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About THD+N

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  • Birthday 08/19/1964

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    Stoneville North Carolina
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    Electronics (amps, signal processors, mostly analog), speakers (and speaker building), technology, politics, camping and other outdoor activities.

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  1. If "everyday" people understood the thought process behind product development, they would be amazed. In some cases, the design is strictly driven by cost, which will yield a certain sound. In my case, I have the tools to measure changes and decide if the change is right for me. I didn't tell everyone this was an upgrade and to modify all Heritage speakers per my changes. In any audio forum, you have to do your due diligence and decide if you want to change or modify your gear based on other members who have posted any type of changes or modifications to said equipment. I am a member of all the popular forums, but rarely post because the egos and mania are just too much to handle most times.
  2. Pete, No scientific (or "real") test was performed to determine the inductor saturation, but you could hear it saturating. Bass got flabby and distorted much too early before power handling was an issue. In another life, I previously worked at Recoton and Audiovox (1997 to 2015), who owned the Advent and AR brand names. I worked closely with the engineers who designed and developed the later Advent and AR speakers. I designed and developed car audio. The Advent brand was price sensitive (from a production standpoint) and it showed in some products. Simple crossovers with small inductors that would just allow the woofers to handle the rated power, cheap (no brand name) capacitors, etc. Although the Advent Heritage was made prior to my employment at the company, if the bean counters would have spared an extra dollar or so, the Heritage crossover would have been respectable.
  3. I think the question should have been; Does the 10pi have a (fairly) constant impedance? The auto-former will more than likely introduce a huge impedance swing into the impedance curve somewhere. The only way to know is to measure it. My Klipsch La Scala's use an auto-former and the factory crossover had a large impedance swing. I rebuilt them into ALK clones. The impedance plot below is from an OLA with news caps (and incorrect surround. Notice the high Fs = 52Hz). The impedance peak at 600Hz is not a problem for any solid state amp. However, a vacuum tube based amp prefers a constant impedance for best performance (especially SET Class A amps, with no global feedback). The peak at resonance can be tamed as well, but it will require a huge inductor . The peak at resonance is not really an issue (a compromise) as long as the rest frequency range is fairly flat. The below impedance plot (DATS2 software) is from the same woofer (with correct surround; Fs = 39Hz) with a series notch filter. I have several SET Class A amps and they sound better with speakers that have a near constant impedance. If you tinker with speakers even for one project, the DATS2 software from Parts Express is worth every penny.
  4. The surround on the 2nd woofer is installed correctly. It looks like the "roll" is toward the front of the woofer, but it is, in fact, going toward the back of the woofer.
  5. I have measured one of two Advent Masonite woofers with DATS 2. This particular woofer (woofer #1) appears to be original except for a new surround. I'm not sure if the correct surround was used and have new surrounds coming from Rick. The Fs appears to be a bit high, but it still simulates well given the high Fs. My measured Vas appears to be inconsistent with other Vas measurements on the Advent woofer(s) posted here. I know the DATS 2 is accurate and my weight for the Vas (Added Mass Method) is accurate. The other Advent Masonite woofer (woofer #2) I have may be a total recone from the physical looks of it. It closely resembles a "real" Masonite woofer. However, it may be another derivation of the Advent Masonite woofer. The below DATS 2 graph is for woofer #1: Woofer #2 in question below:
  6. Here are the complete crossover component values for the Advent Heritage (Classic Heritage, twin woofer). I originally only replaced the caps, but then discovered at higher volumes, the iron core inductors were saturating. I replaced the woofer inductors with Erse iron core inductors and the saturation issue was resolved. I also replaced the tweeter inductor with an air core type. I used DATS 2 to make the measurements. Advent Heritage Crossover Values_062618.pdf
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