Box for an Infinity Perfect 12

I currently have my Infinity perfect 12 in a 1 cubic foot sealed enclosure, and am building a ported box to compare the difference. The sealed box is to Infinity spec, and the ported box should be 1.75 cubic feet with a 4" by 12.33" port tuned to 32hz. Those are the Infinity specs, but I'm looking for "real world" box suggestions for this sub. Those who have it, I'd like some suggestions based on what your running before I blindly build to those specs. I know that often the manufacturer specs are not always the best for the sub, but more like a compromise. Suggestions?

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2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12

*yawn*

I really should make u do this urself.

But .. since I *love* that subwoofer.. and I happen to already have it modeled in WinISD, here a text representation of what it looks like. I'd give ya the image but its like 3 mb and I'm really not into resizing and what-not..
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Number of drivers : 1
Box type          : Vented
Box size          : 1.750 ft^3
Tuning frequency : 32.00 Hz
Vent              : 1 vent(s)
                    15.77 in length for each
                    4.02 in round
                                                            
                                                            
             Relative                                       
Freq        Gain        SPL                               
[Hz]        [dB]        [dB]                            
20.00        -14.07       81.93                            
25.00        -8.27        87.73                            
30.00        -3.83        92.17                            
35.00        -0.44        95.56                            
40.00        1.78        97.78                            
45.00        2.83        98.83                            
50.00        3.08        99.08                            
55.00        2.94        98.94                            
60.00        2.67        98.67                            
65.00        2.37        98.37                            
70.00        2.10        98.10                            
75.00        1.86        97.86                            
80.00        1.65        97.65    

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my *humble* opinion is that curve looks pretty good. I really only look at 30-80 hz (bass cd's have taught me my ears aren't all that useful below like 30hz or so anyway.... from that you see only about + or - 3db either way.. with that usual vented hump at 50 hz or so.

Now, what WinISD says about a subwoofer response and how it really sounds actually playing (here is where adjectives like 'boomy' come into play) can frequently be two different things and my *personal* experience would say that a smaller, sealed box is the way to go with that sub. I would imagine your 1 cuft sealed box will sound much, much better with that woofer than a large vented monster like the one you describe. *but* I still totally encourage you do to it and post back about what you find.

By comparison, a response curve that looks better:
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Driver            : Infinity Perfect 12.1
Project by        : Owner
Project for       : you
--
Number of drivers : 1
Box type          : Vented
Box size          : 2.000 ft^3
Tuning frequency : 25.00 Hz
Vent              : 1 vent(s)
                    23.88 in length for each
                    4.02 in round
                                                            
                                                            
             Relative                                       
Freq        Gain        SPL                               
[Hz]        [dB]        [dB]                            
20.00        -9.80        86.20                            
25.00        -5.29        90.71                            
30.00        -2.25        93.75                            
35.00        -0.34        95.66                            
40.00        0.70        96.70                            
45.00        1.16        97.16                            
50.00        1.31        97.31                            
55.00        1.29        97.29                            
60.00        1.22        97.22                            
65.00        1.12        97.12                            
70.00        1.02        97.02                            
75.00        0.92        96.92                            
80.00        0.83        96.83                 

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And one that will sound like *garbage* but be really loud:

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Driver            : Infinity Perfect 12.1
Project by        : Owner
Project for       : you
--
Number of drivers : 1
Box type          : Vented
Box size          : 1.500 ft^3
Tuning frequency : 50.00 Hz
Vent              : 1 vent(s)
                    6.00 in length for each
                    4.02 in round
                                                            
                                                            
             Relative                                       
Freq        Gain        SPL                               
[Hz]        [dB]        [dB]                            
20.00        -23.06       72.94                            
25.00        -16.92       79.08                            
30.00        -11.98       84.02                            
35.00        -7.69        88.31                            
40.00        -3.76        92.24                            
45.00        -0.03        95.97                            
50.00        3.44        99.44                            
55.00        6.20        102.20                            
60.00        7.49        103.49                            
65.00        7.33        103.33                            
70.00        6.53        102.53                            
75.00        5.66        101.66                            
80.00        4.89        100.89                     

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Now go
here and learn it, live it, love it.

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"I'm finished!" - Daniel Plainview

Whoops I forgot to explain it:
OK the SPL reading --> assume ur in front of the sub holding a mic about a yard away from it and sub is seeing 1watt.. that is how loud the sub will be in that particular enclosure at that particular frequency.

Relative Gain -->just the variation on a flat-response curve between 20 - 80hz. Personnaly, I look for + or - 3db either way.. (perhaps a more senior member could jump in and tell us what is a good curve for a sub..) I just use +-3 and my results have usually been decent.

Frequency --> well. yea.

Okay peace out man I gotta stop staying up this late.


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"I'm finished!" - Daniel Plainview

Thanks for the info Sedate....I actually do have WinISD pro, but I don't understand enough about the technical aspects of subwoofer design to interpret the results the way I need to yet. I am sure that sealed enclosure will sound better, but I know I need to give the sub more power. I'm only feeding it about 200 watts right now and it is not really that loud at all. I love SQ, but I do want SOME loud bass when I feel like it. Right now, I'm not getting much. I want to try the ported enclosure just to see how much of a difference there is. I can always go back to sealed and provide the sub more power if I don't like the ported sound.

So based on the results above, if you were going to go sealed, you would stick with the 1.75 cubic foot enclosure? Some of those port lengths are LONG....the box will have to be pretty deep.

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2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12

The Kappa Perfect isn't really made for ported boxes, but if you do, you'll most likely have to run the port down the side of the box and across the rear wall to get the propper length.

Paul

Here is the diagram published by Infinity for the vented box specs:

They puzzle me with this.  If you use a port tuning calculator, you'll get a different size port length than what they show here.  Note that they say the driver displacement is accounted for in this size....and I'm going to just guess that the port displacement may be accounted for too....but given that, the net volume would go down to about 1.5 ft^3.  To tune a volume of that size with a 4" round port at 32 Hz would require a longer port.  The pic shown here would be a tuning frequency of more like 38 Hz.

Here's a port calculator you can use to help verify data:  https://www.carstereo.com/help2/Articles.cfm?id=31

Just goes to show you can't go with complete confidence in what the manufacturer recommends.  But as you're working up a box with the program, you will have to calculate and deduct driver and port displacements to get accuracy in getting a port length at the tuning frequency you want to use.  The port displacement shown in the above pic is about 0.1 ft^3....and the sub displacement should be about 0.1 ft^3 or a little less.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

"So based on the results above, if you were going to go sealed, you would stick with the 1.75 cubic foot enclosure?"
You mean vented enclosure right? Yea man that curve looks pretty good, especially for manufactures recommendations... if u had *any* idea what the manufacturer spec boxes JL puts out look like on a graph you'd be amazed how bad some makers recommendations really are.

My final box recommendation to you is a 1.75cuft enclosure with a 3" port that is 10" long.. this will give you a 30 hz tune and a *very* flat curve.. better than the sealed box by far. Post back as soon as you build it and let us know how it does.

Your subwoofer is an outstanding choice.. I prolly don't need to tell you that, but looking over WinISD and using them myself for sometime, I'm not sure if you'll find what you want from more power or a new box. The Perfect is the *most* efficient subwoofer I know of (96 db *in car*) and is an absolutely perfect sub for 200 watts. Forget not that a sub running easy *will* sound better than one running hard. That said, I *hate* it when ppl on here respond to questions about something with "spend another $200" but in your case, I'll tell ya that 2 Perfect 12's is a potent, potent combination and your MTX amp would handle a pair just fine. If you build this vented enclosure and remain underwhelmed.. this would be my next step.

Good luck and keep us posted.


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"I'm finished!" - Daniel Plainview

stevedart:

I've found many port calculators give slightly varying results...
No doubt b/c the formula looks like this.

When I calculate my own ports w/ JL's formula and my trusty TI-83 the only port calc I've used that comes *very* close is... no real suprise here... the one here on the12volt.

jdog:
All the port calculations I've provided were taken from WinISD. If you would like to use a 4" port instead, cut it to 16" long .. forget not that you should leave some distance between the end of the port and the inside all of the box for proper application. ppl here say you should leave the diameter of the port between the port and the back of the box.


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"I'm finished!" - Daniel Plainview