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  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15261

    #91
    Well, I'd say tweeter power handling is ALWAYS an issue for any project (except maybe a humongoid line array). But usually it's distortion that's more a concern, which is why the next batch of measurements will be on tweeters, including something old and someting blue, just for historical relevance or perspective.

    Then again, I'm not trying or expecting to get 115 dB levels in the Arvo's. OTOH, 100-107 dB is the LF goal (40Hz to 50 Hz). The issue becomes what drivers, what crossover points, what LF power handling. The waveguide concept could help both directivity and lowering the LF distortion, depending on it's feasibility with chosen midwoofers. I have a feeling that we'll be able to make it work out in an example I'm considering, but that a direct radiator option may be desired by some.

    So, if a 3/4" dome with nice upper end characteristics will work with a waveguide (maybe H1283, also C13-6), then a good midrange 1" dome may be fine without the waveguide (RS28a-4), but won't have the improved directivity control, and may not be a smooth/flat in the top octave. Seems a reasonable/understandable tradeoff, considering the expense and construction issues, no?
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    Comment

    • Brian Bunge
      Super Senior Member
      • Nov 2001
      • 1389

      #92
      Jon,

      Did you happen to notice that PE also has a new Dayton line of waveguides? I'm just wondering if they'd work better or at least as well as the ones offered at MCM.

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15261

        #93
        I dropped on by PE but didn't see anything newer than what they had up a couple of months ago- 75 degree conical waveguides with relatively high cutoff frequencies, due to the flare rate and tighter dispersion. For example, this 8" diameter model has a cutoff of about 2200 Hz.

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        Even the 12" one doesn't go that low- ~ 1200 Hz, and it's pretty huge and deep. Part of the price for 75 degree control, which is also narrower than I'd prefere (say, 90 degree included angle).

        Was there something newer that the search engine doesn't turn up? I'm all ears...

        ~Jon
        Last edited by theSven; 06 May 2023, 20:47 Saturday. Reason: Update image location
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        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15261

          #94
          OK, it's Sunday, and I'm well into doing some new testing on tweeters, from "Goldie-Oldie's" to some very recent introductions. There's a bit of work to do to prepare image files to upload. It's cool working with Praxis and the Acco mic, because now I can look at tweeter stuff out to 40 kHz with some confidence. :B

          More tweeters to test, too, this afternoon.

          Now, this is not going to be the super in detail stuff that MarkK does, for now it's just a 10,000 ft high altitude survey (well, using high resolution cameras, of course!) to get an idea of trends in key areas between the drivers. Because of the time that would be involved doing proper diffraction control between each driver, and because the major effects from diffraction issues show up between 5 kHz and 12 kHz, I didn't spend time on that. I'm more concerned with this survey with LF behavior, including basic distortion patterns, and top octave/breakup behavior. Latter I'll go back and look at a few drivers in more detail.
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          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15261

            #95
            MB Quart MCD1 Dual Magnet as built for Avalon Acoustics

            This is a version of the MCD1 built specifically for Avalon Acoustics. In early production they used a modified version of the standard square frame MCD1. This version includes a different grille and other updates.



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            Here's the SPL data at 5 dB/div; again, I wouldn't worry too much about the lumpiness in the 5 kHz to 12 kHz area... still, the measured window is fairly tight (~ +/- 2.5 dB)

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            Now, let's look at the FR and 2nd harmonic distortion, at ~90 dB




            This may not look state of the art, but consider that the basis of this tweeter was available in the late 80s, almost 20 years ago. Ever measured most standard tweeters from that time frame?


            Now, the FR and 3rd Harmonic from same measurement.

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            Not really too shabby, is it? no copper in the gap, either. While I wouldn't run this tweeter as low as Avalon did, I'd be inclined to say that from 2 kHz and up, it's a pretty respectable performer, particularly for it's day. I used it in a few projects, usually at about 2 or 3 kHz and above. The very first CE 8" two way I did with a Focal woofer used this tweeter crossed steep at 1500 Hz.


            The only thing "icky" about it is that 14 dB spike at breakup. The "oil can" resonance at 25 kHz is pretty wicked.
            Last edited by theSven; 06 May 2023, 20:47 Saturday. Reason: Update image location
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            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15261

              #96
              Seas H1189

              This is the tweeter I used in the first Modula MTM design; it has good distortion characteristics pushed hard with LF three tone tests, even compared with the Seas Millenium Excel.

              On the left.

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              Here's the SPL plot.

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              No upper range break up; of course, response does taper off as you go off axis above 10 kHz.


              Frequency response and 2nd Harmonic distortion at ~90 dB SPL

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              Easy to see why this is a popular tweeter for ~ $30 USD. Wish the 2nd harmonic were a bit lower. Can't help but wonder how much contribution to IM that makes.


              And with 3rd Harmonic distortion
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              Last edited by theSven; 06 May 2023, 20:48 Saturday. Reason: Update image location
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              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15261

                #97
                Seas H1212

                The H1212 is sort of a controversial driver from Seas. In many ways just an aluminum dome version of the H1189, it's general behavior is pretty fair, but it does have a rather serious breakup mode at the top.

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                SPL, at 5 dB/div
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                Distortion is quite low on the sample I measured at nominal 90 dB SPL- certainly one of Seas's best efforts.

                Here's the SPL and 2nd Harmonic graph
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                And here's the SPL and 3rd Harmonic plot
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                Last edited by theSven; 06 May 2023, 20:48 Saturday. Reason: Update image location
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                Comment

                • JonMarsh
                  Mad Max Moderator
                  • Aug 2000
                  • 15261

                  #98
                  Seas H1283

                  This is one I had significant hopes for based on the published data. I've been hoping to find a moderate cost 3/4" tweeter with good distoriton numbers and a break up mode at higher frequency and possibly reduced amplitude. The published SEAS data indicate this could be the one.


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                  First, the SPL data, at 5 dB/div.
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                  Not quite what I was expecting. Looks pretty good up to 18 kHz, then a huge dip, and a pretty serious spike up at 36 kHz. Is this an artifact of the phase difuser, I was thinking? But, if you look closely, there isn't one! Don't know what to make of the physical cause- looks like two resonances close in frequency, maybe even three (see the second dip at ~ 32 kHz).


                  SPL and HD2 data in this plot.
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                  Tsk, tsk.


                  SPL and HD3 data follows.
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                  Much better, if you stay above 2500 Hz. Still, that basic 2nd order nonlinearity is probably going to make this a mean, lean, IM generating machine.
                  Last edited by theSven; 06 May 2023, 20:49 Saturday. Reason: Update image location
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                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15261

                    #99
                    SEAS Millenium Excel

                    OK, obviously no Seas Tweeter comparison would be complete without some reference to the Millenium Excel. Sorry, I don't have any of the other Excel models; many hold them in high regard.

                    On the right, of course.

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                    This is the same tweeter MarkK tested. I did add a little felt surrounding the tweeter faceplate, but it's still not as flat as I expected. I think this is mostly due to diffraction on this baffle- as I explained above.

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                    Now, the SPL and HD2 graph.

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                    Pretty solid performance, and let's admit a lot of us like that extra 2nd harmonic. Still, it won't help IM performance.


                    Now, the SPL and HD3 plot.

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                    Farily solid performance all around. Maybe that's what makes this tweeter a favorite with many folks- well balanced performance, and very nice build quality.

                    Sill, the distortion performance is not all that impressive if you compare it with the H1212. Somewhat perplexing, given the fancy schmancy neodymium motor and chamber construction.
                    Last edited by theSven; 06 May 2023, 20:50 Saturday. Reason: Update image location
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                    Just ask Mr. Ohm....

                    Comment

                    • JonMarsh
                      Mad Max Moderator
                      • Aug 2000
                      • 15261

                      NorthCreek D28

                      The NorthCreek D28, like the Dayton RS28a, is an Usher tweeter design using a 28 mm dome, with copper over the pole piece to reduce inductivity modulation and distoriton.

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                      Here's the measured frequency response, with a small felt piece around the tweeter, at 5 dB/div.

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                      Nothing to complain about here, and one of the flattest I've measurede 1 kHz to 20 kHz.


                      Let's look at distortion- first HD2.

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                      Well, that was something of a surprise- I'm not knowledgable enough about the Usher motor to make any comment, other than it's higher than I would expect top see at 90 dB SPL.

                      What about HD3?

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                      This looks better, but neither would incline me to run this tweeter as low as 1500 Hz, as NorthCreek suggests.
                      Last edited by theSven; 06 May 2023, 20:50 Saturday. Reason: Update image location
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                      Comment

                      • JonMarsh
                        Mad Max Moderator
                        • Aug 2000
                        • 15261

                        Dayton RS28a-4

                        OK, since we're looking at Usher sourced parts, we have to visit the RS28a, of course. Just the unshielded version, because that's all I have.

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                        SPL from product parts sourced about six months ago.
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                        At 5 dB per division, and as noted earlier, I'm not taking any diffraction control measured, and these are not smoothed measurements. Dome breakup is at 30 kHz, fairly narrow Q, though look at the downward dip and recovery afterwards. This is one of the more "neutral" sounding metal domes I've heard, and this high a breakup mode is remarkable given it's 28 mm diameter.

                        Let's look at distortion, something the RS28a gets a lot of press about. First, HD2...
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                        Definitely lower than the NorthCreek, though not hugely so.


                        Next, HD3.
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                        Pretty dang clean above 2 kHz, but not as good below.


                        What about the "early prototypes" and their reported performance?


                        Here's the HD2 and HD3 plots from the protype MarkK sent me to look at many moons ago.

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                        Now, these are only snap shots at a moderate level (~ 90 dB), and don't speak to behavior as you might really push and stress them. Still, at these levels 2nd harmonic is not all that different, actually a bit better in the newer one. 3rd harmonic shows a bit more variation, but quite within what I'd expect for different production samples, much less prototype vs production.
                        Last edited by theSven; 06 May 2023, 20:51 Saturday. Reason: Update image location
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                        Comment

                        • cotdt
                          Senior Member
                          • Oct 2005
                          • 393

                          Below 2kHz, the Northcreek and RS28A tweeters are playing louder than the other tweeters tested. Since harmonic distortion increases nonlinearly with output, it's difficult to compare low-end performance between the tweeters. Wouldn't they also have to be level-matched for an easier comparison?

                          Comment

                          • JonMarsh
                            Mad Max Moderator
                            • Aug 2000
                            • 15261

                            We're only talking a few db- at a relatively moderate level like 90 dB playback, there shouldn't be any real difference. At 100 dB+, I'd expect otherwise. 3rd harmonic is particularly telling.
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                            Comment

                            • JonMarsh
                              Mad Max Moderator
                              • Aug 2000
                              • 15261

                              Accuton C23-6

                              Ok, I've got some other parts around here I don't often write about or discuss becuse they're "not on the radar" for a lot of users due to cost or availability, but that doesn't mean they don't deserve some investigation or comment. Next up is the Accuton C23-6, which I've used in some systems before, including the MkII version of the M8 two way.

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                              This tweeter uses a ceramic (aluminum oxide) inverted dome, and was designed for two and three way applications.

                              Here's the SPL plot- could do with a little more attention to diffraction control in the mounting, but you can see the basic performance.

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                              Because of the proprietary manufacturing process, including the odd little ears in the diaphram, the cone modes are not high Q, and the upper peak at 27 kHz is relatively low Q compared with what we see with other hard dome tweeters.

                              Here's the HD2 distortion plot. No, this isn't a typo or screw up. Measurement conditions were carefully controlled and duplicated between the different models. This is just a good motor design.

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                              Last is the HD3 plot for distortion....

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                              Pretty solid performance, wouldn't you say? What's not to like, except the $175 price.... each. :E
                              Last edited by theSven; 06 May 2023, 20:51 Saturday. Reason: Update image location
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                              Just ask Mr. Ohm....

                              Comment

                              • JonMarsh
                                Mad Max Moderator
                                • Aug 2000
                                • 15261

                                Accuton C13-6

                                Well, this is a sort of cute little tweeter, though when you heft it, you have to wonder if you're gettting your money's worth- it has a neodymium magnet, and weighs hardly anything. That, plus it's just a lot smaller than it's "big brother", the C23-6. Again, a VERY well controlled upper resonance- like it's big brother, maybe even more so. Sort of like the best of worlds between soft domes and metal hard domes.


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                                Here's the SPL plot, and it's fairly smooth from 3 kHz to 20 kHz, though it's disappointing that it rolls off below 3 kHz, higher than the published plot. Since it's on a 24" X 24" baffle like the other tweeters, you can't blame mounting. Realistically, lowest crossover is probably 3 kHz or higher. Similar to the C12-6 in that regard. It uses an underhung magnetic structure, and is rated about 3 dB higher efficiency than it's big brother. I left it at the same drive level, just to see how it would do. Overall, it seems more like 4-5 dB more sensitive.

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                                Here's the HD2 plot.

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                                Pretty respectable performance considering the sensitivity difference and smaller dome.



                                Here's the HD3 graph.

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                                Not great, but not bad. Also have to wonder how it might do grafted to a waveguide. The feasibilitiy of that would depend on being able to remove the perf grille. I think it's just glued in. That, and how brave I might be messing with a $200 tweeter.
                                Last edited by theSven; 06 May 2023, 20:52 Saturday. Reason: Update image location
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                                • cobbpa
                                  Senior Member
                                  • Apr 2005
                                  • 456

                                  So last week's & this week's tests are telling us that the oft-recommended Dayton & Seas combo makes a potent combination, and that the "for the money" moniker isn't really a necessity for that claim, right? Or would the more expensive drivers outshine the more budget ones in other tests?

                                  Comment

                                  • capslock
                                    Senior Member
                                    • Dec 2004
                                    • 410

                                    Thanks, Jon, that's really impressive!

                                    Just a few quick comments as I am scanning through the results:


                                    TDFC:
                                    - really amazing that a soft dome will play up to 30 kHz without serious droop or wiggles
                                    - wonder what is causing the high second harmonic distortion, if it was the ferro, the TBFC would be as poor; on the other hand, the TDC (noferro 550 in Germany) tested really well, so it doesn't look like cone flexing, either
                                    -> production tolerances? could you retest another TDFC and maybe a TDC for comparison? or maybe the TDFC was colder than the TBFC?

                                    TBFC:
                                    - I wonder if the dip at 22 and the peak at 26 kHz are the result of destructive interference between cone edge and center and a local cone mode interacting
                                    - maybe the 29TAF is better regarding those breakups?

                                    22TAF
                                    - looks like flux modulation to me, but could also be flexing distortion from the oversized surround

                                    North Creek & RS28:
                                    - the motor geometry is hard to beat in terms of symmetry, so I would expect those to stay good at high SPLs
                                    - the copper cladding is pretty thin (especially for the North Creek, which has only one sleeve) so the second harmonic might be flux modulation

                                    Accuton:
                                    - I didn't know the C23-6 already had a cleaned up motor design
                                    - does it use ferro?

                                    Comment

                                    • ergo
                                      Senior Member
                                      • Mar 2005
                                      • 675

                                      Hi Jon,

                                      I have a pair of Seas T29CF001 in my new prototype phase speaker that I could measure...

                                      I also have my friend's Praxis for use. If you could send me the Praxis configuration file that I could load and some instructions of how far you measure etc. I could try to make similar measurement of SPL and harmonics.

                                      ***

                                      I have had the speakers "singing" for about a week. These are T29CF001, W18NX and SS8565 for low end. I like how this tweeter sound very much. I also have (only for few days more) a pair of W17E002 and Millenniums and comparing the tweeters - I would say that this far the T29CF001 performs at least as well as Millennium.

                                      Ergo

                                      Comment

                                      • JonMarsh
                                        Mad Max Moderator
                                        • Aug 2000
                                        • 15261

                                        Hello Eric,

                                        Strangely, that's an OLD C32-6 I bought several years ago. Re the TBD, if it was just propagation, I'd think we'd just see a dip- both of the metal seas seem to go into a "
                                        nutso" breakup with fairly chaotic behavior. At least mine do.
                                        Now, the 27TDFC plays pretty much like the factory data sheet, as do several other tweeters, which gives me some confidence in these measurements.

                                        Mic is an ACCO Pacific 1/2", as described above, with CAL file data entered (it's pretty damned flat without that, even.)



                                        Nothing magical in the configuration file. Hardware AD/DC is set for 96 kHz, the stimulus is a log swept chirp 200 msec long, (voltage at speaker terminal independently verified by scope) which is first set for acquisition type of impulse response norm via chirp to set the windowing, FFT size is 16,384 points, BlackmanHarris4 window, 1 avg with coh mode, (at my 6" measuring distance, that's about 93 usec on the front side, then 16 msec on the back side). Then it's set for frequency response magnitude and phase acquisition, flex windowing, and SPL and phase are measured.
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                                        Comment

                                        • dlr
                                          Senior Member
                                          • Feb 2005
                                          • 402

                                          About that Hales tweeter and...

                                          Thanks for all of that useful info. I've been looking at those Accuton tweeters for a while, wondering how they stack up against the current favorites. Looks like they are worth considering, even if so expensive.

                                          I am still unsure about the just how audible the differences are between, say, two similar, very good 3/4" drivers as long as they are used well within their limits.. I've found, for example, little audible difference between the OW1 and XT19. I recently put the XT19 back in my 3-way and after adjustments the system seems nearly identical. I cross LR2 @3500. I don't think that I could tell you which driver was in place based on listening alone.

                                          On tweeter testing, will you be able to test that Hales tweeter? I ask because I am still interested in buying a set of replacement domes and am curious about its response.
                                          Dave's Speaker Pages

                                          Comment

                                          • JonMarsh
                                            Mad Max Moderator
                                            • Aug 2000
                                            • 15261

                                            Funny you should mention that, re Hales, I've got the data and will upload later today or this evening.

                                            Yeah, I wouldn't want anyone to jump to any major conclusions about any driver based on this testing, the idea was more to identify possible issues and trends. In that regards I think it's successful, relative to the amount of time I had to put into it.

                                            It's very interesting how different the upper range breakup is for different tweeters; I just wonder how much that contributes sonically? Chris here is rather sensitive, it seems, to the H1212, and looking it and its little sibling, I see a specific behavior- is it what's repsonsible for what Chris hears?

                                            The Dayton RS28a, OTOH, has a very well managed breakup, and this seems to correlate well with what people report subjectively regarding it's sonics (reports my own experience verifies).

                                            OTOH, the well damped behavior of the Accuton's is intriguing, and whatever other issues I may have had with older systems I've done with the C23-6, hard dome sound definitly wasn't one of them. I'm also starting to look at some of their midrange/midbass units again. When one considers the amount of work that goes into the cabinets, though the driver is expensive, if I pay myself $20 an hour, it's a piffle.

                                            ~Jon
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                                            Comment

                                            • JonMarsh
                                              Mad Max Moderator
                                              • Aug 2000
                                              • 15261

                                              Originally posted by ergo
                                              Hi Jon,



                                              I have had the speakers "singing" for about a week. These are T29CF001, W18NX and SS8565 for low end. I like how this tweeter sound very much. I also have (only for few days more) a pair of W17E002 and Millenniums and comparing the tweeters - I would say that this far the T29CF001 performs at least as well as Millennium.

                                              Ergo
                                              This doesn't surprise me- even the H1189 holds up well. It's a real bargain as tweeters go, but takes a little more voicing effort at the system level. I do wonder if there isn't something strange about my Millenium Excels (at least the one I measured- is stuffing in the rear cavity missing, for example?). I think that bears further investigation.
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                                              Comment

                                              • JonMarsh
                                                Mad Max Moderator
                                                • Aug 2000
                                                • 15261

                                                Originally posted by capslock
                                                Thanks, Jon, that's really impressive!


                                                Accuton:
                                                - I didn't know the C23-6 already had a cleaned up motor design
                                                - does it use ferro?

                                                The C23-6 does use Ferrofluid. The new C24-6 uses it, but supposedly a lot less. The C24-6 is somewhat intriguing, because of the new underhung motor. Efficiency is higher, about 3 dB, but the published distortion sweeps look quite good- both at 2.82V/1 watt and at 5 watts. It seems to have a higher Q breakup mode at 30 kHz, but compared with most metal domes it looks well controlled. OTOH, the FR response curve indicates that one probably wouldn't use it below 1600 Hz or a little higher- though the measured distortion is low down to 1 kHz. I'd be curious what the off axis response looks like with these relatively large inverted domes. I imagine this tweeter might work rather well in a three way with a C88 or C89 midbass. Would be a fairly easy crossover to pull off. But which woofer(s)?
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                                                Comment

                                                • TacoD
                                                  Super Senior Member
                                                  • Feb 2004
                                                  • 1078

                                                  Wow great measurements! Very good resolution with your kit. Why are your measurements centered around 0 dB? I use the stock mic + praxis and I get absolute readings from praxis. Can you tell a bit more about how you measure the distortion (settings in Praxis).

                                                  Comment

                                                  • JonMarsh
                                                    Mad Max Moderator
                                                    • Aug 2000
                                                    • 15261

                                                    There's something funny with the Mic input on my Praxis setup- it's normally meant to handle the Giardin capsules, even with a cal file, it has VERY low sensitivity, and the only way with my ACCO mic or my alternative mic setups (B&K with HP Preamp, or Behringer ECM8000 with M-Audio Preamp) is through the Probe 1 input, as documented in LspCAD manual as an alternative. There's probably some way for me to calibrate the absolute level offset, but haven't figured that out yet.

                                                    In Praxis, one of the options for Acquisition mode from a Chirp stimulus is Swept FR + HD; basically I setup the standard SPL+Phase measurement, including first doing an acquisition to normalized impulse response and setting up the window, then do the Acuisition to SPL & Phase (I didn't display phase in these plots, though it's saved in the data file, of course). I ran the SPL and swept FR+HD at the same levels, with a passive preamp controlling the level to a Sony 5 channel HT power amp, and using a scope to verify levels at the tweeter for ~ 1 watt, as necessary to get ~90 dB, based on rated sensitivity.

                                                    For some drivers I plan to do stepped sine measurements with HD, I believe that's possible. In this case, I just wanted to get through a buch of drivers with enough info to make some basic selections or culling.
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                                                    Comment

                                                    • ergo
                                                      Senior Member
                                                      • Mar 2005
                                                      • 675

                                                      Jon, do you use a protection cap of some sort in front of tweeter when doing these measurements?

                                                      Ergo

                                                      Comment

                                                      • JonMarsh
                                                        Mad Max Moderator
                                                        • Aug 2000
                                                        • 15261

                                                        No. I'm either brave or foolish. Actually, just careful. With a log sweep there's not much time at the LF side. And I'm careful with all my interconnects that that I don't get something unplugged during testing (which could generate a tweeter destroying transient), and a use a Marchand Passie Preamp (Shallco stepped attenuator, highly repeatable) as the volume control between the AudPod output and power amp input.

                                                        For testing a ribbbon, I would use a series pass cap; you can put the probe 2 source sensing right on the driver, and Praxis compensates for the roll off, I believe.

                                                        For higher power distortion testing, I would only use multi-tone or fixed step in a range safe for the dome tweeter.

                                                        While many tweeters have short term power handling rated rather "agressively", realistically these devices are only meant to handle up to about 10 watts. And I would call even that somewhat short term.
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                                                        Comment

                                                        • Jed
                                                          Ultra Senior Member
                                                          • Apr 2005
                                                          • 3617

                                                          Originally posted by JonMarsh
                                                          I imagine this tweeter might work rather well in a three way with a C88 or C89 midbass. Would be a fairly easy crossover to pull off. But which woofer(s)?
                                                          How about the RS 10"? That would be nice. Maybe even a pair of RSs to get the sensitivity up.

                                                          Comment

                                                          • JonMarsh
                                                            Mad Max Moderator
                                                            • Aug 2000
                                                            • 15261

                                                            But which RS10? I'd lean more towards the 265HF, given it's bass output and low non-linear distortion. I've got some RS270's, too, but haven't done any testing on those- not much on the 265HF, either. More things to do, along with more detailed testing of C23-6, C13-6, and pondering acquiring a pair of C24-6, pending how the off axis stuff on C23 looks.
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                                                            Comment

                                                            • Jed
                                                              Ultra Senior Member
                                                              • Apr 2005
                                                              • 3617

                                                              Originally posted by JonMarsh
                                                              But which RS10? I'd lean more towards the 265HF, given it's bass output and low non-linear distortion. I've got some RS270's, too, but haven't done any testing on those- not much on the 265HF, either. More things to do, along with more detailed testing of C23-6, C13-6, and pondering acquiring a pair of C24-6, pending how the off axis stuff on C23 looks.

                                                              I'm beginning to wonder just how much the off axis response really matters. I've heard some very good tweeters that would not even be considered by some because of their poor off axis response. Although, I must admit the OW1s in my current 3-way speaker are nice. Looking to try something different however.

                                                              Jon, If you want to test some more accutons I can mail my C12s and C44s to you to add to the "bunch" for testing. Not sure if they fit any criteria, however. But hey, you never know and I don't have time to build anything for awhile because of my work schedule right now.

                                                              Jed

                                                              Comment

                                                              • cobbpa
                                                                Senior Member
                                                                • Apr 2005
                                                                • 456

                                                                Originally posted by Jed
                                                                I'm beginning to wonder just how much the off axis response really matters. I've heard some very good tweeters that would not even be considered by some because of their poor off axis response.
                                                                Jed
                                                                I'm curious, as I haven't heard many different tweeters, how far off axis did you listen to these? As in, it doesn't matter...because they still sound good in a given window, or because they are actually clearly audible off-axis, even if response is supposedly poor?

                                                                Comment

                                                                • Jed
                                                                  Ultra Senior Member
                                                                  • Apr 2005
                                                                  • 3617

                                                                  Some tweeters that I have listened to that don't have the best off axis response are eton ER4, and Great Heil. Both sound pretty good off axis (say 30 degrees) depending on what type of music you like.

                                                                  Comment

                                                                  • Mark K
                                                                    Senior Member
                                                                    • Feb 2002
                                                                    • 388

                                                                    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...
                                                                    www.audioheuristics.org

                                                                    Comment

                                                                    • jdybnis
                                                                      Senior Member
                                                                      • Dec 2004
                                                                      • 399

                                                                      Jon,

                                                                      A couple of nits, and picks,

                                                                      The harmonics falling above 20k are irrelevant. No?

                                                                      When you measure harmonic distortion can you EQ the input signal so the transducer is flat across the band of interest. Presumably a rising top end or a drooping low end would be compensated for by the crossover.

                                                                      Can you measure/display the signal below -70dB. The information there would be useful. Assuming distortion will increase with drive level. It is interesting to characterize it at 90dB, even before it is audible.
                                                                      -Josh

                                                                      Comment

                                                                      • JonMarsh
                                                                        Mad Max Moderator
                                                                        • Aug 2000
                                                                        • 15261

                                                                        Originally posted by jdybnis
                                                                        Jon,

                                                                        A couple of nits, and picks,

                                                                        The harmonics falling above 20k are irrelevant. No?

                                                                        When you measure harmonic distortion can you EQ the input signal so the transducer is flat across the band of interest. Presumably a rising top end or a drooping low end would be compensated for by the crossover.

                                                                        Can you measure/display the signal below -70dB. The information there would be useful. Assuming distortion will increase with drive level. It is interesting to characterize it at 90dB, even before it is audible.
                                                                        Reasonable comments. Keep in mind I consider this a "survey" test, to identify "components of interest", and "areas of excellence" as well as problematic issues; not a definitive side by side evaluation. And I chose a scale setup that seemed practical and useful for the majority of drivers.

                                                                        The Harmonics above 20 kHz are not measurable because they're outside the bandwidth of the system (~48 kHz, including microphone. I can extend the electronics to ~96 kHz (24/192 M-Audio Card under XP, SP2), but the mic is only calibrated to ~ 45 kHz, response rolls off above that.

                                                                        Re dynamic range, with headroom for the driver peaks, we're looking at about 80 dB range here as displayed. Survey test, remember? For detailed testing, I think I can alter the vertical scale to display another 10 or 20 dB. Seriously, the drivers that are in the -60 dB range are few and far between. And this is getting near the practical noise floor of the system and room, even with this measurement method.

                                                                        It would be better if the drivers were performing at flat acoustical output for all frequencies, but the that would be something of a nightmare to setup, as these drivers aren't necessarily flat... OTOH, anything outside of a +/- 2.5 dB window I wouldn't be interested in, and they are getting flat power inputs. Realistically, I wouldn't use a tweeter below the point it's rolling off in the bottom end.
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                                                                        Comment

                                                                        • JonMarsh
                                                                          Mad Max Moderator
                                                                          • Aug 2000
                                                                          • 15261

                                                                          Mark and Jed,

                                                                          I plan to do some detailed off axis plots on the C13-6 and C23-6. I'm also planning to configure a waveguide for the C13-6 and see if that helps with lower end distortion. I'm also going to modify a waveguide for larger diameter tweeters, and try that with some of the units like the RS28a and the C23-6.

                                                                          If the C23 looks tolerable off axis, I do plan to get a pair of C24-6 to evaluate; the published distortion spectra from Accuton is very low, even at 5 watts drive; consider that this part has the new underhung neodymium magnet system (like the C13-6 and the C90/T5 which I'm still waiting for), and is about 92-93 dB/watt sensitive.



                                                                          I'd really hoped that the H1283 would be an interesting part to try with waveguide, but it's chaotic upper breakup mode doesn't inspire me to play with it- too much like the H1212.

                                                                          I have a new in box NOS set of C88 Accuton's coming on the way this week (precursor to the C89) to test soon; I'm going to be looking at a few different midranges in the coming weeks. Jed, if you're curious, I'd be happy to test your C44's. Mark has the pair of C44's which used to be mine, that I traded for some Hales Tweeters I wanted to play with. I didn't have good test gear then, so couldn't evaluate them in depth. Maybe Mark has data he can share, or I can test yours or someones. Right now I'm not planning on buying C44s, as I'm looking for mids to work in the 300 Hz to 2 kHz area.

                                                                          ~Jon
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                                                                          Comment

                                                                          • JonMarsh
                                                                            Mad Max Moderator
                                                                            • Aug 2000
                                                                            • 15261

                                                                            Hales Transcendence Tweeter

                                                                            This is a part custom built for Hales by Vifa, as shown in other photographs, with a Faraday sheild on the pole piece.

                                                                            Click image for larger version

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                                                                            Because of the unusual front panel, it requires some care with diffraction control with front thick felt, or with rear mounting, though I haven't tried that, as the permissible depth on the panel wouldn't be that great.

                                                                            This tweeter also benefits from stuffing the pole piece to tame the response in the 3 kHz area; this is an unmodified unit, though.

                                                                            SPL Plot.
                                                                            Click image for larger version

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                                                                            Fairly high Q tweeter resonance at about 26 kHz, though not as "frightening" as the H1212 Seas. Other than the "presence" bump, the response is fairly smooth- even with no diffuser or phase shield (my preferred way to go).


                                                                            FR plus HD2 is shown here:
                                                                            Click image for larger version

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                                                                            Not quite state of the art, but still fairly usable above 2 kHz. Not that far off from a typical RS28a.


                                                                            Last, FR + HD3...
                                                                            Click image for larger version

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ID:	936228
                                                                            Very solid performance, nothing to complain about here.

                                                                            Probably could be used down to 1500 Hz if you don't mind some 2nd Harmonic in your Wheaties. A 2 kHz or higher crossover would be better; that's how it was used originally, after all. Would like to see less in the upper end spike; it's not too different from the MB 1" tweeter, and much higher Q than the RS28a.
                                                                            Last edited by theSven; 06 May 2023, 20:53 Saturday. Reason: Update image location
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                                                                            • jdybnis
                                                                              Senior Member
                                                                              • Dec 2004
                                                                              • 399

                                                                              Originally posted by JonMarsh
                                                                              Re dynamic range...Seriously, the drivers that are in the -60 dB range are few and far between...
                                                                              True, but do you care about the ones that aren't? :T

                                                                              Originally posted by JonMarsh
                                                                              It would be better if the drivers were performing at flat acoustical output for all frequencies, but the that would be something of a nightmare to setup, as these drivers aren't necessarily flat... OTOH, anything outside of a +/- 2.5 dB window I wouldn't be interested in, and they are getting flat power inputs. Realistically, I wouldn't use a tweeter below the point it's rolling off in the bottom end.
                                                                              A few of the tweeters (SEAS and Accuton) start to roll off around 3k-4k and are about 6db down by 1k. OTOH the two Usher models are pretty much flat down to 1k before they roll off. In fact the Dayton's general trend is to be more efficient at lower frequencies. Depending on how the manufactures calculated the spec'd efficiency on their tweeters, the C23-6 playing 1khz at 90db in a complete loudspeaker could be getting 6db more juice (measured after the crossover) than in this test, and the RS28a could be getting 4dB less to play at the same volume. A 10db difference is nothing to sneeze at.

                                                                              Originally posted by JonMarsh
                                                                              The Harmonics above 20 kHz...
                                                                              Sorry for being so cryptic here. What I meant to ask about was the HF harmonics displayed on the graphs, e.g., 2nd above 10k and 3rd above 7k. Are they relevant to performance in a system?
                                                                              -Josh

                                                                              Comment

                                                                              • JonMarsh
                                                                                Mad Max Moderator
                                                                                • Aug 2000
                                                                                • 15261

                                                                                Originally posted by jdybnis

                                                                                Sorry for being so cryptic here. What I meant to ask about was the HF harmonics displayed on the graphs, e.g., 2nd above 10k and 3rd above 7k. Are they relevant to performance in a system?
                                                                                Well, possibly not, but then, maybe... generation of high order harmonic products usually correlates with higher orders of IM distortion. Of course, upper resonances tend to obscure what we normally think of as "distortion", but then linear distortion is distortion, too.

                                                                                Now, the real question here might be, what is the best way to test? The answer, in my opinion, is there is no one "best way" to test, becasue sometimes a quick test like this is very useful to highlight trends and suggest areas of further investigation, while more detailed testing, like multi-tone IM or spectral contamination testing, will really be the "acid" test and correlate best with what we hear. Somewhere you have to strike a balance, and my general intent is to do "survey" testing that identifies trends and weak players, then follow up with more detailed testing on the drivers I'm really most interested in for new projects.

                                                                                Unfortunately, there probably will be no "one" perfect driver. Like MarkK, I'd like to find a fairly superlative 3/4" tweeter, but so far it's hard to find one with distortion performance even at moderate levels that compares with the better 1" and larger models. So, is it worth sacrificing off axis performance? To what degree? A lot depends on the rest of the system configuration, and the crossover points you think you'll have to live with. One option I'm going to explore is combining 3/4" and 1" tweeters with waveguides for the 2kHz and up area. If I had the ability to custom build waveguides, I'd probably explore lower frequencies, too. Maybe next year.

                                                                                For many of the good budget midwoofers, a crossover point higher than 1600 or 1800 just isn't desirable, because of cone behaviors above that point which are evident in ETC tests as well as nearfield testing.

                                                                                I'm looking for drivers right now that are OK for maybe 2000 Hz to 2200 Hz crossover points, but I suspect it's going to lead me into some pricey territory. I'm also looking for the tweeters with the minimal upper resonance breakup Q, because so far those have sounded best to my ears with the widest range of equipment. That means either soft domes, not my first preference, or just a handful of relatively well behaved hard domes.

                                                                                I'm not trying to pitch this stuff as any kind of absolute recommendation or guide for anyone, it's just how I'm seeing things right now, and what paths I'm choosing to explore, based on my limited resources- especially, limited time.

                                                                                ~Jon
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                                                                                Just ask Mr. Ohm....

                                                                                Comment

                                                                                • TacoD
                                                                                  Super Senior Member
                                                                                  • Feb 2004
                                                                                  • 1078

                                                                                  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.
                                                                                  I think the question if there are high end drivers that are worth the money depends on the person who you're asking it.

                                                                                  Also if all budget tweeters where as good as some more expensive one's there was no market for those :-).

                                                                                  Comment

                                                                                  • Jonasz
                                                                                    Senior Member
                                                                                    • Nov 2004
                                                                                    • 852

                                                                                    Jon: Maybe a stupid question but if you take the RS28A as an example it seems to have single high q peak at 30k. If you eliminate that peak with a notch (like with metal midbass drivers) would that make any difference distorsionwise lower down in the frequencies that we actually can hear?

                                                                                    Jonas

                                                                                    Comment

                                                                                    • Dennis H
                                                                                      Ultra Senior Member
                                                                                      • Aug 2002
                                                                                      • 3791

                                                                                      One option I'm going to explore is combining 3/4" and 1" tweeters with waveguides for the 2kHz and up area.
                                                                                      I think it might be interesting to make a felt "throat" for a waveguide with a 1" or even 1.5" tweeter. With a 3/4" hole in the felt, you should get pretty good off-axis response up high and it shouldn't attenuate the LF too much. Of course, the response wouldn't be flat anymore so you'd have to do some contouring in the XO.

                                                                                      Comment

                                                                                      • JonMarsh
                                                                                        Mad Max Moderator
                                                                                        • Aug 2000
                                                                                        • 15261

                                                                                        Originally posted by Jonasz
                                                                                        Jon: Maybe a stupid question but if you take the RS28A as an example it seems to have single high q peak at 30k. If you eliminate that peak with a notch (like with metal midbass drivers) would that make any difference distorsionwise lower down in the frequencies that we actually can hear?

                                                                                        Jonas

                                                                                        Unfortunately, to the best of my knowledge, no. No more than it does for the metal cone drivers- the cone resonances amplify harmonic components also. That's why you don't want to get too close to them. less than 1/3 could be a good recommendation.

                                                                                        Now, I'm going to experiment with bandpass tweeter crossovers; Avalon uses them, and I susepct they do it for a reason, EVEN though the Accuton tweeters are generally VERY well behaved up top.

                                                                                        Notice that as metal dome drivers go, the RS28a is much better behaved than most. Look at what those Seas drivers in the basic series do. I wonder what the new Magnesium Excel looks like up top? I think I took a photo of the data sheet at CES; I'll have to go look for that.

                                                                                        Click image for larger version

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                                                                                        Last edited by theSven; 06 May 2023, 20:54 Saturday. Reason: Update image location
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                                                                                        • cjd
                                                                                          Ultra Senior Member
                                                                                          • Dec 2004
                                                                                          • 5568

                                                                                          If only we could convince PE to produce the RS28A with a nice small Neo magnet assembly, we could slice-n-dice to match it up to something at ~7-10kHz or something.

                                                                                          C
                                                                                          diVine Sound - my DIY speaker designs at diVine Audio

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                                                                                          • JonMarsh
                                                                                            Mad Max Moderator
                                                                                            • Aug 2000
                                                                                            • 15261

                                                                                            Yeah, I'd like a nice small RS28a for center channel speakers, and MTM's, too!

                                                                                            I checked the Excel Magnum T29 spec graph, and it looks like a 10 dB peak at 27 kHz. Not bad, not great. Cleaner than the H1212, if the specs are to be believed.
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                                                                                            Resistance is not futile, it is Volts divided by Amperes...
                                                                                            Just ask Mr. Ohm....

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