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JBL GT150 15 " subs (Read 13762 times)
J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #45 - 12/05/05 at 12:33:33
 
determining the frequency to port it at will be math stuff, but you defineatly wanna figure out when the waves add completely and tune to that frequency.  In normal 6th order BP you tune the 2 chambers 5-10 hz apart to get a large peak between the two tuning points, however if you can figure out exactly the frequency that both outputs(front and back of cone) sum you can then une to that frequency.
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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #46 - 12/05/05 at 15:20:20
 
cool...thanks. ill try to do some of the math today at work...unless youve already done it
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #47 - 12/05/05 at 18:21:03
 
the problem is with the horn/port thing. I am not sure exactly how it works, seeing as how it is flared port.

There are people on another forum I am talking to who actually know how to model exponential ports so I am talkign to them.

I figured out the chambers rough sizes though for a scaled up to 50 inch square.  the rear chamber(sealed) is 393.75 square inches and the front chamber is 312 square inches.  thats square so whatever the heighth is minus driver displacement...

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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #48 - 12/05/05 at 21:56:22
 
what other forum are you on?
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #49 - 12/05/05 at 22:05:07
 
www.diyaudio.com, its currently down for the count.

I got a picture labeled with the areas and lengths of the WO scaled to 50 inch square.



I also posted somewhere else, can't remember, asking how to model the exponential port.
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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #50 - 12/05/05 at 23:44:22
 
that might work...cant wait to do the build
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #51 - 12/06/05 at 00:58:55
 
the thing I am worried abotu would be the length of the port may lower tuning way down...not sure.
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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #52 - 12/06/05 at 02:55:23
 
every setup has been loudest at 37 to 38 hz. weird cause i tested and retested and found res. freq. to be right around 46 hz
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #53 - 12/06/05 at 03:01:29
 
my car is weird liek that too, resonant around 44 hz, yet loudest in 60hz region.
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #54 - 12/06/05 at 14:47:37
 
I keep getting mixed coments about the WOs actual box type, some people say its clearly a horn, but its small size makes it a lesser horn(in efficiency). Others say it is a 4th order BP with an exponetial port.  

If it is a horn, when you stack them you increase efficiency nto only by 4 db for doubling power, but by 6-9db for some reason.  



Another option for porting would be out the front, rather than worry about the horn path at all, simply vented out the front would allow you to focus on the summation of the waves.
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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #55 - 12/13/05 at 01:00:20
 
well j_rock...ive finally got off my arss and started the build!!! 2of them will fit quite nice but fitting a third one is gonna be hard...but im tring it ayway!! thanks for all your help! -dan-
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #56 - 12/13/05 at 01:01:25
 
I demand Pics!

Are you building them all at once? or building one to see how it performs than adding more later?

I really wanna come see them too!
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db_audio
Ex Member



Re: JBL GT150 15 " subs
Reply #57 - 12/13/05 at 15:54:29
 
ive started on one...but all 3 will be built before the installation and i test and tune everything... will send pics soon prob this weekend!
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J_Rock
Ex Member



Re: JBL GT150 15 " subs
Reply #58 - 12/26/05 at 21:12:26
 
ANY Updates?
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Learner_UK
Ex Member



Re: JBL GT150 15 " subs
Reply #59 - 01/15/06 at 10:14:54
 
Where have you got all these JBL drivers from??!
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