# 12" Alpine Type R Box Help



## Good

Well, I've built a lot of boxes, but always used the manufacturer specs. I'd like to try something custom and have come up with some numbers using this program:

Subwoofer Box Enclosure Design Calculator - Sealed Ported Bandpass Closed Vented 

and these T/S parameters for the dual 4ohm 12" subs:

http://vault.alpine-usa.com/products/documents/OM_SWR-1242D.PDF 

I tried the Linear Team program, but am missing some required information to understand it as my driver is not in the database...

Anyway, the ajdesigner program says that I need to build a box as follows:

box volume of 1.6135ft.^3
f3 of 27.765
box frequency of 29
and utilizes a port of 3" X 11.822"

Would this be correct? Sound good? Loud? I have WAY more power than these subs can handle, but don't know about this box. Do you have any info that may help? The car is an '05 Chrysler Sebring and will be using 2 subs. Thank you for your time!:coolgleamA:


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## ChrisB

The Alpine recommended enclosure size for your subwoofer is 1.7 cubic feet gross or 1.3 cubic feet net (after taking port and subwoofer displacement into consideration). The recommended port tuning frequency is 33 Hz. 

According to Bass Box Pro, you could get away with as little as .748 cubic feet net tuned to 32.38 Hz. I think that is a little too small and would go somewhere between the Alpine Recommended and the following:

High Fidelity: 2.189 Cubic Feet Net tuned to 23.55 Hz

Extended Bass: 3.094 Cubic Feet Net tuned to 21.57 Hz

Give me a few to check to ensure that I keyed everything in correctly just to doublecheck the box designs.... Also, if you have a set of dimensions that you are working with, let me know and I can have Bass Box Pro do the design up for you.


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## Good

I'm good with approximately 2ft^3 net and I was thinking tuned 30-32hz, but how long do I need to make the port given a 3 or 4 inch port? That's the problem I am having a hard time finding the answer to.


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## Good

Oh, and thanks for your help!!!:jester:


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## ChrisB

If you want to to tune @ 30 Hz, you need a 3" round port 8" long on a 2 cubic foot net box. Your woofer displacement is 0.071 cubic feet and your port displacement is 0.0348 cubic feet. 

If you go with flared ports, your length will need to be 9" in a 2 cubic foot net box. You can also experiment. If you want to tune lower, go longer with the port and if you want to tune higher, go shorter with the port.


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## Good

Yeah, that's what I'm looking for! Thanx for your time! I would imagine this size would sound good as I don't think I can get bigger than this and still keep some semblance of a trunk, with the amps and stuff... (wife's car)

What do you think? Will this sound good, or should I tune to a different frequency? How about SPL? It's not a deebee machine, but I'd like to set off a car alarm or two. How could I tweak this box to sound good, but get the most I can out of it SPL wise?


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## ChrisB

Personally, I wouldn't tune it much lower unless the enclosure was bigger, but that is just me. Then again, going with a bigger ported enclosure would generally give you reduced power handling because it is usually easier to bottom out the sub. 

As for SPL, I haven't worked on a Charger/300 so I can't help you there. I have seen the trunk of an 06 Charger and It had a weird hump it just like my Mustang. At least the Charger has a bigger trunk


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## Good

Very good then, 2ft^3 with a 3" port 8" long, or 9" for a flared port, per sub.

Now for the designing... I have 35"x14" to work with as external measurements. I actually have 37" in width, but wouldn't be able to get the box through the opening, so 35" it is.

Prelim measurements:
External:
35"x14"x19.5"
Internal
(33.5"x18"x12.5"=7537"^3) minus center divider (159.375"^3) [=7378.125"^3]divided by 1728 [=4.269748ft^3] minus speaker displacement (.0696ft^3) and port displacement (.142ft^3) [=4.058148ft^3] divided by 2 for 2 speakers = a rough net of 2.029074ft^3 per sub.

I do, however, want to use the flared port kit here and I say "rough" net, because I don't know the actual displacement of this port in a 9" length. Is this a good choice?:freak:

Without knowing that, what do you think so far?:anxious:


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## Good

One more question, I've angled the backs of *sealed *boxes before, maching the angle of the back of the rear seat to achieve more airspace and more efficiently utillize the trunkspace. The question is this: can I do this to a ported box, or will it adversely affect the performance of the woofer or port sound? I'm just not sure about the wavelengths and reflections, or if it even matters. Thanx. :inout:


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## ChrisB

I have three of those ports awaiting me to get off of my butt and make some enclosures  

Also, if you think you need to angle your enclosure to follow the contour of the back seat and get more airspace you can. You just have to do (Bottom Depth + Top depth)/2 to derive your depth number to use in your calculation. IMHO, the angle will have NO adverse impact on the way the subs sound. IIRC, the worst shape for an enclosure is a perfect cube, but I am sure others would argue with me on this.


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## Good

So here's what I came up with... Not fully wired yet as I needed the dash kit for the HU. I thought I had one, but it was for the wrong year auto, and couldn't find the wiring harness I had either, so I bought new ones today. I'll get it hooked up hopefully today to see how it sounds.  Ignore the mess!!!:blush: And, thanx for your help.


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## Good

Well, sounds real good. Not as loud as I'd like (coming from 2 L715s ported and fosgate power) but sounds good. Thanx for your help...


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## aznboi3644

Alpine specs for the ported boxes suck. The Type R's LOVE big ported enclosures.

If you want more output go with around 2.25-2.5 cu ft per sub with a lot more pore area. IMO I would never go with anything smaller than a 4" round port for a 12" subwoofer.

I put a single Type R 12" in my 33Hz t-line with 1000 watts rms and most ppl were thinking I had two 15's and twice the power.


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