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Why is my system shutting down?


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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 18, 2005 at 12:12 PM / IP Logged  
The 16-MC2000d "Mojo" amp has both variable low-pass filter and a variable sub-sonic filter.  The "QFC" control may be one of these: check your owner's manual.  But based on the description you posted, "quickly fry coils" sounds like what's happening.  Your amplifier is rated at 2000 watts into 2-ohms.  Whoever told you that Memphis (or any other) speakers can "hold" more power than their rating was a liar.  (Speakers don't "hold" power, they dissipate it as heat and sound.)  Speakers are rated for their maximum sustained power levels and you should not exceed them.  Your scraping sounds are probably the speakers being over-driven (or severe amplifier clipping) and you will soon fry something.  How are your speakers wired and what kind of enclosure are they in?
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AJRXtreme 
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Joined: June 08, 2004
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Posted: December 18, 2005 at 10:22 PM / IP Logged  
They are in a sealed box with 2 seperate chambers(3 in each chamber). each chamber is 6ft^3 . I wired each pair to 2 ohms since they are all single 4 ohm subs. So i have 3 positive wires and 3 negative wires coming out of the back of the box. I twisted all the positive wires together and put them in one positive lead on the amp and i twisted the negative wires together and put them in one of the negetive leads on the amp. Is this still ok?
03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004
godblessdremil 
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Posted: December 18, 2005 at 11:15 PM / IP Logged  
QFC stands for Q factor control according to an amp manual i pulled up. The only "Q Factor" i know of is something i learned in my EE classes is the ratio of energy stored in a resonant circuit to energy dissipated per radian.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 19, 2005 at 10:14 AM / IP Logged  

AJRXtreme wrote:
They are in a sealed box with 2 seperate chambers(3 in each chamber). each chamber is 6ft^3 . I wired each pair to 2 ohms since they are all single 4 ohm subs. So i have 3 positive wires and 3 negative wires coming out of the back of the box. I twisted all the positive wires together and put them in one positive lead on the amp and i twisted the negative wires together and put them in one of the negetive leads on the amp. Is this still ok?

Ah... NO!  You are saying you have three 2-ohm loads in parallel at your amp.  This is a gross overload on that amp as it results in a net 0.666 ohm load.  No wonder your system is shutting down, and I guarantee it is clipping like mad.  Keep operating like that and you will destroy your speakers and might fry the amp too.  You need to re-wire for at least a net 2-ohm load.  With 6 speakers @ 4-ohms SVC, the best you can do is wire for a net 2.666 ohms by connecting all three subs in each chamber in parallel (resulting in 1.33 ohms) and then connecting these two sets in series to the amplifier (totalling 2.66 ohms.)  This is the best way to use the system you have.  Then you can properly set your gain control... and I assume you are using a low-pass filter on the amp or externally?

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 19, 2005 at 10:19 AM / IP Logged  

godblessdremil wrote:
QFC stands for Q factor control according to an amp manual i pulled up. The only "Q Factor" i know of is something i learned in my EE classes is the ratio of energy stored in a resonant circuit to energy dissipated per radian.

Ah.  "Q-factor" in this case has to do with the electronic crossover.  It basically adjusts the rate of change at the peak of the crossover envelope, and in some cases the bandwidth of the filter.

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AJRXtreme 
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Posted: December 19, 2005 at 5:31 PM / IP Logged  

DYOHN thankyou sooo much!! I cant believe how much of an idiot i am! I had each 3 subs wired in series for a 1.34 ohm load and the other 3 also wired in series at 1.34 ohm load before i had my jbl amp on them and the whole time i thought that was a 1.34 ohm load on the amp. I didnt know that you added the ohmage together and thats what the amp was handling. So I should wire my speakers the old way then? for  2.666 ohm load on the amp. When you say to connect the 2 sets of wires to my amp in series, do you mean to connect the positives to the positive on the amp and the negatives to the negatives on the amp?

OK and about using a low pass crossover on my amp. Don't all mono amps have a low pass filter already built into them? Other than that i dont have any external crossovers on my system. Would this be a smart thing to buy? Please inform me on what else I can do to enhance the sound of my system. I also have a subsonic filter on my amp. I have this turned off because since my box is sealed i dont think my subs are going to go too low that they will blow. Is this ok that I have it turned off? Alright thats pretty mcuh all the questions I have. Thankyou everyone for your help, you guys just saved me $1,000+ because thats how much i spent on my amp and subs together. No warrantiesWhy is my system shutting down? - Page 2 -- posted image..

03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 20, 2005 at 11:09 AM / IP Logged  

Yes, you need to re-wire so that the three speakers in each chamber are in parallel, and then the two sets are in series with each other.  I did a little drawing that may help you.. And you need to activate the low-pass filter on your amp and set it to somewhere between 80 and 120Hz.

Why is my system shutting down? - Page 2 -- posted image.

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AJRXtreme 
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Posted: December 20, 2005 at 1:18 PM / IP Logged  

I went ahead and wired my subs like i thought dyohn had told me, but it ended up being wired like this  ... [URL=https://imageshack.us][IMG]https://img284.imageshack.us/img284/7188/oldwiringdiagram0pm.png[/IMG][/URL]

I played my system for about a couple minutes last night and no wierd scratching noises happened at all. I went ahead and started my car this morning to pull it back out onto the driveway form the garage and the subs would play fine. I wanted to hear how my system sounded with the wall layed down flat facing up in the back. I then turned on the car and a wierd popping noise happened from the subs when the amp turned on and then the subs wouldnt work. Both red and green lights from the mojo amp were on. Everytime i turn on the car the popping noise happens once. I went ahead and wired my subs to how dyohn said on the picture he sent and still the pop noise happens whenever i turn on the car. If anyone could tell me what is goin on i would appreciate it, thankyou

03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004
AJRXtreme 
Silver - Posts: 302
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Joined: June 08, 2004
Location: United States
Posted: December 20, 2005 at 1:21 PM / IP Logged  
https://img284.imageshack.us/img284/7188/oldwiringdiagram0pm.png <------- this is how i had my subs wired. What ohm load on the amp is this?
03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004
DYohn 
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Moderator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: April 22, 2003
Location: Arizona, United States
Posted: December 20, 2005 at 2:07 PM / IP Logged  
The wiring you show is 0.67 ohms.  You need to disconnect one - and one + from the speakers (one from each set as shown in my diagram) and connect these to each other and NOT to the amp.
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