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Specific Box or 4th Order?


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Hey Guys, Im new to this site and have a question about a build I want to do. I currently have a Rockford P3D412,(the discontinued 500w version)in a Q Logic bandpass being pushed by a Mobile Spec 450D amp. Im very happy with the sound as is but I would like to try building either the specific vented box per their website or a 4th order bandpass or maybe even both just to see which I like better.

The internal volume of the Q-Logic is 1.82cf. The website calls for 1.79cf. Will this little bit of volume make a difference in the output, and in the case of it actually making a difference...should I just fab a 4th order?

If it turns out that I should go 4th order, what would the specs be?

By the way I listen to mostly techno with continuous heavy basslines in 4/4 time if that matters for the build.

Any info is much appreciated as I never built a box before but now have brother-in-law who is a trade carpenter and will help me build this.

And if there is anything Im missing, please let me know, Im not very knowledgeable on the technical side of car audio. Thanks.

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The difference in performance between a 1.82 cf and a 1.79 cf box will be inaudible.  Where you could gain performance with a different ported box would be with a different tuning frequency and more port area.  There are two areas that prefab boxes often are found lacking.  If you let me know what the port area and tuning of your current box are, I can give you further recommendations.  

 

As far as 4th order bandpass box goes, if you want to build one just to experiment and do something different, that's perfectly reasonable.  I would not expect it to have significantly improved performance over a ported box though.  The main advantage of a bandpass box is its ability to push all the output through the port.  This is very useful in certain situations, like when doing a blow through or in a car with a firewalled trunk.  Outside of those situations a ported box is going to have better performance 99% of the time.  If you decide you want to try a bandpass box I can give you recommendations for specs. 

"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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Here is the box and the only info I can find from Crutchfield.

I would definitely still like recommendations either way on both builds if you could. 

I've also been thinking about moving up to dual 15's of this same series but first I wanted to try to see what I can do with this single 12 and some other type of box just for kicks. (no pun intended)

Thanks for the help.

Qlogic112Bandpass.jpeg

QlogicInfo.jpg

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I missed the part in your first post where you said the box you have now is a bandpass. I assumed it was ported. The only thing worse than a prefab ported box is a prefab bandpass.  A well designed and built ported box will almost surely stomp all over that. 

"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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40 minutes ago, Triticum Agricolam said:

  A well designed and built ported box will almost surely stomp all over that. 

You have me intrigued. If this is true, which Im going to believe you, then Im definitely going to build something asap. The sub already sounds pretty damn good the way it is now. However, it did take me a good while to tweak my amp in order for it to sound that way based on my musical preferences.
 

So, Im guessing you just recommend sticking to the website spec build, correct?

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13 minutes ago, TechnoBass said:

You have me intrigued. If this is true, which Im going to believe you, then Im definitely going to build something asap. The sub already sounds pretty damn good the way it is now. However, it did take me a good while to tweak my amp in order for it to sound that way based on my musical preferences.
 

So, Im guessing you just recommend sticking to the website spec build, correct?

Actually I'd modify the box specs a bit from what Rockford recommends.  Since you aren't running real high power you can increase the box volume a bit.  2 cu ft is probably what I'd shoot for.  I'd also lower the tuning frequency down from 40 Hz to somewhere 32-35 Hz, though this depends on your musical tastes.  I single 4" port is insufficient IMHO.  I'd increase port area to at least 20 sq in.

"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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So here is a suggestion for a ported box (for a trunk car, sub / port firing back), judging from the rear chamber side of that box you will definitely get deeper bass with this, power: to sub rated, amp subsonic filter to 28Hz, minimum port clearance 1 3/4", figure is just an assembly guide:

NOTE: If building outside you need to build a cardboard dummy box to test fit in it's way inside.

 

image.jpg

1SFPFno45s_zps74ec662c.jpg

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3 hours ago, TechnoBass said:

Thanks for the cut sheet! Should I also route the edges too or does that not really matter?

...and what about a 4th order spec sheet, I would surely like to experiment with one.

 

I can probably come up with a 4th order bandpass design for ya, it might take me a couple days though since I'm traveling. 

"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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