Helix DSP PRO MK2 Review: Archived but Still Capable

This Helix DSP PRO MK2 review comes with a catch: the processor is still capable on paper, but the manufacturer lists it as an archived model and a new retail price is not confirmed. It is worth considering only if a used or open-box unit sits well below the $1,299 price of its successor, the Helix DSP PRO MK3, which has twice the DSP power and adds features the MK2 lacks. Buyers who can pay for new hardware are safer with the successor.

The page covers what the MK2 offers, how its rated performance compares with that successor and two other rivals, and what to check before buying one second-hand.

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Helix DSP PRO MK2 design and build

The MK2 is a compact unit measuring 40 x 177 x 150 mm (H x W x D). Audiotec Fischer rates it at 9.6 to 18 V with a 510 mA current draw, which works out to 6.1 W at 12 V. Its 64-bit fixed-point DSP runs at 295 MHz, giving 1.2 billion MAC operations per second, and the converters are listed as Asahi Kasei 32-bit parts.

The manual says to mount it in a dry place with enough air circulation, not in a small closed box or near heat sources, and to check behind the mounting surface for wiring, brake lines or the fuel tank. A status LED shows the active setup and, if it flashes orange, that temperature protection has switched the remote output off.

Helix DSP PRO MK2 inputs, setup and features

The MK2 takes 8 speaker-level inputs, 8 RCA inputs, one optical input (12 to 96 kHz), one coaxial input (12 to 192 kHz) and a remote input, with 10 RCA outputs. Digital inputs accept stereo PCM only, not Dolby-coded streams. The speaker-level inputs use Helix's ADEP circuit, which the manufacturer says prevents the fault messages and lost functions some factory radios show when a processor is connected. With a radio that has BTL output stages, the processor can turn on from the speaker signal.

Setup has a hardware step. Input sensitivity is set with eight internal trim pots and jumpers, so the case has to be opened by removing five screws. Speaker-level inputs ship at 10 V and can be moved to 5 to 10 V or 10 to 20 V, RCA inputs ship at 4 V and span 2 to 4 V, and channels G and H can be switched to an AUX range of 250 to 500 mV. A clipping LED helps with adjusting each channel.

In software, each of the 10 channels is configured through the DSP PC-Tool over USB. Time alignment reaches 20 ms per channel, which is about 6.9 m of path difference at 343 m/s (computed). The page also lists an all-pass filter option, reverse time alignment and selectable D/A converter sound options. Two setups can be stored and switched from the unit's button. Power Save Mode switches the amplifier remote off after 60 seconds without signal and restarts it within a second of music returning.

The HEC slot accepts add-on modules such as Bluetooth streaming, USB audio, an extra optical input or an AUX input. The manual says to use only modules specified for the MK2, and retailers list separate HEC modules for the MK2 and its successor. Remote controls on the manufacturer's page include the URC.3, DIRECTOR and WIFI CONTROL. The successor adds an input signal analyzer, input EQ, TuneEQ auto-correction, sound effects such as RealCenter and a three-step sensitivity switch.

Rated performance of the MK2

Audiotec Fischer rates signal-to-noise at 110 dB for analog inputs and 116 dB for digital inputs (A-weighted), THD+N below 0.001 % and 0.0005 %, intermodulation distortion below 0.004 % and 0.002 %, crosstalk above 90 dB and a frequency response of 10 Hz to 44 kHz. Maximum output is 8 V. Our calculation from the rated figures puts 0.001 % THD+N at about 100 dB below the signal.

Against the newer models the electrical numbers are close. The Helix DSP PRO MK3 lists 111 dB and 116 dB with the same distortion figures, and the Helix DSP Ultra S lists 111 dB and 117 dB. The Audison bit One HD Virtuoso rates 104 dB and 110 dB with 0.004 % THD and a 4 V output, though the brands test differently. The MK2's gap to its successor is mainly in DSP power, tuning aids and input range, not in rated noise or distortion.

The manufacturer's page shows a 2017 Auto Sound Award badge and a Car Hifi magazine badge dated March 2017; both are manufacturer-listed. Our research found no independent lab measurements for this model.

Installing the Helix DSP PRO MK2 safely

Plan the channel map first, then mount the unit, run the power and remote leads, set input sensitivity with the amplifiers disconnected, make the basic DSP settings in software and only then connect the amplifiers. The manual recommends installation by an authorized Helix dealer to ensure full warranty coverage.

Safety and wiring notes

• Disconnect the battery negative before wiring, and fit a main fuse on the positive lead within 30 cm of the battery, rated for the whole system's current draw.
• Use only the supplied power connector and screw-terminal plugs, and wire of at least 1 mm2 (AWG 18) for power. Speaker-level input wires should be no thicker than 1 mm2.
• Never use the speaker-level and RCA inputs at the same time, because the manual warns this can damage the radio.
• Always turn amplifiers on from the processor's remote output, which is rated at 500 mA, and not from another signal.
• Digital sources send full level to the amplifiers, so fit a remote to control volume before playing music through the digital inputs.
• Identify factory speaker wires with a meter or wiring diagram before tapping them, never splice into airbag wiring, and keep volume at minimum on first start-up of an active system to protect tweeters.

Day to day, the unit runs unattended once configured. Anything beyond switching between the two stored setups needs the Windows software or an optional remote, so most buyers will want a professional tune or a Windows laptop and a measurement microphone.

How the MK2 compares with three rivals

Three alternatives were checked. Helix DSP PRO MK3 is the direct successor with the same channel count. Helix DSP Ultra S is the 12-output step up from the same maker. Audison bit One HD Virtuoso is a 13-output rival from another brand.

Model	Price	Outputs	Inputs	DSP	S/N analog / digital	Distortion	Max output	Max speaker-level input
Helix DSP PRO MK2	Not confirmed	10	8 speaker-level, 8 RCA, optical + coax	64-bit, 1.2 billion MAC/s, 96 kHz	110 / 116 dB	<0.001 % / <0.0005 % THD+N	8 V	20 V
Helix DSP PRO MK3	$1,299	10	8 speaker-level, 8 RCA, optical + coax	Dual 64-bit, 2.4 billion MAC/s, 96 kHz	111 / 116 dB	<0.001 % / <0.0005 % THD+N	8 V	32 V
Helix DSP Ultra S	Not confirmed	12	8 speaker-level, 8 RCA, optical + coax	64-bit, 96 kHz	111 / 117 dB	<0.0008 % / <0.0004 % THD+N	8 V	32 V
Audison bit One HD Virtuoso	Not confirmed	13 (9 in FIR mode)	12 speaker-level, 6 RCA + AUX pair, 2 optical	24-bit / 96 kHz floating point	104 / 110 dBA	0.004 % THD (1 kHz, 1 V out)	4 V	32 V

The MK2 is the only model here without a confirmed new price. Our calculation from the $1,299 price puts its successor at $129.90 per output, and that unit doubles the DSP power (1.2 to 2.4 billion MAC/s) and raises the speaker-level input ceiling from 20 V to 32 V. A used MK2 has to undercut that by a clear margin to make sense, because delivery and import fees can erase a small saving.

Who should buy it and who should skip it

Buy it if you find a used or open-box unit at a clear discount, you need 8 speaker-level inputs and 10 outputs, your installer already knows the DSP PC-Tool, and a factory radio's speaker diagnostics are the problem you want solved.

Skip it if you want a new unit with a manufacturer warranty, you need speaker-level inputs above 20 V for a high-power factory amplifier, you want auto-correction or sound effects, you want more than 10 outputs, or you do not have a Windows PC.

Helix DSP PRO MK2 availability and what to check

The price of the Helix DSP PRO MK2 is not confirmed. Audiotec Fischer files the MK2 under its product archive and names the MK3 as the successor. The current Helix processor range lists the NEXT DSP Ultra XT, DSP Ultra S, DSP PRO MK3, DSP.3S and DSP MINI MK2. Prices change often, so check the current listing.

Confirm the seller's condition description, return policy and any warranty, and that the USB cable and the supplied screw-terminal connectors are included, because the manual says to use only those connectors. Ask whether a HEC module is fitted and which model it is for. Check which DSP PC-Tool version supports the unit, since the MK2 page lists version 4. Budget for a remote to control digital-source volume, the optional Easy Plug Cable for factory radios, a Windows PC and professional tuning.

Helix DSP PRO MK2 final verdict and score

The MK2 earns 3.5 out of 5. It is a well-specified 10-output processor with strong rated noise and distortion figures and good factory-radio features, held back by its archived status, half the DSP power of its successor, internal sensitivity adjustment, a 20 V speaker-level ceiling and the missing confirmed price. The rubric weights are performance and function 40 %, features and usability 20 %, build quality and design 15 %, and value for the price 25 %. Our calculation gives a weighted total of 3.65, which rounds to the nearest half step: 3.5. Our research score is based on the rated figures and documented details above.

Criterion	Weight	Score	Basis
Performance and function	40 %	4.0	Rated figures close to its successor; no independent measurements
Features and usability	20 %	3.5	ADEP, HEC slot, Power Save; internal trim pots and no auto-tuning aids
Build quality and design	15 %	4.0	Compact, quality converters listed; durability data not confirmed
Value for the price	25 %	3.0	Archived, price not confirmed; a used saving can be small against the successor
Weighted total	100 %	3.65	Rounded to the nearest half step: 3.5

Sources and further reading

• Audiotec Fischer: HELIX DSP PRO MK2 product page and technical data
• HELIX DSP PRO MK2 instruction manual (PDF)
• Audiotec Fischer: HELIX DSP PRO MK3 specifications
• Audiotec Fischer: current HELIX processor range and model status
• Audiotec Fischer: HELIX DSP ULTRA S specifications
• Audison Virtuoso technical sheet (PDF)
• ResoNix Sound Solutions: DSP PRO MK3 listing and price