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Vintage 10" Sub build

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  • Vintage 10" Sub build

    For some time now I have been wanting to replace my old 12" MTX HT sub that I've been using for about 15 years. It is the first and only HT sub I have ever purchased, though as a cheap P.O.S. it has served me surprisingly well. After watching the video shared in this thread, I really liked the design aesthetic of the walnut/fabric combo and decided to adopt it for my next sub. I started on the design about 8 months ago and shortly after choosing my components everything went out of stock! For a looooooong time. Fast forward to now and parts are back in stock (albeit more expensive....S#!^^%$#) so I snatched them up and resumed some modeling to finalize my plans. After a few threads seeking some help (which is always appreciated!) I have come up with the following...
    Amp: SPA250DSP
    Subwoofer: Dayton Audio RSS265HF-4 10"
    Enclosure: 3 cu^ft tuned to 26Hz
    Port: 4" Flared Precision Port @ 13.7"

    Years ago I built a full set of Paul C's Swopes and this sub will be used along with them. I did not build those cabinets with the intention of ever putting grills on them and part of me wishes I had. While I like the look of the exposed drivers, my kids and their incessant need to touch, poke, drive Hot Wheels cars over everything has not been kind to them. That being the case I wanted to incorporate a grill over the sub driver to hide it and hopefully remove the temptation to destroy it . My plan is to build the cabinet with a front firing driver and recess it into the baffle enough so that I can wrap a band of acoustic fabric horizontally around the box to create a grill and still leave room for the woofer to dance. I'll need to take some measurements but my initial estimate from Dayton's drawings and the rated Xmax is that I'll need to recess the woofer about 1" to be safe. That means the baffle is going to be quite beefy.

    Here are the modeled graphs I have come up with so far...

    Transfer Function:

    Click image for larger version  Name:	tf_v1.jpg Views:	0 Size:	186.3 KB ID:	1482004

    Air Port Velocity:

    The port velocity is a little high. I plan to use a down-firing port and in one of my help seeking threads it was mentioned that the use of a down-firing port will filter out any chuffing that may occur (Thanks billfitzmaurice).
    Click image for larger version  Name:	apv_v1.jpg Views:	0 Size:	145.0 KB ID:	1482005

    Cone Excursion:

    I added a 25Hz HP filter to tame the excursion that starts to get real nutty around 23Hz and slightly over Xmax between 32-37Hz. With the filter everything appears OK.
    Click image for larger version  Name:	ce_v1.jpg Views:	0 Size:	164.7 KB ID:	1482006

    Next step is to put together some CAD drawings so I know what to cut. My plan is to do a substantial round-over (2") on the four vertical corners and then wrap the enclosure in a walnut veneer.

  • #2
    Nice driver choice. I might opt for a lower tuning, which should result in a bit less output at 30 Hz and a lot more at 20 Hz. Room gain should help to flatten the response a bit.
    Brian Steele
    www.diysubwoofers.org

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    • #3
      Originally posted by Brian Steele View Post
      Nice driver choice. I might opt for a lower tuning, which should result in a bit less output at 30 Hz and a lot more at 20 Hz. Room gain should help to flatten the response a bit.
      How low would you try and go? According to WinISD a tune of 22Hz would require a 20.3" port (or 21.3" for the Precision Port). The max useable length of the Precision Port I have is equivalent to a 17" port. I could go longer but I'm trying to avoid having to cobble the Precision Port together with standard ABS pipe. With the tuning I've got I shouldn't have to add in any 90s to the length of the port which makes fitting it in the enclosure a heck of a lot easier.

      I've also been reading lots of info that states the inside end of the port should be at least a port's diameter away from the inside of the enclosure. With the length I have now and the internal dimensions I'm planning on I'm right at 4" of clearance.

      Here's a transfer function graph comparing 22Hz to 26Hz. The red line is 22Hz, which as you mentioned, shows more output at 20Hz...

      Click image for larger version

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      • #4
        You can also dial in your intended low-pass to your mains. It'll change things a bit.

        Comment


        • #5
          As of now this is the enclosure design I was intending to go with. I am no Sketch-up wizard and I have no idea why some surfaces are different colors but this gives a good idea of driver, amp, and port placement along with some bracing. The baffle is 2 1/4" think so I can recess the woofer enough to where it won't touch the acoustic fabric grill (The outer recess in the baffle is 1" deep).

          All other sides are 1" thick while the bracing is 3/4". I'm planning to make the four corners by laminating four 3"x24" strips of MDF together and then ripping that down to a 2.5"x2.5"x24" piece. I'll then dado two opposite corners to the appropriate depth to accept a 3/4" piece of MDF where that adjoining side piece will be just proud of the corner piece surface it butts up to. I plan to then round over the outer corner with a 2" round-over bit which should then shave off the extra MDF of the two side pieces so I don't have to worry about getting them perfectly flush.

          Click image for larger version  Name:	vintage_sub_v1.png Views:	0 Size:	426.6 KB ID:	1482025Click image for larger version  Name:	vintage_sub_v2.png Views:	0 Size:	363.9 KB ID:	1482026

          Comment


          • #6
            Originally posted by unclejunebug View Post

            How low would you try and go? According to WinISD a tune of 22Hz would require a 20.3" port (or 21.3" for the Precision Port). The max useable length of the Precision Port I have is equivalent to a 17" port. I could go longer but I'm trying to avoid having to cobble the Precision Port together with standard ABS pipe
            You may be able to accomplish the lower Fb by just adding stuffing to the box. Something you can experiment with after building it.
            Brian Steele
            www.diysubwoofers.org

            Comment


            • #7
              Originally posted by Brian Steele View Post

              You may be able to accomplish the lower Fb by just adding stuffing to the box. Something you can experiment with after building it.
              Does that work for a ported box? I do plan to line the inside of the cabinet with dampening foam but that may not be the same thing as what you're suggesting.

              Comment


              • #8
                Originally posted by unclejunebug View Post

                Does that work for a ported box?
                Yes. Just don't over-stuff it. Use its measured impedance and frequency response as a guide to optimizing the stuffing.

                Brian Steele
                www.diysubwoofers.org

                Comment


                • #9
                  Originally posted by Brian Steele View Post

                  Yes. Just don't over-stuff it. Use its measured impedance and frequency response as a guide to optimizing the stuffing.
                  I guess I have a decision to make then. I was originally planning on internal dimensions of 19"x19"x18". After subtracting port, driver, and bracing volume this puts me right at about 3 cu^ft. Increasing internal dimensions to 20"x20"x20" would get me to about a net of 4 cu^ft and it really isn't that much larger of a finished box. If I go a little larger a 22Hz tune needs a 15.5" Precision Port which should fit. One thing I've also been trying to do is to be able to cover the enclosure with a single 4'x8' sheet of veneer. The larger box should still meet that requirement. Decisions, decisions...

                  Yellow line is 22Hz @ 4cu^ft
                  Red line is 26Hz @ 3cu^ft

                  Click image for larger version

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                  • #10
                    4 cu.ft. is a pretty large box for a 10" driver....
                    Brian Steele
                    www.diysubwoofers.org

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                    • #11
                      Originally posted by Brian Steele View Post
                      4 cu.ft. is a pretty large box for a 10" driver....
                      Fair enough. At this point I feel like I'm just throwing different parameters at it anyways. I originally started with a 2.5 cu^ft box and now I'm talking about a 4 cu^ft box.

                      From what I gather you're known as the subwoofer guy around here . If you were using this driver what size box would you shoot for?

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                      • #12
                        As I suggested in post #4, you should really throw your LP filter (to your mains) on this sim, as it changes things. IF this were a woofer in a 3-way, I wouldn't be so adamant about this, but it's not. A sub works over a much narrower bandwidth. For a 10"er, I TRY to get closer to 2cf, but some will greatly benefit from 3cf.

                        Comment


                        • #13
                          Originally posted by Chris Roemer View Post
                          As I suggested in post #4, you should really throw your LP filter (to your mains) on this sim, as it changes things. IF this were a woofer in a 3-way, I wouldn't be so adamant about this, but it's not. A sub works over a much narrower bandwidth. For a 10"er, I TRY to get closer to 2cf, but some will greatly benefit from 3cf.
                          I failed to mention in my original post that I also have a LP filter applied in the sim. It's currently set as a 2nd order @ 120Hz. Though to be perfectly honest, I'd have to check what's actually set on my receiver to see if it matches. Is this what you're referring to?

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                          • #14



                            Yes, sorry.
                            A more common Fc for a sub is 80Hz, but I'm typically more like 50 or even 40Hz (8" mains).

                            Comment


                            • #15
                              Originally posted by unclejunebug View Post
                              If you were using this driver what size box would you shoot for?
                              I'd probably go for the smaller box, and stuff it a bit until I got the response that I wanted. My current HT subwoofer is a 10" driver in a 2.5 cu.ft. box btw...
                              Brian Steele
                              www.diysubwoofers.org

                              Comment

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