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Help with box for 2 zvx 18s


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I'm trying to build a box for 2 zvx 18s I would like to try a 4th order but I have no idea where to start. My music is all over the place so I want to flex the shit out of everything and have good bandwidth. List of what I'm working with

2 zvx 18s d2

2 taramp bass 5ks one on each sub.

Stock alt for now.

XS power d7500

PIONEER HEAD UNIT

2 RUNS OF 1/0

2 runs of 1/0 to each 5k as well. 

In a 2003 toyota echo 

40 W x 32 H x 27 D I can use part of the trunk space. 

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First start with the rear chamber. The rear chamber determines what output you are going to get and controls cone excursion below the tuning frequency of the front chamber. The bigger you make the rear chamber, the more low end output you will get and the lower your sealed resonant frequency will be, but as you make it bigger your cone excursion goes up too. It's a balancing act to try to make the rear chamber as big as you can to get the most output, but without having it be so big your subs destroy themselves the first time you play a low note at war volume.  In your case I'd recommend 2.5 cu ft of sealed volume per sub.
 
The front chamber size determines what output you will get around the tuning frequency.  Bandpass boxes let you trade efficiency for bandwidth and vice-versa.  The bigger you make it the more output you get, however you only get output over a limited frequency range. Make the front chamber too big and you get a one-note-wonder. Just how big you should make it depends on the parameters of your subs.  Some subs will give you wider bandwidth than others will using the same size front chamber. Subs with lower QTS and/or Vas will be more peaky than subs with higher QTS and/or Vas, this will make some subs inappropriate for 4th order bandpass box usage. Just how peaky you want the output to be depends on your personal goals and listening tastes.  Everything is a trade off.   For your application 12 cu ft is probably a good starting place, though anything from 8-16 cu ft would be reasonable depending on what you want to do. 
 
When it comes to the tuning of the front chamber you can move the tuning around a bit to get the frequency response you want, but generally you will get best performance with it being near the sealed chamber resonance, this is another reason why its a good idea to keep an eye on your sealed chamber resonance when sizing your rear chamber. Its a good idea to make your front chamber port adjustable so you can tweak the tuning a bit when you get it in the vehicle. Tuning frequency on paper doesn't always work out to what you get in practice and you may want to shift your passband up or down a bit to fit your listening tastes.
 
In terms of port area for the front chamber, you need to have a lot.  All of the output has to come out of that port, so you don't want to lose output to air resistance due to an undersized port.  At 30+ m/sec you can lose half, or more, of your output to port compression  I try to keep port velocity under 20 m/sec if at all possible, though it may not always be.  Depending on how much power is going to be used, this can require ports as big as 1/2 the cone area or larger.  In your case assuming a 12 cu ft front chamber and 10k of power I'd go no less than 300 sq in of port area.

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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10 hours ago, Flexasoraus said:

This is the best explanation I have got so far. Thank you for clearing a lot of stuff up for me. 

No prob, glad I could help!

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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6 hours ago, Flexasoraus said:

Do you have a YouTube channel?

I do not.  I post pictures on my facebook page, but making videos isn't really my thing. 

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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