Project NEXUS... A timbre matched family of Hi-Fi/HT speakers

Discussion in 'DIY Speakers and Subwoofers' started by Matt Grant, Feb 10, 2014.

  1. Does that mean kits will be made available through DIYSG?
  2. We discussed adding them but it hasn't moved forward beyond that.

    In the mean time I have added the new crossover info for all the designs as well as the cabinet info. I still have to gather measurements and add those but all the info needed to build the updated designs should now be available.

    I also have PCB's designed for these (one for the TM/MTM design and another for the Center/tower designs) which I can likely get a small number of them made up. If anyone is interested in those let me know.
    LuisV likes this.
  3. Hello, I saw your video on youtube and was verry impressed with the result ;)
    i want to build those MTMWW speakers (with the WTMW center) but i have a few questions...

    Do you put some damping material inside the medium chamber?

    Also, where i live we have the metric system... and 3/4" would be 19mm... but the wood i can buy would be only 18mm thick (0.7")... Do you think i have to change the cutting dimensions or it's just the same thickness and i'm being paranoid?

    Is it a big deal if i build them with plywood instead of MDF? (I don't think so but i prefer to ask)

    Can i screw (in addition of the glue) the wood together or is it a bad idea?

    Can I put the port on the front of the speaker, under the woofers? (I will have to put them close to a wall so the port would not breathe correctly if it's in the back...)

    Also, (and i'm sorry to ask that, but that's my "only" real point of comparison, and kinda a "love at first ear"...) How would you compare them with b&w 683's? (if you know them of course)

    Thank you for the answers :)
  4. The midrange chamber is meant to be filled with some kind of damping material leaving just enough room for the drivers. I used recycled denim insulation but fiberglass, polyfill or acoustic foam will work fine as well. The woofer section of the cabinet should have damping material lining the walls, but I also have the top portion of that cabinet behind the midrange chamber lightly filled. Make sure to leave the area around the internal port flare empty as not to restrict airflow through the port.

    Using plywood is fine as are 18mm thick panels. The external dimensions do not need to change neither do the internal dimensions of the midrange chamber, 3" deep x 14.75" high, though it could be rounded to 75mm deep x 377mm high if that's easier. In fact the cabinet could be made 250mm wide x 1170mm high x 380mm deep to round things out (height where back angle begins would be 775mm high, top changed to 250mm back).

    Base plate can be 300mm wide x 430mm deep. Mine was made from a layer of 1/2 and 3/4" MDF sandwiched together with a 1/2" chamfer added. If you have 12mm and 18mm that works too. But feel free to change it up if you like, it's just there to widen the feet and add stability.

    Drivers center positions down from the top of cabinet would be:

    Port center would be 155mm up from the bottom and it can be placed on the front if desired.

    Screws are ok to use during assembly of the cabinet.

    I haven't heard the 683's. The only B&W's I have experience with are the Matrix 804's and I much prefer these to the 804's. The highs were nice on those but the midrange sounded too laid back almost suppressed. The bass on the Nexus feels more impactful and in controlled while I felt it was on the muddy/boomy side with the 804's especially when they were turned up.
  5. Thanks a lot for your answer, i don't even have to do the maths between inches and milimetters lol
    your comparison with the 804 is encouraging as i reproach them the same things ;)
    Just need some time to get all the parts, and i'll try build them the best i can ;)
  6. #81 Matt Grant, Feb 12, 2018
    Last edited: Feb 12, 2018
    I ended up getting a few PCB's made for the new crossovers, if anyone is interested in those let me know.

    They are designed so the you can use either Poly or NPE caps on the midrange. The woofer on the Center/Tower board only supports NPE but I don't really recommend poly capacitors on that as they get to be pretty big/expensive when you get to that size and you won't notice a difference for just bass anyway.

    I don't have too many of these PCBs but if the demand is there I can get more made:
  7. Matt. ive been thinking about these MTMWW sepakers for a long long time. now that ive decided to order the items. ive found that there is no sd215 in stock until august in Parts express. im from argentina. so i should buy everything in one place if possible. is there any other speaker that i could use without modding ? or any other place to buy?
  8. Hi Gaston, It looks like Parts Express will have the SD215 in stock on May 8th, not August 5th. If you can wait a month I'd use those drivers as I haven't tested another woofer that would be a suitable drop in replacement.
  9. Opps. it was just a translation mistake. down here we write Day, Month and Year. i forgot you use MONTH day and year.
    Thanks for the reply. ill wait and come back when i get the items.
  10. Are There any boards left?
    I'm interested in 3 tower/center and 2 tm/mtm boards.
  11. Just got my tower crossovers done.IMAG0178~01.jpg
  12. What is the port length for the TM?
  13. Port for the TM is left full length when using the 1-5/8" flared port 260-474 from parts express.

    Also for future reference I noticed a had made a mistake on the instructions I gave to NDJ for the MTMWW crossover, the placement of the 12uF and 0.68uF capacitors in the above photo should be reversed.
  14. Nexus center crossover

    The description says: uses two of the Dayton SD215A-88 subwoofer drivers in series as the low end.

    Am I reading the schematic wrong, but that looks parallel?
  15. #90 Matt Grant, Jul 5, 2018
    Last edited: Jul 5, 2018
    Sorry it's a bit confusing I'll need to clarify the post. The SD215A-88 are dual voice coil woofers so the voice coils should be wired in series and the two drivers then wired in parallel to the crossover output.

    Technically you could also wire the voice coils in parallel and wire the woofers in series for the same result.
  16. In the crossover for the center, the 0.51 ohm resistor is for R1?
  17. It's listed as R1 on the schematic but on the PCB it is placed in the LF R1 spot.
    NDJ likes this.
  18. Is there a BSC change when making a center a WTMW, is there a difference between WTMW and TMWW
  19. Technically the latest crossover has only been tested on the WTMW center configuration. The same crossover should work for a vertical WTMW or TMWW design but the frequency response will be impacted slightly by the baffle diffraction effects from different driver placement. The WTMW design should be closer to the horizontal center channel design in that regard.

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