Car Audio Upgrades
BMW 325i / e46
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Investigation
Close-Up
New Speakers
New Speakers
As outlined on the first page, I want to demonstrate the value of changing the BMW speakers while leaving the electronics intact. To make the point, I'm using relatively cheap drivers - later, after we know this is going in the right direction, we can always move upmarket if needed.
Here's the complete analysis, speaker-by-speaker...
Front Door Pillar Tweeters
The stock BMW tweeter has a 1.00" body OD, 0.50" depth, 8 ohm voice coil. They're quite cheap, soft poly dome / small voice coil / lightweight magnet. The sound is just a gentle mush and they can really use an upgrade. I contemplated using "car" tweeters such as Infinity / Polk / Boston, but finally settled on some Audax drivers from Parts Express. Given the way retail merchandising works, it can be far more cost effective to buy loose OEM parts than boxed, branded, retail sets. I estimate the Audax tweeters to be in the same realm as the mid-range Infinity / Polk / Boston gear.
The Audax tweeters have the same 8 ohm rating as the stock BMW parts, so they're compatible with the existing Alpine amp. By removing the outer flange from the tweeter, I find they fit snugly into the BMW plastic carrier that bolts to the door pillar. This Audax is an excellent fit for the 325i / 330i door. It's bigger than the stock BMW part, as big as it could possibly be, but it still fits nicely.
The Audax tweeter uses a textile dome and larger voice coil. Sound is significantly better than the old BMW part, and a bit louder. The highs are "lifted up" above the previous mish-mash.
Front Door Midrange
2.50" body OD, 1.25" depth, 8 ohms, paper cone with rolled cloth surround. This turns out to be an OK driver, compared to other, weaker system parts.
I compared it to a Peerless poly dome midrange, by switching the connections and listening to CD's and radio. There was little difference between the two, especially when considering all the other things going on inside the car. For now I've decided not to change out these midranges.
Front Door Bass
Rear Mid-Bass
6.25" body OD, 2.75 depth, 2 ohms, plastic basket, paper cone, foam surround. Man oh man, is this ever a piece of crap. The paper cone is about as stiff as a paper towel, and the foam surround is thick and hard. If you think all the fuzzy thumping bass distortion is coming from your stock BMW Alpine or Harman Kardon amp, here's a news flash: It's the speaker!
I replaced the rear deck drivers with Goldwood parts from Parts Express. They're 17 $ in single quantity, and they really make a significant difference. The Goldwoods have poly/mica cones, rubber surrounds, heavy magnets, bigger voice coils, and metal baskets. The three significant differences over BMW stock drivers are:
- Cleaner, deeper bass! I was surprised to find that the load fuzzy thumps I thought to be amp failure turned out to be from the old BMW speakers. The Goldwoods just reach deeper, and give way cleaner, more accurate bass extension. This is a very good sign for the stock Alpine amp.
- Clear midrange. There's a lot of midrange power coming from the rear deck speakers, but in the BMW parts the midrange is largely due to higher order overtones of distortion. The BMW speakers, with floppy paper cones pumping against stiff foam surrounds, seem to create far more blaring, muted midranges in comparison. The Goldwoods lift vocals right up out of the music.
- Quieter program power. The Goldwoods are 4 ohm speakers, while the Alpine amp expects 2 ohm loads and the Harman Kardon expects 3 ohms. The Goldwoods might be at half the volume of the stock 2-ohm parts, it's hard to say. On the CD player's fader control, this corresponds roughly to 2 or 3 ticks along the adjustment scale [toward the rear of the car].
Based on these comparisons with the cheap Goldwoods, I've decided to move up into some Vifa 4 ohm mid-bass drivers. A little more efficient, flatter response, and more polite upper-end curves that should help the midrange.
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