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  • Morel MD55

    Hi all. I'm looking for a good dome mid for a project and had a couple questions on the MD55. I had planned using the RS52, but some comments I read here made me wonder if the Morel wouldn't be a better choice. Besides it's mounting method makes it easier to align the AC's, which is important in this design since I'd like to try a Duelund filter with it.

    The subjective impression of the Morel seems to be very good, but does it have any undesirable traits?

    Can it be crossed 700-4000hz @ LR2ish (at least for the first octave)?

    Is it still being made? Sounds kind of like Morel has replaced it with much more expensive model.

    Thanks,
    Brandon
    ~Brandon 8O
    Please donate to my Waveguides for CNC and 3D Printing Project!!
    Please donate to my Monster Box Construction Methods Project!!
    DriverVault
    Soma Sonus

  • #2
    Re: Morel MD55

    Originally posted by augerpro View Post
    The subjective impression of the Morel seems to be very good, but does it have any undesirable traits?
    I've never come across a Morel product that I've really liked, but I've only had 4 or 5 of them in my house, hardly enough to be representative of the entire line.

    All I've seen about the Morel MDM55 are subjective opinions, which generally shouldn't be trusted. I think we need a shootout with real measurements to finally know for sure.

    I've never even seen a MDM55 impedance curve. The one with more inductive rise and/or a narrower bandwidth flat section is likely (but not surely) to have higher distortion.

    Comment


    • #3
      Re: Morel MD55

      I agree John about seeing some measurements. I've only had one Morel product, the MDT22 and it sucked. I cut the cup off and removed the rolled up ring of felt that wasn't doing anything and packed it with wool. I was going to remeasure it and see if that helped the impedance and response but then I thought what's the point? I'll never use it anyway.

      My main concern is that this mid is being replaced by the EM1308, so I won't have replacements available should something happen. And what's with the price increase for the new model? It seems Morel is doing this with a lot of teh tweeters too. Change the faceplate, give it a new model number and raise the price 50%...
      ~Brandon 8O
      Please donate to my Waveguides for CNC and 3D Printing Project!!
      Please donate to my Monster Box Construction Methods Project!!
      DriverVault
      Soma Sonus

      Comment


      • #4
        Re: Morel MD55

        Hi Brandon,

        Mark K. tested the MDM-55 some time ago along with the RS52 and other small drivers.

        http://www.audioheuristics.org/measu..._test_data.htm

        Just a side note, Paul K's winning entry at Dayton and last fall's Iowa DIY event had a MDM-55 mid and a ribbon tweeter. It's a superb sounding speaker. I prefer the sound quality of the MDM-55 to the RS52 on a totally subjective basis. I'm also a ribbon lover so what do I know? :D

        Jim

        Comment


        • #5
          Re: Morel MD55

          BTW John, in your rear mount idea for the RS52, I assume you removed the faceplate becasue of the screw heads that stick out, how did you propose to attach the mid to the baffle? I don't see any way to use screws from the back side. I guess you could use the same method as using the MCM waveguide and clamp it with some mdf pieces.

          If use the RS52 I'm not sure what kind of roundover/chamfer I'll use though. I have 1/2" roundover and chamfer bit, and just bought a really big and shallow chamfer type bit that might work better. Looks like maybe 22.5 degree and 1" or so long blade.
          ~Brandon 8O
          Please donate to my Waveguides for CNC and 3D Printing Project!!
          Please donate to my Monster Box Construction Methods Project!!
          DriverVault
          Soma Sonus

          Comment


          • #6
            Re: Morel MD55

            Jim thanks for the tip-forgot about Mark's test. I actually plan on using this with a ribbon- the Fountek NeoCD3, dome mid, and RS225 woofer in 3 way Duelund crossover. Preliminary modeling with the RS52 looks good, but the RS225 might cause some difficulty in sticking with acoustic slopes for very far. We'll see.
            ~Brandon 8O
            Please donate to my Waveguides for CNC and 3D Printing Project!!
            Please donate to my Monster Box Construction Methods Project!!
            DriverVault
            Soma Sonus

            Comment


            • #7
              Re: Morel MD55

              Originally posted by augerpro View Post
              BTW John, in your rear mount idea for the RS52, I assume you removed the faceplate becasue of the screw heads that stick out, how did you propose to attach the mid to the baffle? I don't see any way to use screws from the back side. I guess you could use the same method as using the MCM waveguide and clamp it with some mdf pieces.
              Yeah, the faceplate would be removed. Basically, I stole the mounting idea from the way I mounted the Vifa D26NC55, (I have a PDF on my tidbits page) and it would just have a MDF bar across the back with 2 screws pulling it to the baffle. Pretty simple.

              Originally posted by Jim Holtz
              Mark K. tested the MDM-55 some time ago along with the RS52 and other small drivers.
              Oh, I forgot to see if Mark tested those. Hmmm, I just get "There is no website configured at this address." Might just be an issue getting to the web site from work, I'll check it out when I get home.

              Comment


              • #8
                Re: Morel MD55

                I'm not qualified to comment, but here's one guys take on soft-dome mids...

                excerpt from here: http://www.nutshellhifi.com/library/...r-design2.html
                None are more hopelessly enslaved than those who falsely believe they are free

                Comment


                • #9
                  Re: Morel MD55

                  Originally posted by jkrutke View Post
                  I've never come across a Morel product that I've really liked, but I've only had 4 or 5 of them in my house, hardly enough to be representative of the entire line.
                  I've got a pair of MDT-37 tweets that you're welcome to test next time you're taking measurements. I work in the valley and could drop them off with you where ever / when ever would be convenient. I honestly don't know what I'll use them for at this point, so if they sat on your shelf for a month, I'd lose no sleep. :D
                  nothing can stop me now

                  Comment


                  • #10
                    Re: Morel MD55

                    If folks are really interested, I can sweep the RS52 and the 55 and post them. My take is that the drivers are very close. The RS52 is technically better in regards to nonlinear distortion but the 55 is physically smaller and doesn't have the metal peak.

                    Asking an acoustic LR2 at 700 from the morel-prob the RS52 is too much. Consider 3rd or 4rth order acoustic under these conditions

                    PS domes in this range are a bit tricky. Baffle width is very important.
                    audioheuristics isn't around right now...

                    Comment


                    • #11
                      Re: Morel MD55

                      Originally posted by markk View Post
                      Asking an acoustic LR2 at 700 from the morel-prob the RS52 is too much. Consider 3rd or 4rth order acoustic under these conditions.
                      If I go with a Duelund style filter it ties my hands quite a bit. I can only change aleph (dampening coefficient) and center frequency. Lower aleph puts more demands on the woofer and tweeter, and I'm already at the limits of what I'm comfortable with with these drivers. I don't want to use the mid any higher than 4khz-and can't with the MDM55-so I can't raise the cener frequency any higher. So I dunno...Now I would most likely only stick to the 2nd order slopes for the first octave and then transition to a something steeper.

                      Originally posted by markk View Post
                      PS domes in this range are a bit tricky. Baffle width is very important.
                      What specifically are you referring too?
                      ~Brandon 8O
                      Please donate to my Waveguides for CNC and 3D Printing Project!!
                      Please donate to my Monster Box Construction Methods Project!!
                      DriverVault
                      Soma Sonus

                      Comment


                      • #12
                        Re: Really old news

                        Sounds like Lynn Olson speaking. He does have valid points and one trying to use most dome midranges below 500 Hz sure is asking for disappointment. But, if you cross them higher, say 700 Hz or up, then cross to a small-dome or ribbon tweeter at 4-5 kHz, you can end up with exquisite sound, especially if the mating woofer works well crossing at 700 Hz or higher. I've used the MDM55 twice, once with an RS225 and XT19 and again with the SS22W/8857T00 and NeoCD1.0 and both combinations sound(ed) extremely good. There's no honking or fatigue or distortion that Lynn talks about. I've also used the RS52 twice and crossed at similar frequencies to woofer and tweeter; it sounded good, too, but not quite as good as the MDM55 (but that may be crossover integration deficiencies and not driver deficiences). I cannot take any credit for these crossover design, however, as others did them for me.

                        Still, maybe some well-designed and executed measurements as John proposes would be informative.

                        And, to Jim Holtz, thanks for your nice comments.
                        Paul

                        Originally posted by wingnut View Post
                        I'm not qualified to comment, but here's one guys take on soft-dome mids...

                        excerpt from here: http://www.nutshellhifi.com/library/...r-design2.html

                        Comment


                        • #13
                          Re: Really old news

                          Originally posted by Paul K. View Post
                          And, to Jim Holtz, thanks for your nice comments.
                          Paul
                          Hi Paul,

                          No thanks necessary. You have a superb sounding speaker that I really enjoyed listening to at last fall's Iowa DIY event. I've also worked with the MDM-55 in the JH3 Reference design Rick and I developed several years ago. It tied for 1st place with Salk Sound Veracity speakers in the unlimited category at the 2003 Iowa DIY event. The Veracity uses a Seas W18 Excel woofer with a Dennis Murphy crossover so you know it was good.

                          I think the MDM-55 is a fine driver when used appropriately as you pointed out and is my top choice in a mid dome. I just wish the prices weren't so high. I bought my last pair at the Dayton event in 2003 and took advantage of the discount they offered. I paid $96 for the pair. Now, that was cool! :D

                          Jim

                          Comment


                          • #14
                            Re: Morel MD55

                            Originally posted by wingnut View Post
                            Both factors combine to make the midrange driver a device that must handle much more power than a tweeter. This imposes harsh demands on the rigidity of the diaphragm, and it exposes the simple suspension to rocking modes.
                            I have the ATC dome you mentioned on my testing wishlist. It does look nice. That article is interesting but it contains broad generalizations that are not always right. There's more to solving rocking modes than just having two suspension planes to keep movement linear. I know of two things that keep the rocking modes to a minimum. One is having the combined center of gravity (all moving parts) as close as possible to the suspension plane. The other is having the voice coil leads on opposing sides on the coil.

                            I recall the first time I tried to create a spiderless passive radiator with a foam surround and a MDF disc. I just made a hole in the enclosure and glued the surround to the disc. I could tell bass was sloppy and distorted... not to mention in 3 days it had a angled sag problem. I tried it again with a rabbet offsetting the surround connection to the center of the MDF disc and it was much better, also solving the sag problem. (note that there was more to getting that style of passive radiator to work well but that's a different topic) The same mechanical principal applies to a midrange dome.

                            Seas dome tweeters have both voice coil leads connecting on one side of the dome. Some of them have a woven tinsel lead, which is meant to allow more excursion. These tweeters have a W in the model designation, or at least the prestige line models. I've tested a lot of Seas tweeters and the W models always had higher harmonic distortion. Then it dawned on me: the woven tinsel leads have a lot more weight than the models that just the have the light weight voice coil wire running to the terminals. Since both of the heavy tinsel leads are on one side, they induce rocking motion. This pretty much sums up why the 27TDFC outperforms the Millenium, or why the 27TBFC outperforms the 27TTFNCGW. Once again, the same mechanical principal applies to a midrange dome. (obviously, there's some speculation here) I think both the RS52 and the MDM55 have opposing voice coil leads, so in this comparison differences that induce rocking modes lie elsewhere.

                            Comment


                            • #15
                              Re: Really old news

                              Originally posted by Paul K. View Post
                              I've used the MDM55 twice, once with an RS225 and XT19 and again with the SS22W/8857T00 and NeoCD1.0 and both combinations sound(ed) extremely good. There's no honking or fatigue or distortion that Lynn talks about. I've also used the RS52 twice and crossed at similar frequencies to woofer and tweeter; it sounded good, too, but not quite as good as the MDM55 (but that may be crossover integration deficiencies and not driver deficiences)
                              I think it might be good to point out that the Dynaudio D76 domes I used to use in the old "Xenon" design (built roughly 15 years ago) had the honking and fatigue mentioned. After a while, I hated it. Unfortunately, I had no measurement experience back then and I have no hard evidence if it was the dome or if it was poor crossover design. If I still had those speakers today I could get some real measurements. I dismantled them and they laid around in my stock until I discovered ebay. :D

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