genek
-
Posts
2,679 -
Joined
Content Type
Profiles
Forums
Events
Posts posted by genek
-
-
Rock wool produced prior to 1980 is likely to contain asbestos. It shouldn't be an issue in a sealed cabinet, but if you're a tinkerer and may open it up again and again...
-
Forum glitched this morning. Hopefully, that was the only thing that got lost.
-
Nice work! One final tip that may help a bit with the last bit of blotching: tinted paste wax.
https://briwax.com/product/briwax-original-16oz/
There isn't a cherry tint, but red mahogany will probably go well with your finish.
-
For the AR-3a, the stuffing should be fluffed up and fill the cabinet right up to the front opening. The only space behind the woofer should be whatever is created by the magnet depressing the crepe or fabric barrier.
-
The 1950s was the era of "bigger is better." Maybe their marketing people didn't think there would be demand for smaller boxes?
-
For pigmented stains I prefer gel stains. I like the gels from General Finishes, but Minwax also makes them. To apply gel over dyed wood you first apply a light coat of sanding sealer or shellac to prevent the new stain from dissolving the dye. Wipe on/off, let dry. Then wipe on/off gel, let dry and apply final topcoat.
Here's a site with step-bystep and a video (this is for walnut, but the process is the same for any hardwood):
-
If you like the color the way it is, you might try another rub with reducer on whatever will be the bottom to see if you can further reduce the blotches. Because an oil finish is going to make them stand out more.
If these were mine, I'd probably want them darker (as I recall, original cherry ARs were fairly dark). I'd follow up the dye stain with a light application of pigmented stain to further level the light/dark areas. Instead of tung oil, I'd use varnish or a varnish/oil blend like Watco to get a gloss that looks closer to the lacquer originally used by AR.
-
You may still have some old finish in the grain in spots. Try rubbing it down with reducer (no stain) and see what happens.
-
Possibly Olson was unaware of the earlier Goodmans design when he originally filed and revised his patent to remove any resemblance to its title.
-
I found a working link to it. Look in the previous post up above. Olson as inventor, RCA as assignee. Wonder why RCA didn't make an effort to contest Vilchur's patent. Or if they used it in anything they made.
-
A great deal of design R&D consists of trying to accomplish what a patented design does without using the patented design. Many patents (possibly, most patents) are not for entire designs, but for some small difference added to prior art that makes the new design not merely a copy of the prior art.
And when authoring a patent, it is important to include a thorough description of the design and all of its potential applications, because while the people in the Patent Office who issue patents are required to have engineering or technical education and training, they are seldom specialists who can infer undocumented aspects or applications of new designs, and the judges who hand down rulings on patent disputes have even less technical knowledge. If Vilchur had properly researched prior art and had known about Olson's patent, it is conceivable that he might have successfully argued in his application that the use of a previously patented high compliance speaker to produce only low frequencies from large woofers in sealed cabinets as part of a multi-driver speaker system was a "nonobvious use of an existing product."
-
I can't help wondering if, having used Olson's patent to invalidate Villchur's, EV ended up paying royalties to Olson instead or if they then found some way to get out from under his patent as well
-
A definite possibility. Especially since, despite losing the legal credit Vilchur continued to be widely lauded as its inventer.
Do we know whether Olson ever made any money from his patent?
-
In a 2005 Stereophile interview, Vilchur maintained that he made the mistake of not hiring a patent expert to properly research prior art and that he could have defended his patent had he been better aware of previous filings.
"There was no general claim for a system that had a speaker mechanism with a free-air resonance frequency substantially below its optimum operating resonance, and which therefore required a small enclosure. That's what an acoustic-suspension system is"
https://www.stereophile.com/content/glorious-time-ars-edgar-villchur-and-roy-allison-villchur-part-2
-
That's pretty much it. Four little Peerless tweeters. Basically, simulating the horizontal spread of a dome tweeter with multiple cones. Was a fun little toy at $40 a pair off eBay 15-20 years ago. $300+ for a pair now is just flabbergasting.
-
I've always wondered what people played to blow those tweeters out. IIRC, Ken Kantor and Tom Tyson have both recounted similar experiences, and I've patched up a few for others over the years, but my own are still original parts.
-
Yeah, but that part was ignoring the fact that AR and KLH deliberately designed their speakers to roll off the way they did because they believed that truly "flat" treble response sounded bad in real listening spaces. Another reason why these didn't appeal to owners of the "high quality $280 speakers."
Perhaps ironically, 40-50 years later when the dome drivers are aging out, these little arrays have finally found their function. I have two pairs of them on top of my AR-3a's and 2ax's. I picked them up 20 years ago when you could snag them on eBay for $40 a pair. I had a third pair on my domeless AR-6's, where the added dispersion really sang, but those went with my retirement and downsizing.
-
The point of the Microstatic tweeter array was not more treble, but wider dispersion, as shown in this page from the MS brochure (the "high quality $250 speaker" that MS refers to is the AR-3a). But while the array did produce wider dispersion than dome tweeters when measured close in, at more practical listening distances most listeners' rooms produced enough of a reverberant field from domes to make the array rather superfluous. They were more of an enhancement for smaller speakers with only cone tweeters, but were priced too high to be attractive to most owners of those models.
-
What was new and different about Vilchur's invention was that he applied WDRC to multiple channels based on volume and frequency, with different levels set according to the patient's hearing tests, so that wearers got more amplification for sound levels and frequencies they had more difficulty hearing and less for levels and frequencies they didn't need as much help with. Prior to that, hearing aids applied the same level of amplification for all volume levels and frequencies and most patients either didn't get enough boost where they needed it or too much (sometimes painfully too much) where they didn't.
-
Who invented something is almost always defined, at least in popular memory, by who managed to get to a patent office first. Competing patent applications often win or lose based on subtle differences in how they describe similar tech. Prior to 1880, the US Patent Office required an actual working model be provided with all applications, and it was possible to build someone else's idea before they could and patent it, which is why you see a lot of old movies depicting characters working on "secret inventions" behind closed doors instead of the way things are done in real life today (file as soon as you think you can describe your idea and then begin development under "patent pending").
Edgar Villchur's biggest invention is arguably not a speaker at all, but the multichannel compression that is incorporated into almost every hearing aid in the world. When he developed it, instead of applying for a patent he published his work openly, putting it into the public domain. When asked about that, he would usually say it was too important a development in hearing research to limit and he didn't want to be involved in another patent boondoggle, but I wonder if he again didn't feel he needed the money that a patent might bring him and just wanted to ensure that this time he would be certain of getting the credit for his invention by publishing first.
-
IIRC, the difference between Villchur's sealed system and those earlier versions was that the prior art was done to reduce distortion at low frequencies while Villchur's intent was to extend those low frequencies to produce lower bass at low distortion from smaller cabinets, by making the woofer much much compliant. The prior versions were like some of today's subwoofers, which have sealed cabinets but are not acoustic suspension.
Villchur's later recollection about his patent was that he made the mistake of writing it without professional assistance and failed to include explanations of how his acoustic suspension differed from prior art that were clear enough for a lay person to understand, and as a result the patent was successfully challenged in the first round. He chose not to appeal because at the time AR was already doing well enough for him based on its revenues without outside licensing income and he thought he had better things to do with his time and energy.
-
Check eBay. Sellers there seem to come and go.
-
It does sound like rock wool, and I think I can see crumbly bits that you don't expect to find in fiberglass.
-
By the time the 4x came out in 1965 the era of rock wool should have been over. It was mostly used in the 50s and early 60s when fiberglass was in short supply.
Annoying resonance in more than 1 type of AR
in Acoustic Research
Posted
The first successful product liability suit for asbestos was 1971. So 50 years is just about right.
Asbestos is a naturally occurring mineral. If you're not specifically testing for it and taking steps to avoid it in your raw material, it can show up in just about any mineral-based product. So just about any mineral-based product manufactured prior to the 1970s may contain asbestos whether it was deliberately added or not. And its use was not limited to high heat applications (it used to be used in the backings of vinyl wallpaper and floor and ceiling tiles for sound deadening).
Also, "Rock Wool" was/is the name of a specific company and branded product, vs generic mineral wool. Although the mineral wool used in AR speakers is commonly referred to as "rock wool," we really don't know who made it.
BTW, the silica particles that are shedded by today's mineral wool and fiberglass products, though not carcinogenic, can still cause skin irritation if handled and respiratory damage if inhaled. It is always best to work with any such products outdoors, wear gloves and masks and put your clothes through a wash when done.