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  • The Against Protocol 3-way (AP3)

    Original build thread here: http://techtalk.parts-express.com/sh...light=protocol

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    I like this picture because it makes the speakers look gigantic, even though they are fairly small.

    This project came about from the desire to use the overachieving Vifa TC9 in a build. It is a great little driver with an easy to work with response and very nice distortion performance all at the low low cost of $12. I actually ended up buying my pair used from rpb last November for $10 IIRC and am just now getting around to using them. I picked up a pair of the Vifa XT25SC90 (small faceplate version of the XT25) in the classifieds to go with them for around $20 shipped. So then it came down to what woofer to use to make a nice 3-way. I debated for a while on what I wanted to do. I didn't really want to go with something pricey, since the rest of the build was so cheap. I also wanted something that could be stand-mounted to use in my bedroom (the eventual home of these). I looked around quite a bit and ended up deciding on another overachiever, the Dayton ND105-4. A lot of people tend to urge against going with small woofers for a 3-way, saying that you should either go with a good size woofer or just pick a pricier woofer for a 2-way due to costs. I definitely understand that logic, but here was my rational: The midrange on the TC9 is great and it is super cheap, but it definitely can't be used too low. The ND105 has crazy output potential for a 4" woofer due to its extremely large xmech and it plays down to 40hz in a roughly 7.5 liter cab. To get the combination of low extending bass and the midrange performance of the two, I would have had to go with a much more expensive, and probably larger driver, and a much larger cab in most cases. So going against the conventional wisdom on this, I decided to name them the Against Protocol 3-way, or AP3 for short. Total cost of the project using all poly caps except for the two largest values came out to just under $200 in parts. My total cost was about $150 since I got the ND105 on sale and the other drivers used.

    Paul Carmody mentioned in a thread about the Event Horizon design he was working on that it was difficult to work with the small woofers in a 3-way due to the higher Fs interfering with the crossover between the mid and woofer. I noticed this problem as well, and it took a bit of finagling to get it to play nice. The crossover ended up fairly straight forward in the end. Second order electrical on the woofer LP and on the mid HP and LP, and third order on the tweeter.

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    I didn't have a lot of time to voice these and measure before NY DIY and the end response surprised me a bit, as it looks kind of hot in the treble. I've had some time to go back and adjust some values to see if it sounded any better with the tweeter level down or the mid level a little higher and I have decided to leave them with the crossover I took to NY. Other variations just didn't sound right to me.

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    Comments on the sound: I got pretty good feedback on them from Roman at DIY NY, which I take as a pretty big compliment. Most of the comments from everyone were on the midrange clarity. Anyone who was at the event, feel free to comment with your thoughts, even if you think they sucked :D My thoughts are that the TC9 produces a really great midrange. Everything is detailed but still really smooth. You can see from the distortion measurements that the midrange through the top end is extremely clean. The vocal reproduction on these speakers is excellent. The phase aligned really well on these and tracks from the bottom end to the top end almost exactly on top of each other. I think this is what contributes to the really nice vocals and midrange sound. The bass is impressive for a speaker of this size and it's pretty amazing to hear how low these little ND105's can go. I was also really surprised that they could fill Roman's shop, which is pretty large, at the levels we were playing. I'll probably never have them up that loud again, but it's nice to know they can handle it.
    Last edited by Navy Guy; 02-11-2015, 04:30 PM.
    -Kerry

  • #2
    Re: The Against Protocol 3-way (AP3)

    I don't have access to a woodshop anymore and live in an apartment so I can't really cut anything here, but I can spray down in our parking garage and do other finishing and assembly in our dining room (my wife doesn't really like this though :D). I ended up having forum member joeybutts make the cabinets for me. Here is the drawing I provided him:

    outside dimensions.pdf

    He used this and some email exchanges with me to get the final product, which ended up being 6"W x 14"H x 10"D. The baffle is 1" thick MDF and everything else is 1/2" MDF. The drivers are rear mounted using a back plate that somehow Joey managed to make from some even more crudely drawn plans I sent him, but in essence, it press fits the mid and woofer into the back of the baffle with 1/4" of MDF between the frame and the face of the cabinet.

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    The mid chamber was created with a 5" to 4" PVC reducer. My initial plan was to try an open back mid configuration, which is why the second hole is in the middle of the back panel in the drawing above, but I started running short on time and it looked like it was going to take up too much space in the cabinet to get the bass performance I wanted out of the speaker. I ended up filling that hole with bondo and sealing up the 5" to 4" reducer after stuffing it with Ultratouch denim insulation.

    I lined the outside of the mid chamber and the walls of the box with vinyl damping material and then the top, bottom, and one side with Ultratouch. I used 2 of the 1.5" Goldwood ports stuffed flush end of one inside of the flared end of the other. This gave a length of about 7 1/4" and tuned the box to about 46hz. F3 of the design was 40hz, F6 36hz, and F10 31hz.

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    -Kerry

    Comment


    • #3
      Re: The Against Protocol 3-way (AP3)

      The insides were a little difficult to get everything to fit because of the small size of the cabinet. It took a bit of planning and test fitting to make sure it worked out.

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      After putting everything together on this, there are a few things I would recommend to anyone who wants to built this. The first would be to increase the width by 1/2" and add another 1/2" to the bottom of the cabinet, keeping driver placement the same from the top and centered. This is because I messed up when I sent the dimensions. The 5" to 4" PVC reduce is right at 5" outside diameter, so I basically left myself with no way to pull the back plate that held the mid and woofer out of the cabinet. The second would be to rabbit the back panel so that it fits without the addition of the plywood edging you can see on the inside of the back in my pictures. Again, this leaves you with no way to pull everything out. So if you ever want to remove the drivers after construction, you should follow this advice. Luckily, I like the way everything sounds and I think I'll be happy with these for a while.
      -Kerry

      Comment


      • #4
        Re: The Against Protocol 3-way (AP3)

        What a great looking speaker. Love the baffle and love the small 3-way concept.
        I think these would be a great choice for a smaller room like a bedroom or dorm and still give you the capability to rock when needed. ;-)

        You should add the build specs here, too.

        Keep it up, you are creating great stuff!
        Andy.

        Hah, you were reserving space while I was typing!

        Comment


        • #5
          Re: The Against Protocol 3-way (AP3)

          Originally posted by andykriech View Post
          What a great looking speaker. Love the baffle and love the small 3-way concept.
          I think these would be a great choice for a smaller room like a bedroom or dorm and still give you the capability to rock when needed. ;-)

          You should add the build specs here, too.

          Keep it up, you are creating great stuff!
          Andy.

          Hah, you were reserving space while I was typing!
          Thanks, Andy.

          Also edited the first post to fix the rotated crossover schematic.
          -Kerry

          Comment


          • #6
            Re: The Against Protocol 3-way (AP3)

            So cool--I love your Chotis too!

            Comment


            • #7
              Re: The Against Protocol 3-way (AP3)

              Originally posted by honfatboy View Post
              So cool--I love your Chotis too!
              Thanks!

              Also thought I would add that these can be built on a flat baffle (no facets) as long as you still fear mount the drivers 1/4" from the front and you will get pretty much the same results... Albeit not nearly as cool looking ;)
              -Kerry

              Comment


              • #8
                Re: The Against Protocol 3-way (AP3)

                I really like this! Well done! I bet it sounds great, each of those drivers has a lot to offer and the design really puts them together nicely!

                Comment


                • #9
                  Re: The Against Protocol 3-way (AP3)

                  Those look great. I love the baffles.

                  Comment


                  • #10
                    Re: The Against Protocol 3-way (AP3)

                    Nice work.

                    Comment


                    • #11
                      Re: The Against Protocol 3-way (AP3)

                      Nice conception, and nice delivery.
                      Funny, I'd been considering almost exactly the same drivers for a small 3 way starting about 6 months before you
                      posted the project. I changed to another woofer, but I'll be using your crossover as a starting point. I've had 6
                      of the TC9 drivers for forever. I like working on a smallish scale, but it certainly presents challenges, and can limit
                      your options in unforeseen ways. :eek:

                      I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                      "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                      High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                      SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                      My Voxel min sub Yet-another-Voxel-build

                      Tangband W6-sub

                      Comment


                      • #12
                        Re: The Against Protocol 3-way (AP3)

                        Originally posted by donradick View Post
                        Nice conception, and nice delivery.
                        Funny, I'd been considering almost exactly the same drivers for a small 3 way starting about 6 months before you
                        posted the project. I changed to another woofer, but I'll be using your crossover as a starting point. I've had 6
                        of the TC9 drivers for forever. I like working on a smallish scale, but it certainly presents challenges, and can limit
                        your options in unforeseen ways. :eek:
                        Thanks! I've had the mid and tweeter for almost a year now before finally getting this together. I think I bought the woofers about 8 months ago. Been too busy to get everything together. What woofer are you planning on using?
                        -Kerry

                        Comment


                        • #13
                          The Against Protocol 3-way (AP3)

                          Originally posted by dynamo View Post
                          I really like this! Well done! I bet it sounds great, each of those drivers has a lot to offer and the design really puts them together nicely!
                          Thanks! I really like the sound. I really can't explain how good the vocals sound. Even my parents while they were here for Thanksgiving noticed it without me saying anything. My mom kept saying "the voices sound so good."
                          -Kerry

                          Comment


                          • #14
                            Re: The Against Protocol 3-way (AP3)

                            Originally posted by Navy Guy View Post
                            Thanks! I've had the mid and tweeter for almost a year now before finally getting this together. I think I bought the woofers about 8 months ago. Been too busy to get everything together. What woofer are you planning on using?
                            I modeled the ND90, ND105, and a few others. Decided to do something a bit different, and bought the Peerless 830855 for the woofers.
                            peerless-830855-sds-4-woofer

                            I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                            "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                            High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                            SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                            My Voxel min sub Yet-another-Voxel-build

                            Tangband W6-sub

                            Comment


                            • #15
                              Re: The Against Protocol 3-way (AP3)

                              Originally posted by donradick View Post
                              I modeled the ND90, ND105, and a few others. Decided to do something a bit different, and bought the Peerless 830855 for the woofers.
                              peerless-830855-sds-4-woofer
                              What made you decide to go with the Peerless? I'm not knocking your choice, just wondering what design decisions you were making. I looked at that woofer but it didn't play low enough for me. I also looked at the B4n and the 4" TB in the Speedster. Someone else already used the TB 4" driver and it was also quite a bit more expensive than the other drivers I looked at. The B4n is cheap, but the ND105 looks better and plays just a bit lower, albeit in a slightly larger enclosure. For me it came down to how low it could play coupled with the huge xmech and the price (it was on sale for $18 when I got them).
                              -Kerry

                              Comment

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