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2x10 cab design.

Discussion in 'Amps and Cabs [BG]' started by Wxp4759cb, Dec 13, 2001.

  1. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    I'm trying to finish desinging my 2x10 cab (no tweeter). WinISD says I should make the cab with inner dimensions width 1.808ft Height 2.821ft and depth 1.132ft. Port, 4.02"x4.02"
    First off I'd rather the cab be wider than high, so I'm assuming I can switch the width, and height.
    I'm also assuming the shape of the port doesn't matter only the area.So I just want it to run across the bottom. Are these to assumptions correct?

    Also when I look inside my current 2x10 cab, the speakers look like they are each inside their own compartment, what does this mean? Should I do this?
    Here are my speaker specs., I have 2 10", if anyone has a good design help me out.

    RE OHMS 6.10
    FS HZ 46.88
    LE MH 1.12
    MMS GMS 39.10
    QM 7.63
    CMS mm/N .2946
    QE .460
    RMS NS/M 1.5097
    QT .440
    VAS LTRS 49.21
    XMAX MM 4.00
    SD SCM 344.88
    BL TM 12.34
    EBP 101.6
    EFF % 1.06
    SPL dB 92.2
    Wattage 150rms
  2. This is a nice design, especially for a 4-string bass, and will be just noticeably less loud than a Carvin RL210. It will also have a bunch more bass from low E to mid B than the RL210.

    Both drivers should occupy the same space. No divider. I would use a port at least 4.5" diameter to keep velocity at 0.10 Mach or less. The duct length will be pretty short.

    You can change the dimensions around in WinISD by changing any two and clicking on the 3rd value for the answer. This is not a true subwoofer, so shape is a bit more important due to standing waves. If you can get close to 0.618 x 1.0 x 1.618 which is the Golden Rectangle, this is as good as it gets. Try to avoid any two dimension being the same, or an exact multiple if possible.

    At first, these looked like Kappa Pro 10 drivers, but they perform a whole bunch better.

    What make and model are the drivers?
  3. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    Peavey Bam speakers, made by eminence.
  4. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    I'm not totally sure if I understand what your saying. Are you saying that I should use a circular port, instead of a vent that runs along the bottom? Do you think the dimensions WinISD gave me are good, or should I try and change them to match that golden triangle ratio? Finally when I said I want it wider than long, I just ment I want the speakers side by side, not one on top of the other, so basically I just wanted to know if I can turn the whole design on its side.

    P.S. Here is the part #, of that speaker
    PART # 70777213
  5. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Just a tip, from the ignorant:

    If you have a speaker cabinet and it has wheels on it, what do you do to stack it on another? Turn it on it's side.

    Doing this won't affect your sound. :)
    Tell me how much $$ the whole project costed, and how well it sounds when you're done, considering I may be doing the same thing. :)
  6. A bottom vent or slot port, will be a lot harder to adjust for the correct tuning. A round tube port is much easier.

    As for location, there are schools of thought about the location of the port, front to back, close to floor or away from floor, etc. I've never seen published tests that confirm or deny port location, so I'll leave that up to you.

    The golden rectangle dimensions are the ideal for preventing standing wave resonances inside the cabinet. A cube is the worst, but even a cube shape is irrelevant with true subwoofers. Your project is not a true sub, and I would not build a cube. Any other set of dimensions will do just fine.

    I doubt you will have any measureable difference between horizontal and vertical operation. You will probably see measureable difference by putting the cab on a chair and off the floor. Proximity to a rear wall, or in a corner will do far more for changing the sound than the difference (if any) between horizontal and vertical.

    If you build a leak-proof cab that does not buzz, and use a DVOM to tune it correctly, you will have a very nice performing cab. Remember to add about 0.12 cubic feet to the volume for *each* of the two drivers, or 0.25 cubic feet. I also add another 0.2 cubic feet for bracing. In other words, add another half cubic foot to the WinISD recommended volume.
  7. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    Crawling Eye, the speakers are $100 each (and a little tricky to get). I don't know how much the rest of the actual cabinet will cost yet.
  8. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    Does a round port sound as good as a vent on the bottom of a cab?

    Thanks for all your help.
  9. Davemell0


    Nov 19, 2001
    SW Virginia
    I believe a properly designed round or rectangular port will give you better bass response than a vent, and I would not recommend rear porting a cabinet, as having the bass frequencies bouncing off the wall behind your cabinet can have adverse effects. My drummer complains that my rear ported cabinet is making him deaf, and we have to be creative with our setup to get around this.
    I had a few questions of my own that I wanted to add. How would you go about calculating the pressure created in a cab by a certain set of drivers? I can calculate the mach number in a port, but I'd need the pressure inside the cab. Also I'd be interested to hear more on the benefits of having your drivers separated within the cabinet, I believe some companies do this on their 8x10. Finally, does anyone have any ideas on using PVC pipe to make ports, its relatively easy to shape, and it comes in lots of different sizes. It seems like it would be a good material, but most of the time I’ve seen rectangular wooden ports used when someone decides they need an odd size.
  10. Suburban


    Jan 15, 2001
    lower mid Sweden
    It will sound better when stacked on height.
    More sound and better definition. Something to do with the way the brain decodes the waves.
  11. BassMasterG,

    Where did you get the T/S data for the drivers? I can't find it on the Peavey site.
  12. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    That data was top secret. Many men gave their lives for it! Well not really. Actually, a local dealer got the part # from peavey over the phone (after several tries). Then I emailed eminence that part number and asked if they made it and what the specs were, they sent me back a message with the specs I put above. I've been working to get those specs, and the speakers themsleves about a month, it wasn't easy!:eek: :eek:
  13. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    NightBass pointed something out to me the number I posted earlier was the peavey part # (I'm ordered them from peavey's parts department so that was the # I used). The eminence part # is 101208. In the email they called that its "spec #"
    Sorry for any confusion.
  14. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    "To absorb internal standing waves and to prevent reflections into the woofer cone, we must add some sort of acoustic dampening material. Adding this material to an enclosure will effectively increase the apparent internal volume. This is important to note, especially with sealed box designs, since the enclosure should be filled close to 100%. Practical equivalent volume increases of 10 to 25% are possible depending on the amount and type of material used"

    Huh? I'm confused now. I thought adding internal damping material would decrease, the internal volume.
  15. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    "and use a DVOM to tune it correctly"

    Can you elaborate(sp)?
  16. Link to TB Thread on Stuffing Material

    If you are building a box, take the time to pick up "The Loudspeaker Design Cookbook" by Vance Dickason. This book willl answer all your questions about tuning and design.

    I use a digital VOM across the speaker terminals with a 200 ohm power resistor in series with the cables that connect the speaker to the amp. This creates a fairly constant-voltage environment to test the speaker. The amp sees the 200 ohm load, plus whatever load is in series from the speaker.

    At the tuning frequency, the speaker impedance is nearly the same as its DC voice coil resistance, i.e. 8 ohms. The impedance rises both below and above the tuning frequency in vented boxes. There is both an upper and lower resonance point. If you measure enough frequencies, you will see these peaks with your volt meter. The upper resonance (Foh) is useful, as this is where the port and cone radiation are fully in-phase. If the system is going to boom, it will most likely be at Foh.
  17. Tsal


    Jan 28, 2000
    Finland, EU
    The trick seems to be that damping material slows the sound wave down, so it takes longer to reach the walls. Which for the sound wave, has same effects than having a larger box.
  18. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    So Bgavin basically what I need to do is, cut the port a little small, then test it with a voltage meter, then keep making it bigger until it comes out right?
  19. Use the formulas that are available to calculate your port size and length.

    Cut the port over long, and shorten it as you test. This is much less grief than resizing a port diameter.

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