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  • GRS Project finished.

    Got it done, for what it is worth. I present to you "Cabrini", named after the patron saint of orphans. The drivers used in this project are orphans of a sort, so I thought the name was fitting.

    First, some explanation of the frequency response: Yes, I am aware it is not very flat. The tweeter has a very ragged response, but overall the dips and peaks in the treble are represented about equally, and there are no peaks that are of a serious magnitude above the reference. I decided that sins of omission are more forgivable than sins of commission. With that being said, here are the measurements:



    Included in those measurements are raw, on-baffle measurements. Not SPL accurate. Crossover is 3rd order BW on woofer and tweeter at ~2800 Hz. The only real problem area is the broad dip around 5k-8k, but fixing that would require more components than the tweeter is worth. It gives it a laid back sound and minimizes the "cupped hands" effect.

    The crossover is simple, with a first order electrical plus zobel on the woofer, and an L-Pad on the tweeter. Five components, three of which are resistors



    I used the cheapest components I could find at PE.

    Here is a snapshot of the final build:



    External dimensions are 9.25"w x 15"h x 8"d, all 3/4" MDF with no bracing etc inside. This nets 0.38 cubic feet sealed. Stuffed with 6 ounces of Walmart polyfil.

    Upgrades: Brace it. Flush mount the drivers. Chamfer the inside of the woofer cutout. Add a roundover on the front baffle. Build it as a small tower of about 1.5 cubic feet, or wait for instructions for the bass bin upgrade using the 12" GRS poly woofer. I now have reason to build that bass bin, so it will be done in a short time.

    Overall, the GRS woofer meets my expectations and even exceeds it in some areas. There is no cone breakup (as advertised). It is attractive, and has very little linear distortion. I did not do non-linear distortion measurements on this, but subjectively it has high distortion below 200 Hz and above 3k. Otherwise, it is similar to the Goldwood driver of which I am now sure it is based on (at least in part).
    Don't listen to me - I have not sold any $150,000 speakers.

  • #2
    Re: GRS Project finished.

    Johnny, that turned out great.

    Comment


    • #3
      Re: GRS Project finished.

      Johnny, what did the total $$$ work out to, less boxes?

      John

      Comment


      • #4
        Re: GRS Project finished.


        Add another dollar for the two other 8.2 ohm resistors.
        Don't listen to me - I have not sold any $150,000 speakers.

        Comment


        • #5
          Re: GRS Project finished.

          nicely done. and with the discounts, you can do 5 for 90 bucks. that's hard to beat.
          TM (RS125/TB25-302), TM RS150S / Vifa BC25SC06, RS150-4 / Vifa ML-TL, 3CR-AL Ultra Budget: Electric Blue TM, TMM, MTM, Dragonflies , Mounties: Mini HT Satellite,sub for minions

          Comment


          • #6
            Re: GRS Project finished.

            Originally posted by johnnyrichards View Post
            Got it done, for what it is worth. I present to you "Cabrini", named after the patron saint of orphans. The drivers used in this project are orphans of a sort, so I thought the name was fitting.

            First, some explanation of the frequency response: Yes, I am aware it is not very flat. The tweeter has a very ragged response, but overall the dips and peaks in the treble are represented about equally, and there are no peaks that are of a serious magnitude above the reference. I decided that sins of omission are more forgivable than sins of commission. With that being said, here are the measurements:



            Included in those measurements are raw, on-baffle measurements. Not SPL accurate. Crossover is 3rd order BW on woofer and tweeter at ~2800 Hz. The only real problem area is the broad dip around 5k-8k, but fixing that would require more components than the tweeter is worth. It gives it a laid back sound and minimizes the "cupped hands" effect.

            The crossover is simple, with a first order electrical plus zobel on the woofer, and an L-Pad on the tweeter. Five components, three of which are resistors



            I used the cheapest components I could find at PE.

            Here is a snapshot of the final build:



            External dimensions are 9.25"w x 15"h x 8"d, all 3/4" MDF with no bracing etc inside. This nets 0.38 cubic feet sealed. Stuffed with 6 ounces of Walmart polyfil.

            Upgrades: Brace it. Flush mount the drivers. Chamfer the inside of the woofer cutout. Add a roundover on the front baffle. Build it as a small tower of about 1.5 cubic feet, or wait for instructions for the bass bin upgrade using the 12" GRS poly woofer. I now have reason to build that bass bin, so it will be done in a short time.

            Overall, the GRS woofer meets my expectations and even exceeds it in some areas. There is no cone breakup (as advertised). It is attractive, and has very little linear distortion. I did not do non-linear distortion measurements on this, but subjectively it has high distortion below 200 Hz and above 3k. Otherwise, it is similar to the Goldwood driver of which I am now sure it is based on (at least in part).
            Nice! For 40 bucks, can't beat that. I know I wouldn't mind the dip at 5-8k. My speakers always seem hot in that area and it drives me nuts. Well at least that's where the Rat Shack meter says it's hot. Nice job. Robert.

            Comment


            • #7
              Re: GRS Project finished.

              do you have the final (with BSC + Box tuning) FRD and ZMAs, I'd like to see what I can do with PCD, thanks!

              I'll be building some of these when I get home for sure!

              रेतुर्न तो थे स्रोत
              return to the source
              leviathan system thread
              deadhorse thread
              shockwave build thread

              instagram :: greywarden_13

              in war, victory . . . in peace, vigilance . . . in death, sacrifice.

              Comment


              • #8
                Re: GRS Project finished.

                Sweet! How's their "pumpitude" compared to commercial $40 offerings?

                Comment


                • #9
                  Re: GRS Project finished.

                  Johnny, thanks for all your work and for passing along the information to all of us. I would compare this project to a person's car. Yeah, there's all kinds of cars I would love to drive, but the economical realities are that I'm limited to pretty low-cost, used cars. So, with that mighty constraint, what's the best transportation I can obtain and use, while maximizing the reliability, comfort (A/C down here in Alabama), fuel economy, etc.

                  Well, if my financial situation at the moment requires low-cost speakers, what can I get/do to maximize my enjoyment of designing, building, and using the speakers? This is a great service to your fellow DIYers, especially in the current economy.

                  Comment


                  • #10
                    Re: GRS Project finished.

                    do you have the final (with BSC + Box tuning) FRD and ZMAs, I'd like to see what I can do with PCD, thanks!

                    I'll be building some of these when I get home for sure!
                    Kind of... My files are not really super usable outside of my environment but I do have them.

                    Sweet! How's their "pumpitude" compared to commercial $40 offerings?
                    Bass-wise, not good. Otherwise - they match most of the cheaper stuff I have heard. If a guy was to do all the upgrades I listed, than they will definitely meet or exceed the sub-$100 stuff at Best Buy and the like. As is, I think they are competitive with some of the ultra-budget commercial stuff, but there is just no getting around the economy of scale. This project was aimed more towards people wanting to get into DIY without any serious financial outlay. This hobby isn't for everyone, this project will let someone know if it is something they want to do.

                    Johnny, thanks for all your work and for passing along the information to all of us. I would compare this project to a person's car. Yeah, there's all kinds of cars I would love to drive, but the economical realities are that I'm limited to pretty low-cost, used cars. So, with that mighty constraint, what's the best transportation I can obtain and use, while maximizing the reliability, comfort (A/C down here in Alabama), fuel economy, etc.

                    Well, if my financial situation at the moment requires low-cost speakers, what can I get/do to maximize my enjoyment of designing, building, and using the speakers? This is a great service to your fellow DIYers, especially in the current economy.
                    Thank you for the kind words and recognizing that sometimes life is about making compromises you can live with, including DIY audio. These can be built with a screwdriver, a jigsaw and a Skil-saw at the minimum. It is all about creating a project to let newbies practice without paying for it. Even if they do not have the basic tools, odds are they know someone who does.
                    Don't listen to me - I have not sold any $150,000 speakers.

                    Comment


                    • #11
                      Re: GRS Project finished.

                      Johnny,

                      Well done. I think this project tancends strictly sonics and DIY's a much better aspect of the hobby.
                      .

                      Comment


                      • #12
                        Re: GRS Project finished.

                        This project was aimed more towards people wanting to get into DIY without any serious financial outlay. This hobby isn't for everyone, this project will let someone know if it is something they want to do.

                        Good on you! Johnny

                        Tim

                        Comment


                        • #13
                          Re: GRS Project finished.

                          How in the "Wide World of Sports" do you find time to do all that you do Johnny???
                          Craig

                          I drive way too fast to worry about cholesterol.

                          Comment


                          • #14
                            Re: GRS Project finished.

                            Originally posted by PWR RYD View Post
                            How in the "Wide World of Sports" do you find time to do all that you do Johnny???
                            I have a touch of mania (don't we all lol), so when the spell is on me I will put in a twenty hour day or three. Plus, my daughter is now helping me with things and I leave the final voicing to my wife - her ears are better. My daughter helped me this go around by grabbing me crossover parts. I taught her how to read the component values and the difference between inductors, resistors and capacitors. This was a lot of fun. I showed her what sound "looks" like with the measurements, and then we lost about an hour of production time when her and I started goofing off with the mic and ARTA :D I now know what a dog bark, a 10 year old scream, a door slam and "I love you daddy" looks like on ARTA. Time well spent!
                            Don't listen to me - I have not sold any $150,000 speakers.

                            Comment


                            • #15
                              Re: GRS Project finished.

                              Originally posted by mzisserson View Post
                              Johnny,

                              Well done. I think this project tancends strictly sonics and DIY's a much better aspect of the hobby.
                              Exactly.
                              Don't listen to me - I have not sold any $150,000 speakers.

                              Comment

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