WMcD

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About WMcD

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  1. Gary had me going – good thoughts by him re Audassity. After some noodling: The criticism of room correction goes like this. We have a dip caused by a duplicate out of phase source from a room reflection (or another driver). If we goose up amp power in the narrow frequency response area of the measured dip, we’re still screwed. This is because we’re increasing the level of the duplicate source which is causing the destructive interference too. Call it a stubborn magic hole. However, the dip is localized and in the fr curve (importantly) we have regions of lower and higher freqs which are not affected by two interfering sources (because they are simply out of their range and they don’t overlap). They have magnitudes which are higher than the dip. But with enough signal processing we can affect them without affecting the dip. Sooooo. My theory is that we don’t try to lift the dip (because that doesn’t work). Rather, we lower what is above and below the dip in fr. In a thought experiment, we can’t fill the stubborn magic hole in the soil, but we can dig out the surrounding non-magic area in the soil to make the surrounding ground, level . . . down to the depth of the magic hole which we can’t fill in. Granted, now we’ve got sort of a level and flat -bottomed hole in the ground. We can go back and just lift up all of it. I have no idea whether this is what the processor is doing. But it makes some sense, maybe.
  2. HDBR, Thanks for the run down on the Hartsfield. It confirmed my research: There was the small woofer version convertible to the large woofer version. Then the large woofer re-design. Therefore, three versions of the bass bin. Sometimes I’d wonder why the dual woofer Jubilee wasn’t PWK’s first design; it is so elegant. Then I realized how expensive woofers were back in those days. I imagine that Hartsfield felt the pinch and had the small woofer as a starter. PWK’s first K-Horn used a small woofer too. OTOH, the labor of cabinet makers must have been cheap. All those angles, wow. The Hartsfield was far more complicated than the K-Horn. The lore is that Mr. Hartsfield contracted out the task of cutting pieces for his bass horn to two shops with each making different pieces. This was so that neither shop would have enough info to duplicate his design. Only the paranoid survive. My guess is that he did well to sell it to JBL. Maybe they found it too expensive to make. It's a beauty though. WMcD
  3. Actually there is some truth to this. I'll let you look up skin effect on Wikipedia. The article there does not make clear how much it could affect speaker wire. But look at http://www.audioholics.com/audio-video-cables/skin-effect-relevance-in-speaker-cables Incidentally, There was the opportunity to do an AB-X on zip cord versus braided CAT-5 at the first pilgrimage to Indy. I tried it with pink noise and found no difference in the AB part. Monster Wire was pull from this contest. I also ran freq response at the amp and at the speaker for a run of zip cord. There was no difference or maybe just one little data point. My recall is that Al K likes linz wire and I can't fault him for working to optimize his products. WMcD
  4. I should add: The AK-4 crossover has much more more steep filters which probably address the issue of the bass and mid having overlapping output and phase issues. My guess is that Roy used the Linear-X system of LMS and LEAP to design this. WMcD
  5. Sorry this is long. I didn't have time to make it short. Sorry I’ve been away. There have been a lot of distractions at work and home. It looks like BFM might have been asking for permission to contact me but I took it as just polite phrasing. Of course I’m always ready. Though I think open communication on the site is best. On the subject of testing. I’ll just say that it is difficult to find what is accurate. If you put the microphone a meter on axis in front the mid, you’re offset from the woofer. Maybe the microphone should be put on the floor for testing the woofer and then you’re offset from the mid. With these variations in path length the dips at the crossover freq(s) is going to move around. Move three meters out in the room the paths from the mouth of the bass bin and the mouth of the mid are pretty much equal, but room reflections hide the dips. (Which might be why PWK was not overly concerned.) Overall, it is tough to find a place for the microphone which reveals everything you want to know. In my view: Perhaps we can agree that an issue is the phase of the test signal as it is presented at the mouth of the bass horn and the mid horn over, say, an octave around the crossover freq. Assuming they are both sounding. If this is a polarity issue (reversing the feed lead) we may be lucky if the sound is 180 degrees out of phase at some freq, and then we correct by reversing polarity. However we can’t generalize between the K-Horn and the Georgian. Essentially: Delay from length causes phase changes. Linear phase change with freq. Also, any roll off causes phase changes. The roll off may be caused by the electrical filter, the mechanics of the driver, or even the response of the horn. IIRC this is described though a Hilbert transform. PWK mentioned it a little bit in an article. Going back to BFM’s analysis. It appears to me that you’re assuming that EV Georgian was correct (in polarity reversal) and PWK in the K-Horn was not correct (in no polarity reversal) . But we have to dig deeper. The Georgian and the K-Horn are different in important ways. EV and PWK might well both correct for their respective and different designs. As mentioned EV used second order slopes in the crossovers. PWK used first order slopes. That is going to cause a relative phase change in what the drivers are fed at the crossover point. These have different phase changes at their respective, and different, cross over points. Further, EV used its “reentrant” mid. (I like to point out that this mid horn is shown in M*A*S*H.) This is sort of what we see in bull-horns. I’ll let you guys look that up. But is a type of folding. The driver is at the front, the sound goes to the back, makes a 180 degree turn, and comes out to the mouth at the front. Effectively, the path is twice the overall length of the horn structure. Therefore, the EV mid horn is twice as long as it seems and has twice the delay of a similarly sized K-5 or K-400. (Actually, bull-horn have a second fold which is why the driver is at the back.) The bottom line: If the output of the mid horn is 180 degrees out of phase with the woofer near the crossover and causes a dip, polarity reversal can cure it. None the less, the situation is caused by phase issues caused by a number of factors which are unique to the crossover and length of the mid, plus the roll off of the horn and driver. This is relative to the bass horn, which has similar phase issues.
  6. Okay, I understand that you're trying to trace down what a could have been a demo used Klipsch salesmen. This is in contrast to some wacky questions we get like, "I heard an album but can't remember the name." But as a wild guess based on little information let me suggest Rampal and Bolling. The album was big in that time period. Very good. light jazz. OTOH it is not quite up to screaming flutes bringing the listener to his knees. In rock, Jethro Tull, used flute. "Thick as a Brick" is a rocker but not too much flute. OTOH, "Bouree" by Tull, using flute, is a jazzed up version of Bach. . I'd suggest you row around YouTube for more Tull. You might find your tune. WMcD
  7. I'm thinking about the open plan house. Just maybe there is nothing wrong with the speakers or amp. As I've described elsewhere: I had some speakers which had respectable performance in a bedroom. Then I moved them to the high school cafeteria to rock Led Zep . . . and, gosh, they were nothing. Later in college a buddy and I put his similar speakers and bigger amp outdoors in a parking lot to rock people with Fanfare for the Common Man. Again, they were nothing. It could be that the open plan house has very lively treble and no bass reinforcement. Still, I'd like to think your speakers and amp are up to the task. - - - Funny story. Year ago I was asked to repair some smaller Speaker Lab speakers owned by a young relative, actually a second hand gift from her dad. The woofers had stopped working without any reported abuse (yeah, right!). This happened when they had been moved to a yard for a party. I bought some woofers from PE and installed them with good results. Of course the voice coils of the original units were open (infinite resistance on a multimeter).. I took an Exacto knife to the voice coils and former. There was extensive charring. My conclusion was that someone had found the loudness control and bass knob on the amp after finding bass lacking outdoors. There was no point to challenging the "no abuse" yarn. We've all been kids, once. ______ Let me ask another question. These must have been purchased "used." Do you have any evidence they worked properly in recent days? WMcD
  8. I was testing my home made horns with a sine wave in a garage. Putting in 2.82 volts measured with a meter at the input terminals which is nominally 1 watt. Disaster. It was unbearable to stay in the room. About 103 dB Putting in 0.89 volts, nominally 0.1 watt was painful. About 93 dB. Putting in 0.282 volts, nominally 0.01 watt was loud. About 83 dB One reason not to use monster amps is that the 1st watt is where we listen, at best. I suspect that 100 watt amps may have distortion down there. WMcD
  9. This is for a high freq horn of course. There is an electrical circuit model where CM1 is the chamber in front of the diaphragm. If there is none Cm1=0 PWK would have seen this and I believe this made him experiment with a front chamber for the bass horn. Again, I believe that he knew it would be necessary to form a semi-closed chamber by the smaller slot. All conjecture on my part but it makes sense. At one time I did some calculations and found that the reactance of the weight of a K-33 diaphragm at about 350 Hz to be X. I guestimated the volume of air in the chamber in front of the diaphragm to be something like a cylinder 12 inches in diameter and 1 inch tall. The reactance was about X. When reactances are equal we get a resonance. Therefore I concluded this was a correct analysis. Then I used Don Keele's electrical model on Spice plugged in the values. It showed what is shown above, basically. I can't find all that right now. However since it was close and not off by an order of magnitude I was happy. Thinking further: there is the issue that resonances are damped by the loading caused by the throat. It could be that the slot reduces the loading. Some diagrams out there show the design has somewhat lower overall output. I thought the slot was lossy. But maybe reduces loading and does not damp out the resonance as much as a full sized slot would. This has some similarity to using a ported box in the back of a woofer. Response in a closed box is rolling off. However the port and box causes a resonance just as it rolls off to goose up the overall response (through the port) just where it is rolling off. Roughly, we get the lower half octave out of the port. The penalty is that below box-port resonance the response drops off very quickly. My best thoughts. Sorry if I talk too much. WMcD
  10. I say, use 4 ohms. One reason is that the K-Horn goes down to 4 ohms and we want to keep the amp happy. Generally they perform best when they are not loaded below their output design. The second is that amp noise will be be lower at the stepped down 4 ohm tap. There is no benefit to monster wire. WMcD
  11. I suspect that the ramp or prism is not very sensitive to size. Granted it may have some effect in directing the high pressure coming out of the slot to the two paths. The illustration of the slot is more interesting. It is reported as a low pass filter. I've written on this before in connection with the mystery of the slot. It appears to me that we have a low pass filter formed by mass of the diaphragm. Keele shows how high freqs roll off because of the mass of the diaphragm. In a way, that can be called a low pass filter. Essentially, the horn loading is taxing the force available from the motor. and moving the mass of the diaphragm bogs it down. further. It is a first order filler. What to do? It would be nice if we can set up a resonance between the mass of the diaphragm and a chamber in front of it. However if the horn throat is about half the size of the diaphragm we don't have much of a chamber. The solution is to close off the path to the throat with the slot.. Now we have a mass in the diaphragm and a spring in the semi closed chamber. We have to make sure that the acoustic impedance of the mass and the acoustic impedance of he chamber are equal at about the freq where the freq response is rolling off. Now we have a second order filter which can have a peak just where we need it. It becomes a second order filter with a peak where we need it. Baranek shows something like this. I will admit that there might be something to the Klipsch design. Bruce Edgar did an analysis which IMHO missed this point. He apparently made some straight horns and could not make the slot work. If I understand correctly he thought the improvement was limited to the Klipsch structure. Maybe that is correct in that the prism and the right angle turns act to seal off the slot a bit. We have a more effective sealed off chamber. This may come as a bit of a surprise. With a first order filter there can't be peaks. Usually we see second order filters designed so that there is just a sharper roll off. However, they can be designed to make a peak before rolling off. WMcD
  12. I object to you. I object to intellect without discipline; I object to power without constructive purpose.
  13. Maybe someone here can suggest a program to recover your present HDD. I replaced the HDD in my "go to Starbucks" laptop with a Sandisk SDD. This required an outboard USB housing for the transfer which was about $15 at MicrCcenter. The transfer software worked very well. I was worried that if something went wrong I'd have a ruined HDD and SSD, but no. The laptop boots much faster and I feel more secure. Because this went to well I put Samsung SSDs in my office and home laptops. Again, the transfer software worked well using the little USB housing. You'll have to shop around for best price. Microcenter is a bus ride away for me and the tech people seem very competent. From what I see, size for ;price is pretty much following Moore's law. But you have to jump on the merry-go-round at some point. I know there are things to read on the Internet that SSD's are not bullet proof. But overall they seem to be a real advance and worth the money. I see you have an external drive and I don't know the exact process for that. WMcD
  14. I certainly agree with UH1. My thought was that one woofer system failing is possible but two failing is less likely. It is surprising how good a stereo pair can sound working with one woofer. The push test will require getting the (front) grill off. IIRC the Forte has the mechanical trapped ball type fastners. The grill can be pried off with a butter knife or putty knife. WMcD
  15. I know you checked, but I suspect the amp. Are mains set to small? by mistake? This would cut the bass. Listen to the amp on headphones if possible or with other speakers. Can you borrow another amp to check these. Even an old dorm room type. Gasoline is never a solution. Where are you located? Maybe some forum member can visit. WMcD