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Another speakerbuilding question...

Discussion in 'Amps and Cabs [BG]' started by jock, Apr 6, 2003.


  1. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    I think it would be fun to build a basscab this summer. A 2x10" no tweeter cab (I already have a 2x12" with tweeter and just want some more punch). I´d like to use the Eminence Kappa pro 10 or the Legend B102.
    When I put in the values for the kappa here I got an optimum volume of 10.3 liters. Not that likely I guess.:D
    Im not that good at calculating (as you can see)but I know how to use the tools and how to build a cab.
    So could someone please help me calculate a good volume and porting dimensions for two of these speakers? :meh: ;)
     
  2. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Also, which of the two drivers mentioned do you think is most suitable fo my needs?
    I want detailed flat sound with good punch and want to be able to use the cab on its one sometimes. I never use the tweeter in my 2x12 so the highs are not that important.

    Here are the links to the speakers too:
    Kappa pro 10
    Legend B102
     
  3. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    Bgavin has a very nice spreadsheet at: http://www.ofgb.org/

    -that has plenty of tuning information on lots of speakers.
     
  4. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    That´s a lot of info in that sheet.:eek:

    But when I put in the numbers in the calculating program it gives me an optimum volume. This volume is however too small to be practical. The cab would be like 3" deep.:rolleyes:

    Can the volume be doubled? What happens in that case?:confused:
    I found that if I put in a volume of about 40 litres and kept the other values I got a nice (similar to the optimum volume) looking graph. But I guess that´s not the way to do it.:meh:
     
  5. The small cabinet volume for these drivers does indeed pose problems.

    If you are using a vented alignment, the port area will have to large enough to prevent chuffing noises. Becase the cabinet volume is so small, the port duct will have to be a mile long to tune this box correctly. Long ducts (1/12 of wavelength) are used, organ pipe resonances become an issue.

    The solution for small vented boxes is a passive radiator.

    I have several Rockford RFR-2210 10" subs that I want to use for 1x10 cabinets. The SBB4 tuning is 0.54 cubic feet at 28 Hz. A correctly sized port for 0.045 MACH is 4.3" diameter, and 91" long in this box.

    I'm going to "cheat" on this box and make the port too small, so I can use less duct length. Using a 2.0" diameter and 18.5" length, Bullock's DOSBOX program shows vent velocity is under 0.07 MACH at 41 Hz. This is my lowest note, even though the box is suitable for a 5-string. At 500 watts with a 5-string, this box will no doubt make chuffing noise at 31 Hz.

    [ edit ]

    Neither the Kappa Pro 10 nor the B102 are going to give you any bottom end. -18dB and -15dB respectively at 41 Hz.

    Have you considered the Deltalite 2510 in SBB4? It is 1.39 cubic feet at 41 Hz, and down -10dB at 41 Hz. I use a standard footprint (width) of 20.75" for my cabs, so this would be 20.75 x 12.00 x 16.70 inches (external), with a 1.50" recessed baffle. Vent is 3.0" diameter, 6" long.
     
  6. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Actually that's a good question? What is the effect of a box that's too large.
     
  7. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    Basically, a larger box offers less resistance to the motion of the cone, and it gives the wave formed by the inward motion of the cone a longer pathway to cover before it exits the cabinet via the vent.

    A larger box will extend the low frequency response, BUT it also increases group delay (high group delay = lack of definition) and allows the driver to more easily exceed its x-max (= distortion). What you want is a box that is just big enough to allow decent low frequency extension while keeping group delay and driver excursion under control. You can easily design a box that looks great on a frequency response plot, but then when you look at the group delay and cone excursion plots, you clearly see that it's not viable. You can exceed x-max, but the further you push it the more likely you'll get distortion, so you want to design it to hold driver excursion within reason. If you go too big, you'll allow the driver to hit its mechanical limits (x-mech, i.e. actual damage).

    Bottom line, a box that is TOO large is no better than a box that is TOO small. It'll certainly sound different, but probably not good, and you run a higher risk of actually damaging the driver with an oversize box.

    As bgavin has recommended, SBB4 specs are usually the best balance of low group delay, cone control, and frequency response.
     
  8. It's called Extended Bass Shelf, or EBS for short. This is the design used by the Avatar 10" cabinets. The internal volume is typically 125 ~ 150% oversized from optimum.

    Link to Delta 10 in EBS


    Delta 10 Group Delay Plots

    Note the flat shelf in the EBS graphic. This is the classic EBS response plot. The bass is extended lower, but at a cost of a significantly higher group delay.
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Guess who's gonna go back and re-design his speakers.......

    My E145 cab and my P'Audio 2x10 are both too big as it turns out. Neither of them sound bad though. But now I'm curious to try them in their correct enclosures.

    You live and learn.......
     
  10. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I'm thinking of building a lightweight cabinet to house the whizzer-cone 12" 'full-range' driver that's in my Peavey 112MB cab. Does anyone know anything about this speaker and/or what it's parameters are?

    Cheers,

    Alex
     
  11. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    While manufactures of raw speakers are happy to hand out the T/S parameters, manufacturers of complete cabs are often unwilling to release that info. Protect their secret, make it hard for other manufacturers to steal their designs. I did a quick google search and came up empty, and that doesn't happen very often.
     
  12. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    So it´s allways best to go with the reckomended volume and tuningfrequency that these kind of programs give you? Even if the reckomended tuningfrequency is rather high?

    What is this SBB4?
    How do I check if my program is calculating with this boxtype? I use a demoversion of LSPWin 2.01.
     
  13. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    When it comes to vented box design, there are a few different theories and related formulas floating around. Each one gives a slightly different "alignment", box size, frequency response, transient response, and group delay. SBB4 is one of those alignments. It seems to be the one that works best for bass cabs. It provides the flattest response.

    Technically an SBB4 box will be tuned to the speakers resonant frequency (Fs). I've just learned via another thread that software programs will usually go for a a tuning frequency that's higher than Fs in the search for a flatter frequency response. Be aware that this can cause a shift in the group delay characteristics of the cab (ie the muddiness).

    I guess if you want to check if your program is using SBB4, post some of it's figures here on TB and get some feedback from the guru's. I know that WinIsd uses SBB4. The higher end programs will let you choose which alignment you want to use.
     
  14. WinISD used the Optimal Flat alignment.

    SBB4 is always tuned at the free air resonance (Fs) of the driver. The cabinet is usually a bit larger than Flat, and the bass rolloff occurs higher up. Group delay (transient response) is significantly better.
     
  15. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    It doesn't does it. All I found was Flite's cab with the same name, and a pdf of Peavey's manula for the cab. Most uninformative. The thing is that Peavey don't make this cab anymore and it didn't sell very well when it was available, despite it sounding so much better than old Peavey products. I've emailed them in the hope that they might reveal some info, but I'm not holding my breath...

    Alex

    P.S. The hope is that I can create a low budget version of the GK MB150, using the Sessionbass head and 112MB cab's speaker.
     
  16. Sometime back, Kurt told me that Flite uses off the shelf Eminence drivers. This makes it easy to run the numbers through WinISD and see the Flite performance claims are completely bogus.

    Anybody wanting to see how an Eden is made only has to take out one of the drivers and run the T/S measurements against it. The cabinet construction is evident once the driver is removed. Eden takes a driver that requires a large box, stuffs it into a small box and gets a big hump in the midbass. This is the Eden "bark" (read: boom) around 100 Hz that helps it cut through a live mix. This is also the Carvin RC210 method.

    This same technique of using high Qts drivers and/or systems is used in the retail music business to make speakers sound attractive to unwashed buyers. It is not uncommon to run a system Qt of 1.0 or 1.2 with the corresponding fat hump, to create the impression of bass by emphasizing the mid-bass.

    Personally, I'd rather have a cab without this gimmick. I can always turn my Mids control up to 10 if I want this type of sound.
     
  17. If you're looking for other options for 12" speakers with whizzer cones, I think Eminence has a new speaker out now with one. I saw it on their web site but didn't study it. also, Euphonic Audio has their new "whizzy" speaker out, and I've had good luck in the past when asking them for help. but that driver may be pretty expensive, judging by the prices they charge for replacement speakers.

    BT
     
  18. This is the Beta 12LT. The bad news is it is a high Qts driver (0.51) that requires 5.8 to 19 cubic feet, depending upon the alignment type.

    I still think the Legend B102 is the best kept secret in the Eminence arsenal right now. It is a 10" whizzer cone also, and great for 100 Hz and higher operation. I have two of them for my Magnum project, and will try one of them as a PA monitor.
     
  19. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Bgavin, if you have the T/S prameters for the Eden drivers handy, I'd love to have a look at them. Is it too much trouble to either post or PM the data.

    Also what program do you use to measure T/S parameters. I'm looking to buy something because people keep shoving all sorts of wierd and wonderful speakers in my face and saying "can you help me do someting with this".
     
  20. I don't have the T/S data for Eden because I'm not interested in them. They can be measured as described by Dickason in his book, with simple tools.

    There are several commercial probes and software that are very good. All are very pricey and intended for manufacturers.