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Three Great Tweeters - Files For You

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  • Three Great Tweeters - Files For You

    Yesterday I decided to try an idea for doing quasi-infinite baffle measurements for tweeters in my family room. I found though, that reflections in my room still necessiated that I maintain gating of around 5 mSec, but below that the impulse was extremely clean.

    To test this method I used three tweeters that I had on hand, all new and never mounted. They were the:

    Dayton RS28F,
    Usher 9930, and
    SB Acoustics SB26STAC-04.

    All of these are excellent tweeters.

    The frequency response data (frd file) was measured using 1/48th Octave smoothing. Then I extended the roll-off using software below 750Hz (the response above 750Hz is actual measured data), then I extracted the minimum phase data from the response. I also measured the impedance and included the zma files too.

    As an added bonus I took some distortion plots of each (the scale is different for the RS28, which I did first, so ignore the low frequency stuff in that chart). As you can see, each of these tweeters are quite nice. The Usher 9300, which few people talk about, looks espcially nice for a crossover below 2kHz, and the distortion is low through the rest of its range too. (I also measured a Dynaudio tweeter too, its disortion show an interesting difference in rising odd order distortion with increasing frequency. Hmmmmm. The Dynaudio files are not included.)

    All of these files are contained in a zip file that can be downloaded here:
    http://www.box.net/shared/scv8lzjfkv52ugg002xd

    Happy modeling.

    Jeff B.
    Click here for Jeff Bagby's Loudspeaker Design Software

  • #2
    Re: Three Great Tweeters - Files For You

    Thanks for sharing your files... Even though I've got more tweeters than I currently have time for I'll have fun seeing what can be done with them in PCD.

    Take it easy
    Jay
    "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

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    • #3
      Re: Three Great Tweeters - Files For You

      Thanks Jeff. I still need to pick a tweeter for the Usher drivers that I picked up at the tent sale. The ones you put back.

      Dave
      http://www.pellegreneacoustics.com/

      Trench Seam Method for MDF
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      • #4
        Re: Three Great Tweeters - Files For You

        Thanks for the files Jeff. I really appreciate everything you do for the DIY community.
        I really need to just buy all new measuring equipment for myself now. That way I'll know for sure if what I'm hearing is what is really going on. It's nice to be able to get close with your spreadsheets though and not have to measure a thing. For now I have a SPL meter and test tones to kinda check my results lol.
        Thanks ,
        JB

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        • #5
          Re: Three Great Tweeters - Files For You

          Originally posted by Jeff B. View Post
          [snip]... I extended the roll-off using software below 750Hz (the response above 750Hz is actual measured data), then I extracted the minimum phase data from the response... [snip]
          Hi Jeff,

          Can you elaborate on your procedure to "fix" the lower frequencies in the measured data before you extract the minimum phase? I am having to do this myself, and I am wondering how you go about it. Thanks!

          -Charlie
          Charlie's Audio Pages: http://audio.claub.net

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          • #6
            Re: Three Great Tweeters - Files For You

            Originally posted by charlielaub View Post
            Hi Jeff,

            Can you elaborate on your procedure to "fix" the lower frequencies in the measured data before you extract the minimum phase? I am having to do this myself, and I am wondering how you go about it. Thanks!

            -Charlie
            I set my gating and response measurement to only give me the response up to 4mSec after the impulse. This produces an frd file that begins around 600Hz.

            I import this file into my Response Modeler. Its import function will bring this file in with a flat line all the way down to 10Hz from this 600 Hz point where the data begin.

            At this point I add a sloped high pass roll-off into the transfer function that matches the slope of what I am getting in the graph in the measurements from say around 1kHz down to the 600Hz cut-off. In some cases I have to use the parametric EQ to smooth the transition point a little.

            Once this is done I save the file and extract the phase.

            Of course the assumptions are that the tweeter will have a natural roll-off of 12dB/oct and that the beginning of this roll-off has already been captured in the data, so I am just extending it.

            Once you do it a couple of times it goes pretty fast.

            This results in a measured frequency response with the proper quasi-anechoic / quasi-infinite baffle roll-off and very accurate minimum phase response. The next steps for simulation would be to model a baffle and add in the diffraction response to this file and go from there.

            Jeff
            Click here for Jeff Bagby's Loudspeaker Design Software

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            • #7
              Re: Three Great Tweeters - Files For You

              Originally posted by davepellegrene View Post
              Thanks Jeff. I still need to pick a tweeter for the Usher drivers that I picked up at the tent sale. The ones you put back.

              Dave
              Well, any of these would work. The larger two would be best for a low crossover point though (9930 & RS28F). Of course, there are other tweeters that can do the job too. I am glad these puppies (woofers) went to good home. If I had bought them they would spend a next couple years on the shelf with other drivers :rolleyes:.

              Was Stephanie going to use these? They have that artsy look to them, you know.
              Click here for Jeff Bagby's Loudspeaker Design Software

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              • #8
                Re: Three Great Tweeters - Files For You

                Rising odd order as frequency goes up . . . is there copper in the Dynaudio?
                R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
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                • #9
                  Re: Three Great Tweeters - Files For You

                  Rising odd order as frequency goes up . . . is there copper in the Dynaudio?
                  Not in this model. It's a D28/2 from about twenty years ago, still in the box and never used. I think their new tweeters are built more to today's standards though. The D28/2 that I measured had very low distortion of all orders at 2khz, but by 8kHz the third order had risen above the second order. From an absolute perspective though, it was still pretty low overall, and I don't know that it would be audible. I think it was still -50dB below the fundamental response.
                  Click here for Jeff Bagby's Loudspeaker Design Software

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                  • #10
                    Re: Three Great Tweeters - Files For You

                    Originally posted by Jeff B. View Post
                    Not in this model. It's a D28/2 from about twenty years ago, still in the box and never used. I think their new tweeters are built more to today's standards though. The D28/2 that I measured had very low distortion of all orders at 2khz, but by 8kHz the third order had risen above the second order. From an absolute perspective though, it was still pretty low overall, and I don't know that it would be audible. I think it was still -50dB below the fundamental response.
                    Jeff, if you load them all and expand the vertical scale, there appears to be a pattern for the RS28 and the SB26. I imported them into Praxis for display. From 3.65-10K there's a set of peaks and dips that are at nearly identical frequencies and Qs. This seems too coincidental. When I've had something such as thing occur, it's usually not coincidental.

                    There's a point from about 6K where both also have decreasing magnitudes that look a bit like increasing directionality as the reason. It looks like some kind of diffraction influence, but it's not apparent in the Usher, so I'm a bit puzzled by that.

                    Unless I miss my guess, at least with the SB and the RS, itindicates that there may be something starting at about 7.5" from the driver center. I'm using the first dip at 3.65K as the basis.

                    dlr
                    WinPCD - Windows .NET Passive Crossover Designer

                    Dave's Speaker Pages

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                    • #11
                      Re: Three Great Tweeters - Files For You

                      Thanks for the measurments Jeff...really appreciate it!

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                      • #12
                        Re: Three Great Tweeters - Files For You

                        Awesome! Thank you for posting

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                        • #13
                          Re: Three Great Tweeters - Files For You

                          Originally posted by djdisturbed View Post
                          thanks For The Files Jeff. I Really Appreciate Everything You Do For The Diy Community.
                          Qft
                          :blues: Flat frequency response, a smooth sound power response free of resonance, careful driver-integration, and high dynamic range both upward and downward :blues:

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                          • #14
                            Re: Three Great Tweeters - Files For You

                            Jeff,

                            I have a pair of the D28/2's from 20 years ago. Could you send me the files for them?

                            Thanks.
                            Craig

                            I drive way too fast to worry about cholesterol.

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                            • #15
                              Re: Three Great Tweeters - Files For You

                              Originally posted by PWR RYD View Post
                              Jeff,

                              I have a pair of the D28/2's from 20 years ago. Could you send me the files for them?

                              Thanks.
                              Shoot me an email and I will send the files back in the reply.
                              Click here for Jeff Bagby's Loudspeaker Design Software

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