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  • #46
    Re: listening impressions of some interesting drivers...

    Hey Brandon, what Silver Flute driver are you using for the 8" sub?
    thanks,
    nikkoluvr

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    • #47
      Re: listening impressions of some interesting drivers...

      The W20, probably the 8 ohm version, though I don't remember for sure. I went with passive radiators for a tiny box (12" cube). I'll be posting that info with the BoseBuster update within the month.
      ~Brandon

      Soma Sonus
      DriverVault

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      • #48
        Re: listening impressions of some interesting drivers...

        So after 5 months I have distilled my experiences in this thread down to some finished designs that I just finished constructing. First is super cheap and easy Silverflute W14 and SB26STCN MTM, using the 4 ohm drivers in series for an easy load:

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        For my buddies home theater, SB15MFC woofers and SB26STCN in MTM or TM:

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        For my own home theater I'll be using the ScanSpeak Disco 15cm and Scanspeak HDS in TM, here is the MTM:

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        I'll also be doing versions of the SB15MFC with Scanspeak HDS tweeter, no pics yet though.

        New reference 3-ways for my music room. Peerless Exclusive 8" woofer (I'll also be doing a version with the SB 8"), Transducer Labs tweeter, and a mid to be selected after auditioning: either the TangBand 3" dome or BG Neo8:

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        And pending a writeup my BoseBuster version 2 are done finally:

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        ~Brandon

        Soma Sonus
        DriverVault

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        • #49
          Re: listening impressions of some interesting drivers...

          Nice builds Brandon. The SB MFC and SB26SCTN are both drivers I've been interested in. The MFC version seems mow behaved at higher frequencies than the NRX according to SB's plots, but you say the NRX is better behaved. That's interesting.
          The BoseBuster looks neat.
          Nichikuros - Peerless 831735 Nomex + Vifa NE25VTA
          Digger8 - Small compact 8" sub with F3 = 20Hz
          Madison-D and Madison-R - Tang Band W4-1720 + Vifa BC25SC06 or Beston RT003C (TM and MTM)
          Jeffrey - Tang Band W5-704D + Beston RT003C
          Jasmine - Fountek FW146 + Fountek NeoCD3.0 Ribbon in Pioneer BS21 Cabinet

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          • #50
            Re: listening impressions of some interesting drivers...

            Originally posted by jsr View Post
            Nice builds Brandon. The SB MFC and SB26SCTN are both drivers I've been interested in. The MFC version seems mow behaved at higher frequencies than the NRX according to SB's plots, but you say the NRX is better behaved. That's interesting.
            The BoseBuster looks neat.
            I had to reread my comments because overall I think the poly is noticeably better behaved than the paper. The high frequency hash just doesn't show up like it does with the paper (caveat: when crossed at 2.8khz, crossing lower the difference may not be as noticeable). What I did notice though, was that on a couple songs where there was vocal high note, the paper stayed a little smoother. But I may have overstated that being the norm, overall the poly is better behaved just due to the breakup not being as noticeable (probably as non-linear distortion).
            ~Brandon

            Soma Sonus
            DriverVault

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            • #51
              Re: listening impressions of some interesting drivers...

              Had to take a couple weeks off from these projects to get the house ready to sell. Today I was able to finish off the construction of the last speakers, all ready for measurements this week. The ones below use the Peerless Exclusive 8", but I have an Aurum Cantus AC200/50C2C and SB Acoustics SB23NRX on the way so I can make versions with those for friends.

              ~Brandon

              Soma Sonus
              DriverVault

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              • #52
                Re: listening impressions of some interesting drivers...

                Was hoping to finish measurements on the 3-way (which I've dubbed Karnak's in homage to the incredible Egyptian temple) today, but looks like I'll need another day. I am extremely happy so far though. A LOT of baffle diffraction modeling, not just for the smoothest response, but a response that will work well with the drivers' response, and the intended crossover points. And a number of prototypes to verify the model. Not doing this well in the past has caused surprises after the speaker is built, and ultimately caused me to drop the project. Here are the results (6.5ms gate, no smoothing):

                TangBand 75-1558SE:


                BG Neo8:


                Transducer Lab N26C:
                ~Brandon

                Soma Sonus
                DriverVault

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                • #53
                  Re: listening impressions of some interesting drivers...

                  FINALLY got my BoseBuster sequel done and written up!! I've shortened the name to BBV2 so I don't get any hassle from Bose. Next I'll be finishing the Scan Disco TM and MTM, the other flavors after. My Soma Sonus site is now hosting my projects. Here is copy of that page:



                  BBV2

                  A small format sub/satellite system


                  The goal for this project was a small, high quality speaker that was shallow enough to be mounted on wall next to the thin LCD TV’s that are now common. The Fountek FR88EX was perfect for this project, with its low distortion and ability to fit in a truly tiny box (you can get the cones really dancing with little change in character). After several tweeters, I finally settled on the SB Acoustics SB26STCN-C000-4. This tweeter not only measures well, but is subjectively a very clear and open sounding tweeter. Crossover point is 2.8khz @ LR4. Here is the on-axis frequency response:


                  With reverse polarity to check phase integration:


                  The frequency response measurements consist of a far field measurement with a 6.5ms gate (no smoothing!!), merged to a near field measurement at 300hz, resulting in a quasi-anechoic response. The low frequency ripple is the noise floor of my shop.

                  Impedance:



                  Here is the crossover schematic:


                  Inductors are 18g on the woofer and 20g on the tweeter. The small resistance value shown with each inductor is the resistance of the inductor itself, not a separate resistor.

                  Baffle layout:


                  The following is how I initially integrated the sub and satellites. This is intended to be a quick way to get the system up and running. Obviously there is always a lot more one can do to get the smoothest bass and mid-bass response, and this is only one simple method.

                  First, I use two subs, one roughly at the foot of each main channel. In this case I tried REW as the measurement software since it’s free and easy to use. I use a mic from Cross Spectrum Labs. I didn’t bother with all the calibration of the measurement setup since we just want to see real-time in-room response for integration. Given that, it is pretty straightforward to setup: just open the RTA window, change the scale to go up to 2khz, 1/6 octave smoothing, select FFT Length 32768, Blackman-Harris 7 window, 8 averages, and that’s it. You might have to open the preferences and set the soundcard output if you get no sound, or the input if the mic doesn’t read anything. I aimed for a 175hz crossover, I’d like to experiment with 200-250hz in the future.

                  1) First set the levels of each channel (without subs on), I use a Radio Shack meter on A weighted Fast

                  2) in the AVR set the sub to “LFE+main” (this is on a Marantz, other brands should be similar)

                  3) set the sub crossover to 250hz

                  4) set the mains to small and crossover of 80hz

                  5) starting with just the left channel outputting pink noise (sub off), adjust the crossover until your -6dB point is at roughly 175hz:


                  My bass doesn’t appear to drop off quick, but that is due to the noise floor of my apartment being fairly high. Raising the signal will correct this, but I didn’t want to get my neighbors bent out shape!

                  6) Now running only the left sub, adjust its level to match the main. I like a little boost in my home theater bass though

                  7) Adjust the sub crossover until its -6dB is also 175hz:


                  8) Now turn on both the main and sub, and check integration:


                  9) Looks good so I moved on to the right channel

                  I was lucky and integration was very good right away. All I really have left is to fine tune the sub response. I’ll probably have to move it, requiring me to go through the integration again. Anyone who measures their setup knows how badly the front wall (often in combination with the floor and side wall) can really mess up the response in the 100-500hz area. One of the nice things about a sub/sat system crossed around 200hz is that you now have drivers with different crossover slopes, and in two different positions in the room, to smooth out the response. At this point I would switch to 1/12 or 1/24 octave smoothing to make sure I wasn’t smoothing over the ugly parts.

                  If one did not have good integration yet, you can adjust the phase on the sub, or adjust the delay setting in the AVR, or move the sub around, to get the proper phase match. Sometimes I find the response improvement to be ambiguous as I change settings. When that happens I like to run the main in reverse polarity, switch to 1/24 octave smoothing, and adjust delay/phase and sub placement to get the deepest null at the crossover. When you find it, you then switch the polarity back to normal and you should have excellent phase integration.
                  ~Brandon

                  Soma Sonus
                  DriverVault

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                  • #54
                    Re: listening impressions of some interesting drivers...

                    Nice! The write-up is excellent and the info and graphs are very thorough. I haven't seen many set-up/integration instructions, but yours are great. Love the effort and end-result.


                    John A.
                    "Children play with b-a-l-l-s and sticks, men race, and real men race motorcycles"-John Surtees
                    Emotiva UPA-2, USP-1, ERC-1 CD
                    Yamaha KX-390 HX-Pro
                    Pioneer TX-9500 II
                    Yamaha YP-211 w/Grado GF3E+
                    Statement Monitors
                    Vintage system: Yamaha CR-420, Technics SL-PG100, Pioneer CT-F8282, Akai X-1800, Morel(T)/Vifa(W) DIY 2-way in .5 ft3
                    Photos: http://custom.smugmug.com/Electronic...#4114714_cGTBx
                    Blogs: http://techtalk.parts-express.com/blog.php?u=2003

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                    • #55
                      Re: listening impressions of some interesting drivers...

                      Originally posted by johnastockman View Post
                      Nice! The write-up is excellent and the info and graphs are very thorough.
                      John A.
                      Thanks. I'm hoping to get some off axis plots up soon. I'm really impressed by these little Founteks, you would assume they would be best with non-stressing jazz or something, but they are really in their comfort zone with rock and roll. Amazing how much those little cones can move with little change in the character of the sound.
                      ~Brandon

                      Soma Sonus
                      DriverVault

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