Results 1 to 10 of 10

Thread: 4312As with the mid out of phase

  1. #1
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12

    4312As with the mid out of phase

    So this is weird. I picked up a set of 4312As a few years back. But they have just never sounded right to me. I poked around a little when I first got them, but everything looked OK. I didn't like them as much as my Centurys, so they went in my office. Where they still didn't sound right.
    We moved and they got put in use for the media room. I was watching an episode of Monk and everything sounded wrong. His voice sound liked there was nothing but upper mid. And the imaging had always been super unstable.
    So I looked at them again, but this time with a ton of knowledge from this site and Audio Karma. It turns out the tabs of the mid... 104H-3s... were wrong. It has the "genders" of the tabs reversed. Plus was on the left side of the speaker as the wiring diagram shows. But it's tab accepted only the negative wire. I tested the speaker; + moves the cone forward as stated in the tech sheets for the 104H-3. Has anyone else encountered this?
    So anyway I got in there are put another set of connectors in the wires so I can easily change the polarity/phase.
    They sound SO MUCH BETTER now. I could go on and on about the difference between my early 70s Centurys and my mid-80s 4312As... now that the midrange speaker is in phase. Much flatter than the Centurys. Piano and voices in particular benefit from the improved mid-range. Loads of bass, but not so peaky at 70Hz. They're mirror imaged... and as a result the imaging is spectacular.
    This is my first post. I'll post some pics If I can figure out how to do that...
    Last edited by Zeb Norris; 06-07-2020 at 03:04 PM. Reason: corrections

  2. #2
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12
    Lol anyone know how to post pics?

  3. #3
    Senior Member Odd's Avatar
    Join Date
    May 2009
    Location
    Oslo, Norway ------ Now Portugal
    Posts
    716
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  4. #4
    Senior Member grumpy's Avatar
    Join Date
    Oct 2003
    Location
    SoCal
    Posts
    5,691
    Missed the AK storyline, so this may be old hat:

    Check the woofers? Perhaps a previous owner got them in backwards (push terminals vs sized tabs?)
    ... as it’s supposed to be wired out of phase with the other drivers (black stripe to neg terminal), and is run wide open (no crossover filtering) so lots of driver overlap.

    https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Jbl-4312A-L-Technical-Manual.pdf

  5. #5
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12
    Thanks Grumpy, but everything else was correct.

  6. #6
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12
    Here's what I found, and how I proceeded. Made it easy to switch back.
    Attached Images Attached Images    

  7. #7
    Senior Member grumpy's Avatar
    Join Date
    Oct 2003
    Location
    SoCal
    Posts
    5,691
    Glad you got it sorted! Factory mistakes have happened.

  8. #8
    Senior Member DavidF's Avatar
    Join Date
    Apr 2003
    Location
    Sonoma County CA
    Posts
    939
    I hesitate to go down the driver polarity path on this but should add some background on your situation.

    Agree that the terminals, male and female, on the mid driver are reversed according to the tech sheet illustration.

    On this vintage of JBL drivers the male terminal is the "positive" terminal in the broad industry sense. A positive signal to the male terminal will cause the driver cone to move outward. It appears you confirmed this.

    Your system follows JBL convention that is the reverse of everyone else as to driver polarity. The tech sheet shows all three drivers wired in the same polarity. Your conversion reversed the mid polarity relative to the tweeter and woofer.

    As to whether this is correct per design, I don't think it is. Since you much prefer the sound with the mid reversed, then it makes sense to leave it as so.
    David F
    San Jose

  9. #9
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12
    Quote Originally Posted by DavidF View Post
    I hesitate to go down the driver polarity path on this but should add some background on your situation.

    Agree that the terminals, male and female, on the mid driver are reversed according to the tech sheet illustration.

    On this vintage of JBL drivers the male terminal is the "positive" terminal in the broad industry sense. A positive signal to the male terminal will cause the driver cone to move outward. It appears you confirmed this.

    Your system follows JBL convention that is the reverse of everyone else as to driver polarity. The tech sheet shows all three drivers wired in the same polarity. Your conversion reversed the mid polarity relative to the tweeter and woofer.

    As to whether this is correct per design, I don't think it is. Since you much prefer the sound with the mid reversed, then it makes sense to leave it as so.
    Agree it doesn't make much sense. It's not like just MY mids have a "male" connector on the positive terminal. But that IS positive, as I confirmed with a AA battery. After the change the wiring is as illustrated in JBL's wiring diagram.

    I tried a AA battery on the entire speaker, but the crossover network only put the power to the woofer.

    Anyway, I do know enough about the sound of out-of-phase drivers to be confident they are now correct. Huge improvement. Now they sound a lot more like my Centurys. Smooth response to a frequency sweep, as opposed to a volume dip or hole in the crossover zone.

    But it's bizarre.

  10. #10
    Junior Member
    Join Date
    Dec 2013
    Location
    Montpelier Vermont
    Posts
    12
    Quote Originally Posted by Zeb Norris View Post
    Agree it doesn't make much sense. It's not like just MY mids have a "male" connector on the positive terminal. But that IS positive, as I confirmed with a AA battery. After the change the wiring is as illustrated in JBL's wiring diagram.

    I tried a AA battery on the entire speaker, but the crossover network only put the power to the woofer.

    Anyway, I do know enough about the sound of out-of-phase drivers to be confident they are now correct. Huge improvement. Now they sound a lot more like my Centurys. Smooth response to a frequency sweep, as opposed to a volume dip or hole in the crossover zone.

    But it's bizarre.
    I've been hesitant to re-cap them... thinking if that was required, I would update the entire crossover instead.

    Question; could a failed capacitor in the crossover change the speaker phase? They ARE 1986 speakers.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Altec radial phase plugs vs concentric phase plugs
    By Altec-Lansing in forum Lansing Product DIY Forum
    Replies: 0
    Last Post: 03-28-2016, 06:48 PM
  2. 802 annular phase plug vs Tangerine phase plug pt2
    By sean19 in forum Lansing Product DIY Forum
    Replies: 2
    Last Post: 08-27-2015, 11:05 PM
  3. Altec 802 annular slit metal phase vs TANGERINE PHASE PLUG
    By sean19 in forum Lansing Product DIY Forum
    Replies: 4
    Last Post: 08-19-2015, 07:24 PM
  4. Picked up a pair of 4312As that need some work...
    By Jon S in forum Lansing Product Technical Help
    Replies: 2
    Last Post: 02-18-2009, 09:44 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •