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Thread: RFC News

  1. #31
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Recent Loudspeaker refurb work for a client:

    Impulse Lali loudspeakers using a simple first order crossover. Problems:

    One of the main drivers breaks into distortion with slight amounts of energy. Slight boominess in the bass and something not quite right with the imaging.

    original crossovers:



    Very basic, badly soldered and a bit of shoutiness at the crossover point.

    New crossovers designed and built using a series crossover design. This has several main advantages, including the cap damping out of band movement of the bass driver and the inductor doing the same to the tweeter. It also means that this is a subtractive crossover, so the signal applied to tweeter and bass must add up exactly to hat applied to the amplifier. Gains expected should include purer mid range perfromance, better damping at and close to the crossover point.

    Bespoke crossovers constructed and here shown on a test board. The crossovers were to be taken externally rather than mounted at the rear of the speaker just behind the main driver as per the original!



    Being tested in the system:



    Boxes constructed from 1/4 inch pine and ply (in this case) and given several coats of Danish Oil. here they are awaiting finishing and fitting of crossovers and terminals:



    New up-rated OFC wiring soldered to main drivers:



    New cabling taken from loudspeakers. Rubber gromits seal the cables as they exit the old terminal plates which have had the terminals removed and holes enlarged to take new cables:



    Some repairs to one of the drivers was also carried out before careful re-assembly for testing.

    Here, the refurbished Impulse Lali Floorstanders are being put through their paces prior to completion and assembly of crossovers into crossover boxes. Whilst not an insubstantial loudspeaker in their own right, here they are utterly dwarfed by the giant Reference Fidelios!



    Sound-wise, the newly refreshed Imuplse Lalis are nothing short of sensational.

    The midrange now sounds (and measures using a calibrated SPL meter and test tones) much flatter and smoother across the mid range. Bass has astonishing depth for the size of the cabs but real texture too. Mid range is now to die for and the distortion issue with one of the drivers has been cured.

    This is one very good example of just what can be achieved refurbishing old speakers. I heard loudspeakers at Whittlebury this year which would have been put to shame by these.

  2. #32
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Completed external crossovers for Impulse Lali loudspeakers with up-rated speaker wiring:






  3. #33
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

    Posts: 6,766
    I'm Dave.

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    Paul, any news on your new 'small' floor-standers yet ?

  4. #34
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Hi Dave

    Shhhhh!

    Yes, I'm working on a design at the minute but can't give away too much except to expect big sounds from slim a WAF friendly design for a very reasonable price (or range of prices depending upon finish). I'm part way through design, have selected the drivers and am aiming for release early next year. Frequency response will be as close to full range as I can get it from very slim enclosures.

  5. #35
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    I'll be expanding services offered soon to include TT set-up. It relies on the customer coming to me, and either leaving the deck with me for a day or two or waiting whilst set up is done. It includes tonearm and cartridge health-check and set up. Guide price varies depending on deck but 25 to 40 to check, set up properly and test TTs is about the ball park. I'll be up-dating my website in the next week or so with these and other services but rather than go back through the thread, I now offer:

    • bespoke quality cable making services
    • HiFi furniture - design and construction, including TT plinths
    • suppliy of high quality two-part contact cleaning solution
    • Loudspeaker design and construction
    • Loudspeaker repair and refurbishment
    • external crossover design and construction
    • replacement or upgrading of exisitng crossovers
    • TT health-check and set up
    • Supply of acrylic products including TT covers made to measure
    • Audio consultancy and set up services


    Just PM me if you have any queries

  6. #36
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

    Posts: 6,766
    I'm Dave.

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    Do you ever sleep..

  7. #37
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Not much Dave

    I'll be posting pictures of my latest loudspeaker refurb shortly to show just what can be achieved for a relatively modest outlay...in this case the rescue of a rare pair of Roksan Darius speakers which had been destroyed when an amp literally blew up and fed them with loads of DC current which welded the voice coils together into a molten blob (one of the tweeters blew as well). The owner was keen to have these brought up to "better than new" in performance terms....what ensued was an epic project which set him back less than a modest pair of stand mounters cost these days and the results were great!

  8. #38
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    For The rest of October ONLY!


    10% off ALL RFC products!

    That's not all...for every discounted order placed for the Venus, Mercury, Saturn or Jupiter cables, receive a FREE bottle of Planet Protector contact cleaner!

    For every RFC-MC1 Step Up Transformer ordered at 10% off RRP, receive a FREE bottle of Planet Protector!
    Last edited by Reffc; 15-10-2013 at 11:40.

  9. #39
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Example of a recent speaker refurbishment:

    Before: main drivers were fried (voice coils were welded together)...here, I've carefully removed one driver which had been glued in with silicone...2 1/2 hours carefully persuading it out without damaging the cabinet! I've already replaced the tweeter unit and wiring:



    Close up of one of the voice coils...insulation totally broken down and blackened:




    Interior cross brace had insufficient wadding to prevent reflections at the critical mid range straight back through the speaker cone causing phase distortion:




    This brace was wrapped in 35mm lambswool.


    Detail of delicate solder joint to replacement tweeters (just fitted in this photo):




    Existing external crossovers: A bit of a mess!:


    Before:





    These had been messed with over the years and some of the values were wrong. I tracked down the designer of the originals who was rather surprised to get a call from someone about his first ever speaker and crossover design of 30 years ago! Lengthy conversations followed during which various permutations were discussed, measurements recollected and final values settled upon in line with some later improvements to this crossover. I chose the components. The multiple caps are there because there are two advantages in wiring caps in multiples for passive crossovers: Firstly, they behave more as an "ideal" capacitor load and secondly, there's more chance of tolerances being met in place of using one large value cap (as in this case it would have to be).

    Two of the inductors were the wrong value. I replaced these (bass and one of the treble circuit damping inductors) with low resistance air cored inductors. Caps and inductors were all within 3% on tolerance. Wiring and routing was neatened up in the process and I ensured that soldred joints were all to a high standard:




    After:



    Note that the original poor quality plastic bodied steel input terminals have all been replaced with quality WBT items.


    Completed refurbishment project being tested for the first time....covers will be added to the external crossovers. They were simply ommitted until I had a chance to put them through their paces:




    Sound-wise, these sound wonderful, and the owner is very happy with his newly rejuvinated loudspeakers which should go on to give at least another 30 to 40 years of service
    Last edited by Reffc; 15-10-2013 at 17:23.

  10. #40
    Join Date: Nov 2011

    Location: Melbourne, Australia

    Posts: 2,062
    I'm Martin.

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    Good job, I bet they sound a lot better.

    That tweeter looks like it suspended on springs?!
    Speakers: Usher mini dancer II DMD
    Preamp: MFA Baby reference mk ii TVC
    Amp: Sanders Magtech
    DAC: Longdog VDT1 transformer coupled DAC
    Source: Self built PC (SOtM pcie usb output card with upgraded ultra low jitter clock card, Paul Pang RAM, pure SSD, passive cooling & Paul Hynes Audio SR7EHD psu providing power on separate rails to each SSD, the CPU and SOtM card)
    Power: Isotek Aquarius Evo3 (Schuko)
    Cables: Speaker cables - TQ Ultra Black, Interconnects - SLIC Innovations Eclipse C x2, Curious USB cable x3
    Ancilleries: USB regen, Acoustic Revive rgc24 under dac, Acoustic Revive QR - 8 (inside DAC) Stillpoints under amp, Shunyata darkfield v2 elevators under cables, Franc Audio isolation platforms under speakers, RDC combi-bases and spikes under oak platforms on everything, Hi fi Tuning Supreme throughout, Akiko Audio Tuning Sticks on speaker cables and inside DAC
    Software: JRiver MC21, Dirac room correction

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