Fi Q judgement day (SPL #'s inside)

[T3mpest 10+ year member]

I have a book that breaks it all down at the house... let me try to paraphrase from memory (haven't looked at it in a few years). The pressure of a woofer is highest at the zero point of displacement -- in other words -- pressure and displacement are 90 degrees out of phase. The sub is putting the highest pressure on the port at the 0 position -- also where motor force is the highest.
If you like I can try to remember to bring that book in and scan it for you... to make sure I paraphrased correctly //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

My real world tests show it is true -- I didn't get 6dB from nowhere //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I know the 6db's came from somewhere, my question is where exactly? What factor did change if it's not displacement? For a given frequency if a speaker moves quicker each way moving back and forth a given amount of times over a given time interval then displacement should increase, assuming it isn't running to suspension limits. Anyway if a speaker imparts energy the best when it's close to a 0 position, then a perfect speaker would simply back and forth a VERY short distance VERY fast at tuning. The suspension would be a mess though since it would have to take one hell of a beating since it would be having to stop a speaker that would move 10ft if the suspension wasn't stopping it dead. I guess that's where the super stiff spiders on SPL subs come in... What book was that from I need to do some reading on speakers anyway as most of what I know is from tech papers and my own grasp of phsyics.

 

[sundownz Pro Seller]

I know the 6db's came from somewhere, my question is where exactly? What factor did change if it's not displacement? For a given frequency if a speaker moves quicker each way moving back and forth a given amount of times over a given time interval then displacement should increase, assuming it isn't running to suspension limits. Anyway if a speaker imparts energy the best when it's close to a 0 position, then a perfect speaker would simply back and forth a VERY short distance VERY fast at tuning. The suspension would be a mess though since it would have to take one hell of a beating since it would be having to stop a speaker that would move 10ft if the suspension wasn't stopping it dead. I guess that's where the super stiff spiders on SPL subs come in... What book was that from I need to do some reading on speakers anyway as most of what I know is from tech papers and my own grasp of phsyics.

It's a bit more complex than that... sustained motor force over stroke is STILL important even though the MAX pressure is at the 0 point. Otherwise the Nightshade v.2 wouldn't be 1 dB louder than the Monster prototype in my box //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

The whole picture is pretty complicated... but an understanding of the "basics" can get you started!

The book I referred to is simply called "Acoustics" :

http://www.amazon.com/Acoustics-Leo-L-Beranek/dp/088318494X

It deals with alot of subjects not necessarily related to car audio but I learned some good stuff from it.