2020 Jeff Bagby Revolution Mini (soft dome)

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  • tktran
    Senior Member
    • Jan 2005
    • 661

    2020 Jeff Bagby Revolution Mini (soft dome)

    Here is my iteration of the late Jeff Bagby's amazing SB Acoustics Revolution Mini speaker.

    For those uninitiated, the Revolution Mini was designed by Jeff Bagby in late 2018. It follows the familiar 1/4 cu. ft. mini monitor size. But don't let the size fool you. This does everything from acapella to classical to jazz to rock. I’ve been in this game over 20 years, and it’s just phenomenal.

    All the kit components can be purchased in one convenient package, who ships to North America, Oceania and elsewhere:



    I opted for the Soft Dome SB29SDAC variant, instead of the beryllium dome SB29SBAC, and the white MW13 for aesthetic reasons, and used blackheart sassafras, an evergreen tree native to south eastern Australia where I'm currently living.

    I never met Jeff, but corresponded with him from the days of Madisound BBS forums over 15 years. Always kind, generous, and shared his knowledge. RIP.

    Click image for larger version

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    My other speakers are Music and Design NaO II, and Jim Holtz Statement II, both over 100L.
    Like your own children, you don't have a best.
    But you want something small, around the size of the LS3/5A or Jeff Bagby's own Continuum speaker, this is something special.

    When I look at the measurements, sure, the first thing that sticks out is the top octave (10-20Khz) on-axis.
    If that bothers you then build the one with the beryllium dome- it's a drop in replacement and doesn't have that failing/feature.

    But the other thing that the visual measurements between 100Hz to 10Khz aren't telling me ~7ms gating, so it's good down to about 150Hz, but in- room there's bass to around 50Hz. For music, it's all there.

    But why is the imaging is so spectacular? Late night intimate listening has never been so good.
  • Evil Twin
    Super Senior Member
    • Nov 2004
    • 1532

    #2
    Good pictures of a well executed classic design... of course, the PR gives it "legs". And your choice of blackheart sassafrass was a very good one...

    Imaging and engagement are key "success factors" for any design or build, and it sounds like this one pleases you well...
    DFAL
    Dark Force Acoustic Labs

    A wholly owned subsidiary of Palpatine Heavy Industries

    Comment

    • HiroPro
      Junior Member
      • Nov 2011
      • 7

      #3
      Very nice build! Beautiful job on the cabinets.
      Why the dip between 1-2k?

      Comment

      • tktran
        Senior Member
        • Jan 2005
        • 661

        #4
        Originally posted by HiroPro
        Very nice build! Beautiful job on the cabinets.
        Why the dip between 1-2k?
        That’s a characteristic of the MW13P midwoofer.
        Jeff took that into account for his design.

        It’s visual but not audible and IMHO generally causes a lot of concern.

        Tools and Olive did decades of research, and I paraphrase, but essentially
        show that dips are generally not audible, whereas peaks or resonances are problematic and discernible.

        Comment

        • HiroPro
          Junior Member
          • Nov 2011
          • 7

          #5
          I can understand how a lack of amplitude at a given frequency isn't audible because it's a lack of sound at a given frequency but that's a -6dB hole centered at 1.8k that goes from 1.2-2.2k and I can't help but speculate it's audible. On axis the scoop seems to go from 100Hz to 10kHz with a huge bump/peak between 10kHz and 20kHz of +8dB. I guess these are just the characteristics of the drivers used and in-room response. I'm sure with correction via AVR DSP these can be flattened out and I'm sure the resulting sound is beautiful as Jeff voiced them.

          Comment

          • tktran
            Senior Member
            • Jan 2005
            • 661

            #6
            Thanks for your comments.

            First off a few thing about my measurements:

            My measurements were taken to satisfy myself that
            1) I do not have defective drivers
            2) I wired up my crossover correctly.
            That is all.

            I posted those 3 lines here, along with the cabinet photos as a proof of DIY Mission Possible; in anticipation of the "if you didn't take a picture it didn't really happen" commentary. :-)

            They were done with what I would call "good-enough equipment" for a hobby grade DIY builder.
            (Sonarworks XRef20 48V XLR microphone, Focusrite Scarlett 2i2 mk3 USB audio interface, Windows 10 laptop, REW Software, and VituixCAD's Measurements Preparation with REW help guide.

            They were done in the far field, (x2 significant dimension of the cabinet) and are ungated, so accuracy is lost below 150Hz or so. It is on axis with the tweeter (eyeballing) and off axis, again is by eye balling.
            There is 1/12 smoothing applied for visual clarity.
            They do not take into the bass response a) the driver b) the passive radiator, c) the room, which generally affects everything below the Schroeder frequency of ~200Hz.

            Please do not interpret too much into my measurements ;

            What constitutes USEFUL measurements for a bookshelf speaker, that may be correlated with listener preferences, would be something like the CTA-2034-A, or "Spinorama"

            In the Olive Experiments- for in 12 bookshelf sized speakers were studied; what matters is:
            Smoothness of sound power (30%)
            Bass performance: (25%) (LFX: -6 dB down point relative to listening window (LW) sensitivity in the range 300 Hz to 10 kHz; and LFQ: absolute average deviation (dB) in bass frequency response from LFX to 300 Hz.
            On axis smoothness in amplitude response based on a linear regression line through 100 Hz to 16 kHz. (26%)
            On-axis absolute average deviation relative to the mean sound level between 200 and 400 Hz, in 1/20-octave bands from 100 Hz to 16 kHz. (19%)

            None of my 3 wobbly lines are sufficient to provide this information.

            Finally, I'm reminded of Troels Gravesen, and his comments about people looking at his wiggly lines:
            "A few comments on MEASUREMENTS before you start interpreting the readings below.
            First of all, if we think measurements will tell us how a speaker sounds, we're wrong. The perception of sound is way too subjective to be reflected in any measurements we can perform. A loudspeaker system is meant to give us a satisfying idea of an acoustic event and for some people a pair of 5 USD ear-plugs are enough, others spend 200 kUSD on a truly full-range pair of speakers - and the latter may not be happier than the former.
            Measurements may give us an idea of tonal balance of a system, i.e. too much or too little energy in certain areas, although dispersion characteristics play a vital role here. A two-way 7+1 and a three-way 7+4+1 may display similar horizontal dispersion, yet sound very different. Measurements may tell us about bass extension if far-field measurements are merged with near-field measurements. In addition to this, ports may contribute to bass extension. Most of we diy'ers do not have access to an anechoic room for full-range measurements from 20-20000 Hz.
            What cannot be seen is what kind of bass performance we get in a given room. Bass performance is highly dependent on in-room placement of your speaker and the same speaker can be boomy in one place and lean in another. Actual SPL level at 1 meter distance and 2.8V input is useful for en estimate of system sensitivity and combined with the impedance profile may give an idea of how powerful an amplifier is needed to drive the speaker to adequate levels.
            What measurements do not tell is the very sound of the speaker unless displaying serious linear distortion. The level of transparency, the ability to resolve micro-details, the "speed" of the bass, etc., cannot be derived from these data. Distortion measurements rarely tell much unless seriously bad, and most modern drivers display low distortion within their specified operating range.
            Many people put way too much into these graphs and my comments here are only meant as warning against over-interpretation. There are more to good sound than what can be extracted from a few graphs. Every graph needs interpretation in terms of what it means sonically and how it impacts our choice of mating drivers, cabinet and crossover design.
            What measurements certainly do not tell is the sonic signature of the speaker, because speaker cones made from polypropylene, aluminum, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of adding spices to the stew. Nor do measurements tell what impact the quality of the crossover components add to the sound, from state of the art components to the cheapest of coils and caps, they all measure the same if values are correct, yet sound very different."


            In closing, this speaker does sound fantastic, EVEN with the cheaper soft-dome tweeter variation.
            I can hear now, why Jeff Bagby (RIP) was proud to put this it up against any other speaker of it's size
            (ie. 5-7L) eg. BBC LS3/5A, or his own Continuum...

            Comment

            • Bear
              Super Senior Member
              • Dec 2008
              • 1038

              #7
              That dip may be reinforced by baffle diffraction. I'm a little surprised to see square edges, but there's no doubt that Jeff knew what he was doing.
              Welcome to Rivendell, Mr. Anderson.

              Comment

              • HiroPro
                Junior Member
                • Nov 2011
                • 7

                #8
                Hi Tkran! To be clear I think your Bagby Revolution Mini is one of the best-looking mini monitor speakers I have ever seen. The sassafras just pops with the heartwood lines via whatever oil/stain you used and the white midwoofer compliments it tremendously. I also imagine these speakers have great sound to go with the good looks and perform well above their mini monitor brethren top to bottom.

                Thanks for sharing information regarding the reality a loudspeaker’s sonic signature is not quantifiable, or more precisely, qualitative via any analytic metric. I agree this is the case for any loudspeaker system and I do believe synergies exist between drivers, xover design and amplification, DAC and transport. It is funny you should quote Troels Gravesen because I had just read those very words five minutes before reading your post in researching BlieSMa tweeters on his site.

                I’m unfamiliar with the Olive Experiments and I’ll be sure to give them a read.

                I do understand and do not hold you to “Spinorama” levels of measurement as I’m sure your wobbly lines were done in your listening area simply to get a prelim test of in-room response as well as making sure drivers are ok and wired correctly and of course an initial listening session. I can imagine such levels of measure were done when Jeff Bagby (RIP) designed it! I’ve read Jeff Bagby’s feelings of this design and I believe he even like it more than his Spirit Winds and that’s saying something!
                Last edited by HiroPro; 14 September 2020, 18:31 Monday.

                Comment

                • RookieBuilder
                  Member
                  • Feb 2017
                  • 41

                  #9
                  Those look awesome, nice work!

                  Care to share some more listening impressions? Id be curious if you could highlight listening impressions (similarities and differences) compared to the Statement II's?

                  Comment

                  • tktran
                    Senior Member
                    • Jan 2005
                    • 661

                    #10
                    auditory memory is poor, and the ownership and use of my Statement II and Revolution Mini is separated in space (20x30’ and over 10’ ceilings vs 12x15’ and 8’ ceilings) and time (2 years)

                    so the comparison will be limited.

                    What I find most impressive is the imaging. And this speaker just sounds much bigger than it actually is (7L!)

                    Comment

                    • Jim Holtz
                      Ultra Senior Member
                      • Mar 2005
                      • 3223

                      #11
                      Very nice build! Jeff is missed in the audio community. Your cabinet work is exceptional!

                      Jim

                      Comment

                      • tktran
                        Senior Member
                        • Jan 2005
                        • 661

                        #12
                        Thanks Jim,

                        Here is the actual on-axis response, and distortion, measured at 0.5m, on the design axis (tweeter).
                        (the irregularities below 300Hz are due to room reflections)

                        It's a great small speaker. Same dimensions (12" x8" x 8") as an KEF LS50, but better IMHO.

                        Click image for larger version

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                        Last edited by theSven; 09 April 2023, 04:38 Sunday. Reason: Update image location

                        Comment

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