The steps I took to rebuild the speaker for the Philco 41-280. I still need to make/install a Dust Cap and finish up on the electrical restoration. Thanks for taking time to watch.
What an excellent roadmap and tutorial for those who might attempt this process or parts thereof! Thanks for the details you shared on re-establishing/maintaining concentricity on reassembly.
+Scott Taylor I appreciate it Scott. Like you stated, most times the speaker just does what's it's suppose to do and we never give it any thought. Thanks again and I appreciate you watching as well. Best, Don
Thanks to you and how you explain the use of different chemicals,and different things for my small work bench ,like the liquid tape which I just got ,I plan on buying a couple things I can afford every month,since I am on a fixed income,your Ideas help .me to do better work.thanks.again.
@@RestoreOldRadios I understand ,but what I learn from you ,you need what you need sometimes ,to do a good job ,and your work is just amazing ,well done you take your time to do it right ,you do have a lot of loyal fans ,I am glad to be one of them teacher. I think you improve us.thanks.And I agree you are frugal .
+Bobby Tectalabyss Thank you Bobby. I used up a lot of brain cells on this one, but the preparation, planning and hours led to a successful outcome. Best, Don
Don, You did an amazing job! That is a brand new speaker, made from scratch. I don't think the factory, cranking them out by the thousands, could have done a better job. Regards, Tom
+THOMMGB Thank you Tom. I learned a lot and will make some minor changes on the next one if there's a next one. I was excited when I plugged it in for the first time. Again, thank you so much for your positive words. Best, Don
There are times when the written word pales in comparison to that which is spoken; this is one of those instances, so here goes... MAN, IS THAT NICE!!! You essentially built a speaker from 'the frame up', not an easy task, and one which is rarely accomplished - these days. E.V. Game could not have done better, and they invented the technology of "humbucking". One of my **former co-workers at Boeing is an avid 'sound reproduction hobbyist', and has an affinity for Bogen sound reproduction equipment. He created an inductive pickup set (both channels) for one of his many HP and Fluke oscilloscopes, and developed a method for evaluating the condition and frequency response in guitar amp speakers. ** I'll look his email address up, then forward a link to this video to him.
+AMStationEngineer Thank you so much Tim, I really appreciate it. I was nervous using the voice coil I built due to the Eddy current issue that was raised; so far so good, but my ears are not the best. I will definitely make that design change on the next one I build, assuming the opportunity presents itself. Thanks again for passing this along and again your kind words. Best, Don
Hi Don, Excellent job ol’ son! Many years ago, I was led to understand one of the chief reasons pre-1970s general type speakers (especially pre-1940s e m speakers) do not sound as good as modern speakers boils down to the difference in the angle of cone pitch (modern cone angle is more obtuse, therefore less tight, and better swing???), quality of paper, and use of synthetic rubber materials for outer cone hinges??? …perhaps so …though I do have a few reservations about this. Off and on over the past four months, I have been attempting to rebuild a p m speaker from of a Bush, model AC11 (1949) radio. Having stripped it completely, I’ve de-rusted the basket; completely reconstructed a cone out of card (as far as I’m aware, speaker re-cone kits are no longer available here in England); reconstructed a voice coil bobbin, and rewound 38SWG e c wire around it, made outer gaskets out of from 3-5mm thick felt …in other words I’ve done most of what you’ve done. At present, I’m giving lots of thought how to construct a press device for pressing the required folded ribs for the rear cone centring hinge, and also pressing the folded ribs required for the top outer cone hinge. Wish me luck in this little venture. Any ideas would be welcome. Thanks, Phil.
+SteelCity321PB Thank you Phil. That speaker from the Bush, AC11 sounds like a challenge too, but one that's worth the effort. I would love to see some photos of your work to this point and more on the folded ribs. I'll send you a PM with my email so you can forward a few photos if you don't mind. Thanks again for watching, sharing your knowledge and experiences. Best, Don
Hi Don: Nice job. I can't argue with success, but I'm surprised that the speaker works as well as it does. I think it would have been better to used steel instead of aluminum for the mounting base of the field coil. The field coil generates the magnetic flux in the air gap for the voice coil to push against. To get the strongest flux from the ampere-turns of the field coil, it is best to use high permeability materials to direct and concentrate the magnetic field. I think it would be interesting to repeat the speaker test you did earlier by comparing the volume with and without energizing the field coil.
+Steve Muenter Steve, that makes sense and thanks for your input. I can repeat the test, but should I hear anything from the speaker without having the Field Coil energized since there's no magnetic field? Thanks again. Best, Don
Even without the field coil energized, there is probably a small residual magnetic field due to the magnetic remanence of the iron pieces. If you hooked the field coil up to your variac and applied an AC current, you could probably demagnetize iron in the field coil assembly by slowly bringing the voltage up, then back down to zero. (Energized with DC, it's a field coil; with AC, it's a degaussing coil.) After degaussing, I'm pretty sure the speaker will be silent if you apply a signal to the voice coil while the field coil is de-energized.
+Steve Muenter Hi Steve, I used my DATS 2 and you're spot on. The Qes doesn't even register (reads 0) with 70 milliamps of current flowing through the Field Coil. Thank you again for sharing your knowledge. I'll be sure to incorporate your recommendations when the next rebuild is needed. Best, Don
I agree that it's extremely important to use iron/steel for that part. It plays a critical part in concentrating the magnetic field in the gap where the voice coil lives. With aluminum there, the mag field is spread out and weaker where the voice coil is. I would expect this to result in much less volume. I believe it still needs the field winding to be energized, however. Without that, there should be almost no field in there. Any residual field will be minimal, especially with that alum plate. Was there a problem with the original plate? BTW, where do you buy the speaker parts that you use, like the spider and cones?
Great job & results. If you get into another one sometime, I do have a small bench top "arm strong" press from Harbor Freight you are welcome to borrow.
+Albert Morris Thank you Al, I'll keep that in mind and appreciate the offer. Hope all is well with you and thanks again for watching and your positive words. Best, Don
Steel should have been used instead of aluminum. And the hole had to match the voice coil to get a tight gap to focusing the magnetic field. Speaker efficiency is greatly reduced. However - I like these videos. 😉
Angel - it’s just a hobby for me as time permits. You could try The Speaker Exchange at: reconingspeakers.com/faq/reconing-faqs/ They should be able to provide direction. All the best. Don
polkiju7 Don’t underestimate your abilities. I have no formal training in this area, just a lot of reading and tearing into one and seeing if I can/could get it back together. I would vote you give it a try. All the best. Don
Sorry, I don't recall the exact number of turns for the field coil. I always base my calculations on the AWG magnet wire nominal DC resistance per foot and back into the required footage based on the field coil DC resistance requirements. Hope this helps. Best, Don
I have to disagree that modern permanent magnet speakers sound better. The field coil makes the voice coil's job much easier, and the sound has a nice "grip" you don't get from most PM speakers.
+Martin Tousignant Hi Martin - like you, I appreciate the sound from a healthy electromagnetic speaker. I was comparing my rebuild to a modern day speaker as I'm not sure it's on par with the factory production units back in the day, but I'm extremely pleased with the outcome so far. Thanks again for watching and sharing your experience. Best, Don
