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Jims 3 way speaker build

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  • Originally posted by Chris Roemer View Post
    3-ways are often plagued more with low-impedance than 2-ways.
    Are they all 4ohm drivers? (From what I can tell (YOUR .ZMAs) they're all 8ohm? A "typical" 8ohm 3-way might "min out" in the 5-6ohm range.)<woofer8, Mid 8 Twt 6 ohm>
    Do you have a lot of overlap (caused by shallow slopes, AND a narrow mid band-pass - 3 octaves (or more) is best)? (<XO as is is 400hz and 3800hz>
    It SEEMS (to me) that you might get a higher Z using a bandpass (mid) topology using a series cap, THEN your series coil, and THEN the shunts (to gnd)...
    Not sure why this is, but I do think it's true.

    Also, don't you need any attenuation on the tweet and mid? Series resistance will help hold your Z up (aren't you using any baffle-step?).
    I will massage this, again it was quick throw together. Also I have rethought the lower XO point and in my designs I try to XO atthe baffle step frequency in this case 285 hz.

    Comment


    • Post your F/Z files (6) and we'll have a look.

      Comment


      • You can try shifting around your crossover points and see how it changes. I am surprised you don't need any padding in your mid and tweeter. Like said earlier a little series resistance will help you out.

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        • That tweeter has no ferrofluid, so what you have may not suppress the Fs of the tweeter enough to keep it from buzzing.
          Agreed that at least some resistance will be required.
          Wolf
          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
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          Comment


          • I traced your 6 F/Z curves (so no phase data)...
            Your tweeter seems so quiet (compared to the mid and woofer) that I couldn't afford to attenuate it.
            Anyhoo, here're MY "1st shot" filters:
            2nd order HP: 5.6uF series cap, 0.36 shunt coil (to ground) - this is EXACTLY what you tried !
            SIMILAR bandpass (slightly different topology - and adding an L-pad, all components change except one):
            47uF series cap followed by a 0.60mH series coil, 2 shunts (to gnd), a 2.0mH coil and a 12uF cap(same), then an L-pad: SR=6ohms / PR=8.
            YOUR LP: 7.0mH series coil (low DCR - iron core), and a 68uF shunt cap.

            Impedance mins near 4.5 ohms near 500 and again at 2000 Hz. (Many "8-ohm" amps wouldn't be unhappy with this.)

            Comment


            • Chris, Wolf, Johnny et al, I will redo all the frd curves. I also redid the zma for the woofer only and I still have to 2 small peaks. I am beginning to think those are the interior braces. I'll post later. Again thanks for your assistance.

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              • OK so I redid the woofer zma. I also redid the frd and imp at a higher loudness as before it was very low. Note that the 2 small peaks at 150/675 still exist after I added more padding to the cabinet. As I mentioned before I believe it is the internal braces if that makes sense. I will do a Sim with these and post results. As usual throw darts lol.
                Attached Files

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                • Adding tweeter snapshots as there is a 5 file limit on uploads. Also where is the "Invert" button in omnimic?? I had to reverse the speaker lead polarity.
                  Attached Files

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                  • I would take a close mic of the woofer, and use it. Doing so will eliminate the room for the most part. Speaking of parts, did you order any? The PE return policy is good, if you have something that you really don't want to keep.

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                    • jimbones
                      jimbones commented
                      Editing a comment
                      no i have lots of XO parts that I keep on hand. I will post some questions below

                  • OK so now that I have had a chance to look at these I have questions:
                    1) the port resonant fr is <20hz. I am using an 11 inch x 4 inch dia port which should put me around 34 hz. Am I doing this right or are my calculations off?
                    2) I dont have an invert polarity option in the "Main Math" drop down menu as described in the Omnimic manual For now I am swapping the speaker leads. Can some one point out where this is?
                    3) The frd files are hosed. when I go to use the im Win PCD or XSim some are OK and Some are very low in SPL. (Note I kept the volume and mic position unchanged. I also measured 2.7vac at the driver just to make sure I was driving it sufficiently. I can post the actual files for soeone to run and see what I am experiencing. Thanks.

                    Comment


                    • Post your files. Frd and zma for each driver.

                      For the woofer, have you taken nearfield response of both driver and port, combined them and blended them with a far field measurement or are you looking for assistance with that?

                      https://www.audiosciencereview.com/f...tuixcad.21860/
                      Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
                      Refurbs: KLH 2 | Rega Ela Mk1

                      Comment


                      • zma and frd files for mid and tweet
                        Attached Files

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                        • woofer zma and frd, damn I thought I had port and nearfield I'll go back and get those
                          Attached Files

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                          • ok port and woofer nearfield
                            Attached Files

                            Comment


                            • Hi jimbones,

                              Are these gated measurements? They don't appear to be - particularly the woofer and midrange. Usually in a home environment you'd be lucky to get anything beyond 4ms gate time for far field measurements.

                              Are these all definitely on axis for each driver? I.e. you're not measuring the midrange with he mic pointed at tweeter and so on?
                              The tweeter drops -15db from 10K to 20K - the seas datasheet indicates a slight roll off of around 3db is expected so just make sure the measurement is precisely on axis.

                              Also are you running configuration files for your microphone and soundcard? If not - that'll also go a long way to explaining the tweeter roll-off.

                              I definitely would not attempt any crossover development with these files the way they are.
                              Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
                              Refurbs: KLH 2 | Rega Ela Mk1

                              Comment


                              • DeZZar
                                DeZZar commented
                                Editing a comment
                                Just saw the impulse response above. Looks like you are getting reflections just after 3ms. Try gating around 3ms - should make a big difference to what you see. Ideally you want to try and get yourself a little more headroom than this - measure outside with the speaker elevated if you can.

                              • jimbones
                                jimbones commented
                                Editing a comment
                                yes gated at 5ms, 1 m out with mic between mid and tweeter.On axis.Yes mic config file is loaded and running.I can not move these boxes they are heavy and I had back surgery so they are staying put. I'll try gating at 3ms and remeasure
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