[squidlyboy]

Originally Posted by instalher

all of the drivers mentioned need airspace to work, model the theil small parameters on term pro and you will very quickly see they have horrific curves under 80 hz...

This is why i've always had a problem calling these underseats: subwoofers. They will never produce the same sound at the same frequencies as a proper trunk sub. Ever. These very flat/thin speakers have a very limited range for cone excursion, and the necessary enclosure space needed to generate that kind of sound is just not there. I don't know why there is a never-ending quest to turn a hammer into a screwdriver.

The best we can hope for is solid lower mid-range to upper/mid-bass. I get that people want to use the existing speaker/space under the seat, and don't want to mess with a leased car, or that you don't want to lose trunk space, but you'll just have to accept the fact that you won't get the perfect sound you are looking for. You set your priorities, accept the consequences, and live with your decision.

Its hard to tell from your pics, but is all that work to create a bigger enclosure happening under the seats? or elsewhere...

[HUGE3]

Another option is the Rockford Fosgate T3-BMW-SUB that are made to fit in the underseat enclosures. That is what I installed along with the PP82DSP. They are definitely better than the stock underseats, but like most others, I still ended up with a trunk sub.

[Slickz]

Still not happy with the stock Harmon Kardon subs in my new 340. It does not feel like there is any base! The previous Harmon Kardon I had in my X5 sounded much richer but the total 600W amplifier and number of speakers is supposedly the same as the 340. I read something online about the cone material in the Harmon Kardons needing to break in before you will get the true base, is that bogus? Heck even my Volvo had rumbling bass in the "Volvo premium sound" system and only geography teachers drive those.

[Lancelot]

Yes they definitely need to break in, at first very shallow sound but after 20h you get a vastly improved sound

[Kabrich]

Vastly improved still does not mean great bass with the HK System.

[Billfitz]

If you think a different driver in the under seat enclosures will make a major difference think again, as the laws of acoustics aren't on your side. At least as important as the driver is the size of the enclosure. For an explanation why google 'Hoffman's Iron Law'.

[m95roadster]

Originally Posted by Billfitz

If you think a different driver in the under seat enclosures will make a major difference think again, as the laws of acoustics aren't on your side. At least as important as the driver is the size of the enclosure. For an explanation why google 'Hoffman's Iron Law'.

From what I have seen in pictures, it looks like the enclosure is vented to the side sill. I'm guessing there's some flow resistance built into the vent to act like a variovent or aperiodic enclosure.

BTW, do you have a folded horn in your ride?

[instalher]

folded horn is like a 86 Camaro, hatchback and a box in the fish bowl, the sound radiates up and reflects off the glass gaining up to 3db of acoustic output, thus the response is similar to a folded horn design, Next those boxes I fiberglassed for under the seat of my bmw, they provide .5 cubic ft, and lots of depth, I am putting in a 3.5inch deep, peerless midbass driver in that box. Midbass is a critical aspect of any music, it adds depth, and emotion to any song, our cars give us tons of midrange but very weak midbass, hopefully changing from a tiny box, shallow 8, to a big box, big 6.5 driver, will solve this issue, again, if you own a iPhone, upload the program from jlaudio, $20 bucks and its almost as accurate as my audio control sa 5030 rta, if not grab any rta app, I have audio tool. works great... Always get a reference point befor you make any changes, play some dynamic music, Spanish Harlem, by Rebecca Pidgeon, upload and make it your bible track....lol.... run an rta and spl. with oem system, THEN you can start making adjustments... good luck guys.. text me if you need help...

[Billfitz]

Originally Posted by m95roadster

From what I have seen in pictures, it looks like the enclosure is vented to the side sill.

I haven't look at mine closely, but with an enclosure that small it's not possible to tune it very low anyway.

do you have a folded horn in your ride?

No, my trunk is for cargo. Carry a sub or carry my golf clubs? No contest. Besides, the only tunes that get played in my car are classic rock, for which the stock woofers are adequate.

[instalher]

classic rock is king.... lol... check out motley crue's dr. feelgood c.d. recorded in d.d.d. perfect for sq and it just hammers!!!

[Slickz]

The underseat HKs started to break in but the bass is still garbage. I'm springing for the Bavsound ghosts, mostly for convenience of plug & play. Also I like the 100 day free trial policy. We'll see how they do.

[Dang3r]

Btw...is there a DIY for the seat removal F32? Its more easier to install the subs...

[sureshrsv]

Originally Posted by DJWabbles

I have the MS 8B-BMW.2 along with the tweeters and the mid-range, the under seat subwoofer sounds amazing from the box it self but even better with a decent AMP.

I have the exact same setup with bimmertech amp. Can you please share your tune file?

I couldn't get the under seat sub woofer to sound.

[Soul_Glo]

Most the subs on the list have been installed by forum members. It would be good to add a link to those installs if you can.

[Billfitz]

FWIW if I was going to replace the woofesr it would not be with 'drop in' replacements. Looking under my seats it appears that you could use a standard driver installed facing down, leaving the vented covers off. The frame/magnet would stick up above floor level, but it looks like there's room enough so that it wouldn't interfere with the seat. That opens up the possibility of using much less expensive but very high quality drivers, for instance:
https://www.parts-express.com/dayton...-coil--295-508
That driver mounting scheme would increase the effective volume of the enclosure for better results. It's not something I'm interested in myself, but it's a viable option to investigate.

[sureshrsv]

Originally Posted by DJWabbles

I have the MS 8B-BMW.2 along with the tweeters and the mid-range, the under seat subwoofer sounds amazing from the box it self but even better with a decent AMP.

are you using bimmertech amp?

[djwoodyuk]

Reviving an old thread here.
Thinking of upgrading my stock Harmon Kardon subs with aftermarket, but I would like to use the OEM amp.
What are my options?
I like the look of Bavsound but not available in the Uk.
Can I use the SWS 8?

[Billfitz]

Originally Posted by djwoodyuk

Reviving an old thread here.
Thinking of upgrading my stock Harmon Kardon subs with aftermarket, but I would like to use the OEM amp.
What are my options?

It's simple enough, use WinISD or similar loudspeaker modeling software to model the results with various woofers, including the stock. Well, not so simple, since you need complete driver Theile-Small specs to do so, which you can't find for most replacement drivers nor for the originals.

[Littlebear]

Originally Posted by Billfitz

FWIW if I was going to replace the woofesr it would not be with 'drop in' replacements. Looking under my seats it appears that you could use a standard driver installed facing down, leaving the vented covers off. The frame/magnet would stick up above floor level, but it looks like there's room enough so that it wouldn't interfere with the seat. That opens up the possibility of using much less expensive but very high quality drivers, for instance:
https://www.parts-express.com/dayton...-coil--295-508
That driver mounting scheme would increase the effective volume of the enclosure for better results. It's not something I'm interested in myself, but it's a viable option to investigate.

Hi Bill,
I like the idea of using a good driver upside down, like wot you said. I know folks at tech talk like many Dayton drivers, & I haven't gone & measured under my seat yet, but that Dayton UM8 (& the RRS Daytons) look big, & crazy powerful.
Would you recommend any other drivers from this page?

https://www.parts-express.com/cat/su...%5D&PortalID=1

Thanks, Murf

[Billfitz]

The main considerations are driver size and using speaker modeling software to see how it compares to the stock drivers. It's easy enough to measure the specs on the stock drivers if you have the right tools; I could do it in about fifteen minutes. It's the time required to get it in and out of the car to do the measuring that keeps me from bothering, that and knowing that even with a better driver it would need a more powerful amp. I'm not so unhappy with how mine sounds to bother doing an upgrade, so I'm not going to be the one to measure the driver specs. That task should fall to one of the companies that markets an 'upgrade', to prove that their drivers really are upgrades.

[Tomo366]

Bimmer Tech just days ago came out with Alpha One Speakers that are Plug and Play I installed a set yesterday which included under seat woofers the sound is amazing!

[Billfitz]

They may be very good drivers, but one cannot tell by looking at their specs, because what's posted on their website are not specs. These are what spec data sheets look like:

https://www.parts-express.com/pedocs/specs/264-955s.pdf

https://www.parts-express.com/pedocs...ifications.pdf

https://www.parts-express.com/pedocs...spec-sheet.pdf