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Problems with mixing speakers?

Discussion in 'Amps and Cabs [BG]' started by Myth_103, Mar 17, 2009.


  1. Myth_103

    Myth_103 Supporting Member

    What problems would one face if they were to put 2 different 10" speakers into the same box? I understand the frequency responses would be different etc..., but what would this cause? Combine say a bp102 and a b102 so there would be high-end from the whizzer and bottom from the other.
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    If speakers with different Thiele-Small parameters share a box, any prediction of performance using mainstream techniques and rules of thumb go out the window. It might work or it might not. Adding an internal baffle would make the behavior of the box more predictable.

    Also, the driver with more low end capability will also have lower overall sensitivity.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You won't get the low end that the BP102 is capable of delivering because the smaller xmax of the B102 will cause it to fart out at 1/4 the power limit of the BP102.
     
  4. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Hoffman's Iron Law only has 2 variables?
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Hoffman's applies to the size of the cabinet, not driver parameters.
    Not necessarily.
     
  6. Could you expand on that (xmax)? I've been toying around with the same idea.
     
  7. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    xmax is the amount the cone will move once signal is applied. if you have more available xmax, you'll generally move a lot more air.
     
  8. Yeah, I read up on that after I posted. Just the same, is there a compelling reason to steer away from this particular combination other than the hard specs? That is to say, if it sounds good, I'm not inclined to fret over the graphs.
    To be specific, I'd like to put two pairs of BP102s and B102s in a 4x10 sealed Bassman cabinet. I tried using 4 BP102s, but that was all woof and no definition. On a side note, if I go with this, would either pair on top versus bottom make a serious difference?
     
  9. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You could break with tradition and do it the right way, using a 6 inch midrange or two to give what the BP102s can't.
    If you take out two BP102s and replace them with B102s what you'll gain in the mids you'll lose in the low end. BTW, you're also losing more than half your low end capability with a sealed cab.
     
  10. Given what I've spent on qualified successes and unqualified failures, I will take your advice to heart. Thanks to both of you for the input.
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
  12. vaxvmsm3

    vaxvmsm3

    Mar 16, 2010
    Hello, TalkBassers!

    I've followed your threads for a while, but never thought to register and contribute, usually being more a guitarist than bassist. However, having been playing a bit more bass than usual for the last 4-5 months, a couple of threads I've just read prompt me to reply.

    I've just finished reading the 2 stickies regarding A) Mid-drivers versus tweeters, and B) mixing-and-matching drivers and/or cabs.

    And now this one, because it addresses my situation, in particular:

    Ok, I have a Peavey 210 TX with some kid of Peavey 10s in it, and what looks like a decent compression driver for highs. (I say this just from looking into the port in the back of the cab. I can't immediately see how to take the cab apart, and until I hear from you guys about my question, I'm not even going to try and figure out how to, yet!)

    The 10s sound blown to me. They make fairly good LOW lows, and decent highs, but when I throw any mids at them at all, they fart / rasp out. (Which seems weird to me. In my guitar amps, it's the lows that generally reveal a bad driver. Anyway, that's how it seems ...)

    So, I thought about replacing the drivers, and my research led me to the BP102. Then my research on the BP102 led me to think about maybe using one BP102 (for low lows) and one B102 (for mids, till I reach the tweeter). Then, that research led me to the threads mentioned above, and to this one.

    But having read ALL those, I still don't know exactly what to do. So, I'm going to ask YOU guys!! I'll tell you what I've got and what my goals are, and hear what the experts say!!

    Ok, here's what I hope is the relevant info:

    1) Goals, in order - I want the cab to be about as portable as it is now, but I want it to make louder, lower lows and be able to handle more power than it does now. (I think mids and highs would be fine as is, if 10s weren't blown.)

    2) Specs - Box is 17 X 16 X 24. 17" deep, 16" tall (Or, actually, wide. I usually run it on it's side.), and 24" wide (Or 'tall'!)

    Box has a 4", round port in the back, mounted with the edge of the port about 2" down from the top-center of the rear panel. The port has what appears to be a 4" diameter tube of cardboard in it, extending toward the interior of the cab. This tube is 4" long. The port is directly behind the tweeter driver, because the tweeter is mounted in exactly the same point on the front panel.

    The box has a 3/4" board inside which appears to mostly separate the two 10s from each other. It's mounted directly between them, and extends all the way from the front panel to the rear panel, and from the bottom panel up to the bottom of the port. So it leaves about a 6" open air space at the upper-rear of the interior of the cab, right where the port / tube / back-of-tweeter is.

    Tweeter says Fostex on it. 025H27. Also says IMP 8 ohms, and Mus 150W. Cab says it's crossed over at 3500Hz.

    Don't know anything about the 10s. They say Peavey on them. And Model 121 #96000296. 8 ohms.

    The whole cab is rated at 175 watts RMS and 350 'Program'. And 4 ohms.

    So, can I put a BP102 and a B102 in there?

    Or, due to the advice above about the B102 farting out, could I put a 4-ohm BP102 and an 8-ohm B102?

    Ok, that's it! Sorry for the long post, and for hijacking, if that's what I'm doing.

    (PS. I'm new at posting in forums. I did read the rules, but I'm still not sure if this post is ok here, or if I should have started a new thread. I know you're not supposed to hijack a thread, but I don't know if this counts or not.)

    If I should have started a new thread, would someone please tell me?

    Thanks in advance for any thoughts, insights, advice, or direction!!

    Tom
     
  13. Doesnt someone already make a cab like this? Sounds like an Acme or Schroeder idea.
     
  14. vaxvmsm3

    vaxvmsm3

    Mar 16, 2010
    I don't know.

    I'm new at being a bass player.

    This is just a Peavey cab, but I was hoping that if I put some better drivers in it, it might sound really good.

    The cabinet itself is fairly small, but it seems very solid. It weighs a TON and when I play it as loud as it will go, there are no weird noises except for the drivers rasping. The cabinet doesn't seem to rattle or buzz at all.
     
  15. vaxvmsm3

    vaxvmsm3

    Mar 16, 2010
    In fact, I guess the more I think about it, the more I don't see why I couldn't put one BP102 and one B102 in it.

    I mean, both of them are speakers that are designed for bass guitar. And they're both rated at 200 watts. So why should the B102 'bottom out' or 'fart out' any sooner than the BP102.

    And if that's true, then I should be able to buy the 8-ohm version of each speaker, wire them in parallel, and end up with a 4-ohm 400-watt cab, instead of a 4-ohm, 175-watt cab, which is what it was originally.

    And I'd have the BP102 covering low lows, the B102 covering mid-lows and mids, and the Fostex horn covering highs, if necessary. (The Fostex is already in the box and already wired with an attenuator, so why not?)

    And since the box originally came from Peavey with 2 10s in it, then presumably, it's already tuned and ported for 2X10 + tweeter, right?

    So, what do I seem to be missing here, experts?

    Thanks again,

    Tom
     
  16. vaxvmsm3

    vaxvmsm3

    Mar 16, 2010
    In other words ....

    Quote:
    Originally Posted by billfitzmaurice
    You won't get the low end that the BP102 is capable of delivering because the smaller xmax of the B102 will cause it to fart out at 1/4 the power limit of the BP102.

    ..... why would the above be true?

    Both speakers are rated at 200 watts, so why would we expect one to fart out at a quarter of the power limit of the other?

    Thanks in advance ...

    Tom
     
  17. gumtown

    gumtown

    May 7, 2007
    New Zealand
    Sorry i can't offer technical data, but from my 30 years of mixing and matching speaker drivers experiance tells me that a pair of speakers sharing the same air cavity or box should be a matched pair. Reasons being that if one is a woofer and one is a mid, the woofer will push the mid speakers cone around like a passive radiator, and the speakers will at some point 'fight' against each other.
    Sounds like you need something like a 12" or 15" (or the 2 x 10's) sub and a 6" mid, connected with a passive crossover.
    Maybe 2 x B102 might be better.
     
  18. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    Like mine...210 loaded with BP102's and a 6" mid in it's own chamber...Sounds beautifully smooth from lows to highs. Though a bigger cab would give even deeper lows (I just didn't need that).

    There really is little point in using anything larger than a 6" driver for mids and highs. Wasted space IMO.

    [​IMG]
     
  19. Bill already explained it.........

    The X-max rating of a speaker determines the low end displacement limitations of the speaker.

    Just because they are rated for the same wattage (which actually means nothing), it does not mean that they can reproduce the same low end frequency range and at the same power levels.
     
  20. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    Speakers are designed for an intended use. Of all the T/S specs, wattage is the least important data. The BP102's go deeper with a larger xmax. By pushing bass through a single cab loaded with both, the B102's will literally be pushed around by the BP102's in the low end...until the B102's are confetti.

    But hey, if you insist...go ahead and build it. Post back and let us know how long your B102's lasted.
     

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