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In Praise of Aethers, Baffle Studies and LEDE

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  • In Praise of Aethers, Baffle Studies and LEDE

    Paul C's Aethers gave me the incentive to simulate something similar with drivers/crossovers on hand. This is a temporary strategy as I have a complete Aethers parts kit coming soon so I can build the real thing. So bear with me as I describe what, as an amateur, I have done so far.

    I took my 4 Audax HM130ZO midrange drivers and a pair of Morel MDT-33 tweeters and built an open baffle as shown in the pictures below. These are drivers used in the Dick Olsher designed PolyNatalia speaker system which I have enjoyed for years (see my Avatar) and an extra pair of mid drivers garnered over the years enabled this MTM open baffle design. I put the two HM130ZO drivers per channel in series to keep sensitivity in line with other drivers and (now it gets dangerous) I scaled some crossover values to match the now 16 ohm midrange configuration. I can describe this process if anyone is interested but, simply stated, I changed the highpass for the mid drivers to a first order (electrical) instead of the 2nd order in the Olsher crossover. I reasoned that the dipole baffle creates a 6 db rolloff beginning at somewhere around 300 Hz so a first order should combine with the 2nd order low pass for the woofers. To improve the bass/mid combo I also put a 4 ohm resistor in series with the woofer low pass shunt capacitor to relax its transfer function. This helped the overall sound to "gel" in the lower mid range and be more smooth. Then, I scaled or doubled the values of the inductors and halved the values of the capacitors in the midrange bandpass filter to help it change from an 8 ohm to a 16 ohm version. Then, came a 2 month time in which voicing changes were made to the values of various components to improve and change the sound at various frequencies.

    All in all I can only state that the result so far has provided me with the very best speaker system I have ever enjoyed ! I am somewhat a trained musician, having played in dance bands, college marching bands and concert bands, sung in a quintet that toured several high schools in the Los Angeles and Utah areas, sung in church choirs, and had an older sister who played the piano in our home where I grew up. I have strong memories of what real music is supposed to sound like. This open baffle system can make Chopin played by Malcom Frager on his big Bosendorfer piano a spine chilling experience! And, these speakers really bring the room alive. Memories of the LEDE (live end dead end) article in Audio many years ago came to mind. I moved sound absorbers and diffusing objects around to help the room better cooperate with this new type of sound system. I am anxiously awaiting the chance to build the real Aethers with a crossover more professionally designed than my modifications to the Olsher Poly Natalia crossover (see xover attached).

    My baffle shape/size is the result of a Troelsgravesen (dk) study (http://www.troelsgravesen.dk/OBS.htm). I first compared the sound of the baffle shaped per Paul C's design then listened to the baffle built according the the Troelsgravesen study. The one shown creates a more open and smooth sound, to my ears, but the study shows the design like Paul's to be a very close 2nd choice. Because the lack of box coloration makes for sound with less distortion I find I am playing things louder. The baffle was vibrating considerably so I built a new baffle of two pieces sandwiched around a 1/4" foam board. Most of the vibration has now gone because of this constrained layer construction.

    Well, whatta' hobby.

    Dick
    Attached Files
    Last edited by dickwest; 07-17-2009, 12:43 AM. Reason: mispelling

  • #2
    Re: In Praise of Aethers, Baffle Studies and LEDE

    Here are other pertinent images not loaded with first message. I went too fast and didn't wait for a couple to upload.
    Attached Files

    Comment


    • #3
      Re: In Praise of Aethers, Baffle Studies and LEDE

      Well, I'll get this right soon. Here is the crossover used as a starting point.
      Attached Files

      Comment


      • #4
        Re: In Praise of Aethers, Baffle Studies and LEDE

        Well done on using a first order on the low end of the mids .

        The basic design does seem to do music quite nicely, doesn't it. :D

        Dick, can you put a piece of timber across the top of the OB mids, to close off the top of the u-frame, and see if you get any changes. Paul and I often argued about this (well, not really)
        If people want to listen to wiggles, that up to them....

        I prefer music.

        Comment


        • #5
          Re: In Praise of Aethers, Baffle Studies and LEDE

          Originally posted by Andy_G View Post

          Dick, can you put a piece of timber across the top of the OB mids, to close off the top of the u-frame, and see if you get any changes. Paul and I often argued about this (well, not really)
          Without a top:
          This should change the lobing pattern and reduce the amount of midrange firing at the ceiling below the baffle's dipole cancellation frequency.

          Comment


          • #6
            Re: In Praise of Aethers, Baffle Studies and LEDE

            yeah, Blackwood had top of the U-frame closed off, but Paul didn't do it on the Aethers. You can clearly see it is missing in the second pic of Dick's second post. I think it should be there, and was wondering if it would make any audible or measurable difference. Dick can find out just by cutting a tight fit piece of timber and jamming it in place.
            If people want to listen to wiggles, that up to them....

            I prefer music.

            Comment


            • #7
              Re: In Praise of Aethers, Baffle Studies and LEDE

              Andy,

              The 2nd picture in the 2nd post is the 2nd version of OB speakers I tried. This 2nd version uses the Audax HP130Z2 drivers. Here you can see my comments about this driver plus comments from John Krutke about them as well (http://www.diyaudio.com/forums/showt...threadid=55456). The HP130Z2 was never available retail as far as I know. They showed up in eBay auctions after, I believe, a certain large speaker manufacturer in the Los Angeles area went bankrupt and I snagged a few pairs of them. These are really great mid drivers but their Fs is a little higher than that of the HM130ZO so they lack a little of the lower midrange in my application.

              Yes, I tried putting a "lid" on the "U" shaped baffle in the 2nd picture (2nd post) and sensed a slight reduction in the image size and concluded I did not like it.

              Note the 2 different shapes of baffles and my comments about which is preferred, at least in my application.
              Last edited by dickwest; 07-17-2009, 12:44 AM.

              Comment


              • #8
                Re: In Praise of Aethers, Baffle Studies and LEDE

                Originally posted by dickwest View Post
                Yes, I tried putting a "lid" on the "U" shaped baffle in the 2nd picture (2nd post) and sensed a slight reduction in the image size and concluded I did not like it.

                Note the 2 different shapes of baffles and my comments about which is preferred, at least in my application.
                That makes perfect sense. A lid on the top is going to create a cardoid polar pattern. This will mean less energy reflected off the backwall and more reflected at andles greater than approximately 45 degrees.(midrange only.)

                Comment


                • #9
                  Re: In Praise of Aethers, Baffle Studies and LEDE

                  cool, I can't really remove the top of my u-frame to investigate.. it sort of holds things together :D

                  a question, how far behind the back of the mid baffle is your wall ?

                  and your side walls from the edge of the speaker ?
                  If people want to listen to wiggles, that up to them....

                  I prefer music.

                  Comment


                  • #10
                    Re: In Praise of Aethers, Baffle Studies and LEDE

                    My speakers are quite far out into a 22' X 24' room. They are 4.5 feet from the front wall and 5 feet from the side walls. They are toed in with their lines of sight crossing just in front of my listening position. It is fun to play with their positioning and then experience the difference in the size of the sound stage and the relative positioning of various performers.

                    "Live in Paris" with Diana Krall has been a good test CD to get the xover voiced. Also, the Shirley Horn "Loving You" helps to get the bass/mid xover points properly defined. When done right her voice loses its chestiness and other instruments also begin to take their proper positions in the sound stage.

                    Comment


                    • #11
                      Re: In Praise of Aethers, Baffle Studies and LEDE

                      Originally posted by Andy_G View Post
                      Well done on using a first order on the low end of the mids .

                      The basic design does seem to do music quite nicely, doesn't it. :D

                      Dick, can you put a piece of timber across the top of the OB mids, to close off the top of the u-frame, and see if you get any changes. Paul and I often argued about this (well, not really)
                      On that note, I've always wondered about boring holes/slots in the sides of the U-frame to do much the same thing.

                      NK
                      I'm just that guy. www.sru.edu Rock Solid.

                      "It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion."

                      L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

                      Comment


                      • #12
                        Re: In Praise of Aethers, Baffle Studies and LEDE

                        Bravo! You're definitely getting into the spirit of it!

                        So is it a 1st order XO all around, or just used for certain filters?

                        I'm glad that, as a musician, you found the speakers to be more "lively" or "realistic" (hope I'm not putting words in your mouth). A weird thing happens to me, if I haven't listened to the Aethers or Sunflowers in a while, when I finally get back to listening to them again, I involuntarily just sort of relax because there's just something about the soundstage that is much truer to live instruments.
                        Isn't it about time we started answering rhetorical questions?

                        Paul Carmody's DIY Audio Projects
                        Twitter: @undefinition1

                        Comment


                        • #13
                          Re: In Praise of Aethers, Baffle Studies and LEDE

                          Originally posted by Paul Carmody View Post
                          "lively" or "realistic" (
                          Subjectivity! Kill him!! :p:D

                          NK
                          I'm just that guy. www.sru.edu Rock Solid.

                          "It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion."

                          L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

                          Comment


                          • #14
                            Re: In Praise of Aethers, Baffle Studies and LEDE

                            Originally posted by nick29498141 View Post
                            Subjectivity! Kill him!! :p:D

                            NK
                            I love it.. Good Boy , Paul !! :D
                            If people want to listen to wiggles, that up to them....

                            I prefer music.

                            Comment


                            • #15
                              Re: In Praise of Aethers, Baffle Studies and LEDE

                              Paul,

                              My first post in this thread was long and a little dense. The crossover was initially designed for the PolyNatalia 3-way speaker. I used the same components with the addition of another pair of HM130ZO and then I scaled mid filter values for the change from 8 to 16 ohms impedance.

                              The low pass for the bass is the same as original -- 2nd order electrical.
                              The high pass for the mid bandpass filter is 1st order which, when combined with baffle roll off beginning around 400 hz, should combine to make an acoustic 2nd order slope to match that of the bass high pass 2nd order filter.

                              The low pass for the mid is about the same as shown in the schematic -- somewhat of a 2nd order. I fudged on the values of its inductors and used those on hand, but after trying various combos of those I have I settled for .70 and .25 mH which are a little different from what scaled or doubled values would dictate.

                              The high pass for the tweeter is 2nd order electrical.

                              The HM130ZO has some significant cone break up so 1st order filters are not really prudent to try for this driver.

                              The mid and tweeter are connected out of phase with the woofer.

                              The Audax Aerogel coned drivers have an articulate slightly crisp sound and the MDT-33 is no slouch, either. So, as I finalize crossover adjustments pleasure with the system should only increase. I don't have measuring equipment/knowledge and published specs on Audax drivers have always been suspect. So, trial and error voicing is required, which I realize is almost considered anathema here where so many measuring/simulation gurus hang out ;) (please no flames).

                              I am waiting to receive an Aethers kit which will be built soon so I can compare what I have cobbled up with your "real" thing.


                              Originally posted by Paul Carmody View Post
                              Bravo! You're definitely getting into the spirit of it!

                              So is it a 1st order XO all around, or just used for certain filters?

                              I'm glad that, as a musician, you found the speakers to be more "lively" or "realistic" (hope I'm not putting words in your mouth). A weird thing happens to me, if I haven't listened to the Aethers or Sunflowers in a while, when I finally get back to listening to them again, I involuntarily just sort of relax because there's just something about the soundstage that is much truer to live instruments.

                              Comment

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