Announcement

Collapse
No announcement yet.

Helium - a true micromonitor

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

  • scottsehlin
    replied
    It really depends on the receiver. Some can take the lower impedance just fine, and some will go into protect at higher levels. The Helium's impedance curve isn't as bad as many "4 ohm" speakers and I haven't really heard of anyone having an issue with their receiver driving these.

    The 8 ohm version is an option, but the design was based on a simulation, so I haven't really heard them. When I did the soundbar project, I came up with a slightly different crossover.

    Designer: Scott Sehlin Project Category: Home Theater Project Level: Intermediate Project Time: 8-20 Hours Project Cost: $100 – $500 Project Description: The Helium Soundbar is a DIY soundbar…

    Leave a comment:


  • silverneedles
    replied
    if i want to use 5-6 of these as surround on an '8ohm' receiver "100wpc"... should i make the 8ohm version ?

    Leave a comment:


  • Chris Roemer
    replied
    #257-024 would be ideal.

    Leave a comment:


  • silverneedles
    replied
    PE doesnt have this 0.20mH 22gauge inductor... what can i use instead ?

    Leave a comment:


  • Navy Guy
    replied
    Got a chance to hear these at InDIYana. They sound much bigger than their size suggests. These are a great choice for anyone looking to build a small speaker.

    Leave a comment:


  • Chris Roemer
    replied
    The Helium DOES have a Zobel on it, kinda (well, a shunt RC anyhow). They only control a driver's Z-climb above Z-min.
    They don't affect a driver's Fs peak, which (in this vented box) is actually a double peak near 40 and again at 120Hz.
    Near 70 is close to the box's Fb, and where the cone moves the least. Doubtful that THAT's your problem.
    Even the peak near 40 (which is more likely your issue) isn't touched by a 500uF cap.

    You'd have to drop it down to around 80uF to net -6dB @ 40Hz, and that really screws up the rest of the FR, losing almost -15dB @ 70Hz, and about -4dB around 200.
    A passive filter in the XO net is not really viable here.
    I've got to wonder if overexcursion is YOUR problem though. Are you sure everything's sealed well? Did you possibly warp the woofer frame? Is your vent maybe chuffing? Is your port's inside end right behind the ND91?

    Leave a comment:


  • joeybutts
    replied
    Ugh... beautiful concept. Can't wait to see it

    Leave a comment:


  • jwjarch
    replied
    Thanks Joey. No port noise either. Although I couldn't turn them up too far with the kid asleep. Haha.

    I'm thinking white lacquer with the walnut baffles will look clean, modern and have a high WAF. I just need it to warm up a little so the paint will cure.

    Leave a comment:


  • joeybutts
    replied
    Really simple yet effective port integration. How about a finish? Whatcha thinking?

    Leave a comment:


  • jwjarch
    replied
    Got back on track with the Heliums over the last week or so after getting my chip amp up and running. I got one assembled for testing tonight. It took some work but I got my oversized XO to fit really well. After playing a few Marian Hill songs through the one, all I can say is this is the best speaker I've ever heard for its size. I wanted to keep finding different tracks to play. I brought it in from the garage to audition for my wife and she said, "Wow, that sounds AMAZING!" WAF earned! I think the centered tweeter is a working well as far as I can tell. I'll have to get to work on the walnut baffles and start the finish on the cabs. Thanks again Scott!

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by CZ Eddie View Post
    All I have is just the aptX Bluetooth Amplifier I installed, which is rated for 50W x 2 @ 4 ohms and is currently taking the stereo Bluetooth signal and summing it to one channel (mod done by the manufacturer). I'd guess it's something like 100W+ to the crossover.
    I tried both low gain and high gain Bluetooth settings and have same issue with both.

    The speaker gets fairly loud.
    But bass sounds bad at high volumes.
    Lots of distortion/breakup/etc below maybe 100hz, I'm not sure.

    What filter/capacitor inline with the ND91-4 would be recommended to remove bass below maybe 80hz?
    I am using the suggested internal volume and the port is tuned as suggested.
    Normally, a 500 uf NPE cap in line with the driver would create a 1st order high pass at 60 Hz. But the ND91-4's impedance spikes at 74 Hz so it may not be well behaved w/o a zobel on the driver.

    What make and model amp are you using? It is probably possible to create a 1st order HP on the amp's inputs (PLXXO).

    Leave a comment:


  • CZ Eddie
    replied
    I never got around to posting up my DIY build. Mostly because while it's completed, I do have an issue.
    First, I have no A/V receiver to power my build, so it's untested in that regard.
    All I have is just the aptX Bluetooth Amplifier I installed, which is rated for 50W x 2 @ 4 ohms and is currently taking the stereo Bluetooth signal and summing it to one channel (mod done by the manufacturer). I'd guess it's something like 100W+ to the crossover.
    I tried both low gain and high gain Bluetooth settings and have same issue with both.

    The speaker gets fairly loud.
    But bass sounds bad at high volumes.
    Lots of distortion/breakup/etc below maybe 100hz, I'm not sure.

    What filter/capacitor inline with the ND91-4 would be recommended to remove bass below maybe 80hz?

    I am using the suggested internal volume and the port is tuned as suggested.

    Finished product gif:



    Cutting the wood discs to build the enclosure.



    Ghost eating a throwaway wood disc.



    Clamping & gluing the cutout discs together.



    Four different trial enclosures.
    The one on the far left is the final and made from real cherry wood (see my original post here at labs).



    Speakers wired up without any crossover or extra wires showing yet.



    Interior view showing speakers, crossover and that white tube is the vent.



    A look without the vent installed.



    Bottom/removable plate with power & etc. wiring.

    Leave a comment:


  • scottsehlin
    replied
    Your port dimensions sound right as a best guess for a equivalent tuning. The way I think about the close wall effect is similar to how Chris describes the beveled end. The effective port length gets longer because one of the sides of it extends along the close wall.

    Leave a comment:


  • Chris Roemer
    replied
    For your "beveled" end on the internal end of the port only, port - the effective length (not accounting for any effects of being next to the internal walls) is the ave. of the long side and the short side of the bevel cut (so . . . same as the "average" port length).

    Leave a comment:


  • jwjarch
    replied
    Thanks for the input Scott. I'm happy to be the guinea pig for the center tweeter. This project has been a lot of fun so far. I'll probably mock up the tweeter using the MDF baffle in case I need to make any adjustments. I wouldn't want to invest too much time in the walnut baffle and have to re-do it.

    So here's where am at then (see attached CAD). I redesigned based on the feedback from you guys. I have the port exit at the bottom rear of the cabinet now. Hopefully this helps with port leakage, not that it seemed to be an issue before. I increased the angle of the cut on the interior port end to 45 degrees to allow a clearer path for air movement. This design gives me a port length of 6-3/8" measured on the port centerline, and 6-3/4" on the edge of the longest leg. Scott, does that equate to the dimensions you were referencing in your last post? I see what you're saying about the sidewall lowering the tuning a bit. It's effectively acting a little more similar to a slot port design, right?

    Also made some headway on assembling/testing my components last night. I sketched up the XO schematic so I could understand it a bit better before soldering. I soldered one XO together and hooked it up to my TK2050 amp (simultaneous project that will be used to drive the Heliums) Please excise the quick and dirty soldering. I'm planning to clean things up a bit once I get closer to assembly in the box. I also went with Solen caps, PE's new perfect layer air core inductors, and larger than necessary resistors. Overkill I know. What can I say, I got excited while I was sourcing components for my first real speaker build. Anyway, let me know if you see any big issues with my XO's (other than fitting in the box. I have a plan, I promise! ) I'm pretty happy with my first attempt at building one.

    So first impressions... I had to put my ear right up to the ND16, then the ND91 to make sure they were both working! What a great XO design, Scott! They sound so integrated, clear, and clean right now. But I really can't wait to get them in the box to fill out the "low" frequency sound.

    Leave a comment:

Working...
X