bass vibrations??

[Lazyron007]

Does anyone know or have any tricks to keep the rear view mirror from shaking and making a lot of noise when the bass is up really loud?

[joe603]

Dynamat on the inside should do the trick.

[Looneybomber]

Does anyone know or have any tricks to keep the rear view mirror from shaking and making a lot of noise when the bass is up really loud?

Dynamat on the inside should do the trick.

What!? Dynamat on the inside of the rear view mirror!?

Lazyron, the soundwaves are causing your windsheild to vibrate obviously, you could either replace your windsheild with bulletproof glass/1" plexy or turn down the volume.

As for keeping your mirror from rattling, you'll need to make sure it's glued down securely to the window. As long as it's properly glued down you should be fine. If you still need more help with it rattling, you can slide the mirror off its base, glob a bunch of silcone in there and slide it back on. Wipe off the excess.

[jmaxima]

I don't have a photographic memory, but I think the mirror is attached to the roof - not the window. With a foot against the window to keep it in place. Adding mass against the back of the mirror along with tightening all the fasteners is the first route to reduce vibration. Adding SD material to the roof can also help. But there isn't really a good way to stop all vibration. Adding mass will lower the resonant frequency and require greater energy to excite the mirror and case. Tubular steal or titanium fasteners along with a tube frame for the car may also help.

[joe603]

What!? Dynamat on the inside of the rear view mirror!?

Yup...Dynamat on the inside of my mirror... (took it apart and applied it to the backside). It stopped the rattles coming from the unit and helped with the excessive mirror vibrations.

-I should mention that I have an auto-dimming one...

[JLPX2]

Turn the volume down.

[joe603]

Turn the volume down.

Why would I want to do that? I have two beautiful MTX subs that hit kick drums hard enough to give you a massage

[PoorManQ45]

Yup...Dynamat on the inside of my mirror... (took it apart and applied it to the backside). It stopped the rattles coming from the unit and helped with the excessive mirror vibrations.

-I should mention that I have an auto-dimming one...

The problem is that that doesn't work when the whole damn car is vibrating

[positron1]

Do you guys/gals with the subs have hatches or coupes and what direction do you have them facing...trunk/hatch, cockpit or the sides?

[PoorManQ45]

I don't have a sub, but I've informed these guys that they should have them as close to the rear of the trunk/hatch while firing towards the back.

This has been proven through testing to produce the least cancelation

[positron1]

You don't get tremendous trunk/hatch rattle with them firing that close to the back?

[joe603]

To answer your question, no. It does not matter what direction the subs fire because for the most part, they are non-directional. With a strong enough system, either direction will find rattles. However, with Dynamat installed properly, and extra used as needed for trouble spots, your car will not sound like the Honda civic in the mall parking lot with the "trunk-about-to-fall-off" sound. I usually laugh at them, especially when they have the attitude.

This is how my system is set-up in my G35.

[xxcrashxx]

thats a cool setup. wish i could do something similar in my j30, damn gas tank is in the way tho. i got my sub in my trunk, facing the driver side of the car, and the box is positioned on the passenger side. i get great bass when its turned up all the way, and no rattle sounds.... granted my mirror shakes like crazy, but hey, who needs that one, when u got two more mirrors to look at. LOL

is that how the trunks are on those cars??? with the shocks on them?? thats pretty sweet, do they have enough force to open the trunk when its popped??

[joe603]

Thanks! I love to pimp her out every now-and-then...

I think you asked if the subs can open the trunk? When the subs are kicking, the trunk acts like an enclosure. If I were to open the trunk while they were being pushed, I'd probably damage the drivers. Whenever the trunk is opened, the music is turned way down.

If you meant the shocks, no they do not open the trunk all the way. After hitting the key fob or dash button, it pops open-I still have to lift it a little to make it go up. One thing I like about the G35 is that even the trunk is nice...cant see any sheetmetal like on most cars.

[PoorManQ45]

I think you asked if the subs can open the trunk? When the subs are kicking, the trunk acts like an enclosure. If I were to open the trunk while they were being pushed, I'd probably damage the drivers. Whenever the trunk is opened, the music is turned way down.

So are you saying that there is no back on the box? Meaning there is nothing but the rear seat behind the face that we see?

Or is there MDF back there to enclose it?

[joe603]

No, its a sealed enclosure, but the space in the trunk acts like another enclosure...almost like a bandpass box. When the speakers are pushing air, the trunk space is pressurized. If you remove that pressure when the system is running hard, the drivers become unstable and could be damaged.

[C-Kwik]

There is no reason why a matched sealed enclosure can't provide the correct "suspension" needs for the subwoofer. IF you blow a speaker becuase you open the trunk, I would be reevaluating my set-up. I doubt the space in a trunk would provide any significant suspension properties for the sub either way.

[joe603]

This is just what my installer recommended....He said NOT to open the trunk with the system being pushed, or I could damage the speakers due to the lack of negative pressure from the trunk being open.

It makes sense if you think about it...with the trunk lid closed, you create an enclosed space of air the drivers have to push against. If that pressure is released, then the drivers do not have as much resistance, thereby increasing the suspension movement. Now I'm not going to test to see if my speakers can blow, but I know that those baby's move with a bass-heavy track. I wanted to see 'em in action when I picked up the car. (This was when he told me not to have the trunk open when pushing the system)

[yelnatsch517]

This is just what my installer recommended....He said NOT to open the trunk with the system being pushed, or I could damage the speakers due to the lack of negative pressure from the trunk being open.

It makes sense if you think about it...with the trunk lid closed, you create an enclosed space of air the drivers have to push against. If that pressure is released, then the drivers do not have as much resistance, thereby increasing the suspension movement. Now I'm not going to test to see if my speakers can blow, but I know that those baby's move with a bass-heavy track. I wanted to see 'em in action when I picked up the car. (This was when he told me not to have the trunk open when pushing the system)

How do the MTX's sound? I personally would have picked different subs for a g35, but that's just me.

Oh yea, what kind of amps are you using? Did the installer suggest the equipment or did you tell him which ones to use?

[joe603]

I've had RF and Kenwood Excell subs, and the MTX kick much harder! It was between the JL 10W7 and the MTX 7500. 2 10" MTX subs were louder and cheaper than 1 10W7.

http://www.mtx.com/Flash2/volume_displacement.cfm

The amp is the MTX TA 7801. I used the MTX installer/dealer because I wanted to use an MTX amp. I had 2 in my last car, and they were bulletproof.

I'm very happy with the end result. The stock speakers sound ok, but with the added thump of the subs, the sound is excellent. Next on the list is to replace the deck and the mids/highs.

[PoorManQ45]

It makes sense if you think about it...

Nope, makes no sense.

Especially sinse you have a sealed enclosure.

When the sub moves in you are pressurizing the air volume inside of the box. This wants to push the sub outwards. When the sub goes out you decrease the pressure inside of the box. This causes the sub to want to go back in.

It equalizes.

The installer did good work, but he definately shouldn't try to teach anyone

[joe603]

The box is sealed, so there isn't anything to equalize the air from the trunks perspective. This is why you can feel the trunk vibrate when bass hits; its putting pressure on the trunk enclosure.

A quick way to test....listen to a strong bass track with the trunk closed. Now, leave the volume at the same level, but open the trunk. It will not be as loud because you've allowed pressurized air to escape. And, it doesn't matter what direction your subs are facing either. The loudness is increased because of resonance of a sealed enclosure within the trunk.

This is the theory behind damaging the woofers if you drive them hard with the trunk open; the volume of air pushing against them is no longer present, thus causing damage.

[PoorManQ45]

Believe it or not when subs are improperly placed/faced in the trunk they will play louder with the trunk open! Yes, I said louder.

This is due to cancelation that occurs.

What you're talking about it just simply cabin gain. Basically, the smaller the space, the more gain you will get above anechoic. This is due to the fact that you have to pressurize less air. Which obviously is easier then pressurizing a large volume of air.

When you open the trunk you are basically making the air space infinite. Therefore in a properly setup system the bass output will decrease.

In an improperly setup system the bass may actually increase.

Just note though, neither having the trunk open or closed will help nor harm the sub

[positron1]

So the best direction to face a small, say 10" sub, in a coupe to get the best sound quality would be.......?

[PoorManQ45]

Well, it's not just facing, it's placement too.

The best place would be as close to the back of the car as possible, with the driver facing towards the back of the car. Leave atleast 3~5" for the driver to be able to move an adequate amount of air