We have a customer with a beautiful blue 2011 BMW 328i. This car is full of options standard from BMW, but the stereo gives no justice to the rest of this luxurious vehicle. This one in particular even came with the Logic7 system, which sounds better than the base-model system but is still far from “up to par” with our standards. We have many customers from the Baltimore Washington Metro area, Eldersburg, Mt. Airy and Frederick that own 3 series BMW’s. We have upgraded the stereos in many of them!
One of this BMW customers main requests was adding a decent amount of bass. We needed to do this in such a way that would not take away from the integrity of the car, and would not require him to lose a lot of trunk space. We also needed to integrate any parts we were installing to the factory radio. To integrate an amplifier, we already knew we would be using the LC2i made by AudioControl. This would give us a clean, high-quality pre-amp signal out of the factory amplifier. The LC2i also gave us what’s called “accubass.” This feature automatically corrects for the bass roll-off that is common with many factory installed audio systems, where the bass level is diminished as the volume is raised. Bass roll-off was designed to help prevent damage to factory speakers at higher volumes, but when adding an amplifier and subwoofer it needs to be corrected. Beyond bass, the customer was also looking to improve the sound quality of the stereo in his BMW. We took on the challenge and here’s what we did!
First, there was going to be a problem with getting the sound from whatever subwoofers we installed in the trunk… INTO the car. This vehicle has a rear firewall, and a lot of sound deadening material in order to make the ride quieter. As we have done in several other BMW’s, we rectified this problem by opening the back of the ski hole in the center of the rear seat and eliminating the metal plating. This opened up enough space for the bass we would be adding to travel into the cabin. We also installed Hushmat Ultra Damping Padding in the trunk and on the trunk lid in order to reduce vibrations and reflect the sound waves toward the front of the car. At the end of it all, these two modifications made an enormous difference in the outcome and output of the stereo.
Now on to the fun part; BASS. For this BMW we chose the impressive HD750/1 amplifier built by JL Audio. This amplifier is top notch. JL Audio put a lot of effort into the research and development in order to produce such a beast in such a small package. Read more in detail about it by clicking HERE. We then moved on to the selection of a subwoofer package. The choice was quick and easy. JL Audio makes a Stealthbox enclosure for the car! Their Stealthboxes are premium custom built enclosures that are manufactured and tuned to be vehicle-specific. As you can see in the photos below, the Stealthbox for this particular vehicle was form-fitted to the back of the rear seat and spread all the way across in between the rear wheel wells. This design allowed for an incredible amount of bass to be delivered by the two JL 13TW5 subwoofers without taking up much trunk space at all. The combination of the HD750/1 and this Stealthbox created a booming bass to be reckoned with… Now we had a little work to do on the rest of the stereo to improve the sound quality.
From the factory, this vehicle came with two woofers; one under each front seat. They were set up as subwoofers to play strictly bass. Because of our additions in the trunk, we reconfigured these woofers to play mid-bass since we had taken care of the low-end bass. We then also modified the phasing of the factory tweeters, drastically improving the staging. This lifted the position of the music being reproduced and centered it, giving the stereo more of a true concert sound. When we install a hi-fi system in a car, we are attempting to reproduce a very complex pattern of sound waves within an environment that is quite different to the one in which the instruments and vocals were recorded. We are trying to recreate not only the sounds of the various instruments and singers accurately but also their positions on the ‘sound stage’. This is often called ‘imaging‘ or ‘stage image’. It may also be described as staging, but in car audio this word is generally used to describe the position of the stage itself (whether it appears to be in front of the listeners or behind them), rather than the position of the performers on the stage. Once this was done, we then installed a JL Audio XD400/4 amplifier to power new German Maestro CC4008 coax speakers in the front doors and the factory woofers under the seats.
With these modifications to the stereo and trunk, along with the addition of the amplifier and Stealthbox in this particular vehicle, you would think we replaced EVERYTHING. The difference was night and day. Every piece of electronics coincided beautifully. The clarity, the transitions between frequencies and accuracy of the bass notes were all impressive. We were thoroughly satisfied with the outcome of the stereo in this BMW 328i!
