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. I have some questions regarding the differences between a center speaker built as WTMW and possibly WTMMW as pictured in post #59 on page 3 of this thread. In post #60 it is stated:

    So, I have a few questions about this.

    First, could the circuits from the WTMW center and the MTMWW right/left crossovers be mixed for a WTMMW center? As in, could the LF (and possibly HF) from the WTMW and/or the MF & HF from the MTMWW be used to at least overcome the suspected lump in the woofer response, or would this just cause other problems?

    Would the benefits of a second midrange speaker be worth the drawbacks of the different positions of the MF/HF speakers, with or without mixing the crossover circuits?

    Lastly, can the box be built with greater length and shallower depth? Due to space considerations, I would like to keep the speakers tightly spaced in the center of the box, without changing the inner M/T box size, while extending the length of the front baffle, cutting down the depth of the box, and possibly using some angles on right and left ends of the back of the box. Assuming the internal volumes don't change much would there be any reasons why I shouldn't do this?

    Thank you very much for your time, not only with these questions but also with the designs themselves. I am just starting my journey into this hobbly and your efforts are greatly appreciated.
     
  2. If you are using any kind of modern AVR with room correction or even basic EQ I'd suggest building the WMTMW center if you are set on that design and using the crossover from the tower MTMWW. I don't think it's worth trying to combine sections from the WTMW center crossover. If you build it and have a mic to take response measurements I can give input on what parts to change if the frequency response is not already usable.

    There may be slight changes in the response from the individual drivers from changing the enclosure design and driver layout in the baffle but things shouldn't be terrible. Obviously I don't know the exact extent of the changes they could be minimal or change the response quite a bit. The second midrange does reduce distortion and compression as each driver only requires 1/4 the power of a single midrange.

    The enclosure could certainly be built wider and shallower if needed, minimal impact to the response and only that of the woofers.
     
  3. Thank you very much for your response. I do have a mic but I am only just learning how to use it, starting with a whole lot of room sweeps and fiddling around with REW and subwoofer settings. I will be moving on to building this center channel once I finish the current subwoofer project. I would like to believe that will be soon but, in the real world, I have limited time for these projects and they always take longer than I think they should. In the meantime, I will probably be reading as much as I can about crossovers, XSim, and whatever sidetracks come along.

    I'll post back here when I am making progress.

    Thanks again, for the project and the input. I really appreciate it.
     
  4. I apologize if this has been asked, but how would these compare to the 1099s?

    My use is 50/50 music which I usually have both cranked up pretty high (reference).
     
  5. Hi,

    Here is a pic of my Nexus Center shaping up. Still very rough, but looking forward to hear it!
     

    Attached Files:

    RSchirtzinger likes this.
  6. How are they for HT application people who have built them? Considering MTMWW fronts WTMW center MTM Rears and TM rear backs. Listen at reference on AVR.
     
  7. Reference will be pushing it with these on AVR power unless you have a small room.

    Reference level requires that each speaker be capable of producing 105dB peaks at the MLP. With AVR power (lets me be conservative and say 100w/channel at 8 ohms) the MTMWW towers will do 109dB at 1m. With the loss of SPL due to distance you can only get to ~5-7 feet away before they will no longer hit that 105dB peak with 100w input. What will likely happen at further distances is the dynamics in the track will end up being clipped by the amplifier when trying to listen at reference level. Even at 200w a channel you can only get ~7.5-10 feet away before they will not longer produce reference level.
     
  8. Hello, Matt.
    First post here, and I have lurked for a while now. I recently purchased the boards for this project from you, and all of the speakers have been received off back order. I am excited to get these cranking!
    That said, back in post 50 you gave an alternative sealed volume for the woofers. I would like to make the towers near the same depth as the center channel. What would be the detriment of doing this? I am crossing over to a pair of 15" HFs running in stereo as well. Would this make them a "mid bass" punch type of set up- essentially a 4 way?
    Thanks for any advice.
     
  9. You can make the tower enclosures sealed but you do give up quite a bit of output and extension at the low frequencies.

    Alternatively you could leave them ported just shrink the depth of the enclosure and the port by ~2.5-3". This will reduce extension but push the response to be a little more elevated in the midbass/kick drum range.
     
  10. I like that idea. I really didn't want to have to go sealed, but had a little bit of a constraint.
    Thanks much for your quick response!
     
  11. Matt,

    I will build 2 new Nexus TM, but I want to use passive radiators.

    Do you think using only 1 Dayton DS135-PR per speaker is enough?
    https://www.parts-express.com/pedocs/specs/295-495--dayton-audio-ds135-pr-spec-sheet.pdf

    PR's xmax is not double of driver per se, but it's almost there. I am thinking an internal net volume of 4 to 5 liters.
     
  12. That enclosure volume works well with the single PR without needing extra mass.
    You are however limited to about 20w if used fullrange before hitting the xmax on the passive radiator, though if used with a high pass of 60hz it's not an issue until you get above 70w input (and only around 50hz).
     
  13. Hi Matt,
    I'm looking forward to build this speaker.
    There are few questions.

    1. Can I place the port at front at the same height from the floor?
    2. Can the cabinet be tried with curved walls, if possible?

    Thanks..
     
  14. Yes to both. The port can be placed on the front or the back without issue. No trouble from curved sides either as long as you keep the baffle width close to its original size.
     
    Thirumal Kumaran likes this.
  15. Hi Matt,
    Excited to build these as my first DIY LCR build, not my first build, but will be the biggest and most complicated. I will be building these as LCR towers in the WMTMW configuration with the cabinet and port shrunk a bit in depth/length as you mentioned above, ports would be to the front. My set up will have these mounted behind an AT screen in my baffle wall which is 20" off the main wall. Not sure how these would work as an "in wall" speaker so to speak with wood/gyp wall finishing out around them? Do you feel it would mess with the baffle step?

    Any tips for the build or for this arrangement would be most appreciated,

    Thanks,
     
  16. It will mess with the baffle step a little bit yes, but if you are using these for a home theater and will be using some kind of room correction/auto EQ in the AVR/processor it will help tame any abnormalities created by that kind of installation.
     
  17. Yup dedicated theater and running Anthem ARC so I will run with it.

    Thanks again,
     

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