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Best Way to Brace a Box


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soundnsecurity 
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Location: Louisiana, United States
Posted: June 26, 2012 at 10:53 AM / IP Logged  
hey can you do me one more favor? can you model this this box for me and tell me what you think?
same SX15, final internal volume 4.3 cubic feet, 43L x 17H x 18D. port is 4 x 15.5 x 31, tuned to 32Hz.
i had a thought the other day as i was listening to the sub, still with the towel stuffed into the port, thinking about how you said that group delay is basically a difference in output from the sub to the port and i thought what if i just build the box and have the port all the way on the other side of the truck. this is how i had my last system set up and maybe it was just an accident but it sounded pretty sweet. this way i can maybe have my cake and eat it too.
i actually like the way it sounds with the towel in the port but i cant leave it like that obviously because i will eventually have to show this to customers and i dont feel like being laughed at. the sound is a lot more detailed than it was normally so the only thing its lacking now is in the bottom end.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: June 26, 2012 at 12:23 PM / IP Logged  

You bet.  In 4.3 cuft tuned to 32Hz results in an f3 at 30Hz and a response peak at 47Hz.  It would be less boomy than 3cuft (which has its response peak up around 74Hz and may be why you felt the need to turn the Xover down so far.)  A larger enclosure would sound better, IMO.  As far as the towel goes, I can't count how many vented enclosures I've built that ended up with a stuffed port because they just sound better, but they still have more low end than a completely sealed alignment.  Go to the fabric store and get some nice black velvet, use that to stuff the port and tell your clients how hard you worked to determine the exact amount of this custom "subwoofer dampning" fabric to use to critically tune the port for the best SQ in your truck.  They'll be impressed.  ;)

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soundnsecurity 
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Posted: June 26, 2012 at 1:12 PM / IP Logged  
cool. if im not happy with the sealed box then thats what ill probably have to build. thanks again
soundnsecurity 
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Posted: August 04, 2012 at 3:20 PM / IP Logged  
just finished building the 4.3 cubic foot ported box and threw it in the back of my truck. it takes up the whole back seat but it sounds awesome. probably gained around 6db and its extremely clean and smooth. now i need to build a floor so i can take the seats out completely and frame it all in with a nice custom install for the customers to see.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: August 04, 2012 at 6:04 PM / IP Logged  
soundnsecurity 
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Posted: August 04, 2012 at 11:22 PM / IP Logged  
its actually cleaner than i expected because even at full volume there is no "hiccup" between note changes. it just transitions so nicely from note to note. obviously its still not quite as loud as my 18 but that is to be expected.
i think its funny that now that i am having to use their "SXX" version of the SX, now they are releasing the "SX PRO" which is basically the older version SX with new markings. ultimately i might still end up with the SX pro but for now i have the sound that i want.
the only difference between the SXX and the SX PRO is that the magnet will now have the vent hole in the back that they originally started with. do you know what effect this can have on a sub woofer system? honestly i have noticed no other differences other than the covering up of this rear vent and now they want to sell both versions ( covered and uncovered) can you tell me if there is a reason for this and what will be the difference? because otherwise there seems to be no other difference.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: August 05, 2012 at 1:07 PM / IP Logged  
A vented pole piece will allow a smaller voice coil to handle higher power levels because it dissipates heat more efficiently than a non-vented pole.  It allows air flow through the middle of the motor.  In general, it has no impact on the sound of the system, but it can create higher sensitivity ratings because of the smaller VC.
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soundnsecurity 
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Posted: August 06, 2012 at 10:28 PM / IP Logged  
cool, i always knew it was better for power handling due to the added air flow but i thought it might allow the cone to move a bit more freely because i figure that since the center of the voice coil is hollow i thought that the air inside would provide some sort of compression/resistance because the air would have no where to go but through the small gap between the magnet and the voice coil. i figure that having the vented pole would allow air to flow and eliminate any compression inside the motor structure and let the cone move a bit more freely/loosely. thoughts?
also just realized how many views this post has gotten, almost more view than some stickied posts that have been up there for forever and a day, so i hope someone else other than me has learned something.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: August 07, 2012 at 9:59 AM / IP Logged  

soundnsecurity wrote:
cool, i always knew it was better for power handling due to the added air flow but i thought it might allow the cone to move a bit more freely because i figure that since the center of the voice coil is hollow i thought that the air inside would provide some sort of compression/resistance because the air would have no where to go but through the small gap between the magnet and the voice coil. i figure that having the vented pole would allow air to flow and eliminate any compression inside the motor structure and let the cone move a bit more freely/loosely. thoughts?

Well, I can't say that doesn't happen, but it's generally not part of the design reason for using a vented pole piece.  It's about power handling (and costs.) 

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vinchinzo 
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Posted: October 23, 2012 at 12:13 PM / IP Logged  
Bolt it down! =)
When in doubt....kick it!
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