Buzzing from Leslie Horn

[Oscar]

I have a C2 running into a FrenkenLeslie (147 but with a custom non-Leslie tube amp). I just replaced the Leslie horn (the old one was missing the reflectors). After installing the new horn, I am noticing a loud buzzing from the horn when I play certain notes (frequencies really). The buzzing occurs when I have the first 3 drawbars out all the way and I play C#, D, and D# 1 octave above middle C.

A couple thoughts on my part:
1) As the custom tube amp on my FrenkenLeslie is more than 40 watts, could the crossover be fried by too much power? Should I be suspicious of a bad capacitor in the crossover?
2) The horn driver is an original Jensen speaker that looks really old, could it be the culprit?

I appreciate any ideas!

[ClavAnother]

For starters, you could give the deflectors a wiggle to see if they are loose. If so, add some glue to the posts.

Also the driver could be dirty. Disassemble it and run a piece masking tape (that is folded backward around a business card) in the groove that the diaphragm sits in. See if it picks up any dirt.

[Sweet Pete]

Take pictures of your work so everything goes back together correctly.

Before taking the V21 apart I leave it hooked up and loosen off and retighten the diaphragm while the offending notes are held down.
Once I pointed the driver throat at the floor and a feather fell out.....
If I still can't get the buzzes out,I remove the diaphragm and use non residue green painters tape.Regular masking tape leaves a residue.
Keep fishing the crud and dirt from the gap till the tape comes out clean.Get a magnifier and flashlight,have a look.Blow compressed air through the gap
before reinstalling the voice coil.

Be careful not to over-tighten the fasteners. The deeper you can get the coil into the gap( 1/2 way is ideal) the better.Newer replacement
V21 diaphragms don't seem to have as deep an excursion as the originals.I use 888800000 the lowest E with C3 chorus as my first test.Any manual drawbar group.
My second test is 88800008 C3Chorus,same lowest E on any manual drawbar group.
My third test is low C pedal drawbars 76 and C triad second highest octave on A preset Swell,and C triad second octave 'root five/no 'E' on Great preset.

Usually if Low E on 8888 manual stops buzzing horn driver,low C on pedals with some brightish voicings usually will sound proper.
Others will weigh in,the V21 is tricky to re-align.While a speaker shop might have a sweep signal generator,it still won't do a better job than your Hammond signal.
Loosen and retighten those fasteners while you run some Hammond through it.

Hope this helps.

[Steve Leigh]

For starters, you could give the deflectors a wiggle to see if they are loose. If so, add some glue to the posts.

I believe that the "standoffs" or "posts" were attached (at the factory) by heating the plastic "posts" with a soldering pencil, and "melting" them to the horns. This is what I've seen on about 150 Leslies. Melted plastic.

The exception is the 31s - they used small wooden dowels.

Personally, I don't even use the deflectors.



If one of those "plastic welds" is loose, you sure WILL hear some buzzing at certain freqs.

Another possibility .... the screws/washers that bolt the upper driver to the shelf. A slightly loose screw will drive you batty trying to chase down that buzz. This also applies to "mount posts" - ie; the upper motor screw/washer "posts", belt tension arm "post", etc.

IF this happens, ie; loose screws/washers - one drop of KrazyGlue (after tightening) should keep you happy for ~25 years.

[Sweet Pete]

Yes,
Steve and Clav Another....mechanical noise is also the reality of a Leslie. Inertia and physics dictate many potential pitfalls.
Worn out lower and upper belts,transmission of vibration through hardened old worn out grommets,bearings dried out...the list goes on.

By building FrankenLeslies from the parts of various models,one learns just how brilliant an engineer Don Leslie was.The best one I built...
went down under.The other one is my auto mechanics daily driver.Both are old,and make some mechanical racket,but overall were in good
enough condition to use on a gig or session.


Krazy glued the tear in the diaphragm of my tweeters in a Yorkville NX520P a few years ago.Have the replacements(RCF) ready to go,but as strange as it seems,
these voice-coils(RCF)mounted with a phase plug are repairable with Krazy glue,in many cases the edge of the dome develops a small tear.

If anyone from Yorkville is reading this.....LOL

Retiring these boxes from back line duty after 13 years of splendid operation.Great little monitors for rehearsals now.

[David Anderson]

The exception is the 31s - they used small wooden dowels.

Actually, virtually all 1950s Leslie horns use small wooden dowels to mount the deflectors. With this type of horn, the horn bearing is pressed into a phenolic pulley. On later horns, the entire horn and pulley were cast as a single piece of plastic, with the deflectors mounted afterwards.