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Need help from Expert cab builders...

Discussion in 'Amps and Cabs [BG]' started by haujobb, Aug 22, 2005.


  1. haujobb

    haujobb

    Dec 16, 2004
    Wallaceburg
    I ordered a 2x10 cab last year that, since it was only used for top end in a large stack, I never bothered to tune. This friday I'm doing a gig with just this cab so I need to tune the port to get the most volume possible. It all ready is loud and has tons of bottom in my room, I just want to get the most out of it for on stage.

    Anyways, the internals are 20x14x16.5. If I calculated it right, that is about 2.67 cu. ft. Correct? The port currently has a internal diameter of 3" and is about 4.5" long. The drivers are 10" Madison Knights.

    So I looked the driver up and entered the specs into WinISD beta and got a rediculously low -3 of 27 Hz. I'm pretty sure this is wrong so I tried WinISD pro instead, only this program won't even draw a plot for the drivers.

    Would it be possible for someone who knows what they are doing to model this box and give me a dimension to cut my port to? Thanx

    Edit: Website for Madison: http://vitacca.com/madison/
     
  2. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho

    The Qts of these guys is .75 which suggests a sealed cab. You might just want to plug the ports.
     
  3. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Agreed. It will be a bit quieter, but probably punchier.
     
  4. I would leave it alone.

    Yes, it has a high Qts, but the rest of the driver does not lend itself well to a sealed box.
     
  5. haujobb

    haujobb

    Dec 16, 2004
    Wallaceburg
    In that case I suppose I can just plug the port with something to test out that theory. Still if it needs to be vented, I can't figure out how to tune it...
     
  6. Here is how you figure how to tune it:

    1) Determine the T/S parameters
    2) Look up the volume and tuning required for this driver
    3) Size the cabinet 2x the volume required for 1 driver
    4) Get a digital VOM
    5) Download TrueRTA free version
    6) Hook a power amp to LINE OUT on your sound card
    7) Measure voltages at 3 digits precision, 20 ~ 100 Hz
    8) Note the lower and upper high voltage points
    9) Note the lowest voltage in the middle, this is the tuning
    10) Adjust port lengths until correct

    Each Knight 10 wants 4.85 cubic feet for Optimal tuning. The box should be tuned to 31 Hz.

    It should be obvious by now that this driver completely sucks. IMO it has all the value of a paper weight... not to p!ss on your parade, but this is how the numbers work out.

    I'd spend a lot less time worrying/fiddling with this driver, and simply play it. If you don't like it, then sell it and get something better.
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Go back to WinISD and tweak the tuning frequency to get the maximum sensitivity at 50-60Hz. What that fb is doesn't matter. Make sure you deduct both the volume occpied by the drivers and the volume occupied by the duct to arrive at a net cabinet volume. Yours is likely closer to 2 cu ft, your current port would tune that to about 37Hz. The tuning frequency does not determine f3, it's the combination of the fb and the driver specs that does that.
     
  8. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    Given that it's a 10 and only has a moderate magnet structure, I'd only use it as an indoor paperweight. :)
     
  9. haujobb

    haujobb

    Dec 16, 2004
    Wallaceburg
    The thing is, I do like it. Is there something wrong with me :p
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    WinISD Pro can be fiddly and I can see two potential problems which caused this.

    1) Sometimes when you change one of the parameters, it resets the tuning freq to Zero and all the plots disappear. It's a glitch which will probably be fixed at some stage. WinISD Pro is still and Alpha test version after all.

    Chances are you changed the size of the ports to match your box. This reset the tuning freq to Zero. Go into the "Box" tab and enter a more appropriate tuning freq and the plots should appear.

    2) WinISD Pro's driver database is fussy. It preferes you enter the T/S data in a specific order. Chances are you used the driver data as entered in the previous version of WinISD, and WinISD Pro is having trouble reading it.

    To fix it, add the driver again from scratch, but do it in the prefered order. You can find notes on the prefered order in the WinISD Pro help files.
     
  11. haujobb

    haujobb

    Dec 16, 2004
    Wallaceburg
    I tried the first one, I'll have to give the second a go tmm...
     
  12. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Get WinISD Beta, it's much more user friendly. Alpha has a better data base and some nice features if you're quite the expert in its use but is almost impossible to get a simple fast result from. I only use Alpha if I need a certain bit of information that Beta can't give, which isn't very often.
     
  13. Not at all.

    Taste is entirely subjective. My point is entirely about the driver being difficult to accomodate in a reasonable volume, and with reasonable results.
     
  14. Why doesn't someone try Eminence designer? Reasonable results on paper and on graphs don't reflect whether it sounds 'good' or not too. I re-loaded a friends Trace Elliot 2103H (2x10 vented box with an fb of 45 hz) with eminence Beta 10s. I punched all the info onto the program and it gave what looked to be 'average' results; I exceeded Xmax below around 120hz at even half power, my -3db point was something like 72hz. Doesn't look great but in actual fact, the new drivers sounded much 'better' than the original celestion units IMO. Low end is warmer and punchier with no signs of complaint. Its driven by my old AH400SMX so into 8 ohms thats around 300w into the box (the rating of the two drivers). It sounds great...
     
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The price and the limitation to Eminence drivers. You do make a good point, though, that predicting good sound from response charts alone is a dicey proposition. What they are more useful for is comparing different drivers and for anticipating how a new box might work based on experience with exisiting cabs.
     
  16. If you have the T/S parameters, they can be punched in. I've never heard of the speakers in question at the begining of this thread but as long as you have the T/S, they can be modeled with Eminence designer. I've put a load of celestion drivers in on my version, checking the specs of my Trace Elliot cabs. I made a slight error on my previous post, the f3 on the 2x10 was 67, not 72 hz as stated. I checked the specs on my Trace Combo last night, the Vtype 4808 (4x8" vented). The response was again not so good on paper, an f3 of 104 hz even with box tuned to 52 hz but it doesnt seem to lack any bottom end thump or any 'holes' in the response. The Fs of the driver itself is naturally quite high at 80hz and after 90 or so hz, exceeds its Xmax slightly, but due to the vented design doesn't get daft until below 50hz. For the record, thats with an input power of 220w RMS, as its fitted with the latest generation (clive button) 300w power stage after the old bi-polar bear died. According to Trace this is the approx output at 8 ohms. I don't remember who's quote it is but someone on here has 'Listen with your ears not your eyes'
     
  17. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That was probably me. I can't speak to the specifics of the Eminence program as I don't have it, but as to the rest of what you're saying it goes back to the common misconception that an electric bass requires a speaker that plays relatively flat to its lowest fundamental frequency. It just isn't so.
     
  18. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    That's been my sig for years. Thanks for listening :)
     
  19. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Just call me Milton Berle.
     
  20. Almost nobody here will get the joke...

    :D