Arkytype

Then there's the Keepers Of Odd Knowledge Society. Lee

If I had two identical amps, one with an input sensativity of 1V and the other with 2.5V then the 1V might be a high gain and the other one a low gain? If no, then what am I missing? Strictly speaking, if both amplifiers have the same rated output power (at a rated distortion level), they both have the same "gain". So, what's the difference? Well, if you own a Klipsch loudspeaker, for a given average listening level, you may find the "noise floor" is more audible with the amplifier having a sensitivity rating of 1 volt than with the other amplifier. Why? It has to do with the noise floor or the signal-to-noise ratio (S/N) of a piece of audio gear. Power amplifier S/Ns are typically specified at rated output power, not at typical listening levels. Let's say both of the above amplifiers are rated at 50 watts continuous average sine wave power at 0.05% THD+N. Notice the "N" term--that's an abbreviation for noise which is usually the noise floor of the power amplifier's circuitry. We'll also stipulate that each amplifier's hum and noise are 85 dB below the rated output power of 50 watts. Since noise figures are usually A-weighted to better correlate with human hearing, we'll rate both amplifier's signal-to-noise ratios (at rated output) at 95 dBA. If your average listening level is at 1/2 watt, the S/N drops to 75dBA. Here's the math: dBA = 10*log (50/.5) = 20 dBA Subtracting 20 dBA from the original S/N of 95 dBA nets a new S/N of 75dBA. Doing the math you can see that as we listen at progressively lower power levels, the noise floor begins to compete with the music. To listen at the highest S/N, you need to set your system's gain structure so that the device with the highest S/N (usually the preamp) is set to deliver the most voltage to a device with the lowest S/N (usually the power amplifier). That means if your power amplifier has only an input sensitivity switch, set it to the lowest sensitivity ( 2.5 V in our example). If your power amplifier has input level controls, set them fully CCW and set the preamp volume control to around 2 o'clock. Turn the amplifier's volume controls CW until your preferred listening level is achieved. At this point, pause the music and listen to the sound coming from the loudspeakers. If you hear nothing but silence, you've achieved your goal. If you want to further test your system's S/N, start with the preamp's volume control set to minimum, the amplifier's sensitivity switch set to 1 volt and/or your amplifier's volume controls set to maximum. Start the same CD and slowly increase the preamp's volume control until you achieve the same listening level as in the first test. Now pause the music and listen. You may notice some low level hum and/or noise that wasn't there before. The more efficient your loudspeaker, the more revealing this test will be. Lee

Gil, Good article. Here's an interview with Geddes by Voice Coil magazine. Lee Earlgeddesinterview.pdf Earlgeddesinterview.pdf Earlgeddesinterview.pdf

PWK wrote an article entitled The Trouble with Attenuators which appeared in the November 1958 issue of Audio Craft. If my memory serves me correctly, he concluded that having boost/cut controls on a loudspeaker's network would be like asking some parts of the orchestra to play louder or softer than others. If anyone can post this article, I'd like to add it to my collection of PWK's papers. Lee

You might want to look at these. They expand and lock the plug into the socket and will handle #10 wire. http://cgi.ebay.com/12-Locking-Banana-Speaker-Cable-Plugs-GLS-Audio-P-BL12_W0QQitemZ200277199417QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2ea1738a39 Lee

Obviously, my cut and paste didn't preserve the paragraphs in my Word document. Klipsch Forum.pdf

As a contrarian, I am compelled to respond to the tenor of Amy’s note about DIYers and “Improvements” to Klipsch loudspeakers.In the Vol. 7 No. 2 February 26, 1966 (Revised March 1972) issue of Dope From Hope, entitled Quality Control, Home Construction and Trade Marks, PWK acknowledges Dr. Irving Gardner as the author of the expression, “You can’t make what you can’t measure, because you can’t know when you’ve got it made”. As someone who owns way too much test equipment, I’ve come to appreciate two other related quotes:1. “Not everything that can be counted counts and not everything that counts can be counted.”2. “When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced it to the stage of science.”The first quote is attributed to Albert Einstein and the second to Lord Kelvin.While none of the three quotes cited specifically addresses acoustic measurements, they certainly apply—up to a point. PWK’s early loudspeaker measurement capability was limited to frequency response plots and using his two ears. By the time I was visiting his lab in the 1970s, he had added the ability to quantify “modulation distortion”. He had identified an audible problem and was able to measure and correlate the electrical results with what he heard. As a result of those measurements, he wrote several classic papers on the topic. At about the same time, a young PhD upstart named Richard Heyser was wrestling with the dilemma that measurements weren’t always correlating with what he was hearing. The ultimate outcome was that he developed a revolutionary methodology, Time Delay Spectrometry (TDS) which gave us new ways to help narrow the gap between what we measure vs. what we hear.Modern day loudspeaker measurement tools such as TDS, FFT, finite element analysis, MLS, etc. are available to help us further correlate objective measurements with subjective perception. Many of these tools are available free or at low cost to the Forum member.I hope the above lengthy preamble establishes that objective measurements no matter how sophisticated still fall short in their correlation with the subjective listening experience. To claim that, “…Klipsch has the best facilities…” raises the question of ‘best at what?’ An anechoic chamber has to be huge to allow for valid low frequency measurements. TDS has all but negated the need for an anechoic chamber at least from about 200 Hz on up. Don Keele’s ingenious close microphone measurement technique can accurately fill in the frequencies below 200 Hz. I’ll concede that the automated transfer function measurements and polar plots that Klipsch probably uses is a time saver for the loudspeaker engineer. However, a Forum member can purchase either the Linear X software Klipsch uses or any number of high-quality programs that will generate (as PWK would say) “squiggles on the graph paper”. He or she can purchase relatively low-cost, high-quality mikes and have a measurement system that will have a high confidence level. As an aside, any Forum member who has measured loudspeakers soon learns there is no such thing as the frequency response of a loudspeaker. So, where does that leave the Klipsch Forum member who thinks he or she has an “improvement” to offer for their Klipsch loudspeaker? Amy’s recitation of the party line that, “…we neither condone nor approve of any “improvements” to our design, and stand firm in believing our designs are the best they can be (until proven otherwise).” serves only to reinforce the Not Invented Here (NIH) syndrome.Let’s take one sorely-needed and long-overdue “improvement” to the Klipsch Heritage line. The K-400 horn was introduced in 1963. That’s 47 years ago. At the time, the K-400 met PWK’s amplitude and polar response goals and was able to work in a 2-way or 3-way application. Anyone who has heard a tractrix horn upgrade from the K-400 will attest that there is no contest as to which sounds more like voice or music. Isn’t it a bit ironic that almost every Klipsch loudspeaker from the $250.00 per pair B-2 to the $20,000.00 per pair Palladium P-39F sports at least one tractrix horn except for the Heritage line?Another long-overdue “improvement” in the Heritage line is the crossover networks. According to my sources, Klipsch uses the LEAP crossover design software. This program offers a fill-in-the-blanks-and-hit-Enter key approach to network design. However, the program fails to properly address the amplifier/loudspeaker interface and the slopes are too gentle to prevent driver interaction. ALK’s popular ES networks offer a near constant impedance load to the amplifier and the steep slopes eliminate any audible driver interaction. I have to disclose that my Klipschorns and Belle have Al’s trachorn and ES networks. As Daddy Dee and fini will attest after several hours of listening, those improvements have transformed my Klipschorns to higher level of sound reproduction realism.One could interpret the line that, “…our designs are the best they can be (until proven otherwise).” to mean Klipsch knows what is “best” and you as a proud Klipsch loudspeaker owner will have no say in suggesting “improvements”. After all, it is their company and ‘He who has the gold makes the rules’.How about if Klipsch offered to consider product “improvements” from those who purchase and listen to its products? Put a “Product Improvement” form on the web site that a Forum member would fill out. The member would have to be specific about a proposed improvement. Not just say, “The bass needs to be less boomy in my Model XXX loudspeaker”. Instead he or she might write, “If you add a layer of 1” damping material behind the port, the bass is smoother and I’ve attached some before and after measurements showing a XX dB variation improvement.” If an improvement were approved by the Klipsch engineering staff, the associated upgrade kit could be made available through Klipsch dealers.Klipsch is to be commended for hosting a forum that allows its members to both praise and occasionally pillory the products it manufactures. I hope the above “tweaks” will generate some interest and discussion. Lee

Oops, I meant Bombay. Lee

Jay, Here's a generator built by Microsoft for their Punjab tech support personnel. Lee

CigarBum, Won't either horn require a new motorboard? ALK has all the parts needed for a Belle and there's a pix of a Belle with the added riser on his web site. Lee

Thomas, I doubt you'll need to "break in " a Klipschorn woofer. I doubt you could even if you wanted to. PWK wrote the following in the Volume 2, Number 7 Dope From Hope dated June 1, 1961: "Our big horn (Klipschorn) will produce one acoustic watt at 32.7 cycles per second with 1/16 inch cone motion." According to the Volume 9, Number 2 Dope From Hope dated August, 1968: "....a sound source radiating from a trihedral corner with a uniform polar pattern will be radiating one watt of power when the sound pressure measured at 4 feet is 118 decibels." The peak-to-peak excursion of a compression driver diaphragm is far less than a cone-type driver. Lee Lee

I hear that all Yugos came with an electric rear window defroster to keep your hands warm when pushing it in the winter. Lee

Coytee, Here's a web site that discusses the idiosyncrasies of the Thorens TD-124 and perhaps how to correct your wandering speed issue. http://www.soundfountain.com/amb/td124page.html#motor Lee

Carl, Chances are the first band is brown, not gold. The value is 1,000 ohms and the tolerance (the gold band) is + or - 5%. Based upon the color and shape, it looks to be a wirewound type. From the size it could be a 1/2 to 1 watt rating. Do you have a way of measuring the resistor? Here's one of many on line resistor calculators. http://www.dannyg.com/examples/res2/resistor.htm Lee

Dee, Yeah, I remember Take-A-Taco but I don't think we ever got anything "to go". If you didn't want to make the (then) long drive to MC, there was Browning's El Patio off University Avenue which back then was a gravel road and called Hayes Street. Our favorite order there was the "Summer Plate" but I couldn't tell you what was served. For the best burgers, you couldn't beat a Number 2 Wes Hall's Minute Man hamburger grilled on an open flame and apple pie heated in the futuristic-looking Amana Radarange. Lee

Dee, Did you eat at the original Mexico Chiquito in Rose City? I remember eating there in the early '60s. The dessert was always a cube of sherbet--yummy. Lee

Yesterday I attended a professional AV equipment show in Springfield, Missouri. At one of the mini-sessions a presenter showed off a powerful AV design tool called AVSnap. As a long-time user of SmartDraw and a dabbler in Visio, I was mightily impressed with the capabilities of this product. While each $125.00 SmartDarw "upgrade" offers fewer new and useful features, AVSnap seems to do it all and the program is free! It is frequently updated to add features requested by the users at the AVSnap forum http://www.AVSnap.com If you are in the AV design business or want to professionally document your home AV system, give AVSnap a try. You can learn the basics of this program in a few minutes. Here's a link to a review which touches on the highlights of AVSnap. http://www.avdocumentsolutions.com/avsnap/AVSnap%20Article.pdf While the default symbol library lists Altinex's products, I was told you can easily add ofther manufacturer's gear. Download AVSnap from http://www.altinex.com BTW, Jack Gershfeld, the founder and CEO of Altinex, Inc. (who also wrote the AVSnap program) was a co-founder of Extron the high-end AV equipment manufacturer. Lee

djk wrote: The DCX2496 has room for improvement, specifically the 17 $0.25 quality opamps and 15 polarized electrolytics in the signal path. Easy to see why you are not impressed. Most pro gear is little better, so I modify it. The EV Dx 38 fairs little better. A quick count of those pesky polarized electrolytics shows at least 15 in one input/output channel. The EV Dx 38 uses 5532 op amps ($0.51) which are almost thirty years old and are getting long in the tooth. The use of the NJM4556s ($0.56) in the output stage is laughable. This device is in the family tree of the replacement for the LM741 which is a poor op amp for quality audio. Lee

PWK spent many happy hours taping his local symphony orchestra. I wonder what recorder he used. Gary, In the mid to late '70s I was fortunate to tape record the Arkansas Sympathy Orchestra with PWK in Little Rock. The players were pretty bad (hence his renaming) but it was live music and a good reference for the ear. Since Paul and Valerie were contributors to the orchestra's fund raising entity, he had free reign "behind the curtains". PWK used a Revox PR99 MK II 1/2 track running at (I think) 15 IPS. http://www.reeltoreel.de/worldwide/PR99-2G.htm He used a pair of spaced omni AKG mikes flown from the light grid. I used a Tandberg 10XD 1/2 track with Dolby running at 7.5 IPS. http://www.bassboy.com.au/getreel/site/samples/tandberg/10xd/10xd.htm The mikes I used were a Neuman U47 & U87 in a mid-side (MS) configuration also flown from the light grid. One of my fond memories of those sessions was when we were setting up our gear. I was using some rather stiff microphone cable and complained to PWK that it wouldn't lie flat on the floor. He gave me that mischievous PWK "look" and said, "Lee, it can't possibly lie flat---it's round!" With the exception of Otari, I have never been a fan of Japanese-made decks. If there is a brand worse than Dokorder, let me know! Most have poor tape path geometry when trying to use 1.5 mil tape. Some Tascam models were OK but the multi-track decks needed outboard noise reduction to compensate for the non-standard narrower track width. As a past owner of both Revox and Tandberg decks, I'd probably recommend any 1/2 track high speed (7.5 & 15 IPS) Revox from the B-77 forward. Keep in mind that Revox used heads with a round profile shape as opposed to the more conventional parabolic shape. This allow for better head contact at the expense of accelerated headwear. BTW, headwear increases (or decreases) as the square of the speed. A deck running at 15 IPS will wear the heads four times faster than the same deck running at 7.5 IPS. If you have a vintage deck and need replacement heads, alignment tapes or recording media, I highly recommend JRF Magnetic Sciences. http://www.jrfmagnetics.com/ I've used John French to relap a dozen or more 1" & 2" 16 and 24 track heads as well as the source for new heads. With proper head alignment, you should be able to get at least two lappings before the head gap becomes too wide. Lee

You might want to try the Generation II locking banana plugs from GLS Audio. http://www.speakerrepair.com/mm5/merchant.mvc?Screen=CTGY&Category_Code=locking I just bought a dozen of them for my test bench them and they work great. Unlike many of the other banana plugs on the market, the GLS will accept #10 wire. Note that the GLS lock themselves to the mating connector making for a secure connection. A 10-pack on eBay sells for $ 3.19 each with free shipping. Lee

duder, Check with Al K. He found a cane grill cloth for my horns and Belle that is real close to stock. I've found that after thirty+ years, my cane grill cloth had yellowed with age and since I was upgrading to the Trachorn motorboards, cleaning became a moot point. Lee

Current theater design (read as you can't sell seats behind the screen) usually doesn't allow for the 45-inch depth of the MWM and its ilk. The 23-inch depth of the 884 allows for plenty of bass in a smaller footprint. As for bottom end performance, when I was sitting in on the voicing of a Malco theater here in NW Arkansas, the response of the multiple 884s was flat to 30 Hz and during a test screening of Transformers (digital DLP projection), peak levels in the 20-40Hz octave easily hit 130 dB halfway back in the house. According to the theater owner, the audio level was 4-6dB below the normal cinema levels! Lee

Gary, Here's one from Harman International that's pretty graphical. You can view the data with the Waves or Modes tabs at the bottom. www.harman.com/xls/Room%20Mode%20Calculator.xls Lee

Jim, Back when I wore a broadcast injuneer's hat, we had a '40s vintage backup AM transmitter. Back then (1992?) the law required that broadcast transmitters with capacitors containing PCBs had to be upgraded to non-PCB caps and the old caps disposed of properly. You also had the option of building a dam around your transmitter to keep the oil from leaking out. Of course this meant a lot of fly-by-night disposal companies sprung up and for a fee (I think we paid $500.00), they would place your deadly PCB-laden caps in a 55 gallon drum, and take them to a gubment-approved disposal site. Yeah, right.... One local station which had a 50,000 watt AM tranmitter chose to construct a concrete curb dam around the transmitter rather than replace the expensive replacement caps. I'm sure the replacement high voltage cap cost was in the thousands of dollars vs. a few hundred to build a dam. No brainer there. As I understand it, the primary danger was not PCB (polychlorinated biphenyls) itself--it was routinely handled by workers in the transformer and capacitor industries---it was the toxic by-products emitted if the PCBs were involved in a high heat fire. PCB was used because it was an excellent insulator, had a high flash point and was stable over decades of use in a transformer or capacitor. Lee

We've had XM for about 3 years. The lovely and gracious Paula has a GM version and I have a dockable version for home and on the road. Since my home unit docking unit is a glorified boom box, I can't speak to the quality issues raised. My biggest complaint with the XM music channels is they are programmed like terrestrial radio and not a new paradigm for the listener. I don't want to hear the Top 40 on real jazz (or any other music channel). Just to pick an example at random---Paul Simon has recorded well over a hundred songs. You wouldn't know it from the playlist on The Bridge. How many times do we have to hear Mother and Child Reunion in a week? While the music channels may be commercial free---they are not DJ free. Sometimes I want to throttle Lilly on Watercolors. Dammit! now I can't get Mother and Chils Reunion out of my head...... Lee