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Thread: Crossover Reversed

  1. #1
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    Question Crossover Reversed

    Hi all, first time poster. I have a question about my newly purchased JBL Studio L880 speakers. I'm pretty happy with them so far, but recently noticed something strange. I had them by bi-amped with a NAD C370 integrated and C270 amp. The configuration was as follows: metal jumpers removed, C370 hooked up to the upper speaker terminals. The C270 was hooked up to the C370 pre-outs (not bridged), and then hooked up to the lower speaker terminals.

    I was experimenting by turning off one amp at a time, to see which drivers were playing. The left speaker performed as expected: with only the C370 on, only the mid/tweeters were operating, and with the C270 on, only the 2 woofers were operating. But with the right speaker, the opposite occured, as if the upper terminals were driving the woofers, and the lower terminals the highs. Any thoughts? Is this a problem?

  2. #2
    Senior Member Don C's Avatar
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    I'd remove the terminal cup and have a look at the color codes of the wires.

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    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Playloud
    Is this a problem?
    Did you purchase the L880's new?

    If if were me, I'd first disconnect - disconnect - the C270 and try only the C370 alone. First, into the LF inputs. Do they operate as expected?
    bo

    "Indeed, not!!"

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    Yes, I did purchase them new at Tweeter. I'd like to avoid shipping them off or lugging them into a service center. After I noticed the problem, I single-wired them to the C370, hooked to the upper terminals, as per the manual. I think they sound very good, I just don't know if they should sound better, or at least different.

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    Senior Seņor boputnam's Avatar
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    OK, my point was, let's get really simple about this. Play dumb with me (I'm good at it when confused about what I think I'm observing...)

    To start:
    - connect only the C370 to the LF on the L - does the woofer work as expected?
    - then, connect only the C370 to the LF on the R - does the woofer work as expected?

    Report back...
    bo

    "Indeed, not!!"

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    Would using a battery to test polarity be appropriate here?

    Mark

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    Senior Seņor boputnam's Avatar
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    Maybe, but let's make sure things are wired-up properly and performing as-expected - in simplest manner.

    It's quite unlikely - but not impossible - that things got wrong at the factory. I'm just trying to make sure we know what is being experienced before we call out the MASH unit...
    bo

    "Indeed, not!!"

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    To start:
    - connect only the C370 to the LF on the L - does the woofer work as expected?
    - then, connect only the C370 to the LF on the R - does the woofer work as expected?

    Report back...

    OK, Bear with me, I'm not technically savvy. I connected only the C370 to the lower terminals on the left speaker (without the metal jumper), and like before, only the mid/tweeter was operating, not the woofers. I did the same for the right speaker, and the woofers operated as expected.

  9. #9
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Playloud
    ...I connected only the C370 to the lower terminals on the left speaker (without the metal jumper), and like before, only the mid/tweeter was operating, not the woofers.
    This is wrong. Since these are new, I'm inclined to load them up and go back where you got them. If this slipped through QA-QC, no telling what else did!! Swap for a NEW pair (or at least the L one...).

    Dood, we are "bearing with you" - thanks for bearing with the pedantic questions (read: me) but we try and not go full-tilt before we verify precisely what is going on! This here is a completely new experience for us...
    bo

    "Indeed, not!!"

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    Thanks for the input. Do you think that this flaw would cause any sonic degradation, or damage, when playing both speakers in a normal single-wire configuration? It's tough to assess sound quality when playing one speaker at a time for comparison.

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    I would certainly wait for Bo to answer but I will express my opinion. If there is 1 thing wrong w/the speakers there may be more.If no damage was being caused, which would be my main concern, it still may not sound right and your test would not be acurate. If the wires aren't connected internally correct you may have phase issues also.

    So my opinion as a beginer is take them back and get it right so you know you have the correct sound before serious evaluations

    See line 1 1 more time

    Mark

  12. #12
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Playloud
    Do you think that this flaw would cause any sonic degradation, or damage, when playing both speakers in a normal single-wire configuration?
    Sorry to be tardy - bogged with IT issues...

    We have no way of knowing. All we know is it is not working as per the owners manual. Period. It should be replaced without hassle from the vendor. That is hassle enough for you. We could get inside and rewire stuff and feel all clever, but fer hellssake, this is not what you paid for.

    You will enjoy these, and paid good money for them. You were clever enough to find this place - now go to the vendor with confidence in your findings.
    bo

    "Indeed, not!!"

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