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  • TMM or MTM?

    [There are two questions at the very bottom, feel free to skip over the intervening "good news/bad news" verbage :D ]

    I've been working on my Gila Monsters (link below in my sig) this week. Made a few small adjustments to the xover, and I think things are about as good as they're going to get with my design (they do sound very good).

    Here's the bad news: I made the mistake of modeling the xover with an RS28A. Well, after looking at the graphs, as far as I can tell, I'm now morally obligated to buy a pair of RS28A.

    OK, the good news is, the RS28A are very nearly a physical drop-in replacement for my existing baffle. Woo hoo!

    Well, hold on, not so fast, I happen to have an extra pair of 831735 drivers sitting on the shelf. And, an MTM version of the xover models even simpler and easier than the MT. Sigh....

    I've attached a mock-up photo of what a TMM and an MTM might look like (I'd also like to relocate the port to the front baffle, as well). I like the look of the MTM. However, the TMM would place the tweeter closer to seated listener height.

    I (finally) have two questions:

    (1) Is there any difference in crossover between a 2-way TMM and MTM?

    (2) Should I consider a 2.5-way instead of a 2-way?
    Attached Files

  • #2
    Re: TMM or MTM?

    Originally posted by 50 watt head View Post
    [There are two questions at the very bottom, feel free to skip over the intervening "good news/bad news" verbage :D ]

    I've been working on my Gila Monsters (link below in my sig) this week. Made a few small adjustments to the xover, and I think things are about as good as they're going to get with my design (they do sound very good).

    Here's the bad news: I made the mistake of modeling the xover with an RS28A. Well, after looking at the graphs, as far as I can tell, I'm now morally obligated to buy a pair of RS28A.

    OK, the good news is, the RS28A are very nearly a physical drop-in replacement for my existing baffle. Woo hoo!

    Well, hold on, not so fast, I happen to have an extra pair of 831735 drivers sitting on the shelf. And, an MTM version of the xover models even simpler and easier than the MT. Sigh....

    I've attached a mock-up photo of what a TMM and an MTM might look like (I'd also like to relocate the port to the front baffle, as well). I like the look of the MTM. However, the TMM would place the tweeter closer to seated listener height.

    I (finally) have two questions:

    (1) Is there any difference in crossover between a 2-way TMM and MTM?

    (2) Should I consider a 2.5-way instead of a 2-way?
    You could potentially use a 2 way crossover in an in the TMM alignment but that opens up the possibility having comb filtering to contend with. Of the two options I'd probably go with a 2.5 way crossover to get the tweeter closer to ear level.

    Another thing to think about is you'll want to double the enclosures volume since you're going to add a second woofer which would mean making a new cab. So if you wanted to build it as an MTM you could build it as a taller floor standing speaker to get the tweeter closer to ear level.

    The third option which isn't a bad one is keeping the BC25 tweeter in them after all you do like the way they sound.

    Take it easy
    Jay
    "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

    Breakfast Stout - HiVi RT2 II/Aurasound NS6
    Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
    Ruination 2.5 way - Vifa DX25/Fountek FW168
    Levitation TM
    - Vifa BC25SG15/Fountek FW168

    Comment


    • #3
      Re: TMM or MTM?

      Originally posted by Brewski View Post
      You could potentially use a 2 way crossover in an in the TMM alignment but that opens up the possibility having comb filtering to contend with. Of the two options I'd probably go with a 2.5 way crossover to get th tweeter closer to ear level.

      Another thing to think about is you'll want to double the enclosures volume since you're going to add a second woofer which would mean making a new cab. So if you wanted to build it as an MTM you could build it as a floor standing speaker.
      Thanks, Jay -- If I understand you correctly, the TMM alignment is typically associated with a 2.5-way xover? I hadn't previously made that connection.

      And, yes, I forgot to mention that I've modeled a new vented 44L enclosure for two woofers :D

      Comment


      • #4
        Re: TMM or MTM?

        Originally posted by 50 watt head View Post
        Thanks, Jay -- If I understand you correctly, the TMM alignment is typically associated with a 2.5-way xover? I hadn't previously made that connection.

        And, yes, I forgot to mention that I've modeled a new vented 44L enclosure for two woofers :D
        I think 2.5 way is a better option but I've read that there are designs in the TMM alignment that are 2 way speakers. I tried it with the first rev of the ruinations with a crossover made by Madisound and felt like after I converted them to 2.5 way it was an improvement. If you're going with a new cab you could go with the MTM alignment and get the tweeter to still be at ear level.

        Take it easy
        Jay
        "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

        Breakfast Stout - HiVi RT2 II/Aurasound NS6
        Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
        Ruination 2.5 way - Vifa DX25/Fountek FW168
        Levitation TM
        - Vifa BC25SG15/Fountek FW168

        Comment


        • #5
          Re: TMM or MTM?

          I had the pleasure of listening to Phil's Gila Monsters this past week -- we compared them to Lou Corragio's PeeDeis and we both agree that the comparison validated the quality of the GMs. They are different, but very close in many ways.

          Both speakers are capable of 100 db, so that led me to wonder what advantages an MTM configuration would offer over the TM's, and what advantages/disadvantages there might be to a 2.5 configuration.
          Tritrix HT:http://techtalk.parts-express.com/sh...d.php?t=222519
          Dayton 12" Subwoofer: http://techtalk.parts-express.com/sh...d.php?t=222930
          Overnight Sensations: http://techtalk.parts-express.com/sh...d.php?t=223751
          Cerberus sub: http://techtalk.parts-express.com/sh...hlight=cerebus
          Duellatis: http://techtalk.parts-express.com/sh...d.php?t=224943
          NTN's: http://techtalk.parts-express.com/sh...d.php?t=227902

          Comment


          • #6
            Re: TMM or MTM?

            I've attached graphs of the MTM simulation that I've done, using the Peerless 831735 and Dayton RS28A.

            At this point, the only hesitation I have in upgrading to MTM (from my present MT) is a concern that an MTM would be just plain "too much speaker" for my small (14' x 14') living room. Anybody have any thoughts about that -- has anyone ever owned/built something that ended up too big for their listening room?
            Attached Files

            Comment


            • #7
              Re: TMM or MTM?

              Originally posted by Soundslike View Post
              I had the pleasure of listening to Phil's Gila Monsters this past week -- we compared them to Lou Corragio's PeeDeis and we both agree that the comparison validated the quality of the GMs. They are different, but very close in many ways.
              I owe a big thanks to Ron, because this comparison was a great learning experience for me. The room we used for this comparison was probably double the space/volume of my living room, which all by itself gave me a much better idea of what my GMs sound like. And being able to reference them alongside a design using the same woofer from LouC assured me that these GMs really are finished and I can stop tweaking the xover already :D

              Comment


              • #8
                Re: TMM or MTM?

                Here are the results of the Gila Monster MT simulation that I did using the RS28A.
                Attached Files

                Comment


                • #9
                  Re: TMM or MTM?

                  Given your room size, it seems like a 2.5 way TMM might free up one 831735 for more mid duty, presumably for even better performance. I don't think anyone has yet used this driver in a quasi-dedicated mid mode.

                  Then again, perhaps it's time to congratulate yourself and just enjoy the music.

                  One other thing. Is it possible to get a schematic of the RS28A XO? I'm not so excellent at translating from PCD screens to schematics.


                  Originally posted by 50 watt head View Post
                  I've attached graphs of the MTM simulation that I've done, using the Peerless 831735 and Dayton RS28A.

                  At this point, the only hesitation I have in upgrading to MTM (from my present MT) is a concern that an MTM would be just plain "too much speaker" for my small (14' x 14') living room. Anybody have any thoughts about that -- has anyone ever owned/built something that ended up too big for their listening room?
                  I was so much older then, I'm younger than that now.
                  OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                  Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                  Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                  Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                  LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                  Comment


                  • #10
                    Re: TMM or MTM?

                    Its all greek to me FB!
                    A good friend will come bail you out of jail. A real friend would be sitting in the cell next to you saying "Dammit man we effed up!!"

                    "Yeah you kinda walked up in here and punched the biggest, baddest speaker in the face haha." - Greywarden


                    My first Speaker Build - A 5.1 HT System:


                    http://techtalk.parts-express.com/sh...d.php?t=223774

                    Comment


                    • #11
                      Re: TMM or MTM?

                      Originally posted by fastbike1 View Post
                      Given your room size, it seems like a 2.5 way TMM might free up one 831735 for more mid duty, presumably for even better performance. I don't think anyone has yet used this driver in a quasi-dedicated mid mode.
                      I've tried to sim a 2.5-way and so far haven't had any luck making it work

                      One other thing. Is it possible to get a schematic of the RS28A XO? I'm not so excellent at translating from PCD screens to schematics.
                      I've attached the MT schem below; I'll draw up and post the MTM version later.
                      Attached Files

                      Comment


                      • #12
                        Re: TMM or MTM?

                        Here is the MTM schematic.
                        Attached Files

                        Comment


                        • #13
                          Re: TMM or MTM?

                          Thanks for the fast response.

                          I have 4 of the 831735s and was thinking of a variation of Lou's Veepers. Not so sure now since I have the BC tweet and some RS28As. May have to pull Paul's trick and try both with external crossovers in a "standard" Amiga cab. I usually make my cabs w/ removal rear panels anyway.

                          I've modeled your box w/ WT2 measurements from new 831735s and get 103dB w/35 watts. Below Xmax above 35 Hz. I think I'm with you guys and am not sure the MTM is worth the extra size.
                          I was so much older then, I'm younger than that now.
                          OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                          Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                          Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                          Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                          LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                          Comment


                          • #14
                            Re: TMM or MTM?

                            Originally posted by fastbike1 View Post
                            I've modeled your box w/ WT2 measurements from new 831735s and get 103dB w/35 watts. Below Xmax above 35 Hz. I think I'm with you guys and am not sure the MTM is worth the extra size.
                            Just so I understand you correctly, your line of thinking is: the MT will put out 103dB @35 watts down to 35Hz, and that's plenty, so there's no need to go to the trouble/expense of building the MTM just to gain a few more dB. Is that more or less what you're thinking?

                            About the tweeter upgrade: the Vifa BC25SG sounds very good, but I've come to think the 831735 really deserves a premium tweeter. Given the genres I listen to and the SPLs that I regularly use, I think it will be worth investing in the RS28a for absolute ease and clarity in the lower treble.

                            BTW, I have a stepson who lives in Brownfield, whereabouts in TX are you?

                            Comment


                            • #15
                              Re: TMM or MTM?

                              That is exactly my thinking. I'm not adverse to building a 40 liter box, but it really doesn't get anything but more dB. The 40 liter version shows 109dB because it will take 70 watts at the same excursion, but I don't listen to anything near that loud. 85dB "steady" is closer for me. 90 only for short periods. Port length is reasonable, velocity is reasonable in your 22 liter box.

                              I haven't listened to the drivers yet, but from everything I've read, the HDS drivers are pretty special so I also think the RS28A is almost a "must have".

                              I'm about 30 miles southwest of Fort Worth. Your stepson is a bit over 300 miles from me.


                              Originally posted by 50 watt head View Post
                              Just so I understand you correctly, your line of thinking is: the MT will put out 103dB @35 watts down to 35Hz, and that's plenty, so there's no need to go to the trouble/expense of building the MTM just to gain a few more dB. Is that more or less what you're thinking?

                              About the tweeter upgrade: the Vifa BC25SG sounds very good, but I've come to think the 831735 really deserves a premium tweeter. Given the genres I listen to and the SPLs that I regularly use, I think it will be worth investing in the RS28a for absolute ease and clarity in the lower treble.

                              BTW, I have a stepson who lives in Brownfield, whereabouts in TX are you?
                              I was so much older then, I'm younger than that now.
                              OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                              Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                              Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                              Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                              LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                              Comment

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