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Helium - a true micromonitor

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  • Re: Helium - a true micromonitor

    I think I want to build these. Who would be willing to help me out picking the xover parts (I am a total newbie). For example, does this work? http://www.parts-express.com/10-mh-2...ctor--269-2266

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    • Re: Helium - a true micromonitor

      Originally posted by Jeff F. View Post
      The Dayton ND91-4 is the designs original mid and is 4ohms. I think he must be referring to a new version with the ND91-8 an 8ohm mid.
      Correct: Dayton Audio ND91-8 3-1/2" Aluminum Cone Full-Range Driver 8 Ohm.
      I wanted to make a 8 ohm version for amps that can only do 8 ohms.
      All the xover parts should arrive today and with a little sanding and fitting, should be ready to put this little guy together.
      I'll do a write up and some pictures when I get them done and let you know how it sounds.
      Getting better!:D

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      • Re: Helium - a true micromonitor

        Originally posted by Atsaubrey View Post
        I think I want to build these. Who would be willing to help me out picking the xover parts (I am a total newbie). For example, does this work? http://www.parts-express.com/10-mh-2...ctor--269-2266
        That will be great. These guys won't be handle a lot of power, so that is a good one for that small box.
        Getting better!:D

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        • Re: Helium - a true micromonitor

          Will the baffle layout be the same for the new design? My only issue with the original is the extreme (to me) offset of the tweeter and the port on the front right next to it. I don't make grills (I suck at making them look nice) and my wife has flat out said "No" to this design with this layout.

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          • Re: Helium - a true micromonitor

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            Is this all good to go? I can't find a 14ohm resistor anywhere. anyone point me in the right direction?

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            • Re: Helium - a true micromonitor

              Originally posted by brianbunge View Post
              Will the baffle layout be the same for the new design? My only issue with the original is the extreme (to me) offset of the tweeter and the port on the front right next to it. I don't make grills (I suck at making them look nice) and my wife has flat out said "No" to this design with this layout.
              This design was planned for the same baffle layout. The real purpose of the arrangement was to find a way to get a port to fit somewhere. Rear porting doesn't work very well, because the port needs to go most of the way across the cabinet, then down (or up). If I started from the back, I couldn't come up with a routing that missed the woofer.

              If one did a slot port coming from the bottom front, then the tweeter could be centered horizontally (which might require another look at the crossover for at least the simulated effect due to change in baffle diffraction). If I recall correctly, the slot would have to be very thin (like 1/8") in order to be a workable length.
              Keep an open mind, but don't let your brain fall out.

              Sehlin Sound Solutions

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              • Re: Helium - a true micromonitor

                Scott,

                Thanks for the reply. Your explanation of why you put the port on the front makes sense. I hadn't thought about a slot port. I've never totally understood how to figure the length of a slot port as it always seems that they are shorter than a round port for the same cross-section, IIRC.

                I've often wondered just how much difference offsetting a tweeter or midrange made in real world use. I suspect room interaction would have an overall greater affect but I don't really have any data to back up that supposition. Aesthetically I prefer the drivers centered on the baffle, but I understand that speaker design (or any other kind of design) is about trade-offs and which ones the designer is willing to live with and which he/she is not.

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                • Re: Helium - a true micromonitor

                  Originally posted by Atsaubrey View Post
                  [ATTACH=CONFIG]63348[/ATTACH]

                  Is this all good to go? I can't find a 14ohm resistor anywhere. anyone point me in the right direction?
                  https://www.madisoundspeakerstore.co...ound-resistor/ or two of these http://www.parts-express.com/dayton-...esistor--004-7

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                  • Re: Helium - a true micromonitor

                    Given the same x-sectional area, a slot should be the same length as a round port to tune the same size box to the same freq. WinISD ( www.linearteam.org ) can model them for you.

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                    • Re: Helium - a true micromonitor

                      Thanks, Chris. I thought I'd read years ago that when you're using one side of the box as part of the port that the effective length was shorter for the same tuning vs. a round port. I'm sure in this case it's not exactly critical though. I'll have to see if I have a way to modify the cabinets for a slot. I don't have the tools or space that I did 4-5 years ago.

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                      • Re: Helium - a true micromonitor

                        Originally posted by brianbunge View Post
                        Thanks, Chris. I thought I'd read years ago that when you're using one side of the box as part of the port that the effective length was shorter for the same tuning vs. a round port. I'm sure in this case it's not exactly critical though. I'll have to see if I have a way to modify the cabinets for a slot. I don't have the tools or space that I did 4-5 years ago.
                        I have read that also, and it makes sense. I am not sure what the correction factor is, but I am sure that a number of people have reported lower port tunings for slotted ports versus the expected tuning based on calculations assuming round ports with the same cross sectional area and length. I have also read that it is possible to get a lower tuning than calculated when the aspect ratio of the port is greater than a certain threshold, but again haven't seen any calculation of or basis for a specific correction factor.
                        Keep an open mind, but don't let your brain fall out.

                        Sehlin Sound Solutions

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                        • Re: Helium - a true micromonitor

                          Well at least I know that I'm not going crazy...this time!

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                          • Re: Helium - a true micromonitor

                            I need some newbie help reading the crossover schematic if someone has the time.

                            I'm not sure I understand the polarity symbols on speaker crossover.

                            Could someone put Pos Gnd symbols on the schematic so I'm sure I'm putting them together right.

                            Embarrassed to ask but I'm just not sure. I have searched and read but still haven't got a handle on it.

                            Thanks for your help

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                            • Re: Helium - a true micromonitor

                              You don't see it, but there's a (implied) "+" symbol in the top left corner.
                              All the ground symbols (look like upside-down Xmas trees) are "-" and can all connect together, AND to your cab's negative (black maybe?) term. (The red term goes to that implied "+" on your XO board.)

                              So . . . this means that both drivers are connected normally (their tops are "+" - from the last XO component, w/their "-" terms running to that "common" gnd.) as well.

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                              • Re: Helium - a true micromonitor

                                Thanks
                                So the circle with the S in the center on the left is ??
                                Is that both the + and - going the the terminal cup ?

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