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Reasonable Expectations for Tweeter Pairs?

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  • Reasonable Expectations for Tweeter Pairs?

    I have too much time on my hands thanks to the Chinese virus lockdown so I've been working on an old project.

    Roughly ten years ago I blew the dome tweeters in my Alesis Monitor One speakers in home audio recording setup.

    I replaced the tweeters with GT-324 metal domes which according to specs seemed to be a decent match for the speakers listed as 88db with 2.5k crossover. Unfortunately the GT-324s were not as loud as I expected and the huge bump advertised at around 1.8k was closer to 2.1k. I have GEQ so it is not a terrible situation. However the pair of GT-324s tonally are a decent match. This is without EQ.

    Click image for larger version  Name:	Monitor One w GT-324.jpg Views:	1 Size:	95.2 KB ID:	1439709

    I thought I'd replace the metal domes wtih GT-510 soft domes. Unfortunately one of the two I purchased had an ugly frequency response and did not pass a normal DATs Rub and Buzz test. Parts Express took care of that problem. The replacment GT-510 was much better but the two tweeters still do not make as nice of a pair as the GT-324s I'm trying to replace.

    Click image for larger version  Name:	GT 510 comparison.jpg Views:	1 Size:	58.6 KB ID:	1439710


    None of the GT-510s have a frequency reponse curve that resembles the advertised curve! In contrast the 10 year old GT-324s still resemble the advertised frequency response curve--cf attached pic below.

    Some years ago I purchased a second pair of GT-324s for another project. I have a comparison of the 4 units below along with the two GT-510s. The GT-324s have a similar frequency curve.

    Click image for larger version  Name:	GT-324 vs GT-510.jpg Views:	1 Size:	115.4 KB ID:	1439712

    I gave up on the GT-510s. Since I need a tweeter that fits the 4" opening on my speakers I purchased a pair of GT-525 soft domes. Thankfully they are better than the GT-510s but still not as good of a pair as the GT-324s. The GT-525s I received are not as desirable for my existing 2.5k crossover as the advertised frequency response curve : (

    Click image for larger version  Name:	GT-525s.jpg Views:	1 Size:	59.3 KB ID:	1439713
    Are metal domes easier to manufacture such that the units tend to have a similar frequency response? Is it harder to make soft domes that have similar frequency response curves?

    I don't want to have unreasonable expectations. Also I have a 31 band GEQ.

    Any thoughts on what is reasonable to expect for <$15 tweeters, especially soft vs metal domes?

    Thanks.
    Attached Files
    Last edited by Joegtech; 05-06-2020, 02:28 PM.

  • #2
    I have frequency response curves from some other old tweeters.

    These are oldies but goodies that I pulled from the trash recently! The pic below shows the super tweeters from JBL J350 floor speakers from the 1980s-- 10" passive radiator, 10" woofer, 4 inch or so upper mid, supertweeter. The passive radiators were blown. The crossover is advertised at 6khz but appears to be closer to 8k.

    Click image for larger version

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    The red and dark blue are the relevant curves below. Surprisingly the sensitivity of the tweeters were not a good match for the upper mid speaker; however it must have been ungodly expensive to make a tweeter that could produce 18khz back in the 1980s.

    Click image for larger version

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    At the other end of the price scale these are three round Motorola piezos from the 1990s. There is also a fourth piezo represented by the bottom two curves. It was a very similar-looking Radio Shack tweeter that I had purchased new in the 1990s. I installed a cap and paralell resistor--1st order crossover--to tame some of the bump at 5khz. It greatly improved the sound probably by reducing distortion. It sounded unusable without the cap.

    Click image for larger version

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