Kit281 Active Crossovers

Discussion in 'Home Theater Projects' started by Michael R Price, Aug 15, 2004.

  1. Michael R Price

    Michael R Price Screenwriter

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    I posted an article about my active crossover project.

    http://jdprice1.home.comcast.net/activexo/

    I decided to restrain my enthusiasm a bit in the article but I won't here. I think these speakers are awesome now, building on the Kit281's strengths in dynamics and balance and improving on some weakness in the midrange and treble. A lot of songs that came out a bit messy or harsh before, sound ridiculously good now. One of my friends said it was the cleanest sound he'd ever heard... then he proceeded to play along with an incredibly distorted song by "Live" on his electric guitar at karaokeable levels. "I alone love you, I alone tempt you..." [​IMG]

    I am trying to judge interest by other Kit281 owners in this project, so that I can organize a PCB purchase if it's worthwhile.
     
  2. Brian_J

    Brian_J Second Unit

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    Very interesting. I have long come to the conclusion that the weekness of this system lies in the crossovers. I especially think this is true with the center channel, which sounds extremely week for a speaker of this size with woofers so large. I just do not get it.

    Count me interested.

    Brian
     
  3. AlexKunec

    AlexKunec Stunt Coordinator

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    Im just about to build an active xover for my HE10.1s, but i need a little more knowledge on active filters. Whats a good book or website that I should read?

    I plan on building my xovers with opamps instead of jfets as it would be much easier. You mentioned that jfets are higher fidelity, however, Im not convinced that I will notice the difference. I feel that if Linkwitz could use them in his orions, they are more then enough in my HE10.1s.

    P.S. Keep us updated on ur prject, i really enjoy reading about active crossovers.
     
  4. Michael R Price

    Michael R Price Screenwriter

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    Brian, the crossover for the Kit281 is actually very elegant, perfectly designed and it would be hard to improve on this passive crossover without going to something much more complicated/expensive. It isn't a weakness, but the woofer breakup makes any crossover in this system difficult to accomplish.

    As for the large center channel, that one is a little weird because the efficiency of the midrange driver does not match up. They actually had to reduce the output from the woofers with a series resistance. It shouldn't sound "weak" but I could understand if the bass was a little slow. Unfortunately I don't have an LCC so I haven't done any work on converting it to an active system. Despite it being a 3-way, the LCC should be relatively easy to use actively (there is plenty of driver overlap) and you would get a huge improvement in the bass.

    Alex, John Pomann's old site is very helpful. Also you can play around with the active filters in LspCAD (a free demo version is available). Opamps will work fine. If you aren't worried about sound quality in the finest sense, NE5532s will work great... I got ten from Apex Jr for 4 bucks. [​IMG]

    http://www.snippets.org/filters/crossover.htm
     
  5. Brian_J

    Brian_J Second Unit

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    My comments about the crossover were related to my impressions of the center channel, not the 281 speakers. This due to the thin sound from it, which just totally baffles me considering how large this speaker is.

    I literally took the crossover apart and put it back together again three or four times convinced I had wired it wrong. But alas, no change. I even added a resistor to the mid range and tweeter upon suggestion of adire and that while helping slightly, sadly does not address the problem. I almost want to stick a 281 crossover in there and bypass the midrange altogether.

    Brian
     
  6. Michael R Price

    Michael R Price Screenwriter

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    Wow, that's weird. If you put it in the position of one of your main speakers does it still sound that way?
     
  7. Brian_J

    Brian_J Second Unit

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  8. Brian Bunge

    Brian Bunge Producer

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    Brian,

    I haven't heard the 281's yet (still need to invite myself over if I can ever find the time[​IMG] ) but I never felt the LCC sounded thin. Keep in mind that I was coming from an ACI Emerald as a center, so the bass response was noticeably better after adding the LCC. Maybe I really need to hear the 281's! [​IMG]

    Michael,

    That's great work there. Nice work, as usual![​IMG]
     
  9. Michael R Price

    Michael R Price Screenwriter

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    How does this simulation look? This is for the "ridiculous slope" filters, with my actual nearfield measurement of an AV8 and Parts Express published tweeter sample measurements. My tweeter measurements were hindered by microphone and reflection issues. I've found the individual driver responses track the simulated ones very accurately (after all these are active filters with 1% and 2% components). The response around the crossover point is a little less certain, leaving some room for tweaking. Because the crossover window is narrower and lower in frequency, it should not be too hard to make this sound better than my current 6th order crossover.

    [​IMG]

    Anyway, I'm wondering if anyone can tell me if they are interested in buying a PCB. It looks like if 10 people want them, it costs $20-30 apiece with all the other components for a stereo crossover costing $120 or so. Of course, the board can be used for any 2-way crossover, not just Kit281s... [​IMG]
     

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