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Distorting Sounds

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  • Distorting Sounds

    Hi All, again I am turning to you guys for help. Our church has an Allen 301B with with HC 12's. This is not an Allen original installation. I have always gotten some distortion from the high's om the Flute channel. This distortion is becoming worse, it now shows up in the 2' flute all the time where it used to be only at fullest volume. Could any of you help me in finding out if the distortion is coming from the speaker itself or is it possible for amplifier to be distorting just the treble part of the sound? I intend of switching the leads into the amps to see if that changes anything but though I would ask for ideas before I open the organ up. Incidentally I've always had the flute channel turned down lower that the Main channel to avoid the distorting. There is no distortion from the bass and I have has the "bass boost" turned up almost all the way since acquiring the organ in June.


  • #2
    Can you look at the speakers? The speaker surrounds for the mid-range drivers may have rotted away.

    Allen 965
    Zuma Group Midi Keyboard Encoder
    Zuma Group DM Midi Stop Controller
    Hauptwerk 4.2


    • #3
      That's my first inclination as well. The HC12's have two mid-range speakers each and the foam surrounding the cones has probably crumbled away by now, thus the distortion as these cones get quite a bit of movement on a 2' flute, pretty much in the range of the fundamental pitches of those notes. The woofers have probably been replaced already or had new foam put in, but if not they are probably overdue.

      Other causes of generalized distortion include dirty connections in the audio path -- pull each RCA connector loose, dab on a tiny bit of Vaseline on the outside of the jack and on the pin of the plug, wipe it off with a paper towel or Q-tip, and re-insert the plug. Cleaning all the audio connections this way is good maintenance and just might make the sound cleaner too. But I'm thinking you'll have to get those midrange units re-foamed.

      There has been plenty of discussion on the forum about those speakers, and the consensus is that you should save them and replace the surrounds. There aren't any really acceptable replacement units any more, and those were very high quality and quite expensive units.
      *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!


      • #4

        Check the following links, and they will show you what to look for:In one of the photos, you can see the surround of the woofer rotted away with a napkin behind it. In the other, it has been repaired. I don't have a photo of the mid-ranges, but if there are cracks or any missing surround, you will want to have them re-done. I have a fellow who does them for next-to-nothing for me.

        To get into the speaker, the grille should be connected by velcro only (pictured in my photos above), and all you'd have to do is firmly pull to get the grille off. That said however, one of my speakers came to me with the grille drilled to the speaker. I'm guessing that was someone's solution to a rattle.

        Best of luck with your investigation, and welcome to the Forum.

        Way too many organs to list, but I do have 5 Allens:
        • MOS-2 Model 505-B / ADC-4300-DK / ADC-5400 / ADC-6000 (Symphony) / ADC-8000DKC
        • Lowrey Heritage (DSO-1)
        • 11 Pump Organs, 1 Pipe Organ & 7 Pianos


        • #5
          Thanks for the suggestions but I have checked the surrounds and they look to be in good condition. Is it possible that something is wrong with the tweeter?


          • #6
            Yes. You could swap tweeters between the systems and see if the distortion follows one tweeter. Also, there should be a slider-resistor on the crossover for the speaker system--make sure it isn't loose. Check all connections on the crossover to make sure they are solid.