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Thread: a loudspeaker design

  1. #1
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    Default a loudspeaker design

    having discussed the design of a loudspeaker before, this is the follow up.

    To outline the design, it uses two (per side) JPW Sonata 'speakers, a bass box containing an EPOS 10 inch drive unit, and a Fountek CD3 ribbon tweeter. The idea is the use the Sonatas almost 'as is', but without the tweeters. Modifications to the box sides and insides are likely, and the whole lot 'tied together' with aluminium or carbon fibre tubes filled with a damping compound.

    The story so far:

    All I have done is replace the token gesture BAF wadding in the Sonantas with either rockwool fibre or PU foam/Herwick sheep's wool. I have been listening to this setup (one channel only) for a couple of weeks to gauge quality and my pleasure. Signals have all been digital sources, either recordings of live broadcasts from BBC R3 or via Dolby decoded Virgin Tivo on BBC R3.

    I have not listened to the Sonantas individually, to assess which wadding suits the Sonata's best, as it is very subtle, and needs measurement.

    I am going to 'tie' all four boxes together with aluminium and carbon fibre tubes, which will be filled with a Plasticine-type damping compound. This will allow anchoring to a base plate (increasing stability) and the placing of the tweeter between the two Sonata boxes, la the MTM or D'Appolito configuration, if I so wish.

    Yesterday I concluded that the Sonatas aren't reproducing much above 1kHz (to my ears, on classical music) so I boosted the treble on the amplifiers, much much better. They are now playing in a stereo pair with my Usher floorstanders, and, if anything, sound a little better, slightly more definition.

    Here is the idea of the design, so far:


    by
    cheers.....Bryan

    http://qualia.webs.com/

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    I tried the D'Appolito configuration today, although without the ribbon tweeter installed. The sound stage was much larger, and more convincing. I have not seen too much written about sound stage, but, for classical music, I think it is very important, getting the sizes of the sound image just right is important, I think. Just as a huge image of a solo singer/guitarist just doesn't sound right, neither does a tiny orchestra belting out Mahler.

    I'll have to give more thought to supporting the D'Appolito configuration.
    cheers.....Bryan

    http://qualia.webs.com/

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    Reminds me of when I heard the top of the line Focal Utophia's at the Munich show 11/12 years ago. The impression it gave was the acoustic guitar was 12' across and played by a giant 20' tall.

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    D'Appolito configuration.
    What is it?

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    One centrally mounted tweeter between two bass/midrange units mounted vertically.


    http://www.visaton.com/en/lexikon/D/15.html



    https://www.soundonsound.com/reviews/sveda-audio-dapo
    Last edited by John R; 24th November 2017 at 14:10.

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    Ah, thanks J. I've seen that arrangement in many speakers but have never owned a set. In fact I haven't really owned any multiple driver speakers, I prefer 2-way.

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    Of course two way systems,are the norm , but I have 2 sets of three way speakers , just sonys but they are I think quiet well designed any way good basic components , but they do sound rather good , I have also in the past had much more expensive three way speakers and liked them but having these for about 10 percent cost to me of the 2000 units , and still playing tunes nicely , I did after several years of trying out and looking around for speakers find it a bit dissapointing that quiet a few speakers are more style etc than sound , but that's just a personal view it's all opinions , I have in the past had some. Rather poor speakers and been happy enough, loved my Martin Logan older electrostatics , but they need space ,

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    I think one of the problems with two way 'speakers is the high crossover frequency of the bass/midrange unit. This is usually the so-called 'cone breakup' region, where otherwise smoooooth drive units get very peaky. Not good. This is the reason that so many PA speakers (which have a large bass units and often a piezo tweeter) show signs of break-up in the mid range. All boom and tizz, dreadful.

    The down side of three driver loudspeaker (apart from cost and size) is the complicated crossovers. However, with the Sonata drive unit going down to 100Hz (and below) without a hump in the FR (at 12 dB/Oct natural roll off) and the bass speaker covering up to 100Hz and a 12dB/Oct crossover before the 300 watt class D amplifier, which is connected directly to the 10 inch driver voice coil, each drive unit should cope well with it's duty.
    Last edited by cat's squirrel; 24th November 2017 at 22:07.
    cheers.....Bryan

    http://qualia.webs.com/

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    had a little tap with a little hammer, today, to ascertain if the boxes were behaving. Hitting the ends of each (of four) boxes showed that one of them had a 'note' that was a perfect fifth lower than the other boxes. It was the one with the foam/sheep's wool in, although I don't think that any problem would be due to the filling. Looking inside the 'odd' box, I couldn't see any problems. However, when I compressed the end of the box, I could see a small gap in the vinyl wrap close up. Maybe the 'woodworking shop' ran out of glue on Friday afternoon. Anyways, that should be easily corrected. Never underestimate the little hammer.

    Been thinking about what jy3 wrote, about the size of the 'image' or sound stage. I do like listening to classical music, which means small to very large orchestras, and also folk and small ensemble jazz, so small sound stage. I was wondering about the design, and the possibility of having it so that I could change the sound stage, by putting the tweeter box either above or between the mid ranger boxes. From the start, I was always going to use two amplifiers to feed the mid rangers and tweeter, and I have bought a stepped attenuator so that I could change the output of one amplifier/speaker compared to the other. Now, if I mounted the tweeter between the mid range boxes, and used the attenuator on the top box, I could change the sound stage to suit the music! I have never seen this done, maybe a good reason!
    Last edited by cat's squirrel; 27th November 2017 at 18:16.
    cheers.....Bryan

    http://qualia.webs.com/

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    I have been listening to one channel of the proposed loudspeaker (without bass or ribbon tweeters) for a couple of weeks, often with the other channel being my Usher floorstanders. There are differences between the two channels, but it is not great, mostly swings and roundabouts! So far, so good. These Sonata loudspeakers with their inexpensive drive units and boxes are certainly very impressive, to these ears, when sensibly driven (not too loud!). The bass is less compared with the Ushers (much bigger boxes) but the lack of an upper bass hump is certainly less taxing on the ears.

    I've ordered some samples of materials I hope to use in combination with the Sonata's mdf boxes, to increase damping, and reduce box honk! And I've settled on some fittings to use to anchor the aluminium tubes to the sides of the boxes.
    cheers.....Bryan

    http://qualia.webs.com/

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    The Sonatas are very good but JPW made some excellent speakers. I think the original AP2 and AP3 are even better. I have a saved search on ebay for them but when a pair comes up, it usually has some problems.

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    Hi Gary,

    for me, the JPW drive unit (mid bass to high treble) is particularly useful, as it is small enough to not suffer too much from cone break-up, and just large enough to have a decent Fr, AND work in a closed box, not have a foam surround and can handle ~70 watts at 6 Ohms. This is a very good spec. and drive units like this are hard to find and use. Buying them with their boxes saves a lot of time, too!

    DV speaker 4 by cat's squirrel
    Last edited by cat's squirrel; 2nd December 2017 at 23:37.
    cheers.....Bryan

    http://qualia.webs.com/

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    I've made an offer for a pair of floorstanders with the D'Appolito configuration. That phrase reminds me of the film Midnight Run, when Grodin may have asked De Niro (both posing as FBI officers in a bar) if he's tried the 'D'Appolito configuration'.

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    just listened to the ending of Sibelius' 5th Symphony (on BBC R3) with right channel with the Sonatas and the left channel with my extant Usher floor stander. The symphony ends with a number of chords separated by a second or two of silence. Well, I say silence, but it is often possible to hear the chord decay into the natural ambience. As it did this time, except only in the right (Sonata) channel! Quite a weird sensation, a loud chord, dying away and sweeping towards the right! Does this indicate that the Ushers are too well damped? Sonatas are stuffed with either rockwool or sheep's wool/egg carton shaped foam on the back wall.
    Last edited by cat's squirrel; 4th December 2017 at 17:39.
    cheers.....Bryan

    http://qualia.webs.com/

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