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Thread: Ultimate Large Format JBL System

  1. #31
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    "Yeah me too! Those slow large format drivers just can't get out of there own way. Who needs a 4" edge wound coil driving a feather anyway"

    The author needs to review Technical Notes Volume 1, Number 8

  2. #32
    Administrator Mr. Widget's Avatar
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    Ian was kind enough to send me the entire article. I read it with great interest. They made many interesting points, and several times said that the reason they picked this or that driver was the taste of the end user and not one of empirical superiority.

    That said, in my own explorations, I must emphatically disagree with their assertion that a 1" exit compression driver is superior to a 2" exit compression driver. I would agree there are times to use a 1" driver, but over the range between 1200Hz and 10KHz in my experience with JBL, Altec, and Meyer drivers that is simply not the case. As they point out in their article the driver is only half of a two part system comprised of a flair (horn) and the driver. I would speculate they didn't try the right 2" horns.

    All in all it was interesting that despite their attitude of breaking fresh ground on the development of high power studio monitors, they ended up with a system that was surprisingly similar to the JBL 4350/55 and the Westlake monitors.

  3. #33
    RIP 2014 Ken Pachkowsky's Avatar
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    Hmm rear's maybe??

    Here we go. It's raining large Westlakes. Looks like a 2122 to me.

    http://cgi.ebay.com/ws/eBayISAPI.dll...category=23786

    Have a good day.

    Ken
    Last edited by Ken Pachkowsky; 08-29-2003 at 10:44 AM.

  4. #34
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    "If the response is rolled off by constriction and there is also a filter, do the rates compound?

    Yes

    "A driver rolled off by constriction is still getting its share of power the amp is putting out at those frequencies below the rolloff hinge. Will the voice coil actually heat up more because the energy cannot be dissipated by conversion to mechanical energy?"

    Not if there is sufficient air movement, which there should be if you are running it on down. I've used countless 112/2108/2121/2122/2202 transducers in such a scenario and have never burned up a coil.

    "If you are after perfection, a minimalist passive high pass filter between the preamp outptut and the mid/high amp using a nice film/foil capacitor/resister may do the trick."

    It's been doing the trick for 20+ years now

    "The slope would be only 6 db per octave as opposed to 12 as recommended by JBL but it would certainly reduce any intermodulation and be as transparent as a filter can be."

    The larger JBL cone transducers are up to the task of handling 6dB/octave filters. The 6dB/octave filter maximizes transient response. It's a Bessel by nature.

    "I recall JBL adopted a similar scheme for the high pass output of the BX 63 sub crossover (ie no chips in the signal path)"

    True, a bit limited but it could have been worse Good enough for mass market consumer stuff.

    "I have thought about doing a passive high level filter, however I don't have any formulae for calculating values that would provide different turn over frequencies for the different input impedances of my various components etc."

    Well I shouldn't have brought the subject up yet again I suppose.

    "I just did a quickie google search and came up with this. It looks like a good starting point."

    Cool!

    Anyway, sorry for opening this can of worms again. I've never had any trouble with any of it but I guess it is possible for some people to start blowing shit up if they aren't careful.

  5. #35
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    "I have nos 3107's (4350), how would You bias them?, I planned to use the bypass caps as described elsewhere."

    Hi Alex,

    Here is a repost since there seemed to be a problem with the original. I went ahead and redrew it to fit the 800 width limit.

    Attached Images Attached Images  

  6. #36
    Administrator Robh3606's Avatar
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    Hello Giskard

    Very nice!! So the 2440 just rolls off. Lot's of caps in that one!!

    "The author needs to review Technical Notes Volume 1, Number 8"

    Where do you find them if they are not in the regular Tech Lib??

    Hello Mr Widget

    I have never had the pleasure of having large format drivers in my home but I had the oportunity to hear some at the MAF. I spent a good amount of my time in Dr. Edgars room listening to the Titans. They were really nice and the midrange was great!! Fast and dynamic, clear as a bell. Just as effortless as it gets.



    Rob
    Last edited by Robh3606; 08-29-2003 at 03:52 PM.

  7. #37
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    "Lot's of caps in that one!!"

    Yes and they are big too. Just one poly/foil will run $40 to $50 if a person goes that route

    "Where do you find them if they are not in the regular Tech Lib??"

    Yeah, I noticed many of the Tech Notes are missing. I sent an email asking them to put them up on the site. I'm hoping because they are Pro and not Home they will come through

  8. #38
    Alex Lancaster
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    Smile

    Giskard:

    WooWW, let's do it again!

    So from the + of the battery, to all the points marked +9V?

    Could You use a regulated 9VDC power supply?, I have a bunch of electrolytics for it.

    Where can I find the original 3107 schematic?

    Thanks Loads.

    Alex.

  9. #39

  10. #40
    Alex Lancaster
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    Smile

    Got it! Thanks again!

    Alex.

  11. #41
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    Love that schematic and Widgets review of the article.

    Having got some ZZ's I actually had a good look through the whole magazine this morning and it would appear they wrote the whole issue (Dec 1986) around monitors and theres a heap of adverts and press releases in it.

    I also see there is opposition to the Reflection Arts approach by Quested and another outfit from Europe. These guys seem to be pushing cones and domes, most likely Dyaudio or the ATC super dome.

    Given this was a U.K Journal perhaps JBL and others like Westlake, Reflection Arts etc were trying to break into the UK market with an alternative offering to the Tannoys, Genelec and BW 802's.

    Has anyone had any experience with these and which is best for the ultimate Large Format Monitor??

    Ian
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    Last edited by Ian Mackenzie; 08-29-2003 at 07:25 PM.

  12. #42
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    Now here's and interesting beast, that looks a lot like a JBL 2123 10 inch mid and a dynaudio D 52 and D 28 in there.

    How dare they mix a JBL thoroughbred from the US of A with those poached eggs from Denmark! I mean hello?

    Ian:o
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    Last edited by Ian Mackenzie; 08-29-2003 at 07:27 PM.

  13. #43
    Tom Loizeaux
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    Mr. Widget,
    You're right that the Parts Express tables are for "speaker builders" and are for assembling passive networks.
    I agree that active filters are the way to go, but most bi-amp systems also use passive crossovers or filters somewhere in their high frequency set up.

    Tom

  14. #44
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    I thought this link was interesting enough to post here for would be doers of the Ultimate Large Format Monitor.

    Although again somewhat of an empirical account of whats good, bad and why, Nelson Pass and may shed some light on just why older style large format speakers sounded so great.

    http://www.passlabs.com/prodlit/rushmore.htm

    Part of his design quest was to research the virtues of old and rather large boxes and apply of best of the past with current state of art electronics to create a fully active system.

    Here is a snippet of a PR document (by Nelson Pass) who recently turned speaker builder.

    Ian
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    Last edited by Ian Mackenzie; 08-30-2003 at 07:15 PM.

  15. #45
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    Technical Notes Volume 1, Number 8

    Originally posted by Robh3606
    Where do you find them if they are not in the regular Tech Lib??

    Rob
    Here it is Rob.

    Technical Notes Volume 1, Number 8, Page 1
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    Last edited by 4313B; 09-01-2003 at 05:54 PM.

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