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Replacing felt and foam on Leslie 145 main back panel

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    Replacing felt and foam on Leslie 145 main back panel

    I am trying to correct a cabinet vibration issue on a 145 when running in high speed. When I refinished the cabinet a few years ago, the felt was fixed with Elmers and then it hardened the felt. So, I have just removed all that and am starting over. Should the felt just be stapled in place? What thickness felt is best to use here? Also, around the motor box, I had used that dense grey door sealer foam. This also does not seem to be the correct type of foam to use there. What type of foam would be best? Can anyone help?

    I have turned the upper motor mechanism around 180 degrees since it was touching the box when it went into high speed. This has fixed my vibration problem, but I still have a flutter issue at high speeds which I can hear at low volumes. The tweeter horn has the extra end pieces (I am not sure what they are called). I wonder if removing those would help? Does any one have experiences with this type of horn baffle?


      The original felt strips for the back panel were stapled in place.

      For the motor box, most hardware stores have a selection of different types of foam. I can't recommend a particular product for you to use.

      I'm not sure what you mean by "flutter." It's normal for there to be some wind noise with the Leslie horn on Fast. How would there not be? Leslie cabinets were designed to be used in churches, not to have someone sticking his ear right up to it. They will never be completely silent.

      The deflectors on the ends of the horn are there to make the ends of the horn the apparent sound source. This helps create the Doppler Effect you get from the horn. Without those, the sound source appears at the center of the horn, and you get much more of an amplitude modulation effect vs. frequency modulation. The effect of the horn is more complex with the deflectors on.

      I have a couple of Leslie horns that have been "mutilated" by having the deflectors removed. If you really want that sound, I'll gladly trade you a horn from which someone else (not me, certainly) removed the deflectors for an intact one.
      I'm David. 'Dave' is someone else's name.


        Thanks for the great explanation of the tweeter horn David. This 145 cabinet was a real beater when I bought it, and it had one of those "mutilated" horns inside which I replaced. As I recall it was busted, and I threw it in the garbage and bought a new assembly. I have always positioned the Leslie sitting right next to the organ in my home. So I will move it around the room to see what it sounds like. I am really amazed at the power of these speakers!


          Was there any dampening insulation inside these Leslie speakers originally?


          • David Anderson
            David Anderson commented
            Editing a comment
            There was a little bit of paper dampening inside the woofer enclosure to damp back waves from the woofer. It smooths the frequency response on the lowest notes a bit. It was stapled to the underside of the horn shelf and it often missing these days. You can use polyester batting if you want, just a thin layer. You're not trying to fill up the space like you sometimes find in a sealed-box HiFi speaker. Different principles.

          • AndyPanda
            AndyPanda commented
            Editing a comment
            There was also a little wispy web of cotton fluff glued inside the actual horn to tame the high frequencies a tiny bit.

          On a side note half the Leslies I have had have the reflectors removed?


            My 122-V came with no deflectors.
            Fortunately the taller horn cabinet facilitates easy swap-out with a deflector horn without needing to drop the horn driver from below.
            I had a deflector horn in there for a while, but swapped it back to no deflectors as it provides more of a Rock n Roll Jon Lord type of sound - more swoosh on the highs. The excessive amplitude modulation can be mitigated by miking further away.
            1971 T-202 with Carsten Meyer mods: Remove key click filters, single-trigger percussion, UM 16' drawbar volume correction. Lower Manual bass foldback.
            Korg CX3 (original 1980's analogue model).
            1967 Leslie 122 with custom inbuilt preamp on back panel for 1/4" line-level inputs, bass & treble controls. Horn diffusers intact.
            2009 Marshall 2061x HW Plexi head into Marshall 4x12 cabinet.

            1964 C3
            196x M-102
            197x X5
            197x Leslie 825


              For those of you with horns that are missing the deflectors - here's my simple and cheap solution:
              I have had good luck making new deflectors out of card stock (heavy paper) that I cut into a circle then cut out a pie wedge and glued into a shallow cone (using a real deflector as my model) - then I use the shaft of q-tips as the standoffs to hold the paper cone to the horn. It works great and painted black looks just like the real thing if you don't get too close and sounds exactly like the real thing.

              I don't bother to make one for the blocked off horn (only one of the two horns is an actual horn, the other one is just a counterweight for balance). On the dummy horn side I just use a little blue tack (poster stick-um) behind the flair of the horn and then spin at high speed and adjust the amount of putty with trial and error until there is no vibration at fast speed. Or you could certainly make a second deflector for the dummy horn but you'd probably not get them identical weight and still need to use some putty to balance.

              Here's a picture of one I made about 15 years ago and still working great. Yikes! I need to clean inside the bell of the horn!
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              Last edited by AndyPanda; 08-26-2019, 09:19 PM.


              • glensound
                glensound commented
                Editing a comment
                ...very cool recreation !!!

              I've seen Dr. Kemp order just the deflectors to repair the horns. Write to him and ask where he got them. Some guy on FB is 3D printing them.

              For the upper motor knocking the motor box, staple or glue some thick door gasket in the area where the knocks occur.

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              To cover the horn driver, you can use fiberfill, the white fluffy material used to make quilts and then get some felt and staple the felt in place covering/holding the fiberfill.

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              You can also use some felt cut into strips to line the mating surface of the back panel and staple that in place.

              If you use a staple gun, use STAINLESS STEEL staples so they won't rust over time.

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              To clean the inside of the horn, use a baby bottle brush with some soap and warm water.
              Click image for larger version

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                Good stuff. I can understand a lot of mods to Leslie's just in general. Most of the time it seems to do more harm than good.


                  The source of the 3D-printed deflectors is Ricky Rininger.