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  • Jim Holtz
    Ultra Senior Member
    • Mar 2005
    • 3223

    Originally posted by capslock
    Jim, regarding Nomex vs. Exclusive, have a look at this: https://www.htguide.com/forum/showpo...&postcount=168

    The regular Nomex have no copper, at all, just a 4 mm alu ring that sits below the pole plate and outside of the VC. The Exclusives add about 0.4 mm of copper cladding on the pole (to just below the pole plate) and a conductive alu phase plug.

    The extra raggedness in the FR is in part due to the lower inductance (hence, an inductor in series will give in an FR more similar to the regular Nomex) and in part to the stiffer construction (extended former is attached to both cone and dustcap).
    Thank you for the response. I had searched and read the post but it didn't quite "click" in my brain until you put it in laymans terms for me here. It looks like the 882 is the mid to go for if I decide on using a Nomex cone driver. Impressive considering the cost. I'd love to actually hear one in a good implementation to see if the detail is more like the typical paper cone or if it is like metal cone drivers.

    ;x( I really enjoy reading your posts and in depth analysis of drivers. It really helps folks like myself make informed decisions.

    Best regards,

    Jim
    Last edited by theSven; 06 May 2023, 20:31 Saturday. Reason: Update htguide url

    Comment

    • Paul W
      Senior Member
      • Oct 2004
      • 549

      The new SS tweeter looks really great, but the 23-6 appears to have 6x the excursion! Does anyone have xmax for the 24-6?

      Jon,
      Have you found a non-destructive way to remove (and replace) the grill on the Accuton tweeters?
      Paul

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15259

        RS315HF Basic Measurements

        OK, let's look at one of the board favorites.

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        What this picture doesn't clearly convey is how tank like the construction of these are, and how heavy they are. Like the other two, the VC tinsels are woven into the spider.



        Others have pounded this driver pretty hard and lots of test data exists on the web; this is just so that there's some comparison with what I've posted above, to put things in perspective.


        Frequency response:
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        SPL and HD2 at "nominal" levels (defines the small signal behavior of the driver).
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        Same with HD3 plotted.
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        Very nice performance, definitely has a lower distortion signature than the TC2+ at these levels. For me, this is important, because I'm looking for something that's very clean at normal listening levels, and nonlinear LF performance is not the only criteria. YMMV, and with it's higher Xmax, the TC2+ can be pushed a little further at max out.


        Now, at approximately 100 dB, SPL + HD2.

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        And SPL + HD3.

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        At these levels the Dayton is clearly the leader, though the TC2+ is low in 3rd harmonic in the 100 Hz area.
        Last edited by theSven; 06 May 2023, 21:02 Saturday. Reason: Update image location
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        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15259

          Originally posted by Paul W
          The new SS tweeter looks really great, but the 23-6 appears to have 6x the excursion! Does anyone have xmax for the 24-6?

          Jon,
          Have you found a non-destructive way to remove (and replace) the grill on the Accuton tweeters?

          Remove, Yes. Non destructive to the tweeter functionality, Yes. Non-destructive to the grille, No. Wouldn't want to use the grille for the most part anyway. Well, it might be nice for the C23-6 or C24-6 if you just wanted to insert some felt diffraction control, but I have "loftier" goals in mind.

          I tried to find out what the Xmax for the C24-6 from Mad, they think it's pretty similar to the C32-6 (underhung geometry, though), but that's just guessing. Distortion testing would tell the real story. And if waveguide loaded, then even Xmax would be mitigated to a degree.

          More coming.
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          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15259

            C13-6 Part 2

            I haven't given up on this little guy (too much money sitting here for me to do that!), so I've been doing a little more tweaking and testing.

            First, I did remove the grille- not really hard to do, unless you wanted it left over in condition to re-install. That doesn't seem feasible, whatever glue they're using is pretty tenacious.

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            This is a pic sans grille, mounted up again for testing with just heavy felt surrounding the driver to control it's edge diffraction. That doesn't do anything aobut the circular groove cut for the grille.

            Mounted this way, here's a set of plots at 0-15-30 degrees off axis.

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            Still kind of ripplely, of course, and a significant spike at 16-17 kHz. Is that due to internal resonances or that silly grille mounting groove?


            Here's a pic with some additional felt, like I used to use on the M8 bookshelf two way project done for AudioXpress three years ago. Just a quick pass, no attempt to fully optimize as I did with the XT25 back then.

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            Here's a plot with the felt from 15 degrees off axis, which is what I consider the "primary" measurement point for tweeters, because it's more characteristic of the averaged on axis forward response than dead on axis. Think about it- it's a power and area sort of thing.

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            That's fairly interesting, and does show, IMO, that this part has some potential in the 2500Hz and up area.

            Next step in a weekend or two (biz travel next weekend) is a waveguide.

            ~Jon
            Last edited by theSven; 06 May 2023, 21:03 Saturday. Reason: Update image location
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            Comment

            • Paul W
              Senior Member
              • Oct 2004
              • 549

              Weekend waveguide

              Darn! I was hoping the grill could be replaced. I wanted to try a 23 or 24 down near 1k in a waveguide, but that seems very iffy...if that didn't work, just use them as a direct radiator in a different configuration. I wrote Accuton asking about 24 xmax so I'll let you know if they respond.

              Here is my first pass at a weekend waveguide (scrap 1.5" MDF). 90x40 with a D27TG-35 mule. Glue took a while to cure so I didn't get to spend much time with it. Directivity boosts the bottom end about 7db, maybe more (no direct comparison w/o waveguide). 27TG is ~flat from 1k up to 6k where it rolls off to "normal" output. 40 degrees vertical seems about right for what I want, but 90 degrees horizontal may be too narrow. Next weekend, I hope to cobble up some baffles for mid and bass drivers and listen to more than pink noise.

              Image not available
              Last edited by theSven; 06 May 2023, 21:04 Saturday. Reason: Remove broken image link
              Paul

              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15259

                Looks interesting, Paul! :T I'm looking to try the MCM waveguide in hopes of gettting a usable radiation resistance boost and distortion reduction in the 2 kHz up area- I'm pretty sure based on what John Krutke achieved with the 27TDFC that this will work well for distortion reduction in the 2 kHz to 6 kHz area with the Accutons.

                I'll be interested to hear what you find out about the 24-6 Xmax. For now, I've decided that I'm willing to commit the 23-6 to the cause for experimentation, primarily if I'm not satisfied with what I can do with the C13-6. For now, I'm going to work with the C13-6, as the smaller dome is a bit more extended- if the distortion preformance can be improved a bit, then I'll go that way.

                The C88's I picked up NOS are looking fairly good- I'm not going to post a full set of plots, as no one can buy these anymore, but FR and distortion looks good for the range of 300 Hz to 2000 Hz, without having to use one of my CE crossovers. Might wind up with something like the Natlie P network on these between tweeter and mid.

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                Last edited by theSven; 06 May 2023, 21:04 Saturday. Reason: Update image location
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                Comment

                • TacoD
                  Super Senior Member
                  • Feb 2004
                  • 1078

                  Again great measurements, also the german magazine HobbyHifi has measured the Aura NS12 and Dayton 12" RS351. The CSD of the Aura was a lot cleaner than the Dayton. Impulse plot of the Dayton had more ringing than the Aura (don't know if that's the correct term for this behaviour). The peerless XXLS has lower dirstorion in the lower frequencies compared to the Dayton or Aura.

                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15259

                    I'd expect the Dayton to have more ringing - look at it's response behavior in the 1500 to 2500 Hz area. Two different cone modes, it looks like, closely spaced- a peak and a notch.

                    With these parts, and the Peerless, it's all about tradeoffs and the target overall. The Peerless I've always heard had very good LF distortion, but really is strictly a subwoofer. The TC2+ has good LF performance, and can go a bit higher - cone behavior is fairly well behaved. The Aurasound is really a long throw woofer- with probably the best cone behavior I've ever seen in a 12" driver. The Dayton is somewhere in the middle- not as much Xmax as a TC2+, but still respectable; usable up higher, but not as high as the Aurasound; more grunt down low.

                    Makes me almost wonder if I couldn't try a hybrid at the high end; two LF 12's, with a relatively low frequency roll off (and positioned near the floor), and two Aurasounds running up to 250-300 Hz. Seems like a lot of trouble; and heavier than I would like. I'm doubting it can be made to work better than running the big 12's in an outboard W woofer cabinet (my first choice). That would at least kill some vibration and also deal with 2nd order stuff.

                    Maybe on the Arvo Part Venti.
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                    Comment

                    • JonMarsh
                      Mad Max Moderator
                      • Aug 2000
                      • 15259

                      Accuton C90/T6

                      Well, I'd better get this up at lunchtime today, because the way things are going I'm not going to have any time this week, maybe not next! Making a living is a real bear sometimes.


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                      First plot is FR measured at 2.83V on a 24" by 24" baffle; note the dip at marketer 1 is a characteritic of this baffle and measurement method.

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                      To get the "real" picture of the driver behavior, a near field measurement is done which essentially positions the mic co-planar with the front baffle.

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                      Not too disimilar to the C88, and for the most part what I expected. This confirms my judgement going into this that 250 Hz to 2 kHz was probably the best case operating range for the C90. Note where the notch is at 5 kHz there is a bobble in the impedance curve (not shown).

                      Next to examine was FR + distortion at "nominal level"- which due to the high sensitivity of this driver, is more like 93 dB.

                      FR + HD2
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                      FR + HD3
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                      Very low 2nd harmonic. Might have been nice if 3rd had been a little lower, but it's still pretty good. How much will it get worse with increasing level?


                      OK, let's push it up to around 100 dB, which is not as much more drive as other more typical midranges I've tested require.

                      FR + HD2 100 dB
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                      FR + HD3 100 dB
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                      What about higher harmonics?

                      FR + HD4 100 dB
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                      FR + HD5 100 dB
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                      If I hadn't checked and re-checked the scale on the HD4, I wouldn't have believed it. :T HD5 is pretty good, though higher.


                      Well, I want a little more for my $460 each, so lets take it up to 105 dB.


                      FR + HD2 105 dB
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                      FR + HD3 105 dB
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                      FR + HD4 105 dB
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                      Well, I'd certainly prefer it if the odd order stuff were a bit lower, but even at this level in the intended frequency range, the C90/T6 does deliver individual harmonic distortion spectra -50 dB or better, for the most part. Maybe I can live with that. :B

                      I'm certainly open to someone finding me something BETTER to test- and use- consider the doors thrown wide open. My main criteria is pistonic operation from 250 Hz to 2 kHz, and lower distortion. comparable sensivity would be a plus, but not mandatory.

                      Has anyone tested any of the AudioTechnology drivers, like the Flex Units or the C-Quenze 18 H 52? Or the ATD W18-4? ($595 at E-Speakers.COM)

                      Heck, I'll just go with these for now....

                      But I ought to look at the "lowly" Peerless 830883 at higher levels, too. It tests very well at 2.83 VRMS, 250 Hz to 2 kHz, 88-89 dB nominal. Wonder how it holds up at levels like the C90 will play at?
                      Last edited by theSven; 06 May 2023, 21:05 Saturday. Reason: Update image location
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                      Comment

                      • cotdt
                        Senior Member
                        • Oct 2005
                        • 393

                        Looks great, how about the Peerless 830883 at 105dB to compare? These Accuton guys seem to always do well in even-order distortion.

                        Comment

                        • Jed
                          Ultra Senior Member
                          • Apr 2005
                          • 3617

                          Jon, I'm curious to know how the C90 compares to the cheaper C88/89 little brother or even the C79 for that matter.

                          Comment

                          • FrancoB
                            Junior Member
                            • Jan 2005
                            • 20

                            Any chance you can put the SCC300 from Sonic Craft in one of your test sessions? If I remember correctly, you have a pair of those lying around somewhere.

                            Thanks for all the great work, Jon.

                            Franco

                            Comment

                            • JonMarsh
                              Mad Max Moderator
                              • Aug 2000
                              • 15259

                              I only have a pair of C88 right now, which use an aluminum VC former instead of titanium- and a different surround material. So, it wouldn't really be an accurate comparison, vis a vis the C89, as the design has been improved.

                              The usable range is similar to the C90, but they aren't as effecient, and don't have as much Sd, hence, they shouldn't play quite as loud down low (the C89 is more similar to the C88 than the C24-6 to the C23-6, as the C89 still has a conventional magnetic structure).

                              The C90 has a better design on the grille. The C88/89 WILL require special mounting techniques (probably something like a 3/16" aluminum plate becuase with it's large square plate for the back of the frame, if you put it in a conventionally cut 1" thick baffle, most of the rear opening would be masked. LF crossover of 250-300 should be good; Xmax supports up to 108 dB+ in dipole on the right size baffle down to 250 Hz.

                              The C79 goes quite a bit higher, but doesn't hold up as well down low- low frequency crossover should be 350 or higher. I don't have any of those to test- it's a more natural choice for C12 or C13 with a 3.5-3 kHz crossover, as long as you space them tight like Avalon does. I still think an Opus Klone with RS225 would work very nicely, as would an Eidelon Klone with Aurasound NS12-513A.

                              If you're into box speakers, that is.
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                              Comment

                              • ThomasW
                                Moderator Emeritus
                                • Aug 2000
                                • 10934

                                This thread is now linked in the Archived reference threads

                                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

                                • Ludvig
                                  Member
                                  • Jan 2006
                                  • 59

                                  Distortion plots

                                  How come that the distortion plots of the stiff cone drivers don't show any distortion peaks at "lower multiples" of the breakup peaks?

                                  If the driver has a big breakup peak at 2 kHz, it seem resonable to me that there should be a 2nd harmonic peak at 1 kHz and a 3rd harmonic peak at 667 Hz. Or am I interpreting the plots the wrong way?

                                  Comment

                                  • noah katz
                                    Senior Member
                                    • Dec 2005
                                    • 188

                                    "If the driver has a big breakup peak at 2 kHz, it seem resonable to me that there should be a 2nd harmonic peak at 1 kHz and a 3rd harmonic peak at 667 Hz."

                                    Because it's the first breakup mode, and there can be none any firster

                                    Harmonics are multiples, not submultiples.

                                    The term "subharmonic" is used, but IMO it's an oxymoron.
                                    ------------------------------
                                    Noah

                                    Comment

                                    • Ludvig
                                      Member
                                      • Jan 2006
                                      • 59

                                      Originally posted by noah katz
                                      Harmonics are multiples, not submultiples.

                                      The term "subharmonic" is used, but IMO it's an oxymoron.
                                      I think you are getting me wrong. I mean that if you have a 1kHz fundamental tone, it's second harmonic is placed at 2 kHz. Since the second harmonic of this 1 kHz fundamental tone is placed exactly at the break up frequency ( in this example), this harmonic will be amplified by the break up mode. In my world, this should result in a peak in the second harmonic distortion plot at 1 kHz.

                                      The same should result in a peak in the third harmonic distortion plot of a fundamental at 667 Hz.

                                      Comment

                                      • Dennis H
                                        Ultra Senior Member
                                        • Aug 2002
                                        • 3791

                                        Originally posted by Ludvig
                                        I think you are getting me wrong. I mean that if you have a 1kHz fundamental tone, it's second harmonic is placed at 2 kHz. Since the second harmonic of this 1 kHz fundamental tone is placed exactly at the break up frequency ( in this example), this harmonic will be amplified by the break up mode. In my world, this should result in a peak in the second harmonic distortion plot at 1 kHz.

                                        The same should result in a peak in the third harmonic distortion plot of a fundamental at 667 Hz.
                                        Yup, you've got it right Ludvig. About why all the peaks don't show up, or aren't as severe, I suspect it has to do with the nature of the breakup mode that is causing the resonant peak and what frequencies will stimulate it best. With the Seas metal cones, the third harmonic seems especially bad -- 1.5K tone stimulating the 4.5K ringing -- but I couldn't tell you which flexing mode is causing it.

                                        Comment

                                        • Ludvig
                                          Member
                                          • Jan 2006
                                          • 59

                                          Originally posted by Dennis H
                                          With the Seas metal cones, the third harmonic seems especially bad -- 1.5K tone stimulating the 4.5K ringing -- but I couldn't tell you which flexing mode is causing it.
                                          What you are describing is present in Seas datasheet of the W18 and W22 distortion plots, but in Jon's Praxis measurements, both second and third order distortion plots are flat like a floor in that region, and that's confusing me.

                                          Of course the plots will differ more or less because of different measurement techniques and environments, but I think that this kind of fundamental distortion signature should be present to some degree.


                                          This link is for the W18, since Seas has removed the distortion plot in the W22 datasheet, but the distortion signature is comparable between the two drivers regarding the "breakup related" distortion peaks.

                                          Comment

                                          • capslock
                                            Senior Member
                                            • Dec 2004
                                            • 410

                                            Well, they are certainly there in the HobbyHifi and Klang&Ton reviews!

                                            Comment

                                            • noah katz
                                              Senior Member
                                              • Dec 2005
                                              • 188

                                              Ludvig,

                                              Yes, I misunderstood you.
                                              ------------------------------
                                              Noah

                                              Comment

                                              • JonMarsh
                                                Mad Max Moderator
                                                • Aug 2000
                                                • 15259

                                                Originally posted by Mark K
                                                Yes Jon,

                                                Please do buy a C24-6 and test it...Sheesh, just when I thought there weren't any high end drivers that are worth the money, the C23-6 has to look pretty darned good. I guess that extra 5mm is worth some distortion. I wonder if the C24-6 is any better.

                                                Good work on all this stuff. I'm still curious about the 3/4 Seas, but it doesn't look like an uber winner.

                                                Jed,

                                                I've looked at the C44 and it's very good. But I only compared it with the mdt55. There isn't alot in this range. Just not alot of dome type tweeters or 2" midranges. Still, it looks like the C23-6 or C24-6 will handle a lower xover. Maybe it should be mated to an 8"...

                                                I've got to get my hands on some accuton tweeters...

                                                Still looking for the holy grail 3/4 tweeter...
                                                Well, the C-24 is somewhat at the other end of the spectrum, given it's dome size...

                                                Mine came in today, but there's a bit of a Twilight Zone element at work here- the cartons say C30N-6, there's another sticker with handwriting saying C24-6. BUT, the published data at Madisound for the C24-6 calls out the same frame size, flange, and cutout as the C23-6, whereas THESE tweeters are clearly the same frame size as a C13-6 (which makes more sense using a similar underhung motor), though clearly they have a 30 mm inverted dome.

                                                Hmmmmmm. I'd hate to order these again and get the bigger frame/package. Gonna have to email Madisound and see what gives.

                                                ~Jon
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                                                Comment

                                                • atalio
                                                  Junior Member
                                                  • May 2006
                                                  • 10

                                                  "What you are describing is present in Seas datasheet of the W18 and W22 distortion plots, but in Jon's Praxis measurements, both second and third order distortion plots are flat like a floor in that region, and that's confusing me."

                                                  It appears that some or all of Jon's woofer distortion plots graph the harmonic distortion component at the frequency (of the fundamental) causing the distortion, not at the frequency of the distortion component itself. So divide the frequency scale by two when interpreting the second harmonic distortion, and divide by three for third harmonic distortion.

                                                  Or simply interpret the plots differently than you may be used to. For second harmonic plots, for instance, interpret the plot as "at this fundamental frequency, the second harmonic distortion produced is depicted directly below (at the same frequency as) the excitation value."

                                                  SEE CORRECTION BELOW
                                                  Last edited by atalio; 15 May 2006, 10:27 Monday. Reason: To inform readers of correction post below

                                                  Comment

                                                  • Ludvig
                                                    Member
                                                    • Jan 2006
                                                    • 59

                                                    Originally posted by atalio
                                                    It appears that some or all of Jon's woofer distortion plots graph the harmonic distortion component at the frequency (of the fundamental) causing the distortion, not at the frequency of the distortion component itself.
                                                    I agree that this is the only reasonable explanation for the different looking distortion plots, even if it surprises me why the program presents it in such a complicated way.

                                                    If this is true, it put new light on many of the drivers, and much of the conclusions and praises of different drivers in this thread are no longer correct.

                                                    Comment

                                                    • TacoD
                                                      Super Senior Member
                                                      • Feb 2004
                                                      • 1078

                                                      Interesting remarks Atalio & Ludvig.

                                                      Comment

                                                      • JonMarsh
                                                        Mad Max Moderator
                                                        • Aug 2000
                                                        • 15259

                                                        Originally posted by atalio

                                                        It appears that some or all of Jon's woofer distortion plots graph the harmonic distortion component at the frequency (of the fundamental) causing the distortion, not at the frequency of the distortion component itself. So divide the frequency scale by two when interpreting the second harmonic distortion, and divide by three for third harmonic distortion.

                                                        Or simply interpret the plots differently than you may be used to. For second harmonic plots, for instance, interpret the plot as "at this fundamental frequency, the second harmonic distortion produced is depicted directly below (at the same frequency as) the excitation value."

                                                        This interpretation is correct- this is how Praxis works. The same technique is used for instrumentation plotting amplifier distortion, for example, if the plot is of the Xth harmonic (second, third, whatever). The distortion level for that harmonic generated at the plotted frequency is shown. This is why the plots stop at lower frequencies than the frequency response- such as 20 kHz for 2nd harmonic (because measurement window only goes to 40 kHz), etc.
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                                                        Comment

                                                        • JonMarsh
                                                          Mad Max Moderator
                                                          • Aug 2000
                                                          • 15259

                                                          Re C24-6/C30N,

                                                          Dinner with daughter interrupted measurements late yesterday afternoon once I finally had a little spare time. No HD measurements yet.

                                                          The basic frequency response shows some elevation/roughness in the 3-5 kHz region, apparently due to diffraction; this is WITH a felt sheet surrounding the tweeter mounted on test baffle. Might still want a little contouring in the crossover, I expect. s

                                                          This is basically a C23-6 in the same size package as the C13-6, with the underhung neodymium motor. Very curious to see how the distortion holds up compared to the C23-6. Besides being much smaller, the C30N is about 3 dB more efficient.

                                                          Upper breakup is pretty well controlled in level. Wish it were a bit higher up, but for a 30 mm diaphram, what can you expect? Unless you go diamond....

                                                          Click image for larger version

Name:	C30NFeltSPL.jpg
Views:	90
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                                                          HD next weekend if all goes well.
                                                          Last edited by theSven; 06 May 2023, 21:05 Saturday. Reason: Update image location
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                                                          Comment

                                                          • Ludvig
                                                            Member
                                                            • Jan 2006
                                                            • 59

                                                            Originally posted by JonMarsh
                                                            This interpretation is correct- this is how Praxis works.
                                                            Sorry, I misread the post of Atalio. You, Atalio and I are meaning the same thing. The distortion plots should peak at the frequency of the fundamental that is causing the distortion peak.

                                                            OK, if we can agree on that Praxis is following this standard, then we are back at the beginning again. Why is the stiff cone driver distortion plots flat at the half/third frequency of the resonant peak when it is assumable that there should be some kind of peak? Again, W18 and W22 datasheets show what I mean.

                                                            Comment

                                                            • atalio
                                                              Junior Member
                                                              • May 2006
                                                              • 10

                                                              Correction to distortion plot post

                                                              Correction regarding distortion plots (underline indicates modificaton to previous post):

                                                              Unlike Jon's plots, it appears that the Seas woofer distortion plots graph the harmonic distortion component at the frequency (of the fundamental) causing the distortion, not at the frequency of the distortion component itself. So in Jon's plots, divide the frequency scale by two when interpreting the second harmonic distortion, and divide by three for third harmonic distortion.

                                                              For the Seas: For second harmonic plots, for instance, interpret the plot as "at this fundamental frequency, the second harmonic distortion produced is depicted directly below (at the same frequency as) the excitation value."

                                                              For Jon's: For second harmonic plots, for instance, interpret the plot as "at this fundamental frequency, the second harmonic distortion produced is depicted at twice the excitation value."

                                                              Hopefully this clarifies the issue of the discrepency between the two different methods. Note also that SoundEasy uses the same method as Seas for plotting distortion.

                                                              Comment

                                                              • atalio
                                                                Junior Member
                                                                • May 2006
                                                                • 10

                                                                Originally Posted by Ludvig

                                                                If this is true, it put new light on many of the drivers, and much of the conclusions and praises of different drivers in this thread are no longer correct.
                                                                I agree that the use of the two distortion display methods could be a source of confusion. However, IMO, neither method is incorrect.

                                                                In any case, a statement accompanying distortion graphs could help avoid misinterpretation.

                                                                Comment

                                                                • Ludvig
                                                                  Member
                                                                  • Jan 2006
                                                                  • 59

                                                                  Originally posted by atalio
                                                                  Correction regarding distortion plots
                                                                  Excellent summary!

                                                                  Comment

                                                                  • Ludvig
                                                                    Member
                                                                    • Jan 2006
                                                                    • 59

                                                                    Originally posted by atalio
                                                                    I agree that the use of the two distortion display methods could be a source of confusion. However, IMO, neither method is incorrect.

                                                                    In any case, a statement accompanying distortion graphs could help avoid misinterpretation.

                                                                    You are right that both methods are of course correct if we know in what way to interpret them. But I feel that many like me has read the distortion plots in the "SEAS/SoundEasy way" which will make the tested drivers look cleaner than they actually are when interpreting them the "Praxis way".

                                                                    Comment

                                                                    • atalio
                                                                      Junior Member
                                                                      • May 2006
                                                                      • 10

                                                                      Originally posted by Ludvig
                                                                      You are right that both methods are of course correct if we know in what way to interpret them. But I feel that many like me has read the distortion plots in the "SEAS/SoundEasy way" which will make the tested drivers look cleaner than they actually are when interpreting them the "Praxis way".
                                                                      I agree with your assessment. Perhaps this is an issue that should also be taken up with the Liberty Instruments staff?

                                                                      I think the SEAS method is probably preferrable for loudspeaker development -- one can quickly view a frequency range on the graph and simply determine whether or not excitation in that range will produce distortion. In other words, one can readily determine the usable frequency range of the driver without having to go through some mental gymnastics.
                                                                      Last edited by atalio; 15 May 2006, 12:09 Monday. Reason: "A-B-E. A - Always, B - Be, E - Editing; Always be editing.

                                                                      Comment

                                                                      • Dennis H
                                                                        Ultra Senior Member
                                                                        • Aug 2002
                                                                        • 3791

                                                                        Hopefully this clarifies the issue of the discrepency between the two different methods. Note also that SoundEasy uses the same method as Seas for plotting distortion.
                                                                        As Jon explained, there is no discrepancy. Praxis plots distortion just like everybody else. As to why Jon's plots look different it's no doubt due to different measurement conditions and techniques -- anechoic vs in room, discrete tones vs chirp, gated vs not. With all the measurements you see on the net, you can usually compare drivers measured by the same person but not by different people.

                                                                        Comment

                                                                        • atalio
                                                                          Junior Member
                                                                          • May 2006
                                                                          • 10

                                                                          Originally posted by Dennis H
                                                                          Praxis plots distortion just like everybody else. As to why Jon's plots look different it's no doubt due to different measurement conditions and techniques.
                                                                          Dennis, that's what I would like to think and would expect, but the woofer distortion measurements I've seen earlier in this thread seem to strongly suggest otherwise. Perhaps we could get some corroboration from the Praxis folks either way...

                                                                          Comment

                                                                          • Dennis H
                                                                            Ultra Senior Member
                                                                            • Aug 2002
                                                                            • 3791

                                                                            I think you're being faked out by the fact that the harmonics are shown in dB SPL, not percent distortion like Seas uses. You have to measure the difference in dB between the fundamental and the harmonic, i.e. normalize the fundamental to a flat line, to get % distortion. Praxis can do that but Jon chose not to.

                                                                            Comment

                                                                            • atalio
                                                                              Junior Member
                                                                              • May 2006
                                                                              • 10

                                                                              Originally posted by Dennis H
                                                                              ...harmonics are shown in dB SPL, not percent distortion like Seas uses. You have to measure the difference in dB between the fundamental and the harmonic, i.e. normalize the fundamental to a flat line, to get % distortion.
                                                                              The issue I'm having is the one Ludvig raised. I'm not seeing any distortion peaks at submultiples of the resonance frequency.

                                                                              Correct me if I'm wrong, but I believe the "resonance-distortion" phenomena we're referring to is relevant when viewing the distortion in dB. It's not contingent on the unit of measure--it shows up in both dB and % distortion plots. For instance, SoundEasy displays distortion in dB, and the resonance-distortion is visible in its plots.

                                                                              I can only infer, but it seems that SE measures distortion dB RELATIVE to the acoustic output signal, not the generated signal. Otherwise, you would get heavy modulation of the distortion value (referencing the acoustic output signal would be equivalent to the speaker output FR normalization you refer to). Even if one were to remove the generated signal amplitude "modulation effect" (assuming it's there), it does not appear to explain the lack of harmonic distortion at the submultiples, unless the subharmonic distortion is somehow getting dwarfed by the modulation effect, which I feel is unlikely.

                                                                              As a side note, it may avoid confusion for others if we separate out any discussion of % distortion from normalizing the frequency response curve, as one does not imply the other.

                                                                              Zaph's L18 plots at http://www.zaphaudio.com/6.5test/hd.html illustrate some of these issues. Note that his setup creates a comb filter measured response, but it does not influence the distortion curves because the signal in dB is referenced to the acoustic output.
                                                                              Last edited by atalio; 18 May 2006, 04:33 Thursday. Reason: inaccuracies and clarification (see underlined text for modifications)

                                                                              Comment

                                                                              • Dennis H
                                                                                Ultra Senior Member
                                                                                • Aug 2002
                                                                                • 3791

                                                                                Zaph's L18 plots
                                                                                Zaph had a feedback issue with his soundcard and he acknowledges that his curves are not correct and shouldn't be compared to anyone else's. Just because you don't see what you expect to see in Jon's curves doesn't mean there's anything wrong with Praxis and your proposed explanation is quite a stretch IMO. I don't see any evidence that it's true and without proof I suggest we stop any such claims before they become internet legend. There are plenty of other ways to explain Jon's curves as I noted earlier.

                                                                                Comment

                                                                                • Hdale85
                                                                                  Moderator Emeritus
                                                                                  • Jan 2006
                                                                                  • 16075

                                                                                  Just a little offtopic question? I just purchased a Sound Blaster Audigy 2 notebook sound card. Is this pretty good for taking measurements or not?

                                                                                  Comment

                                                                                  • JonMarsh
                                                                                    Mad Max Moderator
                                                                                    • Aug 2000
                                                                                    • 15259

                                                                                    Depends on what software, possibly. This is an external USB interface audio module? LspCAD has problems with some of the other Audigy cards. Basically, for speaker measurements you want something that doesn't have EAX or any of the other processign crap you have to disable, and perferably true 24 bit without gimmicks. Sadly, most of the Audigy cards won't do 24/96 cleanly. Not even the PCI boards.

                                                                                    The best thing is to check with the people making the software you're considering using, and go with one of their recommended configurations. I use an MAudio 24/192, it's been flawless. They have a USB external solution that works pretty well, too.
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                                                                                    Comment

                                                                                    • Hdale85
                                                                                      Moderator Emeritus
                                                                                      • Jan 2006
                                                                                      • 16075

                                                                                      Yea this is a PCMCIA card and i got it because i wanted to output 5.1 cause i use it to upconvert dvd's to my LCD tv. Just thought it might work good? its say it'll do 24 bit but not sure if it really does? Anyway to test that?

                                                                                      Comment

                                                                                      • JonMarsh
                                                                                        Mad Max Moderator
                                                                                        • Aug 2000
                                                                                        • 15259

                                                                                        Read what the guys who sell the stuff say in their manuals or guides. Audigy's aren't recommended for Praxis because they don't work as claimed in many cases. They're really primarily gaming cards.
                                                                                        the AudioWorx
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                                                                                        Resistance is not futile, it is Volts divided by Amperes...
                                                                                        Just ask Mr. Ohm....

                                                                                        Comment

                                                                                        • Hdale85
                                                                                          Moderator Emeritus
                                                                                          • Jan 2006
                                                                                          • 16075

                                                                                          Well sounds a lot better then my onboard stuff. But maybe when I get to the stages of needing to measure performance i could get somthing better.

                                                                                          Comment

                                                                                          • JonMarsh
                                                                                            Mad Max Moderator
                                                                                            • Aug 2000
                                                                                            • 15259

                                                                                            It's a question of electrical functionality and consistency of how the drivers work, PLUS being able to turn off "features" like EAX that add "Effects" for games and music, but are just "noise" for measurements. Most of creatives 24 bit products won't actually work at 24 bits, and many which claim to work at 96 kHz won't. At least, not according to the folks who produce Praxis.

                                                                                            Gaming audio cards and high end audio cards are very different animals, use different chipsets, and have different standards for the drivers and usability.

                                                                                            Check out the Libinst site and their recommendations for Praxis, and check out the Maudio site, you'll see what I mean. The MAudio cards are designed for semi-pro recording, and also work very well in HT applications, due to the DACs and circuitry they use. They're also quite good for measurement, and recomended by LspCAD and Soundeasy.
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                                                                                            Just ask Mr. Ohm....

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