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Okay speakerbuilders here is a question.

Discussion in 'Amps and Cabs [BG]' started by jock, Apr 3, 2002.


  1. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    I bought an old cab with two Altec Lansig 418B (15")speakers.
    I really like it´s oldschool mids and highs. (I will use a sub of some kind for lows but thats an other story).

    I would like to make two separate 1x15" of my 215, preferably in a size like Bag Ends s15d.
    How important is the dimetions of the cab if its sealed? The cab is sealed now and I like that sound.
    Can I measure the existing cab and devide it´s volume with two to get the volume needed for one of the speakers? Is it the volume of the cab that is important or is it the depth, hight etc...?
     
  2. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Who sells unfinished (empty) speakercabs and parts in Europe? And in Sweden?

    Here is a link with info about the speakers:
    LINK
     
  3. You're right, just divide the internal volume of the cab by two, and build your two new cabs in any shape you think is cool.

    Regards,
    Joris.
     
  4. now that you mention it.. if you have a 4x10..
    does it make any difference in volume / tone if you isolate all the speakers from eachother ( both magneticly and room ) ?

    e.g. if you make 4 compartments with one speaker each.. put foil on the sides of the compartments..

    would it make a difference in soundquality ? and is the difference positive or negative ?
     
  5. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    I read somewhere that there was a golden rule in the relation between hight, depth an width to avoid standing waves inside the cab. Is this true?
     
  6. AdX,

    IMO it makes no difference. Besides a slightly larger cab to account for the internal panels.

    One particular advantage is, that when one driver blows, the other 3 won't be pushing around the loose cone of the blown one. This GREATLY improves the sound ;).


    Jock,

    Yes there is this golden rule, but I think it hardly applies to bass guitar cabinets. It's more a hi-fi freak thing. But you should really avoid a perfect cubular shape.

    Build the cab so it fits in your trunk / looks cool / makes a nice beer stand / it's comfortable to sit on (this may be a babe-magnet, you know)

    :D
     
  7. fleetwood

    fleetwood

    Aug 29, 2001
    Swansea UK
    Question

    If a 15" bass cab is closed, can it be smaller or does it have to be bigger than if it was ported? Also, if the cab was too SMALL what effect would you have as you increased volume?
     
  8. The optimum sealed volume is typically less than the optimum volume of a vented cabinet. The low frequency extension of the sealed cab is less than the vented. Power handling capability of the sealed cabinet is less than the vented cabinet.

    Bass transient performance of the sealed cabinet is much better than the ported cabinet, especially at and below the port tuning frequency.

    My spreadsheet shows the optimum values for a large number of drivers, both vented and sealed.

    Any cabinet that is too small has an increasing hump in the mid-bass 80 ~ 125 Hz range, and a corresponding falloff in low frequency extension. The Carvin cabs are good examples of cabinets that are too small for the drivers. They roll off very quickly below 60 hz.
     
  9. Ken Nahora

    Ken Nahora

    Jun 1, 2001
    The Egyptians knew about the Golden Ratio when they built the pyramids. They regarded it as one the essential laws of the universe. It's as valid today as it was in the time of the Pharaohs.
    It provides the most balanced and even distribution of resonances.
    In speaker cabinet design, it reduces problematic standing waves and other phase issues.

    The Golden Ratio
    .62 : 1 : 1.62

    So your box could be:
    62cm X 100cm X 162cm.
    That's probably too big, but you get the idea.

    If you have the woodworking skills, you might try a trapezoidal shape. A trapezoid is even better for reducing stading waves and such.

    A pair of trapezoidal 1x15s could provide some interesting possibilities. Side by side, you could improve the horizontal dispersion. Stacked, you could improve the vertical dispersion.
     
  10. Ken Nahora

    Ken Nahora

    Jun 1, 2001
    Also,
    Be careful with those old Altecs. They were only rated for 100 watts.
    They were fantastic speaker though. Very sensitive and dynamic. Some of the most musical speakers ever made. It would be a shame to destroy them with too much power.