Parkandbike

Wammer
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Parkandbike last won the day on July 4 2014

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About Parkandbike

  • Rank
    Super Wammer
  • Birthday 17/09/1949

Personal Info

  • Location
    Cambridge
  • Real Name
    Don

Wigwam Info

  • Turn Table
    Given away
  • Tone Arm & Cartridge
    Ditto
  • Digital Source 1
    dCS Puccini
  • Digital Source 2
    SBT
  • Pre-Amp
    ARC Ref3 LE
  • Power Amp/s
    AN P4s
  • My Speakers
    AG Duos
  • Trade Status
    I am not in the Hi-Fi trade

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  1. I'm still working my way up to speed on digital photography, but I second the endorsement for the Google NIK plug-ins and would add that the "Define" noise reduction works very well indeed. These plug-ins are now free, but I've been told that they cost £400 before Google acquired them.
  2. Yes, I've tried that. I was attempting to use back wall cancellation [which I would have expected to reduce decay time (?)] and side wall cancellation [which would only work at the listening position and hence I would not expect it to impact decay time (?) ]. Of course I may not have got it right, but it did reduce the peak. However I still have extended decay time (difficult to quantify as my measurement package is not that easy to interpret). My thought on active cancellation was to try to supplement the back wall cancellation and also to give me a solution that was easier to tweak without continually adjusting the position or large awkward speakers.
  3. Thank for the replies and pms. I don't think I can have made I clear what I am trying to do. I can tame the troublesome peak by speaker placement (utilising wall reflections) or by dsp, but I still feel there is a bit of "bloat" in this range. The long decay associated with this frequency persists even after I have tamed the peak and I want to see I can correct the long decay time. If I can, I'd then assess whether this has any benefit. My experience with conventional bass traps etc suggests that it is going to be hard to get any useful effect without unacceptably large installations (it's not a dedicated listening room), so I was wondering about active cancellation using sub in anti-phase. I have the necessary kit to try it, but wondered whether anyone had tried this or had experience with other approaches (eg tuned traps) to shorten the decay time. To answer the specific point in the last two replies: The room measurements vary a bit depending on where you take them, but are as follows Length 7.43m (wall to wall) - 7.88m (large from window to rear patio doors (most of width of the room) Width 4.75-5.20m Height 2.27m I realise it could be a complicated mode involving two of the dimensions, or even all three, and I have tried some of the on-line apps for calculating these. However taking the longer measurement for length I calculate room modes at 22Hz (0.5 wavelength), 43 Hz (1.0 wavelength) and 65Hz (1.5 wavelength) which is pretty close to what I see. Yes, I realise both of those points; what surprised me was the apparent lack of any significant impact on the measured frequency response (ie I was not just looking at my problem frequency) Hmm have not made a list, but generally orchestral music. Ill try to be alert the next time I notice it to see if my hypothesis fits The bass units are not ported, but my "one-note bass" comment was sloppy short-hand. As indicated above I felt that this region was too prominent without frequency correction and I was still not entirely happy with it after frequency correction. It may be specific recordings as you suggest, but I have heard at least some of these on other systems where I was not aware of the effect (albeit with speakers with less bass extension).
  4. Whilst a poor speaker design could result in an uneven frequency response, there would have to be some sort of weird delay to show up as a room mode/extended decay time. However, I suppose it's possible (especially since I think the subs are servo controlled) and the thought has nagged me. However I would have thought that would be a pretty severe design fault and no one has commented on it. It could possibly be a fault condition, but I get the same measurements with either of the two speakers driving the room and the other channel muted. The speakers weigh 70kg each, so I'm not that keen to try wrestling them (and the power amps etc) outside where I would have thought other noises could disturb the reading. A better bet might be to try to wrestle one into a different room to see if the modes shift. In the current room there seems to be another strong mode at 20ish Hz, so that rather fits with my hypothesis i.e. that room length is half the wavelength of 20ish Hz and one and a half times the wavelength of 60ish Hz (the peak one would then expect at 40z is clear on one channel but not so much on the other). So my guess is that I am hearing a room effect and I would like to hear if anyone has tried active cancellation to deal with that before I start the heavy lifting, but thanks for the thought!
  5. Parkandbike

    decay time

    For some time now I have been troubled by a "one-note" issue in the base. It's not that bad as some don't seem to recognise it, but it does bother me at times. I've measured frequency response and identified a bass peak around 63Hz and also found a room mode at that frequency. (Playing a 63hz tone seems to be roughly where I'm hearing the problem). The plot of decay times clearly reveals that this frequency range has the longest decay time in the audible bass range. (I suspect this resonance is to do with the room length which is roughly 1.5 times the wavelength at this frequency- although it' not exact and might be a coincidence). I've tried: Using absorptive bass traps (6 GIK monster traps) in various positions and, while they make some improvements at higher frequencies, they do little to affect this peak either subjectively or objectively nor do they seem to have much effect on decay time at that frequency Using a Helmholtz resonator (thanks Gregg!) and while this was not specifically tuned to the problem frequency, it seemed to have little effect (again as judged by listening and measuring) Using DSP (Antimode 2.0). This does trim the peaks, but I still felt the ringing was there. I need to go back and check what it does to decay time, but I seem to recall that it did not make a clear difference. That seems sensible to me since while I can see why a long decay time would cause a peak in the frequency response, I would not have thought that reducing the peak with DSP would affect decay time. Placing the speakers to get destructive interference from wall reflections at this frequency. That was very effective as far a frequency response is concerned, but I still noticed the one-note effect and measurements still showed the long decay time. It may be that I'm obsessing over something that is not amenable to treatment, but I was wondering about trying to use a sub in anti-phase at the other end of the room (with suitable time delay). Has any one tried this and, if it worked, was it better to run it over a wide range or restrict it to the problematic frequency range? Does anyone know how audible a longer decay time is (once the peak has been reduced)? I realise the obvious answer is "suck it and see", but I thought I'd ask before starting to lug things around! Would be grateful for any thoughts and especially shared experience.
  6. Serge will provide the definitive reply, but I think if they are in series you should use 16ohm, or- if in parallel- 4ohm. Presumably the second pair will be in another room?
  7. I thought the ZH270 went well with my Quad ESL 63s and my old amp is now driving 2905s in its new home. I only moved on as it was too noisy for my AG Duos.
  8. Anthony, I'm really sorry, but I missed your post (have not been in the WAM much recently) and both the speakers cables and i/cs sold to a non-wammer friend. My apologies ! FWIW I have the same speaker cables, but cannot recall whether I used them with my Quads. best wishes Don
  9. I've just got my P4s back after 6+ months in Partridge Green. It was a tremendous leap of faith, the cost was enough to make me gulp and at times I wondered whether I was being stupid, but I have to say I am over the moon with the result. The mods included: Change output transformers to UHiB. Change the power supply capacitors to the new KAISEI electrolytics. Change the line input and main board and replace all the resistors with 1 watt non-magnetic Tantalum and all the signal caps with Audio Note copper signal caps. Replace pots with the stepped-attenuators. I'm using a pre with these amps, but this makes it easier to balance the channels if I want to increase or decrease sensitivity (and of course makes it much easier to use them as stand alone single-source integrated amps). Replace the valves I have no idea which of these changes is responsible for which of the improvements I'm hearing, but bass is much better, details are more intelligible and everything sound more "real" somehow. I'm very, very happy indeed!
  10. Richard

    A non-wamming friend of mine is very interested in these.  I can vouch for him and it is his Oracle-MA clock cables I have just posted as sold.  Obviously he cannot reach you by PM, but you can contact him at  terry.hanby@icloud.com if you wish. 

    He's based just outside Cambridge, so it should be easy to arrange a meet if appropriate.

    Best wishes

     

    Don

  11. Oracle-MAs definitely sold (on the Wam ) AVt I/Cs and AVt1 speaker cables still available
  12. 2 x 1 metre MIT ORACLE-MA Digital Cables with BNC terminations, sold subject to the usual. AVt interconnects and speaker cables still available.
  13. All sold now. Mods please archive. A friend is suffering a bout of "sidegradeitis" and wants to sell his MIT cables as follows: 2 x 1 metre MIT ORACLE-MA Digital Cables with BNC terminations - (new price was approx $3000 each - the replacement in the current MIT catalogue is the ORACLE MA-X at $5000 each). With original boxes. - (£600 each ono) 1 pair 1 metre MIT AVt interconnects with RCAs. Can't find boxes at the moment. - (£250 ono the pair). 1 pair 4.5 metre MIT AVt1 speaker cables with interchangeable banana/spade connectors. With original box. (£350 ono the pair). As far as I can see all are pristine, as I would expect given the care he takes with his equipment (non smoking, no pets or kids). I've been promised pics, but as I'm away for the next couple of days, thought I'd post now and add pics later. If you are interested let me know and I'll put you in touch. I can vouch for him and a few "senior" wammers know him.