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Ported and Sealed designs for Dayton RSS315 HF

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  • #16
    Yikes! That 8ohm vers. really wants a BIG box (pretty high Q there)!

    I've found gm's statement to not be true - at all. MOST (well designed) slot ports use 3 walls. I built one in the 4-1/2 foot range (52", maybe 56"). The slot config. MIGHT change the length by an inch or a few (prob'ly less than 5% in length). It's certainly NOthing like what gm states as a change of 10Hz. Mine might have missed the design freq by 1 or 2 Hz.

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    • #17
      Originally posted by Chris Roemer View Post
      Yikes! That 8ohm vers. really wants a BIG box (pretty high Q there)!

      I've found gm's statement to not be true - at all. MOST (well designed) slot ports use 3 walls. I built one in the 4-1/2 foot range (52", maybe 56"). The slot config. MIGHT change the length by an inch or a few (prob'ly less than 5% in length). It's certainly NOthing like what gm states as a change of 10Hz. Mine might have missed the design freq by 1 or 2 Hz.

      Yeah, I'm not too bothered by the cab size since it will be completely hidden.

      I'm a bit confused by all of this slot port talk. So are you guys saying it's best if I made the slot port as wide as the sub? i.e. If I am building the front face as 20x20, just add a 18.5" wide piece of MDF to the bottom as the slot?

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      • #18
        This was the HiVi SP10 driver. Very small box volume (VERY stiff suspension).

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        • #19
          Originally posted by Chris Roemer View Post
          This was the HiVi SP10 driver. Very small box volume (VERY stiff suspension).
          Sorry for the late reply. Crazy couple of days...

          Thanks for the image. That is a very cool port design. Might be too advanced for my novice skills lol

          Okay so I'm going to start off with the sealed build and if I need more I'll try ported.

          I have a new issue. I have NO clue what the resistor values are on my BASH500. I know they used to ship them stock with Fc of 30 Hz and then switched to 18 Hz which makes more sense for a sub.

          I bought this amp from someone so I have no ideas which stock it is.

          Is it easy to check? How do I check?

          I really hope the Fc is not 30 Hz. I would want to switch the resistors if it is. Which I also have no idea how to do.

          Any help is appreciated. Searching this topic online is super frustrating. Nobody seems to know the answer!

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          • #20
            I should also ask....what exactly is Fc? From all the forum chatter I'm assuming it's the same as the subsonic filter? Or is it something different?

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            • #21
              Fc is just the Frequency of the "c"rossover. Could be an HP, an LP, or really any freq. where one (type of) driver is handing off to another.

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              • #22
                Fc is the corner frequency of the filter.
                Craig

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                • #23
                  Thanks. So I guess it's where the HPF takes effect.

                  Going to have another look at the circuit board to see if I can figure it all out.

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                  • #24
                    Alright, here are the R17 (top) and R18 (bottom) resistors. If anyone can help me friggin figure out their values that would be great. I follow the colour guides online and don't get anything near what is in the BASH tables.

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                    • #25
                      Those look like 10k and 60k (trailing brown is 1% tolerance). That's the stock B500 boost of +2dB @ 38Hz.
                      That boost is more like a bad car sub than a lower boost for HT.

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                      • #26
                        Originally posted by Chris Roemer View Post
                        Those look like 10k and 60k (trailing brown is 1% tolerance). That's the stock B500 boost of +2dB @ 38Hz.
                        That boost is more like a bad car sub than a lower boost for HT.

                        That really sucks. I am less concerned about the bass boost and more about the Filter Fc of 30 Hz. Why it would be that high for a subwoofer amp, I have no idea.

                        I think I will measure the in-room response and then decide what to do.

                        Chris, any idea how difficult it is to mod this amp?

                        It will be very tough for me to sell it and buy something else. The market here in Canada for these things is almost non-existant.

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                        • #27
                          Have you looked at the boost table? By LEAVING the 10kohm resistor in place, you can just change the 60k one to:
                          68k - for +3dB @ 33Hz, Fc = 28Hz
                          100k - for +4dB @ 28Hz, Fc = 23Hz
                          150k - for +5dB @ 22Hz, Fc = 19Hz

                          I'd probably pick the last alignment. IMO ANY of these boost changes would mean you'd want to go sealed.
                          I think 4cf would get you down to 25Hz.

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                          • #28
                            Originally posted by Chris Roemer View Post
                            Have you looked at the boost table? By LEAVING the 10kohm resistor in place, you can just change the 60k one to:
                            68k - for +3dB @ 33Hz, Fc = 28Hz
                            100k - for +4dB @ 28Hz, Fc = 23Hz
                            150k - for +5dB @ 22Hz, Fc = 19Hz

                            I'd probably pick the last alignment. IMO ANY of these boost changes would mean you'd want to go sealed.
                            I think 4cf would get you down to 25Hz.

                            I had the exact same thought. Would only need 1 resistor change.

                            I am going to run some measurements in my room tonight and see what the response curve looks like. I'll then determine where I need the boost. Will post results shortly.

                            When I model the driver, a 4 dB boost at 30 Hz actually gives the best looking response. Looks more like a ported design than sealed. We'll see what it looks like in room before deciding.

                            I appreciate the input by the way, very helpful.

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                            • #29
                              My son has a fever and I am in survival mode. Might not be able to test until Monday. Damn life getting in the way of my hobby!!! :P

                              I also started thinking about, if I do ported, how would that change which resistors I wanted. I don't think I could be this aggressive with the boost, but would have to lower the HPF for sure.

                              I wonder why all of us DIYers have OCD and ADD....maybe that's why we enjoy this...

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                              • #30
                                Chris Roemer Okay so I did some testing and the sub hits on average 105 dB across the frequencies, with a sharp drop after 30 Hz, to be expected. The F3 is probably about 25 Hz. Not bad.

                                After modeling the sealed design with the different bass boosts down low, it looks like the cone excursion gets a little crazy and I don't know if it would be a good idea.

                                I will build a vented box this week and see how it compares.

                                I am also wondering, it may be possible for me to straight up trade someone the BASH500 for a 300. If I get another HF 12" 8 ohm and wire them in series I would get the full 300 watts from the amp. Which should be enough for these drivers.

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