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Thread: New Yorks; Tannoy DC 3836's in Rectangular York cab.

  1. #21
    Join Date: Nov 2011

    Location: wirral

    Posts: 103
    I'm frank.

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    Quote Originally Posted by Pharos View Post
    The chassis look very much a departure from usual Tannoy designs, and quite modern in that they are very cut down, which is done to reduce mid reflection from the frame.

    The magnet also appears to be smaller than, from memory, the usual size they would use, although of course many were covered with a pot.

    My instinct is that the drivers are a serious attempt at a solution to something.
    The drivers are standard DC 3836, the same as used in the long discontinued CPA range, the cone colour is different to the DC 3833 as used in the DMT 15/215 studio monitors, other than that they are essentially the same driver.
    Heres one of my 3833 drivers;

  2. #22
    Join Date: Apr 2012

    Location: Southall, West London

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    I'm Geoff.

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    Quote Originally Posted by Pharos View Post
    The chassis look very much a departure from usual Tannoy designs, and quite modern in that they are very cut down, which is done to reduce mid reflection from the frame.

    The magnet also appears to be smaller than, from memory, the usual size they would use, although of course many were covered with a pot.

    My instinct is that the drivers are a serious attempt at a solution to something.
    They are part of the Tulip Waveguide dual magnet series of drivers and very different to the original double ended single magnet units with compression driver.
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  3. #23
    Join Date: Dec 2015

    Location: vancouver

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    I'm danilo.

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    Ohhh Yes! They are decidedly different.
    Happily they retain some, arguably 'most' of the typ earlier design Tannoy DC sounds.
    Some serious Cost cutting inherent there though.

  4. #24
    Join Date: Nov 2011

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    Quote Originally Posted by danilo View Post
    Ohhh Yes! They are decidedly different.
    Happily they retain some, arguably 'most' of the typ earlier design Tannoy DC sounds.
    Some serious Cost cutting inherent there though.
    Well, lighter may well be cheaper(the AlNiCo mag is horrendously expensive) but also better-the precision cast open basket can now be found on all of Tannoy's totl DC's, these 3836 drivers benefit from vented cooling of the voice-coils, copper flux stabilisation rings on LF and HF pole pieces, the Tulip waveguide is a better lower distortion/lower colouration 'horn'.
    But the pepperpot has virtues all its own so I have no preference.

    See the light open frames...3818 from TW Glenair


    and a 12" Alnico pepperpot jobby.


  5. #25
    Join Date: Dec 2015

    Location: vancouver

    Posts: 642
    I'm danilo.

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    Hey! you have them 'In Hand' that's worth quite a bit IMO..
    Personally I wouldn't buy them, for use, only for resale.. for filthy Lucre.. to those afflicted with Tannoy Lust.
    Ferrite mags Lose flux... ~10 years and It's definitely measurable. Ask any Motor designer. Easily remagged though.
    Great Plains Audio has a Very popular Remag service....For Reason.

    Know any owners that Bother, hell.. are even aware??

    Tulip guide is simply a production cost bodge. Drilling pepperpot holes is far more complex/costly. Tannoy certainly F'up ..many.. of the HPD ones during / in the Harmon Debacle
    Regardless, Tulips decidedly sound lesser. But then everybody has an opinion
    Also suspect the die cast frame is again a cheaper solution.

    Audio is rife with Brochure Babbles. Trick is to let those, like water, run off one's back

  6. #26
    Join Date: Nov 2011

    Location: wirral

    Posts: 103
    I'm frank.

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    Quote Originally Posted by danilo View Post
    Hey! you have them 'In Hand' that's worth quite a bit IMO..
    Personally I wouldn't buy them, for use, only for resale.. for filthy Lucre.. to those afflicted with Tannoy Lust.
    Ferrite mags Lose flux... ~10 years and It's definitely measurable. Ask any Motor designer. Easily remagged though.
    Great Plains Audio has a Very popular Remag service....For Reason.

    Know any owners that Bother, hell.. are even aware??

    Tulip guide is simply a production cost bodge. Drilling pepperpot holes is far more complex/costly. Tannoy certainly F'up ..many.. of the HPD ones during / in the Harmon Debacle
    Regardless, Tulips decidedly sound lesser. But then everybody has an opinion
    Also suspect the die cast frame is again a cheaper solution.

    Audio is rife with Brochure Babbles. Trick is to let those, like water, run off one's back
    Lets disagree about bodge-just isnt true. On the subject of magnet materials; ferrite doesn't lose charge over time-it can lose some charge under high temperature but this returns to normal once cooled down.

    The From JBL;

    The Great Alnico / Ferrite Debate
    The subject of Alnico vs ferrite magnet drivers comes up fairly regularly on our site. The following is my attempt to clarify some of the issues involved. Before I get into a discussion on the merits and disadvantages of each magnet type, it is important to separate fact from fiction. To understand how this debate began, it is necessary to know a bit about loudspeaker history. Up until the late 70’s, most high end speaker manufactures used Alnico magnets due to their greater energy/weight ratio. Starting in 1978, all major manufactures (JBL, EV, Altec, Tannoy etc.) switched to ferrite drivers. That was when the myths began.

    Myth #1 – Speaker manufactures switched to ferrite as a way to lower their production costs and cheapen the quality of their drivers.

    Fact – The switch to ferrite was in response to a crisis situation whereby Alnico became totally unavailable. A civil war in Zaire led to the complete embargo of the world’s only source of commercial cobalt used in Alnico. There was no choice but to switch. This is why, in less than one year, every major Alnico speaker manufacturer had switched to ferrite.

    Myth #2 – Due to the lower energy/weight ratio of ferrite, drivers using this material have lower total flux and lower flux densities compared to the previous Alnico drivers.

    Fact – The initial ferrite conversion had the exact same magnetic energy of Alnico drivers they replaced. For JBL, the initial conversion effort focused on bass drivers since that represented their largest consumption of magnets. They had sufficient magnet stock on hand to continue Alnico compression drivers for a number of months.

    To be able to continue production of the speaker systems in their catalogs, the ferrite bass drivers had to be the exact sonic equivalents of the Alnico drivers they replaced. Otherwise, the entire systems would have to be re-engineered and there was no time to do this. To give you an example, the L300 Summit, both before and after the ferrite bass driver conversion, used the exact same Alnico tweeter, Alnico compression driver, enclosure and network. The only change was that the 136A driver had its Alnico motor replaced with a ferrite motor to become the 136H. The basket, cone and suspension remained identical. The only way this could work was if the ferrite motor had the exact same magnetic energy as the Alnico motor.

    As the demand for high power drivers increased, the magnetic energy of the ferrite drivers began to exceed the former Alnico systems. As an example, the last ferrite version of the Altec 515 had a flux density of 15kgauss compared to the 14kgauss of the Alnico version. The Alnico embargo proved short lived. Alnico became available in limited quantities after a year or so, but at a much higher cost. This happened before the compression drivers were converted and it was decided to continue their production to save the costs of redesign. Therefore, Alnico HF drivers remained in production for another three or four years, until it became too cost prohibitive to continue. Around 1983, they were converted to ferrite motors as well.

    Nonetheless, the costs of the ferrite replacements in constant dollars remained about the same as the Alnico drivers before the civil war broke out in Zaire. Any savings in cheaper magnetic materials were outweighed by the sheer size of the magnets and the need for a large pole piece to accommodate the external magnet topology.

    Now to factual differences. There are three main advantages of Alnico over ferrite:

    1) greater immunity to flux modulation

    2) greater heat stability.

    3) greater suitability to shielded applications

    There is also one significant disadvantage – Alnico is susceptible to demagnetization due to large voice coil currents.

    None of these differences are absolute. It is possible to design out all of the limitations of each material. However the issue becomes one of cost.

    Ferrite designs can equal or exceed an Alnico magnet’s flux stability with the addition of a copper shorting ring around the pole piece. With the use of vented cooling and heat sinking, you can manage the heat build-up on a ferrite driver to where it stays below the threshold of non-linear response. Finally with the addition of secondary magnets, you can shield the motor of a ferrite driver to the same degree as an internal ferrite equivalent.

    In the same manner, Alnico drivers can be engineered to be immune to demagnetization from overpowering. JBL has done this though the use of a series of flux stabilization rings in their new 1500AL driver. However it is extremely expensive.

    All in all, the major speaker manufacturers have found it more cost effective to engineer out the limitations of ferrite drivers than to do so with Alnico drivers and hence the dominance of ferrite designs.

    In conclusion, I believe the modern ferrite drivers are superior to the vintage Alnico designs. This is not because ferrite is inherently superior to Alnico. Instead, manufacturers have been able to engineer out any limitations of ferrite and apply the advantages of 25 years of technological progress in driver designs unrelated to magnets. For example, cone materials, suspension design and construction has progressed significantly since the last Alnico drivers were made.

    And from the man himself;

    Greg Timbers post about Alnico Re-Mag;
    Here's the Scoop
    Ferrite magnets do not demagnitize with time or drive. They are affected by temperature but that is reversible. They will return to normal when they return to room temperature. Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available. JBL has done a ton of things within the magnetic circuit to make the material behave in a more stable manner. At 100 degrees F, a Ferrite motor will be down about 1.5 dB in level which means the midband of the woofer will be lower by that much and there will be increased output around the system resonance. The TS parameters will be completely different - as though the BL was reduced by about 18%.

    Alnico magnets, by their nature are easy to demagnitize with drive. They will not change with time and their dependence on temperature is really small - maybe 1% at 100 deg.F. Alnico stability and resistance to back EMF is really good. This is why they make the best sounding magnetic structures. Unfortunatelly, given a big enough pulse of magnetic energy, they will demagnitize by up to 3 dB. The sensitivity to demagging is dependent on the specifics of the magnetic circuit and the length of the coil providing the field. Underhung woofers (LE15 and such) midranges, tweeters and compression drivers do not have sufficient back EMF fields to push the operating point of the structure below the knee. They are essentially stable regardless of input signal. The short-gap, long-coil speakers are the ones that have a problem. A 2231 can take a hit of up to 3 dB if a big enough hit of current takes place. 1.5 dB to 2 dB is more common. The effect does not get better or worse with time, it solely depends on how much current is driven through the coil. The more current, the more field. Once the field is bigger than a certain number, some amount of demagnitizing occurs. It is perminent (until externally recharged) and will only increase if a larger sustained current hit occurs.

    Therefore, if you have a qualifying alnico woofer and you have played it loudly you have some damagging. You can have the unit recharged and it will be fine until you play it again. Exceed the critical level and it will start happening. If you never do, it won't ever demag. Most of these designs trace back to the 50's and 60's where 15 - 30 watt tube amps were the rule. They didn't have the current capability to hurt anything. With the advent of big solid state amps, the current levels went up and the problems started to surface.

    Most of the qualifying 4" motors will loose 1 - 1.5 dB unless they are pummeled. Some of the older 3" with really short magnets, like the 2213A and 123A will typically be around 3 dB down. They go really easily. The old Decade woofers (116A and 127A) only had to see an amplifier in the room and they got really nervous. FYI, the new 1500Al used in the S9800 can take continued pulses of 5000 watts and loose no more than 1%. The test can only be done a few times before the coil is destroyed, but the magnetic assembly is totally stable.

    Frank

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