2x12" Alpine Type-R box - diyAudio
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Old 14th September 2008, 09:34 PM   #1
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Default 2x12" Alpine Type-R box

Hello everyone, first post here.

I have two Alpine SWR-1242D dual 4ohm subs. These are a mainstream SPL sub if you're not familiar (imagine most of you are).

I just ordered a OAudio 500w plate amp:
http://www.oaudio.com/500W_SUBAMP.html

and am putting together a box to house these. I was inspired by this thread:
http://www.diyaudio.com/forums/showthread/t-91576.html

The box that I have drawn up has 4.5cu ft for the woofers (net, before driver displacement), with a port which measures 3.5"x16"x28".

I got a rough plan for the port size from this page:
http://www.carstereo.com/help2/Articles.cfm?id=31

This is supposedly tuned to 28hz.

Im looking for advice as to whether the port is properly tuned to 28hz, and if 28hz is even a good level to tune to. This box will be used at our college house for parties which as you might guess, consist of mostly rap and hip-hop.

Simple rendering:
http://www.mattodoom.com/hosted/box1.jpg

Thanks!
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Old 15th September 2008, 08:41 AM   #2
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OK, here we go

This sub would be GREAT for a car.

But not so great for discos of any kind.

Reason - the sensitivity of this type of cab is around 89 dB, compared to 97...99 of that of a good 18" PA sub.

This means your sub needs about 10 times more power to reach the same levels as a PA sub! Or put it this way - outside of car cabin with your sub you'll get around 115 dB at one meter (SPL drops 6 dB with every doubling of distance)- I get about the same result with four 8" 40 W fullrangers that cost around 20/pc. With 500 W PA sub you will get 125 dB - this is twice as loud! A double 18" box would take a kW and wouldn't be much more expensive than those overhyped (IMO) car speakers, and give you 130 dB, in open air. Now that's some serious bass.

But. If those drivers have similar T/S parameters to Eminence LAB12, then they're good candidates for horn loading, and that's another story - THEN you can get around 130 dB out of these. At the expense of more complicated box.
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Old 15th September 2008, 09:36 AM   #3
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Hi Bass-man's!
The real Bass is for the real Man's!
I agree with previous guy :This kind of box is only for the car or home listening or great for the surround dvd system, and not for PA disco sounding or bigger club's because the eff. of this woofers also reached about 90dB maximum.
Here what I made for my loud (hi fi) room listening.
I exploated them both for about 6 years without any problems(I should knock on wood now)
Click the image to open in full size.
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Old 15th September 2008, 09:47 AM   #4
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This combinations of rubber surrounding woofer (Pioneer 12"), and B&C PA 15" woofer sound's great if Phase tuned O.K, You'll get the lowest spectar of Audio with Pioneer 12 " and get some fast and very tight (well defined ) bass from the B&C woofer with different box like in the picture!I feel the bass knocks right in My chest and stomack even I am working out with heavy weights up to 200 KG at raw bench!!!!
Click the image to open in full size.
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Old 15th September 2008, 02:11 PM   #5
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Thanks for your input guys!

The room that these subs will be in is a fairly small one, this isnt a club were talking about, but our house.

The whole reason that Im building the box is because I've had these drivers laying around for 2+ years. Therefor, I would just like to put them to good use.

Do you recommend making some changes to the box configuration to get more out of these?
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Old 15th September 2008, 05:31 PM   #6
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Yes! Make it a horn

What model are they exactly, and could you post their Thiele/Small parameters. So I can make some horn calculations... Just out of curiosity
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Old 15th September 2008, 06:03 PM   #7
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I actually am using one Alpine S-Type in a sealed 1.25 cubic foot box with a Bash 300w plate amp for my home theater sub. I have the crossover set @80hz and I can tell you from just listening to it on movies it is awesome. A computer generated graph can give you an idea of the frequency range that a speaker can play in but I have founf that if you tune it to your tastes, your fine. I know I will get some grief on that statement but in my years as an home theater installer, this is what I have found. Peoples ears tune diffrently and in my business it doesnt matter what a computer graph says, its what the customer says.
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Old 15th September 2008, 08:43 PM   #8
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SWR-1242D

http://vault.alpine-usa.com/products..._SWR-1242D.PDF
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Old 15th September 2008, 09:23 PM   #9
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Default Consider a tapped horn

Ever heard of a tapped horn?

These drivers look like they will work well in a tapped horn enclosure. A proper tapped horn is definitely bigger than 4.5 cubic feet (closer to 20 for both drivers), but will have usable frequency response into the teens and an efficiency that is equal to or slightly better than the ported enclosure.

Tons of information in the "Collaborative Tapped Horn Project" thread here.
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Old 23rd September 2008, 01:04 PM   #10
defwing is offline defwing  New Zealand
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I have been contemplating a tapped horn for my Alpine Type-R 12". I have been playing around in hornresp. I am after low/deep bass, I currently have the x-over set on <70Hz with 350W RMS @ 4ohm although has had 550W in the past. I was wondering what you guys could come up for tapped horn design wise for the following T/S's?

SWR-1221D(2x2ohm)
Fs 27Hz
Vas 58L
SD 467.59cm^2
Sensitivity 87Db
QMS 8.68
Qes .4
Qts 0.38
Le 2.41mH

Cheers,
James.
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