W204 sub replacement
 

I've searched and can't find much about replacing the 8" sub in the factory location. There seem to be more options nowadays for shallow mount subs and many have good reviews, so I thought I'd try something different from the 8w7 and 500/1 that I've had in my past 3 vehicles.

Has anyone swapped the factory sub on the rear deck? I admit I haven't investigated much or taken anything apart to see the dimensions, I'm just wondering if anyone has experience, knows what fits, or has even seen it done.

According to Harman, the W204 got the oval dual coil shallow mount "racetrack" sub on the rear deck. It's 8 x 10 which is an odd form factor for an aftermarket replacement. If your only gripe with the system is insufficient bass, your best bet would be to remove the factory sub to vent the trunk space to the cabin and install a subwoofer amp and enclosure in the trunk. You can pull signal from the speaker leads going to the existing sub at the amp, located behind the left (drivers side) trunk liner. You'll want an amp that offers auto sensing power, and accepts speaker level inputs.

The link in my sig has more info on upgrading HK Logic 7 systems.

Yeah I found some pictures of the sub assembly, so I did find out it was oval. It looks like the plate could be replaced and would have enough room for a shallow 8". I'm wanting to avoid having an enclosure in the trunk, the w7 I've been using doesn't exactly allow for a small box, so I'm trying to see if i can cram something useful into the factory space.

I'll have to read your site later, looks like a lot of good info there. Thanks!

Also consider keeping the factory sub but giving it its own amp so you can bump up the output. The real weakness in the HK bass is in the factory EQ and power allocation. The sub itself is way underutilized in the factory set up but it can handle a lot more signal and power.

I kept it intact in my S class ( same unit you have) but gave it its own 300 watt JL amp. You wouldn't recognize it compared to stock.

I know exactly what you're talking about. I agree the EQ sucks, and when the right song is on and it's in the sweet spot at certain frequencies it actually sounds pretty impressive. I just figure that aftermarket subs are pretty cheap and they can't be worse than stock.

Where did you tap the input for the sub amp? Does the output from the factory amp include the full range, ie., is the crossover at the sub assembly or at the amp?

All of the crossover occurs in the DSP of the amp. That's how they end up with a "14 channel" or "12 channel" system. Each individual speaker gets its own channel and is wired directly to the amp. No physical crossovers.

I would pull signal from the designated subwoofer channel. I think there's enough midbass in the factory output to play with, and use the outboard amps crossover and level controls to get more of the punch you want in the low end.

Well, after 30 minutes of disassembly and one broken c-pillar clip, I removed the sub assembly. The sub appears to be glued into the assembly and I'd have to do some major cutting or scrap the whole thing. It would also only allow for about 2.5" of depth. The only way to get a worthy sub in its place would be to cut the rear shelf out under the sub. Wanting to avoid that, I'll be putting this thing back together and going with your suggestion of an aftermarket amp.

It's actually a decent sub with the right amp. Very stout by design, dual coil and it can handle a lot more signal than it gets from the stock amp.

I know this a coupe of years old. Did you end up amping the existing sub? How did it work out? Considering the same option on my HK system.