BMW E38 7-Series E39 5-Series E53 X5 DSP Audio Amplifier Information, Coding & Advice

Navigation A/V Forum
Subject: DSP Amp Thoughts and Buyer's Advice
Author: Brian (moderator) : member since January, 2005 : 10979 posts
Posted on: 2006-05-25 10:38:01      
Bookmark and Share

Tinkering with DSP amps after my upgrade has kind of become an accidental hobby for me. Over the last year, I have probably installed at least a dozen different amps in my car out of curiosity and to help a few local friends fix their amp problems or do upgrades. Along the way, I have learned a few things that I thought others might find useful. Also, I thought that I might re-consolidate the information in a single post…

There are 2 Major versions of the DSP amps.

The early amps are made by Philips, and they are distinguished by a squared-off heat sync on the end with the plugs, an “X” pattern stamped on the sides, and the large, square BMW part number sticker stuck on the side.

The later generation of amps are made by Loewe (around 1997 – 1999) and Lear (1999 to present). The Loewe and Lear amps have an angled heat sync on the end with the plugs, and the sides are smooth. Most of the Loewe and Lear amps have a small part number sticker on the end with the plugs. The two newest Lear amps have a rectangular PN sticker on the side with “E39 / E53” in the title of the label. (Do not let the E39-E53 thing worry you, they are still perfectly compatible with the E38 too.)

The key difference between these two major version of amps is that the Philips amps are not compatible with the BM53 and BM54 radios. So, if you are doing a nav retrofit that will include the new radio, and your car is a 1998 or older, you will probably need to upgrade to a newer DSP amp too.

Between the Loewe and Lear, I have found very little difference in audio performance and no difference in compatibility. I have no idea what the functional differences in the amps are behind the scenes, but they were nearly identical in my car.

Also, you can not use the part number to determine if the amp is Loewe or Lear. For example part number 65.12-6 905 119 is far and away the most common Lear amp you will find on eBay (or other used sources). However, I have seen two amps with this PN that were manufactured by Loewe. So, if you really want a Lear amp, then make sure you can read “Lear” on the PN label before you buy.

What does “coding” do?

When a dealer or specialized BMW mechanic connects a car to BMW’s proprietary computer to configure any of the computer-driven components, the process is called “coding.” The DSP amp is one of the computer-driven, configurable parts in the car. The biggest thing that coding does for a DSP amp is to configure it for a navigation-equipped car or a non-nav car. In a navigation-equipped car, the nav computer is the thing that controls the DSP amp. In cars without nav, then the DSP amp is controlled by either a separate DSP controller (like in the E38) or by the MID (E39 and X5). If the amp’s coding is mismatched (nav coding in a non-nav car, or vise versa), the amp will not receive control communications that it expects, so it will shut down after about 30 seconds. This is totally normal, until you get the amp coded—it is typical for folks who have done a nav retrofit or installed a used amp that was coded for another type of car.

The other major thing that I believe coding does is setup internal crossover frequencies and internal equalization settings that match the car’s acoustical characteristics and speaker arrangements. Think about it—BMW uses the very same amp in the E38, E39, and X5, yet they have very different cabin arrangements, numbers of speakers, and speaker placements. So, I am about 99% sure that the coding also sets up the amp for the specific model in which it is installed. My key support comes from the fact that I bought an amp coded for an X5 and installed it in my car. It sounded absolutely horrible, yet it was a perfectly good amp and several years newer than the one I had. The midrange was overly bright and almost droning, and it had no bass at all. I could not lower midrange equalizer settings enough to solve it. I originally upgraded to an amp that came from an E39 M5 with navigation, and it initially sounded OK in my car. However, after I got it coded in my car, it significantly improved the sound quality. (The difference between the E38 and E39 is not as dramatic as the X5, but you can still hear it in the amp.)

So, my recommendation is that if you buy a used amp coded for a different type of car from yours, consider getting it coded, even it works OK.

Audio comparisons

Generally speaking, I think that all the amps sound pretty similar. A lot of folks who have upgraded from a Philips amp to a Loewe or Lear amp have commented that their original Philips amps sounded warmer with more balance in the mid frequencies. That may be true, but it is more likely that their newer amp was possibly coded for a different type of car, and not re-coded for their car.

The Loewe amps sound pretty much the same as the Lear amps. However, I do think that my Lear amp, PN 65.12-6 905 119, may sound just a little bit better than the Loewe amps that I have tested. I think that the highs on the Lear are a little clearer than the Loewe amps.

I just installed the very newest Lear DSP amp, PN 65.12-6 940 977, in my car, and I think that it may sound subtly better than my older Lear amp. The highs are crisper and clearer than my old Lear, the midranges feel smoother, and the bass is not as punchy.

What kills DSP amps

From folks whom I have talked to, the Philips amps just seem to die on their own. It may only be a problem with the earliest amps, but those seem to have the most unaccounted for failures. Overheating, Leaking Capacitors, Jumpstart / Battery Changes... After that, water damage is the next big amp killer. Water damage was the cause for every person I know who replaced a dead Loewe or Lear amp. So, if you have a Loewe or Lear amp on the fritz, carefully examine your trunk for signs of water.

Summary, recommendations, closing thoughts, etc.

♫ Unless you really want a Philips amp, avoid them. They are cheaper, but more prone to failure and not compatible with the new gen radios.
♫ Loewe amps are OK and fully compatible with everything.
♫ Lear amps seem to be the most desirable. They are the current manufacturer for BMW, and they may sound slightly better than the Loewe.
♫ Lear amp PN 65.12-6 905 119 is the all-around best to get. That is the most common used Lear amp. It has a relatively low price (compared to the newest Lear amps), very good sound quality, and greater availability.
♫ Lear amp 65.12-6 940 977 (the current model) sounds the best of all, but can be pretty expensive still.
♫ If you buy a used DSP amp and you have a critical ear, you may want to get it coded in your car anyway. That will guarantee that the nav/non-nav, crossover points, and equalization settings are right for your car.