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RS2-8T MTM RS225 RS28A Project

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  • #16
    Wow- that is -20dB, more than I expected. ROT is generally -25dB minimum down from reference, -40dB typically being much better and accepted as the normal reduction, and -50dB to no longer be an issue.

    Still- I like the look you have there! and the Adcom-rack is pretty cool...

    Later,
    Wolf
    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

    *InDIYana event website*

    Photobucket pages:
    http://photobucket.com/Wolf-Speakers_and_more

    My blog/writeups/thoughts here at PE:
    http://techtalk.parts-express.com/blog.php?u=4102

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    • #17
      Even at 2.6cf, it's not even close. Models show a 4"id x 5" long port to give you a tune of 40Hz. Your DATS clearly shows an Fb that's 10Hz lower. Still curiouser.
      To hit 30 your tube has to be at least twice its length.

      Now, if the actual id is only 3", then THAT would get you pretty close to 30Hz at a length of 5".

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      • #18
        Originally posted by Chris Roemer
        Even at 2.6cf, it's not even close. Models show a 4"id x 5" long port to give you a tune of 40Hz. Your DATS clearly shows an Fb that's 10Hz lower. Still curiouser. To hit 30 your tube has to be at least twice its length. Now, if the actual id is only 3", then THAT would get you pretty close to 30Hz at a length of 5".
        It's definitely a 4" ID tube, port is not close to any walls, etc. Granted it does have flares on each end and IME that throws off the typical simple modeled length. I have also found the models to always be quite a bit off when flares are taken into account. Sent from my iPhone using Tapatalk
        --
        Javad Shadzi
        Bay Area, CA

        2-Channel Stereo system in the works with Adcom components and 4-way towers

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        • #19
          Oddly enough I am working on a project right now with a single rs225 and dats is showing a tuning frequency lower than it should be for the port length as well.

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          • #20
            As Wolf says, I'd like to see the XO circuit design. I imagine the zobel is actually enlarged and is helping knock down the resonance of the 225 some.

            Looking at the bass performance I think this is yet another case where modeling as an MLTL would clue us in. I need to study that and post a report in regards to at what length ratio MLTL modeling is required for accuracy.
            Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
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            • #21
              Chris, didn't you or someone do a Dayton 8 redux crossover with these drivers a few years ago?

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              • #22
                Originally posted by JasonP View Post
                As Wolf says, I'd like to see the XO circuit design. I imagine the zobel is actually enlarged and is helping knock down the resonance of the 225 some.

                Looking at the bass performance I think this is yet another case where modeling as an MLTL would clue us in. I need to study that and post a report in regards to at what length ratio MLTL modeling is required for accuracy.
                Quite possible, those are pretty long boxes. Don't have my MLK Mathcad sheets handy, maybe Paul K will chime in. He of course recently did a MLTL based RS225 design (the Duets), and Ive been working on a similar one... Single driver, but the box proportions are similar. Well, probably a ways from MLTL optimal, but might explain the unexpected boost.

                OTOH, maybe a room node at that placement could do it, too... measuring the speaker in a different part of the room would tell for that.

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                • #23
                  Not sure if this will be helpful, but this is a (2) 225 MLTL I've been working on. Length is 48-3/4" with a 5"diameter port and F3 about 20Hz. SL is 13-1/2 by 20-3/4". Not small by any means. Guess if nothing else it shows what (2) 225 can do in a large'ish MLTL.
                  If life were fair, Elvis would still be alive today and all the impersonators would be dead.
                  ~ Johnny Carson

                  Bungelow Ed's Photo Album http://techtalk.parts-express.com/album.php?u=8594

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                  • #24
                    Originally posted by Wolf View Post
                    Javad-
                    I mean the FR plot of the woofer with it's xover, and the tweeter and it's xover disconnected. I know you said it was as simple as possible, and should meet the recipients needs, but I can imagine how much of a ringing headache that the RS225 can yield being the aluminum resonance is quite horrendous.

                    Later,
                    Wolf
                    Wolf I've been working on a new set of speakers (that I'm bringing to MWAF) and I've been doing extensive measuring and cross over tweaking, FWIW that measurement I posted for you was not near field but was from the listening position, about 6 feet back from the speaker. I'm finding nearfield measurements much more accurate by removing a lot of the room interaction, just wanted to be sure that I pointed that out to qualify that FR plot I sent you.
                    --
                    Javad Shadzi
                    Bay Area, CA

                    2-Channel Stereo system in the works with Adcom components and 4-way towers

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                    • #25
                      I wanted the midfield measurement as you posted,
                      Wolf
                      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                      *InDIYana event website*

                      Photobucket pages:
                      http://photobucket.com/Wolf-Speakers_and_more

                      My blog/writeups/thoughts here at PE:
                      http://techtalk.parts-express.com/blog.php?u=4102

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                      • #26
                        Jared, I would recommend that you try a bottomless notch filter, if you still can, to compare. My first build I did something similar with one of the smaller RS woofers and I thought it sounded great at first. The breakup was about 25 dB down. Then I built a revised version with the notch. The notch made for a much smoother presentation and in comparison the un-notched version sounded grainy. The distortion induced from the breakup and the response peak can be hard to pick up until you know what you are listening for. And the experiment only costs you a cheap cap (usually a value between 0.3-0.66 uF). And if you don't like it or don't hear the difference, it is only a couple dollars spent.
                        -Kerry

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                        • #27
                          Originally posted by Navy Guy
                          Jared, I would recommend that you try a bottomless notch filter, if you still can, to compare. My first build I did something similar with one of the smaller RS woofers and I thought it sounded great at first. The breakup was about 25 dB down. Then I built a revised version with the notch. The notch made for a much smoother presentation and in comparison the un-notched version sounded grainy. The distortion induced from the breakup and the response peak can be hard to pick up until you know what you are listening for. And the experiment only costs you a cheap cap (usually a value between 0.3-0.66 uF). And if you don't like it or don't hear the difference, it is only a couple dollars spent.
                          Thanks for the input! These were a pretty quick project for my brother and sounded great, he's very happy with them and I was very pleased with them as well but I just didn't have time to go too deep with the XO due to the time frame. If I decide to build another pair of these I'll definitely address the 8" come breakup issue and achieve an even flatter FR, thanks! Javad Sent from my iPhone using Tapatalk
                          --
                          Javad Shadzi
                          Bay Area, CA

                          2-Channel Stereo system in the works with Adcom components and 4-way towers

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                          • #28
                            Missed this thread the first time around. What I find interesting is that over the years talk of doing 2ways with the RS225 has progressed from DON'T DO IT, to Well Maybe But Cross Super Low and Still Not a Good Idea, to M'Kay Could Work. And yet whenever actual builds are done the feedback is consistently positive and gushing, with a range of crossover points. Seems to me that the 225 break up just isn't as bad as it's made out to be for making a 2way. I experimented briefly with a ~1400-ish XO w/ a SB29(or maybe the Satori since I have both, don't remember) and I really really liked what I heard. Contemplating doing a quad MMTMM 2.5way with them. Not so much for the bass but for the sheer displacement. Plenty of tweeters for the 1500-2K. Or even the DA32 even lower (and no, no waveguide. Tired of hearing about waveguides).

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                            • #29
                              I would love to do a big dual RS225 build like this to use as workshop/party speakers. They must have huge output capability, even if decidedly "mid-fi". JavadS did you care to share the XO?

                              Edit: Nvm, RS28A...

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