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Thread: Box fb and voltage divider method

  1. #1
    Dave G
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    Box fb and voltage divider method

    Spent a few hours today finding fb of basic 4cu ft box tuned to 40hz built according to JBL enclosure guide. (two 4 by 6.5inch long ports 2226 woofer)

    Box has moderate bracing and thick fibreglass on back.

    Comes out to 35hz according to my calculations. This is lower then I expected but is this variation usual when performing the test?

    I do have a fine tuned frequency generator so can step in 1hz graduations and did roll back and fowards to find what I considered peaks on DVM.

    Did plug the ports and sealed with silicone for the sealed test but a small leak would sent the result out the window?

    Any tips from those who do this every month or so

    Dave

  2. #2
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    Plugging the 4.0 cu ft / 40 Hz specs into BB6P:

    Note Fill and Fb values -
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    and
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  4. #4
    Dave G
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    Thanks Giskard

    I was worried about ending up over 40hz with the volume of bracing. Looks like adding volume to box will not be needed. This box is MDF test before birch ply for Disco/music use. Bar handles not yet delivered as these have a small volume but I think I'm safe to cut wood soon. Win isd gives longer ports than 6.5 inch but this works.

    Anyone build birch boxes like this recently? Should be some pictures posted once this project is finished.

  5. #5
    Dave G
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    bump

    bump!

    Nearly finished, just perforated grilles with foam back to have cut.

    A test will be in order, neighbours permiting.

    Is this thread off topic being a pro woofer used for pro application?

    I heard rumours that this is only just enough for some members home Cinema.
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  6. #6
    RIP 2011 Zilch's Avatar
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    "Boom, boom,
    Out go the lights!"


  7. #7
    Dave G
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    hmm

    Quite likely.

    I shall have electrican on hand standing by with gaffer tape

  8. #8
    Senior Member Baron030's Avatar
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    I am very interested in how the 2226 drivers sound in a 4cu ft box. Having just received a pair of 2226 drivers, I am about to start building a pair of boxes, using chart #6 on the “JBL PROFESSIONAL ENCLOSURE GUIDE” as my plan. So, any advice would be helpful. Oh, and don’t worry about being off topic with a pro woofer in all. My project is to use a 2226H, 2012H, 2446H combined with a 2382A horn, and 2405H for my little home stereo system.
    So, pro components can be used for home applications too.

  9. #9
    RIP 2011 Zilch's Avatar
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    Gonna need a sub, too, probably.

    WinISD says 4.0 cu.ft. with 2 X 4" dia. X 6.5" long ports is tuned to 42 Hz and will play thusly:
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  10. #10
    Dave G
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    4 cu ft

    Hello Baron030

    I would expect that most members would choose a larger volume than 4 cu ft.

    5 might give you more extension for a home enviroment. I doubt you want the added complication of a sub in addition to the other components. A test box can be made and tuning is performed by varying port length as per this thread. I think the components mentioned make sense and you should be able get good sound from them.

    4 cu ft gives lots of kick but not enough low for most. Especially not suited for home cinema with that tuning. I only use a pair in 4 cu ft for disco use where they make lots of noise when fed thousands of watts. I'll let you know how eight sound at full tilt once testing performed

    My boxes rely on mutual coupling which changes things somewhat. Home Hi Fi was never the application of the 2226 it is made for efficency not extension. They are easy to get hold of though and you should be able to get some fun from yours.

    2235, now that is a impressive woofer for home. I'll say that before somebody else does!

  11. #11
    Senior Member spkrman57's Avatar
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    2226 is great "Mid-bass" driver!

    I use the for home HiFi use and most of my musical material does not require much below the 45hz that the 2226 does well down to.

    A sub for the bottom if needed would work well, but not much organ music playing on my system lately.

    I am using a Altec 902 driver on 650hz Edgarhorn (round wooden tractix) crossover is at 1.6khz 3rd order for top end, .7 mh coil for bottom end to reduce the rising response between 800hz and 1.6khz.

    Sound is decent, not totally hifi of course, but I can always throw a tweeter and sub on it if I feel the need.

    Ron

  12. #12
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    Hi Ron

    I am using a Altec 902 driver on 650hz Edgarhorn (round wooden tractix)
    - I'm curious here,,, what's the mouth diameter for that size of Edgarhorn ?

    - Is a 650hz Edgarhorn with a 2" entry much different in the overall diameter ?


  13. #13
    Senior Member spkrman57's Avatar
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    Edgarhorn info

    Earl,
    The 650hz round wooden Edgarhon is a 1" throat with approx 8" mouth. The lowest recommended bottom use is 800hz.

    The 350hz round wooden Edgarhorn is a 2" throat with approx 14" mouth. The lowest recommended bottom use is 500hz.

    The mouth sizes are from memory. I am pretty sure about the smaller one being 8" mouth. I have already sold the 350hz horn, but remember it to be around 14" - 15" as it was as large around as the 2226 driver below it.

    Ron

  14. #14
    Senior Member spkrman57's Avatar
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    Tractix horn info...

    Per Bruce Edgar, the tractix flare is not usable to the flare frequency like with other horn designs, ie: 650hz tractix crossed over at 800hz or higher.

    They are very directional and most people do not like them unless you are at least 12 ft back from the horns or more.

    I use them in a short room environment, but have them toed-in to the left and right of my listening position and tilted back to be aimed slightly over my head.

    This results in a slightly off-axis listening position which will leave some HF roll-off. Toed-in to the listener "dead-on" beams heavily. With low powered tube amps is not bad. With summer time here and warm weather, I tend to leave the tube amps behind and wait for cooler days. But with SS, I need to play at a lower level as they are not as soft as the tube amps.

    Just my 2 cents worth here of course.

    Ron

  15. #15
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    Thanks Ron for the info ,


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