Found some MLV and the perfect de-coupling product at Home Depot. My local store didn't carry it but free shipping online.

dB-3 4 ft. x 8 ft. Acoustical Barrier-DB348X96BX at The Home Depot
4'x8' is enough to do a floor, $30
i got two of them to ensure rear seat and wheel wells.

but you need to decouple the product, that's where ultratouch thermal barrier comes in
UltraTouch 48 in. x 6 ft. Radiant Barrier-30000-11406 at The Home Depot

i noticed my floor gets hot from the exhaust, so this will help that as well. this would also be well suited on the roof to keep a car cooler in the summer (assuming you tint your windows and cover the windshield).

for extra fill in cavities, these bags will do the trick:
UltraTouch 16 in. x 48 in. Denim Insulation Multi-Purpose Roll-60301-16482 at The Home Depot


note that i'm not going to use CCF. CCF is fine for rattles and since it doesn't compress it is a thin decoupler, but CCF isn't absorptive.

The ultratouch blanket insulation is an excellent absorber, and will compress but will still decouple. I expect better results with this blanket than standard CCF.

to adhere the blanket to the roof i would just use spray glue, but keep the foil facing the inside. the blanket is lightweight so spray glue to tack it in place, then replace headliner. this will also improve absorption inside the car for improved acoustics.

The MLV package says .75 lb/sf but then says the 32sq. ft. package is 32 lbs. i know they make 1/2 lb/sf and 1 lb/sf. i assume it's the latter. there was a negative review where the guy sandwiched it between two layers of drywall - well no **** it didn't work, it's a limp mass barrier - the "limp" part is crucial. had that person put the MLV on the inside where it could be loose, he would have seen a marked improvement.

MLV came in. 0.75 lb/sq.ft. still cheaper than the 0.50 lb/sq.ft. i have found which was $140 for 100sq.ft. shipped.

looks decent. once i get the insulating blankets i'll lay it down. i have about 125 sq.ft. coming. i have a lot of uses for them

I got way more than I needed to do the floor. This just one of two rolls, $50 shipped for what you see.






Looks like I will be doing both my cars.









installed and a huge different was made. i'm very happy. much quieter.

deadener on metal to lower resonance. minimum 25% coverage, I prefer as much as you can afford.

radiant barrier on top of deadener/metal to decouple the MLV and reduce heat transfer. radiant barrier should be 100% coverage. i use aluminum foil tape to hold the radiant barrier down.

MLV on top of radiant barrier. MLV should be 100% coverage. MLV should not touch metal. seams are inevitable since it won't bend. seams should be closed with a thick tape (like gorilla tape). i don't show my seals in the pics above. 100% is not possible since you cannot cover where the seats bolt down, or on top of the transmission hump crap. so cover as much as you possibly can.

 

Hey Rich (and any member who wants to help), my names Ryan. New to this forum but learned quickly that you're the guru. If you got the time, I'd love some advice.

Objective: Upgrading 2 front, 2 rear, and 2 tweeters from stock to anything better than stock. Will be happy with the improvements from an aftermarket HU and speakers. Not going to have the car long enough to invest in sub + amp.
Car: 2007 honda accord ex-l sedan, 315000 km on it
HU: Upgraded to aftermarket unit in 2015

Question:
Front speakers: Hoping to replace with new speakers that fit snug in the existing stock pocket, without an adapter. Thinking this might be acceptable since I won't have the power of a sub + amp rattling things around. Want some pro advice.
Also, I'm not sure if 5.25 or 6.5 for the front is a better choice. Any recommended models for this project?

Any other advice you've got is 100% welcomed. Maybe you would approach this project differently?
Hope this catches you at a good time. Thanks man

 

You will need a speaker mounting adapter. They are plastic and are greatly helped with some foam to prevent buzzing. you need to recreate the factory seals between the door metal - speaker - door panel to get any usable bass response out of the speaker (and general good sound). Either 5.25 or 6.5 is suitable, the latter is my preference, typically.

JBL, Polk, Alpine, JL Audio, Hybrid Audio, and Hertz all make budget-friendly speakers that are well built. Used speakers are another option if you want to really lower costs.

Front speakers will have passive crossovers and will need to be mounted somewhere. You can intercept the factory wiring for the door speaker but you will need to run a new wire from the crossover to the new tweeters (easy).

 

Thanks for the quick reply!
The car has 3/4" OEM tweeters in the dash under the windshield that I'm replacing with a pair of JBL GTO 9s... so I was planning on putting 6.5" coaxials in the front door, instead of components.
Is this doable/advisable knowing that I'm only using the built in amplification from the aftermarket head unit, and not installing a separate amp or sub? In other words, wouldn't there already be a crossover connection between the stock tweeters and front speakers - allowing me to just swap the speakers?

 

there are no crossovers between stock speakers and stock tweeters. The stock tweeters have a small capacitor mounted to them, it acts as the high pass filter. you can install any tweeter you want in that location, just ensure you include a crossover with it.

You can run dash tweeters and door coaxial. you may want to turn treble down a bit on the head unit.