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Old 31st October 2009, 09:43 PM   #11
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Really? I assumed that a 12" woofer needing 6+ cubic feet of enclosure wouldn't have low Vas or efficiency...
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Old 1st November 2009, 01:28 AM   #12
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Comparison is where its at if you can't measure response. Just toss any sub/box in the car and EQ it the way you want. What ever your EQ says when you are done is what you want to add to the curve on your new sub. So if you boosted 30Hz then you need more of it. Model the box and your prospective new subs, look to change the curve where you EQ'd it. Yes it is rough because you don't know exactly how many dB, but it gives a good idea. I can get rid of bass easy but I can't make more so I error on the side of more sub.
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Old 1st November 2009, 07:45 PM   #13
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ok ill try this aproach. what if my goal is to drive these subs as loud and as hard as possible till i melted the coils or tore the spider out of them. how would i go about designing a box that would get theis job done?

someone else posted that seems to make sense. if i end up with too much bass i can always just turn the gains down.

in response to the question of " did the kicker specs do anything worthwhile" the answer is no. from what i can tell (and im new at this) the box almost acted like it was doing nothing at all. i was under the assumption that a well designed speaker box will allow you to drive a speaker harder and it will be louder? is this incorrect?

can anyone agree or disagree with the specs i got from gm?
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Old 1st November 2009, 11:29 PM   #14
jol50 is offline jol50  United States
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Actually what tends to happen is a maker will recommend a smaller box so the sub can't xmax so easy. Then it sounds nasty because the response is all humped up like an SPL box...because it is one. Sure it will go loud until you cook it. Larger box will have more bottom and sound better, but it might xmax at some point and eventually trash the sub, depending just how big and what sub. Besides everyone wants to hear they only need .5cf for a 15.
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Old 2nd November 2009, 01:47 PM   #15
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so how can i design a box that will ride right on the edge of full Xmax? if a larger box will have more bass and better sound then i have nothing to lose
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Old 2nd November 2009, 02:02 PM   #16
jol50 is offline jol50  United States
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If you want loud that is SPL. Just get the specs of the sub and punch them into winISD, make a ported box that peaks at 50Hz. Put a subsonic under what the port is tuned to. That should be the most output. It is typical what the manufacturer recommends is that or maybe lightly smaller. You will want a large port.
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Old 2nd November 2009, 10:40 PM   #17
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Can you post the specs for the woofer?
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Old 3rd November 2009, 12:31 AM   #18
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I would not rely too much on published T/S. They can be very inaccurate.

These are the published T/S of a KICKER C15.
Fs = 21.7 Hz
Vas = 272.33L
Qes = 0.397
Qts = 0.383

Got myself one. Brand new. Measured the T/S with my LMS (Delta Mass=260grams weight)
Fs = 23.71 Hz
Vas = 156.75L
Qes = 0.86
Qts = 0.79

The discrepancies in Vas, Qes and Qts are simply amazing.

According to their T/S, optimum loading for Q=0.707 is in a 110L sealed box with F3=39Hz

From my measurements, loaded in the same 110L sealed box will result in Q=1.23 with F3 = 27Hz.

I can work my way round this C15 but it goes to show how unreliable published T/S are.

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Old 3rd November 2009, 01:34 AM   #19
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Mike, that's a ridiculous difference. IMHO, that would indicate either a misprint on the specsheet, a different version of the woofer, or pathetic quality control.

Did you give it some break-in time? Shouldn't make THAT much difference...

If this is a current model, it looks like a prime candidate for IB. I wouldn't mind having a pair that measured like yours.

Sure the specs are for the version you recieved?

And yes, if this is typical, they shouldn't bother publishing T/S information.
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Last edited by tsmith1315; 3rd November 2009 at 01:36 AM. Reason: habitual editor
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Old 3rd November 2009, 02:29 AM   #20
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The simulators can be very accurate if the T/S parameters are correct. I have built boxes and had the FB come in within .5Hz using the measured impedance curve to verify the box tunning.

Rob
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