How to Improve OE Sub Bass Quality and Eliminate Vibrations

pav911

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Just in case there are others as new to this as me, I’m going to add what I’m learning along the way.

It helped to lay all the cut dynamat pieces down for a test fit before sticking anything.

I also realised I’ll need some sort of cleaning solvent to prep the trunk area before sticking down the dynamat.

A82B7618-C185-413B-AF89-471FFDB7E213.jpeg




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pav911

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yes...it will allow you to pull up the rear of the cover a few inches to make it easier to insert center foam block...
I honestly don't see how I can get a 2" foam block up there. Or do you mean put noico up there? thx
 
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tadda

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I honestly don't see how I can get a 2" foam block up there. Or do you mean put noico up there? thx
I used 2" foam....foam compresses...You can also cut the foam to a 1"x2"x6" block...
 

pav911

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I used 2" foam....foam compresses...
Another thing I've learnt is there's all sorts of foam. I think I ended up buying the stuff that doesn't compress all that well. it's quite firm.
 
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tadda

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Another thing I've learnt is there's all sorts of foam. I think I ended up buying the stuff that doesn't compress all that well. it's quite firm.
It appears as if you have the correct foam from the pic you just posted...just cut the foam block to a 1"x2"x6" block and insert
 

Supra889021

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Greetings one and all. I'm a car guy and have owned 2 earlier Supras. Now looking to maybe buy a '21 3.0 Prem.
I need your help if anyone knows the answer. I've seen many vids on the "issues" with the vibration caused by how the speakers are mounted, poor insulation, etc. My question is: Are you all talking about the 2020 model...and is the 2021 exactly the same OR did Toyota "happen" to fix this issue?? If I'm going to buy the '21 I need to know if I'm going to face this very same issue.
Thank you all for any help and knowledge you have with the new Supras.
 

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Same design. It’s just kinda meh
Not a big deal to me. Definitely not even in the top 30 reasons to buy or not buy.
 

pav911

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I'd definitely recommend taking your favorite music to the dealer and spending some time with the car and its audio system. I really regret not doing this, as I wouldn't have bought the car knowing what I do now. Of course where the audio system sits in your list of reasons to buy a car is different for each person so it may not bother you that much. Without a doubt this is a great car to drive and I'm trying to best to just ignore the rubbish audio system.
 

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Everyone is different. It can definitely be improved. I didn't even turn the radio on during my test drive. lol
 

john99teg

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Finished thank you to the op who created this brilliant idea. I tried your settings for equalizer, however, bass seems overpowering. Or how do I say the frequency of bass likes to hit and hit hard. Is there changes between 2020 and 2021? Maybe I have to turn off the Active Sound Design.
 

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Finished thank you to the op who created this brilliant idea. I tried your settings for equalizer, however, bass seems overpowering. Or how do I say the frequency of bass likes to hit and hit hard. Is there changes between 2020 and 2021? Maybe I have to turn off the Active Sound Design.
:thumbsup:

As far as I know no changes were made to the audio system for 2021...I was actually able to take off the rear panel on a 2021 and saw that it's the same exact setup...

Turning off ASD makes a big difference...With ASD enabled bass tends to be boomy and distorted....
 
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Mark-in-Stoke

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My musical tastes are very broad from rock, pop, EDM, alternative, classic, jazz etc.....that said, the Techno and EDM tracks really tests the subs limits and is what I enjoy listening to the most....

This latest album (below) I've been using to setup and test the sound system and particularly the subwoofers has allowed me to isolate all the vibrations, distortions, and rattles....I spent nearly 2 hrs in my Supra yesterday enjoying the entire album at 2/3 max volume and it sounded amazing...And damn the bass is tight and deep now....

Ethereal Techno #008 - favorite tracks are 1,3,5,6,9,19,20

As I've mentioned a few times already, to my surprise and delight the HK Subs are actually very good once you remove all the other physical design warts in the system! Lining the sub enclosure walls with speaker wadding and adding the exhaust port made a huge difference in overall sound quality...The rattles and vibrations also contributed quite a bit to poor sound quality which are gone now...

Next up are the doors and yes I'll definitely keep you posted and please do the same....
Try this track called Seventh wonder by Tonny Nesse it's orchestral trance with some sweet drops in it, and btw thanks for the effort of putting this DIY guide together, can't wait to crack on with it.
 
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Tripjammer

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Turning off ASD does wonders in this car! The 2021 Supra is almost dead silent now and the stereo is good sounding after the EQ adjustments! This is not a bad stock stereo. I still need to make the foam in the sub and port mod and do the dynamat but I bet once all this is done it will be almost perfect! I still think the car is too quiet after the ASD is turned off but hey better to have a better sounding stereo! I am gonna have to get a down pipe and after market exhaust to get more sound....
 

Tripjammer

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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...What I discovered after implementing the improvements outlined below is that surprisingly, the OE Harmon Kardon 8" Subwoofers in the Supra are actually very good speakers once you correct some very basic design issues that were overlooked by Toyota...

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To start with, some incremental improvements to bass response can be made by first removing the Active Sound Design (faux engine / exhaust noise) which is electrically overlayed onto the audio channels when sport mode is selected ...I found that the ASD feature actually "muddies" the bass and audio response and increases distortion and noise...

In addition, many of us have played with EQ settings in an attempt to optimize sound quality but the OE system still fell somewhat short...I also found that selecting the "Surround" enhancement feature added to the phase distortion which resulted in reduced sound clarity...This is one of the first things I turned off and the system clarity was noticeably improved...Also note that "Speed Volume" is turned all the way down as this will change the EQ curve as speed increases resulting in an undesirable response at hwy speeds...

Here are my current audio settings:
  • ASD / Active Sound Design (off - using Bimmercode)
  • Surround (off)
  • Speed Volume (0)
  • Balance: (0)
  • Fade: (front +2)
  • Broad Bass (+2)
  • Broad Treble (-2)
  • Equalizer (shown below)
These are my new EQ settings (below) after improvements made to current OE Subwoofer system...I can now raise the volume to 2/3 of max with no low bass distortions or vibrational noise...

How to Setup and Optimize Sound Quality using OE Equalizer

Equalizer settings after sound test.jpg


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Now with respect to the OE subwoofer enclosure itself what I outline below is where most of the major improvements to bass response and elimination of vibrations were made... I've identified a few notable areas for improvement after observing a few pics posted of the cargo area stripped down and began to get to work...It should be noted that the only panel that needs to be removed in order to make the following changes is the narrow rear subwoofer panel (shown below)...

subwoofer 2a narrow rear panel.jpg


First, lining the walls of both metal sub enclosures (which are indeed separated) with 1" speaker wadding improved 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...

Pic below is posted just to show what enclosure looks like totally exposed....Again, the only panel you need to remove to line the walls with wadding is the narrow rear panel

subwoofer 4  enclosure partitions with wadding and speaker flow.jpg


Enclosure Lining / Wadding Template: 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:

Left_Enclosure_Template.png


Subwoofer 5 2 inch foam insulation closeup.jpg


Secondly, and most importantly is that the majority of the lower bass vibrational noise and bass distortion is actually caused by the narrow rear cover panel blocking the subwoofer exhaust energy...The solution here was to 1) Insulate the area within the narrow rear panel with 2" foam leaving the exhaust port open and 2) Adding 2" exhaust ports to the narrow rear panel...

ported subs air flow.jpg


Foam Cutout Dimensions (below):

Note: I didn't need to remove the narrow rear panel mounting brackets...I actually used a 4"h length of 2" foam and cut slits into the foam such that the foam could be worked in from the top behind each of the brackets...

Wall_Template.png


subwoofer 6 2 inch foam insulation with ports.jpg


Installing Rear Panel Exhaust Ports...
  1. Cover the front carpeted area of narrow rear panel to be cut with blue tape and mark a 2" diameter circle
  2. Use either a 2" hole saw or a dremel tool with disk to cut out the marked circle
  3. Use a small dremel grinding drum to finish the edges of the port hole
  4. Cut the black OE panel insulation in the the center of hole and fold back on either side
  5. Insert 2" exhaust port
  6. Use tie wrap to hold thin black OE panel insulation along side walls of exhaust port
  7. Secure port to rear panel with drops of epoxy or superglue at edges touching rear panel and port walls
I also placed black metal speaker mesh (4" x 4") over the three elongated holes and secured in place with 3m tape...

rear panel port diagram.png


subwoofer 7b ported rear panel.jpg


I've also identified another area that needed to be addressed...I discovered this after implementing all these other improvements, thus allowing me to significantly increase volume along with raising bass EQ settings...What I found was that there was some exhaust port energy escaping from under the long narrow rear panel (which as I show in a few pics below) causing the rear floor panel to vibrate...Keep in mind that this is yet another design problem which causes the floor panel to vibrate where in-turn this vibrational energy is transferred to the cargo areas' side and back panels causing them to vibrate as well...

The solution here was to apply some adhesive back foam to the areas show below which eliminated any energy transfer under the rear cargo floor panel...

Shown below, I first applied 1.5"d x 4" L x 0.25" h adhesive backed foam strips above and below both exhaust ports to isolate them further from the top cover and floor....

subwoofer 7b ported rear panel insulation strip.jpg


Next, the image below shows where some exhaust energy from the 3 elongated ports was also being released under the large rear floor panel causing it to vibrate greatly...With the floor panel removed simply place your hand under the narrow panel and you'll see / feel the exposed gap ...

subwoofer 2a narrow rear panel exhaust port leak.jpg


Shown below are the locations where 2 adhesive back foam strips were applied to underside of exposed narrow rear panel ...The left adhesive backed foam strip was 1.5"D x 11" L x 0.25" H and the right foam strip is 1.5"D x 6" L x 0.25" H...This essentially sealed off the gap where the exhaust energy was also being channeled...

As a result the large rear floor panel vibration has pretty much been eliminated and side and rear trunk panels no longer vibrate during low bass / high volume music passages....

As far as materials, I used Noico RED 315 mil Sound Insulation , which I already had available for beginning my next project of eliminating front door speaker vibrations ....

subwoofer 2a narrow rear panel foam strips.jpg


Here is yet another area that required attention for eliminating subwoofer grill rattle / vibrations...I did this awhile ago and thought it might be helpful to post while we're on this topic....

Remove the woofer grill assembly by prying up to free clips around the grill and then separate the 12 spoke grill cover from the flat grill plate and apply small dollops of flexible silicone adhesive around the underside of the 12 spoke cover (shown below)....Now reassemble and press firmly around the edge of the flat grill insert plate to secure it to the 12 spoke grill cover...

woofer grill cover felt pads.jpg


And finally, I applied some Dynamat to cargo area floor to eliminate any further vibrations and reduce road noise...

Cargo area dynamat.jpg


There is one more area that I would recommend applying some insulation where some vibrations occurred during low bass tracks...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 had already 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...

Rear Cargo Panel Insulation.jpg


Shown below is a pic of the finished project:

completed ported subwoofer system.jpg


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Here is a list of materials I used:

2" Foam Pad

1" Speaker Wadding

2" Exhaust Port

Dynamat Extreme

Noico Adhesive Backed Foam Panels

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Summary and Final Thoughts:

Surprisingly, the Harmon Kardon 8" Subs in the Supra are actually very good speakers once you correct some very basic design issues that were overlooked by Toyota... Without ports added, the bass exhaust energy was literally trapped behind the rear panel which created quite of bit of vibrational noise and also muddied bass response...

Adding exhaust ports to the rear panel along with lining the enclosure walls with wadding and insulating the space behind the narrow rear panel, essentially lowered the Q (damping effects) and resulted in a flatter / clearer bass response...The Bass is now deeper, punchier, and far less distorted and eliminated much of the vibrational noise heard...

For anyone considering installing direct replacement subwoofers as a knee-jerk reaction to improving sound distortions, vibrations, and rattles, these basic improvements should be seriously considered before replacing them...

I am getting all the parts and I am about to do this in a few weeks...Should be fun...Thanks for the write up!
 

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