WMcD

Attached is the TRO entered in On Fire v. Fischer earlier this month. It deserves reading. I could rail on for hours about the righteousness of it. WMcD TRO - On Fire v. Fischer

Interesting. Would you kindly point me to the DfH, please. Also maybe you have the schematic for the decoder. It might be the one requiring furlongs of wire and a variable resistor. Perhaps there is more than one design. Smile

Devil in the White City is a must-read for any Chicagoan. It got me hooked on Larson.

Good to see you again Larry!

I took a look at the on-line Allied Electronics catalog from 1958. There are a few stereo tape machines. There are a few packages of a stereo pre-amp and two mono amps and just one stereo power amp as part of a package.. Two speakers areap included. No mention of stereo vinyl. I dont find any three channel equipment or applications mentioned. Of course what PWK used in any specific year must have been a work in progress. We see from the photo that he used different models in his array. It must have been part of an "add-on" theory. All this amplification was getting expensive. Maybe a third (center channel) could be extacted from a two channel amp. In early days he just connected the center speaker between the two hot (red) terminals of a stereo amp. Therefore the speaker was putting out Left minus Right. He published an article showing that the random.phases involved made this indistinguishable from Left plus Right. But that random phase situation changed with use of a microphone for the solo singer which made him a L plus Right signal. When put through the Left Minus Right system described, he would be eliminated. Engineers, later, must have mixed stereo so that the singer was solid center, meaning in Left minus right the system cancelled him out. His phase was not random. PWK apparently abandoned this Left minus Right and went with Left plus Right in the bridging system. This was accomplied by rewiring the output transformer of one side, say the Right one, to invert polarity. Therefore the bridge resulted in Left minus a minus Right. = Left plus Right. The Bell Lab system which he references used this. Probably people didn't like the idea of messing with their amps and the center channel minbox resistor system was advocated by him. WMcD

There is a lot being discussed here. The curves I ran says LMS because it is Loudspeaker Measurement System. We are measureing the electrical impedance (but call it resistance) at a wide range of frequencies as you can see on the x-axis of the graph. When we use a multimeter we are measuring the resistance at the frequency created by the battery in the multimeter. That is d.c. (so called direct current). The frequency is zero Hertz. It should match what appears on the left-most range of the graph if it could go down that far. It usually doesn't. It is an oversimplification to say resistance over a wide range of frequencies has nothing to do with resistance versus imepedance. However the graph has mostly to do with showing how resistance (err) varies with frequency while our multimeter is showing only zero Hertz. We can wade into the effect of horn loading verus a direct radiator speaker. Essentially we like looking at the input impedance of the driver in a box because it is easy to measure electrically. Very complicated but the system can be broken up into the electrial part (the magnet and voice coil, the mechanical part (mass and spring of the driver, and the acoustical part which is the air load on the driver daphragm (horn loading changes this per below). There is a model for all this. In a way, the electrical resistance as measured at the input terminals is affected by the mechanical and acoustic elements. So with some deep thinking we can look at the box's electrical input and figure a lot about the mechanical and acoustic properties. For example we can see the peak in elecrical resitance caused by the mechanical resonance of the drive -- but that is not what we're talking about here. A very simple model is as follows: terminal plus - - voice coil resistance - - - acoustic resistance - - and a ground return to terminal minus. In a direct radiator system we see: Input terminal plus - voice coil resistance (8 ohms) - - - acounstic resistance (0.8 homs) -- return to ground terminal That acoustic resistance is almost a dead short and like a piece of wire, it consumes no energy because there is little voltage drop across it. Most of the power just heats up the voice coil. The system resistance is 8.8 ohms. Note PWK's comments to the effect of "just heating up the voice coil." And the speaker is a space heater. In a horn loaded system we have termial plus - - voice coil resistanc (8 ohm) --- acoustic restance (8 ohms) - return to ground terminal. Here we see that system resistance is 16 ohms. You have to take a good look at this. We see that we no longer have the acousic resistance of near zero (wire-like) to a resistance which does absorb electrial power quite well (light bulb - like. Also this is why people say that horn loaded system electrical resistance doubles. Also, it is50% efficient because half the elecrical energy is disipated by the voice coil. It is true that the increase in acousic resistance is due to acousic impedance matching by the horn. I'm afraid to go into it here. This matching does not occur at d.c. measures by the mulitimeter, only at freqs where the horn is working to increase the acoustic resistance "seen" by the diaphragm of the driver. WMcD

You certainly don't need a "high quality system" to test them. Just connect speaker outputs of an amp to the screw terminals, being careful for shorting between the screws. Maybe you have what I call an old "dorm room" receiver. By no means should you paint them because it will ruin any resale value.

IIUC the masks are meant to keep your saliva from excaping and contaminating others. The submicroscopic virus can't be filtered by cloth. They certainly can't filter the virus in either direction. Therefore your mask protects others from your liquids getting out in the air. This just a matter that the virus rides around in liquids. Maybe thy will prevent you from inhaling droplets from other people's sneeze a bit but it seems to me the fluid just collects on the outside of the mask.

Heavy stuff but well worth watching.

A warm (below steam setting) clothes can be used to remove labels/stickers from cardboard boxes and envelopes. However most stickers with machine printed information are made of thermal paper and will turn black because of the heat. Therefore copy or photograph any needed info.

FWIW. You may recall the old trick for removing candle wax from a table cloth. Put down brown paper bag material and apply a clothes iron. WMcD

Please not gasoline. It is too flamable and you might not be able to get the smell out.

Wow. Rosewood is rare and expensive. I would keep everything as "stock" or "Klipsch" as possible -- save perhaps repairs. Bob Crites will replace the diaphragms. https://critesspeakers.com/electro-voice-ev-t-35-and-t.html The K-77 is rebranded K-77. K-77's come on the market very frequently. Watch out for ones with burnt out diaphragms. This occures because the tweeter is the most delicate of the three units. I would not open the housing for the woofer unless you know you have to replace it. When test listening make sure to do left and right, one at a time. Balance control will do this if you have one. I got fooled once.

sIf you go up to your original post, look for edit, then you can edit the title. But only the original author can do this. Using the Klipsch system here you can only put one photo in a post. I encourage everyone to reduce the file size of photos by using MS Paint. Reduce so the photo fills that screen. Usually this can be by a factor of 4 depending on setting on your cell phone or camera. WMcD

Part of the problem might be that the separates crowd ran down receivers so persistently that the receiver manufacturers had to call them something else. It is intresting that there are few receivers in stock and you attach an inference that they are not popular. Heck, TP is not in stock. WMcD

Long ago I made a set of very similar horns. Working with wood for most of the unit is workable but I didn't find a way of threading wood to take the driver. OTOH bringing the throat down to a 1.0 inch (or so) diameter is not a problem and I used a plywood disk about 3 inch diameter with a 1.0 inch hole glued and screwed on the end. The the adapter can be bolted to it. Very hand for any design using that type of screw-on driver. It is necessary to design for the bolt heads of course. The link for this version is in my earlier post. WMcD

https://www.parts-express.com/eminence-s2b-a-aluminum-1-3-8-18-tpi-screw-on-to-2-3-bolt-horn-adapter--290-561 There are other versions from other manufacturers. Nice work on the wooden K-400 varient. WMcD

What song uses thruppence and sixpence. (Vaguely related to bread crumbs being sold for tuppence a bag.)

The River Mersey is the river through Liverpool. Mome of the fab four. You'd thumb down a Diesel, wouldn't you.

My parents had an old player for 78s and then later a simple player of 33 rpm LPs for Christmas. Along with it was an LP, How to Conduct Your Own Orchestra (baton included). It contained catchy tunes from classical music. I might have been six years old. I'm with dtel in spirit. AM in the NYC area was very much WABC and top 40. Then FM started up. It was sea change with for rock, intelligent DJs and a thoughtful selection of Album Oriented Rock (AOR). WNEW was tops. Their most fabulous DJ was The Nightbird. This was the mid-1960s. .https://en.wikipedia.org/wiki/Alison_Steele I don't recall any other female DJ and she would be a tough act to compete with. The wiki is worth reading. Classical on FM in stereo was also a big hit. I recall an honorary uncle of mine trying to convince his wife he needed an outboard FM decoder. In vintage mono FM receivers you'll often find a MPX output for multiplex stereo.

Often the wedges are made of metal screening which is acoustically transparent and stuffed with fiberglass insulation which is absorptive. The wedge shap prevents the creation of standing waves at any one frequency and inceases the effective surface area. There is no reason for anyone to be inside during a test because a body could affect the meaurement. The possibility of hearing damage should be a concern, always.

With a grain of salt? Of course. None the less I believe this enthusiastic review reflects a very extensive redesign of the crossovers by Roy based on science and perception. Let me point out.I First time hearing a K-Horn. As said elsewhere, almost a religious experience. The Forte I with a passive got excellent reviews. The tractrix. History shows that Klipsch liked it so much it was put into the Forte II, Cornwall II, and Quartet. Yup, my Forte II had something grand. I had go sell them but the Quartets have much of it. My point is that some designs and re-desgns are worthy of gushing about and reviews are justified.. WMcD WMcD

This should get you there. http://www.itishifi.com/2009/03/plexiglass-klipschorn-and-pwk.html I'm guessing that was taken at the museum. WMcD

We should find the photograph of PWK standing next to the plexiglas K-Horn. He is wearing socks with sandals. I guess it is okay if you're the boss . . . and in Arkansas. WMcD

Fred Flintstone feet? I love it. That must be my problem. I have only three toes! WMcD