Possible surround speaker project.

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • Steve Goff
    Senior Member
    • Feb 2002
    • 186

    Possible surround speaker project.

    I like my left, right, and center speakers, the Revel M20s and C30, a lot. They use metal cones and domes, high-order crossovers, and inert boxes, and are designed using sound principles. As measured by both Revel and the NRC, their response curves on and off axis are fairly amazing, gently sloping down towards the upper frequencies. (If I were the designer I might have tried to go with a lower crossover frequency (the M20s cross over at 2.2K), and I think I would have designed in a tiny bit of a BBC saddle, for those of you who know what that means. And I'm sure I'd try Jon's steep eliptical filter to take the tweeter lower.) I prefer the M20s to the Gems, if not the Salons or the Studios or the big Avalons. The M20s go into the mid 30s, and they will play very loudly in my home theater setup when crossed over to a subwoofer.

    I think I'd like to try to build something comparable as a set of four surround sound speakers for a 7.1 configuration, using metal cone woofers and steep filters. My room is only about 14 feet wide, so the speakers would have to be close to the wall, freestanding, fairly shallow, and very tall, so the sound emerges about two feet above the head. This would put the drivers, or at least the top driver, about 60 inches above the floor. This would mean that the tweeter would have to have good dispersion, since the listener's ears would be fairly far off axis. This might leave out the Vifa ring radiator, since it may not have the best off-axis response. Alternatively, the tweeter could be angled down, much like the tweeter on Brian Cheeney's new VMPS flagship speaker. I would think that the HiV 8 inch woofer used lately by Jon and Thomas would be ideal, as might Jon's steep-slope filter.

    So far I'm just daydreaming, since I don't even have a shop to build these things. I've had experience in the distant past, though, since I designed some speakers about 25 years ago that were some of the first to incorporate Sigfried Linkwitz's crossover ideas, along with some design ideas of my own that later cropped up in onther speakers. They looked very musch like the later Ariel 10Ts, with a slimmer bass box underneath. My friend Mila Nestorovic supplied the woofers, using his patented circuit. A friend who manufactures high end 2-channel audio gear used these speakers for a few years to demo his gear at CES, until he began to share a room with Roger West and the wonderful SoundLab speakers. I had offers from some far east companies to buy the design, but by then I was a full-time lawyer....

    Back in the late 70s and early 80s I was designing new speakers and modifying amplifiers all of the time, but no more. So if I do come up with something I'd probably have to get someone else to make the boxes. I can still solder and test stuff, though.

    So I'd love anyone's comment on this idea. Alternatives ideas for overall concept, drivers, boxes, crossovers, or anything else are welcome.




    Steve Goff
    Steve Goff
  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10934

    #2
    The M8a MK-IV built in a small sealed cab is just the ticket. A tight but workable fit in the Woodstyle WS803 boxes. Using that box only requires a jig saw/drill/router to customize it into a high quality enclosure

    I built a pair of the MKIII design for wall mounted bedroom speakers (minimal baffle step compensation), and am thrilled with the performance.

    The ring radiator actually has slightly better off-axis performance than it does on-axis preformance




    theAudioWorx
    Klone-Audio

    IB subwoofer FAQ page


    "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

    Comment

    • Steve Goff
      Senior Member
      • Feb 2002
      • 186

      #3
      Originally posted by ThomasW
      The M8a MK-IV built in a small sealed cab is just the ticket. A tight but workable fit in the Woodstyle WS803 boxes. Using that box only requires a jig saw/drill/router to customize it into a high quality enclosure

      I built a pair of the MKIII design for wall mounted bedroom speakers (minimal baffle step compensation), and am thrilled with the performance.

      The ring radiator actually has slightly better off-axis performance than it does on-axis preformance
      Thomas,

      Thanks for your reply. Your idea sounds great to me! I hadn't actually looked at the response of the Vifa tweeter, but just thought I read somewhere that its off axis response fell faster than most. Have you guys done a version with minimal baffle step compensation and the Vifa tweeter?

      The Woodstyle enclosure looks good, and I've previously looked at your step-by-step article on it's construction. I'd like to make the speakers floorstanding if I could, since I live in a 110-year-old historic house and I'm hesitant to put any more holes in my wonderful old plaster walls. But I guess I could make some tall stands, or put them on bookshelves. Often it makes more sense to me esthetically and structurally to make the speakers floorstanding rather than stand-mounted. I'll look at the Woodstyle catalog and other ready-made enclosures to see if I can find anything suitable. I suspect I'll end up with the WS803s, though.

      I noticed that the crossovers and zobel networks are quite bulky using the multiple film caps you use. Would it make sense to go with a slightly larger cabinet, or does the WS803 give you a nice, well-damped bass response?




      Steve Goff
      Steve Goff

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15272

        #4
        Thomas's suggestion would be my first response, also. The crossover is somewhat bulky, but as designed for him, the baffle step was eliminated for wall placmement.

        In this size box sealed, the alignment is about a Q of 0.577, which is much more damped than the typical home speaker, which are often designed for a sealed box Q of 0.707 for a Butterworth alignment. When placing an enclosure away from a wall, it's feasible to go with a critically damped alignment sealed (Q of 0.5), as the room boundary lift change from 4pi to 2pi space gives you up to 6 dB more LF output as long as you do the spacing right. When mounting flush to a wall, you're in contant 2 pi mode, and no "room lift" occurs (or rather, it occurs at all frequencies, so don't do baffle step compensation).

        Understand, this sealed design is intended to work with an external sub, it's not tuned for LF extension at all, just smallest reasonable box with good damping.

        The small box volume would make a tower of the height you're proposing awkward- you could make a floor standing system that tall, just a two way, perhaps by sealing off part of the lower portion of the enclosure.

        If you went with this design at that listener height, you should invert the vertical placment of the woofer/tweeter, as the MkIV M8 is designed for both seating and standing use (that's how I use them), and the vertical window is optimized in that way, on and above the woofer axis. Below the woofer axis, you get a dip in the crossover region. So, if one were to place these high, you'd want to invert the configuration.

        This business of surround speakers and center channel speakers is a "pesky" matter- I've been getting some various requests for a small surround system that isn't too expensive to build and has clean off axis response. One close friend locally needs a couple of sets of these, or something similar. Something less expensive and smaller than the M8. There's an AudioWorx "Black Ops" project which so far is only me modeling it in LSPCAD while riding the train to and from work the last two weeks (on the couple of days I've gone in); main driver candidate is a carbon fiber Audax 6-1/2 midwoofer, and the Vifa XT25 tweeter on the top. Due to the range of the Audax, the crossover I'm experimenting with now is a quasi third order series crossover (cuts component count) at about 2 kHz; still with full impedance comp on the tweeter- it looks pretty promising, a lot fewer crossover parts than an M8. One might be able to build it into the WS802 enclsoure, though with the 803 it coudl be tuned to have some real LF output, also. But the 802 could fit on some real lightweight stands, so who knows?

        This came about because I kept trying to think of a way to use the MCM 6-1/2" woofer in a two way, which is an imperfect klone of the Audax. Finally, being the dufus that I am, it occured to me, why not use the Audax? :roll: Other than the cost difference- 3:1! :LOL:

        The Audax carbon fiber drivers are very close to pistonic behavior fairly high up. The HM170C0 doesn't start to lose it until 4 - 5 kHz, and even then it's well damped. There are reasons Pipe Dreams uses the Audax CF drivers in their systems.

        Here's the MCM Klone, which is startlingly similar in appearance and construction:



        I'm using these in a line array project. Got all the parts, but need some time for my back to heal.



        Regarding off axis response, above 12 kHz, the Vifa XT goes soft beyond 30 degrees; everything that doesn't have a difussor lens/resonator seems to do that, and since I don't like the sound of tweeters on axis WITH diffusor/lens assemblies (and remove them in the case where I have used them, like the MB Quart), it's something of a moot point for me. I'd suggest listening to a commerical speaker like the Krells or Polks which use the Vifa ring tweeter and see how you like the response. Stereophile has pretty uniformly been happy with the top end of any speaker using this driver family, including their recent reveiw of the Polk 7's. Which, realistically, though only with a five inch driver, would be a lot less trouble to buy than building your own. But, if you're inclined to build, then nothing less will do!

        In my own experience, the general response of surround speakers above 12 to 15 kHz has not been very important, given what's usually mixed into the surrounds, and the quality of the audio sources in Cinema. A really flat midrange through presense region, up to 60 degrees off axis, seems a lot more important. YMMV.

        Best regards,

        Jon




        Earth First!
        _______________________________
        We'll screw up the other planets later....
        the AudioWorx
        Natalie P
        M8ta
        Modula Neo DCC
        Modula MT XE
        Modula Xtreme
        Isiris
        Wavecor Ardent

        SMJ
        Minerva Monitor
        Calliope
        Ardent D

        In Development...
        Isiris Mk II updates- in final test stage!
        Obi-Wan
        Saint-Saëns Symphonique/AKA SMJ-40
        Modula PWB
        Calliope CC Supreme
        Natalie P Ultra
        Natalie P Supreme
        Janus BP1 Sub


        Resistance is not futile, it is Volts divided by Amperes...
        Just ask Mr. Ohm....

        Comment

        • ThomasW
          Moderator Emeritus
          • Aug 2000
          • 10934

          #5
          Steve

          As Jon indicated the WS803 cab is too small for any significant LFE. I use them with a sub. This was a given as we developed the design.

          BTW the speaker is heavy 50+lbs. I bolted them to a wall stud.

          To make the large value caps, I use clusters of the 5mfd GE film caps from Madisound ($.50ea in quantity). This is labor intensive and takes up space, but large value caps end up being very reasonable. Obviously large value single caps can be used with the associated costs being doubled.

          I made my wall mounted speakers before the Vifa design (M8a-MKIV) was completed. Personally I prefer the sound of the Focal TC120 to the Vifa XT25. The benefit with the Vifa is a lower XO point and better off axis performance.

          A minitower version of the design (like Andrew P made) will have nice bottom end if a 32Hz port tuning is used.




          theAudioWorx
          Klone-Audio

          IB subwoofer FAQ page


          "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

          Comment

          • Steve Goff
            Senior Member
            • Feb 2002
            • 186

            #6
            Thanks, guys, your information is invaluable. I was wondering whether it would make sense to invert the drivers. And I had two other questions. First, how shallow back to front do you think I could make the cabinets without compromising performance? And second, how far away do you have to sit for the drivers to integrate? On the latter question, I assume they integrate closer than many designs, because of the high-order crossover.

            Both of these questions are related to making surround speakers work in my room. A listener seated in the center of our listening area would have his head about 6 feet from the side speakers and about 4 feet from the rear speakers. I had to move the couch back when I built a freestanding frame for my acoustically transparent screen, so I could put the center speaker behind it. And my latest projector, an NEC XG85, has longer focusing lenses than my previous one. By the way, I tested varois acoustically transparent screens, and I prefer Draper's woven fabric (the AT1200) over the perferated offerings of Stewart and others. It has some gradual roll off above about 14-15kHz, but is otherwise easier to work with, in part because it has minimal bounce back.




            Steve Goff
            Steve Goff

            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15272

              #7
              One of the things which is uncanny about the M8 design is the behavior due to the narrow overlap of the drivers. At the moment, I have a folded towel on the top of my left one, (which is on a 24" stand) and on that is my Stinkpad IBM laptop from work; I use it for email at home. It's been convenient because of my back operation; I can work at it standing up- though that's not an issue now, before and just after my surgery it was. Because of the vertical window these speaker have, and the very small range over overlap (hence, the small width of the null if you're seriously off the vertical "listening axis", they still sound pretty dang good standing right on top of them. The horizontal dispersion axis can be meaured at 1 meter out and it quite smooth in the 200 Hz to 10 kHz region up to 60 degrees off axis.



              The driver spacing was designed with panel diffraction "spread spectrum" control (dispersing the frequency effects) but also with regards to wavelength criteria for driver integratio in the crossover region; but having a crossover of 1.25 kHz gives a lot more latitude in positioning than, for example, the typical 6.5" two way with a crossover at 3 kHz. For the former, the ideal center to center diameter should be 10.8" or less; for the latter, it should be 4.25". With most 6-1/2" drivers and tweeters I'm aware of, the latter simply isn't possible.

              Now, one other thought- if I were in your shoes, with an all Revel system at this point, I'd give a moderate amount of thought to expanding my system into surround using these.... :W




              Revel S30 Dipole/Bipole Surround speaker

              Since I'm not selling anything, it doesn't hurt to recommend the competition! :LOL:


              Best regards,

              Jon




              Earth First!
              _______________________________
              We'll screw up the other planets later....
              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
              Minerva Monitor
              Calliope
              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saëns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
              Natalie P Ultra
              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment

              • Steve Goff
                Senior Member
                • Feb 2002
                • 186

                #8
                Thanks, Jon. I've looked at and listened to the S30s. They are quite wonderful as movie speakers, but not as wonderful for high definition surround sound music (DVD-A and SACD), which I am currently exploring. And the retail price is something like $1400 each, so four would be very expensive. And they require a hole in the wall for speaker wires if you want to mount them on the wall. As mentioned above, one of my reaons for building my own would be to avoid putting more holes in my old plaster walls.

                My current surround speakers are dual drive dipoles designed by John Dunlavey for Fosgate/Audionics, and they are actually pretty good. I'm just looking for something better for music without spending a fortune.

                By the way, I did listen to the Polks with the ring radiator tweeter. The highs sounded good, but there is something exaggerated, even harsh, about their midrange. All the measurements I've seen for them show a spike in the response, apparently caused by the small port on the front. I don't know whether that is what caused what I heard, but....

                I've also listened to the Krells briefly and the Cremoras, and liked the highs on both. But they are completely different sounding, even though they share basically the same Revelator drivers (perhaps with some modifications).

                Man the response of your speaker looks great! That kind of performance is what I'm looking for.




                Steve Goff
                Steve Goff

                Comment

                • Steve Goff
                  Senior Member
                  • Feb 2002
                  • 186

                  #9
                  I did a small, quick sketch in PhotoShop of what a floorstanding version of this speaker using the MKIV components might look like if it were made to match the Revel F30 or M20. I don't have a host for it though, and am wondering if anyone could host and post it. I'm not sure how links to pictures work on this forum.




                  Steve Goff
                  Steve Goff

                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15272

                    #10
                    Steve, if you can email it to me, I'll post it on our virtual avenue space, and mail you the URL so you can link to it.

                    Aye curumba, $1400 dollars apiece? That's a lot M8 parts! In fact, that's somewhere around the parts cost for two pairs built with the Woodstyle boxes! No wonder they don't put the prices on the web!

                    Re the Polks, believe it or not, the little port on the front is reportedly an anti-resonance device, intended to knock down some resonances (reportedly due to cabinet interior volume) without using crossover parts. MY suspicion is that any hardness in the upper mids or lower highs is cone problems from the 5" driver and their crossover design, but remember, I blame almost ALL the problems I hear in a lot of speakers in the upper midrange/lower highs at first on non-pistonic cone behavior. And that isn't always the case. But, it is so often, it's nearly like betting on a sure thing.... you can get lulled into a false sense of security...

                    Best regards,

                    Jon




                    Earth First!
                    _______________________________
                    We'll screw up the other planets later....
                    the AudioWorx
                    Natalie P
                    M8ta
                    Modula Neo DCC
                    Modula MT XE
                    Modula Xtreme
                    Isiris
                    Wavecor Ardent

                    SMJ
                    Minerva Monitor
                    Calliope
                    Ardent D

                    In Development...
                    Isiris Mk II updates- in final test stage!
                    Obi-Wan
                    Saint-Saëns Symphonique/AKA SMJ-40
                    Modula PWB
                    Calliope CC Supreme
                    Natalie P Ultra
                    Natalie P Supreme
                    Janus BP1 Sub


                    Resistance is not futile, it is Volts divided by Amperes...
                    Just ask Mr. Ohm....

                    Comment

                    • Steve Goff
                      Senior Member
                      • Feb 2002
                      • 186

                      #11
                      Thanks a lot, Jon, I've sent you an e-mail with the file.

                      Yeah, Polk says the port on the LSi7 is meant to be an anti-resonance device, but published graphs in the March Stereophile (on p. 66) show that the port has a huge spike right at the place where the frequency response has a nasty peak. The response of the woofer also has a peak. I don't know whether Atkinson was able to get a true reading of the woofer without the port, or visa versa. The text contradicts the caption for the figure in question. I'm not sure that Atkinson should be given the keys to drive his test equipment, since he seems to see cabinet resonances where he ought to be seeing cone breakup, but these graphs are pretty graphic. Another magaizine has published frequency response graphs with the same peak, just below 1kHz, though they did not show the separate response of the port. Whatever the cause, it is audible.




                      Steve Goff
                      Steve Goff

                      Comment

                      • Steve Goff
                        Senior Member
                        • Feb 2002
                        • 186

                        #12
                        Thanks to Jon, here is the image:






                        Steve Goff
                        Steve Goff

                        Comment

                        • JonMarsh
                          Mad Max Moderator
                          • Aug 2000
                          • 15272

                          #13
                          Yeah, you've got to wonder abou those folks at Polk, because they're using the 5" driver and that front panel port in a lot of their new systems.

                          I've hosted your image, and sent you the URL with some additional thoughts. For eveyone else, here's what Steve has in mind, which does look pretty interesting:




                          The really funny or amusing thing about this is that this basic design seems to be destined to be adpated to an unusually large number of personal configurations, if things go as in the recent past and current interest.

                          The current version at my home is the MkIV; plus I have a set of the MkII's (Eton and Accuton); the MkIII's are at my girlfriends, and the MkI's are at the home of my best friend in the Bay area and former boss...

                          Another Pair of MkIII's in standard configuration have been built in Denver, and a special wall mount MiniMKIII has been built by ThomasW for his bedroom.

                          A few additional pair of the MkIV has been built, and an MTM pair in sealed towers has been completed by Tibor.

                          Andrew Pratt has done a new tower version of his own, as documented in another thread in this forum section.

                          An Avalon monitor klone using the MkIV drivers and crossover is still under consideration by Trond-Eirick in Norway (he's taken on a consulting job with high stress level recently, so free time is something he only vaguely remembers :W

                          And an Avalon floor tower is in development (all CAD work completed), using what should probably be called the MkV VERY limited production configuration, as this involves modification of the MkIV design to use a Hales Transcendence tweeter (something you unfortunately can't pick up at PE or anywhere else I can think of, as what I have would be called NOS (new old stock). Happily, this tweeter is about the same impedance as the Vifa XT25, with the same Fs (makes crossover rework a lot simpler! :B It uses a low distortion underhung motor design with a double magnet pole piece and rear chamber; there's no lens or other nonsense to mess up the sound; it's just wonderfully flat from well below 1 kHz to 20 kHz.






                          Steve's concept, if built, would be another interesting variation tuned to his specific application requirements. It's also got me thinking about designing a smaller surround speaker (no attempt at bass) with the 6-1/2" HiVi. Maybe next year!

                          Best regards,

                          Jon




                          Earth First!
                          _______________________________
                          We'll screw up the other planets later....
                          the AudioWorx
                          Natalie P
                          M8ta
                          Modula Neo DCC
                          Modula MT XE
                          Modula Xtreme
                          Isiris
                          Wavecor Ardent

                          SMJ
                          Minerva Monitor
                          Calliope
                          Ardent D

                          In Development...
                          Isiris Mk II updates- in final test stage!
                          Obi-Wan
                          Saint-Saëns Symphonique/AKA SMJ-40
                          Modula PWB
                          Calliope CC Supreme
                          Natalie P Ultra
                          Natalie P Supreme
                          Janus BP1 Sub


                          Resistance is not futile, it is Volts divided by Amperes...
                          Just ask Mr. Ohm....

                          Comment

                          • Dennis H
                            Ultra Senior Member
                            • Aug 2002
                            • 3791

                            #14
                            Hey Jon,

                            A question about your quasi 8th order crossover. Traditionally people have been leery of XOs that steep, quoting group delay distortion as the reason. Do you think that's a valid concern or is it more likely they were hearing problems due to the higher parts count of traditional 8th orders. Say you were building a line array and weren't pushing the drivers near their upper and lower limits like you are with the Mk4. Would a super-steep crossover still be a good thing (Martha)? I'm thinking in particular of the digital XOs that can do an 8th order just by crunching a few extra 1's and 0's so there wouldn't be any extra sound degradation from extra parts.

                            Comment

                            • JonMarsh
                              Mad Max Moderator
                              • Aug 2000
                              • 15272

                              #15
                              These are all very valid and interesting quesitons!

                              Frankly, I'd never try to do an eigth order network with a conventional ladder configuration - the impedance control and component sensitivity issues would be frightening! Plus, I think you probably could make the case for some overall sound quality degradation due to multiple components, and especially the difficulty of getting the components of sufficient precision to make a network like this work. Since the network I use only needs one more reactive element for each section than a conventional 4th order L-R, the component and component senstivity issues are much more manageable- hardly any more difficult than for a 4th order L-R. And it get's the job done in the important area, the first 40-50 dB of attenuation.

                              The only way I think I could realistically say whether the group delay issues were significant as a problem would be to evaluate the audibility in the speaker (under anechoic conditions so that room masking isn't present) and compare to headphones or something else. Thing is, group delay for this crossover isn't much different than for a 4th order L-R, which even Linkwitz concluded after some various listening tests of his own weren't audible. That it's not so different may stem from the fact that it's 8th order just in the corner region for up to 50 dB of attentuaion, then drops back to about 4th order.

                              Last, this crossover was developed as an response to the engineering problem of doing a moderately high performance two way for a relatively small amount of money. There are so many performance aspects to balance- and it's arguably a tough call to say "A is more important than B", as to what which issues to optimize, and which to compromise.

                              So, a realistic assessment of the M8 design is that I wanted to optimize the design in the sense of having the LF extension and SPL possible with an 8" driver, yet also optimize as carefully as possible the on and off axis response, hence, the axial response and room power response as well as possible. And an absolute priority is not using the midwoofer in a freuqency range past pistonic operation, as this really (IMO) compromises midrange clarity and naturalness. This is a cornerstone of things I was learning in the 70's, and a cornerstone of the Avalon design philosphy- one which Avalon thought competitors would pick up and run with soon after the introduction of their first speakers (mid-late 80s), but yet, with very few exceptions, they haven't.

                              So, design priorities were developed around pistonic driver operation for midwoofer, a relatively stiff, strong, inexpensive and easy to build cabinet, as uniform a frequency response as possible from 100 Hz to 10 kHz up to 60 degrees off axis, and minimally expensive or difficult means for diffracation control while using conventional grille panels. Oh, did I mention moderately low cost? Everything else was on the table, and obivously group delay or transient perfect crossovers were not a consideration, as they would have totally compromised the other goals.

                              It's like the joke about designing a sub, desired attributes are small box, high sensitivity, high output level, and low cost. Pick any two...


                              Maybe doing the crossover with a DSP solution is a valid possiblity- I'm a little leary of that, but then remember, I'm the zero feedback electronics, radical DAC curmudgeon, so the idea of taking the analog signals and running them into a DSP A/D; crunching the numbers, then doing another D/A just makes me shiver... :E

                              But YMMV! So try it, and let us know what you think... but if the drivers can handle a lower order crossover with good dynamics, and everything else working out OK, I don't know that I'd bother going from 4th to 8th order.

                              For example, though I may try out the steep crossover on my line arrays (Modula MkIV), I'll probably do some tests with a straight 4th order L-R, and it wouldn't surprise me at all if that works out just fine- and allows me to reduce the crossover cost by two reactive components per side (an inductor and cap). If it does work out better with the steep network, I would expect that to be the case because steeper suppression of out of band signals results in more lower distortion in the drivers, and that might be more audible than the difference in group delay.

                              The thing is, a lot of things we do in the audio chain add "distortions" of some type or another- the question which isn't resolved, yet, IMO, is which are most detrimental to the music, and which may be justified in serving achievements which minimize other problems? There's the question....

                              Best regards,

                              Jon




                              Earth First!
                              _______________________________
                              We'll screw up the other planets later....
                              the AudioWorx
                              Natalie P
                              M8ta
                              Modula Neo DCC
                              Modula MT XE
                              Modula Xtreme
                              Isiris
                              Wavecor Ardent

                              SMJ
                              Minerva Monitor
                              Calliope
                              Ardent D

                              In Development...
                              Isiris Mk II updates- in final test stage!
                              Obi-Wan
                              Saint-Saëns Symphonique/AKA SMJ-40
                              Modula PWB
                              Calliope CC Supreme
                              Natalie P Ultra
                              Natalie P Supreme
                              Janus BP1 Sub


                              Resistance is not futile, it is Volts divided by Amperes...
                              Just ask Mr. Ohm....

                              Comment

                              • Dennis H
                                Ultra Senior Member
                                • Aug 2002
                                • 3791

                                #16
                                Thing is, group delay for this crossover isn't much different than for a 4th order L-R,
                                Ah! Very interesting! Thanks, Jon.

                                Comment

                                • Steve Goff
                                  Senior Member
                                  • Feb 2002
                                  • 186

                                  #17
                                  Thanks again to Jon, who has hosted another picture for me, I can share my second attempted PhotoShop rendering of his speaker as I might adapt it to surrond sound mode. This one is taller, narrower, ported on the bottom, and with the crossovers in the base. The thought is that I might be able to use it full range for some surround music , but cross it over to the sub for movies. So I've figured on a volume about the same as Jon is contemplating for the Avalon version of his speaker, with response to the mid 20s. One thing I don't yet know is the length of the port for this version, which would probably influence where I put it. It seems likely to be long, which may mean that it has to be on the bottom. It may be time to make some true dimension drawings:





                                  Steve Goff
                                  Steve Goff

                                  Comment

                                  • JonMarsh
                                    Mad Max Moderator
                                    • Aug 2000
                                    • 15272

                                    #18
                                    The port as designed for 64 liters is 3" diameter, with a length of 11 inches. Even at driver Xmax and maximum port output frequency, the port velocity is under 5% of the speed of sound, a conservative guideline for limiting port velocity (if it were over 5%, I'd go up to a 4" port). One could use a 4" port anyway, if you wanted to be super conservative, but this would have to be 40 cm long instead of 28 cm long.

                                    The only other thing I'm wondering about with this design, is that with the cabinet so long and small in cross section, it may almost wind up trying to act a bit like a quarter wave TL. I wouldn't be surprised if there was some kind of impact on the overall tuning and behavior, but what it might be I can't predict off hand. I'd recommend building a single prototype to evaulate LF effects and tuning first, before proceeding gung ho. (I'm a little more conservative in recommendations to other folks than I sometimes behave myself! :W

                                    -Jon




                                    Earth First!
                                    _______________________________
                                    We'll screw up the other planets later....
                                    the AudioWorx
                                    Natalie P
                                    M8ta
                                    Modula Neo DCC
                                    Modula MT XE
                                    Modula Xtreme
                                    Isiris
                                    Wavecor Ardent

                                    SMJ
                                    Minerva Monitor
                                    Calliope
                                    Ardent D

                                    In Development...
                                    Isiris Mk II updates- in final test stage!
                                    Obi-Wan
                                    Saint-Saëns Symphonique/AKA SMJ-40
                                    Modula PWB
                                    Calliope CC Supreme
                                    Natalie P Ultra
                                    Natalie P Supreme
                                    Janus BP1 Sub


                                    Resistance is not futile, it is Volts divided by Amperes...
                                    Just ask Mr. Ohm....

                                    Comment

                                    • SteveG
                                      Member
                                      • Jul 2002
                                      • 31

                                      #19
                                      I was thinking the same thing. 64 liters is about 3905.5 cubic inches. If the side to side and front to back interior dimensions are 9.5 inches and 8 inches respectively, the length would be over 51 inches, irrespective of any bracing, drivers and other stuff taking up space. The resonance frequency would be about 256Hz, which is quarter wavelength of about 63Hz. I remember next to nothing about quater wavelength transmission lines, other than that the line length should be derived by using a quarter of the driver's resonance. I don't know how a strong resonance within the driver's passband might affect things. Well, this certainly complicates things a bit.




                                      Steve Goff
                                      Steve Goff

                                      Comment

                                      • Hank
                                        Super Senior Member
                                        • Jul 2002
                                        • 1345

                                        #20
                                        Well, my 2 cents surround solution was the Speaker City T62:
                                        http://www.speakercity.com/ht_rear.shtml
                                        I really like this dipole implementation. The 45-degree faces seem to give a combination of direct radiating and traditional front/back dipole driver placement. One of our local audiophiles and speaker designer said the best surround he's heard was a scene from "Saving Private Ryan" in my HT. I actually bought the drivers and xover components from Speaker City - they gave me the outside measurements of the triangular cabinets and I built my own. You know me - cheap

                                        Comment

                                        • SteveG
                                          Member
                                          • Jul 2002
                                          • 31

                                          #21
                                          Originally posted by Hank
                                          Well, my 2 cents surround solution was the Speaker City T62:
                                          http://www.speakercity.com/ht_rear.shtml
                                          I really like this dipole implementation. The 45-degree faces seem to give a combination of direct radiating and traditional front/back dipole driver placement.
                                          Thanks for your suggestion, Hank. As you may notice in my message that started this thread, I already own some of the best dipole surround speakers available, the Fosgate/Audionics SD-180s. They were designed by John Dunlavy, and were among the first to angle the drivers out into the room. They also have Jim Fosgate's patented "Dual Drive" configuration, which means that the crossovers and speaker connections for the front and back pairs are independent, so the can be used as dipoles, as bipoles, and as independent speakers in a 7.1 configuration. They use the Vifa P13 woofer and an Audax tweeter, and the cabinets are quite large and well-made.

                                          But I'm interested in adapting Jon's speakers to this purpose because I'm not sure that dipoles, even the most capable, are the best for listening to multichannel music. If I bult a pair I could test that question, and if they didn't suit me I could use the drivers to make front channel speakers that will likely rival, or even surpass, my Revel M20s.




                                          Steve Goff
                                          Steve Goff

                                          Comment

                                          • Hank
                                            Super Senior Member
                                            • Jul 2002
                                            • 1345

                                            #22
                                            Steve, I noticed that, but the multi-channel issue has brought on an ongoing direct versus diffuse debate on the forums that is a bit like the interconnects arguments. Bottom line, for the new multi-channel formats, some people still like di/bipole diffusion and some like direct-radiating surrounds.

                                            Have you borrowed some direct-radiating speakers to try and see if you really like them best in your HT environment?

                                            Comment

                                            • SteveG
                                              Member
                                              • Jul 2002
                                              • 31

                                              #23
                                              Originally posted by Hank
                                              Steve, I noticed that, but the multi-channel issue has brought on an ongoing direct versus diffuse debate on the forums that is a bit like the interconnects arguments. Bottom line, for the new multi-channel formats, some people still like di/bipole diffusion and some like direct-radiating surrounds.

                                              Have you borrowed some direct-radiating speakers to try and see if you really like them best in your HT environment?
                                              I've tried direct-radiating speakers in my current 7.1 setup, and once used them exclusively in a 5.1 system. They work well for the back channels, but there are tradeoffs for the side channels. In part this was due to the design of the direct radiators, and I've wanted to try to design some that don't have the same problems for this application.

                                              I was into surround sound very early on, using a Hafler circuit and a single back channel in my steroe rig circa 1969. I built my own active surround sound decoder shortly thereafter (it had passive stearing), and was one of the first who tried to incorporate surround sound into a great stereo system. I've owned Schreiber decoders and just aboyut every generation of Jim Fosgate's designs, before and after he teamed up with Charlie Wood to form Fosgate/Audionics. When Harman gobbled them up I got the Citation 7.0 processor, one of Fosgate's designs, and stuck with it until I bought my current processor, the Integra Research RDC-7.
                                              And all the while I was an audio purist, having worked in the trade and informally with a friend who makes purist, two-channel gear with great phono sections. Beginning about 1980 I went to CES every year to man the room for this manufacturer, and for several years we used speakers I designed to demo his equipment. Over the years I've met and got to know a lot of folks in the industry, and have heard most of the good stuff out there, at CES, at showrooms, and in people's homes.




                                              Steve Goff
                                              Steve Goff

                                              Comment

                                              Working...
                                              Searching...Please wait.
                                              An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                                              Please push the back button and reload the previous window.'
                                              An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                                              Please push the back button and reload the previous window.'
                                              An internal error has occurred and the module cannot be displayed.
                                              There are no results that meet this criteria.
                                              Search Result for "|||"