Article about setting up controlled-directivity waveguide type speakers

Discussion in 'Room Set Up, Audio Theory, and Measurements' started by BillWaslo, Apr 29, 2012.

  1. Hi,

    I was getting bothered by several mentions I've seen in forums suggesting that the reason to toe-in waveguides was to minimize some kind of defect, so during some down time I wrote up a small article with diagrams and discussion about the real reason for toe-ing in. Not because we have to, but because it's the only speaker type that can really take advantage of toe-ing!

    It's in the DIY Sound Group "Articles" section at
    http://www.diysoundgroup.com/forum/index.php?action=articles;sa=view;article=1
    =================
    edit:

    Here is the direct link to the pdf file of the article itself.

    url=http://libinst.com/PublicArticles/Setup%20of%20WG%20Speakers.pdf

    -Bill Waslo
     
  2. Thanks for the nice article, Bill.


    Your mention of time/intensity trading may have saved me from making a setup mistake.


    I was thinking the easy way to set toe-in would be to just move sideways across the listening area and adjust for the most even SPL reading on an SLM.


    However I had forgotten about the time part so would not be right.


    Any idea on the relative importance of time vs. intensity in determining the perceived loudness (pr should that \be directionality)?
     
  3. Not sure if Wayne Parham likes links to his Pi Speakers papers, but they are wonderful resources of information.

    JSS
     
  4. Bill, thanks for that article.


    It's the most pithy summary of best practices for front speakers that I've seen.


    Do you mind if I put a link to it on my newish blog (seriousaudio.blogspot.com)?


    Since it's hosted by your company, I thought I'd ask before doing it.
     
  5. Thanks, I'd appreciate if you did link to it. It might bring a bit more traffic to this forum, too.
     
  6. It's up. http://seriousaudioblog.blogspot.com/2012/04/great-article-setup-of-controlled.html


    Comments welcome, of course.


    And good idea about driving traffic here. I included a link.
     
  7. Thanks for great article BWaslo :)
     
  8. Thanks Maxmercy. Wayne is the indirect originator of much that is in Econowave.
     
  9. Agreed.
    A great read for those of us who've never owned (and are planning to) constant-directivity speakers.
     
  10. Fantastic article, Bill.


    I'm not sure why I hadn't realized/understood the time alignment aspect before now, but it makes a lot of sense after reading that.


    Seriously, Thank you.


    Steve
     
  11. Tannoy has been recommending crossfiring since at least the 70's. http://www.hilberink.nl/codehans/hpdtech.zip
     
  12. Excellent lay explanation of the effect!

    The effect to work requires constant narrow(ish) horizontal directivity, so it would be nice if Don Keele could be mentioned in the credits. And maybe also the JBL 4430 team?
     
  13. Sorry I didn't mention it in my earlier post, excellent job Bill!
     
  14. Sorry for the thread necromancy, but this seems the best place to answer my question.


    If planning to toe-in as the articles above suggest, would it be beneficial to separate the controlled directivity device of a loudspeaker from the non-controlled device? I.E. - allow a waveguide to be toed-in and the woofer aimed directly at the listening position? I know that lower frequency sound doesn't beam like high-frequency, but would a woofer toed-in as heavily as the waveguide be affected detrimentally if crossed over at 1500Hz or lower?
     
  15. The woofer in these kinds of speakers is chosen large-ish because that gives it a matched directivity at the crossover frequency, so the speaker can sound more like a single source rather than having an abrupt change in directivity at the crossover point. You want it to do what it does, directivity wise, that's part of the design. At lower frequencies, the directivity gradually decreases rather than all at once. So, leave the woofer toed-in as well, to keep the off-axis sound better matching the on-axis sound.
     
  16. Thanks! That makes it much easier to build, too. I was assuming that it would already be discussed if it was a worthwhile experiment but I had to ask. ;)
     
  17. The document doesn't mention any specific angles. And the toe-in, in the setup with large toe-in, seems to be less than 45 deg (from the line joining the 2 speakers)
    Assuming on axis FR is flat, wouldn't 45 deg toe-in be enough ?
     

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