Part 1- Upgrade priority
The hifi system has some okay speakers in it. The real failings of the system are a couple-
1. The amp is underpowered
2. The underseat sub design is just terrible. They are actually okish speakers, but the physical constraints of speaker excursion and enclosure volume mean this is a mid-bass driver at best, and when pushed to run low frequencies it runs out of power and excursion really quickly.
So what makes the most difference?
1. Match up 8DSP. You get an amp that has the power that the factory system really should have had. It's not going to win any SPL competitions, but it makes the stock speakers come alive and will power the mid range PnP upgrades just fine. More importantly is it gives you time alignment and serious EQ power to adjust for the complicated acoustics of a car interior. It seriously makes a huge difference
2. A real sub. That means a box in the back or under the sub floor in the trunk well. You don't need anything amazing, you just need to obey the laws of physics to make low frequencies. The stock subs can't effectively produce low enough notes at any volume. This allows you to retune the stock subs as mid-bass drivers where they are a lot more effective.
3. Midranges and tweeters. You'll gain a bit of clarity and detail here. If you want to save a bit of money, you can do just the front doors. They'll have the most impact on clarity and imaging.
4. Last is the underseat subs. Due to the laws of physics there isn't a lot to be gained here. There are replacements that offer a little bit more excursion, provided you have power, or could be a bit more clear. If you're looking for a thumping sub you won't get it out of an underseat upgrade.
Part 2- Specific recommendations
The stuff I'm going to recommend is based on value for an easy DIY type install. If you're looking for a SPL king, or high end audiophile experience you're going to need to go more custom. I'll tackle these in the order I recommend doing them.
Note: When using EU shops, always run all the way to checkout for a final price. Most have ~20% VAT included in the list price and are cheaper when the US is selected as the shipping zone. The shops I mention below are ones I've actually dealt with. Update- With all the tariffs going on, please check what they will be before ordering overseas. It might still be cheaper, but I'd hate for someone to order and get hit with a surprise bill.
1. Audiotech Fischer Match Up 8DSP. Its the amp Bimmertech uses. There are other options out there but this is the easiest path. Yah, its expensive, but it also will make a huge difference to sound and is needed to integrate any other changes anyways. You should be aware that the stock amp has built in EQ and cross overs. This helps return that to a flat unified signal for any hardware changes. I reccomend buying this from 12voltshop its currently under $700 shipped. You'll also need a Match PP-BMW 1.7RAM harness cable for UP 8DSP amp. In addition you need about 4ft of 8gauge copper wire for both positive and negative, and a 50 amp inline fuse. You'll need 2 ring terminals as well. I bought battery cables on amazon that had ring terminals preinstalled. If you're uncomfortable with ordering directly, allwoods on ebay is a good, if more expensive, option.
2. Subwoofer. There are a ton of sub options out there. I think the best option is a low profile sub in the spare tire well under the floor of the cargo area. I got a JL audio 12tw3 preloaded in a box. I got a used one off ebay, so I won't link a store, but $400-500 seems typical. Any of the kicker 12" preloaded low profile subs would probably be fine, but the JL is regarded as one of the best low profile subs. Finding low profile boxes that fit to add your own sub is a PITA, so I think a preloaded low profile box is the best option for a cheap DIY approach. There is a custom box for 2 10" subs, but the box alone is $400. You can get a powered sub box, but I don't think they are a great value. They are slightly simpler to install, but limit options a lot. When looking for an amp you're looking for a monochannel amp that is 2ohm stable with an output in the 500-600w range. I just goto a major discounter and sort by % off and get whatever is closeout from a major brand. I ended up with an infinity 600w amp. In additional to the amp you'll probably need 4ft ea of 6Gauge copper wire for positive and negative. That varies a bit depending on mount location. You'll need a fuse around 70-80amp and two ring terminals. You may want a board to mount the amp etc to. Cheap commercial cutting boards are popular for audio installations. Any sub is way better than no sub. If that means the kicker rather than the JL, don't get too hung up on quality here.
3. Focal Inside speakersThere are a number of PnP style speakers. Bimmer tech, bav sound, focal, and I think a couple brands only available in germany I don't know much about. They are all mid range speakers. Sonic signature preference aside, Focal is a company that their primary business is high end speakers and I own home audio from them I was very happy with. That said focals are known to be very detailed speakers. That's a little much for some people's taste. You can tune it in EQ, but if you dislike detailed speakers, maybe try the others. The other big plus of Focals is it is possible to get them much cheaper than the others. I spent less than $400 shipped doing all the mids and tweeters. For a highfi system you need to buy three packages- Rear doors Focal F-ICBMW100, Front doors Focal ISBMW100L, and center channel Focal F-ICCBMW100 You need 1x each. If you're not comfortable ordering overseas they are on ebay at much lower prices than US retailers. Just be careful with part numbers as there are really similarly named parts. I can't vouch for bimmertech or bavsound, but people generally seem happy with them even if they are quite a bit more. I didn't need anything to install, but I'll cover the details when I get to the install section.
4. Under seat subs I'm sure this will be controversial with some people, but I honestly don't think you need to do this one if you do the above. The real sub will cover the frequencies these struggle with and allow the stock speakers to focus on the mid-bass where they don't bottom out. I'd get the focal isub bmw 2 There are a couple options out there. The Earthquake Sound SWS-8Xi is pretty popular. With the additional power from the 8dsp in 2ohm mode it models out as louder than the stock sub. The other options I'd consider more sound quality options than loudness options. Reports on the earthquake is that it has a big midbass hole that needs to be EQ'd out. Not a huge issue with the DSP, but a problem if you're trying these first. By the time you get here you don't need more punch from your mid-bass. The issue I have with the earthquake is that they aren't a ton cheaper than the focals I found. VS the sort of overpriced bimmertech and bavsound underseat subs they are a good deal. There isn't a lot needed other than tools to install these. I think the earthquakes require some adapters as they aren't a PnP speaker.
To be continued-
Part 3- Installing the gear
Part 4- Tuning using DSP PC-Tool for Match Up amps and RTA




