Vehicle Body Panel Flex: The Disambiguation

To all my car audio viewers: If there's one video that I hope you watch and pass on to others, it's this one.

Category:

Education

Tags:

• HexiBase
• PWK Designs
• Pete
• Peter Kulicki
• Body Panel Flex
• Bass
• Warp
• Rattle
• Loss
• Disambiguation

[mporettim]

I've also seen people put stuff on top of their boxes and film it bouncing around. ...cool

[HexiBase]

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.

[mporettim]

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?

[HexiBase]

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.

[mporettim]

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.

[HexiBase]

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...

[jaysmith850]

hexibase pwns noobs once again

[thumpinmagician]

THANK YOU for explaining this. i hate when ppl rate a car by how much it flex's.

[Bshizzle88FI4Life]

Great Vid.



[audis4mister]

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

[FATMIKED5183]

Why does everyone pronounce height like heith?Is it because lenth ends with th?

[fleckx]

Gaddamit Hexi you rock my effin world.

[ExpertOfSound]

So, in other words, buy a smart car for your next SPL setup!

Just kidding. :D

[TylerTron21]

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]

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 " : )

[ScrizzDubb]

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?

[joestl314]

@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!!

[wtfbenny]

Terrific video.

Thank you HexiBase.