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Thread: drawbacks w/ constant directivity horns

  1. #31
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    Specifically the PT devices you have been rooting around with in retard mode are not but you keep trying to make it work.
    Yeah, well, seems quite a few more have joined the PT Corps of late.

    When are you going to actually DO something other than blog and blather here, Ian? :dont-know

  2. #32
    Member mini's Avatar
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    new PTs, Geddes o/k

    Quote Originally Posted by Zilch View Post
    Geddes teaches that horn loading is a concept derivative of old-school horn theory which does not apply to waveguides.

    He also teaches that distortion as we know and measure it is irrelevant to sound quality.

    JBL uses some mighty small horns in its current TOTL monitors, down to 1 kHz:

    http://manuals.harman.com/JBL/HOM/Te.../4348%20ts.pdf

    They ALSO use some rather larger ones at 750 Hz:

    http://manuals.harman.com/JBL/HOM/Te.../4338%20ts.pdf

    Go figure....
    Hi,

    I'm very pleased with Your attentivness (irony). Yes, I do appreciate Geddes' work on horn/waveguide theory. Not to say it was the most delightful reading regarding audio transducers of the last years (Distributed Modes Loudspeaker, better known as NXT flat panels was an other one). It had been real fun all the way. When Geddes uses HOM as an issue to encourage his own designs it becomes slightly uncomfortable though. But in the end his kits/boxes may be the best ones available by now especially for the prices called!

    As Zilch remembers I own a pair of impaired EV horns type HP940. This "loads" down to --400Hz as can be seen all to clear from distortion and intermodulation figures. I'm pretty sure Geddes didn't mean it that way when he claims THD wouldn't matter. High THD from overstressed drive and/or compliance is of course a well known issue. For my taste it sounds very disgusting. What could be of less importance is the adiabatic non linearity with compression drivers at higher frequencies. But again, the scientific evidence regarding that is as flimsy as with some other claims in audio. I would really like to see some additional tests of that hypothesis - 4 eyes principle just 2 be sure.

    Do You have any suggestion what PT Waveguide to take with 1" or 2" drivers? I won't let the fancy 235-2 alone using the appropriate 1.5"er with a brand new capture.

    Jurgen

  3. #33
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by mini View Post
    Do You have any suggestion what PT Waveguide to take with 1" or 2" drivers? I won't let the fancy 235-2 alone using the appropriate 1.5"er with a brand new capture.
    I have built several systems using BMS 4555 on the 1.5" PT-F95HF. JBL 2452H-SL mates very nicely with it as well.

    RobH has used the PT-H1010HF with 2435HPL for over a year now, and reports he is quite pleased with its performance, sufficiently so as to retire the 2344As in his DIY 4430s.

    For that same 100° x 100° pattern, I also like the rectangular PT-F1010HF. The PT Waveguide white paper says the difference is that the "compact" rectangular variants ("F") have lower distortion, but less vertical pattern control. The square "rotatable" ones ("H") appear to play a bit lower.

    Several others have built using the PT-F64HF, and I like that one, too, but their 60° x 40° pattern is a bit narrow for my taste. My preference is biased by having 4430s as my mains for over 20 years now.

    If you want to get an idea of how these perform, the thread-on 1" PT-F95HF is only $9.90. JBL Part# 338800-001, it's the one Geddes measured for us. I particularly like it with BMS 4552nd using the P-Audio PC-35 throat adapter.

    Various members on another forum have now completed 20 systems using this waveguide and inexpensive entry-level Selenium drivers, with another several dozen presently being built by others:

    http://audiokarma.org/forums/showthread.php?t=150939

  4. #34
    Administrator Robh3606's Avatar
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    Hello Jurgen

    You can also go with an adaptor for the 1 inch drivers for the 1.5" horns. Attached are photo's of one on a 2416. So any thread on driver 2426, 2425HS or 2418 will all work as well as any other manufacturers drivers as well. Advantage with the 2426 and 2425HS is you can use aquaplased diaphrams in them.

    RobH has used the PT-H1010HF with 2435HPL for over a year now
    I have 2 pair of these in 2 DIY set-ups both use aquaplased 2435's. My goodness how time files it's actually 2 years now!! If you can get them they can sound quite good. The only real problem with them is they are 1K horns. Too bad they don't go lower than that. I have done sims where they look preaty good using the rolloff to get them lower but have yet to have a listen to see what's going on.

    Rob
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    "I could be arguing in my spare time"

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