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How do you know if your Jbl SRX718s is dead?

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  • How do you know if your Jbl SRX718s is dead?

    It's the last piece of gear that I would think would crap out on me.  I barely play this thing like brand freakin new.  I tried different speakon cables and nothing..no signal on the amp.  Amp is working for sure..tested it with different speaker.  Is there a fuse or something inside the sub?


  • #2

    lilgrasshopper wrote:

    Is there a fuse or something inside the sub?


    Yes, JBL calls it a "voice coil". 


    "We Have Met the Enemy and He is Us" - Walt Kelly​

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    • #3
      Are you sure your speak-on cable is good and correctly configured?

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      • lilgrasshopper
        lilgrasshopper commented
        Editing a comment

        I"ve switched to a qsc amp and there's a signal but there's no noise coming out of the sub.  So it's gotta be the sub....I couldn't find a failed srx718s on the web....is this weird?


    • #4
      You haven't said if you have swapped or checked the cable and speakon
      <div class="signaturecontainer"><a href="http://www.paradoxband.co.uk" target="_blank">www.paradoxband.co.uk</a></div>

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      • #5
        Oops just read that you did
        <div class="signaturecontainer"><a href="http://www.paradoxband.co.uk" target="_blank">www.paradoxband.co.uk</a></div>

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        • #6

          Yep... Look on the loudspeaker

          You probably have +2/-2 wired on your speakon

          This was also my first thought

          Does the sub say +1/-1 for the speakon?

           

           

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          • Unalaska
            Unalaska commented
            Editing a comment
            A 9v battery across the leads of the speaker can quickly tell you if its working.

            Also verify that the sub s accepting signal on pins1 and not pins 2, its either a physical switch on the back near the input or you'd have to remove the input plate.

        • #7
          I'll open the grille tomorrow and inspect. I've got the sub on +1/-1 setting and the speakons are the cheap kind. Not sure how they are configured. On the qsc amp I tried both the full range and high pass switch...seems to have green led signal blinking but not noise or vibration out of the sub. I tried plugging in both top and bottom speakon "outlet" on the sub. I'm not sure what the difference in using the top or bottom plug to be honest.

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          • Craig Vecchione
            Craig Vecchione commented
            Editing a comment

            lilgrasshopper wrote:
            I'll open the grille tomorrow and inspect. I've got the sub on +1/-1 setting and the speakons are the cheap kind. Not sure how they are configured. On the qsc amp I tried both the full range and high pass switch...seems to have green led signal blinking but not noise or vibration out of the sub. I tried plugging in both top and bottom speakon "outlet" on the sub. I'm not sure what the difference in using the top or bottom plug to be honest.

            You haven't mentioned whether you had the same configuration of amp, cables, and speaker working properly originally. Please confirm.


            On the SR-X (the prior series), the input jackplate is removable, and the switching network circuit board is attached to the speakers with wiring connectors. I've had these loosen. See if this may be the case for your speaker as well. I had to simply snap the connector in and everything worked fine.


            Failing this, the 9v battery test mentioned earlier should confirm whether the speaker driver itself is working.


        • #8
          Thump is correct. Positive voltage on red terminal causes speaker cone to move forward on this model

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          • #9
            Speakons are fine. After the battery test,I concluded that the speaker is fine. Either the board is bad or the neutriks are "loose". In either case, I just ordered a replacement input board....that should work. I'll post my result after I get it wednesday or so.

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            • #10
              Unlikely that there is any problem with the connectors or input board. Did you check the wiring and and amp output configuration?????????

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              • lilgrasshopper
                lilgrasshopper commented
                Editing a comment

                amp is configured *1/-1; the speakons have 2 wires inside so I'm sure it's also +1/-1.  I never messed with it so I can't imagine it's configured anything different.  I've got 2 speakon wires...so there's no way 2 could fail in a row.  Can't wait to find out but I'm relieved my sub isn't blown.


            • #11
              Did you confirm with the battery test at the source end of the speaker cable?

              Did you confirm that you had signal at the 1+/- output terminals of the amp?

              I have a strong feeling that you are barking up the wild ass guess tree with incomplete or inaccurate troubleshooting.

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              • Unalaska
                Unalaska commented
                Editing a comment
                Are you using non-genuine NL4s? Sometimes they will go out of spec and lose contact. I seriously doubt the input plate is the issue.

            • #12

              If the amp is mistakenly wired to provide +2 -2 instead, all he'd have to do was throw the switch and he'd get output. I suspect the NL4 wiring.

              Its unlikely the board is fried. Here is a photo of the inside of a 718. Notice the location of the connector on the board, its in the lower position. This is the same board that is used for the SRX728.

               photo.JPG

              Attached Files

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              • lilgrasshopper
                lilgrasshopper commented
                Editing a comment

                OK, so I got the replacement backplate...popped it in...still nothing happened...then luckily I have an extra speakon that I've never ever used...viola!  It worked...so moral of the story is check your wires thrice if u need to!  Everything works now even the oem backplate. Silly me )  Thanks guys! Always there to comfirm DA's like myself.


            • #13
              Speakon cable came like that. Only one side is like that. Not sure why.

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              • lonotes
                lonotes commented
                Editing a comment

                Yikes! Did you buy the cables new in a factory package? Or were they used when you got them?


              • Craig Vecchione
                Craig Vecchione commented
                Editing a comment

                lilgrasshopper wrote:
                Speakon cable came like that. Only one side is like that. Not sure why.

                Do you have the packaging it came in, or if you purchased online, have a link to where you got it? I'm very curious about how it was described. Does it have a shrinkwrap sleeve on that end that describes the schematic? Some cables have "1+, 1-" or similar to denote which terminals are used.


                It's not too unusual to have a custom cable that may run from the 1+- pair to the 2+- pair, for instance, in order to mate a given amp output to a given speaker input. Such cables would need to be marked at each end to minimize (note I didn't write "avoid") confusion.


            • #14
              New.

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              • #15
                With black/white, often black is 1+ and white is 1- because of compataity with 4 wire biamp color codes. It also follows electrical wiring colors.

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