repost of above with additional info. I know how frustrating it can be if things are not buttoned down real tite.
I bought the Polk Audio DB840 8" replacement speaker that is suggested in Youtube videos to replace the OEM Mark Levinson subwoofer. There is some discussion about replacing a Mark Levinson speaker with an aftermarket speaker. I went with the Polk($54) and it sounds fine. Does is sound as good? I couldn't say because the ML blown subwoofer was blown for a year before in replaced it, so its not like I could recall what the thing sounded like with the ML subwoofer. I installed the Polk subwoofer and it sounds fine, maybe great. That's very subjective. But it does sound like a high quality sound system and works fine.
Interesting comments by others suggest is that the price of the Mark Levinson is in the design and not the hardware. Old ML speaker weighs much less than the Polk but does not seem to have any distinguishing or different features from ML.
Thus ended that debate for me. Polk ($54.00 ) vs. ML(used -$300.00 - minimum) . Polk won.
R&R pretty simple. If, by the time you read this , youtube videos are still around, they can walk you thru it. One video has you removing the rubber ring around new Polk speaker, one has you keeping it. I kept it and modified the plastic bracket that goes BELOW speaker and allows speaker to seat properly on car deck.. This is the bracket that is bolted onto your rear deck . I secured the speaker with 3 little screws drilled into the plastic. There are holes in the rubber ring, so just line up with several of these holes and drill out a pilot hole Frankly you can secure the Polk speaker to the plastic bracket with self taping sheet metal screws. It is not a big deal. Don't be scared like I was. Don't let these screws be too long as they will hit the metal rear decking of car. Otherwise any little screw will suffice. The other plastic bracket that is attached to ML sub woofer assembly is no longer needed.
to restate: you throw away one of 2 ML brackets and use only the bracket which screws into car rear deck. Drill new holes thru existing holes in Polk speaker rubber ring and into plastic bracket to secure speaker to this bracket. I only used 3 screws. Like someone said this will only be critical if you roll the car.
The other thing you should do is jump the speaker itself. Why? I dunno but the youtube vids make a convincing argument. Something about 8 v 4 ohms and the receiver and other stuff. Again I don't know the acoustics behind all that, I simply did as they suggest. Worked fine. In short you connect a jumper between one set of connectors on the Polk using speaker wire. Using speaker wire, one strand goes from + to - at connector post. Connect the wires in the connector harness of old ML to the connector post on the Polk, , red wire goes to + connector post , and to black wire goes to - connector post.
R&R of seats and trim pretty simple. Rear seat bottoms disconnects by prying up. Back of seats are bolted to frame. Quick and easy. 5 bolts , 3 at bottom , 2 at top behind round caps at head rests. Then remove all the trim that prevents you from removing the cardboard rear deck and accessing the speaker. These are mostly connected with those little plastic push pins .Unbolt plastic bracket holding the subwoofer.
When done pat yourself on the back and have a beer. You just saved yourself $700.