Toys, trampolines and video games can only get you so far when you take your kids to an audio event. At some point you need to put the kids down for a few hours and deal with the results at a later date. I think I found the perfect service.
It was time to leave so I needed to collect the kids.
Note to self.... don't freeze your kids since they start talking in audiophile terms
. It always feels good to get something finished and shipped - good to get it to the new listener and good to be able to move on to the next project. It is also very motivating. There is something about sinking those screws into that crate. It is closing a chapter... time to reflect on what you learned...
I know I am always posting about mercury... sorry... the stuff sounds great, but it is not easy to deal with... there is that whole toxicity issue... and then there is also a very high percentage of them that are just DOA or bad..... so how do you tell when mercury is going bad? well, the easy and practical method is color... blue is yummy good... purple is bad - headed toward death...
the one on the left is bad.... time to remove from service.... but the one on the right is pretty blue... it should be good for thousands and thousands of hours...
Stories abound in the audio world and in life about the "old dead guys" that have set our destiny. Lately it seems that loss leaders have replaced lost leaders and the rest of us just sit back and consume liters of our favorite drink and brag.
A friend from a former life initially pointed me to Glen and his works by dropping a $1 goldberg variations in my lap and I found I could play them all day without tiring of the music.
Props to Kuma on the asylum for pointing me to this video and teaching me a life lesson.
In the course of working with lowthers you occasionally come across a bad seed or a unit that requires you to "smack it around" to get it in line. The net result of this treatment isn't always pretty but once you get the driver in the right mind, recovery is possible. The following is a result of just such a case. Let me provide you with before and after pictures to start off this success story.
The process was actually very simple, I simply turned a slightly tapered reformer out of an appropriately sized PVC coupling. The taper is about 1mm over the 50mm length with the target diameter coming at about 20mm. I was actually surprised how nicely the PVC turned and all three of the ones I bought to play with are 100% functional.
The ultimate finish may not be 100% but the function is there. In the above referenced coil I was able to recenter it and move it without any rub. The real test sample was a 5" basket that took a rather hard hit to the coil and was impossible to center. It was only mildly eccentric and had a distinct kink where the slit in the former was. 30 seconds in Dave's Reform School for Lowthers and another 30 seconds on a magnet had it centered and passing signals without rubbing.
The lathe is still set up and it only takes a few minutes to turn these so if any of you out there use lowthers and find yourselves in need of such a device, chime in and I'll send you one.
I just wanted to say thank you and rest in peace to Owsley... Nope, I did not make it to Watkins Glen in '73, (I was a few months old), much less Longshoreman's Hall in '66, but I know my life would not be the same were it not for Owsley...
Wolfe's book on Kesey's tests is great... and Owsley's work is documented in there... his lab work as well as the way he sculpted sound by yanking "all of that old stuff" from local theatres... Altec multi-cells and big bass horns... can you imagine lugging that stuff around?
and then there is the wall of sound... hundreds of JBL drivers... 26,000 watts of MacIntosh power.. even some tube amps for the treble...
I know I owe him for many evenings of enveloping sound in my formative years.. thanks, man! RIP!
Much has been said lately about the difference between low voltage and high voltage field coils. The first Lowther prototypes were done at 200V for the sole purpose of the cool glow of mercury in the supply. Alas I never got around to building a proper mercury supply for them before the revisions and subsequent production which ruled out the possibility of the HV supply for safety reasons. We did get to do the mercury LV supply though.
The question of low voltage high current vs. high voltage low current is a tough one to investigate in an apples to apple way but the first step was to rework a pair with 4 identical windings which can be placed in series or parallel to compare 15V @ 2A to 60V @ 0.5A. To get the wire to do the four parallel runs I needed to de-spool 4 rolls from a 100 pound roll of wire. I did all of the calculations and added 10% even though things were getting me a bit nervous at the end, It all worked out.
Here they are all buttoned up and ready to go to the test subjects who will do the comparisons with 8" baskets in160hz front horns and with 5" baskets in a pair of full range back loaded horns. Along with the field coil, we are also sending a pair of alnico and Neo 5" drivers so we can get the report on those differences too.
Ijaz called me the other day and said he stumbled across a pair of Sequerra T9's. Being unfamiliar with that designation I took to google and didn't find out much so it was time for a trip to Dick's to have a chat.
The most interesting thing about this design is that it is a dipole in a sense because it has two ribbons in series, one firing forward and the other backwards.
Of course they need new ribbons but that isn't an issue since they can easily be replaced. Below are a few other shots for google to find so there is at least a bit of info on these tweeters out there for people to find.
Now why is Dave suddenly interested in ribbons? I'm not really, but I am interested in magnets and given a little coaxing I tend to take on some crazy projects just to see what happens. In the case of ribbons, the magnet of choice seems to be neodymium. I'll be honest and say that in my limited direct comparisons, I do not like the characteristic sound of Neo magnets. Dick chose ceramic out of the scale of economy and would have much preferred to use alnico5. Now he is excited about the possibilities of what he thinks may be the best magnet type of all. Time will tell where this project goes so stay tuned.
For years now I have tried to explain (preach? scream?) that tube amplifiers do not have "slow" or "flabby" bass. This common misconception originated when solid state amplifiers came onto the market and the speakers boxes began to be tuned to the lower output impedance of the new amplifiers. If a box is optimally tuned for a solid state amplifier's one ohm source impedance, then it will be severely under-damped (woolly, slow, flabby, etc) with a zero feedback tube amp of a few ohms output impedance.
But what happens in the upper regions? Do compression drivers need to be driven from an optimum source impedance or is lower always better? After all, lower output impedance means a higher damping factor. We have all been told that damping factor must be as high as possible. Well, I am saying that just is not true... please prove me wrong! I was measuring anyway, so I took these plots:
Impedance plot of a JBL 2435 on LC600 horn:
I know that the mighty Bell Labs actually specified a driving impedance for their Fletcher system. It basically was the root mean square of the peak and valley of the impedance plot. They published that this driving impedance was required to meet their frequency response specification. We do not quite meet that formula here, but look at the difference in the region from 1kc to 2kc when the driver is driven directly, through a four ohm resistor, and through a twenty ohm resistor.... and this region from 1kc to 2kc is precisely where the speaker impedance peaks, dips, peaks... driving impedance will change frequency response.. that we already knew...
Frequency response plot of JBL 2435 on LC600 horn - ignore everything above 10kHz, new computer and mic calibration has not been corrected.. sorry...
This is a tight zoom on an impulse response of the JBL2435 driven directly from a solid state amp, through a four ohm resistor, and through a 20 ohm resistor... I did not move the speaker for any of these tests... just clipped in a resistor on the amplifier end...
oh... I know... I should run a square wave through there... I wonder if my measurement gear is up to it... stay tuned!
The first comes from a friend of mine.. Her father was a tinkerer and saved lots of random electronic things and I inherited them. Some were quite useful electronic tools and such, but others had no story with them. So here is mystery number one:
three bobbins.. common core.. one section meant to be rectified and filtered...
and this 127969AU number corresponds to??
last week my PC comes up with this:
nope, that is not my real desktop.... and, nope, I do not have any such program called "System Tool" on my computer. I knew enough to not click anywhere in the box, but even the Task Manager would not start... so I shut it down... After googling "System Tool virus" on an *Apple* computer, I found out it was definitely malware and that I could just delete the file after booting in safe mode. So the mystery here is just "Why do I even still have a PC??" and "Why does all of my simulation software run on PC's only?".... and finally, "Why do I pay McAfee??"....
and the final mystery for today:
how does one get a low frequency rumble on a simple LC power supply that is resistor loaded? this baby should be pure 120Hz.... I think I am about to learn something...
Picked up a few of these off the 'bay last week and lets look a bit closer to see what was going on. As I unpacked them I came upon my biggest peeve and that is the combined use of bubble wrap and packing tape. If you must use tape to secure bubble wrap a very small well placed piece will serve the purpose, there is absolutely no need to cover every square inch of bubble with packing tape to prevent accidental unwrapping during shipping.
Upon unwrapping the first tube and nearly slicing my finger off with an exacto blade I came upon this disturbing sight.
Next I tried scissors and the result was similar.
Brute force opened the next three and gave me this. Nice clean getter huh?
Finally upon opening the last one I was greeted with hope.
Now that is how it is supposed to look. Too bad the effen filament is open.