FX Sound Deadening Project - Infiniti FX Forum : FX35, FX45 and FX50 Forums
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post #1 of 2 (permalink) Old 05-20-2014, 10:11 AM Thread Starter
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FX Sound Deadening Project

Hello All,

I'm new to the forum, I hope you enjoy this content. When I purchased my Infiniti FX50S there were a couple things I wasn't too happy with. Sure it's an amazing car and I absolutely love it, but there's room for improvement.

One of those negative qualities was the lack of sound deadening in the car, as you know the acoustic characteristics of the stock vehicle are simply horrendous. Sure it's fine when compared to most cars, but when comparing the FX to the Volvo XC60, BMW X5, Merc ML500, Audi Q5 TDI and the Porsche Cayenne; it's simply not good enough. The FX is great value, but still for the price I expect my cabin to be quiet and composed.

I proceeded to disassemble my FX to see what I was dealing with. This included all of the trim in the rear cargo area surrounding the spare tyre, the middle bench seat, all of the door trim, the real wheel-well moulding and the exhaust shield cover. Hidden underneath this trim was the body, no sound deadening material at all from the factory. No wonder.....

I would have liked to remove the front seats entirely, along with the dash, the carpets and the head-liner; but the amount of work involved would have been mind-boggling. It simply wouldn't have been worth the effort. So I simply sound deadened key area's and whatever was easily accessible.

I designed a method of layering different sound deadening materials together in a way that would have the most significant impact. The goal was to.....

- Reduce road/tyre noise entering the cabin (Under-body).
- Reduce external noise entering the cabin.
- Stop resonance of the door panels due to the speakers.
- Improve acoustic performance inside the cabin.
- Stop sound from exiting the cabin (speakers).
- Remove low end exhaust frequencies (drone).
- Reduce overall exhaust volume inside the cabin.
- Improve thermal performance.

The exhaust upgrade had given me a little performance boost and I'd shredded around 15KG by removing the stock muffler, this allowed me to install a cornucopia of sound deadening into the car without altering performance due to the weight gain. In total, I used about 80KG of material. Mass Loaded Vinyl was installed as a formed barrier around the occupants, Closed Cell Foam was used as a gasket or baffle on both sides of the the MLV and also to filter high frequency sound. Thermal sheeting was used where possible to improve the cars thermal signature. To alter the car panel resonance and the overall acoustic profile of the vehicle Dynamat extreme was used in conjunction with Enduust Sound Guard, a rubberised sound deadening layer allied to the cars underbody. The engine noise was also decreased by adding as Dynamat hood-liner.

Layer Zero: Endrust Sound Guard (Rubberized external under-body sound damper)
Layer One: Dynamat Extreme (Reduces resonance, creates mass and thermal barrier)
Layer Two: Thermal Insulation (Second thermal barrier)
Layer Three: Closed Cell Acoustic Foam (Baffle and high range diffuser)
Layer Four: Mass Loaded Vinyl (Full range mass absorber)
Layer Five: Closed Cell Acoustic Foam (Baffle and remnant absorption)
Layer Six: Thermal Insulation (Third thermal barrier)
Layer Seven: High Density Acoustic Insulation Batting (Absorber)
Layer Seven: Factory Carpet/fitments

Deadening Locations:

- Rear wheel well mouldings, applied a 14 layer treatment to kill the road noise at it's source.
- Trunk Trim, applied 7 layer treatment to everything accessible; partial wheel well, under seats, inside trim pieces etc
- Rear seat back, applied a treatment to the removable seat backing plate.
- Rear seat cushion, underneath. Pictured, this absorbs lot's of road noise.
- Rear Doors, installed accordingly to also improve boss stereo's acoustic capabilities.
- Front Doors, installed accordingly to also improve Bose stereo's acoustic capabilities.
- Rear seat kick plate
- Above exhaust, external heat shield now unused with removal of exhaust.
- Underneath front and rear foot mats.
- Bonnet, installed acoustic hood-liner.

The entire trunk trim was removed which allowed me to apply deadening to the entire trunk bed all the way under the passenger seats, and also the wheel wells. Total coverage! Very important!

Sorry there aren't more photo's, installation was very intricate. With different sizes of sheeting installed fitting together like Tetris. Together they absorb and deflect a very wide spectrum of sound.

This is the rear seat removed with the completed installation, looks awesome.

Now there's simply no road noise, no whine, no wind noise; just a distant ambient low frequency sound of the tires of the road. But it sounds far away, not right underneath you. There's now a very substantial feeling of safety and quality in the car. Everything sounds solid and heavy, like a tank. The doors close with a notable thud! Driving along it's awkward being able to whisper a conversation whilst doing 110KM on the highway, it's just awesome; quietest car I've ever been in. But with that said, those 21" wheels and tyres are still an issue if driving on a bad road. Only way the solve that is change wheels.... Which I'm not going to do; I like the wheels.

The sound deadening had a crazy effect on the Bose sound system, so much louder, less panel vibration. Less sound escapes the car so if I'm pumping tunes at traffic lights the person next to me can't hear rattling or anything. Overall the sound deadening was a tremendous success, the car feels incredibly solid and the weight gain is negligible; and what weight was added is distributed evenly which in turn softens up the chassis's firm suspension.

The sound deadening was a great success and I recommend that this modification be performed by ALL FX owners. Changes everything! I'm a perfectionist so the install took a solid week, the cost was around $800 in materials. The materials are typically expensive, Dynamat, MLV etc. But well worth it.

If you have any question please ask, thanks!
AusQX70s is offline  
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post #2 of 2 (permalink) Old 08-03-2018, 03:01 AM
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Man, awesome job! This sounds like something I'd love to tackle but I fear it may be a bit beyond me. How would you rate the difficulty of the project? Could a mechanical newb with a little guidance get it done?
VladFX50 is offline  

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