HEDD
TYPE 40 XTD
Extension module TYPE 40 System

The dedicated extension module
The TYPE 40 XTD is a dedicated, active, low-frequency extension module designed for the TYPE 40 Main. Depending on its configuration, it either increases low-frequency headroom and output or provides cardioid control over rearward bass radiation. It can also do both. While the Main remains a complete full-range reference, the XTD gives engineers greater control over how the system performs in their room. The XTD is designed for use with the TYPE 40 Main and is not a standalone product.
Studios can tailor the configuration to their acoustic and playback requirements with one to three XTD modules per channel, then expand the system as those needs change.
Each XTD module combines a 10¾-inch high-excursion woofer with a dedicated 700-watt Class D amplifier. There are four different operating modes that combine frontfire or cardioid operation with a ported or closed enclosure. All of these modes are integrated with the main through HEDD Lineariser® and HEDD CTRL.

Cardioid bass control
In cardioid mode, the XTD works with the main or frontfire XTD modules to reduce the amount of low-frequency energy behind the system by up to 10 decibels. This helps limit wall reflections behind the monitors that can distort the low end. A Cardioid Closed XTD and a full-range Main provide directional control from approximately 20 to 200 Hz. Cardioid Closed offers the widest frequency range of rear reduction. Cardioid Ported, when used with Frontfire Ported modules in mixed configurations, provides somewhat less rear reduction while retaining the efficiency of a ported system. Larger mixed configurations combine Frontfire output with Cardioid control; performance is determined by the arrangement and operating modes. For cardioid operation, the XTD is physically reversed to fire toward the rear.

Configurations and output
Select one to three XTD modules per channel based on the room's acoustic behavior, listening distance, and output requirements. Each XTD module can be configured with either a ported or closed enclosure.
For maximum output, all XTD modules can operate in frontfire ported mode, which increases the maximum SPL at 50 Hz by 6, 12, or 15 dB with one, two, or three modules, respectively, compared to the main module alone. Mixed frontfire/cardioid configurations balance output needs with rear radiation control. The main monitor remains in place in every configuration, allowing the system to expand as needs change.
Ported or Closed
Ported operation provides greater efficiency and maximum low-frequency output. Installing the supplied sealing panel converts the XTD to a closed enclosure, which provides more controlled low-frequency reproduction at the expense of maximum output. Select the matching Closed or Ported (CoP) setting in HEDD CTRL or on the back panel.
HEDD CTRL
HEDD CTRL allows you to manage the main and XTD modules from the listening position. After assigning the units and selecting their operating modes to match the physical setup, the software automatically applies the correct LF Range and Extension Quantity settings. Engineers can then manually adjust the room with a 12-band parametric equalizer at the group and individual speaker levels. There are presets for different workflows or listening positions. The free software supports systems of up to 250 speakers.
Features
- Dedicated active low-frequency extension for the TYPE 40 Main; one to three XTD modules per channel
- Cardioid rear-radiation reduction of up to approximately 10 dB, depending on mode and configuration
- 10¾-inch high-excursion woofer with dedicated 700 W Class D amplification
- Four operating modes: Frontfire Ported, Frontfire Closed, Cardioid Ported, and Cardioid Closed; sealing panel supplied for Closed operation
- Frequency response (-3 dB): 20–80 Hz, extending to 20–250 Hz in Cardioid operation with the Main
- Maximum SPL gain at 50 Hz with all XTDs in Frontfire Ported mode: +6 dB (one), +12 dB (two), or +15 dB (three) per channel, relative to the Main alone
- HEDD Lineariser® with ZERO PHASE, FLAT, and OFF modes
- HEDD CTRL over Ethernet with automatic LF Range and Extension Qty settings; 12-band PEQ for manual room correction at group and individual-speaker level, plus presets and firmware management
- Balanced analog XLR and AES/EBU digital inputs, both with Through connections
- Matching cabinet dimensions with the Main; side M10 mounting points; recommended system stand available separately
Specifications
Type | Dedicated active low-frequency extension module for the TYPE 40 Main |
System configuration | One TYPE 40 Main plus one to three TYPE 40 XTD modules per channel |
Driver | 10¾-inch Ultra-High Performance Subwoofer |
Amplification | Class D, 700 W |
Operating modes | Frontfire Ported / Frontfire Closed / Cardioid Ported / Cardioid Closed |
Acoustic principle | Selectable Ported or Closed; aluminium sealing panel supplied |
Mode selection | CoP control or HEDD CTRL; physical orientation and port state must match the selected mode |
Frequency response (-3 dB) | 20 Hz–80 Hz; extends to 20 Hz–250 Hz in Cardioid operation with the TYPE 40 Main |
Frontfire crossover | 80 Hz with the TYPE 40 Main in XTD mode |
Maximum SPL gain at 50 Hz, All Frontfire Ported | +6 dB (1 XTD) / +12 dB (2 XTDs) / +15 dB (3 XTDs) per channel, relative to the Main alone |
Maximum SPL gain at 50 Hz, All Frontfire Closed | No increase (1 XTD) / +6 dB (2 XTDs) / +9 dB (3 XTDs) per channel, relative to the Main alone |
Cardioid rear reduction | Up to approximately 10 dB in the rear hemisphere; effective frequency range varies by mode and configuration |
Single-XTD Cardioid range | Approximately 20 Hz–200 Hz with one Cardioid Closed XTD and the Main in FULLRANGE |
Kontrolle / Management | HEDD CTRL über Ethernet / RJ45 |
Mixed-system Cardioid range | Approximately 20 Hz–100 Hz in mixed Frontfire/Cardioid configurations |
Mixed-system Cardioid range | Approximately 20 Hz–100 Hz in mixed Frontfire/Cardioid configurations |
Self-noise at 10 cm | <20 dB SPL, A-weighted |
DSP integration | Internal processing at 96 kHz; HEDD Lineariser® with ZERO PHASE, FLAT, and OFF modes |
Lineariser delay | 2.3 ms OFF / 2.3 ms FLAT / 11.3 ms ZERO PHASE |
Analog input | Balanced XLR with Through; input impedance >20 kΩ |
Digital input | AES/EBU XLR with Through; accepted sample rates 44.1–192 kHz |
Maximum input level | +14.77 dBu at -4 dB input sensitivity |
Input gain / sensitivity | -10 / -4 / 0 / +4 dB |
Shelving filter | Adjustable level; corner frequency 40 / 80 / 120 / 160 / 200 Hz |
Extension Qty | 1 / 2 / 3; setting depends on the unit’s role in the configuration |
Control / management | HEDD CTRL via Ethernet / RJ45; 12-band PEQ at group and individual-speaker level |
Automatic standby | After 30 minutes of inactivity by default; timing adjustable in HEDD CTRL |
Power supply | 85–264 V, 50/60 Hz |
Power consumption | 20 W idle / 588 W full output / <0.5 W standby |
Cabinet / finish | MDF / satin black matte paint |
Mounting | Side M10 points; mounting hardware sold separately |
Recommended stand | Sound Anchors HEDD TYPE 40 System Stand, sold separately |
Dimensions (H × W × D) | 370 × 470 × 450 mm |
Weight | 27.5 kg per unit, plus 1.5 kg aluminium sealing panel |
Packaging (L × W × H) | 1,150 × 600 × 480 mm per pair; 79 kg gross |
Amplifier power is a peak rating. SPL gains are relative to the Main alone and apply only to the stated configurations. In mixed Frontfire/Cardioid configurations, all XTDs in a channel must be either Ported or Closed.

