How to Improve OE Sub Bass Quality and Eliminate Vibrations

JasonO

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It would be nice if we can change those speakers in the back
The rear speakers are not the problem, the signal is. Set the speakers to full rear fade and you will see, they do not do much because they are being told not to do much.




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tadda

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That's why I wouldn't consider purchasing the Bavsound direct replacement speakers until they have a suitable EQ Amp available... There is almost no signal going to the front centers and rear side speakers! The only speakers worth replacing with the current OE Amp setup would be the door speakers which I think they're pretty decent but could still be improved on...A new Amp upgrade that takes advantage of those speakers will definitely change things for the better!

After adding some improvements (as I mentioned earlier), the OE Harmon Kardon sub setup sounds surprisingly good...Of course, a new amp would also help further improve the bass quality...
 
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tadda

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There is one more area that requires insulation in the rear cargo area that is also a major contributor to harsh vibrations experienced during low bass tracks and that is the rear cargo panel...Behind the cargo panel there is quite a bit of open dead space and the plastic panel does not have any insulation between that and the body...

I used the 2" foam padding I purchased for the narrow rear sub cover panel and applied foam to the following areas shown below...The rear cargo panel is easily removed..I also opened the empty compartment that is used to store the roadside triangle that US Supra's don't have and inserted a 2" foam strip...

No more vibrations or rattles...

Rear Cargo Panel Insulation.jpg
 
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LeoLee2017

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I spent a fair amount of time over the past few weeks thinking about how to improve the Supra's subwoofers, which we all know by now, were not designed properly and as a result have issues when it comes to both vibrational noise and lower bass quality...

Some improvement to the bass response can be made by removing the Active Sound Design (faux engine / exhaust noise) which is electrically imposed onto the bass signal when sport mode is selected ...I found that the ASD feature actually "muddies" the bass response and increases distortion and noise...

Also many of us have played with EQ settings in an attempt to optimize sound quality but the OE system still fell somewhat short...

View attachment 24428

With respect to the OE subs I saw a few areas for improvement after seeing a few pics posted of stripped down rear cargo areas and began to get to work...

View attachment 24423

1) I lined the walls of both metal sub enclosures (which are indeed separated) with 1" speaker wadding to improve lower bass response and bass quality by reducing distortions created by destructive waves within the metal enclosure..The wadding also serves to increase it's "effective" volume...Speaker wadding turned out to be a very good solution for this...

subwoofer 4  enclosure partitions with wadding and speaker flow.jpg


2) Most of the lower bass vibrational noise and distortion are actually due to the narrow rear cover panel which blocks most of the woofer exhaust energy and introduces most of the nasty low freq vibrations heard...The solution here was to insulate the area within the narrow rear panel with 2" foam leaving the exhaust port open and then add 2" exhaust ports to the narrow rear panel...

ported subs air flow.jpg


subwoofer 2a narrow rear panel.jpg


View attachment 24426

View attachment 24854

I'm extremely pleased with the results...Bass response is noticeably lower and punchier and vibrational noise is gone...I can now listen to the sound system at 3/4 volume and the bass kicks ass!

Project cost: $30

Here is a list of materials:

2" Foam Pad

1" Speaker Wadding

2" Exhaust Port
Thank you so much for the extremely detailed directions. You are the best.

Were can I get the materials?
What's the diameter of the ports?
What's the measure to the center of the ports?
 
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tadda

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Thank you so much for the extremely detailed directions. You are the best.

Were can I get the materials?
What's the diameter of the ports?
What's the measure to the center of the ports?
Here is a list of materials with description and links to where I purchased them online...I included them at bottom of my original post...

2" Foam Pad

1" Speaker Wadding

2" Dia Exhaust Port

Ports are centered over elongated exhaust ports shown below:

subwoofer 6 2 inch foam insulation with ports.jpg
 
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You are really the best. Do you do audio for a living? If not, you should.

I wish that you lived in Tampa or close by to hire you. I'm a veteran with multiple service connected disabilities and this will be a challenge. Hopefully, I can wait until sound shops over for business in Tampa. It really defeats the purpose of having a 12 speaker JBl premium soundsl system if it's not going to sound right. How did BMW engineers missed the rarattlin. I don't think that I've ever heard of a BMW vehicle with this issue.

Thank for you help..

Take care, be safe and be well..

Are you still satisfied with the results?
I'm a retired Engineering Exec and Veteran as well (Former Marine)...I did get into high end audio as a hobby during the 80s and 90s and the interest has carried into my later years...

I suspect the rattling and design error (i.e. placing a panel directly over the elongated exhaust ports) was due to cost cutting and other priority / design decisions made by Toyota....

The project is fairly straight forward and once you remove the narrow rear cover things will become much clearer....The most difficult part was cutting 2 port holes in the rear narrow panel which I used a dremel tool....

And yes, I'm extremely pleased and satisfied with the results and sound quality now....This made me reconsider having to replace the subs...For now I'm very content....
 

LeoLee2017

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I'm a retired Engineering Exec and Veteran as well (Former Marine)...I did get into high end audio as a hobby during the 80s and 90s and the interest has carried into my later years...

I suspect the rattling and design error (i.e. placing a panel directly over the elongated exhaust ports) was due to cost cutting and other priority / design decisions made by Toyota....

The project is fairly straight forward and once you remove the narrow rear cover things will become much clearer....The most difficult part was cutting 2 port holes in the rear narrow panel which I used a dremel tool....

And yes, I'm extremely pleased and satisfied with the results and sound quality now....This made me reconsider having to replace the subs...For now I'm very content....
Thank you for your service. And for the time you took to post this solution. I will start looking online for the materials needed. I will let you know when I get it done. I bought my car last week Friday 4/17/2020, and I immediately noticed that Premium JBL system sounded like crap. At first, I thought it was blown subwoofer. The vehicle only had 9 miles and the dealership doesn't let no one test drive or sit inside Supras. So my guess was the mechanics blew them. lol.. So I researched online and came across your post.
 
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Thank you for your service. And for the time you took to post this solution. I will start looking online for the materials needed. I will let you know when I get it done. I bought my car last week Friday 4/17/2020, and I immediately noticed that Premium JBL system sounded like crap. At first, I thought it was blown subwoofer. The vehicle only had 9 miles and the dealership doesn't let no one test drive or sit inside Supras. So my guess was the mechanics blew them. lol.. So I researched online and came across your post.
And thanks for your Service as well!

Yes, many of us had the same reaction wondering if the subs were blown...Once you eliminate the vibrations and allow the OE exhaust ports to "breath" the Subs actually sound pretty decent...Lining the interior metal sub enclosure walls with speaker batting also improved bass sound quality ...

I'll try and post a few more pics showing the 2 ports mounted onto the narrow panel from the inside...
 

2k20HTownMKV

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Did you try it yet?
I'm wondering where to buy the materials since most car audio shops are closed.
i have not had a chance yet. Still waiting for material to come in. Ebay and Amazon have been my best friend but still some delays in shipping. Also if you look at taddas response each one of the materials has a link
 

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Tom question about your exhaust ports. was there any reason you did not go bigger? was it size constraint or just not needed?
 

stacyoz

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For those that are going to do this project here is another Pro-Tip:

You do not need to remove the Subwoofer Cover (#11) shown below:

Woofer Cover rear.jpg


You just need to remove the narrow rear cover (#16) shown below:

woofer cover rear narrow panel mounts.jpg


I was actually able to roll up the speaker batting cut from a template (shown below) and slip it through one of the elongated exhaust ports and then use a long screw driver to manipulate the cut batting to line the walls of the metal enclosure shown below:

rear cargo area enclosure partitions with wadding.jpg
@tadda, Thank you for providing the details of this project. I am definitely going to try this to improve the lack luster sound system. It is not surprising that the bass is sub par with a plastic cover and carpet covering the bass exhaust.

three questions:
1. How did you cut the holes for the exhaust ports?
2. Out of curiosity, from the picture of your finished installation, it looks like you have installed a mesh in the exhaust ports. Can you provide any details?
3 Where did you get the exploded view of the sub assembly and did it come with part numbers?
 
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tadda

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Tom question about your exhaust ports. was there any reason you did not go bigger? was it size constraint or just not needed?
Based on the total area of the 3 elongated exhaust port holes I found that a 2" diameter port has an equivalent cross sectional area...Also the rear panel height is only 4" and I didn't want to compromise the rigidity of the panel...

Without ports added that exhaust energy was literally trapped behind the rear panel and created quite of bit of vibrational noise...Bass is now deeper, punchier, and less distorted with the ports added...

Side note: The volume of exhaust air released during deep bass sections of music is quite impressive!

subwoofer 6 2 inch foam insulation with ports.jpg


subwoofer 7a ported subs with mesh.jpg
 
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@tadda, Thank you for providing the details of this project. I am definitely going to try this to improve the lack luster sound system. It is not surprising that the bass is sub par with a plastic cover and carpet covering the bass exhaust.

three questions:
1. How did you cut the holes for the exhaust ports?
2. Out of curiosity, from the picture of your finished installation, it looks like you have installed a mesh in the exhaust ports. Can you provide any details?
3 Where did you get the exploded view of the sub assembly and did it come with part numbers?
  1. I first covered the area I wanted to cutout with tape so I could mark a 2" diameter circle...
  2. I used a dremel tool with disk to cut out the plastic panel within the marked circle...
  3. I used a small dremel grinding drum to finish the edges of the port hole...

Yes, I placed black metal speaker mesh (4" x 4") over the three elongated holes and secured in place with 3m tape...

Workshop Service Manual
 
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XPOTTEDPLANTX

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Any links to purchase said materials? Ive been serching online cant find any wadding cheap that is big enough for that template. Thabks for yalls help ahead of time
 

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