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RCA and Goodmans full range speakers in Open Baffle

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langleycello

Greetings,

I have been recently reading about various enterprises with open baffle arrays, and I have a couple of pairs of vintage speakers to experiment with, namely Goodmans Axiom 150s and the legendary RCA LC1C.

I just wonder if anyone has explored either of these speaker types in an OB arrangement and have any thoughts as to the success or otherwise of such an enterprise?

Thanks for any thoughts / perspectives.

Regards,

Stephen

Follow Ups:

RE: RCA and Goodmans full range speakers in Open Baffle - tom1356 09:41:42 07/29/07 (0)
I have recently started using 12" Tannoy Monitor Blacks in JE Labs baffles.
They are really surprisingly good. Give it a try and let us know how you make out with your experiments.
RE: RCA and Goodmans full range speakers in Open Baffle - freddyi 08:03:01 07/29/07 (0)
Hi Stephen - - I've never heard RCA nor Axiom but both should be beautiful on open baffle and you could experiment with asymemtric depth wings and hinges like room divider. (I have MJK's sheet for open baffle but not sure how canted wings are incorporated)
re:JE Labs - seems like good advice - maybe Briggs should get a bit of credit? :^) - ah I see theres good reference and linked pages
a bit of Briggs on baffles
Best,
Freddy

Edits: 07/29/07
RE: RCA and Goodmans full range speakers in Open Baffle - Ivan303 05:48:07 07/29/07 (2)
Pictured above is a Goodmans 201's in a JELabs OB with a 16 Ohm EV T-35B running through a 2UF series cap and an L pad for a bit of top-end.

They did me quite well for years until I manage to find a pair of EdgarHorn 80's.

If you go with an Open Baffle use the plans on the JE Labs web site EXACTLY as drawn, the ratio's and dimensions seem to have a lot to do with the sound.

Nobody here but us chickens.
_________________________
- JELabs open baffle pages (Open in New Window)
- RE: RCA and Goodmans full range speakers in Open Baffle - langleycello 12:45:32 07/29/07 (1)
  Thanks gentleman,
  
  Very encourageing.
  
  Yeh.. I have been inspired by Troels Gravesen's consideration of the subject.
  
  http://www.troelsgravesen.dk/GoodmansAxiom150mkII.htm
  
  My only concern is that the Axiom 150 has a Qts of 0.25, as opposed to it's brother the famous 201, which open baffle enthusiasts embrace readily with a QTs of 0.7 The 201 has a less powerful magnet (Feroba?) it seems..?
  
  Any thoughts? I suppose I can only try out and see... Another thought are a pair of the very early Goodmans 12 which have a smaller magnet (Alnico) and a strange rigid mechanical spider (not the concertina type). Have had a pair of these in the garage for ages, tucked away - full rangers from the 40s, I reckon.
  
  Cheers,
  
  Stephen
  - well.............................. - Norman Bates 01:49:04 07/30/07 (0)
    myself, to figure what the driver's f3 (without the open baffle baffle) I crunch the numbers for a qtc (sealed box) a squeek higher than the drivers qts. That'd give you -3db in infinite baffle (I think).
    
    Then I figure that the shortest distance arround (say 12" to baffle edge).
    Well, if you have 2' from front to back (2' wide baffle), meaning 180 degrees out of phase , so a dip at 1129 / 2' = 560.
    
    Now you are only 90 degrees out of phase an octave below that dip, so expect 3db to 6db of lift at 280hz. Then it rolls at 6db/octave (without driver's affects. I've been trolling for offset ratios as if you have the driver smack in the middle of the baffle you have a deeper dip than if it is offset. Best compromise so far I've found is the driver 1 : 1.618 from left to right, and the driver 1 : 1.31 to the top. Or if a 4' wide board, have the driver 18 1/3" from left making it 29 2/3" from the right, and have it centered 24" from the top. I'd love to have someone measure such a beast.
    
    And this is a free boost !!!!
    
    I've read not to worry of baffle step for open baffle either.
    
    Something else to remember, If you put an 18" driver on a 24" wide baffle, you have a shorter distance front to back due to the wider speaker, so you baffle is now not as wide as it was before.
    
    So a qts driver will start rolling really high.
    
    Others can argue.
    It's the way I figure.
    
    I enjoy the lack of chestiness from open baffles.
    
    Norman

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