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Helix P-DSP

Programmable 8-channel digital signal processor

Item #: 975PDSP

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Original Price: $699.99

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Everything is under control

If you're an ultimate tweaker who's crazy about sound quality, then Helix's P-DSP processor will be a welcome addition to your system. After downloading the application and software from Helix, you plug your PC or laptop into the P-DSP's USB port. A detailed control panel will appear on your computer screen that lets you set virtually every tunable audio parameter to achieve the highest musical fidelity possible in your car. The visual display shows the resulting sound curve of each setting, so you'll know for sure how your adjustments are affecting audio output.

P-DSP tuning screen

The main control panel for the P-DSP, as it appears on your computer's screen

Switcher, EQ, time alignment, and more

The P-DSP processor accepts up to six inputs, which you can assign to up to eight output channels, perfect if you're running separate tweeters, mids, woofers, and subs. Each channel has its own output volume and a 30-band graphic equalizer that gives you incredible control over the sound. The EQ section features a fine tuning adjustment that lets you get in between the preset bands to smooth out any rough spots. The time alignment feature lets you correct for each speaker's placement in your car, so the sound from each speaker arrives at your listening position at the same time.

An insane filter section

You can configure almost any type of high-pass and low-pass filter on each channel. Not only can you adjust a crossover's frequency, but you can also choose the slope, its "filter characteristics" (see bullets), and adjust its "Q-factor," which adds a bump at the crossover point for certain settings. Filters and EQ can be set separately for each channel, or channels can be linked together for common settings.

Helix P-DSP

Save your settings

Don't worry, you don't have to drive around with your computer plugged in. You simply download your settings to the P-DSP processor, after saving them on your laptop. The P-DSP can store two settings at once, so you can toggle between them to see which sounds better. You can also use an optional microSD memory card to store and transfer processor settings.

Also works with Helix vehicle-specific Plug and Play wiring

The P-DSP can also serve as a digital processor in a Helix Plug and Play factory upgrade system. You use an EPC5 Easy Plug Cable and a Helix vehicle-specific adapter harness to plug your P-DSP directly into your vehicle's stereo to get its input signal, with no wire-cutting or splicing necessary.

Product Highlights:

  • digital signal processor
  • DSP settings and adjustmenets made via laptop or PC through USB port
  • download DSP PC-Tool Software from
  • 6 assignable inputs
  • inputs: 6 RCA preamp, 4 speaker-level, 1 optical SPDIF
  • 8 preamp outputs (4 volts)
  • channel settings can be separate or linked together
  • time alignment in 7 mm increments
  • 30-band graphic EQ with fine tuning
  • 1-band parametric EQ
  • adjustable high- and low-pass filters (20-20,480 Hz)
  • selectable slopes (6, 12, 18, 24, 30 dB/octave)
  • selectable filter characteristics
    • Butterworth: sharp transition, suitable for most applications
    • Bessel: gradual transition, suitable for smooth speakers, but not subs
    • Linkwitz: recommended for high-end speakers only, not subs
    • Chebyshev: very sharp transition, useful as high-pass for tweeters or low-pass for subs
    • Self-Define: selectable Q-Factor, 12 dB/octave slope only
  • adjustable Q-Factor in Self-Define mode (0.2-2.0) increases signal at crossover point
  • phase adjustment: switchable 0/180 degrees on front and rear channels, adjustable 0 to 360 degrees on sub channels in 22.5-degree increments
  • includes 57" USB cable
  • optional microSD memory card for saving and applying settings (sold separately)
  • plug and play input from select factory radios with EPC5 Easy Plug Cable and a Helix vehicle-specific harness (sold separately)
  • dimensions: 5-15/16"W x 1-11/16"H x 6-15/16"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

Helix P-DSP Reviews

Hands-on research

What's in the box?

Download owner's manual

  • P DSP digital signal processor
  • 19" Power/ Ground/ Remote input cable
  • 19" Remote output cable
  • 57" USB cable (USB Type A connector on one end and mini-USB Version 2.0 connector on the other)
  • Four 3/4" Self-tapping screws
  • Instruction manual (German/ English)

Product Research


Overview: The Helix P-DSP is a digital signal processor, programmed with your computer using the Helix PC-Tool software (downloaded from their web site). This allows you to upgrade your vehicle's factory or aftermarket sound in conjunction with aftermarket amplifiers, while leaving all of your factory or aftermarket equipment and controls intact.


  • Left Side:
    • Line Input: six RCA inputs, labeled A to F; each can be assigned to any combination of the eight line output channels, or marked Not Used
    • Speaker Input: Molex plug with four speaker level input channels (harness not included); can be used with the Helix Easy Plug Cable (item number 975EPC5, sold separately) and vehicle specific harnesses
    • Optical Input: Toslink input; compatible with 6 kHz to 192 kHz sampling frequencies
    • Power Input:
      • +12V: constant 12 volt power source
      • Ground: chassis ground
      • Remote-in: remote turn-on; not needed when using the speaker level inputs
      • Remote-out: 12 volt trigger to turn amplifiers on
  • Right Side:
    • USB: connect to computer using the included USB cable; P-DSP operating software updates are downloaded and DSP settings are adjusted through the USB port
    • Micro SD: P-DSP operating software updates and complete DSP settings files can be downloaded using the MicroSD card slot
    • Control Input: multifunction input for possible future Helix accessories
    • Line Outputs: eight RCA inputs, labeled A to H

Controls: All the controls are on the Helix PC-Tool software, downloaded to your computer from their web site:

  • Channel Configuration: Any combination of the six input channels can be used, so if only two inputs are available, they can still be routed to all eight outputs. Each output can be programmed as any input, or combination of inputs. (For example, a subwoofer output might have left and right/front and rear inputs routed to it, so it combines the left and right channels and is not affected by the fader.) Outputs A through F can be defined as any channel (left, right, front, rear, center) and set to full range, tweeter, midrange, woofer, or rear fill. Output G has the same options and adds subwoofer. Output H can only be designated as a subwoofer output. When an input or output is not used, it is set to Not Used.
  • Crossover: The crossovers are set for each channel individually, or multiple channels can be linked together and adjusted simultaneously (left and right, front and rear, etc.). Each channel has high pass and low pass crossovers, either or both can be bypassed. There are four settings for each crossover:
    • Frequency: The crossover points for each channel vary by how the channel is defined:
      • Full Range: adjustable from 20 Hz to 20.480 kHz in 1/12 octave increments
      • Tweeter: adjustable from 20 Hz to 20.480 kHz in 1/12 octave increments
      • Midrange: adjustable from 20 Hz to 20.480 kHz in 1/12 octave increments
      • Woofer: adjustable from 20 Hz to 20.480 kHz in 1/12 octave increments
      • Subwoofer: high pass (subsonic) adjustable from 20 to 100 Hz, low pass adjustable from 20 to 300 Hz, both in 1 Hz increments
    • Filter Characteristics: Different crossover types exhibit different sonic characteristics:
      • Butterworth: regular impulse behavior, sharp transition, 3 dB gain in the crossover frequency band, suitable for almost all applications
      • Bessel: very good impulse behavior, very gradual transition (drivers must have smooth frequency response outside the frequency band range), less than 1 dB gain in the crossover frequency band, only practical with very high quality speakers, not recommended for use with subwoofers
      • Linkwitz: very good impulse behavior, no gain at the crossover frequency, only practical with very high quality speakers, not recommended for use with subwoofers
      • Chebyshev: very sharp transition, poor impulse behavior, output exhibits 1 dB ripple, only recommended for a subwoofer or tweeter operating near the resonant frequency
      • Self Defined: useful as high pass (subsonic) in ported subwoofer systems, slope fixed at 12 dB/octave, Q value adjustable from 0.5 to 2.0
    • Slope: the crossover slopes are selectable; zero (bypassed), 6 dB/octave, 12 dB/octave, 18 dB/octave, 24 dB/octave, and 30 dB/octave (Linkwitz is limited to zero, 12 dB/octave, and 24 dB/octave; Self Defined is fixed at 12 dB/octave)
    • Q Factor: using the Self Defined filter characteristic setting, the Q factor can be adjusted from 0.5 to 2.0 in 0.1 increments
  • Output Level: The output levels are independently adjustable for each of the eight output channels. The range is +5 dB to -60 dB (1 dB steps from +5 dB to -10 dB, 2 dB steps from -10 dB to -30 dB, and 6 dB steps from -30 dB to -60 dB).
  • Phase: The phase of each output channel is independently adjustable. The subwoofer outputs are adjustable from 0° to 360° in 22.5° steps, all other outputs can be sit to 0° or 180°.
  • Time Alignment: The distance from the listener (for one position in the car) to the speaker connected to each channel is independently adjustable from zero to 353.5cm (approximately 12 feet) in 7mm (0.28") increments.
  • Equalizer: Each output channel has its own 30 band (1/3 octave) equalizer (10 band for channels defined as subwoofer outputs). Each band is adjustable from -15 dB to +6 dB in 1 dB steps. A fine tuning section also allows slight adjustment of each band's center frequency (eight options in 1/12 octave steps) and Q (0.5 to 15.0 in 0.1 steps).


  • Input Sensitivity:
    • Preamp: to 3 volts
    • Speaker Level: to 9 volts (20 watts RMS)
  • Output Voltage: 4 volts
  • Frequency Response: 10 Hz to 22 kHz
  • DSP Bandwidth: 56 bit
  • DSP Processor: 172 MHz
  • D/A Converter: BurrBrown
  • A/D Converter: BurrBrown
  • Signal to Noise Ratio:
    • Digital Input: 112 dB
    • Analog Input: 107 dB
  • THD: 0.002%
  • Operating Voltage: 9.2-18 volts DC

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