1. ## Predicting pressurization pathways and acoustic coupling.

It occurred to me that my configuration is somewhat unique. Sub woofer firing forward happens to be peaking at 45hz. That's the easy part.
We find our 1/4 wave length to get our front a rear wave into phase at the dash where the car is peaking.

So in theory if we can developed somewhat of a pathway of lowest resistance we can in theory get the front and rear wave to couple at the dash giving tremendous gains in output.

So we know that our peak frequency is 45hz.
We know that the meter is on the dash.
We also know that the rear where is a hundred and eighty degrees out of phase so in order to get the rear and front wave in face the rear wave has to travel 2 times the distance from where the front wave develops to get it to couple but the rear wave.
So let's do the math.

Speed of sound in inches per second over frequency or hz aka cycles per second
13503.937/45=300 inches.
He of that is 150". So from said sorce the rear wave must travel 150s before it reaches the front wave.
The tricky part is creating a low resistance pathway that is the correct length.
the closer we can get it the louder we will be.
Now to the drawing board for 150s..
Last edited by Papermaker85; 05-15-2017 at 06:07 PM.

2. ## Re: Predicting pressure inaction pathways and acoustic coupling.

not going to happen at that distance with that dynamic of an environment. quarter wave theory works well for tuning antennas for propagation in a small footprint and for spl when the port is literally directly in front of the meter.

just my opinion, im in no way an engineer. unless im compared to @papermaker
Last edited by wew lad; 05-15-2017 at 12:43 PM.

3. ## Re: Predicting pressure inaction pathways and acoustic coupling.

not going to happen at that distance with that dynamic of an environment. quarter wave theory works well for tuning antennas for propagation in a small footprint and for spl when the port is literally directly in front of the mirror.

just my opinion, im in no way an engineer. unless im compared to @papermaker
It does happen. You may not get perfect coupling be reinforcement in one shape or another happen s in order to have intensity gains over a 1st and 2nd order where just one wave is pressurizeing the cabin.
Why do you think dubs forward and subs up port back works so well?

4. ## Re: Predicting pressure inaction pathways and acoustic coupling.

They have a show next month. I'm contemplating selling my amp and getting something bigger or reconing the driver to dual 1. I have the hdc3 psi remix in now and with no tuning its easily 146.. just alittle effort and understand ing goes a long way. If i can get the wave to travel 100 inches im good..

5. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by papermaker
They have a show next month. I'm contemplating selling my amp and getting something bigger or reconing the driver to dual 1. I have the hdc3 psi remix in now and with no tuning its easily 146.. just alittle effort and understand ing goes a long way. If i can get the wave to travel 100 inches im good..
just get a big amp already.

6. ## Re: Predicting pressure inaction pathways and acoustic coupling.

not going to happen at that distance with that dynamic of an environment. quarter wave theory works well for tuning antennas for propagation in a small footprint and for spl when the port is literally directly in front of the mirror.

just my opinion, im in no way an engineer. unless im compared to @papermaker
What are you hitting on the dash for the last ******* time so I have a goal to beat!

7. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by Jeffdachef
just get a big amp already.
Its not that easy man.
I have 1 15 and I'm limited to 2k clamped and I can't compete in Stock 7001 up. They have 20k on 4 15s in a big Tahoe. I got a stay in trunk or stock 3500 down. Lol
I could do 2 15s in there but I want to compete with my prototype..

8. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by Jeffdachef
just get a big amp already.
If i had to pick a new amp id probably wreck from stressing what would be louder. Lol

9. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by papermaker
Its not that easy man.
I have 1 15 and I'm limited to 2k clamped and I can't compete in Stock 7001 up. They have 20k on 4 15s in a big Tahoe. I got a stay in trunk or stock 3500 down. Lol
I could do 2 15s in there but I want to compete with my prototype..
get a regulated power supply amp.

10. ## Re: Predicting pressure inaction pathways and acoustic coupling.

At 45Hz you're pretty much dealing with the energy balance in a constant pressure wave expansion or compression process ("pressure is constant throughout the system rule") more than you are the quarterwave theory.

1130ft/sec @ 45Hz = 25 foot wavelength (6.3 foot quarter wavelength).

Now, if you want to build a friggin' giant horn that results in the entire vehicle space being the mouth of that horn, you might be on to to something. You could just build a slowly unraveling ultra-long horn that ends up being the "wall" of your build. Open it up and show people that you have a single high efficiency 15" running off of 800w, loading a tiny compression chamber. You could teach the young ones.

11. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by ciaonzo
At 45Hz you're pretty much dealing with the energy balance in a constant pressure wave expansion or compression process ("pressure is constant throughout the system rule") more than you are the quarterwave theory.

1130ft/sec @ 45Hz = 25 foot wavelength (6.3 foot quarter wavelength).

Now, if you want to build a friggin' giant horn that results in the entire vehicle space being the mouth of that horn, you might be on to to something. You could just build a slowly unraveling ultra-long horn that ends up being the "wall" of your build. Open it up and show people that you have a single high efficiency 15" running off of 800w, loading a tiny compression chamber. You could teach the young ones.
You fimilar with a wave guide ported alignment?
The length of the port is 1/4 of the frequency the systems resonates at.

12. ## Re: Predicting pressure inaction pathways and acoustic coupling.

wish i had pictures. it was in a trail blazer. the port was i wanna say 96 inches long. and the port was on he opposite side 90 degrees leading in phase(port forward subs up not sure on the actual term)
had 2 punch HE2 10s on a opti 1000 and blew the seals out the rear windows.

14. ## Re: Predicting pressure inaction pathways and acoustic coupling.

FYI its not that i'm building the box but placing boards to help guide the rear wave across the trunk 2 times then out the front of the trunk. fron the rear of the cone to the exit of the port is an average of 24 inches when it exits the box (8 inches away from the very left side of the trunk it goes across the trunk 38 inches then back across 38 then forward 32. from the drive with a typical dispersion pattern another 24 inches. so in the round about of. so i should be pretty close if i seal the "wave guild" off fairly good.

15. ## Re: Predicting pressure inaction pathways and acoustic coupling.

Originally Posted by papermaker
You fimilar with a wave guide ported alignment?
The length of the port is 1/4 of the frequency the systems resonates at.
I dabble. There was a commercial product (believe it or not) that utilized a version of that. They were using small aluminum cone drivers, like 5.25" & 6", to make these oddly loaded hybrid subwoofers. It was like a transmission line and a vented enclosure hybrid. But not like the MLTQW versions you may be thinking of. But they basically loaded the cone over the entire passband so that the thermal limit of the driver was truly the limit. Excursion was never an issue.

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