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  • Dayton Audio GF180-4 Graph

    So playing around with the graphing for the new Dayton Audio GF180-4....why does it look like it's having a major myocardial infarction? There are so many drastic variations in the FRD its difficult to work with.
    Attached Files
    Last edited by Jicafold; 12-29-2021, 08:45 PM.

  • #2
    You should describe your measurement procedure in detail. Those look like some kind of "artifact" either in the measurement process or the data-processing. I've had some spikes like that appear when extracting minimum phase using Jeff Bagby's program, but not a lot and not in that frequency range.

    PWRRYD just built a two way using the GF180-4 and commented that they were easy to work with.
    New GF180-4 two way project

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    • #3
      This looks more like the manufacturers FRD plot rather than a measurement - correct me if I'm wrong. Did you run the FRD file through a simulator for baffle step/diffraction or something?
      Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
      Refurbs: KLH 2 | Rega Ela Mk1

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      • #4
        It appears that it is some type of interaction between the 2 drivers. Hmmm. Thanks for the link.

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        • #5
          I agree it looks like there are some drastic jumps in the phase response that probably shouldn't be there.
          If the rest of it is good and you just need to get rid of those spikes, you can open the FRD in NotePad and delete the little spikey bits (delete all three parts of the line at once...Frequency, DB, and Phase) where you see drastic changes near those problem spots. It'll give a little false smoothing, but should only be for those tiny bits.

          Some of the Dayton tweeter FRDs have this same problem.

          You also might want to try switching polarity of one of the drivers to see if the response can add together where they overlap instead of canceling like they appear to be.
          My first 2way build

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          • #6
            Care to post your .frd files?

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            • #7
              ? I used the standard files posted on Parts Express. But here they are...
              Attached Files

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              • #8
                Playing around a bit more it got even worse....This was using the values from one of those cheap 2 way crossovers sold on Amazon. I imagine like LOUT says, just ignore it.

                Attached Files
                Last edited by TroyH; 01-03-2022, 10:26 PM. Reason: Links to competitors prohibited

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                • #9
                  Do you want my actual frequency response and impedence measurements of that GF180-4 woofer taken in a real ported enclosure with a 8.00" wide baffle (1/2" roundovers)?
                  Craig

                  I drive way too fast to worry about cholesterol.

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                  • #10
                    I think what is happening to generate those spikes is an interaction of the phase of the two drivers. I note there are no spikes in the frd curves of the raw drivers. I have a feeling this is due to not generating minimum phase data, as I threw the PE files into VituixCAD and got some spikes too, but when using minimum phase they went away. There are several things you need to due to the PE files to get an accurate simulation...model the diffraction/baffle step loss, model the in-box impedance of the woofer, and generate minimum phase. (Probably some more stuff I am forgetting.)

                    https://sites.google.com/site/undefi...d-measurements
                    http://woggmusic.com/advanced-speake...gn-simulation/

                    One other thing to note...that tweeter has slightly less sensitivity than the woofer. Usually you will want to "pad" down the tweeter somewhere between 0 and 6 db due to baffle step loss. If you plan on having no baffle step compensation (BSC) then you may be okay, but otherwise you may need a different tweeter. Additionally, the recommended minimum crossover for that tweeter is 3Khz and 2Khz for the woofer, so there isn't a good overlap there. I believe PWRRYD is the first person to use the new woofer and has good things to say about it, so maybe consider a different (better?) tweeter that can cross lower.

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                    • #11
                      Unfortunately, I am with A4 here, and think the TD20 is not able to go low enough.
                      I also agree with DeZZar and A4, in that you need to alter the files to adapt them to your cab design adding BSC and box alignment.

                      Wolf
                      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
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                      • #12
                        Ah...ok. I was using that tweeter because I already had 2 of them. Also, I had not figured in the BSC either in modelling. Just wanted to try out those new woofers but I certainly don't have to. Thank you.

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                        • a4eaudio
                          a4eaudio commented
                          Editing a comment
                          I have 4 of the 8-ohm woofers but I haven't done anything with them. BUT...they do look great and PWRRYD likes the sound of them. Your tweeters are nothing to be excited about though. I'd say get the woofers and different tweeters that match better and save the TD20's for something else or sell them.

                      • #13
                        "As-is", PE's .frd file has a LOT of phase "swings" (between +175* and -175*) from 300Hz up to 3kHz. (You can see this in the text file, if you look.)
                        Phase (which is a 360* phenomenon) is recorded in F/Z files as "zero", plus-or-minus 180*.
                        When the data passes +180* (for example), it gets recorded as -179* (or whatever). (This is known as phase "wrapping".)
                        In MOST XOsim softwares, this causes no issues (the software is designed to interpret the data correctly).

                        What software are you modeling this with?

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                        • #14
                          IF you can try it safely (without commiting too much if you don't like it), do you think something like this might work for that TD20?
                          Click image for larger version  Name:	Maybe TD20.png Views:	0 Size:	2.3 KB ID:	1480598
                          It looks like this should keep under 0.1mm of XMAX for the TD (which I think it has 0.2mm) with the GF180/system given ~20-25watts (where the GF180 in a 21L ported box would also be nearing/hitting XMAX of its own).

                          It should also be about -5db at 2Khz...for easier pairing with the woofer down lower.

                          I don't have an ear for most distortion (or much of anything, ha) so I can't say whether or not you or anyone else would like the sound of it...but I've been running my TD20's with various similar HP for the last couple of years and they seem happy enough.

                          ...Please ignore me if this whole project is using the GF as a midwoofer in a 3way or some similar configuration where the system will be pushed a lot harder.
                          Last edited by LOUT; 01-02-2022, 12:52 PM.
                          My first 2way build

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                          • #15
                            I haven't had to do this in a while, but I used to sometimes have to manually adjust some phase numbers in Excel. In my experience, when I was seeing these kind of jumps, it was because the phase in a driver's measurement was wavering back and forth between 180 and -180, and the simulation software didn't know how to handle these "jumps." So basically, I'd just pick a number, say 179 degrees, and just stick with it for a few Hz until the phase looked like it was truly ready to rotate over to -180. Yes, it's not 100% accurate, but it definitely helped make Frequency Response graphs that were easier to read.
                            Isn't it about time we started answering rhetorical questions?

                            Paul Carmody's DIY Audio Projects
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