DB840 sub in LSI15's replace the stock 8"driver!!!!!

@aggie113

As Maxwell Smart says: "I missed it by THAT much."

I mean... If you're single with no kids... Magnets on the outside could be an awesome look, just make sure you reverse the polarity!

Funny responses are 2 years apart... That's carrier pigeon speed

Absolutely... As long as it sealed to the enclosure the preformance would be the same... The trick would be routing the wiring while maintaining the seal.

Again just need to reverse the polarity of the wiring

gp4jesus wrote: »

I believe the replacement driver’s bass “extension” is due to its lack of “boom.” The original was masking the same under use.
Original & replacement measure the same.

...which is my concern with stepping up to the MM842 and overpowering the balance of the lovely mids and highs. MM840 reviews go back to at least '09, so it was presumably available when the DB840 was determined by Polk's engineers to be the ideal upgrade. Implying they had that option on the table and decided against it.

On the other hand, maybe the MM makes the LSi15 a better all-around speaker if room EQ is available to account for the extra low end impact, but Polk didn't want to recommend something that had any such dependencies.

I attached a spreadsheet with small parameters or various Polk Audio car subs. Maybe you can match something fairly close to the db840. There was some conflicting info from various sources on the old Polk Audio site. I tried to note them in the spreadsheet.

After waiting for the mail to arrive quite late, I open the box to find that Amazon sent a DB842 and a MM842 instead of two DB842's. What are the odds, given the above dilemma of which of the two to go with?!

Now I have to decide which one to install... Or do I install both and answer the head-to-head question we're "all" wondering, then hope there's no hassle returning the one I choose against, seeing as it was their fault sending me a mismatch Qty 2? Either way, it'll sort of suck going back to, or staying, stock on one tower while waiting a week plus for the replacement.

Well we know why we didn’t get a response before

Before opening the MM may want to see if Polk can verify or send you the dimensions for the driver

Sorry to hear

I came up with one semi-plausible explanation for the discrepancy: As mentioned a few posts up, my grills are the apparently less common type that screw onto the back of the wood side trims, rather than being pressed in from the outside. It seems unlikely that that setup would correspond to a different size cutout (and presumably different size woofer, unless it's a loose fit in a bigger cutout on others), but it would be interesting to see cutout measurements from people with the regular grills.

txcoastal1 wrote: »

Open a new thread, may get some attention

Will do. In the meantime, I took @VR3 's advice and tried out an inverted woofer mount. I had some old Sounstream SS8's lying around that just happen to be 4 ohm SVC, the exact same diameter as the stock driver, and 4 of their 8 holes line up. They just needed a little outward ovaling of the holes to hit the cabinet's holes.

Since I had the stock woofer out already, and had taken the pedestal off to make it easier to push out, it was trivial to extend the wires out through the port for a trial. I didn't want to conclude the day empty handed.

The improvement is quite pronounced in the chest slam region, even though it isn't sealed at all. (There's actually quite a bit less air coming out of its port than there is on the other tower with stock woofer. The rest is probably leaking around the thin, raised lip that has no gasket.) It's also a bit small of a cabinet for the SS8, even without their driver displacing VAS. I have to think an inverted mount of a properly sized driver, and a good seal, would be quite a winner! I also think the stock woofer must have been a standard O.D. for its day, given that the Soundstream is an exact match.



Also, here's a direct overhead shot (as opposed to a misleading angled perspective) of how minimal the overlap is between the inner cutout (baffle) and port. It would take a plumb bob to get an actual measurement, as I'm guessing it's less than 1/8". So, any deep magnet'd driver will drop in just fine with no overlap. VAS is the only issue there.

Here's a better indication of what the inverted sub mount looks like on the Right speaker, with wood trim in place (the Left's wood trim is sun faded and needs some stain applied):



I'm liking that approach, but the SS8 subs aren't particularly high power handling, so they're probably not a long-term solution. So, I decided to keep the MM842 and figure out how to make it work... (The DB842 appeared to have been an Open Box item, sold as New -- no tape on the outer box, tape removed and set aside on the inner packaging -- so I felt that one should be returned, regardless. They managed to screw up both halves of that order.) Its beefy all-black basket will also look a lot better inverted.

I measured the depth of the baffle and it's exactly 0.25", which makes it easy to match without planing. As soon as the weather clears, I'll go look for supplies to make a trim ring that depth. My router circle jig should be able to get the inner and outer diameters right.

Maybe ask for Kim Jasper, he's an original and knows his stuff.