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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Breezy Monitors

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  • Breezy Monitors

    Well, more than a year after I bought the parts, I finally finished a pair of speakers. Sad part is I didn't even have to build the cabinets. Life has been busy I guess.

    Anyway, these are a speaker designed to be an easy and inexpensive "high end" stand-mount monitor. I have always been attracted to the empty BR-1 cabinets that PE sells as a good bang for the buck option for when time, lack of tools, or lack of finishing skills prohibits cabinet building. I have tools, but not much time and minimal finishing skills. So, BR-1 cabs and easy: BReasy..Breezy Monitors. Cheesy I know

    As far as driver selection, I have always liked the Vifa/Scan ring radiators, and they have been used successfully in many speakers, some quite expensive. XT25BG60-04 was the choice. Having a fixed enclosure volume of about 0.50 ft3, I needed to find a driver to match. Fortunately I really wanted to work with a large diameter coil driver like the Dynavox, Morel, Esoteric Series, etc, and the new Dynavox LW6004PMR-N 6.5" units fit the budget and enclosure volume.

    Neither driver fits the driver recesses. I found the Silkie and Dayton Classic woofer both have odd frame size. Fortunately the openings were adequate. The XT25 fit in the recess with a small gap around the perimeter and the Dynavox fit as a surface mount. The diameter of the Dynavox was too large to accommodate the BR-1 grilles, so I removed the grille grommets on the baffle and used a sheet of black craft foam glued to the baffle. It provides coverage for the tweeter gap and grommet holes, and makes a nice suede-like appearance.

    As far as enclosure tuning, I cut the factory port down to 3.5" (I may to increase to 5") to the outside of the flare. The enclosure is lined inside with polyester batting. This appears to set tuning in the high 40s. I feel the low end is sufficient for most music.

    The crossover (schematic not drawn yet) was going to hopefully be simple. It kind of was, except once in the baffle the Dynavox produced a peak of about 5db around 1200hz that I had to create a notch to reduce to make things work out. Otherwise, it is a 2nd order electrical on the woofer and a 3rd order electrical on the tweeter. The xo frequency ends up at about 2900hz. I know this is high for a 6.5" two-way but it was comfortable for both drivers so I went with it. I feel like I liked this better than hammering drivers to a specific xo frequency that I wanted instead of letting the drivers choose, like I have done in the past. With the higher xo frequency and third order parts, it seems I was able to avoid notching the XT25's FS.

    I always get excited at the end of a project and end up quasi-reviewing the sound of my own speakers when I finish them, but I am going to avoid that (because who am I to judge them) and just say that I am very pleased with the result. Pics and charts to follow. Thanks for looking!
    Last edited by dynamo; 01-22-2018, 11:45 AM. Reason: added comment on port length

  • #2
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    Got the pics rotated the right way!
    Last edited by dynamo; 01-22-2018, 12:56 PM. Reason: figured out how to properly rotate the pics

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    • #3
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      In the measurements, feel free to ignore below 500hz or so due to refelctions. Honestly, not sure if I did the distortion measurement correctly, but I believe I did. Third chart in is about 2m away or so, fourth is 1m, and distortion about 2 feet.

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      • #4
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        Measured impedance

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        • #5
          The FR does tip up a bit at the top. This can be flattened by adding an extra ohm of series resistance on the tweeter if desired. I was happy to see the dip in the sim and 1m measurement flattens out a fair amount at listening distance.

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          • #6
            Here is the parts list and schematic. As far as parts go, I came in at under $300/pr (not including wiring, polyester, or foam sheets) even specing all poly caps. You would be fine with NPE caps on the woofer section and probably save over $20, allowing the whole project to be under $300/pr.

            As for resistors, 10w is fine in the tweeter section, but I would parallel two doubled value 10w or use single 20w resistors in the woofer section after running it in xsim, the notch being the biggest heat dumper.

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            Last edited by dynamo; 01-22-2018, 12:53 PM. Reason: changed a word

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            • #7
              Originally posted by dynamo View Post
              [ATTACH=CONFIG]n1361085[/ATTACH]

              Measured impedance
              ​Interesting. Is the box stuffed?
              Brian Steele
              www.diysubwoofers.org

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              • #8
                I took some leftover foam sheet (closed cell under 1/8” thick) and glued it to the interior walls for the heck of it in case it would damp panel resonance and then lined the walls with a relatively loose polyester batting about 1/2” thick from a roll. Walmart or hobby lobby stuff iirc.

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                • #9

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                  • #10
                    Originally posted by dynamo View Post
                    If you don’t mind me asking, what are you seeing in the impedance plot that makes you curious? I’m always looking to learn something new and certainly open to critique and suggestions.
                    ​The minimum impedance between the two impedance peaks below 100 Hz looks a bit higher than expected, which suggests that the box is quite stuffed which is likely reducing the output from the vent (the closer this impedance is to Re, the less damped the resonance at Fb, and the more output from the vent). Of course, if this what you were actually aiming for...
                    Brian Steele
                    www.diysubwoofers.org

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                    • #11

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                      • #12
                        Originally posted by dynamo View Post
                        The walls are lined but it is a straight shot from woofer to port, which is on the rear behind the tweeter.
                        That will affect midrange leakage through the vent, but the vent's efficiency at Fb is a factor of the vent's length and cross-section area, the volume of the box and how much damping there is in the box. With theoretically no damping, the impedance minimum will be equal to Re, the DC resistance of the driver (plus anything added by the x-over, of course).
                        Brian Steele
                        www.diysubwoofers.org

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