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refining my crossover (HELP NEEDED)

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  • refining my crossover (HELP NEEDED)

    i need some help with my crossover circuit design such as

    does it look correct with the layout for a two way 3rd order butterworth at

    400hz

    this is for a future build that is to be a set of rear surrounds with this

    config

    a 4ohm input at 300watts
    with 250watts at 2ohm to the lows
    an 50watt at 4ohms to the highs with a L-Pad Attenuation of - 4db with a first order lowpass at 1500hz (it is for smoothing out the highs)
    an a 2nd order highpass at 16hz with a 1.4q

    does this need anything more like a ground or a zobel circuit if an so were

    would it go

    the drivers to be used are as followed

    using two GRS PT6825-8 8" Planar Mid/Tweeter 8 Ohm ( wired to 4ohms )

    an one Dayton Audio RSS265HO-44 10" Reference HO DVC Subwoofer (wired

    to 2ohms)

    an two Dayton Audio RSS265-PR 10" Aluminum Cone Passive Radiator tuned at

    16hz

    https://imgur.com/gallery/iv8DeQu








    Attached Files

  • #2
    Your crossover is confusing. The input to the Mid/ tweet is 18 db/octave followed by all those resistors. Two of the correct value would be fine.
    Then there is L4 ? Looks like it would attenuate the higher frequencies.
    The woofer crossover is 18 db/octave followed by a 12 db/ octave high pass. I can not make any sense of your thought process. Anybody else
    have comments ? Did you make the cabinets, they look very professional !

    Comment


    • #3
      What's with all the resistors? And the 16Hz high pass on the woofers? I can't imagine what L4 is for. I don't see the value in rear surrounds that go below 80Hz, or the need for dual tweeters.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

      Comment


      • #4
        In addition to being completely confused over your crossover, and your use of two tweeters, I don't understand how you intend to orient the baffles. Are you going to stand these cabinets up? If so, the horizontal tweeter placement will result in a very narrow horizontal field and a wider vertical field. Aside from the comb filtering you'll get from dual tweeters. Typically these planar tweeters are stood up so that you get wide vertical dispersion, which I would think would be important in a surround speaker.

        Comment


        • #5
          Agree with above, specifically these:
          • The high pass on the woofer is not needed, that's best left before the amp if you feel you need infrasonic protection. Generally, that's not needed at all.
          • The 10 resistor cascaded L-pad is crazy, 2 resistors of the correct values will do.
          • The orientation of those dual planar tweeters may be a concern, read up on dispersion and comb filtering.
          Last edited by wogg; 05-19-2021, 09:32 AM.
          Electronics engineer, woofer enthusiast, and musician.
          Wogg Music
          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

          Comment


          • AEIOU
            AEIOU commented
            Editing a comment
            I hate it when people say subsonic, more correctly it should be infrasonic.

          • wogg
            wogg commented
            Editing a comment
            Harmless enough... I'll oblige

        • #6
          Are our legs being pulled here?

          Last edited by fpitas; 05-12-2021, 03:55 PM.
          Francis

          Comment


          • #7
            Not that the enormous resistor ladder on the tweeters isn't cool.
            Last edited by fpitas; 05-13-2021, 01:05 PM.
            Francis

            Comment


            • #8
              ...wait....is that a 6,810uf cap on the woofer...

              I'm truly curious as to what design theory lead to the crazy resistor setup and that 16hz high pass....

              I can't really add much more to what everyone else has already said only to say that realistically until you have your own measurements to work with you can't really finalise or tweak a crossover design - it's theoretical at this point.

              However, some design issues to focus on with those dual tweeters first....

              ​​​​​​​

              Comment


              • #9
                ACTUALly ... if you model your filters in a program ...

                getting rid of the (passive) HP on the sub (the 6800uF cap & 14.0mH coil), MOVING the top end rolloff coil (0.40mH) ahead of your "L"(-pad) and tweaking it down to 0.30mH, and using a 3ohm (series) and 3ohm (parallel) resistors for your L-pad, AND just using a single planar ...
                you end up with what looks like +/-3dB up to around 12kHz with an Fc very near 400Hz.

                It can almost assuredly be improved, but it's not awful - however, there is essentially NO baffle-step.
                The worst (most roller-coasterly) is the driver transition between about 250Hz to around 1.3kHz.

                (If your planar section used about a 3.5n(ohm) SR and a 0.5n PR, you'd end up w/about the same level and load as your 10 resistor array - which is about -20dB BTW.)
                Last edited by Chris Roemer; 05-13-2021, 02:00 PM.

                Comment


                • #10
                  Can anyone confirm if there's something weird with the RSS265HO-44 FRD or ZMA files? It looks like the ZMA used is the 2ohm configuration (which I think was also used for the T/S parameters), BUT despite the T/S results and the USPLsensitivity spec from PE both showing [email protected] the FRD (both in the specs PDF and in the FRD file) are closer to [email protected]

                  It kind of looks like PE used the T/S and ZMA files with the woofer measured in parallel 4/4ohm, while the FRD file was measured in series 4+4ohm or maybe the FRD was glitched some other way?
                  My first 2way build

                  Comment


                  • #11
                    I'm guessin' here (of COURSE), but the .zma looks to be for 2ohm config., and (like you say) the sensitivity spec SEEMs to be @ 2ohms (90dB), but the .frd LOOKs like it's for the 8ohm config (which I believe should be 84dB/2.83v). Even though below the resonance "ringing" (@ 2.6kHz) the output crests at only about 81dB (near 90 and 1700Hz), and AVERAGES a few dB less (more like 78-79dB in the useful bandpass), I've seen a peak (like this 92dB spike @ 2.6k) skew the sensitivity rating several dB higher. I ran my sin using the Dayton .frd data, but I'm going to note that THAT data looks to be for 8ohms, and I'm going to add +6dB to the curve to use w/a 2ohm sim.

                    So, using a single planar (and the only proper way to orient it is vertically), and adding +6dB to the .frd files (for a 2ohm v.c. config.), this is what I get for 2nd order filters, w/a notch/tank on the RSS and an "L" and series coil on the planar (9 parts):

                    HP: 28uF series cap, then a 2.0mH shunt coil (to ground), then a 0.25mH series coil (to roll down the tweeter's rising top end), and an L-pad w/ SR=3ohm and PR=3ohm. Reverse polarity is "indicated".
                    LP: a low DCR 2.0mH (iron core) series coil, and a 47uF shunt cap (to gnd). There's a "tank" circuit in parallel with (bypassing) the series coil - it uses a 4ohm resistor and a small 1.5uF cap. This targets the 2700-2800Hz range.

                    Even though this uses (somewhat) bogus data, the sim runs around 80dB/2.8v, +/-2dB, with full baffle-step. Fc is near 900Hz. Filtered planar drops off above 12-13k, but so does my hearing.

                    Anyone else w/any insight/experience?

                    Comment


                    • #12
                      to all it was my first time trying to design a xover at all in Xsim
                      the effect i was going for was this

                      Click image for larger version

Name:	the new god2.jpg
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ID:	1469725in Xsim putting the 1st order lowpass gave this result which is what i want
                      iv also desided to go with one tweeter in vertical on the left an on the right

                      is what its like without the 1st order low-pass
                      Click image for larger version

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                      what ever config achieves this is what im going for






                      an i haven't built the cabs yet



                      Comment


                      • #13
                        I suggest you start over, with different goals. Rear surrounds don't need to go below 80Hz, so the first change is to use a woofer or midbass, not a sub driver. The second is to go ported if it's required to run to 80Hz, sealed if not. The third is to reconsider the driver size. Rear surrounds don't require the output capability of tens.
                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

                        Comment


                        • #14
                          Here's a quick visual/graph of what Chris Roemer described above:
                          Click image for larger version  Name:	VituixCAD_XO-schema.png Views:	0 Size:	5.2 KB ID:	1469737 Click image for larger version  Name:	VituixCAD_SPL.png Views:	0 Size:	26.4 KB ID:	1469738

                          This simulated response includes a ~13"x27" (~0.5"radius) BaffleStep SIM on the woofer. It also DOES include resistance from the inductors, but I cropped the visual from the XOschematic for simplicity and to avoid some confusion (otherwise this particular program shows the inductor resistance like another R in series with each inductor).




                          I also agree with billfitzmaurice and anyone else above who mentioned that an RSS265 (or any other subwoofer) isn't a good fit for surround speakers. If your reciever is setup to send lows to a subwoofer, then none of the other 5-7woofers will see bass below 60-80hz. Even if the reciever is setup to send bass to the R/C/L/RS/LS speakers instead of sub/s, I don't think surround channels see much deep bass. This means you could use a smaller ~6.5" mid-woofer instead of the 10" RSS265, and the midwoofer could get just as loud with that amp while allowing a MUCH smaller box and still digging down around 50-60hz in something like a 9Liter ported box.

                          There's also no reason (that I can think of) to use two of those tweeter+mid for each woofer. A single tweeter+mid (like used in the SIM above) will keep up perfectly fine and loud, while saving money and avoiding the phasing/combing issues you'll get if you use two/each.

                          Of course, if you're more interested in making some "fullrange" speakers for all kinds of things moreso than making surrounds, do what you want and have fun...just saying that for a movie system (which likely included a dedicated subwoofer) these feel like they're using up money and size/space that they don't need and taking away money and space that could/should be used by better dedicated subs.
                          My first 2way build

                          Comment


                          • #15
                            ive updated my design concet ignore the prevous config of
                            a 4ohm input at 300watts
                            with 250watts at 2ohm to the lows
                            an 50watt at 4ohms to the highs with a L-Pad Attenuation of - 4db with a first order lowpass at 1500hz (it is for smoothing out the highs)
                            an a 2nd order highpass at 16hz with a 1.4q

                            ill be going with a singal planar in vertical at 20watts at 8ohm with a 12db Attenuation crossed at 400hz with 280watts at 2ohm for the lows

                            this is what im aiming for
                            Click image for larger version

Name:	the new god 6666.jpg
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                            im really new to this espeacily in Xsim
                            the drivers ill be using are per cab with twin rads are

                            one GRS PT6825-8 8" Planar Mid/Tweeter 8 Ohm

                            an one Dayton Audio RSS265HO-44 10" Reference HO DVC Subwoofer (wired to 2ohms)

                            if anyone can design this correctly to get this fq response id be greatful

                            once designed iv got a guy that can build it for me

                            Comment


                            • AEIOU
                              AEIOU commented
                              Editing a comment
                              Greatful, that's a good one.
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