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OK electrically minded, help the stupid

Discussion in 'Amps, Mics & Pickups [DB]' started by Marc Piane, Feb 27, 2008.


  1. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    OK. Here the situation. I have a little carvin pa cab (10" and a horn) that I use as an extension to my gk once and a while. It actually sounds surprisingly good and is just the size I want. I can't really afford a new cabinet anyway... at least until the government sends me my check... and truthfully this setup has worked really well.

    Here's the question. I picked up a better quality (Eminence) 10" driver. It is rated at 8 ohms with 200 watt power handling. I want to disconnect the tweeter in the cab and just hard wire the speaker directly to the jack bypassing the crossover. Is this the right thing to do?
     
  2. Is it the right thing to do? If you want just a woofer and no tweeter, then yes. You will need to either unplug the tweeter or remove the crossover. Then you can wire direct to the input jack.

    + will go to the center pin for the cord
    - will be the sleeve.
     
  3. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    A better quality 10" and no tweeter is exactly what I want.
     
  4. You could document what you did with a little drawing taped inside so that if you ever want to reinstate the crossover at a later time you will know what you did. I always seem to change my mind down the road and want to know how to get home!
     
  5. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    The Eminence driver itself may be better quality but may not offer an improvement once it's installed in the cabinet. If, for example, it is a ported cabinet, it has likely been "tuned" for the driver that's in it. You might get lucky-- maybe not. If the crossover consists of a low-pass and high-pass section (for the woofer and tweeter respectively), then the easiest way to by-pass the crossover is to disconnect the leads currently going to the woofer and wire new ones to the jack. On the other hand, it is likely that the crossover consists of nothing more than a high-pass filter in front of the tweeter. Sometimes they are just tapped off the woofer leads. If that is the case, simply disconnect the leads from the woofer to the HPF and you're good to go. If the HPF is tapped off the jack, then just disconnect it there. Fell free to PM me if you need more detailed help.
     
  6. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    Thanks for the info guys. I'll keep you posted on the results.

    Not that it probably matters 'cause the proof is in the puddin' but it is a vented cab and the speaker Eminence says is designed for vented cabs. They have a different model they market for sealed cabs. They also give "Recommended Enclosure Volume" and it matches fairly closely to the cab I plan to put it in.

    We'll see.

    Any other input is great.
     
  7. Lia_G

    Lia_G

    Oct 27, 2005
    If you can measure (or approximate) the internal volume, and the measurements of all ports, I'm happy to feed it into WinISD pro for you along with the driver and give you predicted frequency response charts. Just let me know.

    Cheers
     
  8. robgrow

    robgrow Supporting Member

    May 1, 2004
    Cincinnati, Ohio
    I have an Eminence Legend B102. It's just OK, but nothing special. Interestingly it doesn't compare very well in overall sound quality or sensitivity to the custom Eminence-made driver in the EA Wizzy 10 (which the B102 superficially resembles). I tried the B102 in a couple of different cabs each with a couple of different tunings, but the results were about the same, so I don't think the cab that you use it in is going to make a huge difference.

    Hooking up the B102 is very easy. Just connect the wires from the cab's input jack directly to the speaker's terminals, and you're done. Make sure the wire from the tip connection on the input jack is connected to the terminal marked "+" on the speaker. It should also be very easy to disconnect the tweeter and won't cause any harm.

    Have fun.
     
  9. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    Thanks Liam. I may take you up on that.

    My goal is to upgrade the Carvin driver that it has in it now. I talked to a buddy that upgraded a 2x10 Carvin combo amp (so I'd assume the same 10" Carvin speakers) with these exact speakers and he said it made a big difference. The thing has served me well as is. The Eminence speaker was $80. If it makes the thing sound even a little better I'll be happy.
     
  10. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    Actually, although I'd follow this convention, reversing the leads would simply flip the phase which is of no consequence unless you are concerned about matching it with another, simultaneously driven, cabinet. In fact, flipping phase at the speaker terminals is a cheap, if cumbersome, way of achieving what the phase-reversal switch does that is found on many pre-amps.
     
  11. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    It would be an extension cab to a GK MB150.
     
  12. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    Probably following the convention is best then. Here's a link to the free WinISD software that Liam mentioned in case you'd like to play with it yourself.
     
  13. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    One note is that the Carvin driver, if you look at the model number on the driver itself, may have Thiele-Small parameters at the Carvin website. This would let you model "before and after" to decide how big a change to expect.
     
  14. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    One last question.

    What does the sensitivity rating of a speaker mean?

    The Carvin manual says : 98db SPL, 1 watt @ 1 meter

    The Eminence manual just says : 93

    I've heard talk of this stuff 'round here but remember, I'm not that smart. Please keep it simple.

    Also, is this that Eminence not 'good'? I've noticed with most high end cabs (and not so high end) it hovers around 100db SPL. I can return the Eminence if this is not a favorable rating.
     
  15. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Sensitivity is how loud the speaker gets, in SPL, for a given amount of input power, when you are standing a certain distance away from the speaker. The typical power and distance for this rating are 1 W and 1 meter.

    With that said, a speaker could have different sensitivity at different frequencies, thus a single number could be:

    a) Some kind of average

    b) The value at the most favorable frequency

    For a 10" speaker, 98 dB is extremely optimistic, and in fact 93 dB is probably representative of what a typical decent 10" can do in the bass.

    So you're probably OK.
     
  16. Greg Clinkingbeard

    Greg Clinkingbeard

    Apr 4, 2005
    Kansas City area
    KC Strings
    Francis,
    :eyebrow:
    We'll need to talk off-line about licensing fees. Call me.
     
  17. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    To be technically correct, the ratings on loudspeakers are more akin to efficiency. The rating is not how loud a cabinet will be, but what the physical sound-pressure level will be for a given input of power. Loudness is a subjective, psychological quantity. My buddy fdeck knows this. :)

    The rating for a raw driver is essentially meaningless. What SPL will be achieved is intimately related to what cabinet the driver is in. Keep in mind that every 3 dB represents a factor of two in power. So, a cabinet rated at 93 dB SPL @ 1 meter, 1 watt will produce half the acoustic power as one rated at 96 dB SPL @ 1 meter, 1 watt. Every 10 dB represents a factor of 10 in power. So, a cabinet rated at 93 dB SPL @ 1 meter, 1 watt will produce one-tenth of the acoustic power as one rated at 103 dB SPL @ 1 meter, 1 watt.

    As for loudness, the perceived loudness roughly doubles with every 10-dB increase. So, in the last example above, the latter cabinet will sound roughly twice as loud as the former given the same input power.

    For another example, see this.

    fdeck is quite correct that the ratings may be some sort of average. That is where the frequency response come in. If one knows that the cabinet is rated, for example as 40Hz - 10 kHz +/-3 dB, one can get an idea of how much the power is likely to vary over the range of frequencies of interest.
     
  18. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    It's for "educational use." :D
     
  19. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Man, bad habits are hard to kill. Of course you're right! :)
     
  20. Marc Piane

    Marc Piane

    Jun 14, 2004
    Chicago
    Question. I found an Aguilar cab that I like but I was going to install this Eminence driver in my old Carvin cab just for kicks.

    Here's the question. The crossover is hardwired to the jacks. Can I just disconnect the tweeter, replace the 10" and still have it be 8 ohms? The Carvin driver that was in there was 8 ohm. Also is this going to limit the frequencies the 10" gets?
     

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