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Thread: 4320 to 4333 Upgrade – did you change the ports?

  1. #1
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    4320 to 4333 Upgrade – did you change the ports?

    Hi All – I’ve started refinishing some 4320 cabinets that I’m going to repaint and re-veneer in my quest to upgrade it to a 4333. I’ve got all the drivers (2231, LE85+H91, 077) and one 3133 crossover in the mail (still need a second if you have one you’d part with).

    My question specifically is around porting. The 4320 has (2) 4” ports with 7 Ό” tubes while the 4333 is spec’d to have a single 4” port with 4” long tube. It seems like I should remove one of the tubes and block that port and then shorten the other tube (presumably by removing, sawing and then reinstalling). Any tips for removing and reinstalling the port tubes?

    Does this plan sound right to you folks? Both 4320 and 4333 have the same cabinet dimensions and volume (5.5 ft3). I know lots of people on this forum have done the conversion before but I haven't been able to find any information specifically on port mods.

    Thx, David

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    remove the tubes with a thin utility knife

    Thru trial and error, I was able to remove the port tubes best using a thin utility knife. The kind with the retractable blade that you can snap off when the tip becomes dull. The larger blades were too wide to effectively bend around the radius between the tube and the circular port hole. I had a smaller utility knife with a 3/8" blade that worked well. Just extend the blade a little and score around the edge and then progressively extend and score deeper until you have separated the tube from the port. Eventually, you can wiggle the tube until it becomes free.

    One of my errors was finding this really thin Japanese saw blade (only 6" long). I thought it would be perfect but the teeth ended up eating into the baffle a little so now i have to repair that with a little more bondo. In the end, the razor blade worked much better than a toothed saw blade. Just score a little deeper each time instead of trying to cut through in one go. And have some extra blades on hand. I snapped off a few during the process. These utility knives are like $.59 at Harbor Freight and like $1.79 at the local hardware store.

    Now that the tubes are out, I'll block one port off with some plywood in the inside. The second port tube I'll cut off at 4". I wonder if a miter saw will make for a nice clean & square cut. I guess that we'll see. The good thing is I have a couple of extra tubes to experiment on since I only need one tube/port per speaker instead of 2.

    Once I'm done with the bondo, I'll spray the front (blue) and back (black) with Benjamin Moore Advance alkyd paint using my new HVLP gun before moving on to veneer. The bondo process for restoring all the edges and corners probably deserves it's own post but they did turn out good even though it took a while to do so many different surfaces.

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    Still sanding the front baffles which had a splatter finish on it.

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    How do I get the grill clips out without destroying them?

    I'm almost finished sanding but now I can't figure out how to remove the grill clips without destroying them. I could probably sand around them but I'm not going to be able to spray around them. Any suggestions?

    Thx

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    Senior Member grumpy's Avatar
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    Quote Originally Posted by David24x7 View Post
    I'm almost finished sanding but now I can't figure out how to remove the grill clips without destroying them. I could probably sand around them but I'm not going to be able to spray around them. Any suggestions?

    Thx
    The posts? They just come out (or break off).
    perhaps just mask off w/tape.
    Mine are gone, depending on Velcro in the corners now

  6. #6
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    If they are glued in, it won't be easy to get them out, sometimes a heat gun or similar will soften the glue enough to allow you to grab the post and twist it out. The original material sometimes gets brittle so it may snap one edge off. If the top breaks off flush, then use an Alden Grab-it or similar easy out to grab and pull out the remnant.

    The post can be replaced by used originals or the delrin repros that Ebay seller sign-shop sells, I've used them and they are nice but not inexpensive. But they do have the new grip that will hold the grilles on if you use them.
    When faced with another JBL find, Good mech986 says , JBL Fan mech986 says

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    Quote Originally Posted by mech986 View Post
    If they are glued in, it won't be easy to get them out, sometimes a heat gun or similar will soften the glue enough to allow you to grab the post and twist it out. The original material sometimes gets brittle so it may snap one edge off. If the top breaks off flush, then use an Alden Grab-it or similar easy out to grab and pull out the remnant.

    The post can be replaced by used originals or the delrin repros that Ebay seller sign-shop sells, I've used them and they are nice but not inexpensive. But they do have the new grip that will hold the grilles on if you use them.
    That's a good idea. I've been using pliers and vise grips and they aren't budging (but a couple of tips are snapping off). I was wondering how they were secured. I'll try the heat gun tomorrow and see if that helps. Good to know where to find replacements. Hopefully, i can finish sanding and filling this weekend. Thanks!

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    You have to pry out the grill clips

    Problem solved. To remove the grill clips from the 4320/4333 cabinets, you have to pry open some tabs. And I only had to destroy one clip to figure it out.

    Get yourself a penlight so you can see down in the hole, and a tiny flat bladed screwdriver and pry out the tiny recessed tabs on either side of the larger protruding tabs. The tabs are sharp and essentially grip the sides of the hole as you try to pull them out.

    Take a look at the pic and you'll see what I mean.

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    Senior Member grumpy's Avatar
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    Thanks for documenting with a pic! I remember seeing those but was fixated on the later plastic posts.
    Glad you figured it out.

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    Quote Originally Posted by grumpy View Post
    Thanks for documenting with a pic! I remember seeing those but was fixated on the later plastic posts.
    Glad you figured it out.
    It's the least I could do considering how helpful this forum and its members have been to me.

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    any updates? im about to start a 4333 build...how far are the holes for the woofer clips from the edge of the woofer's cut out?
    Semper Fidelis

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    Quote Originally Posted by ARMED View Post
    any updates? im about to start a 4333 build...how far are the holes for the woofer clips from the edge of the woofer's cut out?
    It looks like the holes are 1 1/4" from the edge of the woofer cut out.

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    The build is coming along slowly but I did get the fronts and backs painted. I used Advance from Benjamin Moore which is a hybrid water based alkyd paint. Turned out good but a little glossier than I wanted but Satin was the lowest sheen they had. Oh well, they look good and aren't original anyway (cabs were originally grey but had been sloppily painted over in brown).

    My challenge now is in sanding my edge banding flat against the already painted surface. If I were to do it all over again, I think I might veneer first and then mask off and paint second. Chalk it up to inexperience.

    Here is a pic taken just after painting. Hope to have some veneered pics up soon. Still haven't decided on a finish. Maybe Danish Oil but I'm leaning towards The Good Stuff (a synthetic oil finish) that I have used before with good results.

    What has everyone else used to finish new walnut veneer?

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    BTW - I found that a pop-up shade tent made for a nice spray booth when you wrap it with a little painters plastic.

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  15. #15
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    Brute Force, Old-School Port Tuning... Worked!

    NOTE: If you wish to journey far beyond my primitive methodology, Read Here:


    http://troelsgravesen.dk/vent_tuning.htm




    I built a pair of 5 cubic foot cabs for subs using 2235s. I used two 4" PVC tubes in each. Using the old JBL Enclosure Construction Guide, I estimated a rough-in value for port lengths, with an extra 1" in case the calcs might be off a bit.

    Finally used the tuning procedure in the guide which has a 1,000 ohm resistor in series with amp output, AF signal generator into the amp, and ac voltmeter across the loudspeaker terminals. Done at low power levels.

    Lastly I adjusted port lengths for the double notch response.

    I made the subs' low-pass network to be -3db at 125 Hz* with quality 10 mH inductor from Gold Sound in series with the driver, and a zoebel network from a JBL 3107 network (12 uf cap in series with a 10 ohm 25 watt resistor) connected across the driver.

    *125 Hz recommended in a project article in Speaker Builder magazine, using the 2235 or 2245.

    Hafler DH-220 amp for the subs. Alesis Matica 500 for the 4410s.

    With everything above 125Hz handled with 4410 monitors, IMO the low end response and in particular superb detail from the 2235's, they could not have sounded better.

    The high-pass function of -3db @ 125 Hz for the 4410's was implemented via a .022 uF polystyrene cap in series with each of the >125 Hz power amp's input RCA jacks, working into the amp's 22K ohm input impedance. Low to high range transition was seamless and first-order slopes adequate to work with the 2235 and the (now mid-bass) 127H's of the 4410s.



    The sound of the system did justice to the JBL Pro brand.

    Sorry for the thread divergence from just port size. The rest is just an example of what easily can be done as long as you have most excellent drivers to work with.

    Regards, -de-

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