I looked at the Earthquake and SWS OEM under seat replacements (along with the Audison and Ground Control ones, specifically). Both of them take significantly more power than the OEM ones, and quite a bit more than most of the under seat replacement woofers... but I have read mixed reviews on them. Most of the negative SWS/Earthquake reviews talked about the speaker blowing or falling apart after a period of time. I don’t want to turn you away from them (for all I know they may have sorted the issues out) but I would definitely recommend doing plenty of research before pulling the trigger.
I spent hours on these particular speakers because of their significance to the overall system. I’m doing so I came to the conclusion that no matter who makes them, they are all going to be limited in what they can do. This is because of the parameters that the designers have to work with. Those under seat enclosures are small and awkward. There just isn’t much room to work with. I felt it was better to go with a woofer that’s was capable of playing in just about any type of enclosure, or no enclosure, and the NEOs really fit that bill. In fact, when you get them there is a letter in there that talked about why they built them... and that was exactly the reason. An 8” mid woofer that could go just about anywhere. Believe it or not there really aren’t many quality mid woofers out there that can do that!
What I will confirm for you is that these NEOs hammer really good when you have it crossed over at the right point. I just finished getting those puppies in over this past weekend and have been tinkering around with the crossover points for them. Initially I had the high pass set around 140Hz (with a 24Db curve) but after speaking with Jimmy I tried lowering them to 60Hz (with a very steep 42Db curve) and that made a huge difference. They aren’t even broken in yet and they really sound great.
By the way... when you go to replace them do yourself a huge favor and remove the seat from the car. I was trying to get the passenger one out in my garage (it was raining) and I hardly had space on that side of the car so I tried to tilt the seat back and take the enclosure out that way. I managed to do it but it took me much longer than necessary. Don’t make the mistake I made...
Also, if you have a newer model year BMW chances are the OEM woofer is glued to the enclosure. The earlier models had screws that held them in. If there are no screws holding them down you will have to use a hammer and a flat head to break the seal and some elbow grease to pull them away. I ended up screwing my adapter plate to the housing where the earlier models would have been mounted, but when I undo all of this I know I’m going to have to lay down a need of caulk to get the OEMs back in place. The video I linked to in one of my previous posts, from BavAuto, goes in to this and shows you how to hammer out the woofers that are glued in. I highly recommend watching it (it’s easy to damage the OEM enclosure if you don’t!).
This is what mine looked like after I got the ADs mounted on the OEM enclosure. You can see the brass screws where the earlier style woofers would have been mounted. Those are just going through the HDPE adapter I fabricated. I think Jimmy mentioned using a 3/4” piece of HDPE. I only had 1/2” sheets so I used them and they worked out okay. The back may be a tad bit closer to the enclosure than I would have wanted but it was still a good 1/2-3/4” clearance between the back of the NEO and the enclosure. I also seem to have gotten a newer version of the AD because the speaker wire connectors are not as large and intrusive as the ones that were on Jimmy’s. In fact, they barely went past the bottom of the speaker. One thing to note: you may or may not get the oval-ish metal bits that are under the screws in the hardware package with your NEOs. I did and everyone I asked could not figure out what they were for. After giving it some thought where they are now seemed like a logic place to use them since it protected the frame from being damaged when you put the screws in:
Oh... and you don’t have to worry about grills since the OEM grill will cover it nicely and the speaker won’t touch it even sheen it’s extended to its max.