LDS 1-12s: Houston, We Have A Problem!

Discussion in 'Amps and Cabs [BG]' started by ::::BASSIST::::, Sep 4, 2010.


  1. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    Well, I've held off giving any indepth reviews of my LDS 112 cabs because since I got them, there was/is something not quite right about them... a mild distortion when I play low notes, especially 'A' and 'G' on the E string. At first I thought it was just the crappy sounding acoustics I have to put up with at the rehearsal studio I usually frequent. However, I've used them in about 4 or 5 different rooms now and I definitely felt something was wrong.

    So I grabbed my UL112 and did some driver swapping. I put the driver from the LDS (3012HO) into the UL112 box and the problem disappeared. I put the driver of the UL112 in the LDS box and the issue was there. The issue is what I understand to be chuffing. There is a hell of alot of air coming out of the two circular ports of the LDS cab. It sounds like a sheet of paper that is being vibrated at a very fast rate. Initially I thought it was some form of distortion but after careful listening, I am fairly certain the sound is coming from the ports. Its happening on both cabs so I'm guessing a design flaw?

    Is there any way I can fix this myself or am I going to have send the cabs back?
     
  2. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    Two other somewhat unrelated things I'd like to quickly mention. The 3012HO is a beast of a driver compared to the eminence neo that was stock in the UL112. Using my unaccurate kitchen scale I found the driver from the UL112 weighs "about" 4.5LBS while the 3012HO weighs approx. 7LBS. Thats quite a big difference...

    The other thing is that during my testing I found that the 3012HO worked pretty well in the UL112 box. If anyone needs to replace their driver in their UL112 the 3012HO seems to be a good replacement.
     
  3. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    i would think a chuffing problem could be easily fixed without having to ship them back. or am i wrong about that?
     
  4. will33

    will33

    May 22, 2006
    austin,tx
    The chuffing is too much air velocity moving through too small an area. It gets turbulent and will make weird sounds. It needs either bigger or more ports. Basically more port area. The problem may not have been there with some more "run of the mill" drivers but you have to think about that stuff when using something with the performance of an HO. It's excursion and ability to take some lows will really get some wind moving in the ports.

    Edit/addition: The fundamentals of the G and A are right in the 45-55hz area that's a pretty common box tuning for a lot of cab/speaker combinations. At those frequencies the ports are doing nearly all the work, that's the source of your noisy, high air velocity. The speaker/cone itself on those particular notes will be producing mostly 1st harmonic on up with the ports trying to put the bottom in.
     
  5. will33

    will33

    May 22, 2006
    austin,tx
    I don't know if you want to do this to your cabs by yourself or have them fix it if you're still some warranty period or something. I also don't know how the baffle is laid out or if there's room but the fix is to take those port tubes out and cut the circles out for a little bit bigger tube. More area = less velocity, the source of the chuffing. Some compromises will have to be made though. The bigger tube means it needs to be longer to reach the same tuning the cab is tuned at now. That will take a little box space away from the speaker which will affect it's lowend extension a little bit. It's a balancing act but the right answer is in there somewhere.


    It probably doesn't need to be a lot bigger, you gain a lot of area when dealing with circles. It's pi x r2.

    The area of a 2" circle is 3.14 square inches. A 2-1/2" circle has 4.89, a 3" circle has 9.42...3 times that of the 2" circle. A 4" circle has 12.56 square inches...4 times that of a 2 inch. The larger the pipe the longer it's going to have to be taking more box space away from the speaker.


    If you are still under a warranty/return policy or something like that it may be best to send them back and have them remedy the problem instead of hacking up your new cabs.
     
  6. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    There is quite a bit of surface area on the baffle to add additional port(s). However, I'm not sure I have the tools or the expertise to do it myself. If its just a matter of drilling a two inch circumference hole into the baffle and glueing in a port tube, I could do that. But I'd have to know the exact size of hole and the exact length of tube before I'd entertain the idea of trying it myself.
     
  7. wave rider

    wave rider

    Jan 5, 2005
    What did Don have to say?

    =wr=
     
  8. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    I just sent Don the email tonite.
     
  9. rpsands

    rpsands

    Jul 6, 2007
    The 3012HO needs about 20 square inches of port area for maximum excursion with a ~50hz tuning and no chuffing. If you have two 3" ports, you are about one more 3" port short. If you have two 4" ports you should have more than enough. One 5" port would be enough too.

    If you have two 2" ports you need a LOT more.

    Increasing port area would require changing the length of all three.
     
  10. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    I just measured and I have two 3" inch ports. Guess that means a 3rd one is needed? Seems strange that Don wouldn't catch that(?)

    In changing the length of all three, would the two already there have to be lengthened or shortened?

    If they have to be lengthened, I'll have to send the cabs back. The ports are glued in with some serious glue and there is no way I'm going to mess with all that. Hope Don covers the shipping both ways.
     
  11. jnewmark

    jnewmark Just wanna play the groove. Supporting Member

    Aug 31, 2006
    Stax 1966
    Third St. Cigar Records staff musician.
    Just out of curiosity, how big are the ports in the Epi ?
     
  12. will33

    will33

    May 22, 2006
    austin,tx
    They'll have to be longer. He maybe didn't catch it just because what he's using hasn't caused a problem in the past. Still should've modeled it out or did a real world test at full volume though. My 12's consist of older carvin branded heavy magnet speakers and emi deltalites and I haven't had a chuffing problem using port areas roughly similair to what he's using. The HO is a different animal though. It's kinda like souping up the engine in your car but not getting better suspension or better tires to handle it, can get a little squirrely when you put the hammer down.
     
  13. rpsands

    rpsands

    Jul 6, 2007
    Well, "by the book" the 3012HO might seem like it's ok with 14 square inches of port area, but the book allows for pretty high air volume that can, especially on attack, cause chuffing.

    I am not sure what it is exactly but bass guitar seems to be a different animal when it comes to port movement. Kick drum might be the same. The custom 1x12 I made with around 20 square inches of port area and a 3012HO could make port noise when turned up really loud with bass. But with recorded music you could crank it to the point of driving you out of the room.

    Edit: More info!

    The Eminence "small vented box" cabinet design for the 3012HO includes two 3" ports exactly and a 63hz or so tuning. However, it assumes a steel 70hz high pass used for vocals pretty much.

    If you look at the "medium vented box" the increased size means more low end a lower high pass...so it recommends two 4" ports.

    http://eminence.com/pdf/cab-kappalite-3012ho.pdf
     
  14. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    The epi has one square port. Not sure about measurements but it looks like its 3 x 5 inches.
     
  15. Tommygunn

    Tommygunn

    Nov 8, 2008
    Houston, Tx
    Uh, oh!
     
  16. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    Interesting.

    I'll wait to see what Don wants to do about this.
     
  17. will33

    will33

    May 22, 2006
    austin,tx


    That's 15, no more than the LDS. Shape,location and design of the port can have some effect on this as well. Do the round ports on the LDS feel smooth all the way through, no rough edges from cutting them from a long piece of stock? Are we sure the noise has been isolated to the ports and isn't some other loose hardware, bad glue joint in the cab that starts causing problems at higher volumes? Played it with the grill off?
     
  18. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    It's extremely simple to fix: turn down the bass and/or volume controls. May not make the OP happy, but it'll work.
     
  19. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection. Supporting Member

    Sep 2, 2004
    Vancouver, BC Canada
    Its definitely the ports. I took the grill off, tried all kinds of things like cable changes etc. I'm pretty sure its the ports. The ports on the LDS are smooth. I was testing them at a good amount of volume, but not super loud.

    I was just guessing on the measurements of the epi port. I'll take actual measurements to be sure.
     
  20. will33

    will33

    May 22, 2006
    austin,tx

    If the Epi's a square port built into the corner it can/will act different as far as airflow/turbulence etc. even though it doesn't have more area. For one, they don't have to be as long because the cabinet walls help to make up some of the port volume. If you send too much air through a round tube it can take on the properties of a flute.....or fart, whatever.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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