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  • Mercury

    This project came about when the Dayton shielded RS line was replaced with unshielded models. People started asking for shielded RS150's in the classifieds, so I sold mine from an RS150-Seas H1212 project I had built in 2005. Now, I had a pair of Dayton 0.25 cu. ft. cabinets that needed to be populated... Among the drivers on hand were the HiVi M5n, which models very well in a 0.25 cu. ft. vented enclosure (the vents used for the RS150 actually looked about perfect), and the Vifa BC25SC06-04. The Vifas were only $11 at the time and among the best value tweeters out there. There still pretty tough to beat at their current price. I had a spare pair of baffles for the cabinets - so the project was good to go. Since these were going to my oldest son - who had given himself the nickname "Mercury" (presumably for his speed rather than his toxicity) the project had a ready-made name.

    Crossover:

    This project presented several challenges. The M5n is a highly functional, attractive and affordable driver, but as a metal cone driver has breakup that needs to be dealt with and has a rather high inductance that requires a bigger woofer inductor than one would expect for a 5" driver. The BC25SC06-04 has a very high sensitivity and requires a LOT of padding to match up with a single M5n. When padding that much, keeping the shape of the tweeter response under control is not trivial.

    I tried several versions of a standard parallel crossover and came up with one that did what I wanted, but it took 11 components. For a budget 2-way, I was hoping for something simpler. About 5 years ago I had good luck with a second order series crossover on another project using a 5" woofer and a Vifa XT tweeter, so I thought I would try a similar approach here. The outcome is a second order series crossover plus a big 12.5 ohm padding resistor and a zobel on the tweeter - and a bottomless LC notch filter on the woofer to suppress the breakup. The component count went from 11 to 9, which is a little more than I would prefer, but I couldn't really find anything else to take out.

    The resulting frequency response is +/- 1.5 dB on axis through the midrange up to 15 kHz. The crossover point is 2.4 kHz with 4th order LR acoustic slopes on both woofer and tweeter. Due to the slight horn loading of the tweeter, the acoustic centers of the drivers line up closely, allowing a nice 25 dB reverse null without requiring asymmetric slopes.

    Enclosure:

    The 0.25 cu. ft. PE enclosure is tuned to approximately 52 Hz by a 1.5" diameter by 6" long port. I used the 1.5" by 4" flared port available at PE with a high tech 2" extension formed by a toilet paper roll and some duct tape. The combination of the duct tape and thin cardboard TP roll provides excellent damping characteristics to work against any port resonances. ;)
    The drivers are centered along the vertical axis of the baffle. The center of the tweeter is 3" down from the top edge of the baffle. The center of the woofer is 8" down from the top of the baffle. The port is in the rear of the cabinet directly behind the tweeter.

    Impressions:

    After building these about a year ago, I read Paul Carmody's writeup on the Swope HT project. Since those are already out there using the M5n and a small format tweeter, I really didn't see a compelling reason to post this design. A few months ago, I got to hear the Swope MT head to head against the Mercury when a fellow speaker geek brought a pair over. We had trouble telling which was playing in AB comparisons (no, not blind or double-blind testing...) except when there was significant bass content, in which case the ported Mercury had the edge. We also thought we heard a little more upper midrange detail with the Mercury, but any difference was very, very subtle. Recently, there has been interest in a Swope MT with better bass response, which is a need that this project fills. There is a slightly lower driver cost and slightly higher crossover cost - so I think the net outcome will be very nearly a wash. Drivers and crossover for a pair come in at $155 for the Mercury.

    For HT use, the Swope might integrate better with a sub and will be simpler - while for use as a compact stereo speaker, the Mercury's bass extension will be welcome.
    Attached Files
    Keep an open mind, but don't let your brain fall out.

    Argon | Helium | Lithium | LithMTM | Hafnium
    Mercury | Matrix | Shrubbery

  • #2
    Re: Mercury

    That certainly looks like a good built. Do you have any pictures of the final product?

    Comment


    • #3
      Re: Mercury

      I can get some posted up. "Mercury" is catching some z's, so ETA is tomorrow at the earliest.
      Keep an open mind, but don't let your brain fall out.

      Argon | Helium | Lithium | LithMTM | Hafnium
      Mercury | Matrix | Shrubbery

      Comment


      • #4
        Re: Mercury

        You don't see too many series XO designs around here, but yours sims up fantastically. Really looks awesome Scott. I bet this would get a lot of interest in a full-fledged build thread. If I wasn't up to my ears in other projects, this would be a most definite consideration.
        Bryan K.

        Midwest Audio Club

        Speedster | Sub Attachť | The Wildeman | Sean's NLA Towers | CO‹GAR, COUGAR II and CO‹GAR JR | Triton | Lithium | J-Boom | Trym MLTL | Docere MLTL

        Comment


        • #5
          Re: Mercury

          Looks solid! I went parallel with the M5N and the TB 25-1414 tweeter and used quite a few more parts. Sadly, the tweeter is NLA.
          Nicely done!
          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

          Comment


          • #6
            Re: Mercury

            Originally posted by Wolf View Post
            Looks solid! I went parallel with the M5N and the TB 25-1414 tweeter and used quite a few more parts. Sadly, the tweeter is NLA.
            Nicely done!
            Wolf
            Wolf,

            I remember your Mn14 project from its appearance in Iowa. It was the first time I had heard anything from the HiVi M series - and I was impressed.

            That certainly looks like a good built. Do you have any pictures of the final product?
            See the attachment. This is the pair flanking the mighty Sansui 9090.

            You don't see too many series XO designs around here, but yours sims up fantastically. Really looks awesome Scott. I bet this would get a lot of interest in a full-fledged build thread. If I wasn't up to my ears in other projects, this would be a most definite consideration.
            It not only simmed well, but actually measured accordingly (see attachment). That was taken at 1 meter in a very sub optimal location in my basement. Praxis flex windowing at least gives some idea what is going on in the lower midrange - no nasty surprises.
            Attached Files
            Keep an open mind, but don't let your brain fall out.

            Argon | Helium | Lithium | LithMTM | Hafnium
            Mercury | Matrix | Shrubbery

            Comment


            • #7
              Re: Mercury

              Sweeeeet Sansui :D
              Bryan K.

              Midwest Audio Club

              Speedster | Sub Attachť | The Wildeman | Sean's NLA Towers | CO‹GAR, COUGAR II and CO‹GAR JR | Triton | Lithium | J-Boom | Trym MLTL | Docere MLTL

              Comment

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