The most optimal 12" Alpine Type R SWR-1242D box design

[HomeLite 10+ year member]

Hello caraudio peeps!

OK, so with no real space constrictions, what is the best box for the 1242D? The recommend 1.7 tuned to 33hz with a 1.25" port width. I hear they like bigger enclosures plus I'm thinking that 1.25" is really narrow. I like my bass low so somewhere in tuned to low 30's is good. Thanks!

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[RAM_Designs 5,000+ posts]

2.25ft^3 at 32hz.

 

[Vagomire 10+ year member]

Maybe you should ask Alpine..

 

[RAM_Designs 5,000+ posts]

Maybe you should ask Alpine..

Most mainstream manufactures are going to recommend smaller boxes and higher tunings so they peak high and don't take up much space(so you can fit more of their product).

 

[Vagomire 10+ year member]

Most mainstream manufactures are going to recommend smaller boxes and higher tunings so they peak high and don't take up much space(so you can fit more of their product).

Makes sense..

As for the 1.25" wide port, my port for my 12" kenwoods is supposed to be 1-3/8 and I built it like that and it sounded great! I should have built the box a little bigger and the port a little longer but it did hit the mids very well

 

[HomeLite 10+ year member]

Sweet! So I was trying to get this all designed using the RE L port calculator but it seems to be a bit off. I put in the Alpine specs and it came up with a tuning of 30.9hz and 1.49 cubic feet. Is this just due to not factoring in the driver displacement? So how would I get accurate measurements? Also what should the port width be? So would a 12"x2" be enough for little port noise and not be too big?

 

[HomeLite 10+ year member]

Oh, ok so the 1.25" will be fine? Coolio. Deranged, your signature gave me such a laugh!

 

[HomeLite 10+ year member]

Oh and is it 2.25 cubic feet after or before port and driver displacement?

 

[RAM_Designs 5,000+ posts]

You'll probably need more port area than the Alpine box says to have.

 

[HomeLite 10+ year member]

OK! I think I have it! Tell me if this makes sense:

23.9" wide

14.5" Tall

16.5" depth

2" port width

33.5" port length

2.53 cubes gross

1.77 cubes net

Tuned to 32hz

 

[HomeLite 10+ year member]

Or would one with 17.5" depth and a 28.5" length port be better? Is that correct for the tuning frequency? I calculated this by using the RE calculator but I figured out that it wasn't factoring in the wood that was used in the port, so I subtracted an equal amount of volume and looked at the tuning frequency that gave me. But I just threw the volume and tuning frequency into a different calc and it gave me a length of only 18" for the vent. What's going on here?

 

[RAM_Designs 5,000+ posts]

You also need to take sub displacement into account as well. Use the 28.5" port length, but make the box 26"wide, and you'll be sitting pretty at ~2ft^3 and a 32hz tuning.

 

[HomeLite 10+ year member]

You also need to take sub displacement into account as well. Use the 28.5" port length, but make the box 26"wide, and you'll be sitting pretty at ~2ft^3 and a 32hz tuning.

My calculations may be off but I think that's what it is with 23.9". Grr math! lol

Is this correct?

Gross is 22.4*13*16 = 4,659in^3/1728 = 2.69ft^3

Port displacement: 13 (Height) *2.75 (Port width+wood width) *27.75 (Port length-front wood width because it's already factored in with gross volume) =.57ft^3

The sub displaces .071ft^3 according to the alpine manual

So that totals .64ft^3 of total displacement Leaving 2.05ft^3 space right?

The reason why I was using 23.9" is only because it would be really easy to cut from a full sheet

 

[iLL Ridge 10+ year member]

the re calc does take the wood volume for ports and enclosure into effect. It does not do driver displacement.

 

[HomeLite 10+ year member]

the re calc does take the wood volume for ports and enclosure into effect. It does not do driver displacement.

Are you sure? For my box it says that the displacement is 759in^3. I could be completely wrong about this but wouldn't the calculations for a 2"*13"*28.5" be 2.75(.75 for the piece of wood that's in the box)*13*27.75(because .75 is not actually in the box)? That gives me 992in^3. or if you just take the volume of the wood 14.75"(L1)+10"(L2) = 24.75*.75*13 = 241.31in^3 just in wood. Now the air that it displaces is 741in^3 so how does that work?

I used this method and the driver displacement and accurately compensated for the difference between the tuning frequency of the RE calc and the Alpine manual. Because the RE was showing 30hz and Alpine was saying 33hz. The .07cu^3 driver displacement doesn't explain the big difference. If you factor that plus the wood, you get 33hz. Idk, just my findings