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Product features
HELIX ISM 400.2DSP: 2-Channel Subwoofer Amplifier Module with Integrated DSP
The HELIX ISM 400.2DSP is a 2-channel subwoofer amplifier module with a built-in 1-channel DSP (digital signal processor), delivering up to 460W RMS at 2 x 2 ohms. It's built for adding a proper subwoofer to a factory sound system without ripping the whole thing apart. Compact, efficient, and EV ready, it fits neatly into modern vehicles including hybrids and electric cars.
Product overview
The ISM 400.2DSP is built for one job: adding a high quality subwoofer to a car that already has a factory sound system. Rather than replacing the whole setup, this module taps into the existing system and adds amplification plus digital tuning for the sub. It uses Class HD amplifier technology, a design that blends Class H and Class D principles so the internal supply voltage adjusts constantly to match the signal. This keeps heat down and efficiency up, which is why the unit can stay so compact. The DSP side runs on a 64 bit fixed point processor paired with high quality AD/DA converters (the chips that turn analogue signal into digital and back), giving clean, accurate bass processing. A heavy duty stereo highlevel input accepts up to 32V RMS, which means it can safely read the speaker-level signal straight from an OEM amplifier, something many basic amplifiers can't do without extra gear.
Features and benefits
Up to 460W RMS output, strong bass from a small box: at 2 x 2 ohms the ISM 400.2DSP can push up to 460W RMS, giving you real headroom to drive a proper subwoofer without the amp running out of puff.
Built-in 1-channel DSP, tuned bass integration: the onboard digital signal processor lets you shape how the subwoofer blends with the factory speakers, adjusting for where it sits in the car and the sound you're after. You'll need the DSP PC-Tool 6 software and some patience to get the most from it, so it's not a plug and forget install.
Heavy duty highlevel input up to 32V RMS, safe OEM signal pickup: many factory amplified systems push high signal voltages that a basic amp can't handle safely. This input is built to take that voltage without distortion or damage.
ADEP.3 smart input circuit, trouble free OEM integration: modern factory head units actively monitor connected speakers and can throw error codes or disable features like fader if a standard amp is wired in wrong. ADEP.3 is designed to avoid tripping those checks.
Class HD amplifier technology, efficient and compact: this design adjusts the internal supply voltage to match the music signal, cutting wasted heat so the amp stays small and runs cooler than a standard design pushing similar power.
DirectDSP switch, bypass option for external processors: if you've already got a separate DSP in your system, this switch sends the signal straight to the power stage untouched, so the ISM just works as a dedicated subwoofer amp.
EV Ready power supply, works in hybrids and electric vehicles: the extended operating voltage range down to 6V for short periods and up to 18V means it copes with the different electrical systems found in modern EVs and hybrids, not just standard petrol cars.
Signal sensing auto turn-on: the module switches on when it detects a music signal, so it works reliably even with factory amps that don't provide a dedicated remote turn-on wire.
IMPACT enclosure subwoofer compatibility: it can directly power certain passive 2 x 2 ohm IMPACT enclosure subwoofers by swapping the connection terminal, turning a passive box into an active one.
What's in the box
- 1 x HELIX ISM 400.2DSP subwoofer amplifier module
- 3 x Connection cable
- 1 x USB cable
- 1 x Fuse
- 1 x Mounting material
- 1 x Instruction manual
Technical specs
| Specification | Detail |
|---|---|
| Power RMS at 4 ohms | 2 x 130 watts |
| Power RMS at 2 ohms | 2 x 200 watts |
| Max. output power | Up to 460 watts RMS at 2 x 2 ohms |
| Amplifier technology | Class HD |
| Inputs | 2 x RCA, 2 x highlevel speaker input |
| Input sensitivity | RCA: 0.4 to 4 volts or 0.8 to 8 volts; Highlevel: 1.6 to 16 volts or 3.2 to 32 volts |
| Input impedance | RCA: 47 kOhms; Highlevel: 9 to 33 ohms |
| Outputs | 2 x speaker output, 1 x AISA signal output |
| Frequency response | 10 Hz to 20,000 Hz |
| DSP resolution | 64 bit |
| DSP power | 1 x 295 MHz (1.2 billion MAC operations per second) |
| Sampling rate | 48 kHz |
| DSP type | 1 x audio signal processor |
| Signal converters | A/D: BurrBrown 32 bit; D/A: AKM 32 bit |
| Signal to noise ratio | 102 dB (A weighted) at full power |
| Distortion (THD at 50 Hz, 1W into 4 ohms) | Less than 0.005% |
| Distortion (THD+N at 50 Hz, 1W into 4 ohms) | Less than 0.015% |
| Damping factor | 85 |
| Operating voltage | 10.5 to 18 volts (max 5 seconds down to 6 volts) |
| Power rating | DC 12V, 45A max |
| Idle current | 260 mA |
| Operating temperature range | Minus 40°C to plus 70°C |
| Fuse | 1 x 40A LP Mini fuse (APS) |
| Additional features | Start-Stop capability, clipping LED, DirectDSP switch, Smart Control Port, 32 bit CoProcessor, ground lift switch, highlevel input with automatic turn on function |
| Dimensions (H x W x D) | 54 x 231 x 105 mm (2.13 x 9.09 x 4.13 inches) |
Compatible with
The ISM 400.2DSP is compatible with the following passive 2 x 2 ohm IMPACT enclosure subwoofers, which can be converted to active using this module by replacing the connection terminal:
- IK ES10.1-DVC2 MK2
- IK E8.1-DVC2 MK2
It is also suitable as a base for custom built active subwoofer solutions.
Frequently asked questions
Can the ISM 400.2DSP work with my car's factory sound system?
Yes, it's designed specifically for that. The stereo highlevel input accepts up to 32V RMS, so it can safely read the signal straight from most factory amplifiers, and the ADEP.3 circuit helps it integrate without tripping factory fault checks.
Will this work in my hybrid or electric vehicle?
Yes, it's built as EV Ready with a Start-Stop capable power supply that handles voltage down to 6V for short periods and operates up to 18V, suiting the electrical behaviour of modern hybrid and EV platforms.
How much power does it actually put out?
It delivers 2 x 130W RMS at 4 ohms, 2 x 200W RMS at 2 ohms, and up to 460W RMS maximum at 2 x 2 ohms.
Do I need special software to tune it?
Yes, the DSP functions are configured using DSP PC-Tool 6 software via the included USB cable. This gives you control over equalisation, bass tuning, and other DSP features.
What's included in the box?
You get the ISM 400.2DSP module, 3 connection cables, a USB cable, a fuse, mounting material, and an instruction manual. For anything else, please contact us.
DSP features
| Feature | Detail |
|---|---|
| TuneEQ | Automated frequency response correction using a single measurement per channel or channel pair with a suitable measurement microphone, adjusting the parametric equaliser to match a reference curve. |
| Augmented Bass Processing | Combines Dynamic Bass Enhancement and SubXpander to boost deep bass and sound pressure, with an option to add subharmonic tones between 50 and 100 Hz for a deeper bass character. |
| DirectDSP | Routes the input signal straight to the power stage without DSP processing, for use when an external DSP already handles signal processing. |
| Power Save Mode | Switches off the internal amplifier stages when no music signal is detected for a set time, returning to normal operation within about 2 seconds once a signal is detected again. The delay can be adjusted or switched off in the DSP PC-Tool software. |
| ACO (Advanced 32 Bit CoProcessor) | Handles control and communication tasks, enabling fast system startup and quick switching between up to ten sound setups, plus features like AISA, DLC, and RTC. |
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