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  • Audio Exciters. You can't ignore their existence if you've ever clicked on a parts-express email. I've always been intrigued, and finally after being pummeled by ads for a couple of years, I dove in a little deeper. There are a few helpful articles, and videos. I looked at several, compared, contrasted, and took a stab at it. I wanted to to keep the cost to a minimum. I didn't have high hopes, but the stakes weren't high either. I bought the exciters on Amazon. At the time parts-express was out of stock on several models.
    One inch thick polystyrene foam is a popular media to mount the exciters on. I used the pink foam panels from home depot. From the 2' x 2' squares I cut the largest pieces that I could get at a 3 x 5 format. This ratio seems to be a magic rectangle that enhances the performance when used with overall size, and mounting location.

    There were a few things that I believed to be in a popular consensus. Mainly, they are limited in range. The response deteriorates below ~200, and above ~4kHz. This obviously wouldn't be useful in a stand alone situation, but instead best utilized as a system component. Class D plate amps from small to large are also always in the parts-express ads. Having the need to power a sub woofer as well as the speakers, I decided on a low power 2.1 channel plate amp. It's 22w per channel, with a 50w sub channel that has separate volume and threshold controls. It was very well suited for what I wanted.

    The need for a subwoofer was apparent. I recalled an article that I had read about 'transmission path speaker enclosures'. Being intrigued by the idea for a while, this became the perfect opportunity to try it out. I used an inexpensive 8" poly cone sub, and 8" aluminum cone passive radiator connected by a long port. No science involved in my design, I made the path as long as possible going from the speaker to the passive. I was originally going to only port it, but saw a great chance to try the passive radiator coupled with the transmission path.
    The bottom end being handled, I took the simplest, and least expensive path for the higher frequencies. The Two-way 3,500Hz crossovers came from Amazon. The 2 1/2" paper cone tweeters are from parts-express.
    None of these parts were expensive. They were all in fact, dirt cheap. Everything for the entire project totaled around $150. For that type of spending in the Hi-Fi audio world, you generally don't get much, and what you do get doesn't sound all that great. Granted, my hearing isn't as good as it used to be, but this setup sounds huge. Phenomenal clarity that sounds more like a thousand watts than one hundred. The sub-woofer is an absolute cannon. It's obvious why this type of construction is so effective in small radios, and powered speakers. The radiant surface of the foam panel is very large compared to most things designed to reproduce mid-range frequencies. I'm convinced this is a big contributor to the overall high efficiency of the system. It also seems that they are much less directional than a small midrange driver. The cheap paper cone tweeters sound fine to me, but my high frequency hearing is a little impaired.
    Class D amplifier technology has advanced far enough that it is accepted and used in maybe the majority of consumer based audio products nowadays. Their benefits of very small power construction, virtually no heat generated, and low cost of construction are hard to deny. This tech is improving continuously, and is no doubt the current direction of audio products of the near future. I've been using a 50wx50w Class D bluetooth amp in my garage for years to power a pair of old Bose 301 bookshelf speakers. I paid less than $10 for it. If, and when it dies, I have a spare on the shelf.
    I'm using the new stuff for my home entertainment system. It replaced a Pioneer Audio and Cerwin-Vega speakers setup that I had used for a couple of decades. This started out as an experiment quell my nagging curiosity, and resulted in a far more successful outcome than I hoped.
    I'm not done playing around with the audio exciters yet. Their frequency response that I mentioned earlier falls nicely into the range of a guitar. I plan to experiment with some different materials and the usability with a guitar amp. I haven't seen any work on this to date. I'm really interested how they sound recorded compared to various guitar speakers.

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    Last edited by John_H; 06-08-2021, 05:40 PM.


    • Interesting! Hope you can post some photos, too!
      I build and repair guitar amps


      • FWIW, and this is just my personal opinion, of course. I've always preferred the sound of paper tweeters. They sound much smoother than the alternatives, regardless of cost, to my ear.
        "Yeah, well, you know, that's just, like, your opinion, man."


        • Originally posted by xtian View Post
          Interesting! Hope you can post some photos, too!
          You're not seeing the thumbnails?

          FWIW, and this is just my personal opinion, of course. I've always preferred the sound of paper tweeters. They sound much smoother than the alternatives, regardless of cost, to my ear.
          Good point. I've never heard any that I considered harsh.


          • Originally posted by John_H View Post
            You're not seeing the thumbnails?
            Now I am. Thanks, looks very cool.
            I build and repair guitar amps