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Allen mid-range speaker re-foaming -- my experience

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    Allen mid-range speaker re-foaming -- my experience

    Allen HC cabinets all use Peerless midrange speakers, very nice premium drivers with large, heavy metal back-chambers that give them response down to the range of 250 Hz. There has been much discussion of these drivers on the forum. The need for discussion arises because the unit was built with a foam surround which deteriorates with time and must be attended to in some way. Almost any HC cabinet more than 15 years old probably has some rotting and crumbling of that foam, so this issue affects most Allen owners sooner or later.

    The replacement driver can still be bought from Allen parts department. I checked on it just a couple weeks ago at the request of a friend. Problem is Allen wants a LOT of money for these. (About as much as one might pay for a complete used HC cabinet these days.) And I haven't seen them for sale through the typical sources such as MCM and Parts-Express, nor have I discovered a close replacement unit. The old Pioneer midrange with a large back-chamber is NLA, and the Pyle unit that some of us have fallen back on, while cheap enough ($10) doesn't have much output in the 250-500 Hz octave, where the midrange in Allen HC cabinets needs to at least contribute something.

    Now, I've personally been advocating the use of the Pyle midrange, if only because it's inexpensive and fits in the hole (though the screw holes don't line up and you have to improvise on that). And in the HC boxes I've repaired with a Pyle mid, the sound has been perfectly good. I haven't done any side-by-side testing of my Pyle-equipped boxes with the originals, but I can only say that I don't hear anything wrong with them, no apparent deficiencies in output.

    But since so many of you have had your mids re-foamed, I decided to give it a try. I bought a box of 10 surrounds from Parts-Express for about $40, so $4 each. Earlier this week my associate and I spent a little time trying out the process. Here are some observations:

    1. It's easy to prep the unit. Using a flat screwdriver tip, you can scrape away the old foam from the metal frame in a couple minutes. Pulling it away from the paper cone requires a little more patience, but the cone is quite sturdy and I just went around it curling up the edge, tugging on the foam and pulling it away in bits. Then I used a blast of canned air to blow away the debris from inside and outside the unit. We used Q-tips and alcohol to clean the metal frame of the remnants of the old glue.

    2. The new surround is just a tiny tiny bit too big... I've not heard anyone mention this before, and perhaps the two units we picked out of our scrap pile were not typical, but the foam seemed to be about 1/64" too big. We trimmed a hair-width from around the perimeter with scissors, which took a minute or so per driver. Once trimmed, the new surround laid down flat on the metal frame and matched up perfectly with the cone. Before trimming, the surround did not go down on the frame well enough to perfectly mate with the cone. Trimming it solved that problem completely.

    3. Putting on the glue is easy and non-critical. We used the supplied white glue and foam applicators to spread a film of glue around the metal rim and around the cone. After a minute or two of quick drying, we just dropped the surround in place, then used the foam applicator to run around the perimeters of the frame and the cone to make sure the joints were firmly sealed. The cone and coil seem to be held securely in place by the inner spider, so you don't fool with removing the dust cap or shimming the coil on these little units, as you must do when re-foaming woofers.

    4. Before starting to work on each driver, we tested each one with the meter, to make sure the coil measured right at 7 ohms, per spec. Then tested each one with a quick touch of a 9 volt battery to the terminals, listening for a clean pop without any raking of the coil against the pole piece. They both sounded clean.

    5. Today, I plan to connect each one to an organ output (playing nothing but 2' stops) to make sure they work and put out clean sound without distortion or buzzing. I know that a couple of guys have had a buzz in a speaker after doing this repair, possibly due to a voice coil that was already damaged, or due to not getting the foam securely glued to the cone all the way around. If my units sound good when playing, I'll consider them ready to use in the next repair project.

    The entire process for each driver probably took under half an hour, and that was our first try. If doing this assembly-line style, working together we could probably turn out 6 or 8 per hour, so the labor cost is quite small.

    So, if my repair turns out well, I'll probably make this my go-to approach, as it is low in cost, preserves the original specs, and it does head off the need to re-configure the screws. Best of all, in HC-12 cabinets where you have two units mounted side by side, it will not be necessary to overlap the frames or otherwise deal with the fact that the Pyle mids are just a tad larger around the outside edge than the Peerless.

    Will report later. Also, I think I'll do a quick comparison between the tone quality of the Peerless and the Pyle drivers using some A/B testing with 2' and 4' stops only.
    John
    ----------
    *** 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!

    https://www.facebook.com/pages/Birds...97551893588434

    #2
    John,

    I hear the whoosh of a jet heading your direction, filled with Peerless mid-range speakers for re-foaming! Thank you so much for the "how-to" treatise on re-foaming mid-range Allen speakers.

    Admin, can this thread be made into a Sticky? Just a little more information, and I'd recommend it be done.

    Michael
    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)
    • 9 Pump Organs, 1 Pipe Organ & 6 Pianos

    Comment


      #3
      I don't think speakers can be carried on a plane due to the magnets! But regular ground service gets them where they need to go....

      Actually, my point in writing this up was to say how easy it is to do this. I think most people can do their own units without incurring the expense of sending them away. I was genuinely surprised at how easy it was to do, and how nearly fool-proof. I've heard stories about frequent failures when re-foaming woofers, as that is a much more difficult thing to do. But these little mids should be do-able for most people.

      I got back too late today to give mine a test drive, gotta get to choir practice soon. Hope to give them a listen tomorrow and let you know how they sound.
      John
      ----------
      *** 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!

      https://www.facebook.com/pages/Birds...97551893588434

      Comment


        #4
        A part number or link to the surrounds would be helpful.
        -Admin

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

        Comment


          #5
          The Parts-Express part number for the set of 10 surrounds is 260-910. Here's a link to the item on their website:

          https://www.parts-express.com/speake...akers--260-910

          At least one other company sells new surrounds for these speakers, as I've seen the link somewhere on the forum. As I recall, their kit was a lot more expensive. But then there may be advantages to that kit, such as a more perfect fit into the frame, eliminating the need to do the tiny bit of trimming that we did on the foam before gluing it down.

          Maybe someone else has used another type of kit and will offer their thoughts on it.
          John
          ----------
          *** 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!

          https://www.facebook.com/pages/Birds...97551893588434

          Comment


            #6
            Originally posted by Admin View Post
            A part number or link to the surrounds would be helpful.
            Thess links aren't to the Pyle surround, but were mentioned in other threads:These links are old, but all the links worked as of the date of this post.

            John, do you have a link to the Pyle surround kit?

            Michael

            P.S. Oops, posting at the same time as John.
            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)
            • 9 Pump Organs, 1 Pipe Organ & 6 Pianos

            Comment


              #7
              Originally posted by Admin View Post
              A part number or link to the surrounds would be helpful.
              I reported on this same speaker about two years ago. I rebuilt 27 speakers. The midrange and woofers are very simple to do. My midrange came out of the HC12 cabinets and all of the foam had melted down.

              Comment


                #8
                Pipeorganbuilder,

                I went back and read your thread about these drivers. Since you repaired a large number of them, I'm curious to know if they all turned out well, or if you had any that wound up with buzzing or distortion. Reading other threads about this, I see that some of us have had one fail now and then. When I visited with another forum member last year who had rebuilt about 15 HC-12s for his ADC-8000, all 30 or so of his midranges turned out OK except for one, which had a buzz in it after rebuilding.

                The process seemed nearly fool-proof to me, but I suspect that in some cases the old drivers had their voice coils damaged before the surrounds got replaced, or maybe the coils got pulled out of round by rough handling during the removal of the old foam.

                You also indicated that the re-foaming of the woofers was not too difficult. Did they all turn out OK as well?
                John
                ----------
                *** 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!

                https://www.facebook.com/pages/Birds...97551893588434

                Comment


                  #9
                  Here's a link to the Speaker Exchange Peerless refoaming kit.
                  http://reconingspeakers.com/2011/11/...drange-repair/
                  -Admin

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

                  Comment


                    #10
                    John,

                    All of the woofers turned out great and are still working perfect. Only the first midrange speaker buzzed due to me not getting all of the old adhesive removed from the metal. The new adhesive turned loose causing the buzz. All midrange speakers have been working hard for the last of years with no problems. I hope that you will continue to repair the older midranges. They are really nice speakers and the repair kit is very cheap.

                    Comment


                      #11
                      I had a local fellow re-foam my church's Rodgers midrange speakers. The speaker cabinets sit high in the sanctuary, so they cooked over the course of about 20 summers - no AC, so it got hot near the ceiling. I wasn't willing to try it myself, so paid about $170 for six speakers to be done. That was about two years ago, and the results were excellent. IIRC, the speakers are Peerless, also. They sounded horrible before the job, and since no one had played the organ for years, it went unnoticed. I caught it before the coils were damaged, and they were rubbing a bit. I am well pleased with the results.
                      Home organ, same as church's organ - Rodgers 940

                      Sign on my work toolbox that effectively keeps people away:

                      DANGER!!! 1,000,000 OHMS!!!

                      Comment


                        #12
                        I can report that both the Peerless midrange speakers we re-foamed this week turned out perfectly. I connected them to a manual-channel output from a small Rodgers organ in the shop and played the organ through each one. Not loudly, but putting as much power through them as I think they get in a normal situation, where there is a crossover network to keep the bass out of them.

                        No rattles, no buzzing, no distortion. Just beautiful clean sound in the middle audio range. I'm very happy and surprised. I will definitely be doing this from now on with every foam-rotted Peerless mid. And believe me, we didn't "baby" these things in the process. I was actually quite expecting them to buzz, given that we didn't even worry about making sure the voice coils were centered.

                        While testing these, I also tried out one of the small closed-back mids we have been using as a substitute. The one I had on hand is not a Pyle brand, but a clone of the Pyle sold by MCM for a dollar or two less, but virtually identical to it. I will only say that the small unit without a back-cup sounded very different from the Peerless in this admittedly un-scientific match-up. There was obviously a higher low-frequency cut-off point, which you would expect given the very small internal air space behind the cone. And there was quite a lot less treble output too, but that is perhaps insignificant, since the Peerless, as used in HC cabinets, is not expected to put out much treble, the treble being routed to a tweeter. So the little cheap driver sounded "honky" compared to the Peerless, meaning it had a much more pronounced peak in response. But it was loud.

                        Whether or not the cheap driver works just as well in practice, I can't tell you, because I don't have an HC cabinet in the shop that was repaired with one of these. But I do know that when I've used these on a job, I never heard anything deleterious about the sound results, so I don't feel compelled to go back to all my old jobs and jerk those things out of the cabinets. I'll just try to re-foam from now on because it is easier to do than having to re-engineer the mounting to accommodate the Pyle, especially in HC-12 cabinets, where you have two Peerless mids mounted side by side, and the two Pyle speakers have to be over-lapped, unless you trim one of them with a hacksaw.
                        John
                        ----------
                        *** 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!

                        https://www.facebook.com/pages/Birds...97551893588434

                        Comment


                          #13
                          I've been advocating re-foaming the Peerless drivers for years, using the Parts Express Bose 901 surround kits, and certainly others offer compatible surround kits.

                          As to using the 5 to 6 inch sealed back midranges that are commonly available, their specifications indicate they are a REALLY poor substitute for the Peerless midrange unit that Allen used.

                          Typical is the Pyle PDMR5 which has a Qts of 2.43 resulting in a peak of 7.7 dB at resonance (465 Hz). While this might be fine for a different crossover design, it puts that peak right around the Allen crossover frequency, and the speaker should be crossed over at a frequency at least 4 times the resonant frequency (2 octaves above, say around 2,000 Hz) to avoid the peak being extremely noticeable.

                          For reference, the Peerless midrange has a Qts of 0.92 with a resonance of 262 Hz. This gives a response at resonance down 0.7 dB which is inconsequential. And this is appropriate for a crossover which is about twice the resonant frequency, as used in the Allen.

                          The crossover for the HC14/15 suggests crossover frequencies of 520 Hz and 6,000 Hz and thus the midrange is expected to produce signal right around the Pyle resonant frequency.

                          To see if the Pyle's peak is noticeable try playing a reed stop, or perhaps a Cornet, with a fundamental near low C of an 8' registration and play up and down an octave--the shifting harmonic peaks in the formant ought to show up any imbalance caused by the peak.

                          I continue to look for a good replacement for the Peerless driver for new as well as replacement work, since it was one of the best and affordable ones ever available from the mid 1970's through the late 1990's though it did sell to the speaker building market for around $40 when it was still in production, so it was never a particularly inexpensive driver. Other manufacturers used to make sub-enclosures for their midrange drivers (which did not have sealed backs), but those seem to have evaporated as well.

                          The math is pretty simple if you can handle logs--response at resonance is equal to 20 times the log (base 10) of the Qts, or 20*log(Qts). The entire purpose of Qts is to describe the response curve at resonance, and Qts (total Q of the speaker) is a calculation involving the electrical and mechanical Q of the speaker.

                          Comment


                            #14
                            FWIW, I also use the Bose 901 Surrounds, which are a perfect fit for those Peerless drivers; available from different distributors.
                            Can't play an note but love all things "organ" Responsible for 2/10 Wurli pipe organ, Allen 3160(wife's), Allen LL324, Allen GW319EX, ADC4600, many others. E-organ shop to fund free organ lessons for kids.

                            Comment


                              #15
                              For those of you that use the 901 surround replacements -- do you use the foam or the cloth?
                              Rodgers W5000 --- home (currently at church)
                              Rodgers MX200 module --- home (currently at church)
                              Kawai UST7 studio piano --- home

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