An interesting Tannoy CPA 12" / GRF cabinet experiment

Discussion in 'Hi-Fi and General Audio' started by speedy.steve, Aug 28, 2010.

  1. speedy.steve

    speedy.steve

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    Today Dev (moderator here) came round with his Tannoy CPA12's - these are 12" paper coned DC's with tulip wave guide and rubber surrounds that were in a small 80L (I think they were), MDF boxes used as a studio monitor.

    We listened to my 15" HPD first and while while sorting out the 12" into my other pair of GRF's. I'd made some adapter rings so my 'spare' GRF cabs could take the 12" drivers and we loaded them in.
    Sounded pretty amazing in truth. A sound I could live with - the 15's are more subtle in some areas but the 12's are punchy and not exactly lacking in filling the full GRF cabs for sound either.
    Bass was pretty amazing - no sub needed here!
    Quite an interesting experiment... If a 15" driver can go in a 530L cab (Westminster) then a 12" can certainly go in and work in a full size Tannoy GRF we found today!

    I think it safe to say Dev was a bit blown away that cabs could make so much difference. After nearly 2hrs of all sorts of music (thanks to Rob for the Laptop streaming via my DPA enlightenment DAC lossless FLAC's that sounded pretty good), we then put the 12's back in the monitor cabs and tried them - they sounded not unpleasant but where had all the scale and bass presence gone, not to mention the mid and upper bass detail and timbre?!

    I am learning that cabs really are important.

    Some photo's.

    My 15" HPD's in cabs
    [​IMG]

    Dev's CPA 12's loaded in with adapter ring and extra felt to seal the mag in the rear baffle they went in pretty smoothly.

    [​IMG]

    [​IMG]

    Lucky I'd kept the 15" front baffle cutout when making them...


    The CPA's in there normal home, Pretty substantial, braced and weighty 80L MDF cabs... Great for monitoring guitars / vocals as they were intended I reckon, but struggle as full range hifi speaker.

    [​IMG]
    Very interesting experiment.

    So all you 12" owners, what are you waiting for Back loaded horns are the way to go!

    Perhaps a scaled down cab but having heard these I would say you want the full cab effect!

    Dev might be thinking of a similar sized cab with turned 90 deg with a narrower front baffle and similar volume folded horn arrangement...
     
    Last edited by a moderator: Dec 7, 2013
    speedy.steve, Aug 28, 2010
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  2. speedy.steve

    Dev Moderator

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    Many Thanks for your hospitality Steve. It was an interesting (and as I said yesterday a depressing:)) experiment. Yes, the GRF horns are much better home for the 12" CPAs. They were a completely different speaker. I'm now left wanting more, so Thanks a bunch!!! :D.
     
    Dev, Aug 29, 2010
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  3. speedy.steve

    nando nando

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    i still love my cheviot's modified by me , steve when you are in this neck of the woods please pop round and have a listening sesion, regards,
    nando.
     
    nando, Aug 29, 2010
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  4. speedy.steve

    RobHolt Moderator

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    it was a very interesting day and showed quite clearly that some of the smaller Tannoys really are hampered by the cabinet. Not that a !2" driver is exactly small :)
    The good news is that these older pro Tannoys in the plain black enclosures don't attract the sky high prices of the better known models, yet the drivers are similarly excellent.

    Nice TT you have there Steve, and the 12" Pioneer looks and works superbly.

    Thanks for a very illuminating day.
     
    RobHolt, Aug 29, 2010
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  5. speedy.steve

    sq225917 Exposer of Foo

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    Dev, told you they were a better driver than speaker, they need 80l behind them at least, even better with 120l
     
    sq225917, Aug 29, 2010
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  6. speedy.steve

    Dev Moderator

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    You did Simon, but I couldn't believe just how good they were in the GRF cabs.

    BTW, Rob listened to them a couple of weeks ago at my place, where we even played with isolation and had the source on 8 phases of isolation :D. Even with this they didn't sound as good as they did yesterday:D.

    [​IMG]



    [​IMG]
     
    Dev, Aug 29, 2010
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  7. speedy.steve

    speedy.steve

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    Is that insulation the same sort of paranoia as the Mana boys have? :)

    The future is the past - get a GRF!
     
    speedy.steve, Aug 29, 2010
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  8. speedy.steve

    Dev Moderator

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    :D

    So, any ideas for a suitable cabinet?
     
    Dev, Sep 1, 2010
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  9. speedy.steve

    nando nando

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    open buffle, oops,
     
    nando, Sep 1, 2010
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  10. speedy.steve

    RobHolt Moderator

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    Big aperiodic box - 100+ litres.

    You can lose some of the box width you don't want and extend the depth.
     
    RobHolt, Sep 1, 2010
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  11. speedy.steve

    Dev Moderator

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    I think this is probably the simplest option for me. I believe a simple rectangular 1m (h) x 0.35m (w) x 0.4m (d) should provide well over 100l. I can't be precise cos I have no idea how much space the drivers and bracing would steal. I would like cabinets tapered though just like my D700's, which again would rob them of volume.
     
    Dev, Sep 1, 2010
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  12. speedy.steve

    speedy.steve

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    I have to say back loaded horn as no boom box or ported affair will come close to the range of bass / scale available to GRF's - You might end up with a 12" pair of Berkeleys. Actually, sticking them into a pair of Berkeleys and trying them to see how they work might be an idea... They are 98L.
     
    speedy.steve, Sep 1, 2010
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  13. speedy.steve

    Dev Moderator

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    I tend to agree with you Steve, but I don't have room for them, or an understanding wife:(.

    There is also the small matter of my limited woodworking skills.
     
    Dev, Sep 1, 2010
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  14. speedy.steve

    Tenson Moderator

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    Get a copy of WinISD and put the drivers T/S data in. You can then play with box volume and porting arrangements. I'd suggest a large area rectangular port is the easiest to build and sounds best too. You can insert some light damping in the port if you want to make it aperiodic.
     
    Tenson, Sep 1, 2010
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  15. speedy.steve

    Joe Petrik Denebian Slime Devil

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    Steve,

    Some dude has scanned an original GRF rectangular brochure. Thought you might be interested in reading it —

    [​IMG]

    [​IMG]

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    -----------------------

    And a related scan —

    [​IMG]

    Joe

    P.S. Any idea if the 30–20,000 cps ± 3db spec is accurate?
     
    Joe Petrik, Sep 2, 2010
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  16. speedy.steve

    speedy.steve

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    Thanks Joe, Great material / document. Will read in much more detail after work.
    See Dev - show your wife the sales material. It says they are compact! Must be true!

    100l = 3.5cuft.
     
    Last edited by a moderator: Sep 2, 2010
    speedy.steve, Sep 2, 2010
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  17. speedy.steve

    Joe Petrik Denebian Slime Devil

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    Steve,

    It's odd that GRFs were considered a compact speaker, given that today the term is used to describe 7- to 9-litre enclosures.

    If people want wee speakers, fine, but ye cannae change the laws of physics.

    Legendary speakers are where it's at, man.

    Joe
     
    Joe Petrik, Sep 2, 2010
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  18. speedy.steve

    la toilette Downright stupid

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    All things are relative, and I think the rectangular GRF's are compact compared to the colossal corner GRF's!

    My Devon cabs are 'bookshelf' speakers according to Tannoy; they've got 12" driver FFS! How big did they expect one's bookshelf to be?!
     
    la toilette, Sep 2, 2010
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  19. speedy.steve

    bottleneck talks a load of rubbish

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    mneh - its all a matter of perspective. corner GRF's are compact when compared to a 5 way horn system. . .


    (but then so is a ford modeo)
     
    bottleneck, Sep 2, 2010
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  20. speedy.steve

    Joe Petrik Denebian Slime Devil

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    Chris,

    There's huge and then there's f-in' huge, but I take your point.

    Are you running a 5-way horn?

    Joe
     
    Joe Petrik, Sep 2, 2010
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