How an Electrodynamic Loudspeaker Humbucking Coil is used to Mitigate Hum

[@alcinobras]

Congratulations for the high quality video explained.

[@RestoreOldRadios]

Thank you very much! Best, Don

[@nfijef]

This must have been where Seth Lover came up up with the humbucking guitar pickup concept. Shoulders of giants. Thanks Mr. Don!

[@RestoreOldRadios]

Thank you for watching this interesting science concept. Best, Don

[@FluxCondenser]

Now there’s a demo that went the extra mile, but still wasn’t satisfied and did yet another lap! It was helpful and entertaining to see not just an exploded diagram, but an actual speaker taken apart to reveal the individual parts. You could have stopped there, but you then did a live demo with the separated parts. And then showed a demo with a non-deconstructed speaker. And then gave us a diagram just to clear up any remaining questions. Fantastic work as always!

[@RestoreOldRadios]

Thank you. It was fun seeing how this works and already having one broken down made it easier to pull together. Thanks again for watching and I see you changed your YT channel name; very cool. Best, Don

[@y_x2]

Thanks for this unusual subject.

[@RestoreOldRadios]

Thank you for watching and your feedback. All the best. Don

[@josevaldes5002]

Love your videos and knowledge...thank you...

[@RestoreOldRadios]

This one was a learning experience for me too and worthy of sharing. Thanks again Jose for watching and reaching out. Take care and stay well. Best, Don

[@bradleyleben7785]

At 6:01 sounds exactly like my dad’s old electric razor. That what he would tell the technician a the radio store 60 years ago.

[@RestoreOldRadios]

Bradley, a cool story and thanks for sharing it. Best, Don

[@davidedwards5461]

Don that was a really interesting one. Many thanks but please keep them coming during this period of "self isolation" we are all going through. Stay safe and best wishes from Scotland. David gm4glg

[@RestoreOldRadios]

It was a learning experience for me too. Hopefully you find other content on my channel that adds value or entertaining. Hope to have a few new videos posted soon. The social distancing is a big change for sure. Stay safe too David and all the best. Don

[@AllAmericanFiveRadio]

Very good information and important. There is so much information to talk about with this hobby, it is impossible to run out of material. Great demo!

[@RestoreOldRadios]

Thank you Rick. I agree on the material, many things to discuss and learn from. Best, Don

[@cassvirgillo3395]

Hello Don, Looks like your doing well in these uncertain times. I'm sure I sound redundant, but, Thank you for sharing your knowledge of radio circuits and their operation. Very informative and great demonstrations. A good time to stay home and work on Restoring old Radios. Be safe, C.

[@RestoreOldRadios]

Cass - we're doing okay. I was hoping the demonstration would help clarify how the theory works in the real world. This gives me something to look back on myself for reference too. Take care and thanks again for your kind words. Best, Don

[@hestheMaster]

Great video Don. It explains a Electrodynamic speaker setup and what you can do to mitigate hum.

[@RestoreOldRadios]

Thank you. I appreciate you watching. Best, Don

[@Backtothefutureradios]

Great demonstration and explanation of the speaker setup in vintage radios....the humbucking coil has always confused folks...including me! lol.....Speakers have always fascinated me...but, I know so little about them...I need to study up on them some! Thanks for sharing the video and info!!! Take Care--Larry

[@RestoreOldRadios]

Thank you Larry. Since I seem to forget things these days, it will be a resource for future reference as needed. Best, Don

[@deanschmeltzer9620]

Thanks Don love the tutorial. I have used a compass recently doing my first field coil rewind ,as you did a while back. It worked the first time. Thanks to your information . Thanks for your time. I think I see a antenna coil wind I my future. Thanks again ...... Dean

[@RestoreOldRadios]

I appreciate it Dean and hope your antenna coil wind goes well. Stay safe and thanks for watching. Best, Don

[@preiter20]

Thank you for this video. I have one radio that has an issue with either the speaker or the transformer and this will help me troubleshoot!

[@RestoreOldRadios]

Paul - I hope you’re able to isolate the trouble. Reach back out if you need anything. Thanks for watching. Best, Don

[@tinkeringwithelectronics]

Thanks Don, right down my alley

[@RestoreOldRadios]

I appreciate it Josh. All the best. Don

[@RadioRetired]

Great info,, thank you. There’s more to it than I thought.

[@RestoreOldRadios]

Thank you. I learned a lot myself. I appreciate you watching. Best, Don

[@sc0or]

It’s possible to inject a hum directly into a voice coil from an amplifier (with a correct phase). With a same technic engineers usually use the injection to reduce s hum produced with an amplifier;)

[@RestoreOldRadios]

I’ve never tried it, so I can’t say one way or another. It definitely gives me something to ponder. Best, Don

[@davidjones9730]

Thanks for the great and informative video. Can you let me know what App you used with the old telephone pickup microphone. I have one and this might be a good use of it. Thanks again. Stay safe.

[@RestoreOldRadios]

David - for IOS devices: Speaker Pop Version 4.0.0 Hope this helps and thanks for reaching out. Best, Don

[@jmasseys]

Hi Don, Thank you for your explanation. It explains perfectly the hum I am experienced on a 1936 Silvertone console. I thought I was looking at a problematic humbucker coil (low volume hum at zero volume) but I now know that isn’t the case or it would now work at all. The question I have to ask the owner is if he wants to replace the speaker with a permanent magnet type. My question is, and I know it’s a loaded one, do you think by replacing the speaker will further reduce or eliminate the hum? I assume so. Thanks again for your sharing your experience, Scott

[@RestoreOldRadios]

Hi Scott - thanks for reaching out. Do you plan to use the old field coil as the choke? Best, Don

[@jmasseys]

@@RestoreOldRadios Hi Don, I was, assuming I can fashion a suitable mounting, but I am not apposed to replacing it with a more standard choke. It will become a cost/benefit decision for the owner. Replacing the 10 inch speaker won’t be cheap. I may have an 8 ohm permanent magnet candidate that I repaired a number of years ago, but I do not know the original speaker ratings. I think my candidate was for a guitar amplifier. It probably wants a lot of power to develop full response. It might be ok if the radio amplifier can support it. It’s a push-pull design using 6F6Gs. So yes, if I can, I’d remove the field coil from the original speaker basket, fashion a mount, remove the humbucker coil and rewire the speaker’s audio transformer to the speaker would be the plan. Of course, I’d need to verify the speaker’s ratings to avoid a bigger problem. Can I simply compare the DC resistance of the voice coils? Seems like that’s not enough. Sorry to ramble on. I’ve been getting conflicting opinions on humbucker mitigation probabilities to eliminate hum. I am of the opinion that it’s an imperfect solution when speaker technology was evolving and low volume, 120Hz hum was fairly common. Thanks again for your thoughts, Scott

[@RestoreOldRadios]

Scott - I assumed that was your plan, but I just wanted to confirm. Low level hum and hum in general is somewhat common for the receivers for this period. I'm assuming you've already recapped the receiver? To estimate the existing loudspeaker (LS) impedance w/ the LS disconnected from the output transformer, measure the DC resistance (DCR) & multiply by 1.25 to approximate the impedance. Many folks use this M&P or as a guideline they use 3.0 to 3.5 ohms of DCR is = to a 4 ohm LS and 6.0 to 7.5 ohms of DCR = to a 8 ohm LS. You may try disconnecting the voice coil leads (only one needs to be disconnected) from the existing LS and jump in your replacement LS (substitute) and see if the hum improves before going to the trouble of breaking it down or installing an equivalent choke. Hope this helps and feel free to reach out anytime. Best, Don

[@jmasseys]

@@RestoreOldRadios Hi Don, It does help a lot. That is how I was thinking but I didn't have a method to approximate speaker impedance. Now I do. Thank you very much. I have recapped, replaced more than a handful of "dog bone" resistors and changed the 6V6 amplifier tubes to 6F6s to return it to the original design (Someone before me did some work on the set, the output tubes mainly), but it's mostly original. I think the 5V4 rectifier tube is a bit tired on one side because the ripple is asymmetrical. I popped a 5U4 in it's place as a test and that produced a symmetrical waveform but it really had no affect on the hum level. My thinking is the only way to "cure" this one would be to either crack open the speaker and figure out a way to add or remove turns from the humbucker coil (a task I do not want to try) or simply replace the speaker/reconfigure the field coil and go from there. My guess is the owner will live with it as it is. It's not that bad. Thank you again for helping me with this somewhat academic discussion. I really do appreciate your time. Cheers, Scott

[@RestoreOldRadios]

Scott - Glad to help. I hope things continue to go as planned and thanks again for watching/reaching out. All the best. Don

[@mattvoce1091]

I’m sleeping now your voice is so sleepy

[@RestoreOldRadios]

Hi Matt - I was definitely not astir. Best, Don

[@saturn5tony]

Hi Don, I hope you and your family are doing well. I changed my utube name and may be getting back into radio again but for now still into space and such. (You may remember me as as ????) Very interesting situation they did with a humbucking coil and one we guitarists know too well. Les Paul used it way back In making coils for pickups in electric guitars and got rid of alot of lower noise issues as well. Always still have your awesome radio stuff utube link and watching it again. Be well.

[@RestoreOldRadios]

Tony, what was your old channel name; Storm....? Thanks for viewing I hope all is well on your end. Be safe and take care. Best, Don

[@saturn5tony]

@@RestoreOldRadios No it was ????. You sent me a cool schematic about a midland walkie talky I had as a kid. Radio is just so cool. See ya later buddy. I'll be watching more of your great vids and even look at most I have missed so far. Thanks for the quick reply.

[@carlitoyabes7368]

6😅😅😅 off p

[@RestoreOldRadios]

Thanks for watching. Best, Don