M FOUR - Receiver Helix - Free user manual and instructions

Product Type	4-Channel Amplifier with Integrated Active Crossover
Brand	Helix
Model	M FOUR
Dimensions (H x W x D)	50 x 230 x 154 mm / 2.00 x 9.06 x 6.06 in
Power Supply Voltage	10.5 - 16 Volts (max. 5 sec. down to 6 Volts)
Output Power RMS @ 4 Ohms	4 x 100 Watts
Output Power RMS @ 2 Ohms	4 x 100 Watts
Output Power RMS Bridged @ 4 Ohms	2 x 200 Watts
Amplifier Technology	Class D
Inputs	4 x RCA / Cinch, 4 x Highlevel Speaker Input, 1 x Remote In
Input Sensitivity (RCA)	0.5 - 6 Volts
Input Sensitivity (Highlevel)	1.3 - 13 Volts
Frequency Response	10 Hz - 30,000 Hz
Highpass Filter Range	15 Hz - 4,000 Hz (adjustable)
Lowpass Filter Range	40 Hz - 4,000 Hz (adjustable)
Bandpass Filter Range	15 Hz - 4,000 Hz (adjustable)
Filter Slope	12 dB/Oct
Signal-to-Noise Ratio	98 dB (A-weighted)
Distortion (THD)	0.05%
Damping Factor	100
Protection Circuits	Overheating, Over/Undervoltage, Short-Circuit, False Connection
Additional Features	Active adjustable crossover, Input mode switch, Start-Stop capability, Highlevel input with auto turn-on, ADEP circuit
Fuse	2 x 30 A Maxi-fuse (APX)
Maintenance	Clean with a dry cloth; avoid moisture and solvents.
Safety Precautions	Disconnect battery negative terminal before installation; use correct fuse rating; ensure proper ventilation; do not expose to water.

Frequently Asked Questions - M FOUR Helix

How do I connect the amplifier to my car radio?

You can connect via low-level RCA inputs or high-level speaker inputs. For RCA, use the Line Input jacks. For high-level, use the pluggable screw-terminal connector to the Highlevel Input. Never use both simultaneously. If using high-level, the remote input (REM) is not needed due to auto turn-on.

What is the ADEP circuit?

The ADEP (Advanced Diagnostics Error Protection) circuit prevents error messages and loss of features (like fader) when connecting to modern OE radios. It ensures the amplifier is detected as a speaker without loading the outputs.

How do I adjust the input sensitivity?

Use the Input Level controls for channel pairs A/B and C/D. For RCA inputs, range is 0.5-6V; for high-level, 1.3-13V. Turn the control from min CCW to 9 o'clock for standard radio high-level (approx 9V). This is not a volume control.

What does the Protect LED indicate?

A red LED indicates a malfunction, such as overheating, over/undervoltage, short-circuit, or false connection. The amplifier shuts off. Check for wiring errors, speaker impedance (min 2 ohms per channel, 4 ohms bridged), and ventilation.

Can I use high-level and low-level inputs at the same time?

No, it is strictly forbidden to use both simultaneously. Doing so may cause severe damage to the low-level outputs of your head unit.

How do I set up a bandpass filter?

Set the X-Over switch for channel pair C/D to LPF (lowpass). Then adjust the highpass filter (control 4) and lowpass filter (control 7) to create a bandpass between 15 Hz and 4,000 Hz. Ensure at least two octaves separation between the two frequencies to avoid gain loss.

What is the minimum speaker impedance?

Minimum impedance per channel is 2 Ohms. In bridged mode (channels C/D bridged), minimum impedance is 4 Ohms. Lower impedance will activate protection.

How do I bridge channels for a subwoofer?

Use the Bridged speaker output terminals for channels C and D. Connect the subwoofer positive to the left (+) terminal and negative to the right (-) terminal. Set the X-Over switch to LPF and adjust lowpass filter accordingly.

Does the amplifier support Start-Stop vehicles?

Yes, the HELIX M FOUR has Start-Stop capability. Its switched power supply ensures operation even when battery voltage drops to 6 Volts during engine crank.

How do I turn on the amplifier when using high-level inputs?

When using high-level inputs, the amplifier automatically turns on once a speaker signal is applied. The Remote In (REM) does not need to be connected. This works with BTL output stages.

USER MANUAL M FOUR Helix

4-channel amplifier with integrated active

crossover

① Line Input

⑧ Speaker Output

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Congratulations on your purchase of this innovative and high-qual ity HELIX product.

The HELIX M FOUR highlights best quality, excellent manufacturing and state-of-the-art technology. Thanks to more than 30 years of experience in research and development of audio products this amplifier generation sets new standards.

We wish you many hours of enjoyment with your new HELIX amplifier.

Yours, AUDIOTEC FISCHER Team

General instructions

General installation instructions for HELIX components

To prevent damage to the unit and possible injury, read this manual carefully and follow all installation instructions. This product has been checked for proper function prior to shipping and is guaranteed against manufacturing defects.

Before starting your installation, disconnect the battery's negative terminal to prevent damage to the unit, fire and/or risk of injury. For a proper performance and to ensure full warranty coverage, we strongly recommend to get this product installed by an authorized HELIX dealer.

Install your M FOUR in a dry location with sufficient air circulation for proper cooling of the equipment. The amplifier should be secured to a solid mounting surface using proper mounting hardware. Before mounting, carefully examine the area around and behind the proposed installation location to ensure that there are no electrical cables or components, hydraulic brake lines or any part of the fuel tank located behind the mounting surface. Failure to do so may result in unpredictable damage to these components and possible costly repairs to the vehicle.

General instruction for connecting the HELIX M FOUR amplifier

The HELIX M FOUR amplifier may only be installed in vehicles which have a 12 Volts negative terminal connected to the chassis ground. Any other system could cause damage to the amplifier and the electrical system of the vehicle.

The positive cable from the battery for the complete system should be provided with a main fuse at a distance of max. 30 cm from the battery. The value of the fuse is calculated from the maximum total current input of the car audio system.

Use only suitable cables with sufficient cable cross-section for the connection of the HELIX M FOUR. The fuses may only be replaced by identically rated fuses (2 x 30 A) to avoid damage of the amplifier.

Prior to installation, plan the wire routing to avoid any possible damage to the wire harness. All cabling should be protected against possible crushing or pinching hazards. Also avoid routing cables close to potential noise sources such as electric motors, high power accessories and other vehicle harnesses.

① Line Input

RCA inputs for connecting lowlevel line signals.

② Highlevel Input

Highlevel speaker inputs for connecting a factory radio or an aftermarket radio without lowlevel line outputs.

③ Input Level

Control for adjusting the input sensitivity of the lowlevel Line and Highlevel Inputs for the individual stereo signals.

④ HPF

Control for adjusting the highpass filter from 15 Hz to 4,000 Hz.

⑤ X-Over

Switch for activating the filters for each channelpair.

⑥ Input Mode

Switch to route input signals to respective amplifier channels.

⑦ LPF

Control for adjusting the lowpass filter of the channels C and D from 40 Hz to 4,000 Hz.

⑧ Speaker Output

Speaker outputs for connecting speaker systems.

⑨ Power & Protect LED

This LED indicates the operating mode of the amplifier.

⑩ +12 V

Connector for the +12 V power cable of the positive terminal of the battery.

11 REM

Connector for the remote cable.

12 GND

Connector for the ground cable (negative terminal of the battery or metal body of the vehicle).

① Line Input

4-channel lowlevel line input to connect signal sources such as head units / radios / DSPs.

Important: It is strictly forbidden to use the High-level Input and lowlevel Line Input at the same time. This may cause severe damage to the lowlevel line outputs of your head unit / car radio.

② Highlevel Input

4-channel highlevel loudspeaker input to connect the amplifier directly to the loudspeaker outputs of OEM / aftermarket radios that do not have any low-level line outputs.

The Highlevel Input is equipped with our proprietary ADEP circuit (Advanced Diagnostics Error Protection) which ensures that the car radio detects the amplifier as a speaker and thus neither any function of the radio (e.g. fader) will be deactivated nor any error log in the CPU of the car will be created. If this input is used the remote input (REM) does not need to be connected as the amplifier will automatically turn on once a loudspeaker signal is applied.

Attention: Solely use the pluggable screw-terminal for the highlevel connector which is included in delivery!

Important: It is strictly forbidden to use the High-level Input and lowlevel Line Input at the same time. This may cause severe damage to the lowlevel line outputs of your car radio.

③ Input Level

These controls are used to adapt the input sensitivity of the channel pairs A/B and C/D to the output voltage of the connected signal source.

This is not a volume control, it's only for adjusting the amplifier gain. The control range of the RCA / Line Input (lowlevel) is 0.5 - 6 Volts and 1.3 - 13 Volts for the Highlevel Input. If the Highlevel Input is used in combination with a standard car radio we recommend an input sensitivity of roughly 9 Volts. For this purpose, turn the control from max. CCW position to 9 o'clock position.

④ HPF

This control is used to adjust the crossover frequency of the highpass filter from 15 Hz to 4,000 Hz. This control is activated if the X-Over switch of the specific channel pair is set to HPF (highpass filter). On channel pair C/D it is also activated in LPF / Bandpass and its adjustment is mandatory.

⑤ X-Over

This switch allows to set the internal crossover to highpass, fullrange or lowpass / bandpass mode. The filter options depend on the channel pair.

Channel pair A/B: Highpass filter or fullrange If this X-Over switch is set to HPF (highpass filter) the crossover frequency for the highpass can be adjusted with control 4 of the channel pair A/B.

At switch position FULL (fullrange) the crossover is bypassed.

Channel pair C/D: Highpass filter, fullrange or low-pass filter / bandpass.

If this X-Over switch is set to HPF (highpass filter) the crossover frequency for the highpass can be adjusted with control 4 of the channel pair C/D. At switch position FULL (fullrange) the crossover is bypassed.

At switch position LPF (lowpass filter / bandpass) the highpass is always active. That means a bandpass is created in any case.

By adjusting the highpass (control 4) and lowpass (control 7) filter any bandpass between 15 Hz and 4,000 Hz can be realized.

Caution: To avoid a loss of gain make sure that the crossover frequencies of the high- and lowpass filters do have an interval of at least two octaves when generating a bandpass.

That means if the lowpass signal is adjusted to

Initial start-up and functions

320 Hz the highpass should be adjusted to 80 Hz or less (one octave = doubled frequency or halved frequency). If a subwoofer is connected we recommend to use the highpass control (control 4) as variable subsonic / low-frequency highpass filter or turn it counterclockwise to 15 Hz to get a subsonic filter.

⑥ Input Mode

This switch is used to route the input signals to the respective amplifier channels.

4-channel mode: If the head unit / car radio provides two stereo outputs (front left / right, rear left / right), all four signal inputs of the amplifier are supplied with the corresponding output signals of the head unit / car radio.

2-channel mode: If the head unit / car radio only provides one stereo output, all amplifier channels are supplied with this signal. This means, that only the RCA / highlevel inputs of the channels A and B need to be connected. In this mode the input signal of channel A is routed to channel C and channel B is routed to channel D. Please consider that the fader and balance control of the head unit have the same effect on channels A and C and respectively B and D.

⑦ LPF

This control is used to adjust the crossover frequency of the lowpass filter of the channels C and D from 40 Hz to 4,000 Hz.

⑧ Speaker Output

Speaker outputs of the channels A - D to connect speaker systems. The impedance per channel must not be lower than 2 Ohms (4 Ohms in bridged mode).

⑨ Power & Protect LED

The power and protect LED indicates the operating mode of the amplifier.

Green: The amplifier is ready for operation.

Red: A malfunction has occurred. A malfunction may have different causes as the HELIX M FOUR is equipped with several protection circuits. These protections shut off the amplifier in case of overheating, over- and undervoltage, short-circuit on loudspeakers and false connection. Please check for connecting failures such as short-circuits, wrong connections, wrong adjustments and over temperature. If the amplifier does not turn on it is defective and has to be sent to your local authorized dealer for repair service. A detailed description of the malfunction and the purchase receipt has to be attached.

⑩ +12 V

Connect the +12 V power cable to the positive terminal of the battery. Recommended cross section: min. 10 mm ^4 / AWG 8.

⑪ REM

The remote lead should be connected to the remote output / automatic antenna (aerial positive) output of the head unit / car radio. This is only activated if the head unit / car radio is switched on. Thus the amplifier is switched on and off together with the head unit / car radio. This input needn't to be assigned if the Highlevel Input is used.

12 GND

The ground cable should be connected to a common ground reference point (this is located where the negative terminal of the battery is grounded to the metal body of the vehicle) or to a prepared metal location on the vehicle chassis i.e. an area which has been cleaned of all paint residues. Recommended cross section: min. 10 mm ^2 / AWG 8.

Connection of HELIX M FOUR to the head unit / car radio:

Caution: Carrying out the following steps will require special tools and technical knowledge. In order to avoid connection mistakes and / or damage, ask your dealer for assistance if you have any questions and follow all instructions in this manual (see page 11). It is recommended that this unit will be installed by an authorized HELIX dealer.

1. Connecting the lowlevel line inputs

Use the correct cable (RCA / Cinch cable) to connect these inputs to the lowlevel line outputs of your car radio. It is not mandatory to use all lowlevel line inputs. If only two channels will be connected we recommend to use the channels A and B and set the Input Mode switch to "2CH". When all channels will be used please choose switch position "4CH" (see page 14, item 6; Input Mode). The automatic turn-on circuit does not work when using the lowlevel line inputs. In this case the remote input (REM) has to be connected to activate the HELIX M FOUR.

Important: It is strictly forbidden to use the Highlevel Input and lowlevel Line Input at the same time. This may cause severe damage to the lowlevel line outputs of your car radio.

2. Connecting the highlevel speaker inputs

The highlevel loudspeaker inputs can be connected directly to the loudspeaker outputs of an OEM or aftermarket radio using appropriate cables (loudspeaker cables with 1 mm^2 / AWG 18 max. ).

We recommend the following channel assignment:

Channel A = Front left

Channel B = Front right

Channel C = Rear left

Channel D = Rear right

Actually it is not mandatory to use all highlevel speaker inputs. If only two channels will be connected we recommend to use the channels A and B and set the Input Mode switch to "2CH". When all channels will be used please choose switch position "4CH" (see page 14, item 6; Input Mode).

Make sure that the polarity is correct. If one or more connections have reversed polarity it may affect the performance of the amplifier. If this input is used the remote input (REM) does not need to be connected as the amplifier will automatically turn on once a loudspeaker signal is applied.

3. Adjustment of the input sensitivity

Attention: It is mandatory to properly adapt the input sensitivity of the M FOUR to the signal source in order to avoid damage to the amplifier.

If you want to change the input sensitivity of the channel pairs use the two Input Level controls (see page 13, item 3; Input Level). The settings of the controls affect both the lowlevel line inputs (Line Input) and the highlevel speaker inputs (Highlevel Input)! If the Highlevel Input is used in combination with a standard car radio we recommend an input sensitivity of roughly 9 Volts. For this purpose, turn the control from max. CCW position to 9 o'clock position.

4. Connection to power supply

Make sure to disconnect the battery before installing the HELIX M FOUR!

Connect the +12 V power cable to the positive terminal of the battery. The positive wire from the battery to the amplifier power terminals needs to have an inline fuse at a distance of less than 12 inches (30 cm) from the battery. The value of the fuse is calculated from the maximum total current draw of the whole car audio system (M FOUR = max. 60 A RMS at 12 V power supply). If your power wires are short (less than 1 m / 40") then a wire gauge of 10 mm² / AWG 8 will be sufficient. In all other cases we strongly recommend gauges of 16 - 25 mm² / AWG 6 - 4!

The ground cable (same gauge as the +12 V wire) should be connected to a common ground reference point (this is located where the negative terminal of the battery is grounded to the metal body of the vehicle), or to a prepared metal location on the vehicle chassis, i.e. an area which has been cleaned of all paint residues.

5. Connecting the remote input

The remote input (REM) has to be connected

Installation

to the radio remote output if the amplifiers low-level line inputs are used as signal inputs. We do not recommend controlling the remote input via the ignition switch to avoid pop noise during turn on/off.

If the Highlevel Input is used this input does not need to be connected as long as the car radio has BTL output stages.

6. Connecting the loudspeaker outputs

The loudspeaker outputs can be connected directly to the wires of the loudspeakers. Never connect any of the loudspeaker cables to the chassis ground as this will damage your amplifier and your speakers.

Ensure that the loudspeakers are correctly connected (in phase), i.e. plus to plus and minus to minus. Exchanging plus and minus causes a total loss of bass reproduction. The positive terminal is indicated on most speakers. The impedance of each channel must not be less than 2 Ohms (4 Ohms in bridged mode), otherwise the amplifier protection will be activated. Examples for speaker configurations can be found on page 18.

Unique Features of the HELIX M FOUR

Smart highlevel input

The latest generation of OE car radios incorporates sophisticated possibilities of diagnosing the connected speakers. If a common amplifier will be hooked up failure messages and loss of specific features (e.g. fader function) quite often appear - but not with the M FOUR.

The new ADEP circuit (Advanced Diagnostics Error Protection) avoids all these problems without loading the speaker outputs of the OE radio during high volumes unnecessarily.

Start-Stop capability

The switched power supply of the HELIX M FOUR assures operation even if the battery's voltage drops down to 6 Volts during engine crank.

Examples for speaker configurations

4-channel
Component system + coaxial system

Channel A/B Highpass filte

Channel C/D Highpass filter

4-channel
2-way fully active operation

Channel A/B Highpass filter

Channel C/D Bandpass

3-channel
Component system + subwoofer

Channel A/B Highpass filter

Channel C/D Bandpass

Note: The values listed here are empirical values that have been approved as useful in practice. Depending on the size of the loudspeaker we recommend the following highpass filter settings: ca. 50 Hz for 6.5"/16.5 cm LS; ca. 70 Hz for 5.25"/13 cm LS; ca. 100 Hz for 4"/10 cm LS

Technical Data

Output power RMS / max.

- @ 4 Ohms .... 4 x 100 / 200 Watts

- @ 2 Ohms 4 x 100 / 200 Watts

- bridged @ 4 Ohms 2 x 200 / 400 Watts

Amplifier technology .... Class D

Inputs.... 4 x RCA / Cinch

4 x Highlevel speaker input

1 x Remote In

Input sensitivity.... RCA / Cinch 0.5 - 6 Volts

Highlevel 1.3 - 13 Volts

Input impedance RCA / Cinch 20 kOhms

Input impedance highlevel.... 13 Ohms

Outputs....4 x Speaker output

Frequency response....10 Hz - 30,000 Hz

Highpass.... 15 Hz - 4,000 Hz adjustable

Lowpass 40 Hz - 4,000 Hz adjustable

Bandpass.... 15 Hz - 4,000 Hz adjustable

Slope high- / lowpass 12 dB/Oct.

Signal-to-noise ratio analog input....98 dB (A-weighted)

Distortion (THD)....0.05%

Damping factor 100

Operating voltage 10.5 - 16 Volts (max. 5 sec. down to 6 Volts)

Idle current.... 1,100 mA

Fuse....2 x 30 A Maxi-fuse (APX)

Additional features....Active, adjustable crossover, input mode switch, Start-Stop capability, highlevel input with automatic turn on function and Advanced Diagnostics Error Protection (ADEP)

Dimensions (H x W x D) 50 x 230 x 154 mm / 2.00 x 9.06 x 6.06"

Warranty Disclaimer

The limited warranty comply with legal regulations. Failures or damages caused by overload or improper use are not covered by the warranty. Please return the defective product only with a valid proof of purchase and a detailed malfunction description. Technical specifications are subject to change!

Errors are reserved! For damages on the vehicle and the device, caused by handling errors of the device, we can't assume liability. These devices are certified for the use in vehicles within the European Community (EC).

AUDIOTEC

FISCHER