Announcement

Collapse
No announcement yet.

MTM vs TM, and Series vs Parallel and how it effects sensitivity

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

  • MTM vs TM, and Series vs Parallel and how it effects sensitivity

    This has probably been beat to death, but I'm curious about it. Let's use a single VC 8 ohm woofer, and say it's 90db sens. Can someone let me know if this is correct math?...

    2 woofers, each a single 4 ohm VC, 90db sens, wired in parallel= 2 ohms, +3db, so 93db sens.

    2 woofers, each a single 4 ohm VC, 90db sens, wired in series= 8 ohms, +0db, so it remains 90 db sens; correct?

    If that math is correct, what is the gain from using (2) 4 ohm woofers in a MTM/TMM wired in series; verses just making it a TM? I could definitely see if these were 8 ohm woofers- the gain from wiring in parallel would be +3db sens; but using 4 ohm woofers wired in series in a MTM, what's the gain in going to a MTM vs just making a TM? The sensitivity is the same for both.

    I can make some assumptions but not sure if they're true... For example, I would assume you would have better power handling and more output from the 8 ohm MTM, verses a 4 ohm TM; the MTM would play cleaner at higher volume... is this correct? Any other pros/cons to making a 8 ohm MTM, verses making a 4 ohm TM using the same woofer?
    "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
    "Audio is surely a journey full of revelations as you go" JasonP

  • #2
    Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

    I think you have it backwards. I believe in series they would be 2 ohm and parallel would remain 4 ohms. I may be wrong.

    Comment


    • #3
      Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

      Originally posted by richard t View Post
      I think you have it backwards. I believe in series they would be 2 ohm and parallel would remain 4 ohms. I may be wrong.
      You are
      It is estimated that one percent of the general population are psychopaths - New Criminologist: Understanding Psychopaths

      Comment


      • #4
        Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

        Originally posted by mattsk8 View Post
        This has probably been beat to death, but I'm curious about it. Let's use a single VC 8 ohm woofer, and say it's 90db sens. Can someone let me know if this is correct math?...

        2 woofers, each a single 4 ohm VC, 90db sens, wired in parallel= 2 ohms, +3db, so 93db sens.

        2 woofers, each a single 4 ohm VC, 90db sens, wired in series= 8 ohms, +0db, so it remains 90 db sens; correct?

        If that math is correct, what is the gain from using (2) 4 ohm woofers in a MTM/TMM wired in series; verses just making it a TM? I could definitely see if these were 8 ohm woofers- the gain from wiring in parallel would be +3db sens; but using 4 ohm woofers wired in series in a MTM, what's the gain in going to a MTM vs just making a TM? The sensitivity is the same for both.

        I can make some assumptions but not sure if they're true... For example, I would assume you would have better power handling and more output from the 8 ohm MTM, verses a 4 ohm TM; the MTM would play cleaner at higher volume... is this correct? Any other pros/cons to making a 8 ohm MTM, verses making a 4 ohm TM using the same woofer?
        No. Your two 4 ohm drivers in parallel will see a +6 dB increase in sensitivity to 96 dB. The series connected drivers would remain the same sensitivity as the single driver at 90 dB, but impedance would increase to 8 ohms.

        Now if you are comparing this to an 8 ohm woofer that is 90 dB, then a 4 ohm version of that driver, all other things being equal, would have a sensitivity of 93 dB rather than 90. And if you paralleled two of them to 2 ohms the sensitivity would now be 99 dB/ 2.83V.

        The advantage of two 4 ohms drivers in series is that you end up with nice 8 ohm load and twice the surface area and displacement as a single driver. Power handling is doubled, required excursions are cut in half, and distortion is lower.
        Click here for Jeff Bagby's Loudspeaker Design Software

        Comment


        • #5
          Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

          I prefer MTM because it offers better vertical directivity than TM, which helps tame floor and ceiling bounce. That assumes an in-phase crossover.
          Francis

          Comment


          • #6
            Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

            My bad. :(

            Comment


            • #7
              Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

              Originally posted by mattsk8 View Post
              This has probably been beat to death, but I'm curious about it. Let's use a single VC 8 ohm woofer, and say it's 90db sens. Can someone let me know if this is correct math?...

              2 woofers, each a single 4 ohm VC, 90db sens, wired in parallel= 2 ohms, +3db, so 93db sens.

              * * * yes, but you gain +3dB MORE sensitivity due to doubling the cone area, so . . . 96dB.

              2 woofers, each a single 4 ohm VC, 90db sens, wired in series= 8 ohms, +0db, so it remains 90 db sens; correct?

              * * * NO, @ 8 ohms you LOSE -3dB, but . . . gain +3dB back, again due to doubling the cone area, so 90dB IS correct!

              If that math is correct, what is the gain from using (2) 4 ohm woofers in a MTM/TMM wired in series; verses just making it a TM? I could definitely see if these were 8 ohm woofers- the gain from wiring in parallel would be +3db sens; but using 4 ohm woofers wired in series in a MTM, what's the gain in going to a MTM vs just making a TM? The sensitivity is the same for both.

              * * * this is no different than what you already stated above. The TM is 90dB. The series'd MTM is also 90dB, but they can take twice the total power.

              I can make some assumptions but not sure if they're true... For example, I would assume you would have better power handling and more output from the 8 ohm MTM, verses a 4 ohm TM; the MTM would play cleaner at higher volume... is this correct? Any other pros/cons to making a 8 ohm MTM, verses making a 4 ohm TM using the same woofer?
              covered (I don't really think I type that much slower than you other guys - it just seems like i do)

              Comment


              • #8
                Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                I have a spreadsheet that I use to calculate Impedance and Sensitivity of drivers for line arrays, but it illustrates what Jeff stated above. Free download here if you have MS Excel:

                http://soundhobby.com/download.htm
                Some people are addicted to Vicodin. I'm addicted to speaker building.

                The Chorales - Usher 8945A/Vifa XT25TG Build
                ESP Project 101 Lateral MOSFET Amplifier
                LM4780 Parallel Chipamp
                Sonata Soundbar Project
                The Renditions - Active/Passive Towers

                Comment


                • #9
                  Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                  The math question has been answered.

                  Originally posted by fpitas View Post
                  I prefer MTM because it offers better vertical directivity than TM, which helps tame floor and ceiling bounce. That assumes an in-phase crossover.
                  But there remain large differences in the sound field produced by TMs and MTMs, with no clear advantage one way or the other. It all depends on your application which would be better suited in my experience, and this is just a starting point; lot of other stuff matters, too.

                  Have fun,
                  Frank

                  Comment


                  • #10
                    Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                    Thanks a lot guys. So (generically) I was close in my understanding, but I forgot to add 3db for doubling the cone as well. And the gain in going from a TM to a MTM is basically the output is a lot better... Right?
                    "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                    "Audio is surely a journey full of revelations as you go" JasonP

                    Comment


                    • #11
                      Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                      As Jeff said about the MTM: "The advantage of two 4 ohms drivers in series is that you end up with nice 8 ohm load and twice the surface area and displacement as a single driver. Power handling is doubled, required excursions are cut in half, and distortion is lower."
                      Paul

                      Originally posted by mattsk8 View Post
                      Thanks a lot guys. So (generically) I was close in my understanding, but I forgot to add 3db for doubling the cone as well. And the gain in going from a TM to a MTM is basically the output is a lot better... Right?

                      Comment


                      • #12
                        Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                        Originally posted by fpitas View Post
                        I prefer MTM because it offers better vertical directivity than TM, which helps tame floor and ceiling bounce. That assumes an in-phase crossover.
                        Originally posted by fbov View Post
                        But there remain large differences in the sound field produced by TMs and MTMs, with no clear advantage one way or the other. It all depends on your application which would be better suited in my experience, and this is just a starting point; lot of other stuff matters, too.

                        Have fun,
                        Frank
                        Bingo Frank!! This was really the premise of my post, I just wanted to learn a little along the way . In addition to learning about the sensitivity changes, I was trying to figure out the pros and cons of MTM vs TM, and if there were any clear answers as to what changes in directivity and soundstage when you compare a MTM to a TM. I totally understand what fpitas is saying, but aren't there some downsides to a MTM over a TM... Or no??
                        "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                        "Audio is surely a journey full of revelations as you go" JasonP

                        Comment


                        • #13
                          Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                          Originally posted by Paul K. View Post
                          As Jeff said about the MTM: "The advantage of two 4 ohms drivers in series is that you end up with nice 8 ohm load and twice the surface area and displacement as a single driver. Power handling is doubled, required excursions are cut in half, and distortion is lower."
                          Paul
                          Basically what I meant when I said "the output is a lot better".
                          "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                          "Audio is surely a journey full of revelations as you go" JasonP

                          Comment


                          • #14
                            Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                            Originally posted by fbov View Post
                            The math question has been answered.



                            But there remain large differences in the sound field produced by TMs and MTMs, with no clear advantage one way or the other. It all depends on your application which would be better suited in my experience, and this is just a starting point; lot of other stuff matters, too.

                            Have fun,
                            Frank
                            No argument here.
                            Francis

                            Comment


                            • #15
                              Re: MTM vs TM, and Series vs Parallel and how it effects sensitivity

                              But you ended with, "Right?" as if asking for confirmation about your conclusion, thus the reason for my post. FWIW, I often don't like MTMs because they sound a bit too forward, which I'm assuming is the negative aspect of their better vertical directivity.
                              Paul

                              Originally posted by mattsk8 View Post
                              Basically what I meant when I said "the output is a lot better".

                              Comment

                              Working...
                              X