How to Improve OE Sub Bass Quality and Eliminate Vibrations

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Question about the dynamat on the trunk floor: it sounded like this reduced road noise (hurray!), but I am curious if it makes it harder to hear the stock exhaust?
I've used and found that with Dynamat you'll definitely experience less vibration and rattles. That said it seems to have had little to no impact on exhaust noise levels...
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Hey Everybody,

I just wanted to share with everyone what I did to improve the bass in my MkV. Its not meant do be a DIY, just some pics and info on what I used and a brief description on how I did it.

I ended up removing the OEM subs and replacing them with some shallow mount 8" subs from Pioneer. I searched high and low for subs that had the shallowest profile and low cuFt requirements. I ended up coming across the 8" Pioneer TSA2000LD2 subs. Their profile was shallow enough to fit in the enclosures and only required 0.15-0.5 cuFt of space. I know these Pioneers aren't the greatest subs, but for me it was all about retaining the OEM enclosures and keeping everything looking OEM. I used a Kicker Key 500.1 amp to power them and tapped into the stock sub inputs for the signal.

The results are pretty good and sound way better than the stock subs. The lower range is drastically improved and the overall sub output is way louder. Here's a list of the major parts I used with some pics to summarize the install.

Parts:
Pioneer TSA2000LD2 Subwoofers (qty 2) - Pioneer Subs
Kicker Key 500.1 Amp - Kicker Key Sub Amp
Kicker 4 gauge Amp kit (46PK4) - Amp Kit
Kicker Bass knob (46CXARCT) - Bass Knob
12 gauge speaker wire - Speaker Wire
Install Gear 4/8/10 Distribution Blocks - Distribution Blocks
Rubber foam tape, 9/16" thick - Foam Sealing Strips
22 gauge wire for remote turn on
Lexan Board for amp mounting
Posi-taps
Add-a-fuse
Tessa Tape
Cable Ties

Install:
-Step 1-
Cut out OEM subs from the enclosure. I literally cut the fabric cone out and left the flange that mounts onto the box. This was the only way to maintain an air tight seal between the sub and the box.




-Step 2-
Using the thick rubber foam striping, line the flange where the OEM sub used to sit. This will allow for an airtight seal between the new sub and the enclosure box.




-Step 3-
Now here's the risky and somewhat "ghetto" part of this install.... For the perfectionists out there, this method probably isn't going to work for you, but I didn't have any other means to get it done. In order to get these Pioneer subs to fight into the oddly shaped enclosure, you're going to have to cut the sub mounting flanges into straight sections. I used an oscillating / reciprocating saw with a high quality metal cutting blade to get this done. It doesn't look pretty, but its not something you can see because their covered by the grilles. At the end of the day, it got the job done and that's all I cared about.




-Step 4-
I used 6 screws on each sub to mount them to the OEM box. You'll have to screw them in at a bit of an angle in order to catch onto that flange you cut out of the stock subs. After they're screwed in, I made sure they were air tight by pressing the bottom of the enclosure to a table (where the green seal is) and pressing on the sub. If their was resistance on the sub and no air leaking out of the circumference of the sub...youre good.




-Step5-
I wired these 2 ohm DVC subs in series, and then both subs in parallel at the amp which gives you an overall load of 2 ohms. The speaker wires were ran down the bottom of the enclosure and out of the ports where the actual bass comes out of. I tapped the stock sub wires with posi-taps and then ran everything over to the drivers side following the OEM harness. The distribution blocks linked above are where I made the connections between the subs and the output of the amp.






-Step6-
Mounted amp, distribution blocks, wiring, bass knob cable, etc to the Lexan board I cut. I mounted the board to a threaded post that was welded on the body of the car. I ran the power and ground cables to the battery, and 22 gauge remote turn on wire to rear passenger side fuse box (fuse 207). Fuse 207 is an extra unused fuse that turns off 5 seconds after you turn the engine off.





Like I said....this wasn't meant to be a total DIY. I wanted more to just share with you guys the general ideas I had to replace the stock subs with better ones while maintaining a totally OEM look. Maybe this will give others some insight on trying to do something similar with possibly different / better equipment or ideas. If anyone has any questions on how I did something and wanna try this for themselves....just send me a message and I can try to help you out.
 
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^^ Nice job! :thumbsup:

One suggestion...I think it would be a good idea to start a new thread in the Audio Section for this writeup for others to see and comment on your particular audio setup...

-------------------------
Side note:

And as I mentioned several times within this thread the Harmon Kardon OE subs are actually quite good and not really the problem here...In other studies done in the BMW forum by a few audio enthusiasts / professionals it was surprising to find in side by side comparative tests that the HK OE subwoofers actually performed much better than most shallow mount competitors!

Underseat Woofer Comparisons.jpg


I actually tried replacing the subs after modification with Bavsound Ghostsubs and was extremely disappointed and ended sending them back since there was really no major improvement in sound quality!

Bavsound Ghostsub Review: I really wanted to like them...

That said, I've always said that installing a dedicated amplified sub to the system, high pass crossovers to the existing HK woofers @ ~200hz (utilizing them as mid-bass woofers) would be the best low cost / high quality solution for the existing system...This would also effectively increase headroom of the HK OE amp as well since power below 200hz would no longer necessarily be drawn from the OE Amp...

This is my next step and will create a new thread when completed...
 
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I did it! Thanks for the awesome guide and for answering questions. Definitely sounds noticeably better too.

IMG_0375(1).jpg


Attaching some extra photos I took while progress:

IMG_0366.jpg
IMG_0367(1).jpg
IMG_0368(1).jpg
IMG_0371(1).jpg
nicely done! :thumbsup:
 

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^^ Nice job! :thumbsup:

One suggestion...I think it would be a good idea to start a new thread in the Audio Section for this writeup for others to see and comment on your particular audio setup...

-------------------------
Side note:

And as I mentioned several times within this thread the Harmon Kardon OE subs are actually quite good and not really the problem here...In other studies done in the BMW forum by a few audio enthusiasts / professionals it was surprising to find in side by side comparative tests that the HK OE subwoofers actually performed much better than most shallow mount competitors!

Underseat Woofer Comparisons.jpg


I actually tried replacing the subs after modification with Bavsound Ghostsubs and was extremely disappointed and ended sending them back since there was really no major improvement in sound quality!

Bavsound Ghostsub Review: I really wanted to like them...

That said, I've always said that installing a dedicated amplified sub to the system, high pass crossovers to the existing HK woofers @ ~200hz (utilizing them as mid-bass woofers) would be the best low cost / high quality solution for the existing system...This would also effectively increase headroom of the HK OE amp as well since power below 200hz would no longer necessarily be drawn from the OE Amp...

This is my next step and will create a new thread when completed...
Id be curious to see how they compared with theses Pioneers.

I understand the OEM subs were specifically designed for the space and type of enclosures that are in the car. But they just seemed really cheap and flimsy. Like they wouldn’t withstand the extra power from adding an additional amplifier. The subs weighed barely anything, the cone material seemed extremely cheap, and the size/weight of the magnets was laughable.

I understand that a lot of the poor base response is due to the OEM amp, but I just didn’t trust the OEM subs would handle additional power from a dedicated sub amp. Your idea of adding an additional subwoofer and using a bandpass on the stock subs is prob the best route, but it wasn’t the route I wanted to take. I value whatever space I do have in the hatch and didn’t want to loose any of it. I also didn’t feel like spending $2500 on something like the Oem Audio Plus system which I’m sure sounds great. But for $600, I got what I was looking for, and I’m totally happy with it. The lower bass notes are now present and the sound quality has greatly improved. Plus I have confidence these subs will hold up over time and I won’t have to worry about replacing anything in the future.

Thanks for your detailed response to my post and all you have contributed to this forum. I’ve used lots of information you’ve provided on here a bunch of times and it’s highly appreciated.
 
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Id be curious to see how they compared with theses Pioneers.

I understand the OEM subs were specifically designed for the space and type of enclosures that are in the car. But they just seemed really cheap and flimsy. Like they wouldn’t withstand the extra power from adding an additional amplifier. The subs weighed barely anything, the cone material seemed extremely cheap, and the size/weight of the magnets was laughable.
Once you resolve all the other design enclosure issues that I outline in the first post the HK sub's actually sound pretty decent and will handle quite a bit of power...What I've learned over the many many years of doing this (yeah I'm old...ha!) is that the quality of performance isn't necessarily measured by weight or magnet size...They might not be pretty but I assure you the HK woofers are robust and are built surprisingly well...

One of the issues is that the current subs are being tasked to handle far too much range / bandwidth...With some of my past test analysis I've done it showed that the operating range of the OE subs is fairly wide 50~500hz... Like I mentioned earlier by simply adding 12db 8 ohm high-pass cutoffs (150~200hz) to the current OE subs (making them mid-bass) will free up more OE amp power and also allow the OE "midbass" woofers to operate far more efficiently...Then add a line converter and powered subwoofer (<200hz) and your done...Shouldn't cost any more than $800...I'm currently considering the JL Audio 400W powered 10" sub...

Finally, yeah, I could spend thousands on upgrading the system, but there quickly reaches a point of diminishing returns and as a Engineer the fun is also doing the work myself and finding pragmatic simple solutions to problems...Been down this rabbit hole far too many times in my younger days...I have to still remind myself that the weakest link in any audio system is the human ear...ha!
 
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Hey Everybody,

I just wanted to share with everyone what I did to improve the bass in my MkV. Its not meant do be a DIY, just some pics and info on what I used and a brief description on how I did it.
Awesome job! You should totally make a separate thread.

I love how how you used lexan/plexiglass for the amp mount. On my X3MC I used sheet metal - wish I had thought of the plastic route :)
 

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That said, I've always said that installing a dedicated amplified sub to the system, high pass crossovers to the existing HK woofers @ ~200hz (utilizing them as mid-bass woofers) would be the best low cost / high quality solution for the existing system...This would also effectively increase headroom of the HK OE amp as well since power below 200hz would no longer necessarily be drawn from the OE Amp...

This is my next step and will create a new thread when completed...
I got passive crossovers for the HK "woofers" on my X3M but never installed them. I am looking forward to the writeup to see how you integrate as I wasn't crazy about cutting the wires to the connectors. 200hz seems a bit high, I like to keep my subs 80hz and below but that is all personal taste.

One of the issues is that the current subs are being tasked to handle far too much range / bandwidth...With some of my past test analysis I've done it showed that the operating range of the OE subs is fairly wide 50~500hz... Like I mentioned earlier by simply adding 12db 8 ohm high-pass cutoffs (150~200hz) to the current OE subs (making them mid-bass) will free up more OE amp power and also allow the OE "midbass" woofers to operate far more efficiently...Then add a line converter and powered subwoofer (<200hz) and your done...Shouldn't cost any more than $800...I'm currently considering the JL Audio 400W powered 10" sub...
If this is the sub you are referencing, the dimensions are 18.5"W x 11.125"H x 5"D.

In what orientation would you place it? Flat on it's back or stood up behind the HK woofers?

Trying to convince my gf to get a powered sub but she needs the space for groceries and Costco runs :)

I wish they made a powerful small sub which could be tucked away in one of the corners behind the taillights.

My X3 has 75% of the truck taken up by my JL Audio bandpass box with a 10" W7.

My formula Bass > Space ;)
 
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If this is the sub you are referencing, the dimensions are 18.5"W x 11.125"H x 5"D.

In what orientation would you place it? Flat on it's back or stood up behind the HK woofers?

Trying to convince my gf to get a powered sub but she needs the space for groceries and Costco runs :)

I wish they made a powerful small sub which could be tucked away in one of the corners behind the taillights.

My X3 has 75% of the truck taken up by my JL Audio bandpass box with a 10" W7.

My formula Bass > Space ;)
I plan to lay it flat and close to the rear...Looking from the back with hatch open I would also have it such that the side controls would be on left side closer to the Amp wiring....I wouldn't place it forward as I would not want to block the OE woofer exhaust ports...

It's only 5" high so really won't take up a whole lot of space and I'm not concerned with placing groceries on top sides and around the sub...I also not that big a power shopper...ha!

1634748561267.png
 

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I plan to lay it flat and close to the rear...Looking from the back with hatch open I would also have it such that the side controls would be on left side closer to the Amp wiring....I wouldn't place it forward as I would not want to block the OE woofer exhaust ports...

It's only 5" high so really won't take up a whole lot of space...
This hatch is so tiny I think anything is too much lol.

I was reading reviews on the JL and some people noted it was overpriced for what it was and not up to JL quality.

Curious what you end up with/how it works out - will be waiting patiently for the thread!
 
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This hatch is so tiny I think anything is too much lol.

I was reading reviews on the JL and some people noted it was overpriced for what it was and not up to JL quality.

Curious what you end up with/how it works out - will be waiting patiently for the thread!
The hatch it large enough for me with the box in it...And yeah, I saw a few negative
reviews as is the case with most reviews....Far more positive than the few negative comments though...I'm looking for tight deep base not a ghetto boomer...ha!
 

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The hatch it large enough for me with the box in it...And yeah, I saw a few negative
reviews as is the case with most reviews....Far more positive than the few negative comments though...I'm looking for tight deep base not a ghetto boomer...ha!
:D:D:D
 
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I got passive crossovers for the HK "woofers" on my X3M but never installed them. I am looking forward to the writeup to see how you integrate as I wasn't crazy about cutting the wires to the connectors. 200hz seems a bit high, I like to keep my subs 80hz and below but that is all personal taste.
Oh, I forgot to reply to this...

My reasoning for adding 200hz high pass crossovers is more about freeing up OE HK amp headroom and taking full advantage of the powered sub operating range...I want to dedicate the existing HK woofers strictly for upper-mid bass (200~500hz) operating range...As is, I think those HK OE woofers are operating over far too broad a range...

I see many folks are adding powered subs to their systems and not taking advantage of the fact that at least 1/4 of the power consumption of the HK OE amp is actually being used below 200hz...So, if you are going to install a powered sub in which it's range / capability is from say 50~200hz, then use it, and at the same time free up at the very least 1/4 of the power consumption of the existing OE amp...This is a for more efficient use of available power which should in turn result in a less distorted system sound output at higher power levels...
 

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One of the issues is that the current subs are being tasked to handle far too much range / bandwidth...With some of my past test analysis I've done it showed that the operating range of the OE subs is fairly wide 50~500hz... Like I mentioned earlier by simply adding 12db 8 ohm high-pass cutoffs (150~200hz) to the current OE subs (making them mid-bass) will free up more OE amp power and also allow the OE "midbass" woofers to operate far more efficiently...Then add a line converter and powered subwoofer (<200hz) and your done...Shouldn't cost any more than $800...I'm currently considering the JL Audio 400W powered 10" sub...
I agree the OEM subs are tasked with too high of a frequency range. I think this is what causes some of that weird distortion at lower to medium volume levels. Two dedicated 8" mid-bass woofers and one 10" low range woofer would definitely sharpen the overall sound of this system. It would have been awesome if they had made one woofer an 8" (mid-bass) and one a 10" (<120hz) to handle bass duties.

I have a 10" JL Audio W3v3 in the H.O. Wedge box I used in my previous car (Genesis G70), and it sounds phenomenal. I dont have any use for it at the moment but dont want to get rid of it because I love it so much. JL makes awesome products.
 

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Awesome job! You should totally make a separate thread.

I love how how you used lexan/plexiglass for the amp mount. On my X3MC I used sheet metal - wish I had thought of the plastic route :)
Thanks!
I covered the back side of it with sound deadening material as well for good measure. I definitely didnt want that rattling or making any unwanted noise after putting everything back together.
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