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No port? But bass reflex, how do we work out enclosure alignment?

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  • #16
    Okay I have done some hefty research on this including chatting to renowned speaker designers. Either I have totally misunderstood the concept or there is two sides of the coin and I only came across one side of it.

    I am happy to break the myths, I am here to learn but I need to understand the concept that your proposing so I can get a take away from this.

    So from what I gather, when as for example Paul Carmody suggests a two option in the Amiga enclosure design one with a smaller box volume with a slightly larger port really only is reducing the low bass which in turn gives us better transients? Remembering that the Amiga enclosure is bass reflex and that decreasing box volume it does decrease low bass so that I understand. Paul O, essentially that is what your saying right, lower QTC less low bass better transient response? But I thought in a closed box larger box doesn't necessarily give you higher F3 it actually keeps lowering the F3 so for a closed box ive lost the concept.





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    • #17
      Originally posted by Trdat View Post
      Your telling me when I switched from my closed box SVS sub at around .9 QTC to a .7 QTC DIY sub then improved that same DIY sub to a .58 QTC I was imagining things?
      Of course not. When you lower Q you lessen the possibility for boomy midbass, which tends to dominate the response, not in a good way. This assumes that all else is equal, which it seldom is.
      if I am crossing over the Visaton's to subwoofers around 150hz
      Crossing to subs above where the subs are directionally locatable isn't recommended, it severely limits where the subs may be placed. Using a pair of twelves to go to only 150Hz is a waste of driver capabilities and box size. For that matter if you're only going to even 100Hz the added size and complexity of a ported enclosure, and twelve inch drivers, doesn't make a lot of sense other than in very high output pro-sound applications. I fear that you may have chosen the Visaton design for the wrong reasons and may be trying to force a square peg into a round hole as a result.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #18
        If you're rolling your subs in @ 150Hz (and, then, I'd assume you're high-passing your (MASSIVE) Mk3s ALSO near 150Hz?), then the curve you're looking at in WinISD does NOT (really) make a bit of difference !

        Since you're using WinISD, go to the "EQ/Filter" tab and add a Highpass filter @ 150Hz. Look at your (bass) curve drop on your Mk3s ! !
        That 40-50Hz "hump" is NOW pushed down -20dB. You're not going to even notice that (prob'ly not even if your subs aren't running).

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        • #19
          Look at these box recommendations (for 1 driver) here:
          https://www.soundlabsgroup.com.au/mm...&Product_Name=

          Your Mk3 enclosure falls in the middle of these suggestions.
          The largest box has the biggest hump (+2dB @ 40Hz), but look at the smallest box - VERY "lean" curve (low Q).
          Again though, since you must be high-passing these at 150Hz, none of this really matters...

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          • #20
            Hey Trdat; I like your comments and questions. You want the truth ! My recommendation is to purchase Vance Dickasons Loudspeaker Design Cookbook. Mine is the fourth edition. It will answer all your questions regarding various alignments pros and cons without the BS.

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            • #21
              In a sealed box, a Qtc of 0.707 yields the lowest F3 you can achieve. If you build a larger or smaller box than that box with 0.707 Qtc, you have a higher F3 rolloff point.

              Later,
              Wolf
              "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
              "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
              "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
              "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

              *InDIYana event website*

              Photobucket pages:
              http://photobucket.com/Wolf-Speakers_and_more

              My blog/writeups/thoughts here at PE:
              http://techtalk.parts-express.com/blog.php?u=4102

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              • #22
                Originally posted by Regore View Post
                My recommendation is to purchase Vance Dickasons Loudspeaker Design Cookbook. Mine is the fourth edition. It will answer all your questions regarding various alignments pros and cons without the BS.
                Vance's book is a good reference source for newbies, but everyone who's weighed in here is well beyond the newby stage. I can't give a time line for Paul, Chris, Dukk and Wolf, but I was designing speakers 20 years before Vance published Edition One. Ten years after that, in 1997, I joined Vance as a Contributing Editor at Speaker Builder Magazine. This ain't our first rodeo.

                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #23
                  hijack (PM for BF) - well, not THAT private !

                  are you in your 70s Bill, (not that you'd have to answer, of course)?

                  I'm 65 and sometimes wonder how many on PETT are retired.
                  Actually I'd like to see a graph of the age distribution of the ("regular") TT users. Just curious.

                  Hey, don't let 'em screw up the NH caucus (like they did in Iowa), okay?
                  Take care.

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                  • #24
                    I'll be 50 this year. Built my first calculated speaker enclosure in 1989, then spent 28 years in retail electronic sales / car installations either full or part time.

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                    • #25
                      I'm 70 and still working, designing speakers and doing audio consulting. My knees won't let me ski anymore, so in winter I've got nothing else to do. In summer I play nine holes of golf five days a week, but that only keeps me busy until 11AM. New Hampshire doesn't have a caucus, we have a primary. After this debacle Iowa will go to a primary as well. The caucus system is as relevant today as a community barn raising, and they don't do that in Iowa anymore either.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

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                      • #26
                        Originally posted by billfitzmaurice View Post
                        Vance's book is a good reference source for newbies, but everyone who's weighed in here is well beyond the newby stage. I can't give a time line for Paul, Chris, Dukk and Wolf, but I was designing speakers 20 years before Vance published Edition One. Ten years after that, in 1997, I joined Vance as a Contributing Editor at Speaker Builder Magazine. This ain't our first rodeo.

                        Bill we are aware of your work and fully value your input. Obviously many of the others are also up there with their knowledge, its obvious their professionals. I am definitely not a newbie and the book will be to simple for me, so I agree with you there. At times post can get a bit complicated especially on the DIY forum while here its kept a little more simple. Many of the topics that are floating around have not been covered in a book, they are new concepts which aren't based on any research per se but rather taken from experience by experts which is not to say its not scientific. But a new book with clarification on these issues in particular on the questions in this post are needed for the next generation of speaker designers. Unless it exists and I have missed it...

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