Today is it global Solar Water Heater day?

Loudness, Its Definition, Measurment, and Calculation - Harvey Fletcher and W.A.Munson, Bell TelephoneLlaboratories - JASA October 1933

At your risk. The amazing paper publised nearly 100 years ago showing that loudness does not depend only on intensity but frequency, waveform, psychological state of listener etc. my humble observation while reading this paper is that while +70dB intensity compared to threshold at 1KHz can still not be heard by a human it may have dramatic psychological effect to a human being if coming say from machinery in the same building (structure born sound) for prolonged periods, (for example in the house you live in, try to sleep etc). After all sub or very low frequency audio is used in thriller movies. So local authaurities must take into account, a law on moise protection should take all these into account. If there is not data available then research is needed.

Creating baffle speaker as solar panel to drive the amplifier

At your risk. For example the solar panel serving as a speaker baffle at the same time, which a suitable hole to mount the speaker.

On creating a great sounding speaker with the Fostex FE-127E fullrange speaker or other good quality fullrange speakers or a good quality woofer, tweeter combination

At your risk. See next posts.

Creating speaker baffle from cardboards glued together to increase thickness

At your risk. A 4mm baffle was created by glueing 2 layers of 2mm by PVA water soluble glue. Size of panel is 50cm by 70cm. Promissing sound. More thickness, say 3 ply increases bass as a thicker matterial insulates more the bass. But for some reason 4 ply sounded a bit bass heavy on particular 50cm by 70cm baffle and speaker. Bass and treble response should be balanced on any speaker as we know from Olson's RCA research on the influence on bandwidth to a natural sound. For example if a speaker reproduces from 100Hz up it will sound shriil if it goes up to 20kHz. After all 40Hz is ones octave above 20Hz, 10KHz is one octave below 20kHz. Currentlty on Pleiades lab comparisons are done by ear-brain speaker vs reference Sennheiser hd-580 headphones at same loudness. There was not much bass with Tesla 5in speaker although the mid quality was good. There was some bass with the Fostex speaker. there was much more beautifull and deep bass with the Grundig 5"x10'fullrange speaker. Mid high heaviness was reduced by adding a sereis inductor of 1.7mH see next posts. How would baffles created from 2 or 3 linoleum boards glued together would sound like? How would a say Puioneer CS-353 size box made from such thickness linoleum panels sound like with the great Fostex 4.5'FE-127E connected in series with a 1.7mH inductor and 40 ohms in parallel with such inductorm (see next posts) sound like? The idea is to use the sound absorption (damping) properties of linoleum while creating something colored and beautiful. 45 degrees panels may be cut very carefully with the Olfa 45 degrees cutter, not tried yet.

The Zeis Ikon typ:31-06 51cm by 51cm baffle full range 7" cabin speaker sounds great with a 1.07mH to 1.7mH inductor in series

At your risk. Mid high heaviness is gone. A high say 47ohms or greater resistor can be connected in parallel with said inductor if some increase of high frequency response is needed. Promising results.

On calibrating home made speakers by ear using SennheiserHD-580 open back headphones as reference

At your risk. This is how it is currently done on Pleiades lab. In real time under real room listening environment. A good CD such as Guilty - Steisand, Gibb is on Sony CD Walkman. Its line out is connected to class A Pleides 2N3053 power amplifier feeding speaker to be acousticaly calibrated. Phones out is connected to excellent neutral Sennheiser HD580 headphones. Volume is adjusted so that headphones, or speaker sounds equally loud so that the listener's brain is on the same equal loudness curve (Fletcher-Munson curves). Say a Philips 8in woofer is placd on a 21cm by 29cm by 48cm Pioneer CS-353 box (actually this box may be small). If it is directly connected to amplifier it sounds mid and midhigh heavy. If a 1.07mH inductor is placed in series the midhigh heaviness is gone and the bass can now be clear. Say then a paper cone tweeter is connected by a series 2.2uF capacitor. We get the treble but it sounds a bit strange. Pressing pause on CD Walkmann, the power is disconected from power amp and the headphones are worn. Now Barbara Streisand voice sounds much more warm with less high frequency heaviness on the song A Woman in Love. Goinjg back to speaker mode, a variable series resistor is connected in series with capacitor and tweeter to control amount of high frequency content until Barbara sounds as equal as possible to Barbara on the reference headphones HD-580. When her voice sounds right the resistance can be measured to be say 20 ohms in this particular case. By still comparing speaker and headphones in turn it is found that there is still a mid high heaviness. Capacitor is now changed to 0.5uf which makes sencs as the high series resistance increases the time constant which is RC ie resistance times capacitance. Now it sound much closer to reference headphones and there is a smile in your face as you look at the blue sky. But there is still some midbass heaviness. It is decided to increase the woofer series connecetd inductance by inserting a screwdriver inside the bobbin core of said inductor. Now it sounds almost perfect and you laugh. The inductor is later measured on an impedance bridge to be 1.7mH. Same tactic can be used to remove midhigh heaviness from fullrange speakers, the capacitor usually is not needed but the inductor and a resistor in parallel with it is needed, see next post. So the most expensive apparatous is used to full advantage, your ears and your brain.

On placing fullrange baffle or non baffle (even closed box) spakers to the place they trully deserve

At your risk. They sound amazing due to their point source coherence etc but usually there is an annoying mid high heaviness that can hurt. So this is an option. Adding an say 1.7mH inductor in series to cut mid, midhigh heaviness, ie treeting it like a woofer. Then to restore high frequencies a resitor of say 29ohms is placed in parallel with said inductor. the resistor can be variable until one gets it right. Results are promising. These are values used with the great Fostex FE-127E 4.5ii fullrange placed on a Pioneer cs-353 box. Unboomy deep articulate bass, natural mid, sweet highs. It works nicely with other great full range speakers such as a 5ii by 10ii Grundig on baffle etc. Tried also sussesfully with a Staren 5ii fullrange and a Bayma 8ii fullrange. If a woofer such as a Philips 8in is used it may be preferable to uise a small say 1uF capacitor instead of said resistor in order to enchance high frequency response, ie treat the speaker as both a woofer and a tweeter!, see a previous post on speakers with or without baffle.

Is the Pleiades linoleum Auratone type C a failure?

At your risk. Possibly. It turns out the Tesla fullrage speaker used has very little bass, ie high reasonant frequency. But it can be greatly improved by adding in series an inductance of 24mH to remove mid, mid high heaviness, and say 50ohms in parallel with said inductance in order to remove resultant prominance in bass ie add back the sparcle. Fed by the Pleiades 2n3053 class A amplifier when at a high volume setting the non linear distortion on voices, Barbara Streisamd, Bary Gibb is very interesting, on the song What Kind of Fool.

Unexpected nice distortion on Pleiades 2 K117 microphone preamplifier by chance

At your risk! While fine tuning the second stage... The coupling capacitor from 1st amplifying stage was disconnected to 2nd stage and music from the Sony Cd walkman was connected to potentiometer feeding second stage on the small made in Taiwan breadboar At a point Vb 9V batterysupply was disconnected from output transformer and was connected by mistake to one rail below feeding only the onlder version drain resisator of 22Kohms. surprisingly music could be heared on headphones connected to output transformer with a very interesting distortion on Barbara Streisand vocals. And no matter how loud distortion did not become ugly. By observing carefully the schematic the output transformer is still connected to the drain of output stage but its other side is connected to the upper side of the 1rst stage drain resistor. So effectively this other side of the transformer is connected to ground through the whole 1st JFEt stage. It worked only with high values of 2nd stage source resistor, say 3.8Kohms.

Updates on the Pleiades 2 K117 (2 jfet only) no feedback low noise microphone preamplifier with balanced input and output, 9 volt battery supply

At your risk. It can directly drive 300 ohm Sennheiser headphones by being fed with a shure SM58 microphone from a soft singing voice 24in from microphone. The schematic is as simple as it may get, input transformer, K117 resistance capacitance coupled stage in class A, attenuating potentiometer, K117 transformer coupled output stage! The gain is dramaticaly inscreased by changing the second stage source (bias( resistor to 420 ohms thereby increasing output stage power. 2 tiny (input and output) transformers are used which have a low inductance typicaly 100mH to 4H to cut bass heaviness to listener brain when a flat mic is used in order to compensated for equal loudness curves, voice effort curves. In detail component values, schematic: Mic input transformer: Thordarson MIT 209. 68nF coupling capacitor to gate. !Mohm gate resistor to ground. K117 JFEt. 100Kohm drain resistor (electron tube similarity for high gain , small device current can give very low noise). 10Kohm source bias resistor in parallel with 47uF/35V electrolytic capacitor. 470nF coupling capacitor from drain to 220Kohm log potentiometer. Other side of pot to ground, tap of pot to 2nd k117 JFET gate. 1 Mohm resistor from gate to ground. 420ohm resistor from source to ground for self bias, in parallel with 47uF/35V electrolytic capacitor. UTC DO-T9 output capacitor directly connected to drain as on class A single ended power amplifiers. That's all folks! It is intended to be placed insisde a beautiful looking beige-brown Retex made in Spain console box with a bulgin 9 volt battery holder.

amazing biography of inventor Edisson

At your risk. It is like watching a movie, thrilling, why not a movie? The book is Thomas Alba Edisson - Glenwood Clark Edisson attended only 3 months of school as the teacher and inspector insulted him, so he was taught at home by his mother who was a teacher. His father would give him 25c for every book he read. Edisson tought himself, started doing experiments many times until he was convinced that a theory is good or not! For his inventions he worked very hard doing so many experiments until he got it as he wished.