Guide: 2nd Generation CX-9: Bose subwoofer improvement

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Texas
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'19 MX-5, '20 CX-5
I must be completely deaf or the CX-5 ≠ CX-9 because I think my '20 CX-5 sounds very good. Granted, it's not as good as the 16-speaker ELS 3D Studio system in my '19 RDX, but the Mazda doesn't have nearly as many problems as the Acura did. ;)
 

sm1ke

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Canada
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'18 CX-9 Signature
I must be completely deaf or the CX-5 ≠ CX-9 because I think my '20 CX-5 sounds very good. Granted, it's not as good as the 16-speaker ELS 3D Studio system in my '19 RDX, but the Mazda doesn't have nearly as many problems as the Acura did. ;)

The CX-9 does have more cabin space to push sound through, and I'm sure the acoustics are also different. I have not sat in a CX-5 to compare, so it's quite possible that the CX-5 sounds just fine the way it is. You could still do this mod to the CX-5's Bose subwoofer and it would result in the same improvements, but the improvements may just be less noticeable.
 
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2019 Mazda CX-9 Signature
the way you cut the sound deadener is really good, I don't think I will be able to do this way.

Do you think just adding the poly-fil would make a significant difference?
 

sm1ke

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Canada
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'18 CX-9 Signature
the way you cut the sound deadener is really good, I don't think I will be able to do this way.

Do you think just adding the poly-fil would make a significant difference?

Lol yeah, I had some extra time so I really took my time with it. But you could just cut bigger pieces instead of cutting a bunch of smaller pieces like I did. Just be sure that you don't cover the screws, the center hole, or the port on the side.

A bunch of people have only done the polyfill and reported that they did notice a difference. You could try adding polyfill first, then testing to see if its good enough. If not, you can buy some sound deadener and apply it. If you're still not happy after that, there are some aftermarket spare-mounted subwoofers available that you could probably upgrade to, but I haven't looked into those yet.
 
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2019 Mazda CX-9 Signature
Lol yeah, I had some extra time so I really took my time with it. But you could just cut bigger pieces instead of cutting a bunch of smaller pieces like I did. Just be sure that you don't cover the screws, the center hole, or the port on the side.

A bunch of people have only done the polyfill and reported that they did notice a difference. You could try adding polyfill first, then testing to see if its good enough. If not, you can buy some sound deadener and apply it. If you're still not happy after that, there are some aftermarket spare-mounted subwoofers available that you could probably upgrade to, but I haven't looked into those yet.
thanks for your response

I fill the empty space with polyfill and I do certainly notice a difference.

Now I worried the amplifier, with all the polyfill stuffed around it, I am afraid it may overheat
 

sm1ke

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Canada
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'18 CX-9 Signature
thanks for your response

I fill the empty space with polyfill and I do certainly notice a difference.

Now I worried the amplifier, with all the polyfill stuffed around it, I am afraid it may overheat

The polyfill should not be packed tightly, just enough to fill most of the space. I can actually press the fill straight down and feel the bottom of the sub. Because it isn't packed so tightly, the air is still free to move around the sub. There should be no issues with overheating - if there are, it is likely due to a manufacturer defect in the wiring, amp, or sub.
 
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Texas
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'19 MX-5, '20 CX-5
Now I worried the amplifier, with all the polyfill stuffed around it, I am afraid it may overheat

There's no amplifier in the enclosure - just a speaker with two wires connected to it. The amplifier is mounted elsewhere in the vehicle.
 
Is there a rule of thumb for how tight to secure the holddown bolt for the sub/sparetire? I removed both the other day to install some trailer wiring, and it didn't seem like the bolt was that tight. When replacing, I just tightened until the sub felt nice an snug, and didn't want to over tighten and break something.
 
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2016 Mazda CX-5 GT w/ Tech
If it’s this easy to improve the sound, why didn’t they just do it at the factory? And I thought Bose was trying to improve their name
 
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2018 CX-9 SIGNATURE
If it’s this easy to improve the sound, why didn’t they just do it at the factory? And I thought Bose was trying to improve their name
Bean counter: a person involved in corporate or government financial decisions and especially one reluctant to spend money
 
Anybody try plugging the port??
I filled the enclosure with recycled denim the other day and there certainly was a noticeable improvement.
However, I do think I'm hearing some port chuffing at higher volume.
Maybe I'll give it a try.
Bose really did half-ass this subwoofer.
 
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2020 CX5 Signature
New 2020 Signature here; the modifications to the subwoofer attached to the spare tire seem easily do-able. The Parts Express damping sheets come in two sizes: 10"x13" and 27"x40". What size sheet would I need to purchase?
 

sm1ke

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Canada
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'18 CX-9 Signature
New 2020 Signature here; the modifications to the subwoofer attached to the spare tire seem easily do-able. The Parts Express damping sheets come in two sizes: 10"x13" and 27"x40". What size sheet would I need to purchase?

One 10x13 sheet should be enough to do the most important part - the top of the sub. I only put material on the other surfaces because I had extra.
 
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2018 CX-9 GT
Revisiting this. I still get a very powerful bass response, even at lower settings. It's not boomy, but it's fairly strong even at 1 or 2 setting. Has anyone swapped out a different sub-woofer for the Bose? Wondering if a higher-quality speaker would make a difference (or not!)... Thanks.
 

klwdallas

2019 Pearl White Touring with Premium Pkg
I did this mod just now. I may be imagining it, but I think it sounds better. Tighter bass as others have said.

The enclosure isn't quite as bad as I expected based on what I read here. Some parts of it seemed really thick and there were lots of curves and reinforcements added. I focused on putting the deadening material on the parts that seemed thinner and on larger, flat areas. I didn't use as much deadening material as shown. I can always add more.

The enclosure was so stuck to the spare tire with some rubber ring that I wasn't sure what to do at first. Just rock it

(I'm surprised you have to remove the enclosure to change the tire. This process taught me how to remove the spare before I needed to know, which is a side benefit.)

Thanks for creating this guide.
 
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Florida
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2021 CX5 Signature
Would this process work for the subwoofer in a CX5 also? The sub is mounted in the spare under the rear floor.
 

sm1ke

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Canada
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'18 CX-9 Signature
Would this process work for the subwoofer in a CX5 also? The sub is mounted in the spare under the rear floor.

Yes, the procedure should be very similar between the CX-9 and the CX-5.
 
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CX5 GT
It is exactly the same for the cx5. I tried it but can't find any difference. May be the smaller interior of the CX5 plays a role. One big issue to me is that the 'floor' of the trunk is practically bare metal. Mazda did not put any sound deadening material at the back on those cars. Nothing below the trunk as well.
 
This is a DIY guide that details how to reduce the "muddy" bass from the Bose subwoofer mounted in the spare tire. This fix has been done by many others on this forum (originally jgriffter, followed by PTguy, jmeitz, Zoom49, greggmischenko, and others). I recently did the same mod, and I just thought I'd document and organize it to show how easy it is to do.

This process was photographed by myself, using my cellphone camera, my old DSLR and my 2018 Mazda CX-9 Signature as the "demo" vehicle. While the instructions are written by me, many references will be made to the various posts from the users named above. This DIY is provided as a learning aid and reference guide. I assume no responsibility for any warranties this process may void, or damages you may inflict on yourself or your vehicle.


What you'll need:

- 21mm socket or wrench (or the tire iron from the emergency jack kit)
- 1/4" socket
- Sound deadener
- Poly fill (pillow stuffing)
- Box cutter, scissors or Xacto knife


From jgriffter's original thread:





For the sound deadener and poly fill, PTguy recommends Parts Express.

I personally used three sheets of 10mm thick, 20x12" deadener from eBay, but if I had to do it again I would spend a bit more and buy the deadener from Parts Express. The adhesive on the eBay deadener isn't very strong, and the thickness makes it a bit harder to work with. For poly fill, I pulled some out of an extra guest pillow I had lying around. Since the guest pillow wasn't used much, the poly fill in it was not compressed, which was perfect.

1. Remove the subwoofer from the car by unplugging the harness (1) and loosening and removing the 21mm bolt (2) that mounts the sub and spare wheel to the car.

2. Remove the 7 1/4" screws (3) on the top cover (4) and set them aside.




3. Remove the 4 1/4" screws (5) securing the speaker (6) to the housing (7).

4. Fill the housing with poly fill (8). It doesn't need to be packed in, just lightly fill it. Screw the speaker back into the housing.




5. Apply sound deadener (9) to the outside of the housing. I forgot to take a photo, but I also applied deadener to the flat surfaces around the speaker.




6. Apply sound deadener to the top of the cover (1O), then screw the cover back onto the housing.




7. Reinstall the subwoofer. Don't forget to plug the harness back in.

Here's the finished product.




Here's jgriffter's thoughts after adding poly fill and sound deadener:



This is basically the same experience I have after doing this mod myself. The bass is noticeably tighter and cleaner after this mod. I listen to almost everything, but it's mostly rap/hip hop, rock and some electronica. I noticed that because the bass hits cleaner and tighter, it doesn't drown out the mids, and the music sounds more uniform and "right".
I followed your excellent instructions and I’m amazed at the difference. It‘s totally changed and is now on par with my partner’s Audi concert sound system. Such a simple fix, cost me about $60 AU for materials from JayCar in Australia. (Premium sound deadening material). thank you
 

sm1ke

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:
Canada
:
'18 CX-9 Signature
I followed your excellent instructions and I’m amazed at the difference. It‘s totally changed and is now on par with my partner’s Audi concert sound system. Such a simple fix, cost me about $60 AU for materials from JayCar in Australia. (Premium sound deadening material). thank you

No problem, thanks for the feedback :)
 
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