BSW Knowledgebase

Tuning an Amplifier in your BMW

Testing the Actual Installation Prior to Tuning

First things first, after physically completing the installation, make sure your amplifier is powered up properly. It needs to turn off and on with the key. The power light should turn off when you take the key out of the ignition. Test this out a couple of times to make sure. If it does not, and you are having trouble figuring out why, give us a call or drop us a line. Trust us, it won’t be anything major.

Now We Begin. . .

Now, go to the front of the car, and turn on the stereo. Put in your favorite CD (not a burned CD, but one that was professionally mastered and recorded), and tune in to your favorite track. We recommend using a very dynamic type of music, with many types of musical variations within the CD.

Before You Start to Make Any Detailed Adjustments

As for the physical adjustments of the amplifier(s) you are tuning, first make sure the gain(s) are turned all the way down. That is, the knob turned all the way down to the left. Next, set your appropriate crossovers. Crossovers basically tell the amplifier which frequencies to allow the speakers to reproduce. High pass crossovers are for interior speakers, and low pass crossovers are for subwoofers. Now, roughly adjust the crossover frequencies, setting the high pass crossover between 90 -150hz for the interior speakers, and the low pass crossover between 90-150hz for the subwoofers. Hertz (hz) are simply a unit of measurement used to measure a particular frequency. If you set the low pass crossover at 100hz, that means that frequencies above 100hz will start to roll off ( not be played at full output volume)at the predetermined slope of your amplifiers crossover, be it 12db, 18db, or 24db. (These are the most common crossover slopes, your amplifier may vary) All frequencies below 100hz, however, will be allowed to play through the particular output (speaker)

By setting a high pass crossover at 100hz for example, this means that any frequencies below 100hz will start to roll off ( not be played at full output volume)at the predetermined slope of your amplifiers crossover, be it 12db, 18db, or 24db. (These are the most common crossover slopes, your amplifier may vary)
All frequencies above 100hz, however, will be allowed to play through that particular output channel (speaker).

Adjusting an Amplifier for Your Interior Speakers

If you are adding an amplifier for your interior speakers as well as a subwoofer amplifier, you must first start the tuning process with this amplifier before adjusting your subwoofer amplifier, which will be covered later in the tuning process.

Adjusting a four channel amplifier is very detail oriented. Again, with your gain(s) turned all the way down, begin to turn the volume of your source unit up until you reach its maximum volume.
This will vary depending on the source unit you are using. If it is an aftermarket unit, the volume scale usually operates between zero and a certain number, say 62. If this is the case, you would turn the volume back down to about 59. Have your bass settings set completely flat as well. You should be able to independently adjust your subwoofer. Make sure the preliminary crossovers have been set (high pass) and the frequency roughly adjusted (90 -150hz) before you proceed.

If you are integrating into an OEM system, tuning becomes a bit more difficult. Most BMW’s do not give a numerical readout of volume. You simply have to know how loud it is by the perceived volume, not a number. You will need to spend more time making adjustments in this situation. We recommend turning the knob to the right (clockwise) around five or so turns. Make sure the preliminary crossovers have been set (high pass) and the frequency roughly adjusted (90 -150hz) before you proceed.

Front Speakers First

Now, slowly begin adjusting the gains up (clockwise), blending in the front speakers first.
Begin increasing the front gain until you detect the slightest bit of audible distortion in your front speakers. Take careful precaution to ensure that absolutely no distortion is present in your front speakers before proceeding. Distortion is when your speakers begin sounding muffled or crackled, if that makes any sense. Distortion will blow your speakers, and blown speakers are NOT covered by warranty. If any distortion is audible at any point in the tuning process, back the gain down (counter-clockwise) about 1/16th of a turn to the left, or until the distortion becomes inaudible again.

Moving to the Rear

Slowly begin to blend in the rear speakers by increasing the gain (turning the knob clockwise) until they become audible. You don’t want them to overpower your front speakers, as you are trying to develop a soundstage in the front of your vehicle, aren’t you? Blend them in until you can detect their presence clearly from the front seats, but your ears aren’t drawn to the rear of the vehicle. This allows your soundstage to become more present, which is the primary goal of the entire installation, right? You want your rear speakers to be a part of the equation without a doubt, but not the focal point. Get it? When you go to a concert, where does the band play? Not behind you. Let’s all take our part in making the world’s BMW’s sound a little bit better. Thank you.

You might make minor adjustments here and there, but for the most part, you can leave this amplifier alone unless you change any other components in your system. At that time, it will be necessary to readjust your settings to accommodate your new products.

Let’s Add Some Low End

Now is the time, if you are adding multiple amplifiers, to tune your subwoofer amplifier. Remember to roughly set your low pass crossover around 90-150hz. For example, if you set your low pass crossover to 100hz, that means that all frequencies above 100hz will not be sent to that particular output channel (speaker).

If you also amplified your interior speakers, it is important to overlap your crossover points to ensure that there no significant gaps in the frequency response of your audio system. For example, if you set your high pass crossover for your interior speakers at 110hz, you need to set your low pass filter for your subwoofer at a minimum of 110hz, but not more than 120hz to keep an overall tonal balance in your BMW.

Again, with your gain(s) turned all the way down, begin to turn the volume of your source unit up until you reach the point where the interior speakers are distorting ever so slightly.

Now, back down the volume until the distortion disappears and stop there. Head back to the trunk and slowly begin adjusting the gain(s) of the amplifier until you are content with the amount of bass being produced by the subwoofer without any audible distortion of the woofer. Also, make sure the clipping light on the amplifier is not illuminating. If it is, back the gain(s) down until the light ceases to flash. Now, as you adjust the volume of the head unit, the bass will adjust proportionately with the rest of your music.

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