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. Thanks for those charts!

    If anyone is interested, I have made same Sketchup designs for the Nexus WTMW Center, WTMW L&R and the TM On Wall/Atmos. If Matt it's OK with it, I can leave the links here so that anyone can use them and make any modifications if needed.

    I am building my wtmw center (I already contacted you for the PCB) and converting my TM to TM Atmos.OW.JPGwtmw center.JPG
    wtmw lr.JPG

    Attached Files:

  2. Is there a TM Atmos design available?
  3. If you want to make one really compact for atmos use you could build it at the same 7" x 10" baffle size but make it sealed and only 5" deep. This will give ~100hz extension. You could also stick one of these ports in cut to about 5" long, it will have to go in the top/bottom or sides. That will tune it to around 65-70hz and give an f3 around 75hz which should make an 80hz crossover usable.
  4. The Nexus TM shallow design I made is tuned around 65hz (3,9 liters internal volume) and it's (W)178mm x (H) 320mm x (D) 125mm... maybe I can make it sealed and a little shorter, but thought to keep it with a tuning as close as possible to the original design. Do you see and inconvenient with it?
  5. Your design will certainly work well.

    I just figured keeping size to a minimum would be one of the main goals for an atmos speaker which is what I did for the above cabinet recommendation. It's pretty much the smallest cabinet I'd use that woofer in.
  6. Sounds good. Should I be concerned with the BSC mounting them directly to the ceiling?
  7. If you are using some kind or room correction in your AVR it's not worth worrying about as that should help fix any issues that arise there.
  8. If anyone was interested in the PCBs for these I did get more made up for both the MT/MTM and the Center/Tower designs.

    I also had some PCB made up for the Argos and AlTi designs. Once I have some photos and make up instructions for those boards I'll put them up on eBay along with the Nexus PCBs for ease of purchase.
  9. Please let us know when the Argos PCB are available, I'll buy 2. I'm going to see about digging out an old breadboard and prototyping the crossover and wiring it to the speakers.
  10. #160 Matt Grant, Mar 14, 2020
    Last edited: Feb 10, 2021
    Steve Chan likes this.
  11. #161 mga2009, Apr 1, 2020
    Last edited: Apr 2, 2020

    One quick question. In the Nexus Center, the tweeter has a 4ohm resistor. I want to use a better quality resistor there, meaning Mills or Jantzen.

    The problem is that PE, now, does not carry an exact 4ohm for those brands... If i preffer a "hotter" high frequency, better than a more "laid back" sound, should I go with a 3.9ohm or a 4.5ohm?

    Thanks in advance!

    UPDATE: I tried XSIM with the FRD and ZMA files from PE for the ND28F-6 and reproduced the XO only in the tweeter part, and tried changing the resistor value from 4ohm to 3.9ohm and 4.5ohm. It seems that a lower resistor value (3.9ohm) will produce a "hotter" high frequency response. Is this correct?
  12. Yes, that resistor is in series and therefor a lower value will result in more output from the tweeter. That said 3.9 Ohms will be almost indistinguishable from 4 Ohms, something around 3 ohms could be used which would be about 1dB of additional output above 5k. Changing the 4.3uF cap to 4.7uF would extend that to 2k and up.
  13. Hi Matt, I saw earlier in this thread that you said the center channel could be made ported if needed. Would the ported or sealed center be best for a home theater setup?

    Also, I have a garage system that I am currently using Classix IIs with a 12" sealed sub. Would the a ported version of the WTMW center be a good upgrade over the Classix II?

    And thanks for the PCB boards! They worked out great!
  14. I'd use the sealed version for home theater, often there isn't much need for extension below 60hz which it provides sealed as an 80hz crossover is most common.

    I'd like to say the ported WTMW would be an upgrade over the Classix II though I haven't compared them or heard the Classix II betfore so I don't really know how they stack up. Certainly the ported WTMW would give you more bass extension and greater output capability then the Classix II if you are looking for that.
    Dr. Muscle likes this.
  15. I'm looking at using either the mt or mtm to mount to my ceiling as downfiring atmos speakers. I'm going to attach them to existing beams. I'm trying to crossover at 80hz, would there be any advantage to the mtm over the mt in my situation?
  16. For atmos I would use the MT design as it will have better vertical dispersion then the MTM. That said If you only have one row of seating or your ceiling is fairly high you could probably get away with the MTM. The main advantage the MTM has over the MT is its greater sensitivity and output capability, at the expense of the narrower vertical dispersion.
    Mike_j likes this.
  17. #167 Mike_j, Jun 1, 2020
    Last edited: Jun 1, 2020
    I think I'll build the mtm then, I have 10' ceilings in a 20x30 room roughly. I'll probably build in an angle pointed at the listening area, so I can mount them flat on the ceiling and against the beam. I'll try my hand at building the port into the box this go around. I have a rough cut wood ceiling I'd rather not cut into if I don't have to, so this should be perfect. Thanks, Matt!
  18. I'm interested in building a pair of the ported TMWW for my garage system in the large bookshelf size. Does anyone have a mockup on how that would look?
  19. @Matt Grant
    thanks for the crossover pcb's (3 x center/tower WTMW), looking forward to get building.

    I have the option of building a horizontal or vertical for LCR. Would there be much difference in sound between horizontal vs vertical for L&R main speakers?
  20. Generally the left and right are built vertical as it takes up less space and gives better horizontal coverage. It's usually less of an issue with the 3 way design but you can still experience some drop in output at the upper range covered by the woofers when far off axis due to the cancellation between them. When on axis or slightly off axis there would be minimal difference in the sound.
  21. @Matt Grant
    How would you say these compare to the HT8's? I have a smaller home and subwoofers and was going to do a 5.2 speaker system with HT8's for the 5.0 portion. Are the Nexus comparable?
  22. Depends on which Nexus design you are comparing it to but in general the HT-8 will be capable of more output and have better imaging then any of the Nexus designs resulting in better intelligibility.

    The Nexus designs will likely have better bass extension (slightly better for MT or MTM to much better for MTMWW) while the dome tweeter will result in a more open and perhaps detailed sound presentation.

    I'd say the Nexus designs are more suited to music or 50/50 playback while the HT-8's are designed primarily for movie/multichannel playback.
  23. #173 Mike_j, Aug 9, 2020
    Last edited: Aug 10, 2020
    I finished the mtm's but it sounded muffled, I reversed the polarity of the tweeters and it sounded right again. Is this something I did with the crossover? Never mind I reversed polarity of the whole speaker, it was really muffled until I did so.
  24. Reversing the polarity on the tweeter would normally cause a large hole in the frequency response around the crossover. Unless your woofers were also reversed or you originally had the wires mixed it shouldn't sound better reversed vs normal.
  25. I didn't catch the spell check correction before I posted. Somehow I reversed polarity of the whole mtm, not sure what I did, but it works correctly.

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