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Yamaha S4115H Speaker Crossover

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  • Yamaha S4115H Speaker Crossover


    One of my music buds has a pair of Yamaha S 4115H speakers. This is a big folded horn design with a 15" woofer and horn. He claims that one of the speakers does not reach a full output (compared to the other speaker). He mentioned testing the woofer outside the cab and it appears to be ok. So that leaves us with the horn and/or crossover.

    I see that the horn xover uses a pad that connects across the inductor. I am guessing that this is used to change the inductance value and thus the crossover point. A 6.8Uf cap and .6mh inductor would yield a xover point of around 2.5Khz. So the pad would then either increase or decrease that xover point?

    For testing, I am suggesting that he disconnect the pad and connect the negative side of the horn directly to the cap/inductor junction.

    Anyone ever seen one of these crossovers before? I am wondering about the value of having the pad.

    Thanks, Tom
    Attached Files
    It's not just an amp, it's an adventure!

  • #2
    I think that they are using the pad to adjust the high freq level as compared to the woofer.

    Page 3 of the manual.


    • #3
      So this pad is acting more like a "volume control" as opposed to changing the xover point. That makes sense!
      It's not just an amp, it's an adventure!


      • #4
        The only x-overs I know of with adjustable frequency are active units. L-pads are usually used to control HF level.
        I'm not ready to rule out the lows yet, a bad coil could affect what the woofer gets. The easiest way for him to troubleshoot this would be swapping between the good and bad cabs. Try the woofer first, then the horn.
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


        • #5
          Yes,thatīs the standard use of the pad/attenuation/level contol in a speaker crossover.
          Even more, see that itīs not a plain "volume control" but two fully independent rheostat sections, which work in opposite ways, precisely the idea is presenting a reasonably constant load impedance to the crosover filter so crossover frequency does NOT change.
          Juan Manuel Fahey


          • #6
            Thanks gents....

            I agree... the first step is to swap out the crossovers in the cabs and see what happens. From there, I will troubleshoot.

            And Juan... I was wondering about the dual rheostats... you answered that question!

            I remember these cabs... they are big, not ideal for mid or vocals, but great for throwing sound over a long distance. I'm hoping we can resolve the issue quickly!

            Again, my appreciation for the quick responses.

            It's not just an amp, it's an adventure!


            • #7
              Classic, "This speaker doesn;t sound like my other one." And of course didn;t bring the other one so you can hear the difference.

              You really ought to invite the guy to bring in the other speaker so you can hear them side by side. He tested the woofer out of the cab and it seemed OK??? How would he determine it wasn;t weak in some regard? I sure as hell would not accept his diagnosis unheard.

              First thing to do is play the same stuff through both speakers and listen what is difference. Maybe the horn driver on one is seized up and so puts out very little compared. I'd do the listening tests before I start swapping out boards and stuff. Maybe someone messed with it first and the horn is out pf phase. Or woofer.

              Don't have HIM doing the tests, unless he is doing the repairs too. otherwise, all we are doing is playing telephone here.

              Ever deal with churches? They often have elaborate sound systems. And a zillion volunteers. So what happens is the sound guy hears a problem with the PA, say the left channel is weaker, decides where the problem in and pulls the piece of gear out and gives it to a volunteer to get it fixed. The vol takes it to another vol who "knows electricity". Mr. Electricity hands it to another vol to bring to you. You ask, "so what is wrong with this, why is it here?" INEVITABLY, that last vol says "I think it is blowing fuses." The problems we are six people removed from whoever decided the unit was bad in the first place. But wanting to be helpful, they will always make up an assumed problem to report. And if I ask some questions I need answers to, they have to float back up the food chain and god alone knows what the original guy hears, and any chance his response will get back to me at all, let alone correctly is remote.

              The fixer needs to communicate with the problem owner. The fixer needs to see the system. As other explained, the L-pad is just a volume control for the horn.
              Education is what you're left with after you have forgotten what you have learned.


              • #8
                and god alone knows what the original guy hears
                Hey Enzo !!!!
                What else did you expect?
                Itīs a CHURCH !!!!!
                Juan Manuel Fahey