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AudioControl FOUR.1

In-dash equalizer with line driver

Item #: 161FOURP1

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6 Reviews | 1 question - 1 answer

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This is not your father's EQ

AudioControl's FOUR.1i equalizer takes the old-school in-dash EQ to a whole new level. This little problem solver features 4-band equalization, a parametric bass equalizer, and a built-in line driver that'll send a hot, clean signal to your amps.

Rear connections

Find those trouble spots

Mount the FOUR.1i in your vehicle's dash opening along with your receiver, or under the dash if space is an issue. For connections, you'll find a set of inputs, front and rear outputs, and an auxiliary input for an iPod or other audio source. You can adjust response at 125, 500, 2000, and 8000 Hz, then use the parametric EQ to find and kill any bass trouble spots between 40 and 80 Hz.

Set up in an instant

AudioControl makes it easy. Bring up your input knob until its LED starts to flicker, then adjust your output level to get the most out of your amplifiers. You can switch between your main and auxiliary sources with the touch of a button. The ground isolation selector allows you to minimize noise in your system. You can choose between green or amber illumination.

Information provided by AudioControl


Product Highlights:

  • in-dash equalizer with line driver
  • steel chassis with gold-plated RCA jacks
  • 4-band EQ (125, 500, 2000, and 8000 Hz) with parametric equalization for bass (adjustable from 40 to 80 Hz, +/-12 dB)
  • balanced inputs eliminate noise
  • line driver increases output up to 9.5 volts RMS
  • inputs: stereo RCA, auxiliary RCA
  • outputs: front and rear
  • green or amber illumination
  • frequency response: 10 to 100,000 Hz
  • signal-to-noise ratio: 110 dB
  • fuse rating: 1 amp
  • size: 6-3/4"H x 5"W x 1"D
  • weight: 2 pounds
  • warranty: 5 years
  • Our 60-day money-back guarantee

AudioControl FOUR.1 Reviews

Average Customer Review:

6 Reviews

Sterio install in 1967 442 Cutlass

Written by: Mike W from winchester, VA on February 6, 2016

Crutchfield Customer Review (What's this?)

My 1967 442 Cutlass is a frame off completely restored car. It has a factory am radio which is undisturbed. The system I set up in my car is played completely threw blue tooth called the Mark III because I'm using my phone to transmit my signal threw the Mark III I am using the Four 1 to fade the front and back speakers. Crutchfield said that it is your father's EQ on steroids. That's is a under statement. The Four 1 performed perfectly. Thanks Crutchfield for all your help

Pros: The fade works perfect. The master volume works perfect. This EQ is perfect for my system.

Cons: None

Equalizing the right way!

Written by: Anonymous from Kansas on February 15, 2014

My bass would fade down as I drove due to change in voltage (or something like that). After installing this I would always get maxium bass, and I could adjust it when I needed that little extra punch on my bass! Before installing this equalizer I was not happy with the constant bass/clarity I was getting from my stock radio with aftermarket speakers and sub. After installing it I am now happy with the way my system sounds! I feel I have completed my system. Would recommend this to everybody that loves to hear music! I had a professional install it.

Pros: Constant bass while driving Awesome tuning on the fly Completed my car system!

Cons: None so far.

wow, this thing is serious!

Written by: jason from georgia on April 19, 2012

Crutchfield Customer Review (What's this?)

Already have a great system but I could tell it could sound even better. The pre-amp line driver feature alone allows for a dramatic difference in clarity and sound quality!

Pros: Professional grade product. Sound quality is amazing!

Cons: None, highly recommended

Works as advertised

Written by: DanD from Atlanta, GA on April 11, 2011

Very nice EQ. I got it to integrate with my factory amp which uses a differential input. The AudioControl changes the normal output from my Alpine HU to the input required by my amp. Sounds very good.



yep the best eq out there

Written by: steven from newyork on May 30, 2010

Crutchfield Customer Review (What's this?)

This EQ is the best.It will totally enhance your system unlike the others out there.As soon as I hooked it up,my system came alive and I dont even have to raise the volume real high to get the benefits.Its worth the money.I was at first skeptical because of the price,but like they say if you want something good you know what you have to do



AudioControl FOUR.1

Written by: CREATOR from Calgary AB Canada on October 12, 2009

PIMP piece- AGAIN! Another product in my SHOW TRUK! Wouldnt be without it! Total control and COOL sweep adjustment finds THE loudest Bass frequency IN UR VEHICLE! Then, the GAIN control? AND the MASTER volume?? OUCH! Hard hitting, tight, hammertime bass. The double octave EQ points, are perfect for those pesky naisly midrage tones! & the 8K adjustment just takes the edge off, off-axis tweets to keep them from peeling off ur eyebrows!

ONE input and it gives u FADER output- WHO else would think of that! CONTROL both ur Bass amps AND ur component power! DO urself a favor and Get ur mitts on one of these NOW!



Hands-on research

What's in the box?

Download owner's manual

  • Pre-amp line driver/EQ
  • 2 Mounting brackets
  • 4 Mounting screws
  • Owner's manual
  • QC checklist
  • Product registration card

Product Research


Description: The Four.1i is a combination equalizer/line driver. The 1/2 DIN chassis can be mounted in-dash, or under-dash using the included brackets.

4 Band Graphic EQ: The rotary knobs adjust the signal +/-12 dB at 125 Hz, 500 Hz, 2 kHz, and 8 kHz. There's a notch at each knob's center position so it's easy to return to the flat setting.

Para-Bass: Para-Bass is a single band, parametric equalizer for the bass output. Like the four graphic EQ bands, the adjustment range is +/-12 dB; the center frequency is continuously variable from 40 Hz to 80 Hz.

Line Driver: To achieve the best possible signal to noise ratio and dynamic range from your amplifier, the built-in line driver can increase the head unit's output voltage up to 20 dB (9.5 volts RMS/ 13 volts peak).

Aux In: In addition to the main input, there is an auxiliary input (stereo RCA). A switch on the front panel toggles between the two inputs.

Volume: If you choose, you can adjust the system volume using the Four.1i's volume knob. This allows you to leave the source volume at it's maximum un-clipped level, resulting in the best signal to noise ratio and dynamic range output from the source.

Fader: Because there is only one stereo line input and both front and rear line outputs, the front panel fader knob is needed to adjust the relative front and rear volume.

Input Gain: The input gain for the left and right channels is set independently; 0 dB to +20 dB. The +20 dB gain allows you to increase the head unit's line voltage to the top of your amp's input range; up to 9.5 volts RMS/13 volts peak.

Balanced Inputs/Outputs: Using the balanced differential input circuit cancels noise picked up in the transmission line between the Four.1i the the source unit, or between the Four.1i and the amplifiers. Both the main and auxiliary inputs and the outputs can be individually set to balanced or unbalanced, incase your amps don't accept balanced inputs.

Ground Isolation: The power supply ground is switchable, in case of ground loop noise. The factory position is fully isolated (typically the best choice), but can be changed to Ground or 200Ω.

Terminal Block: The power/ground/remote/illumination terminal is removable; the wiring is attached to the block, then the block is plugged into the rear panel of the Four.1i.

Illumination: The outer ring of each knob is lit whenever the illumination terminal is energized. The color is switchable between green and amber.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Product reviews from the Crutchfield Labs

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Customer Q&A

1 question already asked

Thanks for your question. For information on comparing two or more models I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They will be able to help determine the differences and help you make the best choice for your system and your budget. [ Krissy  Nov 02, 2015 ]  Staff