Odd shape box design help needed...

bobduch · 16th November 2009, 02:56 PM

Friend of mine got a new 12" sub for his car (I know this is not auto section,please bear with me) and needs a 2 cf sealed box. He has in place a 1.5cf sealed box. Current box is almost rectangular in shape but does not have parallel side walls. Nice.
So here is my question. He does not have room for a bigger box but could add an irregular shape to the existing box or run a connector to where has has room for a .5cf box. Could he run a tube from the 1.5cf box to another box of .5cf? Or something like that. If so how small in diameter/how long could the tube be? (Tube would obviously be reinforced.) Could he theoretically add a long 4" of 5" diameter tube until he had the extra .5cf? In other words, the air in the sealed box acts as spring. What are the limitations to the shape of the spring?
Thanks,
Bob

PeteMcK · 17th November 2009, 03:37 AM

The best bet is to put the driver parameters (if available) into WINISD and see how much difference the change in box size will make. You'll probably find that there will only be a small difference in the LF roll off, & you'll be able to use the existing box ...

bobduch · 17th November 2009, 03:10 PM

Or just play with fill. I know.
But now I'm curious and want to know the answers to my questions.

Suricat · 22nd November 2009, 06:25 PM

bobduch, I am afraid that creating two chambers connected by a restrictive link will do just this: creating two chambers. You will not be able to directly add the 2 volumes and will err in unknown territories. Unless the link resistance to air movement is neglectable, for example, when adding braces around the inside of a box.

You friend is better off doing a composite panel that will adapt to the car's shape. But before anything, go with PeteMcK advice and simulate in WinISD. You might be very surprised. In anycase, you will raise the total quality factor of the box-speaker assembly (Qt). Who knows, that may be exactly the bass increase you like in your car!

Good luck,

Suricat

16th November 2009, 02:56 PM	#1
bobduch diyAudio Member Join Date: Jun 2009	Odd shape box design help needed... Friend of mine got a new 12" sub for his car (I know this is not auto section,please bear with me) and needs a 2 cf sealed box. He has in place a 1.5cf sealed box. Current box is almost rectangular in shape but does not have parallel side walls. Nice. So here is my question. He does not have room for a bigger box but could add an irregular shape to the existing box or run a connector to where has has room for a .5cf box. Could he run a tube from the 1.5cf box to another box of .5cf? Or something like that. If so how small in diameter/how long could the tube be? (Tube would obviously be reinforced.) Could he theoretically add a long 4" of 5" diameter tube until he had the extra .5cf? In other words, the air in the sealed box acts as spring. What are the limitations to the shape of the spring? Thanks, Bob

17th November 2009, 03:37 AM	#2
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Sydney	The best bet is to put the driver parameters (if available) into WINISD and see how much difference the change in box size will make. You'll probably find that there will only be a small difference in the LF roll off, & you'll be able to use the existing box ... __________________ ‘today… there lives alongside the twentieth century the tenth or thirteenth. A hundred million people use electricity and still believe in the magic power of signs and exorcisms” Trotsky

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17th November 2009, 03:10 PM	#3
bobduch diyAudio Member Join Date: Jun 2009	Or just play with fill. I know. But now I'm curious and want to know the answers to my questions.

22nd November 2009, 06:25 PM	#4
Suricat diyAudio Member Join Date: Nov 2009 Location: Montreal	bobduch, I am afraid that creating two chambers connected by a restrictive link will do just this: creating two chambers. You will not be able to directly add the 2 volumes and will err in unknown territories. Unless the link resistance to air movement is neglectable, for example, when adding braces around the inside of a box. You friend is better off doing a composite panel that will adapt to the car's shape. But before anything, go with PeteMcK advice and simulate in WinISD. You might be very surprised. In anycase, you will raise the total quality factor of the box-speaker assembly (Qt). Who knows, that may be exactly the bass increase you like in your car! Good luck, Suricat

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