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Help with my junk !@

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  • Help with my junk !@

    Ok so I was given some B-52 MX-1515 cabinets and the compression horns are both blown up ,the crossovers appear to have been reworked by a blind one armed monkey but the 4 x 15" Eminence or however its spelled drivers still work and the cabinets are in decent shape. The only thing I will ever be doing is playing music from Youtube,MP3 player ,etc . Pretty much I just want a loud *** stereo that I will have in a 25'x14' room with 8' ceilings. Im looking for full sound lots of bass from these things and hopefully be able to crank em up without blowing them up . So I have some cabs with 3"x12" wave guides in them with 15" driver and no matter what placement they have a very fine line of sound that sounds good.Dang how do I explain this if im sitting on my couch ears say at 30" from ground and my compressions at same height and 12' away it sounds ok ...but if I stand up it all sounds crappy so what can I do to fill the room with more sound from them horns? Another question is what crossovers should I put inside them as far as hz and all that fun stuff? Thank you for helping my dumbarse out everyone the help is greatly appreciated....

  • #2
    So you have replaced the compression drivers already?
    Are you now using the cabs without an internal crossover?
    What processing(EQ) have you applied?
    What shape is your room and where are the speakers located?

    There are a whole bunch of things going on here..
    You have one of the worst speaker designs with dual 15's and a 1" CD. It's very likely both 15s get the same signal and the CDs are crossed high just to keep them alive. The problem with that is those 15's have to reproduce all the bass and much of the mids too and that simply isn't possible without making a mess of the mids at higher drive levels. AND... the output from those 15's narrows through the mid frequencies and to get out of the destructive interference pattern created by badly oversized dual midrange drivers that are operating too high you have to move further away. Then if we look at the compression driver and horn, it needs some specific EQ to help flatten the response on and off axis, the constant directivity horn type does a better job of spreading sound around but it will sound dull and have a lot of HF rolloff without corrective EQ

    The fix for all this is to turn the boxes into a semi 3-way, a low pass filter is applied to the bottom driver so it begins to cut off at about 500hz and it's only the upper driver that goes all up to meet the CD, and if a passive crossover is used it must include an L-pad to bring the output level of the CD down to blend in with the 15s. The boxes then need EQ, no way around this the sound will never be anything remotely close to hifi without it. The best type of EQ will be parametric, but unless you are very experienced in tuning by ear this will likely require some test equipment.
    Speaker placement in the room and the overall size of the room also has a hugh effect on the sound, it will take some experimentation to find the best locations and the boxes may need to be elevated for best results. It is also possible the horns have some built-in downward firing geometry, if the horns are symmetrical this could work to your advantage and allow you to flip them over and get better coverage without raising the boxes.
    Paul O


    • Professorsteve
      Professorsteve commented
      Editing a comment
      Hey Paul thanks for your help here my friend you have no idea how much you are appreciated along with all the rest of you that reply ..
      So answers to your questions
      No I have not replaced the compressions yet been kinda checking out options wave guides mostly
      I am not using the cabs not at this point yet ,they sit in a mountain of cabs that just seem to keep showing up over the past year or so in my room basically all crap really all passive tops and a few old passive 18" ELECTROVOICE ELIMINATORS that were donated by my daughters gymnastics class along with some FENDER 15" and a compession in a sealed cab . Which was nice of them but thinking of putting those over in the woodshop at moms house along with some home theater stuff thats in that collection I got . As for processing I have been told for my plan of only playing music via Youtube ,Pandora etc my best bet would be to go with a DBX PA2 driverack speaker management deal which I really dont know too much about yet being this sound reinforcement /pro audio is all brand new to me pretty much. But a buddy of mine said he has a DBX 231s graphic eq he said he would sell me ..Another thing I was told is if I go the driverack route I will no longer need a 3 way crossover to control my subs or an eq being because the driverack has it all built in along with all my filters i will ever need but thats why I am trying to learn as much as possible from you pro guys because seriously you guys impress the **** out of me with the vast array of knowledge that this whole side of audio takes just to turn the dang things on lol . Way badass !
      The shap[e is a rectangle its exact measurements are 18'x12' with 8' ceilings all just simple textured surfaces carpeted floor big king sized bed,desk, little couch so its packed as it is but i mean if getting a sleeper sofa will give me more bass /sound i'll get this bed out of here licity split ! Whatever it takes to get me closer to my goal of having a stereo system that if I feel the need to I can whick it on up and hit that bass so hard it makes my eyeballs shake to where I cant see straight.But would be insane is if I could hit as hard as some of the car audio guys hit in my house. Im even entertaining the idea of running a dedicated circuit to this system if need be. Which reminds me of power conditionoing and surge protection equipment important is this on this side of the audio world ? I assume just as important if not more important as everywhere else correct? Would you have a recommendation as to what would protect my stuff keeping in mind my stuff is pretty junky and not at all the best but I still want to protect it right because ive noticed this stuff can be real pricey real quick like here in this new side of audio ive taken a liking in
      Paul I also love the idea of turning the MX 1515's into 3 ways . Now that you have said something about them slaughtering the mids it makes complete sense to me ! And not to mention I dig doing projects like that I can build the heck out of cabinets thats also another lil hobbie I have and if it might help I love building bandpass Ive done lots of 4th order and did a 6th order for a friend that was insane. Transmission lines , Folded horns loaded everywhich way now Im thinking of maybe fiddling with building my first crossovers and such but have not quite got all the math and the understanding of all the capacitors resistors degaussing wire etc to just jump on in and start puttin circuits together just quite yet maybe soon though .
      So once again THANK YOU sir for sharing your knowledge and expertise with me I really dig chatting with everyone and learning all I can from each and every one on these forums that I can . Hope I kinda gave you a bit more info as to where im at and all that but if you have any questions or comments ,concerns or ideas ...anything feel free to send me a message or reply to a post and I will answer to the best of my abilities .But guys n gals im off to bed now get some sleep before these kids get up so hope to talk to ya soon and have an awesome fun filled day and im outtttttttt .........

  • #3
    Originally posted by Professorsteve View Post
    if im sitting on my couch ears say at 30" from ground and my compressions at same height and 12' away it sounds ok ...but if I stand up it all sounds crappy so what can I do to fill the room with more sound from them horns?
    Probably nothing. The horns are made for long listening distances and have narrow vertical dispersion to aid in that. The best you can do is to put the speaker height in a compromise position between when sitting and standing.