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RS28AS vs. RS28A, interesting finding

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  • RS28AS vs. RS28A, interesting finding

    Not long ago, someone asked me if the RS28AS (that is, the shielded one) was compatible with the Core project. I wasn't sure, because it seems to me that whenever someone asks about swapping in the shielded for unshielded, people seem to say that the two are different, and crossover adjustments would have to be made. Well, this guy was nice enough to lend me a pair to test head-to-head, and here are the results, which I personally find surprising.

    First, take a look at the shielded and unshielded tweeters' frequency response. I measured both of these in the Core cabinet, one after the other. I made sure not to move the mic at all. The two are overlaid. The unshielded is in black, the shielded is in red:


    Seems awful darn close to me. So let's look at the impedance. Same as before: unshielded in black, shielded in red.


    Finally, let's look at how the actual speaker works using either tweeter. I don't know about you, but this looks like a drop-in replacement to me.


    And just to make sure I wans't lent some fluke shielded tweeters, I tested them against one another, and they measured very close.



    So, make of that what you will, but if you ask me I'd say that means that the unshielded and shielded tweeter are interchangeable. As I said, I found this surprising, because it seems to me as though this is not the commonly-held belief around the internets.
    Attached Files
    Isn't it about time we started answering rhetorical questions?

    Paul Carmody's DIY Audio Projects
    Twitter: @undefinition1

  • #2
    Re: RS28AS vs. RS28A, interesting finding

    Originally posted by Paul Carmody View Post
    As I said, I found this surprising, because it seems to me as though this is not the commonly-held belief around the internets.
    I was also solidly under the impression that they were at least somewhat - if not very - different drivers.

    Thanks for this information. Is it possible this is a generational thing? i.e., an early run differed from a later run?

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    • #3
      Re: RS28AS vs. RS28A, interesting finding

      Originally posted by Paul Carmody View Post
      Not long ago, someone asked me if the RS28AS (that is, the shielded one) was compatible with the Core project. I wasn't sure, because it seems to me that whenever someone asks about swapping in the shielded for unshielded, people seem to say that the two are different, and crossover adjustments would have to be made. Well, this guy was nice enough to lend me a pair to test head-to-head, and here are the results, which I personally find surprising.

      First, take a look at the shielded and unshielded tweeters' frequency response. I measured both of these in the Core cabinet, one after the other. I made sure not to move the mic at all. The two are overlaid. The unshielded is in black, the shielded is in red:


      Seems awful darn close to me. So let's look at the impedance. Same as before: unshielded in black, shielded in red.


      Finally, let's look at how the actual speaker works using either tweeter. I don't know about you, but this looks like a drop-in replacement to me.


      And just to make sure I wans't lent some fluke shielded tweeters, I tested them against one another, and they measured very close.



      So, make of that what you will, but if you ask me I'd say that means that the unshielded and shielded tweeter are interchangeable. As I said, I found this surprising, because it seems to me as though this is not the commonly-held belief around the internets.
      Thanks Paul. That is very helpful. I have used both tweeters, but not at the same time and in different boxes, so I had no reference to tell how close they were. The plulished curves have a different Q with quite a bit of difference at the knee, but your plots don't show that to be an issue. This means that some designs may have some new life.

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

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      • #4
        Re: RS28AS vs. RS28A, interesting finding

        Just out of curiosity, would it be a big bother to overlay the RS28F-04 onto those graphs?

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        • #5
          Re: RS28AS vs. RS28A, interesting finding

          Originally posted by turn2 View Post
          Just out of curiosity, would it be a big bother to overlay the RS28F-04 onto those graphs?
          Yeah, I thinking the same thing. The response and impedence graphs would be very interesting.
          Thanks,
          Aaron

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          • #6
            Re: RS28AS vs. RS28A, interesting finding

            thanks paul. i didn't know that the a would go that low.
            " To me, the soundstage presentation is more about phase and distortion and less about size. However, when you talk about bass extension, there's no replacement for displacement". Tyger23. 4.2015

            Quote Originally Posted by hongrn. Oct 2014
            Do you realize that being an American is like winning the biggest jackpot ever??

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            • #7
              Re: RS28AS vs. RS28A, interesting finding

              Originally posted by arlis_1957@yahoo.com View Post
              thanks paul. i didn't know that the a would go that low.
              Just because it measures that low, does not mean it cleanly does so. Lowest I've seen it is the 1.2kHz in Mark K's project with the RS225.

              Later,
              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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              • #8
                Re: RS28AS vs. RS28A, interesting finding

                Paul, good find - a little surprising considering how different the spec sheets looked, back when I looked at them long long ago...

                Jeff, when you quote a message you don't have to include all the photos, thread is a lot neater if you don't. The only reason to do so would be if you replying lots of pages later and wanted to bump the pics up to the end...

                Originally posted by turn2 View Post
                Just out of curiosity, would it be a big bother to overlay the RS28F-04 onto those graphs?
                The A and F (and now we know AS) are definately drop-in swappable at the crossover frequency range, with the difference being the F having a slight rise at the top end (which most people can't hear?).
                "...this is not a subwoofer" - Jeff Bagby ;)

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