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bobovox

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About bobovox

Personal Info

  • Location
    SE London, Europe
  • Real Name
    Robert

Wigwam Info

  • Digital Source 1
    Arcam CD73T
  • Digital Source 2
    Pioneer N-50
  • Integrated Amp
    Arcam A90
  • My Speakers
    B&W684 + DIY
  • Trade Status
    I am not in the Hi-Fi trade

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  1. I cheated and got the panels cut to size and the CNC work done by the supplier (SL Hardwoods). Sanding the Valchromat seamed to produce less fine dust than would have been the case with standard MDF. Valchromat has some kind of lubricant internally supposed to make it easier to machine and cut.
  2. Happy to oblige, Tony: I had the openings for the drivers and ports CNC machined - these were very nearly done. My cabinet building skills are a bit basic so butt joints all ‘round. They look reasonably presentable, perhaps with a bit of “home made character” if you look closely.
  3. Cabinets now sanded and after two coats of clear danish oil the yellow Valchromat is now looking distinctly ocre. I have taken some impedance measurements on the mid-bass: Port tuning at approx 73Hz. This agrees very well with the prediction from the Scanspeak spreadsheet I used for the box design: The predicted anechoic frequency response from the same spreadsheet is below. I will make some near-field microphone measurements to confirm when I get the time.
  4. Crossover designed - methodology as above. The design is based on gated measurements at 1m from mid way between tweeter and mid-bass so not valid below 200Hz (that applies to the graphs above also). Crossover frequency approx 2400Hz: The upper mid-range sounds harsh with the Beocreate board, particularly with music with lots of energy in the 800Hz-1200Hz region (eg Walton's Belshazzar's Feast). Using the same filter design* with my Arcam amplifiers and MiniDSP 2x4HD there is no such problem. I will have to investigate this further. The Beocreate board also has a problem with the auto mute cutting-in during quiet passages - I have set the auto mute level to zero in the DSP but the problem persists. The clicks between tracks also detract from my enjoyment of the music. Obviously, a speaker with a 4 litre enclosure is never going to produce huge bass but what bass there is I think is reasonably articulate. We shall see what others think at Kegworth. *Bi-quad coefficients adjusted for the differing sample rates in the DSP units but parametrically the same.
  5. bobovox

    NAS me peeps!

    If you only want to use the NAS drive for serving audio files to your streamer then the Synology j-series is fine. I use one with Minimserver - freeware/donationware DLNA server software that sits on the NAS drive and allows you to browse your music collection to find the music you want to play. I think there is a free CA app for controlling your streamer - others may know more about this. Setting all of this up is just a matter of following the instructions - no special technical knowledge required.
  6. Rear view; Internal view. There are 2mm bitumen damping sheets below the acoustic damping.
  7. Hi @lostwin I look forward to meeting you at Kegworth and showing the speakers It’s back to Plan A though - I’m not confident I’m going to get the reborn Minstrels to sound good enough. A few pictures of progress: Cabinets need sanding and varnishing. Crossover yet to do.
  8. bobovox

    The Hi-Fi Pub (Cafe, Restaurant...)

    The thing with Spiritland in King's Cross is that no amount of telling the screenagers to shut up and crunch their granola and poached quince more quietly lets you hear the stereo properly. I haven't been to the one in the Festival Hall yet but I expect the space in one of my favourite spaces in the entire world could be put to better use.
  9. bobovox

    The Truth About Vinyl - Vinyl vs. Digital

    I'm genuinely curious how many people can reliably tell the difference between a Rasberry Pi Zero W with an IQAudio DAC c/w wallwart switch mode power supply (£35 all in) playing 16/44.1 lossless vs 24/192 played on the most high end streamer, if unsighted and all other things being equal. I can certainly tell the difference between any redbook equivalent digital source and any record deck as soon as the first pop or crackle appears from the vinyl.
  10. bobovox

    Aside from your own system...

    The first time I heard Quad electrostatics I was totally blown away and have been every time since. Regretfully, I don't have the space at home.
  11. bobovox

    The Truth About Vinyl - Vinyl vs. Digital

    QI fact: The track order on the vinyl pressing of Peter Gabriel's So album was dictated by this effect; as the linear speed reduces toward the end of an album track, the bass resolution is also reduced. "In Your Eyes" was placed at the beginning of side two on the original vinyl to ensure the deep bass could be reproduced. On the CD, it was placed at the end of side two, giving a rather more uplifting end to the album (for those of us that listen all the way through anyway ).
  12. bobovox

    The Truth About Vinyl - Vinyl vs. Digital

    Surface noise during the quiet passages on classical recording kills vinyl stone stone dead for me.
  13. I've added a back-up system to my room & my wife will be coming to.
  14. bobovox

    Help with Tannoy Drivers

    Andrew, do you have the T/S parameters for the drive units? I'm wondering as Tannoy used them in a ported enclosure if they are really suitable for a sealed cabinet. Hopefully you can find an off the shelf enclosure design but if not then you will need the T/S parameters to calculate the enclosure volume required for the drivers. If you don't have them, it is possible to measure them with REW + an impedance measurement jig (which you can put together with a few quid's worth of bits): https://www.roomeqwizard.com/help/help_en-GB/html/thielesmall.html https://www.avsforum.com/forum/155-diy-speakers-subs/1340740-lilmikea-s-diy-impedance-measurement-jig.html
  15. Looking again at the drawing of the speakers and stands above I couldn't help think there was room for a 'speaker with a larger enclosure, offering the potential of a bit more bass. I stumbled upon a pair of Royd Minstrel cabinets, sans crossover & mid-bass drive units for £20 on eBay so thought I might try something a little different. I don't know the history of them - maybe that the mid-basses were donated to a pair with damaged drivers - but I'm just speculating there. The reclining enclosures are screwed onto the base plates with threaded inserts into the bottom panel, so it's perfectly possible unscrew these to fit the 'speakers into a suitcase. The drive units I had proposed originally were not suitable - the tweeters would not fit the original routing (104mm dia face plate vs 94mm in the Royds) and I didn't fancy the woodworking; the mid-bass was not suitable for a 7litre enclosure, so I bought some 2nd hand Monacor SPH-145HQ mid-basses from eBay and some Vifa XT19TD-00-04 ring-radiators (basically the little brothers of the tweeters proposed originally). Making a few nuckle-wrap tests on the enclosures I started to think that I would probably want to rebuild them anyway in 18mm MDF or 12mm with some additional internal bracing - the existing 12mm walls were a bit ringy - especially the chipboard rear panel. Anyway, drive units screwed-in I took gated measurements with REW - I have used this program before for DIY passive 'speakers I have built but wasn't sure how easy it would be to import into the DSP on the Beocreate. When it came to cross-over design I preferred to use the ACD (Active crossover design) spreadsheets by Charlie Laub, used by many of the active crossover guys on DIYA: http://audio.claub.net/software/ACD/ACD.html Measurements on the mid-bass showed a -5.5dB step in the on-axis response between 1kHz and 1.5kHz. I was concerned that this was a measurement artefact but searching on the internet I notice others have measured them same - not shown in Monacor's data sheet though. In order to get the acoustic response of the two drive units to follow the desired LR4 crossover slopes I set the corner frequency of the tweeter crossover to 2kHz in the DSP and 2.5kHz for the mid-bass. Even at LR4, 2kHz for a tweeter with fs=760Hz I thought was pushing my luck a bit so decided to rebuild the cabinets with routing suitable for the ScanSpeak ring radiators (fs=450Hz) proposed originally. With the simple text-file based configuration of the DSP in the Beocreate board, low and high-pass filters can be specified interns of corner frequency and Q. Filters are 12dB/octave by default so LR4 is specified as two cascaded 2nd order filters with Q=0.707. However, the shelving filter needed for baffle-step compensation had to be specified in terms of biquad coefficients. Unfortunately, the Beocreate documentation is not great here - I had to do a bit of experimentation to ensure the coefficient values were specified in the correct order. Resulting frequency response: Not sure what's going on at 425Hz - maybe something with a cabinet resonance? I'll get the accelerometer out when I get chance. I haven't attempted to optimise port tuning as yet - impedance measurement jig has gone walkabout so might need to build another. Nice deep response null with one of the drive units set to reverse polarity: Subjectively, I have reservations - I think this might change when I've got the port tuning / enclosure stuffing sorted. We shall see.