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Apple Desktop Speakers Using Light Weight Cabinet Design

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  • Apple Desktop Speakers Using Light Weight Cabinet Design

    I'm in the process of building some desktop speakers for someone that will go with Apple products using my light weight cabinet design that I used on my Black Box speakers. I've made a few modifications to simplify the process, lighten the cab's some more and I am using a different bracing Technic.

    Each cabinet will have a single KEF 8” “Uni-Q” concentric driver (used in their Q900 speaker) rear mounted.

    This driver has the tweeter center mounted in the driver using the cone as a waveguide. I'll be doing the the crossover work. I will also be comparing the polar plots to my Black Box speakers which are waveguide loaded. should be interesting. I'll also get to do some listening to compare.

    Same baffle style as my black box speaker and it will get wrapped in light grey grill cloth. The baffle will be mounted from inside the cabinet with bolts.



    Recessed 1/8" into baffle.



    Light weight cabinet wall design.
    1/2" MDF with 2"x3/8" deep holes drilled. 1/4" plywood will get laminated on the inside. The cavities will get stuffed with Denim Insulation.







    Denim insulation



    I am using angle bracing so the center of the panels are braced from the corners and not just straight across. This should ad some rigidness to the cabinets. Bracing is 1/2" x 3/4" maple. Corner blocks are for mounting the baffle.



    I have 1/8" clearance from the bracing to the driver magnet. I'm thinking about shimming the space and run bracing back to the rear of the cabinet to help stiffen the driver.



    As for the finish I will be using the Alumi-blast paint that I used on my Panhead speakers for the rear panel and also along the four corners of the cabinet. The sides, top and bottom will get laminated with gloss white acrylic panels. The baffle will be covered in light gray cloth. The grill cloth is not as dark as the pics are showing. I couldn't seem to get a shot that would show the true color.





    The cabinets with bracing weigh 5lbs a piece not including baffle or rear panel. Same size cabinet in 3/4 MDF with no bracing or front and rear panel weighs 8lbs.


    Dave
    http://www.pellegreneacoustics.com/

    Trench Seam Method for MDF
    https://picasaweb.google.com/101632266659473725850

  • #2
    Re: Apple Desktop Speakers Using Light Weight Cabinet Design

    This looks really cool. I am working (I use that term liberally) on a desktop monitor with the smaller uni-q driver, and this is inspiring.

    Comment


    • #3
      Re: Apple Desktop Speakers Using Light Weight Cabinet Design

      Where did you source the woofer? I wasn't aware you could get the "tangerine" Uni-Q drivers unless you owned a pair and needed to order replacements from KEF. They are supposed to be the best performing coaxial available in many ways.

      I love the project. I built some "apple style" speakers years ago. It was designed to look kind of like an iPod. It was made from 1/4" thick aluminum on the sides with a lightly polished finish and the front and rear baffles were painted with a white acrylic gloss paint. They were pretty cool little speakers. I'll try to add a couple pics.

      It will be awesome to see measurements of that driver and pics of the final project.
      Loren Jones

      http://techtalk.parts-express.com/sh...-sound-drivers

      http://techtalk.parts-express.com/sh...for-live-sound

      Comment


      • #4
        Re: Apple Desktop Speakers Using Light Weight Cabinet Design

        This is an interesting build. I think I will subscribe to it as I would love to see your progress and get your listening impressions.

        While we are on the subject of "Apple Speaker" the link below is to a thread of some who built a pair of OS MTM's. I think the guy did a great job.

        http://techtalk.parts-express.com/sh...-Sensation-MTM
        Shaken, not stirred...

        Classix II
        OS MTM's
        Digger 8 sub
        Overnight Sensations Center Channel
        Sprite Build
        Wolf's PC Speakers
        Minions III with Voxel Sub

        Comment


        • #5
          Re: Apple Desktop Speakers Using Light Weight Cabinet Design

          Originally posted by davepellegrene View Post
          I'm in the process of building some desktop speakers for someone
          [raises hand]

          I'm excited that Dave chose to take this project on. While I had been paying attention to his waveguide work and measurements of various drivers, his Black Box design really stood out to me in all phases of design and execution as just an impeccable piece of work, based on his pictures, description of the design process, and published measurements. I'm really looking forward to seeing and hearing where the same thought processes and execution, combined with some of the most thoughtfully-engineered drive units I know of*, will lead. At worst, I know it will end up looking way better than any attempt of my own would, and probably sounding better too.

          I'd love to hear name ideas. One that strikes me as fun is "BBC," for "Black Box Concentric."

          The other major deviation from Dave's Black Box speakers is that the cabinets here are closed boxes. IMO, there's no point to venting the mains when one's using subs. Just don't gain anything. (I will be running these with a subwoofer.) Here, the F3 should be in the 70Hz neighborhood based on my measurements of the drive-units.

          Originally posted by davepellegrene View Post
          Each cabinet will have a single KEF 8” “Uni-Q” concentric driver (used in their Q900 speaker) rear mounted.
          To add some detail about the driver, it has an aluminum 8" cone and a concentric 1.5" (!) aluminum sandwich dome tweeter loaded with KEF's "Tangerine" phase plug. (Yes, their propaganda calls it a "waveguide," but it isn't. It's a phase plug and the cone is a waveguide. The Mark Dodd and Jack Oclee Brown AES paper on the current Uni-Q uses the correct term.)

          The voicecoil is a bit bigger than 2", so they can handle some power, though given the distance they won't need much. Other notable features of the drive unit are the strange surround shape, which necessitates rear-mounting (or a trim ring) and lossy mounting of the cone to the vc former. That damping collar does mitigate woofer breakup to some degree, but it's not nearly as effective here as it is in the smaller 5" Uni-Q KEF uses in their Q100 and X300, and that AJ used in his old Soundfield Audio Montior 1.

          Originally posted by davepellegrene View Post
          The cabinets with bracing weigh 5lbs a piece not including baffle or rear panel. Same size cabinet in 3/4 MDF with no bracing or front and rear panel weighs 8lbs.
          That's some pretty impressive mass savings!

          Originally posted by NickJ View Post
          This looks really cool. I am working (I use that term liberally) on a desktop monitor with the smaller uni-q driver, and this is inspiring.
          Incidentally, these speakers will be replacing a pair of the aforementioned SAM1's (0.75 ft^3 PE cabinet loaded with the 5" variant of this KEF concentric driver, and a TangBand W8-740 powered by a BASH 300W amp) on my desk. (Unlike with the SAM1's I will be running subwoofers with these speakers. The SAM1's are absolutely excellent speakers, but for my desk I wanted something to match the aesthetics of the other stuff on my desk, and the aesthetics of the desk itself. (It's a vintage George Nelson Action Desk, made by Herman Miller.) Also, I have another spot in mind for the SAM1's.

          They're going to be used behind my 24" monitor, on 18" steel stands.
          Last edited by Pallas; 08-09-2013, 05:27 PM. Reason: Fix URL of SAM1 show report
          --
          "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

          Comment


          • #6
            Re: Apple Desktop Speakers Using Light Weight Cabinet Design

            Originally posted by lorenmjones View Post
            Where did you source the woofer? I wasn't aware you could get the "tangerine" Uni-Q drivers unless you owned a pair and needed to order replacements from KEF. They are supposed to be the best performing coaxial available in many ways.
            Ditto, if you may divulge your sources. I mean I can't afford a pair right now but I can't help but be curious, in case I win a lottery or something.

            Comment


            • #7
              Re: Apple Desktop Speakers Using Light Weight Cabinet Design

              Originally posted by evilskillit View Post
              Ditto, if you may divulge your sources. I mean I can't afford a pair right now but I can't help but be curious, in case I win a lottery or something.
              I picked these up on eBay. They were actual KEF spares rather than harvested from Q900s, which IMO is a good thing because I think most sellers would botch the packaging. KEF ships replacement drivers with a plastic cap designed to protect the suspension and the front of the cone.

              I had a search on eBay going for a good two years before these popped up from a Canadian seller. He actually sold two pairs, but I was outbid on the first one. I won the second.

              On the plus side, I picked them up for considerably less than the official replacement driver cost of $225 or so + shipping. (Which, frankly, for the quality of the engineering and built, is a fairly reasonable price to begin with.) And I picked them up after Dave published his "Black Box" design.
              Last edited by Pallas; 08-21-2013, 05:30 PM.
              --
              "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

              Comment


              • #8
                Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                I have the woodworking done and two coats of Bin 123 on all the parts that are getting the Aluma-blast paint.



                Dave
                http://www.pellegreneacoustics.com/

                Trench Seam Method for MDF
                https://picasaweb.google.com/101632266659473725850

                Comment


                • #9
                  Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                  Looking oh so good!!
                  Loren Jones

                  http://techtalk.parts-express.com/sh...-sound-drivers

                  http://techtalk.parts-express.com/sh...for-live-sound

                  Comment


                  • #10
                    Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                    Originally posted by lorenmjones View Post
                    Where did you source the woofer?
                    I also found mine on Ebay, and ended up getting a great deal. They are quite good looking drivers, and I am hoping that some day (maybe after november), I can make some nice cabs for them, to make some nearfield monitors.

                    Comment


                    • #11
                      Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                      A little more progress

                      I recessed a spot for the Speakon connection to sit flush to the baffle.



                      Back of the baffle. Studs are through bolts since the baffle is getting covered with grill cloth. The dowels will line up with holes in the cabinet for a little more cabinet stability around the driver.



                      Alumi-blast paint applied.



                      I had the baffle painted white figuring it wold go best with the light grey grill cloth. What I didn't figure is the screw heads showed through the grill cloth. Painted black seams to hide them. I think it will also look better with the driver as well.



                      Driver mounted. I used a thick closed cell foam for the seal because the driver has a small rubber lip around where the surround meets the basket which I routed the hole so small for the basket to set down flush to the baffle. I didn't want to smash that lip so the thick foam took up the difference so I could draw the screws down tight. I guess it kind of decouples the driver from the box a little bit. I also put a fine bead of silicone around the grill cloth mostly so I wouldn't get leakage between the grill cloth and baffle but it will also assure the grill cloth will hold if the baffle ever needs removed.



                      Finished grill with driver mounted



                      I have the acrylic sides mounted to the cabinets and am waiting for the silicone to set up so I can clean them up. I'll post some pics when that happens.
                      Dave
                      http://www.pellegreneacoustics.com/

                      Trench Seam Method for MDF
                      https://picasaweb.google.com/101632266659473725850

                      Comment


                      • #12
                        Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                        Oh wow! That looks NICE!

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                        Comment


                        • #13
                          Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                          Originally posted by davepellegrene View Post
                          This driver has the tweeter center mounted in the driver using the cone as a waveguide. I'll be doing the the crossover work. I will also be comparing the polar plots to my Black Box speakers which are waveguide loaded. should be interesting. I'll also get to do some listening to compare.
                          Are you able to include intermodulation distortion measurements? The trade-off is something like better polar response for rougher frequency response and higher distortion due to the midwoofer cone motion modulating the tweeter output.

                          Comment


                          • #14
                            Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                            Thoughts on what to name them?

                            The best thing that's come to my mind is "BBC Monitors," with BBC standing for "Black Box Concentric."

                            Other things I've considered are "Q450" ("half a Q900"), "LS80" (riff on KEF LS50), and "DP80" or "PA80" (again riff on LS50).
                            --
                            "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

                            Comment


                            • #15
                              Re: Apple Desktop Speakers Using Light Weight Cabinet Design

                              Originally posted by andy19191 View Post
                              Are you able to include intermodulation distortion measurements? The trade-off is something like better polar response for rougher frequency response and higher distortion due to the midwoofer cone motion modulating the tweeter output.
                              I'm not sure but I am very curious on how the cone motion will effect the tweeter. I had thought about testing the tweeter by itself and then testing it with a lower frequency being played through the woofers cone to see how it effects it, if any. I would think it would only effect the lower frequencies of the tweeter and those waves may be large enough not to be bothered.

                              Dave
                              http://www.pellegreneacoustics.com/

                              Trench Seam Method for MDF
                              https://picasaweb.google.com/101632266659473725850

                              Comment

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