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Tuesday, April 23, 2024

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Doug Vetter, ATP/CFI

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BMW E36 HK Audio System
Speaker Upgrade DIY

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(Image: Closeup of CDT 6x9 infinite baffle subwoofer)
Spurred by a need to replace a failed midrange driver, I decided to
replace all of the speakers in my E36.


This article explains how I replaced the speakers in my 1998 HK-equipped E36 using aftermarket drivers.

Before we get started, some background is necessary. The HK system uses an external, trunk-mounted amplifier that contains passive crossovers. This means that the speaker outputs of the amp are not full range signals so you can't just plug those into a component set with its own crossover and expect to get something listenable. If you intend to keep the amplifier and simply replace the speakers (definitely the simplest solution), that limits the number of options for replacement drivers. See "Choosing Drivers" below for more.

There have been a couple revisions of the audio system over the production run of the E36. Early systems came with a complement of round drivers mounted to the rear deck in a large square enclosure, while later models like my 1998 came with a smaller oval enclosure consisting of a 6x9 driver woofer and 2" component tweeter. You can easily determine if you have 6x9 drivers by sticking your head in the trunk and looking up at the rear deck. A black plastic oval enclosure indicates you have 6x9s. If that's the case, you can follow this DIY verbatim to replace the drivers.

If your vehicle is equipped with the older square boxes, you will have to buy some aftermarket mounting adapters as buying the BMW adapters pictured as provided in later vehicles is not an economically viable solution unless you can lift them from a parts car or a junkyard. I recommend using the adapters sold by BSW with one caveat: they do not provide a mounting location for a component tweeter. If you need to use these adapters, that means you have a few options:

Choosing Drivers

No matter what drivers you choose, if you intend to retain the HK amp, keep in mind that running any driver without the crossover designed for it may result in poor sound quality or, in a worst case scenario, damage to the driver. This is especially critical with tweeters and Polk units in particular. I've blown my share of Polk tweeters in the home to know better.


Replacement of the speakers in the E36 requires the following:

Front Speaker Replacement

  1. Remove the door panel. By now there are a ton of door removal DIYs on the net so I won't belabor how to do that here. I will point out, however, that a door removal tool is essential to prevent damage to the door panel. Unfortunately, even if the proper tool is used, due to the poor quality of the glue used in the manufacturing process the mounting tab or storage pockets may separate from the door panel. In this occurs, the parts must be glued to the door panel before the panel is reinstalled on the door. The best glue to use for this (courtesy of my technician) is 5 minute 2-part epoxy.
  2. Remove the midrange from the grill assembly. Remove the midrange and grill assembly from the door panel by unscrewing the locking ring from the back of the door panel. Once it's removed you'll see that there are two locking tabs that must be depressed with a screwdriver to release the driver from the grill assembly. You'll reuse the grill assembly, so do yourself a favor and protect the grill side with some blue painters' tape. It would be a shame to scrape that up and have to buy another one at $80 a pop.
  3. Install the new midrange in the grill assembly. The BSW units were a snap fit, but I found them a bit loose in the grill assembly. To prevent vibration I used a hot-melt glue gun to secure the driver to the grill assembly. I found it a bit difficult to get the glue in the right place because the gun was too big to fit into the recess between the driver and the grill, but tilting the grill assembly at just the right angle allowed the glue to fall right into place. Hot melt glue cools and solidifies fairly quickly (which is good or bad depending on how you look at it...if you don't know what I mean, you will), and I found I didn't need much to secure the driver.
  4. Remove the tweeter from the grill assembly. The tweeter assembly may be removed from the door panel in the same manner as the midrange. When it came to release the driver from the grill it was a bit more involved as I found my tweeters secured to the grill with a bit of glue. I broke that free with a screwdriver and then popped the tweeter out of the grill.
  5. Install the new tweeter in the grill assembly. Before the Polk db1000 tweeters would fit nicely into the grill assemblies I had to grind down the locking tabs on the grill. I used one of the abrasive stones on my Dremel. Literally five seconds per tab is all it took and the tweeters press fit right in like a glove. One note of caution, though -- when I mean press fit, I mean press fit. It's not like I couldn't remove the drivers if absolutely necessary, but it was pretty obvious the drivers wanted to stay put. Make sure you're ready to install them for good and push them home. As you will note in my pictures, I did not push them all the way into grill, and that was intentional so I could use a screwdriver to pry them out of the grills at some later point if necessary. I applied a few small beads of hot melt glue to secure the driver because I had the gun there ready to go, but it wasn't strictly necessary.
  6. Prepare the car's wiring to accept the aftermarket midrange and tweeter. The bad news is you'll need to cut off the factory connectors. The good news is Polk provides pigtails off of their driver and BSW provides some wires with pre-crimped, polarized spade connectors that are a perfect fit for their drivers. All I did was cut the pigtails to an appropriate length (about 18") and splice them in with the stock wiring using some mid-line splice spade connectors to facilitate later removal of the door panel. All wiring was bell spliced and covered in heat shrink because I can't stand butt splice connectors, but use what you want in your car.
  7. Remove the kick panel. Removal of the kick panels requires removal of the footwell ceiling panel. Both panels require removal of two screws and the wiring associated with the footwell lighting. All in all pretty easy. Then, to remove the driver's side panel, unfasten the hood release and set it aside. Finally, remove the kick panels themselves by pulling them aft before pulling them away from the car.
  8. Remove the woofer and install the new unit. Removal of the woofers requires an 8mm socket or screwdriver. Once the drivers have been pulled out of the cavity in the kick panel you may note that one of the terminals is smaller than the other. Depending on the vehicle and the chosen speakers, you may need to cut off the factory spade connector(s) and affix your own. Basic stuff, really. When done installing the new drivers, keep the kick panels off the car until you've completed system testing.

Front Speaker Replacement Highlights