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PrestonTom

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  1. I suggest using a cheap RMS voltmeter (or borrow one) and measuring the AC voltage out at low, middle and high frequencies. Is the AC output within 10-15% across these frequencies. If so, then it is accurate enough. If it is off by 50%, then that is off by 6dB, If it is down by 30% that is about 3 dB. That is for the output. As far as the input (the exact frequency), it will be close enough. Now, the big question regards the speaker output (you have only measured the voltage going into the speaker). That is the open question .... it depends on the speaker. That will require a microphone. Measuring this at very low frequencies can be problematic (mic placement and speaker location relative to walls, corners, etc). Good Luck, -Tom
  2. Geoff you are asking a reasonable question. Unfortunately too much folklore is involved. If the crossover frequency is around 500 Hz (I forget the exact number). The wavelength is 2 ft and longer. A bit of foam in the back does very little. So lets get the notion that it is absorbing the back wave off the table. What the foam or pressed fiberglass does is effectively "make the volume of the cabinet seem a bit larger". This where the VAS comes into play. When building JBL cabinets, the rule of thumb is that 1 inch lining will "create" a cabinet that is about 10% larger. So does your Kappa driver need to see "more volume". Adding foam can make a difference, does the cabinet design need It? If one wanted to be methodical, you could always do a before-and-after measure. Unfortunately, many on the forum do not start with a design based on goals. Yes, homework is involved. Good Luck, -Tom
  3. This reminds me of why it is difficult to diagnose and prescribe via the internet. I had a friend of a friend ..... who complained of sibilance (as he defined it). He had received all sorts of suggestions (taming things with a tube amp, all digital systems are bad, horns are bad, crossover need to be re-capped, change amps, sources, pre-amps, dampen this and dampen that, etc). I finally went over there since he lived near a friend I was visiting. The diaphragm on the mid-range compression driver was damaged along with some debris rattling around inside the driver. Th only reason I spotted it so quickly was that I had a similar problem a few years before. The sound was distinctive , especially when you ran some test tones through it at a sufficient volume. Although I referred to it as "harshness" and not "sibilance". Interestingly, the other speaker sounded fine. That data point, however, did not limit the suggestions for the "system-wide" cures regarding, amps, caps, etc, etc Good Luck, -Tom
  4. Those cabinets you built for your 2-channel system have always been an inspiration for me. Beautiful !!
  5. You guys need to be more systematic in your approach. 1) Look at the volume of the cabinet 2) Look at the VAS for the klipsch driver in question 3) Look at the VAS for the Kappa driver. Again, this an issue of design and not "try it and listen". That does not come until later. Hopefully, there will be some measurement in between. Good luck, -Tom
  6. It sounds like you have a good strategy. I also like bass horns. Good luck, -Tom
  7. Is it the horn or the driver? If it is the driver, then the K-53-K was used in the original (1985-1989). If it is just the diaphragm on the driver, then check with Klipsch or Bob Crites. If the horn is damaged, you would be surprised what you can do with epoxy. Good Luck, -Tom
  8. John, Do you feel this ringing or whatever is strong enough that one could measure it. For instance would it be discernible on an impulse response? (with and without the rope caulking).
  9. Not to detract from Claude's work, but if you have working Altec 416's they are a valuable woofer that can be used in various ways. Over at DYaudio there are some highly acclaimed designs using that woofer (notably the Oaken cabinets, my spelling might be off). There are a number of choices. Running a simulation is a good idea, but please keep in mind the the Altec 416 was produced for a number of years and not all versions have identical specifications. Good luck, -Tom
  10. I am not a Klipsch engineer so I am only guessing...... The "mumps" allow the horn (for its size) to control the dispersion down to a lower frequency. So look at these facts 1) a new horn costs money to develop, prototype and manufacture. 2) there would need to be a sufficient market to amortize these costs. 3) a controlled dispersion (CD) horn like the K-510 and K-402 do not "beam" as you go up in frequency (IOW, the on-axis and off-axis frequency responses are roughly comparable). A side effect of #3 is that to some folks the CD horn, if it is eq'ed for the "CD compensation" to be flat on axis, then the "extra" off-axis energy may make the horn sound a bit "forward". OTOH, for some a CD setup sounds better (see Toole's work for a detailed explanation). While in a auditorium, then CD is essential (all seats hear a similar spectral profile). So it could be that there is no strong benefit of shifting the crossover point on the mid-horn lower in frequency. For a 15inch woofer like the K-33 (on the Cornwall), the woofer's dispersion will approximately match the mid-horn's dispersion at around 700-900 Hz. So no strong reason to cross lower (distortion on the mid-horn may also increase if the crossover point is lowered). So mumps make perfect sense for commercial application, but there may be push back by some for domestic environments. Mumps on a newer K-510 makes sense because the vertical dispersion is now better controlled (uniformly) to a lower frequency (while the horn remains 9 x 15 inches). It really is a system-design issue, with all of the trade-offs etc. These are just my thoughts and BTW, I love a controlled dispersion speaker system. I think they sound wonderful. Good luck, -Tom
  11. What is it that you are expecting this material to do? IOW, what is the problem you are trying to fix?
  12. The additional caveat is that the vendors have changed over the years. The original K-31s were manufactured by Pyle (at one time owned by Klipsch). Later they were made by someone else (although I understand that the specs and manufacturing jigs were the same). I think in more recent years there may have been another change in manufacturer. However, I stopped being concerned about it.
  13. Not really, I posted this last month "Years ago, Gil posted the JAES article on the Jubilee. Search for that. It lists all the T/S parameters. Those are correct measured specs for the K-31" It is still correct. These are for the K-31s (also used on the Jubilees). I was told by an engineer at Klipsch that they are correct. One of the reasons for some of the part number changes over the years (possibly not all the reasons), was that the k-31 woofer when it was mounted in the Jubilee required a 1/4 inch gasket for clearance (between the woofer and the splitter). That combination of woofer and gasket necessitated other part number.
  14. Yes, I noticed that also. I assume there are typos in those specs. There may be others (probably).
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