub-bass but unwilling to give up all of your luggage space or invest in a separate amplifier? Then, an active subwoofer could be the way to go. Here, we feature two magnificent examples from Hertz.

In recent years, sub-bass has become better, more space efficient and easier to afford. Joining the Hertz line-up is a total makeover of a Hertz staple and a new design to help provide lovers of the deep with neat solutions.

First of all, we will look at the Hertz Dieci DBA 201F. This sealed, flat enclosure hosts an 8” driver with an impedance of just 0.4 ohm. The impedance is exceptionally low. Those of you who are used to buying subwoofers for a car will know that they tend to come in 4-ohm or 2-ohm versions. Careful impedance matching of amplifier and speaker helps to optimise power while keeping firm control of performance. With the introduction and development of class-D amplification, it is now possible to run amplifiers into a lower impedance without causing overheating or damage to the output stage. The result of this lower impedance matching means that a speaker and amplifier system can run much more efficiently and require far less power from the vehicle’s battery. Low power is good as it also reduces stress on cables and connectors.

The whole unit produces 440 watts of output power and draws a maximum of 15 amps from the vehicle’s supply. This is so low that power can be supplied from the vehicle via a removable plug rather than soldered or clamped in place by some binding post or nut and star washer arrangement. This means the whole assembly can be easily removed if space is needed temporarily for other things. The low power draw also makes this product highly suitable for use in EVs.

The enclosure itself is made from rigid plastic. Strengthening ribs are moulded into the case to quell any resonance. The whole assembly measures 345mm X 245mm X 79, making it suitable for under-seat mounting in many vehicles. Strong adhesive Velcro is provided to anchor the enclosure to the vehicle carpet. Four low-profile feet allow for screw-fitting to a board if preferred.

The DBA 201F can accept either pre-outs from a head unit or speaker outputs. The input sensitivity can be adjusted to ensure maximum input without distortion in both cases. Pre-out inputs can accept levels between 0.2 – 5 volts, while the speaker inputs can handle inputs from 1.2 – 30 volts. Left and right signals are summed within the subwoofer to create a single mono input.

The internal amplifier can be switched on by a conventional wired remote output from the head unit or via an autosensing function that powers the amplifier when a signal is detected on its inputs.

A whole host of functions are included, accessible by switches and controls on a panel on the side. These include the aforementioned sensitivity controls, a switch for the auto-sense function if using, but also a 180° phase switch, which may be required depending on mounting position. A control marked “Gain” sets input sensitivity while a 6 dB bass boost (@45Hz) is also included. A 24dB/octave Lo-Pass filter with an adjustable cutting corner (50 – 150 Hz) is also provided for precise adjustment.

A subsonic filter is built in. This filters frequencies below the audible range (15Hz). These frequencies can lead to high cone excursion and cause overheating if left unchecked.

Hertz Dieci DBA 201 shares all of the features of the DBA 201F. However, the 8” driver is supplemented by two passive radiators. These are like speakers but without the motor assembly. Their job is to vibrate in sympathy with air pressure changes in the cabinet due to the cone movement of the main driver. Passive radiators are common in small enclosures but can also be found in larger speakers. Some home Hi-fi speakers contain passive radiators, as do many small Bluetooth speakers. It is a tried and tested way to achieve low bass without using space-inefficient ported enclosures. The alternative would be to port the box, resulting in it having to be much bigger physically.

They work well in this wedge-shaped MDF box, which is built to sit in a luggage compartment. The overall dimensions are 291mm X 315.5mm X 264mm. The DAB 201 can also be easily removed when additional storage space is required.

Both products offer ideal solutions to the same problem and are now readily available from all FOUR MASTERs.