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"Into The Abyss", Tweeters in low places

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  • "Into The Abyss", Tweeters in low places

    I have generally been against running tweeters below 2500hz a point were most SB tweeters start to misbehave.
    But now that I have been playing with wave guides and a new breed of tweeters that seemingly play nicely
    down to 2K and even LOWER. A well know member of thee audio community told me "never
    expect a 1" dome to go under 2K" and I have lived by it, but the times they are a changing.

    So over the next few weeks I will be testing larger dome tweeters and maybe even some AMTs
    to see what I can get away with, with and without wave guides I will also be experimenting with
    minimal part XO's, that these tweeters and wave guides allow.

    Some of the "victims" on hand.

    SB29SDAC-C004

    Wavecor TW030WA11

    SEAS Prestige 27TBCD/GB-DXT

    Satori TW29R Ring Dome Tweeter

    Scanspeak D2604/833000

    Peerless XT25SC40-04

    Peerless DA25TX00-08

    DAYTON RST28F-4

    And some smaller tweets that might be able to go lower with the use of a wave guide.

    SB29RDNC-C000-4 (and it's beryllium cousin asap)

    SB21RDC-C000-4

    To match or not match levels? There has been some concern, so I will do both.
    Because I often will be comparing another tweeter to the main unit to give
    some sort of reference.

    The test rig will be a B&K 4007 omni and a Focusrite Scarlett 2, the tweets and WGs will be mounted
    to a 19x19 inch baffle counter sunk. Tweeters driven by a hypex UcD 700, with a analog active XO.

    What are your thoughts on standardizing the levels and mic distance, since this test is looking
    mainly at the tweeters ability to play low (and the resulting THD) I am thinking of keeping the
    mic close like 6" to help avoid reflections and background noise. and running the tweets around 100dB.

    Speak now or forever hold your peace.
    Guess xmax's age.

    My guess: 15. His grammar is passable. His trolling is good.

  • #2
    Originally posted by xmax View Post
    To match or not match levels? There has been some concern, so I will do both.
    Because I often will be comparing another tweeter to the main unit to give
    some sort of reference.
    If you intend to only measure a single SPL, then yes by all means level match is the "correct" method. A comparison simply cannot be made accurately if the passband SPL varies between tests. Just as you would not want to create subjective opinions by listening to two different speakers at two different volumes, you would not objectively compare how one tweeter performs at 89dB to another at 92dB, that is not useful information. I'd recommend setting the SPL match to something like 92dB at 1m (regaldless of mic distance).

    Originally posted by xmax View Post
    What are your thoughts on standardizing the levels and mic distance, since this test is looking
    mainly at the tweeters ability to play low (and the resulting THD) I am thinking of keeping the
    mic close like 6" to help avoid reflections and background noise. and running the tweets around 100dB.
    For a distortion test I would say the response from the speaker is secondary and perhaps not important at all, so a near mic of 4-6" is just fine as long as the SPL at the mic is within its limits where it doesn't become overloaded. Ideally, it would be nice to normalize the frequency response such that the harmonic information is all relative to the fundamental, so you don't have to consider the frequency response to determine how many dB down each harmonic is.

    What AMT's did you have in mind ?


    "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
    exactly a Fc 3K for both drivers, anybody can do it." -Xmax

    Comment


    • #3
      That's exactly what I was gonna say but dcibel beat me to it.

      xmax, I'm a big fan of horn-loading AMT's, as I've found out they respond very well. And of course that's why I bought the Beyma TPL-150H's off of you as well. Did you see the results/graphs that I posted with the Hygeia/Airborne RT-5002 with a Dayton H110 horn?

      Comment


      • #4
        I'm also not a fan of low crossed tweeters. I believe that they are just physically too small to make the required SPL levels at lower frequencies. Displacement increases, which theoretically causes distortion. Problem is, I don't know what is considered a lower frequency. Maybe 2000 Hz is fine? 1500? 2500? I don't know. This should be interesting.

        I like your idea of a simple filter, probably first order I guess. I think this really helps see what happens when a tweeter rolls off most naturally.

        Comment


        • #5
          Test with and without a crossover. One thing that does not get tested much is the effect of a crossover on tweeter HD profile.
          -Bob

          The PEDS 2.1 mini system
          My A7 Project - another small desktop speaker
          The B3 Hybrid Dipole - thread incomplete and outdated

          Comment


          • #6
            Originally posted by BOBinGA View Post
            Test with and without a crossover. One thing that does not get tested much is the effect of a crossover on tweeter HD profile.
            You can simply apply the transfer function of the crossover to the fundamental as well as the harmonics for a good idea of the result. This method will be fairly accurate up to the point where the distortion is caused by over-excursion, wither by exceeding xmax or hitting mechanical limits. Within the driver's linear range, the harmonic profile will be proportional to the fundamental amplitude for the most part. Personally, I'd rather see a measurement to about 500Hz without any filter in place.

            "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
            exactly a Fc 3K for both drivers, anybody can do it." -Xmax

            Comment


            • #7
              Xmax, add the SB26STAC to the list. In a guide I'd be stunned if you couldn't run it to well below 2KHz with the proper 2nd order HP filter.
              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

              Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


              95% of Climate Models Agree: The Observations Must be Wrong
              "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

              Comment


              • #8
                Originally posted by Pete Schumacher View Post
                Xmax, add the SB26STAC to the list. In a guide I'd be stunned if you couldn't run it to well below 2KHz with the proper 2nd order HP filter.
                Pete, the 26stac easily plays to 1.8k without a guide. Crossed 3rd order electrical in a series circuit in my Armonicos. I would suspect in a guide, 1.2k would not be an issue.
                https://www.facebook.com/Mosaic-Audi...7373763888294/

                Comment


                • #9
                  I think you all know what song these words are to....

                  Chorus:

                  Yeah- I got tweeters going low places
                  Sometimes waveguides help
                  Them match the traces
                  In the proper way
                  'Least that's what I say

                  Well I'm not big on smiling faces
                  Type of EQ that
                  Jacks the treble and basses
                  Oh I got tweeters going low places

                  ------------------------------

                  At first they didn't sound right
                  The bass was too light
                  And the treble was too hot for sure

                  Turns out initially wrong
                  Helped me write this song
                  And experience helps 'em sound pure

                  And when I get 'em done
                  I'll shine like the sun
                  They are voiced and they measure spot on

                  I'll be really happy with this pair for a while
                  ...But that won't last long!

                  ---------------------------------(Chorus)

                  You know I build speaks
                  From dog woofs to mouse squeaks
                  and you know that this bug has me bad

                  First it was to save money
                  That's what I told my honey
                  But more expensive drivers were to be had

                  I shelled out for a few
                  If I only had knew -----------------------(poetic justice on that one, give me a break!)
                  How far my addiction had gone

                  Now I just can't help it I sit back in my chair
                  ....and listen to song after song!


                  Heeheehee,
                  Wolf

                  "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                  "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                  "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                  "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                  *InDIYana event website*

                  Photobucket pages:
                  http://photobucket.com/Wolf-Speakers_and_more

                  My blog/writeups/thoughts here at PE:
                  http://techtalk.parts-express.com/blog.php?u=4102

                  Comment


                  • #10
                    "even after I knew"?
                    Guess xmax's age.

                    My guess: 15. His grammar is passable. His trolling is good.

                    Comment


                    • #11
                      Originally posted by Pete Schumacher View Post
                      Xmax, add the SB26STAC to the list. In a guide I'd be stunned if you couldn't run it to well below 2KHz with the proper 2nd order HP filter.
                      Ok I will get some, I see they have a little extra air up top, is that why you want to use them with a WG? If you send me the files I will CNC one, since WG help extend the
                      the tweeters low freq. ability they will be used in these tests, but the tweeters will also be measured without the WG to see the difference.
                      Guess xmax's age.

                      My guess: 15. His grammar is passable. His trolling is good.

                      Comment


                      • #12
                        Here is a prime example of how a WG can extend the low end of a tweeter, this was done before the "official" standardized
                        test will begin, but fun stuff, Click image for larger version  Name:	21 WG.jpg Views:	1 Size:	237.7 KB ID:	1378683 this is the tiny SB21RDC-C0004 ring dome with and without a passive LR2 at 4K with a bored out WG16-25-B
                        Guess xmax's age.

                        My guess: 15. His grammar is passable. His trolling is good.

                        Comment


                        • #13
                          How about if I use the same gain setting always so I get a -10 reading @ 2K, =100dB it seems to me if you are looking for a low
                          safe XO that would be a fair and equal test. I.E. adjust volume to get 100db= -10dB?
                          Guess xmax's age.

                          My guess: 15. His grammar is passable. His trolling is good.

                          Comment


                          • #14
                            Originally posted by xmax View Post
                            "even after I knew"?
                            Fits, but the meaning is different.
                            Wolf
                            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                            *InDIYana event website*

                            Photobucket pages:
                            http://photobucket.com/Wolf-Speakers_and_more

                            My blog/writeups/thoughts here at PE:
                            http://techtalk.parts-express.com/blog.php?u=4102

                            Comment


                            • #15
                              Wolf - I never would have guessed you were a Garth fan!
                              Co-conspirator in the development of the "CR Gnarly Fidelity Reduction Unit" - Registered Trademark, Patent Pending.

                              Comment

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