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too much power???

Discussion in 'Amps and Cabs [BG]' started by PhatBoi5, Dec 19, 2002.


  1. I have a problem. I just blew, for the third time, speakers that were in my SWR big foot 2x12 cab. I use a Carver pm1200 power amp (700w@4 ohms). I have blew up the stock bag ends, peavey black widows, and recently Eminence Kappa pro (400w). I am not a ignorant youngster that tries to out work the PA either. usually I have the pre amp (aguilar db659) at the equilavent of pre-gain=11 oclock, post gain=8. I run a hartke 2x15 with Eminence deltas(300w) and havent blown those ever??? any thoughts on why in the world this happens, moreover could you recommend a head doctor to examine my head as to why I keep dropping $100 a pop, twice a year on new speakers?
     
  2. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    most likely possibility is that your powere amp's wattage level is overstated and that you are clipping the power amp and blowing speakers that way
    other possibility is that you are truly overdriving the speakers and not noticing it
    i have more power than my speakers can handle so i have learned what levels will overdrive them and i always check out the sound for this when i play out (esp during the 1st few songs)
     

  3. I use two cabs both run @ 4 ohms. I did at very very small venues I would use only the one side with the 2x12.
     
  4. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    Speakers sometimes blow when they are pushed too hard with too much power in frequencies that they were not designed to handle.
    Are the speakers 12" that are constantly blown?
    If they are, you may be pushing the lows too hard.
    Some low frequencies (20hz-30hz) will pop small speakers if boosted too much and you may not even hear them.
    I have a dbx subharmonic synthesizer that creates a sound an octave below what I am playing (down to 21hz). You feel frequencies that low more than your hear them. It takes a good deal of movement of the speaker cone to produce frequencies that low. I have to be careful with it as it really tears up speakers. Several years ago in one of the first loud gigs I used it in I blew 2 15s. After that I started running a compressor/limiter after it to ensure the signal never gets above a certain level.
     
  5. When you say that you are blowing speakers, are you (a) melting the voice coils, or, (b) over extruding them and doing mechanical damage?

    PS. I have found that speaker damage and beer drinking go hand in hand. ;)
     

  6. Well the bag end tore the whole circumference of the cone. the black widow and the eminence both were voice coil issues.

    at least thats what I think.

    I press down on a certain part of the cone edge and the crackling reduces greatly. It only works if I touch the cone in a very specific area (about sqaure inch or less) while I hit any note.
     
  7. In this case you are clearly trying to make the speaker do more than it was designed to do. (stuffing 50lbs of sh!t into a 20lb bag) You need more and higher power capacity speakers. Have you considered an 8x10 cab? The power is spread out over 8 voice coils and cones, they are a lot more forgiving.
     
  8. i have thought about it but I do a lot of B and E string work and I didnt like any 8x10 I have played thru in a live setting (ampeg,peavey, and 6x10 SWR) 10s dont seem to produce the lower end thump I like. I just am partial to bigger speakers I guess.
     
  9. It sounds to me like you have the answer right there.
     
  10. its 300w on each speaker. and that isnt the one thats blowing
     
  11. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    PhatBoi5
    You posted that you do a lot of B and E string work and you like the lower end thump.

    It sounds like it may be the low frequencies that are poping your speakers. A low B is around 30Hz. Most 12" speakers that I have seen do not produce 30Hz very well. I think the Aguilar db659 has a Bass boost at 30hz and the Low knob is centered around 40hz - both could be out of the range of frequencies the 12" speakers are designed to produce. Check the specs of the speakers.

    You may try biamping and run your lows to something with an 18" speaker in it. Larger speakers tend to handle the lower frequencies better as they have a larger surface area. I use PA cabinets for my lows. There are several 1x18 cabs on the market that handle around 1000watts of power.

    If you are not running a compressor/limiter then that might be a start. There are used bass compressor pedals available for decent prices at www.musicgoround.com and on ebay. Eventually you will probably want a rack compressor with more options.
     
  12. the part that I dont understand is how can I do such damage when im not really pushing the amp to near its capable power? Are those low freq's doing THAT much damge even at low volumes
     
  13. geshel

    geshel

    Oct 2, 2001
    Seattle
    Yup. If the cab is tuned to a frequency higher than that (most likely, it is, tuned to 50Hz or something), then the cones are free to flap in the breeze at lower frequencies. You'd be amazed at how far cones move in free air at 30Hz with ten watts! Not many bass cabs on the market could handle a few hundred watts at 30-40Hz. Also realize that 10dB of bass boost means 10x more power at those frequencies - still, of course, within the amp's limits if it's not clipping. But A sturdy amp like yours could definitely dish out more LF than the Bigfoot could handle.

    The 2x15 might be tuned to a lower frequency, and have more cone control where your problem area is.

    I see on SWR's web page the new 2x12 (the 12-pack) is rated to 56Hz, and it's ported. Yeah, I wouldn't put much low-B into this cab. Dunno how similar the Bigfoot is. The current Hartke 215BXL is rated to 30Hz, and though I suspect that a bit, it's probably tuned quite a bit lower than the SWR.

    I really wish manufacturers would publish charts that show the power-handling versus freqeuncy of their cabs. It's bass, after all. . .
     
  14. geshel

    geshel

    Oct 2, 2001
    Seattle
    Hard to say. My assumption about the tuning of the Bigfoot is probably correct, but might be wrong. It'd be possible that it's tuned to say 40Hz and still has a -3dB point of 56Hz. BUT, :) with the Bag-End 15's yeah, I think they can handle a 4-string pretty well.

    I've been thinking though. . .even overpowering a speaker at low frequencies typically won't completely rip the speaker apart like that - I don't think. At least I haven't heard of that happening too much. Do you slap much, PhatBoi? The sharp impulses created by slapping the strings could be the culprit (they're lots of different frequencies combined together, but a lot of bass too). I could see 400w of spike causing a lot of stress on the cone.
     
  15. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    The DB659 Preamp may be working against you also.

    I found this link that describes the Preamp:
    http://www.spotlightmusicstore.com/aguilar/db659preamp.htm

    According to it, the deep switch adds +3DB at 30hz (which is probably below the cabs tuned freq) and the shelving low frequency is at 40hz (meaning it would boost at 40hz and below). So if you are are boosting the bass by using either the low knob or the deep switch then you are boosting frequencies below what your cabinet is designed for.
     
  16. Nick man

    Nick man

    Apr 7, 2002
    Tampa Bay
    Instead of constantly replacing your speakers, follow what Geshel said and get something that fits your sound and playing style better.

    Maybe get another Hartke 2-15". Im not sure if that'd be the best choice though, unless you only like bottom, and no top end.

    If you want some mids and highs, just bi-amp with the higher frequencies going to the SWR.

    Peace
    Nick
     
  17. I cant biamp with that preamp though. I really never thought about the freq range aspect since I plugged everything in and it was "my sound" tight but not boomy and not "10 inch speaker tight"
     
  18. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    If you want a Sub that will really shake the house check out the Servodrive Contrabass:

    Here are the Specs for the Servodrive Contrabass:
    http://www.mindspring.com/~sdinc/pages/contra_g_sp.html

    Note the following:
    Sound Pressure Level = 114dB at 16Hz at 200 Watts at 1 meter
    Frequency Response = 14 - 125Hz

    What else on the market can produce 114dB at 16Hz at 200Watts?

    There is one on sale on Ebay right now.
     
  19. Nick man

    Nick man

    Apr 7, 2002
    Tampa Bay
    There are tons of active crossovers that are on the market. Look in the proaudio section of any music store or catalougue to see what I mean.

    Peace
    Nick
     
  20. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    FYI there's a neat little device which might serve you well: a Rane DC-24 Dynamic Controller. Info here: http://www.rane.com/dc24.html

    To begin with, it's a dual compressor limiter. Each channel has both a compressor and a peak limiter (and also an expander, which is typically used as a noise gate). But the beauty of the device is that it also has a crossover.

    I use the DC-24 in mono split-band mode, in which highs and lows are compressed separately and then remixed into a full-range signal. However what might be useful to you is to use biamp mode: running the lows and highs separately, each band into its own amp channel and speaker.

    It's a versatile device, and pretty darn cool that you get crossover and stereo compressor/limiter/expander in one rack unit.

    [​IMG]