bobovox

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About bobovox

Personal Info

  • Location
    SE London, Europe
  • Real Name
    Robert

Wigwam Info

  • Turn Table
    Rega RP3
  • Tone Arm & Cartridge
    Rega Elys2
  • SUT / Phono Stage
    Rega Fono Mini
  • Digital Source 1
    Arcam CD73T
  • Digital Source 2
    Pioneer N-50
  • Integrated Amp
    Arcam A90
  • My Speakers
    B&W684 + DIY

Recent Profile Visitors

284 profile views
  1. Focal Utopia speaker clone with active crossover

    Great work, Dean, I'm seriously impressed.
  2. DIY compact, active floorstanders

    Hi Colin, yes I remember your thread - was hoping to get to Scalford this year particularly to hear yours and the other DIY speakers on show but had to cancel at the last minute. I have finalised the speaker terminal plate design in Front Panel designer and will send that off to Schaeffer for manufacture. I think I will use a protection cap - I went a bit spendy with the tweeters so don't want to take any risks. I'll keep the thread updated with progress but things might be a bit slow as life is getting in the way a bit at the moment - I'm getting married in November and too many other things going on as well.
  3. DIY compact, active floorstanders

    I found this while I was researching active crossovers - I haven't tried it so can't comment on how well it works: http://www.instructables.com/id/Raspberry-Pi-Music-Server-With-Built-in-Crossover-/ I may give it a go at some point.
  4. DIY compact, active floorstanders

    Hi Luke. My integrated amp can also act as a preamp for an multi-channel system; in multi-channel mode after the preamp stage the two "front" channels get routed through the stereo power amp section and the other channels require separate power amplifiers, I'm using an Arcam power amp I bought on ebay quite inexpensively. It's basically similar to what you are doing I think, just with an extra power-amp box. At one point I thought about getting a used home-cinema amp with HDMI input (processing bypassed) and using a Raspberry Pi to act and source and to do the cross-over but that required a bit more "hacking" than the MiniDSP solution.
  5. DIY compact, active floorstanders

    Cheers Stephan. I had read a few stories of people hearing hiss with the MiniDSP units and started to get a bit worried. I could just use the power section of the integrated amp and use the MiniDSP but as the preamp but would have to leave the MiniDSP accessible and I wouldn't be saving any boxes. I think I should be OK with maximum levels - I will use Toslink input from my CD Player, Network Player or Tuner. The maximum output level of the MiniDSP is 2V (as per the sources) so I think I'm OK, although please tell me if I'm getting this wrong. I chose the drive units based on hearing some Gamut stand-mounts which use them (or modified versions) and subjective impression was very favorable. This might be a bit of a slow-burn project but I'm bound to have more questions later and some drawings & pictures when I have them.
  6. DIY compact, active floorstanders

    I’m planning to build a pair of DIY two-way compact floorstanding ‘speakers. Drive units are from the Scanspeak Revelator range; R2904/7000-05 ring-radiator tweeter and a 18W/8531 mid-woofer. Inspired by a few recent threads here, I’m proposing an active cross-over, using a MiniDSP 2x4 HD unit. My only reservation about active cross-overs is getting the gain-structure right. I propose to use the MiniDSP between the digital source and the preamplifier. Am I correct in understanding that this will result in a higher signal to noise ratio than placing the cross-over after the signal is attenuated in the pre-amp? I have a multi-channel pre-amp module for my Arcam A90 stereo integrated amp and will use the power section in the integrated amp to drive the woofers and an Arcam Alpha 8P power amp to drive the tweeters. I have most of the bits I need and will start building the enclosures soon. Before I can do this I need to work-out how much space I might need for passive components as I was planning to mount these on the reverse of the input terminal plate. I understand that I should place a protection capacitor in series with the tweeters to block any DC. Does this need to be a high value, to minimise the effect on the tweeter pass-band? Crossover frequency will probably be in the region 1600-1800Hz so the capacitor could end-up rather bulky. Would it be OK to use an electrolytic capacitor for this? To allow for the difference in sensitivity between the tweeter and the woofer (including baffle-step loss) I will need to attenuate the tweeter signal. If I do the attenuation in the Mini-DSP, do I reduce the signal to noise ratio? I can apply some of the attenuation to the tweeter channels in the multi-channel pre-amp (up to 6dB, IIRC) and / or could use resistors in an L-Pad if this would have less effect on the SNR. Or am I worrying unnecessarily?
  7. Out of interest, Serge, how important is slew rate in evaluating the performance of an amplifier? There is little energy in music or a film sound track in the upper ranges of human hearing and nothing above the cut off frequency of a digital source therefore producing a 25kHz test tone (taking your example above) at full power appears a rather onerous test, if I have understood you correctly.
  8. Converting WAV files to FLAC

    Ah 24/96. The best way to reduce file size is not encoding dynamic range and frequencies you can't hear.
  9. Converting WAV files to FLAC

    Hopefully, these numbers weren't invented: https://en.wikipedia.org/wiki/FLAC#Compression_levels Approximately 3% increase in processing for decoding of FLAC 8 vs FLAC 5. Insignificant, certainly not a margin that would need a step change in hardware capability, albeit the reduction in file size is even less significant; where I will agree is that there are diminishing returns in terms of file size with increasing compression beyond level 5. The experiments I did suggest that the reduction in file size going from 5 to 8 was a bit bigger than this example though. FLAC was designed to be easy to decode. A Raspberry Pi Zero will quite happily decode FLAC 8 files, so I am surprised to hear that the Transporter had problems.
  10. Converting WAV files to FLAC

    If the file has been encoded correctly, no more processing power is required to decode FLAC 8 than FLAC 5 (or lower) as the instructions for decoding are written into the file at the time of encoding. https://xiph.org/flac/faq.html#general__asymmetry
  11. DIY Speaker Bake Off

    Suits me fine.
  12. DIY Speaker Bake Off

    I would love to come also, if the date suits. I have some DIY active floorstanders in the works. Albeit they've been "in the works" with various bits and pieces in place for about 18 months and were originally going to be passive standmounts. One way or another this could give my 'project' some (badly needed) focus. A "masterclass" on acoustic measurement and interpretation of the results would be useful for me - would love to know what I've been doing wrong
  13. Ideally a P90 but would consider other DIVA or FMJ 2ch in black.
  14. Crossover Design

    Passive crossover design isn't that difficult; I needed to do a fair bit of reading but as a part of my motivation for building some DIY speakers was to learn a bit more about audio this was all part of the experience. You can knock-together a functioning impedance measurement rig with a few quids worth of bits. There is freely available software for frequency response and impedance measurements (eg REW) and free-form crossover simulation (XSim) so it needn't cost thousands.
  15. DIY Presentation by Linn at Scalford

    I'll be interested to see what Linn unveil. An integrated amplifier with digital crossover hardware and four / six channels of power amplification might persuade me to convert exinging passive speakers - the increased box count puts me off at present.