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Thread: Tall and narrow GRF style birch plywood cabinets

  1. #1
    Join Date: Mar 2009

    Location: The New Forest

    Posts: 1,855
    I'm Steve.

    Default Tall and narrow GRF style birch plywood cabinets

    The Cabinets I made for a pair of Tannoy HPD drivers could finally be collected after the lockdown easing.

    The drivers were dropped off to me and I installed them during the day for afternoon collection.

    The aftermarket crossovers are external hence dedicated boxes.
    Nice components in the crossovers.

    We also used high quality Janzen integral cable and gold plated Tannoy 4 pin plugs.

    These are built using the Scandinavian birch plywood throughout and designed to be taller and narrower than the original Tannoy GRFs.
    Modelled you have the same tuned backloaded horn path.
    These also feature the bass cleaning up Tear drop baffle in the throat of the horn section.

    Finished in English light oak.

    The customer (a Dolby surround sound engineer) had the drivers in original chipboard Tannoy Berkeley cabinets.
    Needless to say the cabinet material, construction and backloaded horn bass make these a very much improved Hi-fi experience.

















    Driver installation





    System: Turntable : SP10 MKII slate plinth, Custom Ebony tonearm board, Arm : Fidelity Research FR64s, Cartridge : SPU Royal N. SUT : Lundahl 1:13. Phonostage : Icon Audio, Streaming RPi/Kali reclocker -> I2S -> DSP XO / Pre / 4 DAC's : WAF Najda, 5 Poweramps : 3 x EL84 SET's, 2 x D class amps on bass channels, Speakers : 5 way front loaded horn system: 2 X Tapped sub 15" LF drivers / 2 X Exponential mid bass 15" drivers / Tractrix 200Hz mid horns with JBL2482's, / Tractrix 550Hz upper wooden horns with factory refurb'd Vitavox S2's / Raal Lazy Ribbons as high frequency tweeters. Wires: good silver or good copper where best suited. DIY RCM.

    Maker of tonearm boards, armpods, Tannoy GRF style speaker cabinets, horn speakers, counterweights and more.
    For more information about my creations and products please click below

    http://fosworld.wixsite.com/magna-audio & on Instagram https://www.instagram.com/magna_audio/

  2. #2
    Join Date: Sep 2019

    Location: North Lincolnshire

    Posts: 254
    I'm Lloyd.

    Default

    Forgive my lack of knowledge, if I was to buy from a pair of these narrow GRFs from you would I need to get the crossovers (Berkeley cabinets currently) altered to be tuned to the larger GRF cabinet ?
    A widower finding solace in music

  3. #3
    Join Date: Mar 2009

    Location: The New Forest

    Posts: 1,855
    I'm Steve.

    Default

    Quote Originally Posted by Swann36 View Post
    Forgive my lack of knowledge, if I was to buy from a pair of these narrow GRFs from you would I need to get the crossovers (Berkeley cabinets currently) altered to be tuned to the larger GRF cabinet ?
    Hi,
    The existing crossovers will work just fine.
    The crossover point remains the same. 1000Hz.

    The notch filter for the horn tweeter renains the same.

    The energy settings on your crossovers give you the flexibility to essentially attenuate the bass some extent. Turn up the treble energy you turn down the overall volume = less bass.

    I found my Berkeley drivers and crossovers worked very well in the GRF cabs.
    I always had them set in the mid positions.
    Average sized living room.

    There are aftermarket crossovers which may improve clarity (higher quality components).
    I've fitted quite a few.
    Most customers stick with the standard crossovers.
    I've also replaced the very old capacitors a few times.

    The GRF bass is deeper, and it's more tuneful horn bass. Instrument mid bass and deeper bass subtleties become apparent.

    Additions of the tear drop baffle to help block unwanted higher frequencies from the horn help too.

    I make the cabinets so tuning of the bass horn damping can be achieved by the addition of more inner felt lining the horn.
    Only found this to be necessary for small rooms.
    Otherwise it's done as per the GRF drawings.

    I use 21mm and 24mm premium birch plywood, the cabinets are of a superior faster/tighter sound.

    Hope that helps.
    Last edited by Magna Audio; 27-09-2022 at 08:56.
    System: Turntable : SP10 MKII slate plinth, Custom Ebony tonearm board, Arm : Fidelity Research FR64s, Cartridge : SPU Royal N. SUT : Lundahl 1:13. Phonostage : Icon Audio, Streaming RPi/Kali reclocker -> I2S -> DSP XO / Pre / 4 DAC's : WAF Najda, 5 Poweramps : 3 x EL84 SET's, 2 x D class amps on bass channels, Speakers : 5 way front loaded horn system: 2 X Tapped sub 15" LF drivers / 2 X Exponential mid bass 15" drivers / Tractrix 200Hz mid horns with JBL2482's, / Tractrix 550Hz upper wooden horns with factory refurb'd Vitavox S2's / Raal Lazy Ribbons as high frequency tweeters. Wires: good silver or good copper where best suited. DIY RCM.

    Maker of tonearm boards, armpods, Tannoy GRF style speaker cabinets, horn speakers, counterweights and more.
    For more information about my creations and products please click below

    http://fosworld.wixsite.com/magna-audio & on Instagram https://www.instagram.com/magna_audio/

  4. #4
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

    Default

    very nicely made steve.. very pretty too
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

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  5. #5
    Join Date: Sep 2019

    Location: North Lincolnshire

    Posts: 254
    I'm Lloyd.

    Default

    Quote Originally Posted by Magna Audio View Post
    Hi,
    The existing crossovers will work just fine.
    The crossover point remains the same. 1000Hz.

    The notch filter for the horn tweeter renains the same.

    The energy settings on your crossovers give you the flexibility to essentially attenuate the bass some extent. Turn up the treble energy you turn down the overall volume = less bass.

    I found my Berkeley drivers and crossovers worked very well in the GRF cabs.
    I always had them set in the mid positions.
    Average sized living room.

    There are aftermarket crossovers which may improve clarity (higher quality components).
    I've fitted quite a few.
    Most customers stick with the standard crossovers.
    I've also replaced the very old capacitors a few times.

    The GRF bass is deeper, and it's more tuneful horn bass. Instrument mid bass and deeper bass subtleties become apparent.

    Additions of the tear drop baffle to help block unwanted higher frequencies from the horn help too.

    I make the cabinets so tuning of the bass horn damping can be achieved by the addition of more inner felt lining the horn.
    Only found this to be necessary for small rooms.
    Otherwise it's done as per the GRF drawings.

    I use 21mm and 24mm premium birch plywood, the cabinets are of a superior faster/tighter sound.

    Hope that helps.

    It certainly does and thank you for taking the time to explain.

    I’m contemplating moving up from the Berkeley cabs as I’m moving house soon (fingers crossed this year) and once settled in and see how all the bills work out plus room layout I plan on getting my last set of speakers and I’m really captured by yours as far as I can see only positive comments and I of course have the drivers 15 inch HPDs from 1976 which I’ve had recommended on another thread they should go to Paul at RFC for their surrounds renewing/ general fettling up and if budget allows his external crossovers too so your cabs might well complete the picture on the speakers front , well that’s where my heads at so far , Paul’s (RFC) Canterburys are stunning but well out of my price range even without the current inflation crisis.

    Once again thanks for the reply I hope we can speak again before the year is out

    Oh nearly forgot my further aspiration is to hear then perhaps save up for a Copper Amp like I’ve seen mentioned elsewhere on here
    Last edited by Swann36; 27-09-2022 at 12:06. Reason: Added a further point
    A widower finding solace in music

  6. #6
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

    Default

    Very nice. I can almost feel the bass punch from here , I know what big BLH speakers can do!
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  7. #7
    Join Date: Mar 2009

    Location: The New Forest

    Posts: 1,855
    I'm Steve.

    Default

    Quote Originally Posted by Swann36 View Post
    It certainly does and thank you for taking the time to explain.

    I’m contemplating moving up from the Berkeley cabs as I’m moving house soon (fingers crossed this year) and once settled in and see how all the bills work out plus room layout I plan on getting my last set of speakers and I’m really captured by yours as far as I can see only positive comments and I of course have the drivers 15 inch HPDs from 1976 which I’ve had recommended on another thread they should go to Paul at RFC for their surrounds renewing/ general fettling up and if budget allows his external crossovers too so your cabs might well complete the picture on the speakers front , well that’s where my heads at so far , Paul’s (RFC) Canterburys are stunning but well out of my price range even without the current inflation crisis.

    Once again thanks for the reply I hope we can speak again before the year is out

    Oh nearly forgot my further aspiration is to hear then perhaps save up for a Copper Amp like I’ve seen mentioned elsewhere on here
    Uncertain times, but we'll get through them.

    Yes, it's Paul's X/Os I've fitted several times over the years.
    System: Turntable : SP10 MKII slate plinth, Custom Ebony tonearm board, Arm : Fidelity Research FR64s, Cartridge : SPU Royal N. SUT : Lundahl 1:13. Phonostage : Icon Audio, Streaming RPi/Kali reclocker -> I2S -> DSP XO / Pre / 4 DAC's : WAF Najda, 5 Poweramps : 3 x EL84 SET's, 2 x D class amps on bass channels, Speakers : 5 way front loaded horn system: 2 X Tapped sub 15" LF drivers / 2 X Exponential mid bass 15" drivers / Tractrix 200Hz mid horns with JBL2482's, / Tractrix 550Hz upper wooden horns with factory refurb'd Vitavox S2's / Raal Lazy Ribbons as high frequency tweeters. Wires: good silver or good copper where best suited. DIY RCM.

    Maker of tonearm boards, armpods, Tannoy GRF style speaker cabinets, horn speakers, counterweights and more.
    For more information about my creations and products please click below

    http://fosworld.wixsite.com/magna-audio & on Instagram https://www.instagram.com/magna_audio/

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