Pete B

I made the mistake of starting a thread at Parts Express Tech Talk giving credit to Villchur: "Ed Villchur's Acoustic Suspension Invention" https://techtalk.parts-express.com/forum/tech-talk-forum/65475-ed-villchur-s-acoustic-suspension-invention Then after actually looking up Olson's patent, made this correction: Correction: I called this "Ed Villchur's Acoustic Suspension Invention" and I've known for many years that Villchur's patent didn't hold up in court with the reason that I read on the internet being that Olson had previously patented the closed box speaker. I thought logically, why would Villchur bother if there were no differences, that Olson's was sealed but that the air was not the dominant compliance. I just read that his 1949 patent title was "Air Suspension Loudspeaker" #2,490,466, clearly the air spring is part of Olson's patent. This is from the patent: ----------------------------------------------- An object of the invention is to increase the power handling capacity of a small speaker, making *it comparable to one substantially larger in size in its output of undistorted acoustic energy and fidelity reproduction of desired low as well as high frequency sound waves. Another and more specific object of the invention is to provide an improved diaphragm suspension structure in a loudspeaker characterized by a reduction in the effect of the suspension impedance, thus lowering the natural resonant frequency of the speaker of a given size, without increasing the mass reactance of the moving parts. A further object of the invention is to provide an improved compliant suspension in a limited space for a piston-type*loud speaker diaphragm of small mass reactance whereby the diaphragm is free to vibrate at large amplitude over a substantially extended portion of the lower audio frequency range without amplitude distortion. A still further object of the invention is to improve the low frequency response of loudspeakers mounted in small housings as in small radio receivers. ----------------------------------------------- It seems that this patent clearly covers everything that Villchur claimed in his work done about 10 years later. It is odd that Olson's patent is written to cover small radios, this makes no sense since all the theory applies to larger speakers. Why didn't they design and market bookshelf speakers? Villchur applied it to bookshelf systems and essentially changed the world but I have to say, IMO, that he did not invent the concept. He certainly popularized "small" high performance loudspeakers. I do enjoy the history, but I'm not a historian so I'm not going to go into it in anymore detail, or dig any deeper. I welcome well researched additions to the history.

I wonder how this Visaton paper cone tweeter with a smooth response would do as a replacement, with a parallel resistor to match the impedance: https://www.mouser.com/ProductDetail/Visaton/TW-70-8-Ohm?qs=VWNNG7jHlrLkQoY0VZlmUA%3D%3D Mounting would have to be worked out, perhaps 3D printed.

Next year this thread will be 20 years old, time flies!

As the title says don't want to ship but will try to figure something out if further. Anyone? Don't mind doing a few or more repairs.

I have a pair of LA woofers here that were refoamed by Bill LeGall of Millersound about 6 months ago and there's no sign of the dust caps being removed.

If you found an 8 ohm SA woofer I'd say that it was probably worked on with a VC replacement or they mixed up some LA woofer voice coils in with the SA ones. It is in the "engineering" sales literature that while they SA maintains the same F3 as the LA they lowered the impedance to 4 ohms in order to keep the system voltage sensitivity as close to the LA as possible. However, even the LA is lower than 8 ohms with the DCR usually measuring under 5 ohms. When I worked on a few SA woofers I was surprised how similar, if not the same the magnet pole piece, VC were to the LA, probably a parts commonality thing for mass production. I repair two SA woofers here with some notes: https://audiokarma.org/forums/index.php?threads/small-advent-woofer-repair-some-measurements.819443/ I measured a DCR of 3.3 ohms for the SA woofer.

They look like Advent Legacy woofers with very large replacement dust caps.

I discuss a bit more about the presentation in this thread: https://audiokarma.org/forums/index.php?threads/presentation-at-frankenfest-4-1-2023-why-waveguide-speakers.1026720/#post-16319058 I measured the LA Econowave here and found a few serious issues that are corrected in the PB1 modded version that I'll be demoing: https://www.audiokarma.org/forums/index.php?threads/measuring-the-jackgiff-bauhausler-jb-large-advent-la-econowave-2022.1006729/

Giving my presentation "Why Waveguide Speakers?" and demo of the Large Advent Econowaves at the 2023 Spring Blue Mt. Audio fest. Peekskill, NY Tomorrow Saturday May 6, Doors open at 10 AM presentation at 1 PM or so, playing it by ear, very informal. $20 fee, also audio gear swap meet. Blue Mountain Park, Welcher Ave. Peekskill NY https://audiokarma.org/forums/index.php?threads/%E2%99%AB%E2%99%AB-saturday-may-6th-2023-spring-blue-mt-audio-fest-peekskill-ny-%E2%99%AB%E2%99%AB.1025956/

I use a 10 ohm resistor so it is about half the voltage at the speaker. One thing I should have mentioned is that the rubber edge could have hardened, though mine looked fine. It depends on the type of rubber and I have many woofers with rubber edges that have Fs now that is 2X what it should be. Wintergreen oil is talked about a lot on the Web and Youtube and it works great for a day or 3 let's say. Doesn't take long for them to be back to 2X. I will probably try brake fluid next time being careful not to get it on the glue.

I was given some very beat up large Advents, did some repairs and did a lot of sanding thinking I'd just apply a new finish. I found the same thing, that sanding, even the first layer produced a lot of colored dust. What I found was that the front trim was not even close to the rest of the cabinet. And the cabinet had large color variations. It seemed to me like there was a tinted clear coat and after doing some research I found that this was common since the 1940s to even out the color and I'm quite sure that it is what Advent did. I think that AR's used a better quality wood and perhaps this wasn't needed but it is something to keep in mind. Certainly, if the owners manual says it is finished with BLO and that's what to use to freshen it up, then that's what you should do. Please keep us up to date since It might help with my effort. These were almost ready for the dumpster so I consider it a learning experience. I'm considering trying a black dye/stain just to get the job done.

Great that you already rebuilt them! Yes I'd add the shunt cap but no rush. Hope you enjoy them very much.

Your tweeter impedance certainly looks to be 4 ohms. That is of each series-parallel array? If they all work, I would just use them and listen for distortion in case any of them have problems. Perhaps they were already rebuilt with 4 ohm coils? Both arrays have an impedance peak around 4KHz which is very high and makes them super tweeters. Most of those tweeters that I've measured, perhaps were worn out, did not show much of a peak at all. I don't know what the correct impedance peak frequency is for those tweeters. As far as caps go, I would replace the tweeter and mid caps as soon as possible. I prefer film caps because I don't like to have to change them every 10-20 years. I'd probably replace the cap across the woofer with an NPE. The large input cap I'd check for leakage and it might be okay, otherwise you might want to replace them with new. See how they measure for leakage and how they sound.