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Bass cab Deltalite 2510II

Discussion in 'Amps and Cabs [BG]' started by Northwood, Apr 24, 2018.


  1. Northwood

    Northwood

    May 2, 2013
    Denmark
    Hi guys.

    I have a spare 2510-II 8 ohms on hand and want to make a small lightweight practice cab.
    Now I need confirmation on a cab design I made.
    First thing. I have a choise making a flat frequency response or decrease cab size with a bump in the mid bass.
    Keeping in mind this is a small practice cab, I dont expect it to have lots of low end. I rather have a strong mid range.

    +3 dB @ 99 Hz
    VB: 34,5 L
    FB: 72,4 Hz
    F3: 65,7 Hz
    Rectangular shelf port: (WxHxD) 288x50x156 mm

    I am not sure if the 99Hz is a good spot or what effect it will have to move closer to 90 Hz.

    Do you have any suggestions improving this design?
     
  2. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    Imo your tuning frequency of 74 Hz is on the high side. Yes the frequency response curve looks good, but the problem is, below the tuning frequency the cab doesn't provide much back-pressure on the cone so you can easily drive the woofer into over-excursion (fart-out).

    If you tune to low-E, I suggest lowering the tuning frequency to the upper 50's. If you tune to low-B, then I suggest the upper 40's.

    Even with those lower tunings, that rather large internal volume (for a Deltalite 10) will make the cab more prone to fartout than you might want. Personally, I'd be inclined to go with a smaller box, maybe 25 liters, for the sake of fartout resistance.

    I don't understand this sentence: "I am not sure if the 99Hz is a good spot or what effect it will have to move closer to 90 Hz."
     
    AstroSonic likes this.
  3. Northwood

    Northwood

    May 2, 2013
    Denmark
    Hi Duke.

    I have a 5-stringer with low B.
    The +3dB was a boom box pre load in the android app I used. With a variable mid-bass bump.
    I'm in WinISD now :)

    I get your point. I modelled at 25L and 49Hz and get cone runaway at 40Hz.
    In my design I had cone over excursion at 55Hz. Huge improvement.
    According to ISD Xlim at 8 mm is reached at 39Hz, 250W. This seems a bit overrated...

    I plan on using a slot port at the bottom ala the fearful 12/6 I own.
    Port dimension will be 27x2x20.85 cm. Any problems here? Air velocity etc.
    Another option is triangular port(s)

    EDIT:
    The cab has a cone excursion bump around 80Hz. Is it ok tuning against Xlim at 250W?
    Xlin is at 80W.
    What is acceptable air velocity in a slot port?
    New port dimensions: 26.4x2.8x25.8
    Tuning: 28L, 49Hz

    Thanks
     
    Last edited: Apr 27, 2018
  4. Northwood

    Northwood

    May 2, 2013
    Denmark
    Bump!?
     
  5. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    That sounds great to me! I think that's plenty of port cross-sectional area. I've read that the threshold for acceptable air velocity is about 34 meters per second, or approximately Mach .10 (point one zero). But if you can get away with it, bigger is better, because compression starts to set in before outright chuffing.

    Note that your peak air velocity will probably be down around 30-35 Hz. If you're putting 250 watts into the cab (the rated thermal power handling of the Deltalite), I wouldn't expect those lowest fundamentals to get much more than 60 or 70 watts, unless you're deliberately boosting the very bottom end. So in other words the energy distribution of electric bass gives you more chuffing threshold than the raw numbers of a modelling program predict.

    The excursion-limited farthout threshold is unfortunately easier to reach, at least theoretically, because the excursion requirements of the overtones in effect stack "on top of" the excursion requirement of the fundamental.
     
    Last edited: May 1, 2018
    AstroSonic likes this.
  6. Northwood

    Northwood

    May 2, 2013
    Denmark
    Thank you Duke.

    The port depth is restricted by cab depth. I have 332mm from front shelf to back panel.

    ISD is calculating a port depth of 260mm (hight 28mm, lenght 266mm) and an end correction of 0.732, presuming one flanged end (which is not exactly true as I recess the front baffle by 30mm)
    So I need to multiply the port depth by the end correction, having an actual port depth of 190mm, right?
    Which means I can calculate a deeper port, right!?
    A hight of 30mm equals a depth of 332mm, end corrected to 243mm.

    Won't the space between the shelf and the rear panel act as a partial port extender?
     
  7. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    I don't use shelf ports and I don't use ISD so I don't have hands-on experience with either one, sorry. I think what you are saying sounds right.

    Yes.
     
  8. Passinwind

    Passinwind I know nothing. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    WinISD is famously wonky as far as predicting shelf port length, and the bolded part of your quote is presumably mostly why. You will typically end up at around 2/3rds of the predicted shelf length, at least IME. There are a lot of other software solutions that do a better job, I like Boxsim personally.
     
    DukeLeJeune, Arjank and ThisBass like this.
  9. Northwood

    Northwood

    May 2, 2013
    Denmark
    Thank you for your interest, Passinwind.
    Never tried Boxsim before, but after fiddling around this evening, I find its nowhere as easy got-to as ISD.
    The driver data I enter doesnt get copied to the different parts of the program, so they have to be reentered. A bit tedious.
    And the port data is way off compared to ISD - or vice versa. Am I doing something wrong?
    Multiple ports is not an option - I want a port divider to brace the panel.
    Countersunk baffle is not an option - The port and other panels protrude 30mm from the baffle.

    What Im trying to say - I am not smart enough to get under the skin as quick as other sims.
    Can you help me out?
     
  10. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    Exactly.
    I did own a 2510-II and got pretty useful results in a 24liter cab tuned to 52hz. The smaller cab volume keeps the fartout threshold in check.
    I ditched the 2510-II because I didn't like how it sounded when it exceeds xmax so keeping the cone-excursion under control is a good thing to do with this driver.
     
    Last edited: May 3, 2018
    AstroSonic and DukeLeJeune like this.
  11. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    I always use Boxsim (free ware) to calculate the port length since it takes the distance of the port in relation to the inner walls into account. Below an example of how to calculate the port length in Boxsim.
    SWR Goliath III tuning.
     
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  12. Northwood

    Northwood

    May 2, 2013
    Denmark
    Multiple ports are only available if I choose round ports. Why is this and how do I correct for a port divider/panel brace other than the divider thickness (12mm)?
    Boxsim seems to do some calculations, but the different plots are empty. No frequency response curves or anything.
    The latest cab iteration is attached.
    Notice the short distance from shelf to rear panel.
    My goal is 300mm overall cab width.
     

    Attached Files:

  13. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    If you add a divider panel to the slot port just substract the 12mm from the port area.

    The tool in Boxsim for calculation the port length doesn't show the curve, only the tuning frequency. You can do the curves in a different part of the program.

    I will look into your design later :)
     
    Northwood likes this.
  14. Slight correction. Subtract the cross sectional area of the divider from the port area,

    or subtract the width of the divider from the width of the port if it's self calculating the area from width and height.
     
    Northwood and Arjank like this.
  15. Northwood

    Northwood

    May 2, 2013
    Denmark
    Update!
    My cab is almost finished. I took it to a rehersal today and I am very pleased with the result.
    Its small, lightweight, articulate, have a good low end and cost me next to nothing. Perfect.

    You can see it squeezed in between my fEarful 12/6 and my Sandberg Custom 5. On top rest an Ashdown LG1000.
    An easy one trip setup. Bass on the back, cab in one hand and a bag with amp, score sheets and other stuff in the other.

    Thx everyone for your help :)
     

    Attached Files:


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