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sealed box sounds to small (Alpine Type X


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casaus19 
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Posted: July 22, 2005 at 8:24 AM / IP Logged  
i just made a sealed box for an alpine type "X" 12 for a ford mustang convertible.  i made the box to what the recomended specs showed(still learning box sizes) and the box barely fits in the trunk.  when we hooked it up it sounds like it does not have enough airspace.  and i can't make it much bigger because of fitment issues.  any help on a good volume for that sub or how to make it sound better  would be great
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oonikfraleyoo 
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Posted: July 22, 2005 at 9:44 AM / IP Logged  
I think thats just the way that sub sounds, sorry. I had one for a minute and its a very dissapointing speaker. You could try a ported box, but I'm not sure you could get it to fit if the sealed box barely does.
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placid warrior 
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Posted: July 22, 2005 at 4:49 PM / IP Logged  
how bout adding some polyfill or something, cut a square of it, roll it up and staple it to the corners to keep it as far away from the sub as u can.
ss-installer 
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Posted: July 22, 2005 at 11:59 PM / IP Logged  
i agree, try tuning the box with polyfill. you do have the amp set on low pass right? what is the frequency set at?
placid warrior 
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Posted: July 23, 2005 at 2:30 AM / IP Logged  
yea...if u dont have a crossover or the crossover is set wrong it can sound really cr@ppy too.
DYohn 
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Posted: July 23, 2005 at 9:48 AM / IP Logged  

What makes you think the enclosure is too small?  A small enclosure results in a boomy system that appears to have too strong midbass and less low bass.  In a subwoofer crossed over properly at 80Hz or so, this may mean not much output at all, especially if the enclosure is very small.  Adding polyfill at a ratio of 1 pound per 1 cuft of enclosure volume will increase the effective size of the enclosue by about 40%.  This means a 1 cuft enclosure with 1 pound of acoustic fill will act as a 1.4 cuft enclosure.  And the fill should be between the woofer and the back wall of the enclosure for best effect, loosly filled.  It does not matter if it touches the woofer, except that in very high powered systems the magnet can get hot and the polyfill may burn...

I quickly ran the T/S of that Alpine woofer and it requires a pretty large enclosure.  I got 145 litres (5.1 cuft) for a sealed enclosure (resulting in a -12 db/oct slope below 40Hz) or 146.5 litres (5.2 cuft) ported, tuned to 18Hz (4" port 17.25" long) which gave the best performance.  Relatively flat down to 30Hz, a +2db port peak at 20Hz and -24 db/oct below that.  Impressive. 

How large is your enclosure?

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stevdart 
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Posted: July 23, 2005 at 11:45 AM / IP Logged  
This thread should be renamed something like "Alpine type X enclosure size" so that searchers can see the info here, DYohn.  I know I'd want to find this again if I were looking for some good direction on building a box for these.  :)
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DYohn 
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Posted: July 23, 2005 at 2:23 PM / IP Logged  
you got it. 
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casaus19 
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Posted: July 23, 2005 at 11:32 PM / IP Logged  
so in this case i am really a newb.  the biggest that i could get the box was roughly 1.75 cuft.  if  that subs needs so much air space how am i gonna be able to do that in the mustang when it was hard enough to get the 1.75 box in the trunk.  but those stats are nice to hear thanks.
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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: July 24, 2005 at 9:23 AM / IP Logged  
Alpine recomends 1.75 cuft for this woofer?  That is entirely too small and will turn this sub into a mid-bass at any normal listening volume.  1.75 cuft is probably being recomended because Alpine knows not many people can put a proper size enclosure in their car, and that car audio power is cheap.  If you pump a continuous 2KW into this thing in a small enclosure you may be able to overcome the compliance limitations and create appreciable SPL in the sub frequencies.  But if it was me, I'd use this as a killer home theatre sub in a 5.2 cuft ported system with a 500 watt plate amp.  That would make those T-Rex footsteps shake the fillings out of your teeth.  But in a car, I'd use a different woofer.
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