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Thread: Updating JBL L-88

  1. #1
    Junior Member joetech's Avatar
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    Updating JBL L-88

    I just got a 035Ti tweeter from E-bay for an excellent price. Just one. This is suppose to be the upgrade to the LE25 tweeter. For the price I didn't think I could go wrong.
    I put it in the left speaker and compared the two. I didn't notice much diffence at first but I began to notice that the sound stage was much more forward. My usual listening position it a bit left on center because of a reading lamp. I am usually read while listening to mostly classical.

    Because of the listening position I find the right to be too dominant. I've played around with the balance setting but its more noticable on some music and not on others so I can never get it just right so I usually leave it a 12 o'clock. However, with this new setup I find the sound stage to be much wider so listening position is less critical.

    I've replaced the original cap and those terrible spring wire clamps on the backs of the speaker with some nice posts from PE. I've also added about an inch of fiberglass to the back wall of each speaker. Bass is a bit less boomy which can be a bit of a problem with some classical passages.

    Overall I am very pleased so far. Now I just need to find another 035Ti. I've bid on several pairs in the past but always got out bid or they just went for way too much.

  2. #2
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by joetech View Post
    I've also added about an inch of fiberglass to the back wall of each speaker. Bass is a bit less boomy which can be a bit of a problem with some classical passages.
    Try plugging the port:

    http://audioheritage.org/vbulletin/s...070#post123070

    Damping results here:

    http://audioheritage.org/vbulletin/s...348#post124348

    035tiA is a substantial improvement. A real crossover would also help that configuration - the woofer needs to be shut down above the crossover frequency.

    Get radical. Try the $10 horn....

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    Junior Member joetech's Avatar
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    Thanks for the insight. I did see this thread when it first started but it looks like more has been added since I last saw it. I forgot to mention that I did add about 2 inches of Fiberglass to the back wall when I replace the old caps with some new Solens of the same value (8mf). I has been suggested on another forum that adding a 1.1 mH choke to the woofer would also work. What do you think?

    Have you seen some of the work Troel G from Denmark(can't remember exact URL) is doing with an L-26? He seems to be planning on doing some work with an L100 as will. He hasn't posted any results yet but it should be interesting. I think I'll try some ployfill up around the tweeter. The port tube bends 90 deg down to the woofer. See what that does before i block the port. I think I would try what you did with a plug. That looks like the type of plug used on engine blocks. A temp plug for freeze plugs with a rubber expander. I use to work in an Auto parts store I think it would be a great application.

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    RIP 2011 Zilch's Avatar
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    It's a plumber's test plug, available at your local hardware store or pluming supply for under $3.

    Yes, try adding the choke, too.

    I have seen the L26 work. Got some good tips there....

  5. #5
    Member epoch5's Avatar
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    Zilch is right I plugged my ports and it's a great upgrade for $3.95 each.
    Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming WOW WHAT A RIDE!

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    Anyone ever try one of these things from Parts Express?

    Scan Speak 29001 Flow Resistance Vent

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    Senior Member SEAWOLF97's Avatar
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    Quote Originally Posted by 4313B View Post
    Anyone ever try one of these things from Parts Express?

    Scan Speak 29001 Flow Resistance Vent
    I just use different colored socks for variableness ...the white athletic are densest, the OL's black sox are pretty porous.
    I know my life would look all right ..
    if I could see it on the silver screen

  8. #8
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by 4313B View Post
    Anyone ever try one of these things from Parts Express?

    Scan Speak 29001 Flow Resistance Vent
    I have considered, but never tried aperiodic venting.

    I'm just not clear as to what advantage is to be gained, other than lowering the Fc impedance peak for bottleheads.

    A disadvantage would be that it affords little or no excursion protection; it becomes a leaky closed box from the woofer's perspective.

    There's no denying it works in Dynaco A-25, which I have measured. I don't understand the parameters, obviously.... :dont-know

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    Quote Originally Posted by SEAWOLF97 View Post
    I just use different colored socks for variableness ...the white athletic are densest, the OL's black sox are pretty porous.
    Yep, back in the day when we did such things the dirtiest socks in the L65 ports worked best.
    Quote Originally Posted by Zilch View Post
    I have considered, but never tried aperiodic venting.

    I'm just not clear as to what advantage is to be gained, other than lowering the Fc impedance peak for bottleheads.

    A disadvantage would be that it offers little or no excursion protection; it becomes a leaky closed box from the woofer's perspective.

    There's no denying it works in Dynaco A-25, which I have measured. I don't understand the parameters, obviously.... :dont-know
    You should be able to use something like WT2 to measure the system loss as well as the resulting parameter shifts; If you cared... I was just curious if anyone had every tried them.

  10. #10
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by 4313B View Post
    I was just curious if anyone had every tried them.
    Coming from you, that typically implies there's something of significance to be learned, which we have not yet discovered....

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    Nope. I just saw them while looking for some stuff and wondered. No biggie.

  12. #12
    Senior Member spkrman57's Avatar
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    I've tried variovents before...

    I found that while impedance peak was greatly lowered the cone excusions were not as well controlled as I expected them to be.

    The driver was a Audio Concepts AC-12 which was loaded in a 4 cu ft cabinet.

    I later found better results with the cabinet sealed.

    Qts was approx .4 with Fs of 20 hz and Vas of approx 9 cu ft(from memory).

    The sound was adequate for lower to medium levels without a hump in the bass response.

    I have since found that I can use other methods for better results.

    Maybe someone who has successfully used them and likes them will chime in!

    Just my 2 cents worth!

    Ron
    JBL Pro for home use!

  13. #13
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by 4313B View Post
    Anyone ever try one of these things from Parts Express?

    Scan Speak 29001 Flow Resistance Vent
    I have four unused Scan Speak vents like those in my collection... back in the day when I used Dynaudio woofers I used Dynaudio Variovents... same basic thing. They worked really well, but did allow the woofer to unload below system resonance just like a port will... that was before I had proper measurement gear... I have never actually studied their behavior with proper measurements of impedance etc...


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