Best upgrade yet (Sun Screen)

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There are lots of cars with subs in the trunk and also lots of people put subs in the trunk. The thing is low frequencies are omni-directional, or more so than higher frequencies. The wavelength of a 60hz tone is very long, so it permeates through most materials. When designing acoustic foam, you need a material the thickness of a quarter of the wavelength of the frequency you are trying to attenuate. A 1k tone is approximately one foot long, so in order to attenuate that frequency, or absorb it within the material, you need about a 3 inch thick panel. Any frequencies above 1k would get absorbed as well. Low frequencies are the hardest to mitigate for soundproofing because their wavelengths are so long, when you get real low they're like 30 feet long. That's why most subs have a phase switch, because depending on where you place a sub you might not actually hear it because the wave is at its zero point where you're sitting. That's also why you can hear one of those boom boom cars a thousand feet away.

This is just what I know from my experience in the audiovisual field of work, so I decided to do a not-so-scientific experiment. I used a three inch piece of Roxul mineral insulation, which is basically what acoustic panels are made of, and did some measurements with the audiotools app on my iphone. Tone settings are flat, volume is somewhere in the middle. I played a sine wave at 60hz, 100 hz, and 200 hz, both with the grill open and with the insulation taped to the underside of the grill. I then played pink noise and captured the covered and uncovered results. The Iphone was placed over the center console.

One thing I learned is that I have some resonant rattles at 60 hz. Another thing I learned is the rear seats have barely any coverage.
I could see that the cabin would feel more "dead" because there are less high frequencies bouncing around in the trunk, but the sub would work fine if the trunk was completely enclosed. It might honestly improve bass response because sound is pressure, and you'd be increasing the pressure in the trunk when sound is moved through it.

If you are talking about the rear seats, I could see more attenuation of the sound because there doesn't seem to be any woofers in the door speakers, but from the front seats I noticed no change in bass response and the results back that up. So I think covering that grill would be a great way to get rid of some road noise, but probably not the droning type at lower frequencies.

The phase switch on a sub is usually there to match your speakers, which could be on the opposite phase.
Can happen with mixed brands in which subs often are different from the mains.

I agree the foam is probably attenuating some higher frequency noise more than anything.
But the music seems somewhat less punchier in the lower frequencies. How low I don't know.
How high the rear sub covers I also don't know.

Speakers move air and I significantly change the path air moves from trunk to cabin. Period.

 

[Shizzrock]

The phase switch on a sub is usually there to match your speakers, which could be on the opposite phase.
Can happen with mixed brands in which subs often are different from the mains.

That's not entirely true. It has nothing to do with brands, but rather avoiding standing waves, which are sometimes unavoidable with low frequencies due to their long wavelengths. Like you said, the switch is there in case the sub is out of phase with the rest of the speakers. This, however, is entirely dependent on where you are listening in the room and nothing to do with brands of speakers. The sub can be placed anywhere because of the omnidirectional nature of bass frequencies, but the rest of your speakers are usually in front of you. If the sub was right next to the rest of the speakers, generally you could set the switch to zero and it would mostly be in phase. But it's still dependent on the room dimensions and where standing waves actually occur.

Speakers move air and I significantly change the path air moves from trunk to cabin. Period.

Ok, but the RTA couldn't tell a difference when I did my test. It will definitely change the acoustics in the cabin, though.


I'm also doubling down and saying the only reason that hole is there is for light in the trunk.

 

[chinnam3]

That's not entirely true. It has nothing to do with brands, but rather avoiding standing waves, which are sometimes unavoidable with low frequencies due to their long wavelengths. Like you said, the switch is there in case the sub is out of phase with the rest of the speakers. This, however, is entirely dependent on where you are listening in the room and nothing to do with brands of speakers. The sub can be placed anywhere because of the omnidirectional nature of bass frequencies, but the rest of your speakers are usually in front of you. If the sub was right next to the rest of the speakers, generally you could set the switch to zero and it would mostly be in phase. But it's still dependent on the room dimensions and where standing waves actually occur.



Ok, but the RTA couldn't tell a difference when I did my test. It will definitely change the acoustics in the cabin, though.


I'm also doubling down and saying the only reason that hole is there is for light in the trunk.

That's correct. One of the main purpose of the Phase switch to align Sub sound to be in phase with main speakers. Nothing to do with brand( We are not timbre matching here in base region). Lower end subs simply have 0 deg or 180 deg, but some subs have more fine grained control for phasing.

Phasing depends on where you placed the sub and direction of the Sub.

Fortunately, most mid range and higher end receiver now-a-day offering Phase correction and timing correction even for Subs. I have seen too many installations where Sub is not in phase, and many installation too boomy and folks thinking it is very good.

Like you said, taming bass is not as easy as high frequencies. I ended up with several acoustic panels in corners at 45% in my HT room to clean up bass, still not ideal.

BTW, I was also thinking of building a lightweight panel to cover glass over front seats. One aspect it reduces some noise coming in, thermal insulation for heat, and ofcourse it tames hi-frequency reflection little bit. Wish some 3rd party offers some nice panel to press fit in that area which can act as sunscreen/heat rejector as well as noise isolation.

Closing the grill over rear deck, may be not a good idea. Cabin pressure equalization air vents for model 3 are covered by rear bumper on passenger side which is in the trunk. So when door are closed air pressure is relieved via this grill.

 

[RyanT]

Aren't there phone apps that will measure the decibels in the car? You could take these 2 upgrades out and measure it on a noisy stretch of road and compare it with the measurements with them in.

 

[mswlogo]

That's not entirely true. It has nothing to do with brands, but rather avoiding standing waves, which are sometimes unavoidable with low frequencies due to their long wavelengths. Like you said, the switch is there in case the sub is out of phase with the rest of the speakers. This, however, is entirely dependent on where you are listening in the room and nothing to do with brands of speakers. The sub can be placed anywhere because of the omnidirectional nature of bass frequencies, but the rest of your speakers are usually in front of you. If the sub was right next to the rest of the speakers, generally you could set the switch to zero and it would mostly be in phase. But it's still dependent on the room dimensions and where standing waves actually occur.



Ok, but the RTA couldn't tell a difference when I did my test. It will definitely change the acoustics in the cabin, though.


I'm also doubling down and saying the only reason that hole is there is for light in the trunk.

RTA can be really tricky. I tried to do that between my Jeep Summit (which is extremely comfortable noise wise) and model 3. I couldn't tell the difference either. But it was clearly different to my ears.

I respect your opinion on the rear deck hole and you might be right. Mine is just a hunch.
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Most systems have a time delay to where you are sitting relative to each speaker and sub (need to be careful of added processing delay in some subs). So if they are in phase it should be all correct. But you could still be sitting in null. Flipping the polarity isn't really a good fix if there is a problem. Moving the Sub or Seating position is. No matter what the main speakers should be in phase with mains. If it sounds better with it out of phase you have big problems.

 

[Tricia]

Does anyone know where to buy seat covers for the model 3?