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  1. #76
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    86
    Posts
    147

    Default

    Quote Originally Posted by HeadScratcher View Post
    I have found this website extremely fascinating Loudspeakers his work is referenced a lot by people in the know.
    Whilst the basic cabinet may be simpler on the surface, probably far more effort is actually required for proper design, than a regular cabinet.

    Yes any one can route or jigsaw a hole in a flat board, but to make it work properly requires a massive amount of math, and there is an absolute ton of setting up to be put into practice.
    When set up properly they can sound absolutely magic, but half do it and you would be better off sticking with a sealed or bass reflex cabinet.

    So unlike the advice you quoted I wouldnít suggest people try it unless they are prepared to commit to it properly, or you will wind up with the acoustic issues they mention in spades, but that is not what a proper setup sounds like.

    Hereís a pic of the ball park I see the finished speakers looking like.
    I found that to be interesting reading with no surprises but I was disappointed that nothing was said about systems without cabinets which is what I want to study because as I've said earlier, it goes against everything that I've ever learned about loudspeaker system design.
    Harry

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    2010
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  3. #77
    Join Date
    Jan 2013
    Location
    Adelaide
    Posts
    5

    Default

    Hi there,

    Admiring your artistic talent and sketchup skills. Also admiring the drivers you've acquired... some of the best money can buy. Flipping through the pages of the post, I found myself really looking forward to seeing the build progress to a finished product... you can imagine my disappointment when I got to about page 5... NO WOOD?!! ) Whadda you mean no wood??? Where's the thingy's gonna go???

    On a somewhat serious note, being an acoustic engineer, I can see some issues with your no baffle idea. It won't give you the sound you were hoping for, at least not below about 2.5kHz, where you're likely to cross your RAALs. Open baffles are a somewhat different story, but the response will not only depend on the length & shape of the baffles, but also the size, shape and finish of the room and the speaker positions within the room. It's finnicky.

    An unmounted driver cone is a "dipole" source, compessing air on one side of the cone while rarefacting it in on the other as it oscillates. The baffle prevents the high pressure air to "leak" to the low pressure at the back and vice versa. The leakage is the worst when the edge of the baffle is less than half a wavelength away from the speaker cone. With wavelength being inversely proportional to the frequency, the lower the frequency, the greater the baffle dimensions required. (i.e. Speed = Frequency x wavelength, where speed is a constant at ~340m/s). With a no-baffle situation, the air is just going to be moved backwards and forwards around the edges. You'll likely end up with a very inefficient speaker with horrible, frequency dependant off-axis directionality.

    To add to this, although driver properties (cone suspension stiffness and damping, excursion etc) determine if they're "best" suited to sealed or ported box applications, most can usually be used in both. The leap from drivers in enclosures to open baffles is much greater, requiring a completely different driver design (stiffer suspension, longer travel etc). If you want to design high end speakers to rival your Cremonas, you may need to understand more of the physics behind loudspeaker design (acoustics, vibration, electrical systems) and check what the drivers you bought are best suited for. You may even want to invest in a loudspeaker design software package down the track (SoundEasy, LspCAD, LEAP to name a few), so you can model everything from enclosure design, driver characteristics and crossover design to room characteristics and loudspeaker placement within the room prior to building them. Some of the packages also combine ability to measure various driver / box / room properties as well as measuring the finished speaker response. A word of caution tho, I would strongly recommend brushing up on loudspeaker design theory (if you haven't already) before sinking any coin into design programs. They require a fair bit of background knowledge to master... especially SoundEasy.

    Anyhow, good luck, and I look forward to some progress in the new year.

    Cheers

    Boyan

  4. #78
    Join Date
    Aug 2005
    Location
    New Zealand
    Age
    63
    Posts
    235

    Default Catch up time.

    Howdy scratcher, how is the project? Did you bring it to a conclusion or is it still evolving?

    I've been a mite busy over the last year or so, with my current build being a set of PMS speakers.

    Heres where I'm up to at the moment.

    DSCF7467.JPGDSCF7482.JPGDSCF7483.JPG
    Dust Mite...Terrorising noses for the discerning...
    Pirongia Pens & Woodcraft

  5. #79
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Hey Dust Mite. Project is still ticking along... I am just putting some final touches on a CNC I built from scratch. Now I can build whatever I want

    First audio project is to build some lute shaped cabinets for the 18" bass drivers. I am still running open baffle speakers after all these years.

  6. #80
    Join Date
    Aug 2005
    Location
    New Zealand
    Age
    63
    Posts
    235

    Default

    Yo headscratcher ... you ever finish this project?
    How about a sitrep, its been nearly 3 yeras now.
    Dust Mite...Terrorising noses for the discerning...
    Pirongia Pens & Woodcraft

  7. #81
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Dust Mite I have procrastinated and procrastinated until I think I have run out of excuses to make. I haven't used the CNC in 12 months since my last water pump died. Sick and tired of being slack I have ordered some bits to get the CNC going again and get some of these projects back on track. All going well I should have most of the parts I need to get the CNC going again in the next two to three weeks. I am also trying to fix up many of the half finished things on the CNC like limiting switches and drag chains. I have built a new Z axis out of block of billet alloy which got rid of all the chatter problems I had and I got around to putting the second X axis ballscrew in so now it stays more square driving evenly from both sides. Promise by the end of May it will be working and woodchips will fly.

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