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Home Theater Overhaul: JBL Pro L/C/R Build

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  • Home Theater Overhaul: JBL Pro L/C/R Build

    EDIT: I realize some of these pictures are large. I didn't realize this until I had already uploaded them. So I apologize to those of you with a disdain for large image sizes. ;)


    This is a pretty simple build, relative to all the stuff I see here...

    Backstory:
    For the past year or so I've been working on my HT. I had a 110" screen, an Epson 8350 projector, my DIY 3-way Scan/Kef speakers, Kef r20c center, and some Kef Q100's for rear speakers. I 'completed' everything last summer.

    There were a few things that I didn't like about the room. Mainly, it didn't really have that "theater" vibe to it. I really didn't like floorstanding speakers in front of the screen (not physically blocking the view, but just forward of). I started thinking about the THX type baffle wall builds and really wanted to do something like that but I couldn't really justify it. Until...

    Around November a listing on Craigslist popped up. It had a lot of very nice JBL Pro Cinema gear. For practically free (literally) I obtained the following:
    (4) JBL 2035PHL 15" Woofers
    (4) JBL 2446J/2380A Compression Drivers/Horns
    (4) JBL 2330A Rear Speakers

    These all came from a theater which had closed down about 2.5 years ago. Some of the items were brand new and most were barely used.

    Now I have High Efficiency (the woofer is about 99dB @ 1w/1m efficient and the horns are ridiculously efficient at 111dB @ 1w/1m). I picked up all that and it gave me an excuse to build the baffle wall I'd been wanting to build. ;)
    yes, these will almost certainly be toed in by some degree (I'll have to get these in the room to determine that), which means the baffle wall sides will be angled to support this. The center channel is the only one which will be firing through an AT screen.

    I'll be going active 2-way on each of the speaker so I have better control of the response, with each channel driven by a channel of my Crown XLS1500's (I have three of these amps already).

    And this is where the build begins...
    ErinsAudioCorner.com

  • #2
    Re: Home Theater Overhaul: JBL Pro L/C/R Build

    I did some testing of the JBL 2035's and with help of Mayhem13 here I determined the optimal size to use for these.

    Here are the results of two of the 2035's impedance sweep:

    The first one was playing on the bench for about an hour at a low-mid volume. The second hasn't seen power in months, at least.

    #1:
    * Piston Diameter = 351.0 mm
    * f(s)= 56.52 Hz
    * R(e)= 3.98 Ohms
    * Z(max)= 34.30 Ohms
    * Q(ms)= 3.210
    * Q(es)= 0.421
    * Q(ts)= 0.373
    * V(as)= 130.600 liters (4.612 cubic feet)
    * L(e)= 0.85 mH
    * n(0)= 5.34 %
    * SPL= 99.38 1W/1m
    * M(ms)= 79.87 grams
    * C(ms)= 0.10 mm/N
    * BL= 16.38


    #2:
    * Piston Diameter = 351.0 mm
    * f(s)= 58.54 Hz
    * R(e)= 4.21 Ohms
    * Z(max)= 42.25 Ohms
    * Q(ms)= 3.581
    * Q(es)= 0.397
    * Q(ts)= 0.357
    * V(as)= 138.700 liters (4.897 cubic feet)
    * L(e)= 1.05 mH
    * n(0)= 6.68 %
    * SPL= 100.30 1W/1m
    * M(ms)= 70.12 grams
    * C(ms)= 0.11 mm/N
    * BL= 16.54


    ErinsAudioCorner.com

    Comment


    • #3
      Re: Home Theater Overhaul: JBL Pro L/C/R Build

      Modeling the response in various enclosures using BBP.


      This is just the #1 woofer.


      Red: JBL spec tuning/half box size (since it's one less woofer) @ 4 ft3, fb = 40hz

      Yellow = 3.84 ft3, fb 53hz

      Blue = 2.78 ft3, fb 60hz





      BBP let's me use an active filter as well so I just applied that to the 2.8ft3, fb 60hz model real quick.

      ErinsAudioCorner.com

      Comment


      • #4
        Re: Home Theater Overhaul: JBL Pro L/C/R Build

        I decided to go with the 4cube enclosure and these 4" ports. I finally got the time to assemble and route out the enclosures for the 15's. Each will house a JBL 2035HPL and will cover about 70-500hz for my L/C/R's. Fb is about 50hz, give or take. From 500hz and up, the horns will take over. The low end is all covered by the SI HT18's and JL 12TW1's.




        FWIW, I built the cabs from the PE 4cuft flat pack. I absolutely love that these things are available for guys like me (ie; guys who like to DIY but don't have the time to go buy all the wood and cut all the panels). They aren't as cheap to buy as they are to build but they save me a lot of time and effort so it's worth it to me to just go the flat-pack way. If I had to cut the wood for the enclosures, I'd probably only be half-way through just building one enclosure at this point. I put all three together in one day. I spent more time cutting out the speaker/port holes than assembling the cabs. Seriously.

        So now that the cabs are built the next step is to load each enclosure and run an impedance sweep so I can match the tuning frequency and try to get the best match I can. From there it'll be time to mate the big-ol' horn and start doing some testing to determine the best crossover point/levels/EQ to get the desired response. After that, they go upstairs and I start building the baffle wall.
        ErinsAudioCorner.com

        Comment


        • #5
          Re: Home Theater Overhaul: JBL Pro L/C/R Build

          Enclosures loaded and swept. Impedance matches pretty well on all of them (about 0.5 ohm difference on the odd-ball, which is fine since it's a straight level thing). The Qts values being different don't concern me at all because a) the differences are actually negligible, although the graph looks work and b) once the high pass filter is involved, these differences matter less.



          The resonances that show up at 700hz/1100hz are driver based; possibly edge or basket resonances... I'd have to measure distances to determine what it is exactly but it's not really important. The tuning frequency actually was lower than I was shooting for (which is fine) at ~45hz. I was shooting for 55hz but thinking there would be too much displacement with the bracing to achieve that, but it looks like there's a lot less than I had accounted for.

          The fronts were spray painted black so they wouldn't stick out (color wise) in the wall. Still, they will have black grill cloth over them as well as being covered with 2" wedge foam on the bare wood. Moral of the story: they ain't pretty but it doesn't matter. ;)











          I should also note the above impedance sweeps were done with the drivers simply sitting in place and not torqued down (I hadn't even drilled out the screw holes yet). I did this so I could swap out a driver or adjust the fill easily until I hit the desired spec in an effort to better match each speaker. Once torqued down the values will change somewhat. The goal was merely to match the speaker impedance as best I could.


          Next step is to set up the horns and start testing crossover options via the Helix.
          ErinsAudioCorner.com

          Comment


          • #6
            Re: Home Theater Overhaul: JBL Pro L/C/R Build

            On the first test, were the JBLs facing up, on a flat surface? If the vent was blocked that may explain the higher Fs- which seems to be lower in the 4 ft enclosures, the lowish Qms and higher Qts would tend to support that theory, though they may just be stiff from storage. Watching with interest- I have 2 dual 2035H bins I've been keeping, meaning to press into service. The 2035h has a copper sleeve through the pole, which seems to be effective up until 6-7k in your plots- making it easy to work with passively. It'll be interesting to see how those resonances play out- it might be a great candidate for some cone damping, though it may not really be needed.

            Comment


            • #7
              Re: Home Theater Overhaul: JBL Pro L/C/R Build

              I wish you would build a larger speaker at some point and time. those look great, this setup is going to make some mighty fine music.
              craigk

              " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

              Comment


              • #8
                Re: Home Theater Overhaul: JBL Pro L/C/R Build

                Originally posted by badman View Post
                On the first test, were the JBLs facing up, on a flat surface? If the vent was blocked that may explain the higher Fs- which seems to be lower in the 4 ft enclosures, the lowish Qms and higher Qts would tend to support that theory, though they may just be stiff from storage.
                when you say the "first test" you mean the two impedance sweeps at the beginning of the thread, correct? if so, those were done free-air, vertically. The last batch of testing was done in the enclosures in the manner you see pictured, so it's not really an apples to apples comparison.

                the resonances don't bother me too much as they're out of the intended pass-band. but I'm not saying they won't be an issue. I'm just hopeful they won't be.
                ErinsAudioCorner.com

                Comment


                • #9
                  Re: Home Theater Overhaul: JBL Pro L/C/R Build

                  After thinking about it, I'm not convinced the resonances I'm seeing in the impedance plot are driven by the surrounds. I just pulled up the JBL spec again for the 4638th (which uses a pair of 2035's so keep that in mind as you look at the varying data and realize the wild variances above beaming are likely due to this lobing) and you can indeed see the 700hz resonance cause a drop in output by about 6dB which seems to me to be a clear indication of a reflection; a distance of about 9.6 inches. So that may be something I can easily pinpoint. I have a couple ideas of what they are... I'll test those theories tonight. Either way, I don't think there's anything I can do. It will be interesting to test this, though.
                  ErinsAudioCorner.com

                  Comment


                  • #10
                    Re: Home Theater Overhaul: JBL Pro L/C/R Build

                    Originally posted by craigk View Post
                    I wish you would build a larger speaker at some point and time. those look great, this setup is going to make some mighty fine music.
                    what qualifies for "larger speaker"? this is a 15" midwoofer with a horn bigger than a bookshelf speaker. these are just L/C/R's. in the world of home audio, I'd say that's pretty dang large. ;)
                    ErinsAudioCorner.com

                    Comment


                    • #11
                      Re: Home Theater Overhaul: JBL Pro L/C/R Build

                      Oh, this is worth noting...

                      The JBL spec for the 4638TH cab tuning/half box size (since it's one less woofer) is as follows:
                      4 ft3, fb = 40hz

                      So, my enclosure being closer to about 3.7 and fb=45hz is actually really darn close to the JBL spec cab. Sweet!
                      ErinsAudioCorner.com

                      Comment


                      • #12
                        Re: Home Theater Overhaul: JBL Pro L/C/R Build

                        The dip on the 4638 spec sheet appears to be related to driver spacing, not driver acoustic performance- there's a 2 way with 2035h in their lineup (1 2035H) that doesn't show that dip.

                        Comment


                        • #13
                          Re: Home Theater Overhaul: JBL Pro L/C/R Build

                          Originally posted by badman View Post
                          The dip on the 4638 spec sheet appears to be related to driver spacing, not driver acoustic performance- there's a 2 way with 2035h in their lineup (1 2035H) that doesn't show that dip.
                          interesting that the resonance in impedance seems to occur at the same place the dip occurs, but doesn't show that dip in the single 2035 measurement you noted. Hmph.

                          Do you have a link to the single 2035 driver enclosure? I'm not too 'up' on the different types.


                          I did find the response for the 15" 2226 here which doesn't show that blip in impedance nor the dip in response:
                          https://www.jblpro.com/pages/pub/components/2226.pdf

                          The key being no blip in impedance.
                          ErinsAudioCorner.com

                          Comment


                          • #14
                            Re: Home Theater Overhaul: JBL Pro L/C/R Build

                            Originally posted by ErinH View Post
                            what qualifies for "larger speaker"? this is a 15" midwoofer with a horn bigger than a bookshelf speaker. these are just L/C/R's. in the world of home audio, I'd say that's pretty dang large. ;)
                            it's not big, it's large. I would like to hear these when they are completed.
                            craigk

                            " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

                            Comment


                            • #15
                              Re: Home Theater Overhaul: JBL Pro L/C/R Build

                              Originally posted by craigk View Post
                              it's not big, it's large. I would like to hear these when they are completed.
                              Ohio to my house... about 6-8 hours, ballpark (takes me 4.5 hours to get to Louisville). So, come on down! LOL.
                              ErinsAudioCorner.com

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