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JoRillo
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#1
19th September 2011
Old 19th September 2011
  #1
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12" Sub

So I was wondering. I have my car bass system with 2 12" subs in a box. I was thinking of creating a new box so I got the idea to build two boxs and put one of the 12"s in my studio. Is there any kind of issue with this? Is there any kind of design I would have to follow to do this correctly?
#2
19th September 2011
Old 19th September 2011
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Wattage and impedance are the main issues. I'm not really familiar with car audio stuff - my rather jaundiced opinion is that it is marginally worse than typical hifi audiophool stuff, in that all specs are hyped beyond recognition. So if it says 1000 watts power handling, I would doubt it very much.

Apart from that ... I would look at building infinite baffle boxes. They are less efficient, but you "hear the bass, not the box". Also, design is less critical, because a sealed box is a sealed box. Just make it very strong and heavy.
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19th September 2011
Old 19th September 2011
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If you have access to a box design program and the driver's parameters, you can see if it's possible to get a fairly flat response. But I'd kind of doubt it. Most car audio are designed for maximum output at a very narrow frequency range. What is called a high Q design in that is it very peaky at a particular frequency.
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19th September 2011
Old 19th September 2011
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Vented boxes give your high Q peaky resonance. They are louder, because the driver can move air more freely - but the cost is a resonant peak.

Hence my comments about using infinite baffle to hear the bass, not the box. Not as loud, but in my experience you can overdo subs. A totally closed box minimises resonant peaks. You'll have enough of those from your room itself.
#5
19th September 2011
Old 19th September 2011
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Depending on the Thiel-Small parameters of the driver, it can give a high Q alignment in a small sealed box as well. In fact most small sealed boxes will have a fairly high Q along with a high fc. It takes volume to lower both. But if the driver has a fairly stiff suspension meant for free air trunk or bandpass box mounting, it may not give a low enough fc to be worthwhile. Probably more like 80-100 Hz. Which might be bumpin in a car, but not of much use in a mixing environment.
#6
19th September 2011
Old 19th September 2011
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Hi guys, some misconceptions in the thread which I will try to sort out:


Quote:
Originally Posted by Kiwi View Post
Apart from that ... I would look at building infinite baffle boxes. They are less efficient, but you "hear the bass, not the box". Also, design is less critical, because a sealed box is a sealed box. Just make it very strong and heavy.
It's tru that it is generally easier to get a closed box right BUT you don't hear a bass reflex box more than a closed box. As a matter of fact you don't hear a well built box at all no matter the type. A faulty alignment can bee boomy and peak for both a closed box and a vented box.

Quote:
Originally Posted by Aeolian
If you have access to a box design program and the driver's parameters, you can see if it's possible to get a fairly flat response. But I'd kind of doubt it. Most car audio are designed for maximum output at a very narrow frequency range. What is called a high Q design in that is it very peaky at a particular frequency.
While I'm not that experienced with car audio designs few woofers have such high Q that it is not possible to make a design with good frequency response.

Quote:
Originally Posted by Kiwi
Vented boxes give your high Q peaky resonance. They are louder, because the driver can move air more freely - but the cost is a resonant peak.

Hence my comments about using infinite baffle to hear the bass, not the box. Not as loud, but in my experience you can overdo subs. A totally closed box minimises resonant peaks. You'll have enough of those from your room itself.
The interesting thing is the summed output between the port and the woofer. A vented box can be made well damped or peaky just as a closed box.

You touch one interesting thing though. Vented boxes are often blamed for boomy response and the explanation is found in a flatter frequency response which together with room gain and room resonances (eigentones) creates this. The solution is not going for a max flat vented design but instead making it rolling of early like a closed box design.

By standard definitions infinite baffles are such that the box air compliance is non significant compared to woofers suspension compliance which basically means very large boxes. Most closed box designs are realised as what is called "acoustic suspension" where the box volume can be less than the drivers VAS or say uo to 3xVAS.

Quote:
Originally Posted by Aeolian
Depending on the Thiel-Small parameters of the driver, it can give a high Q alignment in a small sealed box as well. In fact most small sealed boxes will have a fairly high Q along with a high fc. It takes volume to lower both.
Volume or a different driver with higher moving mass and stronger motor.



/Peter
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