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help with 8 autotek m12d4's

Old 05-24-2012, 09:38 PM
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help with 8 autotek m12d4's

I'm buying 8, they're only $45 on audiosavings with free shipping (drop off in US/pick up from Canada). I've been playing with designs for my Alero behind the front seats.

I just sent this message to Autotek on Facebook:

I asked a local audio shop guy about a 4th order wall for 8 M12's. He told me it'd fry the coils and to ask if you do or dont recommend bandpass (2 ported @ 45hz, 1 sealed/each/each). Like this, behind the front seats (the blue line is plexi so you look back and see the surrounds, port above the head rests) https://fbcdn-sphotos-a.akamaihd.net...87306875786_60 0705785_128...30585_1820650142_n.jpg - i'd need to take out the rear door panels for it to fit and i doubt i'd be able to build a floor, i'd probably just put a 1" layer of rubber on the metal so it doesn't screw it up. the subs are only 9.5 lbs, the wood 3/4", maybe mdf lite. box braced with 2x4's.

shop guy recommended this instead

https://fbcdn-sphotos-a.akamaihd.net...87973745786_60 0705785_12832273_110057267_n.jpg

Both are cool, but I really wanted that 4th order wall. The M12 plots nicely from 25-70 Hz in about 2 ported/1 sealed @ 45 Hz, nearly flat.

I don't know what to do anymore. Are these safe for a 4th order? If theyre designed for ported OR sealed than why would both be bad?

The box would cost $500-$600 and it would be about 16 cubes ported/20 cubes 4th order (16 p/1 s). nice design this guy drew up, really cool looking. I still wanted that 4th order wall because I thought it'd be safer for the subs because they'd still have loading below the tune. He said he could do it but it might fry the coils, saying that the bandpasses of the 90's weren't good or something. It seemed he was going to "guesstimate" the port area. I was like um, bad idea dude. he then said i could port towards the floor at that point i was like w.t.f. no. i can send him my visonik 1500w to get fixed. im stuck between what i think is bad advice and what im pretty sure i wont be able to accomplish on my own. my skills are screwy. thanks guys.

specs:
qts .734
9mm xmax
spl 83.2 1w1m
fs (which they called FO) 23.72 hz
vas 98.15L

I also got to listen to a ported 12" on 4k in a golf hatch. Holy christ that thing slammed. It was hard to breathe but I'm a bass head and want more.
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Old 05-24-2012, 10:12 PM
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after talking with a pro/judge (dbdon?) ive decided to just do a ported/angled wall with two stacks of 4 12's wide with the port on top. i didnt know that bandpasses were "distortion monsters".
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Old 05-25-2012, 04:46 PM
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A bandpass will not 'fry your coils'. Neither are they 'distortion monsters'

Truth - a bandpass box masks sounds above its cutoff frequency, thus the term band-pass as it only passes a band of sound. This feature makes it hard to hear it should you over drive your subwoofers which can lead to damage from unknowingly overdriving them.

If anything, you hear less distortion from a bandpass enclosure.
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Old 05-25-2012, 07:06 PM
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-_-

I went from knowing all that, to having a hard time disbelieving it, back to trusting in my own knowledge.

However, for ease of use, I'm still doing a ported wall instead of bandpass. They modelled nearly the same. The guy at the shop didn't want to build a wall, and designed a 3-angled box where the back seat is, non walled, which was cool, but it's not what I want.
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Old 05-26-2012, 11:49 AM
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A ported wall has a better chance of success as it is easier to build and modify. Walls are a pain in the butt to begin with, making it a bandpass just complicates it more.
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Old 05-26-2012, 06:47 PM
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I took the amp in to the shop today. They told me it was fried pretty bad and it would be around $300 to fix. I paid $250 for it in 2007, so I wrote down "I'll pay only up to $100".

I'm losing interest in getting them to build the wall, although I know their wood work is top notch (used to work with them), because I was talking to two shop dudes (not the owner) about sub wiring. I told them "if 4 D4's wire into 2 ohms than 8 will wire into 1 ohm". They disagreed and said it'd wire into 2 ohms and that I'd need 2 amps @ 2 ohms. I was like, no, if (by diagram):

1 D2 = 1
2 D2 = 2
4 D2 = 1

1 D4 = 2
2 D4 = 1
4 D4 = 2

... than 8 D2 = 2 and 8 D4 = 1, and I did tell them I wanted 1 ohm.

Is this correct?

I'm considering the MB Quart ONYX 2K for $239. I was told it was on par with the AQ 2200.

They started talking about 8 ohms into something into something then double something something. I was like whaaaattt? Why can't you just remember that D2 = 1 and D4 = 2 and double from there?

They ended up googling it. I was like, Jesus Christ, should they build this thing? How hard could it possibly be? I'll make a template out of cardboard tomorrow, maybe now.

Considering Alpine Type-E, they're $134.95/pair on audiosavings and look great on a plot after cabin gain in 2 @ 33, like nearly flat from 20 on up (~+6db on & after 30 Hz).

I'm taking out the panelling and back seats tomorrow.

The thing will be right to the floor, where the back-seat passengers legs would go because that way the stacks (25"-ish) would end at the seat height (not including the head rest), and I'd remove the head rests.
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Old 05-27-2012, 11:38 PM
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I think you have discovered that a carpenter is not necessarily an electrician (not that many electricians have a firm grasp on ohms law either)

At any rate, no, I would not let them wire anything.
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Old 05-29-2012, 07:18 PM
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If I can't get the screw in at an angle than what do I do, glue the out of it?
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Old 05-29-2012, 07:23 PM
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I've changed my mind to the Crossfire C5 500w, they look like theyd actually take rms daily. I can get them for $95ish each and 8 comes to $1030 after shipping etc. should i use two amps or one? Is 4k safe with 235a? it was recommended for my car. How many batts would I need with 4k w/235 amps?
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Old 06-04-2012, 06:38 PM
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Sonic is out of Autoteks. I was going to get 2 Obsidian 18's, but they don't ship to Canada.
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