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      02-11-2010, 10:44 PM   #1

Drives: '06 AW 330xi
Join Date: Mar 2009
Location: North Jersey/Philly/NYC

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2006 330xi  [3.22]
Logic7 SWS-8 Underseat Sub Upgrade FAQ

So I have been researching quite a bit about the SWS-8 upgrade and have picked up allot from both the forums and my mistakes. Here are just some of the things I had questions about and the answers I have learned. Please tell me if I am wrong in any of my answers. Also please add any questions you had and the answers you have learned by either asking here on the forum or asking another individual. I will add these questions to my thread (with permission granted of course). Maybe we can even include the HiFI and basic sounds systems as well.

NOTE: I am only answering these in a simple way. Most of the topics I am going to cover have DIY guides or threads already posted on the forums so SEARCH before asking how, what, where, can, do, and why questions! Also I'm not a professional. Over the past year I have researched the E90 stereo system to death. I know quite a bit but not everything.

Is the SWS-8 upgrade for me?

The upgrade is for those looking for an improved low to mid-range sound output. SWS-8s WILL NOT produce ground shaking bass. This is simply because of the size of the SWS-8 woofer. The SWS-8s are 8" shallow mount woofers that can only travel so far. If you want hard hitting bass, bass that will make drivers next to you stare, you need a 10" or 12" trunk sub in a proper enclosure.

Also, many have mentioned that mid-bass suffers while bass improves.
Here are some recommendation for dedicated midbass drivers:
Morel ADMW9
Morel MW166
Kicker SSMB8

Should the underseat subs be in stereo or mono?

The underseat subs can be setup either way. You can run a 2 channel amp with 2ohm SWS-8's OR a mono amp with 4ohm SWS-8's in parallel making a 2ohm load on the amp. The 2-channel route will give a slightly better "punch" because of the lower impedance of the 2ohm SWS-8s. Of course there are other options and setups (the ones listed being the most common) but it really depends on your application. I currently have the 4ohm SWS-8s wired in parallel down to 2ohms to a JL 500/1 and I am planning on adding a trunk sub. (SWS-8s high-passed at 60hz, Trunk sub low passed at 60Hz)

Update: Since writing this thread I have blown my SWS-8s. I now have my stock L7 woofers amped and bandpassed from 150Hz down to 65Hz. I also now have a trunk sub in a sealed enclosure, powered by the JL 500/1 that blew my SWS-8s.

2ohm or 4ohm?

The impedance of the factory underseat subs in the Logic 7 system are 4ohms. Therefore, if you are only upgrading the subs than 4ohm SWS-8's will be required. If you want to power the SWS-8's in parallel with an added amp that can handle a 2ohm load, you need the 4ohm versions.

The ideal way to run the SWS-8's would be in 2ohms on a 2-channel amp (in stereo).

Update: The above statement is true when running the underseats as dedicated midbass driver's. As someone mentioned in a later post, the stereo separation is very low at these frequencies so if you're running these for bass, mono is fine. Really it's up to you. I don't think an average enthusiastic can notice the difference between stereo and mono....however I haven't heard a stereo setup don't hold me to that.

Originally Posted by Technic View Post
Note: the Logic7 OEM woofers are 4 ohms (70W), the HiFi woofers are 2 ohms (40W), the Stereo woofers (6.5") are 4 ohms (15W in parallel with the door full range).

How much power/what amp to get?

A 2-channel amp with 150W-200W RMS per channel is ideal for the SWS-8's (2 ohms versions). However, you can easily power them with a more powerful amp as long as the gains are set properly/not too high. A monoblock amp can also be used as well but keep in mind which application you'll be using them for (mid-bass or bass).

Amp Settings?

Make sure the gain on the amp is all the way down before starting up the system. Turn up your head unit volume to about 3/4 loud. Turn the gain up slowly until you hear distortion and back off a few clicks. You should run the gain low for a week or two to break-in the subs. The factory L7 amp low passes the sub outputs at around if you're just swapping out the underseats and not adding a trunk sub, you don't need to set any filters...maybe a subsonic filter at around 30Hz.


Spacers are needed between the SWS-8s and the factory underseat enclosures in order to provide enough clearance for the slightly taller SWS-8s. < This is a must! Another spacer can be placed between the grill and the carpet. Some leave the grill off and others just use the spacer. Some even put the spacer and the grill under the carpet. In some situations, the spacer and grill need longer screws to secure them to the enclosure. (e.g. The spacer is on top of the carpet and then the grill is placed on top of the spacer.) You can either make your own or buy a set from one of the member on the forums.

The are also other methods like the following:

Originally Posted by 808MGuy View Post
I did the trimming the ribs method as well as installed a foam/rubber gasket between the enclosure and the SWS. That lifted it up enough for me not to have to use a spacer.
This has been covered on the forum so please search.

Power and Ground?

Wire them directly to the battery with an inline fuse rated for your amp.

REM or Remote Turn On Lead?

A good LOC with a remote turn on trigger will eliminate the need for a REM wire. However if you need to run a REM wire (in the L7 system only), it will need to go up to the head unit. There is no REM lead in the trunk for the L7 system like the other systems have.

Member "Technic" has summed up this answer very well in another thread:

Pin 13 in the back of the OEM HU is the remote wire in all the OEM systems. Pin 10 is the exact same wire but at the OEM amp connector in the non-Logic7 system. Sometimes the wire will work directly with aftermarket amps, sometimes a 12V relay will have to be used -with the OEM remote as the trigger- to turn amps on, all depends of the amp chosen.

(Technic, hope you don't mind me quoting you.)

Also I beleive Technic makes a harness so you don't need to cut any OEM the amp. Just plug and play.

Also if your amp accepts high level inputs, you can tap the outputs from your stock amp and wire them directly to your amp. Make sure setting are set correctly....signal level high, signal sensing on, etc.

Which wires to tap?

I tapped the sub outputs of the L7 system at the amp end as per this guide:

Update: Other systems require different wires to tap...just follow the guide. In general, you'll want to tap the sub wires. I believe the Standard system has a Full Range signal going to the rear deck speakers so for that system, tap the rear deck speakers.

Why do the side skirts rattle with the new SWS-8 upgrade?

The underseat enclosures are "ported" into chambers within the side skirts. The enclosures are "sealed." The increased movement of air from the more powerful SWS-8s create the rattling effect. Nothing can really be done about this. You could try blocking off the ports, however you will lose significant space and therefore decrease sound output. In short, blocking the ports is not recommended.

Useful Links:
SWS 8 upgrade with MTX amp
The DIY I followed to install my SWS-8s.

FULL SWS-8 sub and amp install, 34 pictures, step by step
Another DIY

Ultimate Subwoofer Installation Guide (Instructions inside)
Great breakdown of OEM amp wiring harnesses.

"Short review: Custom Earthquake SWS-8 / SWS-8x spacers"
These are the spacers I used.

Logic 7 specs
PDF attachment in 2nd post.

Last edited by fdriller9; 10-12-2010 at 12:13 PM.