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DIY 1x12 calculations: a little help, please?

Discussion in 'Amps [BG]' started by hobbes1, Apr 2, 2014.


  1. hobbes1

    hobbes1

    Joined:
    Nov 3, 2006
    Hi. There have been some really helpful people in the past who have steered me right and I'm hoping one or more of them might be willing to donate a few minutes of their time to running the numbers for me for a specific cab and speaker combination. I'm looking for max SPL and max Power specifically.
    I have a sealed cab that is 20"wx20"hx12d", 1/2" birch plywood with an existing baffle cutout for a 12 inch speaker, prewired with 1/4" jack plate. I have stuffing and can also add some 1" bracing inside if needed. The speaker I'm looking at is the Dayton PA310-8 with the following specs. Would anyone be kind enough to simulate this and let me know how it would work and what the best porting might be. Thanks in advance!

    Product Specifications

    Nominal Diameter12"
    Power Handling (RMS)450 Watts
    Power Handling (max)900 Watts
    Impedance8 ohms
    Frequency Response44 to 4,000 Hz
    Sensitivity97.2 dB 1W/1m
    Voice Coil Diameter3"
    Magnet Weight80 oz.

    Thiele-Small Parameters

    Resonant Frequency (Fs)44.4 Hz
    DC Resistance (Re)5.7 ohms
    Voice Coil Inductance (Le)1.53 mH
    Mechanical Q (Qms)8.63
    Electromagnetic Q (Qes)0.34
    Total Q (Qts)0.32
    Compliance Equivalent Volume (Vas)2.89 ft.³
    Mechanical Compliance of Suspension (Cms)0.21 mm/N
    BL Product (BL)16.94 Tm
    Diaphragm Mass Inc. Airload (Mms)62.1g
    Maximum Linear Excursion (Xmax)5 mm
    Surface Area of Cone (Sd)530.9 cm²
     
  2. hobbes1

    hobbes1

    Joined:
    Nov 3, 2006
    bump for "pretty please" :)
     
  3. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    Off the top of my head this driver is best suited for a ported enclosure of approx 2.5 - 2.8 cu ft tuned between 42 - 48hz.
    Are those the outer dimensions? If so the cab is approx 60liters.
    That's a bit small for that driver if you convert it to a ported enclosure, but I think it'll sound pretty good if you tune it to 45hz.
    Use two 4" tubes with a lenght of 11" to get the 45hz tuning.
     
  4. will33

    will33

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    May 22, 2006
    Location:
    austin,tx
    Disclosures:
    Use of this field for any other purpose is prohibited
    I'd follow Arjanks suggestions, though you might be able to get away with a pair of 3" ports so they wouldn't have to be so long (been working for me on 12's with similar xmax - no chuffing it seems). The 4" would have to be installed on a side, or use an elbow inside the cab to make clearance for the openings.

    You could try ut sealed first, but I'd expect weak lows and less power handling. The driver is really suited to ported cabs.

    PA-310 is a nice driver. I'd probably be using them if I didn't already have others that are suitable.
     
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  6. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Gold Supporting Member

    Joined:
    Nov 24, 2008
    Location:
    Preston, Idaho
    Disclosures:
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    Arjank's tuning looks fine to me too.

    If you decide to go with 3" ports, here's a trick that delays the onset of chuffing a bit: Cut the inside end of the port at a 45 degree angle, with the length measured along the centerline. This increases the cross-sectional area of the opening at that end, and that's the end where chuffing starts. At the other end, the baffle itself has a slight funnel effect - or at least is an improvement over nothing around the opening - which helps to smooth the airflow into the port.
     
  7. AstroSonic

    AstroSonic Supporting Member

    Joined:
    Dec 10, 2009
    Location:
    rural New Mexico
    After adding the driver, braces and port tubes you will end up close to 2 cf. Tuning to 48 Hz will result in a mild EBS alignment (-1db@90Hz, -1.8db@60Hz) offering relatively full bass and good extension (-3db@52 Hz, -5db@46Hz) and good driver loading to about 40Hz (minimal farting out with a 4 string). Suggest two 3-inch dia. (+1, will33) ports, 5 7/8 inches in length. Ports should preferably be flared/rounded at both ends. Models as handling 450w down to 42 Hz, below which it rapidly becomes excursion limited.

    If the entire box is made of 1/2 inch stock, suggest that you double the baffle board thickness.

    Keep the stuffing to a minimum with 1-inch thick padding on 3 nonparallel sides.

    The on-axis response of the PA310-8 dives above about 3.3kHz. While no off-axis response is given, it probably starts losing HF energy above about 0.8 to 1.2 kHz. Those preferring a vintage tone will likely find that more than adequate. Others will do well to add a closed back mid (for your pre-made box), and a full HP/LP crossover.
     
  8. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    Yup, two 3"ports will probably work well when flared.
    Tomorrow I'll do some simulations with AJhorn, my preferred sim-tool.
     
  9. hobbes1

    hobbes1

    Joined:
    Nov 3, 2006
    thanks a ton all. much appreciated. Arjank, thanks for checking into that further for me.
     
  10. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    Here ya go.
    55 liters tuned to approx 43hz gives a perfect response(left upper image) ;)
    The red line is ported, black is closed.
    Btw. it will have no problems with a low B
     

    Attached Files:

  11. AstroSonic

    AstroSonic Supporting Member

    Joined:
    Dec 10, 2009
    Location:
    rural New Mexico
    As you said earlier, good results are likely with tuning in the 42-48Hz range. The power sag (lower right graph) just above the max loading band (centered on Fb) with the 44Hz tuning is pretty severe: power handling is well below 200w between about 50Hz and 83Hz. This power sag is rapidly reduced as Fb is increased. Alignments are all about juggling compromises. My preferred alignment was 48Hz: it results in a different set of compromises (see post 6), and was optimized for extension, loading adequate for 4-string, and fullness. Either would likely result in a good usable cab.

    The OP could have fart-out issues with low B. Check the power handling below 40Hz. Yes, I know, the fundamental only has a fraction of the power in the note, but 20w power handling at 30Hz seems hardly adequate, especially if the low bass is at all boosted. A HPF and a little trial and error experimenting would solve this.

    Overall this could be a nice, very capable cab.
     
  12. hobbes1

    hobbes1

    Joined:
    Nov 3, 2006
    thanks for the further info.
    i have two different amps i use: one a GB Shuttle 6.0 and I normally have the bass knob rolled back a little (think 11 o'clock) and some mids boosted a bit.
    the other is a carvin dcm 1015 + Sansamp VTBassDI pedal (carvin has built in 15 band graphic eq. i keep the first two sliders all the way down (25, 40 Hz) and the 63Hz slider down about halfway).

    so, in general, i'm less of a bass boost and more of a low mid boost sort of player. I do play 5 strings though but I pretty careful about dropping in huge low notes without hitting the strings softer.

    also, i sometimes use an AKG WMS40 mini wireless and it only transmits 40Hz and up....hopefully, these things will help limit the likelihood of damage at the low end as well as the fact I don't usually need to play with the amps wide open.
     
  13. Arjank

    Arjank

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    Oct 9, 2007
    Location:
    Above Amsterdam
    AJhorn gives less optimistic(read: more realistic) results regarding powerhandling then WINisd does, even if I simulate it with 48hz, the power sag will not change much.
     
  14. AstroSonic

    AstroSonic Supporting Member

    Joined:
    Dec 10, 2009
    Location:
    rural New Mexico
    We all have our favorite software. I have no experience with AJhorn, but IME the most common and significant differences between the various programs are related to the bass ports: primarily end correction, and Fb calculations for rectangular vents. I seriously doubt that there is a practical difference between the power handling calculations from AJhorn, WinISD, BassboxX Pro, WinSpeakerz, Eminence Designer, etc. The fundamental calculations are relatively easy to implement. The only way I can get your result (such a deep power handling sag) is to set Ql unrealistically high and to substantially increase Vas. I will check into my program (a custom spreadsheet, not WinISD), although it has always seemed to closely reproduce the results of others including those in professional publications.

    In any case, that droop in power handling would likely be of concern to players who like a fair amount of energy in the 50-90 Hz range.

    The lack of power handling below 40Hz is likely of little consequence to the OP because he favors the mids and routinely attenuates the deep bass. It would be a problem if reproduction of the fundamental for notes below E were desired.
     
  15. Linnin

    Linnin

    Joined:
    Jul 19, 2012
    Location:
    Waynesboro, Virginia
    Can't you get some extremely well engineered plans for free straight from Eminence? I'm sure they have some, or just copy GK 112 or Fender Rumble 112 as they are almost identical and both use Eminence 12" Neo woofs. :D No need to reinvent the wheel or the woofer box. ;)
     
  16. Passinwind

    Passinwind Charlie Escher Supporting Member

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    What good would that do, given that he's using a Dayton ferrite driver?
     
  17. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    AJhorn is different, it uses a completely different model to calculate, read the manual to get an idea http://www.aj-systems.de/Manual.htm
    It's a pitty I only have version 5.1, version 6 is even more powerfull and accurate.

    If I use Boxsim to calculate the tuning, response and powerhandling I get approx the same results as WINisd cuz it uses the same method for calculation.
     
  18. Linnin

    Linnin

    Joined:
    Jul 19, 2012
    Location:
    Waynesboro, Virginia
    So, it's a box with a woofer in it???
     
  19. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    I wouldn't be concerned about that when using this Dayton driver, it's 5mm xmax is more "true" then e.g. some Eminence drivers.
     
  20. Arjank

    Arjank

    Joined:
    Oct 9, 2007
    Location:
    Above Amsterdam
    Here is the response simulated in boxsim.
    Boxsim takes the bafflestep into account so the response will look different from those calculated by WINisd, it's also not in half-space but in full-space.
    You also see that the powerdip is less pronounced in Boxsim then in AJhorn.
    Btw. If I double the xmax value in AJhorn I get the same dip as seen in Boxsim....
     

    Attached Files:

  21. B-string

    B-string Gold Supporting Member

    Joined:
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    Location:
    Lake Havasu City, Az USA
    G-K does not use Eminence. G-K builds their own drivers in house. A box is a box, a bass cabinet gets DESIGNED for a specific speaker. Invention is needed. ;)
     

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