Announcement

Collapse
No announcement yet.

NE225W+PM180+ViaWave Design & Build Thread

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Chris Roemer
    replied
    Classy lookin' box !

    Leave a comment:


  • jml
    replied
    Good Evening!

    The grills are coming along, and I'm really pleased with the results. They're all ready to receive a coat of matte black paint, and then they'll be complete. I will be doing the vast majority of my listening with the grills in place, so I plan to take a new set of measurements with them on before finalizing the crossover design.

    Cheers!

    Joe

    Leave a comment:


  • Wolf
    replied
    jml- I feel that there are good points in all 3 of your sims, but I feel that you aren't where you should be yet.
    In the first, you likely have the sum of MT a bit higher than necessary to sum flat, but it's in a better range. resonance of filter parts is likely the cause of the impedance dip.
    In the second, I agree that the tweeter is going to low.
    3rd has good impedance.

    Some thoughts- I think you'll likely find better summations in the 300-500Hz range for woofer to midrange, 2.5-3k for midrange to tweeter, and I'd try and allow the drivers to show you where they want to xover. Don't try and force them to do one thing or another. I know Pete said that the PM midbasses typically use an order higher slope to get one less order rolloff, and to use a damping resistor to complement the cap in the circuit. ie- use a damped 3rd order LP (coil-shunt CR-coil) to yield a 2nd order rolloff.

    Have fun!
    Wolf

    Leave a comment:


  • jonasz
    replied
    Originally posted by r-carpenter View Post

    All depends on how you work the tail. All ribbon tweeters have chamber/foil resonance that falls between 1500hz and 1800hz. It's sort of like Excel Magnesium breakup. Viawave is no exception in this respect.
    This resonance or the luck of attenuation on the part of many designers gives ribbons bad rep BTW. If you notch it out and your main electrical filter brings the tail sufficient enough, I can see 2.2khz safely and clean.
    Thanks Roman.
    Maybe, just maybe, they can be paired with the Excel W15 then but it will probably be a stretch... Sorry for th OT

    Leave a comment:


  • r-carpenter
    replied
    Originally posted by jonasz View Post
    Is the Viawave comfortable with a 2k crossover?
    All depends on how you work the tail. All ribbon tweeters have chamber/foil resonance that falls between 1500hz and 1800hz. It's sort of like Excel Magnesium breakup. Viawave is no exception in this respect.
    This resonance or the luck of attenuation on the part of many designers gives ribbons bad rep BTW. If you notch it out and your main electrical filter brings the tail sufficient enough, I can see 2.2khz safely and clean.

    Leave a comment:


  • jonasz
    replied
    Is the Viawave comfortable with a 2k crossover?

    Leave a comment:


  • jml
    replied
    Chris:

    Thank you for taking the time to provide some feedback! I've taken a pass at incorporating some of the solutions outlined above into a new model.

    Cheers!

    Joe

    Leave a comment:


  • r-carpenter
    replied
    I don't like either one of this x-overs, to be honest.
    The first version shows woofers to be approximately 4 db lower than the rest of the compliment. So the important question is, how did you measure and summed up woofers for the sim? Was baffle step added as well?
    Second x-over allows the tweeter to work in to too low of the range. It's only around 10 db down at 1000hz. Not the best choice for a ribbon or even many domes.
    What I would suggest is to lower the output of the mid by couple of db and rework the filter for the tweeter. Push it to 2800hz or so with your second order and add parallel notch at 1700hz. Play with the shunt resistor on that notch so there's no impedance deep. This way you can get good phase response between mid and the tweeter and stay away from impedance issues.

    Leave a comment:


  • Chris Roemer
    replied
    Most of the time, too low of an impedance (esp. in a 3-way) is caused by too much driver overlap. Try to push your Fcs apart to closer to 300-400 and 3kHz.
    Also, ideally you'd like each crossing driver to be down -6dB (-3dB MINimum) at Fc. Your last two sims both show (phase) trouble with the mid/tweeter cross. Your final attempt (so far) is better, but still can be improved. In your previous version you can tell you've got poor phase alignment by the way your summed response dips below each driver's individual response ("detrimental" summing). Often, to make a meaningful phase shift, you'd generally have to raise or lower the offending filter by an order (the HP on the tweeter, or/(sometimes AND) the LP portion of the mid's BP.

    Also (IMO) most often the mid's impedance can be held up a bit by running the series components together (cap & coil), followed by the shunts (to gnd.). I don't think ALL the sim softwares out there support that topology, but it would be nice if they did.

    Leave a comment:


  • jml
    replied
    Ok, this one is a little better - minimum impedance of 3.5 ohms.

    Leave a comment:


  • jml
    replied
    Alright! The #20 stainless mesh is on the way for the grill inserts, so while I'm waiting for that, it's time to work on the crossover.

    I had some (quiet) time to spend taking measurements, and they seem to have turned out OK, with the exception of a bump around 60hz from ambient noise - neighbor mowing the lawn, fridge, laptop fan - not sure.

    I spent about an hour playing around in Xsim, and one problem persisted in nearly every permutation I tried - extremely low impedance in the midrange. I'm sure the experts on this forum will take one look and see what I'm doing wrong, but it has escaped me, thus far.

    Let me know your thoughts!

    Best regards,

    Joe

    Leave a comment:


  • 6thplanet
    replied
    Maybe sandwich the white grill cloth between said steel rings? ...after the steel rings are sent out to be copper plated, of course... 😎

    Leave a comment:


  • jml
    replied
    Good Evening!

    I finally have another update on this project. I wasn't able to get a perfect cut of the perforated .03" steel for the grills, so I had some 1/16" steel rings cut, which will act as a frame for the grills. I am going to try sandwiching some steel mesh between two rings for each driver, then paint it all matte black and hold it in place with magnets. Attached are a few pictures for "proof of concept". I'm optimistic this solution will be functional, achievable, and aesthetically pleasing.

    Also, I've now got my DATS, OmniMic, and Xsim up and running. I've had time to take some measurements and play around in Xsim with the results, but I plan to take some time to ensure I know how to get good measurements before I invest too much time in Xsim.

    Cheers!

    Joe

    Leave a comment:


  • bjaurelio
    replied
    This is a really nice looking project. I think you're safest using snips rather than a power tool to cut on your lines and have more control. As you mention, edge trim can cover any imperfections.

    Question about the NE225W drivers. How did yours measure compared to specs? I am considering a build with these drivers and wondering how close I can get using published specs for purposes of comparing drivers. Obviously, once a driver is chosen, I will have to measure my drivers given normal variances.

    Leave a comment:


  • jml
    replied
    Good Morning!

    Well I've spent a lot of time staring at the speakers trying to decide on how to proceed wit the grills. The next option I'm going to try is doing 3 individual round grills for the 2 woofers and the mid. I figure there is no grill needed on the tweeter given that it's both recessed in the waveguide and covered by a screen. i think this will be the best option to keep with the aesthetic theme of the project - kind of a minimalist modern look, while not covering any of the end grain. One of the things that bothered me about the previous grill design was that from the listening position you couldn't see any of the wood.

    My plan is to use .03' perforated steel for the grills sprayed with the same matte black as the feet. I plan to cover the outer edge with a very small black rubber edge trim, and then magnetically attach to the driver mounting screws.

    What do you guys think is the easiest way to cut the perforated steel into a circle? I suppose a purpose built die and an industrial punch press or CNC plasma cutter would be the best option, but the budget doesn't allow for such luxuries. For now, I'm going to attempt to mark the circle with a marker and then cut it out with a snips with the hopes that any minor imperfections will be hidden by the edge trim. I'm thinking this will be easier than building a jig and using a metal cutting blade in the bandsaw or jig saw.

    Cheers!

    Joe

    Leave a comment:

Working...
X