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Thread: LE14A Full Range?

  1. #1
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    LE14A Full Range?

    I have a pair of S99's with LE14A and LE20-1. The woofers have new surrounds but otherwise all is original. The midrange is very "shouty" and unpleasant. Looking at the specifications and schematic of the crossover, the tweeters are crossed over at 2000 hz but it appears that the woofers run full range.

    I'm a complete novice but doing a little reading about crossovers, it seems that upper end of the woofer can be controlled with an inductor. I think this would be a nice little experiment that can easily be reversed. If this is reasonable, can someone recommend a value, or range of values for an inductor to limit the woofer to 2000 hz or so? The tweeters and woofers are 8 ohms.

  2. #2
    Senior Member RMC's Avatar
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    Hi Bedrock,

    Ideally you would need a LE14A impedance curve, as well as a response curve, in order to determine a proper "crossover point" with the driver, in your case a low-pass "cutoff point". The reason for this is that driver impedance usually varies with frequency, and the 8 ohm value given is only a nominal number, not an exact across the spectrum number. More often than not, impedance value goes up as frequency goes up.

    For illustration purpose only, look at the attached 2226H spec sheet impedance graph, pretty typical with stock form woofers, hence the importance of knowing driver impedance value at a certain frequency.

    In the absence of actual LE14A data you're more or less having to go with trial/error method with different inductor values... A simple inductor will give you a 6 db/oct roll-off.

    Just to help you get going with the experimentation, the crossover calculator in Winspeakerz gives me, for woofer 8 ohms and frequency of 2 khz, inductor value of 0.6366 MH. Double checking this number in crossover tables I have, I get 0.64 MH, so pretty much the same. Good luck, Regards,

    Richard


    JBL 2226H Specs sheet[1].pdf

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    Thanks Richard, that should be easy enough to find.

    Looking at the impedance curve for the 2226H you linked, I see that the impedance at 2000 hz is about 20 ohms.

    If one were to use the 0.64 MH inductor you suggested on the 2226H instead, would the crossover point be at 600 hz or so?

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    Woofer Tester 2

    I found this thread where Zilch tested several LE14A's. The graphs suggest that at 2000 hz, impedance is about 20 ohms.

    Am I reading this correctly?

    http://www.audioheritage.org/vbullet...=woofer+tester

  5. #5
    Dang. Amateur speakerdave's Avatar
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    I'm wondering why the described sound problem is attributed to the woofer and not the tweeter.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Too Many JBLs

    Quote Originally Posted by speakerdave View Post
    I'm wondering why the described sound problem is attributed to the woofer and not the tweeter.
    I also have a pair of L66 and L88, both of which use the same tweeter and are also 2-way designs. I believe those woofers run full range as well, but I'm not certain of it. Anyway, I don't hear any annoying midrange in either of those two speakers so I'm assuming the LE14A is the culprit.

    I'm not ruling out the tweeters or the crossovers as a problem though. Open to suggestions.

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    Senior Member RMC's Avatar
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    Hi Bedrock,

    For my part I had assumed you already determined the woofer appears to be the bugger. JBL having put a 14"! driver with a tweeter I figured the woofer must go relatively high to avoid a "hole" in frequency response, though possibly pretty directional at some point, but that's another matter.

    Yes, in Zilch posts # 1 and 12 impedance is just a little shy of 20 ohms.

    As for your question in post # 3, unfortunately the answer is no.

    A 0.64 MH inductor at 20 ohms won't give you a 6 db roll-off from 600 hz but rather more around 4 khz. To get a 6 db roll-off starting 600 hz with 20 ohms you need instead an inductor with 5.3 MH (Winspeakerz).

    Inductors can also be combined in series or parallel to modify their total value. Regards,

    Richard

    P.S. In order to help you minimize the guessing work related to choice of inductor value for your low-pass roll-off filter investigation (listening tests), I have a simple chart of high and low-pass filter component values that will probably make your task much easier. If interested, send me a private message here along with an e-mail address.

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    So if the woofers measure 20 ohms at 2000 hz, is this the value that should be used to select components for a 2000 hz crossover?

    I found an online crossover calculator and first using 8 ohms, it gave me the same inductor value of .64 MH that Richard posted earlier. I then plugged in 20 ohms for the woofer and was given a value of 1.59 for the inductor.

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    Senior Member RMC's Avatar
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    Hi bedrock,

    Great, now you've found a calculator to help you.

    The answer to your question in post # 8 is yes.

    The 600 hz low-pass filter requiring a 5.3 MH inductor was in relation to your 600 hz question in post # 3.

    With regards now to a 2 khz low-pass filter (6db/oct) I get the same result as you: 1.592 MH for the inductor.

    Regards,

    Richard

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    That's awesome, thank you.

  11. #11
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by bedrock602 View Post
    I also have a pair of L66 and L88, both of which use the same tweeter and are also 2-way designs. I believe those woofers run full range as well, but I'm not certain of it. Anyway, I don't hear any annoying midrange in either of those two speakers so I'm assuming the LE14A is the culprit.

    I'm not ruling out the tweeters or the crossovers as a problem though. Open to suggestions.

    The L66 crosses over at 3000, maybe closer to the LE20-1 comfort zone, but if you have the L88 without the upgrade kit, you may have a point there.

    It might be interesting to put a new, better, capacitor maybe even a charge-coupled pair, in front of the tweeter as a first step (just to be scientific), and you probably should upgrade there anyway while you have everything apart.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by speakerdave View Post
    The L66 crosses over at 3000, maybe closer to the LE20-1 comfort zone, but if you have the L88 without the upgrade kit, you may have a point there.

    It might be interesting to put a new, better, capacitor maybe even a charge-coupled pair, in front of the tweeter as a first step (just to be scientific), and you probably should upgrade there anyway while you have everything apart.
    I like the scientific approach although I don't know what a "charge-coupled pair" is.

    I pulled the crossover out and found that it is the LX4-1, not the LX8 I assumed it to be from looking thru the library here. Need to dig a little further to find a schematic.

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    Senior Member Odd's Avatar
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    Lx 4-1

    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030)

  14. #14
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    Thank you !

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    Crossover Modification ?

    I never use the attenuator on any of the speakers that have LE20's so wondering if I can eliminate the switch, two resistors and the 3.0 MH inductor?

    At this point, I would leave the original x-overs alone and build new ones from scratch. The boards are just 1/4" masonite with some t-nuts attached. No biggie.

    http://www.audioheritage.org/vbullet...2&d=1558412703

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