Can anyone help me with my 4th Order box? Need to verify measurements

autokraftgt said:

ok here are my thoughts on this as I have been into car audio for a long time. I have zero problems with the blow through concept and it's your truck, do as you wish. With that said, I have a problem with 4th order enclosures and bandpass enclosures in general. Today, those two types of enclosures are for SPL...That's it. They have no real practical use for everyday systems of today. IMO, 4th order/bandpass enclosures are relics from a former era of car audio. They were popular 20 years ago when subwoofers were not nearly as efficient as subwoofers today. Especially when tuned high (45 hz is high) you're able to get high db levels in a very small frequency window. Generally speaking, they sound really bad, but people will be able to hear you from a mile away when playing one of the 4 songs that hit the right notes..not awesome IMO. Today, we honestly don't need to do as much magic to get GREAT spl. Sure, you will get slightly better spl numbers from 4th order/bandpass enclosures, but the HUGE loss of sound quality and frequency range just isn't worth it anymore....it just isn't. In my opinion....I'd build a blow through with a much lower tuned ported box (say...28-34hz tuned) or even a sealed box...(cause lets face it...if you ran a sealed box, all you'd have to do is roll a window down and there....you have a 4th order box with the cabin being your big side. With natural cabin gain, you really wont need the extra SPL the 4th order would provide...but with a ported or sealed...you will have a substage that can be very musical, very dynamic, even transparent, but when needed, you'll also have a substage that will hit with sheer authority with PLENTY of SPL...PLENTY. I've built many bandpass and 4th order boxes in my days....but like I said earlier...it really doesn't make sense anymore......of course, this is simply my opinion. Best of luck!!

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BadRam14 said:

Thanks AutoKraft, This is exactly what I was looking for and you gave me a lot to think about. It has been a long time since I have really done anything this serious in one of my vehicles so I really don't have the knowledge on box building. With that being said, I have contacted Mark at Car audio fabrication to design a box that will get me SPL and be musical at the same time. Thanks again for sharing your knowledge/opinion.

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autokraftgt said:

You're welcome pal, Iam more than confident you'll be able to have great sound quality, extreme flexability, SPL levels that will send ripples to near-by creeks & lakes, and a fun factor that makes me pretty darn jealous. Post pics when this s**t starts getting real!

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BadRam14 said:

I will definitely post pics once I get started. I do have another question that I was hoping you could answer. For a blow through port. If the port needs to be 10" long, is that for what is going on the inside of the box or total length, even if the port is coming outside the box say 4"?

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autokraftgt said:

If your box calculator suggests a 10" port, that will be 10" inside the enclosure. You will obviously have an external port/tunnel to pass through bed wall & rear cab wall but that's more of a passage port to get sub bass into the cab.

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baum said:

just dont forget to put the seam of the boot on the bottom and over lap the joint and use silicone to seal it.

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