Announcement

Collapse
No announcement yet.

OT ... How do you design a enclosure when you don't know the...

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • OT ... How do you design a enclosure when you don't know the...

    Guys, going through some of my old junk and came across a Logitech 2.1 where the amp board appears to have karked it. They are only 2.5inch drivers which are 8ohm and that's about all I know about them

    As they are about to be taken to the "big garbage bin in the sky", I would like the construct a maze inspired enclosure, which I'm guessing would be a t line or horn. Honestly just want to use my router and do some.layers.

    How does one design something when the specs are unknown? I don't have a have a mic either..

    All I would like to do is use scrap timber and upcycle these speakers, then spend a little amount of cash on a small amp board (maybe DTA 2 again)

    Attached Files

  • #2
    It's said you can use the (free) ARTA "suite" and a cobbled together test jig (maybe $5-$10?) to derive T/S parms. In reality (unless they're extraordinary 2-1/2" drivers, like ND65s) it probably won't matter much what kind of box you put them in.

    Comment


    • #3
      If you are goofing around pick another 2.5 inch driver and use that for your modeling. Rough estimate...for a tapered t-line pick a starting area near 3 x sd and a length at 1/4 wavelength 40 hz equals about 7 feet. Use a terminus/ leaving area of 1/2 sd.
      John H

      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

      Comment


      • #4
        Originally posted by Chris Roemer View Post
        It's said you can use the (free) ARTA "suite" and a cobbled together test jig (maybe $5-$10?) to derive T/S parms. In reality (unless they're extraordinary 2-1/2" drivers, like ND65s) it probably won't matter much what kind of box you put them in.
        I don't think I would compare against the ND's, they get a great rap. Honestly they sounded pretty good when coupled with the powered sub and served me well for over a decade, but not expecting the world when away from the bass support

        edit: just found the operating manual..interesting power output for the size of them.

        Attached Files
        Last edited by 3rutu5; 12-25-2018, 04:16 AM.

        Comment


        • #5
          Originally posted by 3rutu5 View Post
          I don't think I would compare against the ND's, they get a great rap. Honestly they sounded pretty good when coupled with the powered sub and served me well for over a decade, but not expecting the world when away from the bass support

          edit: just found the operating manual..interesting power output for the size of them.
          The reality (not knocking your stuff) is more like 10 watts to the sats and maybe 40-50 to the sub.
          Stuff like that is highly exaggerated and is usually not very reliable.

          Comment


          • #6
            Yeah listing power at 1k/10%THD is really overrating real world power. Think back to the Pyramid amps of the late 80's.

            Comment


            • #7
              Originally posted by kevintomb View Post

              The reality (not knocking your stuff) is more like 10 watts to the sats and maybe 40-50 to the sub.
              Stuff like that is highly exaggerated and is usually not very reliable.
              On another site, somebody found this

              Fs = 42.95 Hz
              Re = 7.80 ohms [dc]
              Le = 7328.42 uH
              L2 = 3120.63 uH
              R2 = 52.25 ohms
              Qt = 0.52
              Qes = 0.57
              Qms = 6.49
              Mms = 50.81 grams
              Rms = 2.112233 kg / s
              Cms = 0.000270 m / N
              Vas = 10.35 liters
              Sd = 165.13 cm ^ 2
              Bl = 13.755757 Tm
              ETA = 0.14%
              Lp (2.83V/1m) = 83.66 dB

              http://www.tomsguide.com/forum/57164...ch-2300-titans. Not sure where these figures were pluckef out from or if they are just made up.

              Which got me slightly excited until I saw the fs and vas, SD....
              Although they listed it under satellite, it is clearly referring to the 8" sub.

              I agree completely with the fact that there is some exaggeration from the manufacturer and most likely bogus. When I bought these ones they were about 200 aud and capable of performing loud and able to rattle the light fittings in the house with bass heavy music, but I have no real idea how the speakers will operate on their own without the sub. Not knowing alot about this stuff, I would image that the fs is probably around 120-150 hz looking at other 2.5" full range drivers around

              I was having a look last night with some calipers and ended up assuming a SD of 32cm2

              Comment


              • #8
                Originally posted by jhollander View Post
                If you are goofing around pick another 2.5 inch driver and use that for your modeling. Rough estimate...for a tapered t-line pick a starting area near 3 x sd and a length at 1/4 wavelength 40 hz equals about 7 feet. Use a terminus/ leaving area of 1/2 sd.
                Pretty much goofing around on this one, hence why I have a budget of zero bucks on the speaker build so I guess a 1/4 wave length for 100hz would be about 2-2.5ft and would need a throat of 16cm2, roughly speaking.

                If it sounds alright I'll get a small amp board to power them..

                Comment


                • #9
                  John, if you use a line tapered at 6:1 as you suggest and want its 1/4-wavelength resonant frequency to be 40 Hz, its length need to be only ~58" long. If the line were not tapered, a length of ~84" would be correct for the same 1/4-wave resonant frequency. A negatively tapered line has two advantages over an equivalent line having a constant area. The line can be shorter for the same 1/4-wave resonance, and the overall response shape will be smoother.

                  3rutu5, if you want a 100-Hz 1/4-wave resonant frequency with a taper of 6:1 as John suggests, the actual length needs to be ~24". For a non-tapered line with the same 1/4-wave resonance, the length would need to be ~34". A beginning (throat) area of 3 Sd with the tapered line might or might not be optimum, and the only way to know for sure is to model the line with T/S values appropriate for the driver of choice with an accurate TL modeling program. Also, where the driver is located along the line's length greatly impacts the results.
                  Paul

                  Originally posted by jhollander View Post
                  If you are goofing around pick another 2.5 inch driver and use that for your modeling. Rough estimate...for a tapered t-line pick a starting area near 3 x sd and a length at 1/4 wavelength 40 hz equals about 7 feet. Use a terminus/ leaving area of 1/2 sd.

                  Comment


                  • #10
                    Are the ports on those satellites fake as the second picture suggests (it looks like the port is sealed off)?
                    Brian Steele
                    www.diysubwoofers.org

                    Comment


                    • #11
                      Thank you Paul, it's good to have someone who knows TLs give some better guidance!
                      Last edited by jhollander; 12-25-2018, 10:29 PM. Reason: spelling
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #12
                        Originally posted by Brian Steele View Post
                        Are the ports on those satellites fake as the second picture suggests (it looks like the port is sealed off)?
                        Correct big old fakies....to think I didn't notice it was sealed for 10 years, they use to have grills over them

                        Comment


                        • #13
                          Originally posted by Paul K. View Post
                          John, if you use a line tapered at 6:1 as you suggest and want its 1/4-wavelength resonant frequency to be 40 Hz, its length need to be only ~58" long. If the line were not tapered, a length of ~84" would be correct for the same 1/4-wave resonant frequency. A negatively tapered line has two advantages over an equivalent line having a constant area. The line can be shorter for the same 1/4-wave resonance, and the overall response shape will be smoother.

                          3rutu5, if you want a 100-Hz 1/4-wave resonant frequency with a taper of 6:1 as John suggests, the actual length needs to be ~24". For a non-tapered line with the same 1/4-wave resonance, the length would need to be ~34". A beginning (throat) area of 3 Sd with the tapered line might or might not be optimum, and the only way to know for sure is to model the line with T/S values appropriate for the driver of choice with an accurate TL modeling program. Also, where the driver is located along the line's length greatly impacts the results.
                          Paul
                          Cheers, I made a jig before with some.scrap timber, also inspired by YouTube e and a high probability that this is crap, I can get a lenthl upwards of a meter in a relatively small box. Please chime in if this a bastardized t line that insults the masses...the flush cut bit I wanted to use will put.a rounded edge at all bends

                          I got.all.the way to the end and realized I left out a space for.the amp
                          Attached Files

                          Comment


                          • #14
                            Actially I have a different idea using a router. I'm almost finished a tv/hifi unit, so will look at this little side project afterwards, so feel free to tell me if im on the wrong track

                            Comment


                            • #15
                              In your drawings I assume the driver is located in the upper left corner in the large area, which is the beginning of the line? As to comments, you're shooting for a 1/4-wave resonance of 100 Hz, right? If you are, that will be appropriate for a driver with a 100 Hz fs if its Qts is equal or close to 0.4. If the driver's Qts is appreciably lower than 0.4, the tuning frequency will need to be higher than 100 Hz, and if Qts is appreciably higher than 0.4, the tuning frequency will need to be lower than 100 Hz. Of course, if fs is something other than 100 Hz, that changes requirements in addition to the Qts value. Unless one is building a subwoofer that's crossed pretty low, locating a driver at the very beginning of a line usually ends up having a pretty big dip in the response in the 100 to 300 Hz range. It's always better to locate the driver at either ~20% or ~33% of the line's length from the line's beginning. I'd be happy to model a TL for you but would need reasonably representative T/S values for the driver: fs, Re, Le, Bl, Sd, Vas, Qes and Qms (if you have only Bl or only Vas along with the other parameter values I can accurately calculate either Vas or Bl, respectively).
                              Paul

                              Originally posted by 3rutu5 View Post
                              Actially I have a different idea using a router. I'm almost finished a tv/hifi unit, so will look at this little side project afterwards, so feel free to tell me if im on the wrong track

                              Comment

                              Working...
                              X