60's EV SP15 with "mystery" control. (not a coax) There's only about 2 cubic foot volume. This made my AN10 in 70 liter reflex sound pathetic with Stanley Clarke giving an upright bass some workout.
The measurement was in-room with the cabinet in an 8x10 room with doorway to hall adjacent to the left of the cabinet.
FWIW I think its an idea worth pursuing and would try the JBL lens shape vs others.
Here's a pair of SP15 https://img.canuckaudiomart.com/upl...-ev_electrovoice_sp15_15_coaxial_speakers.jpg
The measurement was in-room with the cabinet in an 8x10 room with doorway to hall adjacent to the left of the cabinet.
FWIW I think its an idea worth pursuing and would try the JBL lens shape vs others.
Here's a pair of SP15 https://img.canuckaudiomart.com/upl...-ev_electrovoice_sp15_15_coaxial_speakers.jpg
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For the early 1950's, and even today, The RJ for a 15 inch (and 12) was only ~3.5 cubic feet (~98 liter) external bulk. I have a slim-line RJ 12 which is the same bulk and imagine a slimline RJ15 should work about like the regular/more cubical RJ15.
Below are pictures of the rare, early RJ with "diamond" shaped aperture
plus its dimensions from the BBC paper (showing the 12 inch speaker aperture)
And the same cabinet but famous "lemon" aperture
The little 8 inch driver RJ was an early example of a bookshelf speaker form-factor
My old 18 inch reflex cabinets were vented like the RJ. There were two pairs, this one at 6.2 cubic foot internal
volume was the smaller cabinet. A mic could be poked in the aperture and get the response neatly.
Below are pictures of the rare, early RJ with "diamond" shaped aperture
plus its dimensions from the BBC paper (showing the 12 inch speaker aperture)
And the same cabinet but famous "lemon" aperture
The little 8 inch driver RJ was an early example of a bookshelf speaker form-factor
My old 18 inch reflex cabinets were vented like the RJ. There were two pairs, this one at 6.2 cubic foot internal
volume was the smaller cabinet. A mic could be poked in the aperture and get the response neatly.
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with fullrange having hot/shouty/rising on axis response, I would experiment with JBL's lens for an RJ style
Scale this and print for a template
Scale this and print for a template
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I've not been at my house for some months but think its~0.75 inches - its shown as that in the BBC RJ paper which can be dowloaded:
The Robbins-Joseph (R-J) loudspeaker enclosure - BBC R&D
fwiw - here's the "Slim-Line" RI with 12" speaker and the spacing cleats can be seen
IRC R-J used 1/2" plywood for their cabinets
Here's how I tried to model in hornresp as a tapped horn:
The Robbins-Joseph (R-J) loudspeaker enclosure - BBC R&D
fwiw - here's the "Slim-Line" RI with 12" speaker and the spacing cleats can be seen
IRC R-J used 1/2" plywood for their cabinets
Here's how I tried to model in hornresp as a tapped horn:
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hi bob4 - - here's the1953 R-J article - still interesting
Audio Asylum Thread Printer
Here's that issue of AUDIO in case you want better quality views
Audio Magazine (January 1953)
Frank Robbins and William Joseph had a similar sized cabinet for a 1951 article but it was more like
a BP box
Audio Magazine (December 1951) : Free Download, Borrow, and Streaming : Internet Archive
Here's an interesting pdf with William Joseph and British Industries Group
https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/50s/Audio-1955-Apr.pdf
Robbins and Joseph's first speaker from the December 1951 issue of AUDIO
Audio Asylum Thread Printer
Here's that issue of AUDIO in case you want better quality views
Audio Magazine (January 1953)
Frank Robbins and William Joseph had a similar sized cabinet for a 1951 article but it was more like
a BP box
Audio Magazine (December 1951) : Free Download, Borrow, and Streaming : Internet Archive
Here's an interesting pdf with William Joseph and British Industries Group
https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/50s/Audio-1955-Apr.pdf
Robbins and Joseph's first speaker from the December 1951 issue of AUDIO
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Here's Frank Robbin's patent for the well known commercial version of the "R-J"
https://patentimages.storage.googleapis.com/ce/c2/58/a5cf53dfa6d925/US2694463.pdf
Interestingly, those patent images seem correct with regards to scaling as the inner baffle was spaced
two inches from the front baffle, giving a tuning of around 80Hz.
https://patentimages.storage.googleapis.com/ce/c2/58/a5cf53dfa6d925/US2694463.pdf
Interestingly, those patent images seem correct with regards to scaling as the inner baffle was spaced
two inches from the front baffle, giving a tuning of around 80Hz.
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