Some more info on upcoming release (May 2020) of OEM Audio Plus Complete Supra Sound Solution
FEATURES:
• Designed and tuned specifically for the Supra A90
• Supra-Specific Subwoofer System
• Multi-Channel Power Amplifier
• Pre-Calibrated Digital Signal Processor (64-Bit)
• Plug and Play...
I still prefer the 2020 exhaust note which is somewhat deeper and throatier in normal mode (not really a fan of sport mode burbles though)...The 2021 exhaust note sounds like an EU version exhaust and is kinda tame to me...
I first covered the area I wanted to cutout with tape so I could mark a 2" diameter circle...
I used a dremel tool with disk to cut out the plastic panel within the marked circle...
I used a small dremel grinding drum to finish the edges of the port hole...
Yes, I placed black metal speaker...
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...
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...
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...
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: