[Billfitz]

Very low frequencies have little difficulty passing through seats, or anything else for that matter. That's why when you hear a teenage doofus pass by playing his system loud enough to be heard in the next county it's only the low bass that is heard.

[johnung]

Originally Posted by pierreye

If you found certain speakers you like and able to fabricate the mounting, go ahead and try it out. As you said, different person had different taste. Personally, I like vocal and airy sound, so I feel Scan Speak D3004 and 4424F/10G meet my requirement. I think your setup going to be more complex than what I have done so far and can't wait for your feedback.

You are right that stock Top Hifi is a bit underwhelm compare to higher offerings such as B&W system in latest Volvo. But for budget upgrade, I would keep the amp and just upgrade the underseat woofer and speakers with at least 2nd order crossover. This is the biggest jump in audio fidelity for me. Next if you have fold down back seat, you can install a trunk sub for lower bass. As I do not have a fold down seat which will have problem for the bass sound to penetrate into the cabin, I forgo this idea.

I don't know how much if anything has changed from the F series models to the G series models in terms of underseat subwoofers. F3x underseat sub boxes are limited in size which limits the ability to just drop in any aftermarket speaker, no matter how expensive it may be, and achieve an improvement.

The Earthquake subs use a different design that permits them to achieve a measurable performance improvement in those BMW sub boxes, but only when driven with up to 150watts/channel RMS. So a secondary amplifier is also needed to drive the upgraded underseat subs. I also used a $50 harness from Technicpnp which made the installation clean, risk free and reversible. I used an AudioControl amp that perfectly handled the HK 40volt speaker level outputs while providing two 150/watt channels that were needed.

Like I said, not sure if they made changes to the underseat subs & boxes in the G, but maybe this info from the F might help.

[johnung]

Originally Posted by johnung

I don't know how much if anything has changed from the F series models to the G series models in terms of underseat subwoofers. F3x underseat sub boxes are limited in size which limits the ability to just drop in any aftermarket speaker, no matter how expensive it may be, and achieve an improvement.

The Earthquake subs use a different design that permits them to achieve a measurable performance improvement in those BMW sub boxes, but only when driven with up to 150watts/channel RMS. So a secondary amplifier is also needed to drive the upgraded underseat subs. I also used a $50 harness from Technicpnp which made the installation clean, risk free and reversible. I used an AudioControl amp that perfectly handled the HK 40volt speaker level outputs while providing two 150/watt channels that were needed.

Like I said, not sure if they made changes to the underseat subs & boxes in the G, but maybe this info from the F might help.

Photos that failed to attach to previous post

[Billfitz]

Originally Posted by johnung

I don't know how much if anything has changed from the F series models to the G series models in terms of underseat subwoofers.

They're not the same, but they're not all that different either. Modified to fit the different sheet metal of the G20, but otherwise very familiar. https://www.realoem.com/bmw/enUS/sho...diagId=65_3141

The Earthquake subs use a different design

The basic design of the Earthquakes, and pretty much every other replacement, isn't all that different, being dictated more than anything else by being able to fit into and work within the enclosure. Where the Earthquake differs the most is in the resonant frequency of the driver, which allows it to go lower. It's really a simple modification, you mainly just make the cone heavier. The trade off when you do so is a loss of sensitivity, so with the same voltage input it won't be as loud as a driver with a higher resonant frequency (Thiele/Small parameter Fs). That's why it needs a higher power amp to get out of it what it's capable of. By the same token there are drivers that have a higher Fs than stock, which may allow them to be louder than stock without any change in the amplification. However, that additional loudness comes at the expense of how low they'll go. How this works is summed up by Hoffman's Iron Law.

[pierreye]

If I go for trunk sub, it’s better to get higher sensitivity underseat sub for better mid bass punch. It depends on what u want to achieve. My measurement in X3 show that the stock underseat sub sensitivity is not match to my speakers and trunk sub. I need to boost the underseat sub by +3db and set all my speakers by -5db to equalize the FR. At higher volume, the underseat sub will no longer able to keep up with the rest of the system. Note that this is driven by UP 7BMW 150w sub channel. I would suspect SWS Earthquake would not be a good match in my application. You can check some previous installation on Earthquake with trunk sub coming to the same conclusion. Lack of mid bass punch.

[Billfitz]

In your case you'd want to be looking for an under seat with an Fs of 60Hz or higher. The Ground Zero 200 BMW 2 ohm is one example. It doesn't go as low as OEM but has higher sensitivity above 60Hz. Of course you need 2 ohm capability. They make a 4 ohm, but Fs is 54Hz, so it's not as good above 60Hz.

[pierreye]

Yes. That’s the model I get to replace the underseat sub. If I have time, will try to measure the driver vs HIFI driver at multiple SPL for more scientific conclusion.

[GeorgeR]

Illusion Audio has started shipping a new version of the Carbon C8-W Midbass Driver.

I had planned on using Jenhert XE200 8” drivers for my under-seat upgrade but they are no longer available, at least in the USA.

My searches kept coming up with the Audio Development W800NEO and the Illusion Audio C8 as top performers, even though I could find few examples in BMWs' under-seat location other than JimmyDee's W800NEO. He posted on this forum about his 440i upgrade and while his thread doesn’t mention it, he has since changed the Jehnert’s out with AD W800NEO’s, sold his 440i and bought an X6M where he is also using the AD W800NEO.

Previous versions of the C8 modeled very well but it has not been available for some time. Hopefully someone will get a chance soon to test the newly designed C8 and my expectation is that it is at least as good if not better, although it is too late for me.

As luck would have it a new version of the C8 was just released and arrived the day I dropped my car off for installation. I don't have the specifications but understand both the flange and depth are about 1/4" smaller. The basket is different and the mounting holes are no longer recessed. They have also configured the speaker wire connection posts inside the basket so they don't add depth to the installation.

Musicar Northwest crafted a beautiful adapter ring and dropped it in and I have a few hours of listening so far. Hard for me to tell how the C8 is performing since it is now tuned as part of new speakers in an 8-speaker active front stage, plus the rear stage and subwoofer, external amps and DSP but overall the system sounds fantastic.

Do a search of Audio Development W800 NEO, Illusion Audio C8-W or C8 and you should be led to hits like the two below.

Stevens Audio MB8 & Illusion Audio C8

Comparing Audio Development W800NEO & Illusion Audio C8 Physicals


Not inexpensive options, not direct replacement, in other words requires some work to get them to fit, but options non the less in the spirit of the thread. I was drawn to them based on reviews in car audio circles, both competitors and enthusiasts, and while they were typically installed in doors, were highly recommended.

[eleven11]

Originally Posted by GeorgeR

Illusion Audio has started shipping a new version of the Carbon C8-W Midbass Driver...

Thanks for sharing. New options are always a good thing. Let us know your impressions after more time.

I recently consulted with Musicar, also. Similar to your story, the Jehnert is no longer available (or, at least for now). They suggested the Audison APBMW S8-2. I installed a pair this weekend, but have only listened for less than 10 minutes. So far, it seems the general loudness/kick is non-inferior to OEM, and perhaps less sluggish.

[GeorgeR]

Originally Posted by eleven11

Thanks for sharing. New options are always a good thing. Let us know your impressions after more time.

I recently consulted with Musicar, also. Similar to your story, the Jehnert is no longer available (or, at least for now). They suggested the Audison APBMW S8-2. I installed a pair this weekend, but have only listened for less than 10 minutes. So far, it seems the general loudness/kick is non-inferior to OEM, and perhaps less sluggish.

Musicar recommended Audison for my X6 as well after learning they couldn't get Jehnerts anymore. I would trust them over most anonymous internet"experts" but I did research the best I could and Musicar humored me and agreed to install the new form factor C8's. They may have received the first pair off the boat. I'm sure the Audisons will sound great.

[Billfitz]

The original C8 response and sensitivity is virtually identical to the OEM Hi-Fi woofer. The two traces shown can hardly be told apart.



Driven by the OEM amp you wouldn't be able to tell the one from the other. The C8 will take more power, so it would go louder driven with a more powerful amp than stock. There's no data on the C8-W on the Illusion Audio site yet, so I can't compare it at this point.

[eleven11]

Originally Posted by Billfitz

The original C8 response and sensitivity is virtually identical to the OEM Hi-Fi woofer. The two traces shown can hardly be told apart...

Bill, thanks as always for the input. I've seen you reply numerous times about various speakers (especially subwoofers), often citing the need for TS values to compare through modeling software, etc. However, it seems your conclusion is often only about the relative loudness of speaker A versus speaker B.

I'm curious (as an audio layman), what we can determine about the other differences between these speakers, aside from just loudness (e.g. accuracy). Granted, these are "subwoofer" frequencies, with perhaps less opportunity to discern audio nuances. However, I think this becomes more important for those using the underseats as part of their midrange, when having a dedicated rear subwoofer.

Thanks.

[Billfitz]

Other factors are important once you get into the lower midrange, but that coincides with where the under seat woofers leave off and the door midranges take over. Many differences do exist between different speakers in the frequencies where the under seat woofers operate, but they are as much determined by the enclosure as by the driver contained within. Those differences that can be realized with a different enclosure aren't an option for us, so we're stuck with what the BMW enclosure allows.

As for using the under seats for higher frequencies than stock, that wouldn't work very well. The reason they can be placed under the seats is that the wavelengths they produce are long enough that they're not directionally locatable. Once you get much above 120Hz you need to have the drivers placed closer to ear level, without obstacles blocking the sound. That's the reason why the woofers are crossed over to the midbasses where they are. If you tried running the woofers even one octave higher it would cause problems with phase, time alignment, imaging and more.

[sunny_j]

+1
Thanks for all the info you share in this thread. I've learned a lot about under seat subs from reading this thread

[eleven11]

Originally Posted by Billfitz

Other factors are important once you get into the lower midrange, but that coincides with where the under seat woofers leave off and the door midranges take over...

Thank you for the reply and education.

When recently replacing my underseats (see above), I noticed that the OEM enclosure has a semi-sealed port/vent that runs laterally to edge of each respective door. I was not aware of this design, beforehand. However, it will come into consideration as I try to identify where these speakers are creating rattles at higher volumes (only appreciated outside the vehicle).

[Billfitz]

That vent allows the cavity it vents into to become part of the enclosure, increasing its size. Without that they wouldn't go as low as they do. The rattles heard outside the car are from vibrating body panels. You might be able to damp them with a vinyl mastic. I use this, which has the best damping to cost ratio:
https://www.amazon.com/Noico-deadeni...t%2C190&sr=1-3

[eleven11]

Originally Posted by Billfitz

That vent allows the cavity it vents into to become part of the enclosure, increasing its size.

I assumed that was the purpose. Thanks again.

I've secured some great butyl already, which I have extensively installed in my door panels. This seems to be in the region of the rocker panel and undercar - I'm planning to explore every nook and cranny.

[Billfitz]

You'd think the most likely area would be where the woofer vent fires into, but not necessarily. What's most easily vibrated by long wavelengths is large panels. The good news is that anything vibrating enough in the low frequencies to be heard can also be felt.

[damack]

Parts are on the way to upgrade the underseat subs in my F31. Thanks to all in the discussions in this thread and others. I went with the Earthquake SWS8xi, Polk Audio D2000.2 amp, Audiocontrol LC2i and TechnicPnp harness. The LC2i accubass feature interested me, not sure if I'll need it or not as I haven't seen any discussions on rolloff from the HK processing in the amp. I figure it's there if I need it. Everything should be here in the next week or so, enough time to plan out where it's all going. The F31 has a large empty area on the drivers side above the factory amp so that's where I'm thinking it'll go.

[jedi-knight83]

Billfitz apologies if its already been asked an answered... But in an F series car, if you are running a trunk sub, what would your suggested crossovers be to start at (and then fine tune obviously depending on the speaker)

At the moment I'm

Trunk Sub = 20Hz - 70Hz
Woofers = 70Hz - 150Hz
Doors = 150Hz - 20kHz with a passive cross to the tweeters at 4.5kHz

I'm not happy with my overall sound still. I still need to change my 4ohm Rainbow subs back to the 2ohm OEM HiFi subs to test that out and also want to try different door speakers with a lower passive cross.

As good as the up7bmw amp is for its adjustability as well, I wonder if its just not powerful enough in reality (it claims 65w rms). The vocals just don't seem to fill the front like they have on my previous audio install on a MK5 golf.

[jedi-knight83]

Originally Posted by johnung

I don't know how much if anything has changed from the F series models to the G series models in terms of underseat subwoofers. F3x underseat sub boxes are limited in size which limits the ability to just drop in any aftermarket speaker, no matter how expensive it may be, and achieve an improvement.

The Earthquake subs use a different design that permits them to achieve a measurable performance improvement in those BMW sub boxes, but only when driven with up to 150watts/channel RMS. So a secondary amplifier is also needed to drive the upgraded underseat subs. I also used a $50 harness from Technicpnp which made the installation clean, risk free and reversible. I used an AudioControl amp that perfectly handled the HK 40volt speaker level outputs while providing two 150/watt channels that were needed.

Like I said, not sure if they made changes to the underseat subs & boxes in the G, but maybe this info from the F might help.

So you are running another amp to boost the already amplified output?

[Billfitz]

Originally Posted by jedi-knight83

Billfitz apologies if its already been asked an answered... But in an F series car, if you are running a trunk sub, what would your suggested crossovers be to start at (and then fine tune obviously depending on the speaker)

At the moment I'm

Trunk Sub = 20Hz - 70Hz
Woofers = 70Hz - 150Hz
Doors = 150Hz - 20kHz with a passive cross to the tweeters at 4.5kHz

The trunk sub doesn't need to go that high, I'd go between 50 and 60Hz. 120-130Hz to the doors is pretty good. The up7bmw amp has enough power when you've got a trunk sub doing all the heavy lifting. Vocal intelligibility wouldn't be aided by more power anyway. EQ boost in the 500-2kHz region should help there. I'd do a lot more with EQ before investing in more speakers that probably won't make much difference. If you're really serious about your sound a better investment would be in testing gear, like this:
https://www.parts-express.com/dayton...ystem--390-792