What would your take on sunroofs be?. i have roof flex, but i do have more sunroof flex than anything and i know im loosing alot of pressure through there, any ideas to what i can do to lower the amount of movement without making it look horrible. and keep the sunroof in usable condion
Pete you are a genius, with an extensive lexicon of audio terminology I must admit. You've definitely proved you're point, and I remember hearing that each millimetre of panel or box movement equal 20 watts of acoustical power loss.. So how can trunk and roof rattling be solved aside from heavily dampening the body with 'dynamat' & Mass Loaded Vinyl, and re-inforcing/bracing the roof and doors with metal or concrete or something... And what about stiffening the trunk latch?
Also realize that it takes a good amount of pressure to flex body panels. Yea sound is lost through resonating panels and what not, but it still takes a good amount of pressure to make them flex. There arnt many street setups out there that have the power to flex body panels. That said, each car will take a different amount of pressure before it starts to flex. Its kinda a rough way to tell how much pressure there is......as there isnt many other ways to tell from a youtube video...
I agree with this video under normal competiton formats except one.and that MECA's drive by spl which is measured from the outside. vehicles thant are tuned lower and flexes mores puts out better numbers because the flexing of body pannels act like speakers on the outside.
Ouch! I won't even get into the plethora of issues associated with the walls of an enclosure flexing enough to launch objects into the air. But you're right. And the sad thing about it is just like with panel flex: For every one person who concludes that the enclosure is poorly braced, ten people will conclude that there's no problem, and that it's simply evidence of high pressure. Ironically, the spikes in acoustic impedance that this causes are one of the leading causes of blown woofers.
Trust me, It is. I've modeled extensive scenarios in which I've allowed for one or more of the enclosure walls to radiate out of phase with the driver and the effect is very similar to the "air spring" of a severely under-tuned port. Think of it as multiple acoustically inhibited Fs points which the woofer translates right back into higher resistance when current is passed through the voice coil at a corresponding rate.
In my design calculations, I always compensate for back-pressure, but it only becomes significant with certain design styles and loading arrangements. Obviously infinite baffles are going to be quite sensitive to structural losses around the cabin. Depending on how they're arranged, transmission lines tend to also couple some of the cabin losses back to the driver. Most types of b-pillar walls, standard cab blow-through setups, etc...
@mporettim it only means there box is built poorly.thats sad. i try to teach everyone your sub system is only as good as your enclosure no matter what subs u use.
@mporettim Now I am fully against people putting stuff on there car roof or whatever and filming it bouncing around. Iv done that maybe twice, but its never good to scratch your paint or ruin your phone or video camera.
And as i see someone has rated this vid low because they must not agree.
How they dont agree is the weird thing because it really is commen sence when you look at it. But people just dont want to listen and I can only think of them as childish or whats the word... STUPID for not wanting to listen.
Who knows, perhaps they posses a superior understanding of cabin pressure dynamics and the physics of resonance, which lead them to an opposing conclusion. You'd think that this would call for an in-depth rebuttal. One-staring a video anonymously offers about as much of an insight into any opposing view as the content of my cat's litter box. Hmm... Perhaps that's a message in and of itself.
That may be, but the point of this video is that whatever that--or any car like it--is doing, it pales in comparison to what it could be doing had it not been for all the wasted acoustic energy.
That would be fine except that there's no direct correlation between cabin pressure and the degree to which a given panel flexes. You could for instance project a wavefront that, at the point of impact with a given physical surface, measures 1x10^2 W/m^2, and conduct this experiment in two identical vehicles... that surface will react differently in each vehicle. (Just as a small, low power sub can potentially cause panels to flex more than a large, high power sub.)
i run 3/4 mdf in the roof / doors floor etc on my nissan but i read the new MECA rules for 2010 and thy discourage any reinforcing in front of the "B" pillars i do it for myself but for comps it could be a disqualification
It just goes to show how much of an advantage proper bracing and reinforcement can be. Besides, you compete once in a blue moon compared to how often you simply play music for the sake of enjoyment, so which is more important?
The same way that extreme class competitors do: Replace glass with polycarbonate resin thermoplastics like Lexan or acrylic fibers like Plexi. Some of these can be conformed to the curvature of the glass you're replacing.
Thank you for putting this into words and explaining it so well!!! seriously! To me, a car that flexes is like a box that flexes - its either built wrong or braced wrong. 5/5!
You the man. I may ending up redoing all of my walls in my van with some MDF. Check out some of the vids and let me know what you think. It doesn't really flex that much but the windows are a different story.
MDF is great for sound damping and structural reinforcement alike. As you build your van up, you'll notice a change in loudness and impact that's inversely proportional to the amount of panel flex.
The walls are already thin plywood but Im sure thicker wood can help a lot. I already had some foam that you use as a barrier for homes. It goes between the walls and bricks of a home. I not sure if it helped but I used it.
Great Vid.
Bshizzle88FI4Life 1 month ago
What would your take on sunroofs be?. i have roof flex, but i do have more sunroof flex than anything and i know im loosing alot of pressure through there, any ideas to what i can do to lower the amount of movement without making it look horrible. and keep the sunroof in usable condion
audis4mister 1 year ago
Why does everyone pronounce height like heith?Is it because lenth ends with th?
FATMIKED5183 1 year ago
Gaddamit Hexi you rock my effin world.
fleckx 1 year ago
So, in other words, buy a smart car for your next SPL setup!
Just kidding. :D
ExpertOfSound 1 year ago
Due to this video, I have started deadning / stiffening all doable body panels in my car .
You dont have to accept my videos but they are examples of my " problem " and then the steps im taking to reduce / eliminate my " problem "
TylerTron21 1 year ago
Due to this video, I have started deadning / stiffening all doable body panels in my car :)
You dont have to accept my videos but they are examples of my " problem " and then the steps im taking to reduce / eliminate my " problem " : )
TylerTron21 1 year ago
Pete you are a genius, with an extensive lexicon of audio terminology I must admit. You've definitely proved you're point, and I remember hearing that each millimetre of panel or box movement equal 20 watts of acoustical power loss.. So how can trunk and roof rattling be solved aside from heavily dampening the body with 'dynamat' & Mass Loaded Vinyl, and re-inforcing/bracing the roof and doors with metal or concrete or something... And what about stiffening the trunk latch?
ScrizzDubb 1 year ago
Terrific video.
Thank you HexiBase.
wtfbenny 2 years ago
Also realize that it takes a good amount of pressure to flex body panels. Yea sound is lost through resonating panels and what not, but it still takes a good amount of pressure to make them flex. There arnt many street setups out there that have the power to flex body panels. That said, each car will take a different amount of pressure before it starts to flex. Its kinda a rough way to tell how much pressure there is......as there isnt many other ways to tell from a youtube video...
320bit 2 years ago
More like enlightenment..
txmaxt 2 years ago
hexibase pwns noobs once again
jaysmith850 2 years ago 12
I agree with this video under normal competiton formats except one.and that MECA's drive by spl which is measured from the outside. vehicles thant are tuned lower and flexes mores puts out better numbers because the flexing of body pannels act like speakers on the outside.
safaribass 2 years ago
I've also seen people put stuff on top of their boxes and film it bouncing around. ...cool
mporettim 2 years ago
Ouch! I won't even get into the plethora of issues associated with the walls of an enclosure flexing enough to launch objects into the air. But you're right. And the sad thing about it is just like with panel flex: For every one person who concludes that the enclosure is poorly braced, ten people will conclude that there's no problem, and that it's simply evidence of high pressure. Ironically, the spikes in acoustic impedance that this causes are one of the leading causes of blown woofers.
HexiBase 2 years ago
I didn't know about the acoustic impedance being affected. Is acoustic impedance the same as the impedance seen by the amp or something else?
mporettim 2 years ago
Trust me, It is. I've modeled extensive scenarios in which I've allowed for one or more of the enclosure walls to radiate out of phase with the driver and the effect is very similar to the "air spring" of a severely under-tuned port. Think of it as multiple acoustically inhibited Fs points which the woofer translates right back into higher resistance when current is passed through the voice coil at a corresponding rate.
HexiBase 2 years ago
Well then if "enclosure flex" can affect impedance wouldn't car panel flex behave similar?
Although that might not be significant enough to be measurable.
mporettim 2 years ago
In my design calculations, I always compensate for back-pressure, but it only becomes significant with certain design styles and loading arrangements. Obviously infinite baffles are going to be quite sensitive to structural losses around the cabin. Depending on how they're arranged, transmission lines tend to also couple some of the cabin losses back to the driver. Most types of b-pillar walls, standard cab blow-through setups, etc...
HexiBase 2 years ago
@HexiBase This was the BEST car audio video I've seen on youtube! I was laughing my ass of at 2:30.
I checked out yourwebsite and your info is TOP NOTCH!!
joestl314 2 years ago
@mporettim it only means there box is built poorly.thats sad. i try to teach everyone your sub system is only as good as your enclosure no matter what subs u use.
safaribass 2 years ago
@mporettim Now I am fully against people putting stuff on there car roof or whatever and filming it bouncing around. Iv done that maybe twice, but its never good to scratch your paint or ruin your phone or video camera.
320bit 2 years ago
And as i see someone has rated this vid low because they must not agree.
How they dont agree is the weird thing because it really is commen sence when you look at it. But people just dont want to listen and I can only think of them as childish or whats the word... STUPID for not wanting to listen.
tom58c 2 years ago
Who knows, perhaps they posses a superior understanding of cabin pressure dynamics and the physics of resonance, which lead them to an opposing conclusion. You'd think that this would call for an in-depth rebuttal. One-staring a video anonymously offers about as much of an insight into any opposing view as the content of my cat's litter box. Hmm... Perhaps that's a message in and of itself.
HexiBase 2 years ago
now that is what im talking about 100/5 i tell pepole thay breg about ther flex that your loosing good sounf and db's but they fight that im wrong
mmatsjugg 2 years ago
Very nicely explained. Hope to see more videos like this. thx
SMPSIRSG 2 years ago
NICE ONE!!
flattabang 2 years ago
Good vid. We miss you in the forum.
XmaXimuS
txmaxt 2 years ago
please make more vids like this i learn so much from your vids
thanks!
Poundin346 2 years ago
@PassiveRadiatorsRule
That may be, but the point of this video is that whatever that--or any car like it--is doing, it pales in comparison to what it could be doing had it not been for all the wasted acoustic energy.
HexiBase 2 years ago
@HexiBase love your video's....
ddking69 2 years ago
@PassiveRadiatorsRule
That would be fine except that there's no direct correlation between cabin pressure and the degree to which a given panel flexes. You could for instance project a wavefront that, at the point of impact with a given physical surface, measures 1x10^2 W/m^2, and conduct this experiment in two identical vehicles... that surface will react differently in each vehicle. (Just as a small, low power sub can potentially cause panels to flex more than a large, high power sub.)
HexiBase 2 years ago
i run 3/4 mdf in the roof / doors floor etc on my nissan but i read the new MECA rules for 2010 and thy discourage any reinforcing in front of the "B" pillars i do it for myself but for comps it could be a disqualification
AVNwinner 2 years ago
@AVNwinner
It just goes to show how much of an advantage proper bracing and reinforcement can be. Besides, you compete once in a blue moon compared to how often you simply play music for the sake of enjoyment, so which is more important?
HexiBase 2 years ago
now how to stop the windows form flex .. lol
AVNwinner 2 years ago
@AVNwinner
The same way that extreme class competitors do: Replace glass with polycarbonate resin thermoplastics like Lexan or acrylic fibers like Plexi. Some of these can be conformed to the curvature of the glass you're replacing.
HexiBase 2 years ago
1a!
First2ner 2 years ago
Thank you for putting this into words and explaining it so well!!! seriously! To me, a car that flexes is like a box that flexes - its either built wrong or braced wrong. 5/5!
GeorgiaScion 2 years ago 2
Dude, your a audio/mathematical genius!
NcHalfrican 2 years ago 2
one of the best vids so far man 5star
Ziggetyzag26 2 years ago 2
You the man. I may ending up redoing all of my walls in my van with some MDF. Check out some of the vids and let me know what you think. It doesn't really flex that much but the windows are a different story.
LooseCannon48 2 years ago
@LooseCannon48
MDF is great for sound damping and structural reinforcement alike. As you build your van up, you'll notice a change in loudness and impact that's inversely proportional to the amount of panel flex.
HexiBase 2 years ago
@HexiBase
The walls are already thin plywood but Im sure thicker wood can help a lot. I already had some foam that you use as a barrier for homes. It goes between the walls and bricks of a home. I not sure if it helped but I used it.
LooseCannon48 2 years ago
THANK YOU for explaining this. i hate when ppl rate a car by how much it flex's.
thumpinmagician 2 years ago 11