Upgrading the JBL L200

Discussion in 'Speakers' started by Fast996, Dec 5, 2010.

  1. Fast996

    Fast996 Mod that Vintage Gear

    I have aquired a pair of JBL L200's and with my current pair that I purchased in the early 70's I want to use them in a 4 channel system. I have a large room downstairs and for under a 1000 invested I just couldn't see going with anything else for the money.

    What is the mods that can be done to these to improve the bass,midrange and high frequency sound. I wouldn't consider changing the woofers out but would be interested in adding a high freq. driver and upgrading the crossovers.

    I did a quick search but didn't find what I was looking for. If there is a thread please post it.

  2. barredowl

    barredowl Before and after Science

    Might be an interesting ewave with a modern wave guide, do a search here.
  3. Fast996

    Fast996 Mod that Vintage Gear


    Is that the thread that is 817 freakin pages?? How bout the super micro condensed version, say 3 paragraphs...maybe.
  4. Zilch

    Zilch Curve Junkie Subscriber

    It's all summarized with links in the first post of the thread here:


    Literally hundreds have been built by others worldwide; that thread is now pushing inexorably toward a million views.

    The precursors to EconoWave were L200s built by both AKer Jackgiff and myself, fully documented on Lansing Heritage in the Q&D thread.

    Here's the index:


    Do that with today's standard E-Wave driver and waveguide using the high-efficiency variant of the crossover, and you'll be good to go with a cool $400 or more extra in your pocket after reselling the original drivers, horns, crossovers and acoustic lenses.... :yes:
    Last edited: Dec 5, 2010
  5. Tom Brennan

    Tom Brennan AK Member Subscriber

    How about a compensation network for the original compression drivers and horns? Then he'd still have L-200s but improved. Perhaps.
  6. Zilch

    Zilch Curve Junkie Subscriber

    Been there, done that, Tom. The original exponential horns beam the high frequencies so badly that the vertical beamwidth virtually goes negative. See Fig. 4 here:


    The only other way to "fix" them is convert to 3-way, the standard approach being to add JBL slot tweeters with N4333 crossovers, a $500 - $1000 upgrade, and unless you also change out the horns to the longer exponentials, that's still not going to get quasi-L300, which further requires swapping out the woofers with 2235H to achieve the extended bass of those later designs.

    L200B boosted the HF with comp, and failed for these reasons, even with Greg Timbers (as I recall) doing it. 2-way just didn't happen until 4430, and nobody's looked back since....

    Footnote: See the Altec 511 directivity and beamwidth plots in that tech note, as well, Fig. 3. BOTH the horizontal and verticals beam, and that's why 4430 with its true constant-directivity horn by Keele beat out Model 19, the first product to actually incorporate HF comp as a 2-way VHF extension strategy some 3-4 years earlier.
    Last edited: Dec 5, 2010
  7. 4343

    4343 AK Subscriber Subscriber

    As one that has used the very same components for many years:

    While I love the sound of the "Foghorn" and L91 Acoustic Lens, it has limitations, mostly the lack of "Flat to 20K" that some people like. (I find the rolloff very nice, but I've learned to also like the sizzle that's missing...)

    Also, the directionality is lacking. If you take the Acoustic Lens off, you will hear the horn beaming all the highs right down the middle, the lens tries to spread the highs sideways, but only does a mediocre job of it. You must still aim them at your ears to get a flat response. Much to the side and the highs get muffled.

    The modern Constant Directivity waveguides solve this problem, for a lot less change. Now I'm not one to say you should cut up decent L-200's*, and just adding a supertweeter can bring them into the '80's, soundwise, but it has been done before, and the results are pretty amazing, not that the stock or tweeter modified L200 can't sound pretty amazing in it's own right (take a pair outside and feed them some watts, you have a downright amazing backyard barbecue/block party system! Reworking the crossovers to eliminate any tiny iron core inductors (and recapping) can make them sing even more.

    My 3 paragraphs.

    *Others have been pounded pretty hard for suggesting that in the past, maybe not here, but near here!
  8. 4343

    4343 AK Subscriber Subscriber

    I did not know that. That's my one reservation about the 4430, trying to EQ the top end flat pushes the diaphragm into breakup, which looks like extended high end, but sounds like hash. Does anyone make 1.75" Be diaphragms?
  9. Zilch

    Zilch Curve Junkie Subscriber

    Smith, Keele, and Eargle rolled off the 4430 VHF at 16 kHz; the reason is apparent in the distortion plots.

    1.75" Be diaphragms are in the works at TruExtent.
  10. Fast996

    Fast996 Mod that Vintage Gear

    Thanks Zilch, I will read through it.

    How about the complaints on the bottom end,boomy and such. Can a redone crossover help this?
  11. Fast996

    Fast996 Mod that Vintage Gear


    Can the stock tweeter be modified? Or is that accomplished by adding a super tweeter.
  12. Zilch

    Zilch Curve Junkie Subscriber

    Not everyone agrees with respect to the boomy bass; you're just going to have to listen for yourself, once you've done the HF upgrade.

    Jack and I both switched to 2235H.

    The original woofers have high resale value, I suspect because DIYers are using them in bass horns, maybe.... :dunno:
  13. Tom Brennan

    Tom Brennan AK Member Subscriber

    I used a pair in fairly big sealed boxes; actually they were L-220 boxes left over after I sold off the guts. Anyway they sounded pretty good but then again I wanted them to; know what I mean?
  14. 4343

    4343 AK Subscriber Subscriber

    The stock tweeter is more of a midrange, really. It's spec'ed to 20KHz, no qualifier, which means it's probably at least 10dB down up there. And eq'ing it up to flat only adds distortion, lots of it.:thumbsdn: (Caused by the fairly large dome "breaking up", where the metal actually bends due to standing waves building up in it.) They have a real nice rolloff that makes vocals and acoustic instruments sound very natural. Tube amps can make them sound really nice.

    They are what they are, a fairly nice sounding, efficient tweeter horn/lens that sells for a nice price. Assuming the original Aluminum diaphragms are in good shape.

    I still remember the first time I heard them, I immediately set out the sell my Altec 511 horns with 808-8A drivers and acquire them. Never looked back.

    Since the Ewave bug bit, I've been using them less, and less, and less. Now with Be diaphragms, and a CD horn...
    Last edited: Dec 5, 2010
  15. toddalin

    toddalin Super Member

    Best mods to make to the L200 include:

    Punch out the back to put the longer horn in (shown here with the LE175 driver):

    BTW, at the lower end of their range, the LE175 is smoother and extends lower than the LE85 and almost lets you get away with the shorter horn.

    Redo the crossovers:

    Add the slot tweeter:

    Cut out the base, make it taller, and put a new base on it to get the woofer further from the floor and add ~3/4 cubic foot of internal volume and put a plug in one of the two ports.
  16. Fast996

    Fast996 Mod that Vintage Gear

    Great! Now what are the numbers for the slot tweeter and longer horns?

    After doing these modifications,how would you decribe the sonics compared with the original configuration.
  17. Zilch

    Zilch Curve Junkie Subscriber

  18. toddalin

    toddalin Super Member

    Speaker essentually becomes an L300, but with a better crossover.

    Longer horn is the H92 (as opposed to H91) or 2312 (as opposed to the 2307)

    Tweeter is an 077 (or 2405)

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