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My 15 Can't Handle It...Ideas??

Discussion in 'Amps and Cabs [BG]' started by Freakin Idiot, Aug 19, 2005.


  1. I recently got my M-Pulse 360 and the semi parametric eq is a dream. It's awesome. But my 15 inch Son of Bertha can't handle it. Not only does it clip, but it slaps the back of the grill. Now if you're standing there looking at it is sort of scary to see it move that much. I am running my 360 at 4 ohms with the Goliath III hooked up also.

    What should I do? I like the added bass of a 15 and I want something that can handle my Mesa. Should I replace the speaker, the entire speaker/cab, or just go with an 18?

    My Mesa screams with my current settings on the semi parametric eq. I'm clipping my 15 at barely above 1/4 master. Now I know how to use my eq very well and didn't go crazy just boosting stuff. I don't want to change any settings. You guys got any ideas?

    I guess I could consider getting something like a 2x15 + 2x10 setup, but I bought my 4x10 not too long ago. Would Mesa 15s kick about the same as my SWR? If I decided to sell my rig, what would be a good price, seeing as the Son of Bertha is a year old...

    Thanks in advance.
     
  2. xb100

    xb100

    Mar 24, 2004
    NH, In
    That kind of sucks dude, I'd take the SOB back where you baught it, it should still be under warrenty, and if your mesa puts out 360watts into 4ohms, your SOB shouldn't be thumping like that.

    I know bag end makes great 1x15 cabs, maybe you could check them out. I think if you sold your SOB you would have enough to get one of bag end's s15d's they are the 1x15 with out the tweeter (red thingy) I got a quote for em for 370.

    Hope ya figure something out dude!


    -Rob
     
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Can I ask what frequencies you're boosting with the parametric EQ?
     
  4. I'm boosting 80, 200, 700, 4k, 6k. This adds some punch along with nice bottom end with a little bit thicker treble.

    I have the bass blend at 3:30, mid at 12:00, and treble at 1:00.

    Basically, it's a very warm/tubey slap tone for Blue Steel strings on EMG Hz pickups. Makes my $500 bass sound like something $1200.
     
  5. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I see two problems here, namely the boosting of 80Hz, and also the boosting of the Bass knob. At a guess I'd say the centre frequency of that knob is somewhere near 40Hz (as it is on my amp).

    Put simply, you'r asking for too much lows from not enough speakers. An 18 would help but I'd be more inclined to add a second 15. Both will produce more bottom end naturally but with twice as many speakers, you'll be putting less strain on the speakers suspension system.
     
  6. So you're saying that if I got a 2x15, the speaker travel of each speaker would be less? And what about the 18? I've read tons of posts about 18 inch overkill, but then I could tun down my bass knob...
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    That's exactly right. Each speaker recieves half the wattage, so the speaker movement is halved. Lets assume you 15 has an X-max of say 5mm. Your current setup has the speaker moving more than 5mm. Getting two 15's effectively doubles the available suspension travel. Each speaker still has a 5mm X-max, but with the wattage split between 2 speakers, at the equivalent SPL, each speaker only moves half as far. Hence you can now puch that little bit harder. But that's part of the equation.

    Adding a second speaker usually decreases the nominal impedance and provided you amp can handle it, results in more watts being genereted.

    Furthermore, the two speakers sill acoustically couple in the low frequencies, so the low frquencies from one speaker effectively reinforces the lows from the other, resulting in an increase in bottom end and a greater overall system efficiency.

    So if the nominal impedance thing checks out, adding a second speaker gets you more speaker cone movement, more watts, and more lows. You'll probably find you don't have to boost lows as much (if at all) and you won't have to push your amp as hard to get the equivalent SPL. Switching to an 18, will certainly give you more lows, but may or may not provide the other benefits mentioned.

    Just my 2c, but it's based on what I believe is the sound that you're chasing.
     
  8. That said, any ideas about a 2x15 that won't break my bank? My birthday isn't far off and if I can get $320 for my SOB I'd be all set. I wish SWR still made the Big Bertha :crying:
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Before you rush out and buy anything, what's the nominal impedance of your cab? And what the minimum ohms rating of your amp?
     
  10. Suggested 4 ohms, 2 ohm minimum. A power amp isn't too far down the road for me, say a QSC RMX850 (830 watts bridged).
     
  11. bill h

    bill h

    Aug 31, 2002
    small town MN
    Compressor
     
  12. I have a compressor with a ratio knob built into my amp. Granted it's still better than a limiter, I lose the punch.
     
  13. Here is what I see when looking at your cabinet from the Internet:

    The 80Hz is the sore spot. Here's why:

    The cab is very likely tuned around 40 Hz. Vented boxes have a double resonance point, one above and one below the tuning point. Cone excursion is maximum at these two points. These are typically found (drum roll please)... about 1 octave away from the tuning point.

    This puts the maximum cone excursion right around 80 Hz. The EQ is making it even worse, by boosting response at this range. The problem is self correcting though, as a short amount of operation with the cone hitting the grille will soon cure itself. Cone movement will be minimal after that. Very minimal.

    :D
     
  14. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    .

    What about the nominal impedance of the cab?
     
  15. Cab is rated at 8 ohms.
     
  16. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    In that case I can't see any reason not to get a second 15" cab. You'll want them to blend in with each other. Make sure the second cab is also 8 ohms to esure each speaker gets the same number of watts. And if possible get something which has a similar sensitivity rating to the existing cab.
     
  17. Read and re-read this post a few times. First of all adding another 15 to your rig isn't the answer. It's all about how the cab is tuned. You are throwing way too much low end at your cabs. The next time you jam with your band start with your EQ flat and adjust as required. That EQ curve probably is slammin' alone in your bedroom but as you add volume to keep up with the band you are damaging your rig. Fill in the holes in your bands sound don't make them. Or you could just ignore bgavin's post and fry your cab. End of story.

    Jeff
     
  18. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Zoomboy, that's pretty darn rude. Go back and read, then re-read all the posts in this thread, particularly FI's. Is FI complaining about lack of articulation or cut? Nope! He likes bottom end, so lets give it to him without getting the speakers to exceed X-max. Whatever your thoughts are on equalisation are, the bottom line is that the 1x15 isn't producing the amount of bottom end required. He has 2 choices, namely more speakers, and/or bigger speakers. Each has it's pros and cons and we've covered those already. This isn't my opinion, it's the laws of physics at work, and they don't change for anyone.
     
  19. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Yep.
     
  20. I just got an old peavey 215D with BW's for £75 :D , i cant complain about that, its really sweet sounding, the only thing ive found it doesnt like is too much overdrive, but thats fair enough i supose, still, for that price i can hardly complain ;)