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Ohms my God! Rookie wattage question

Discussion in 'Amps and Cabs [BG]' started by neilshane, Jul 18, 2012.


  1. neilshane

    neilshane

    Sep 21, 2007
    St. Louis
    I have an Ampeg B1RE head. It's rated at 175 watts at 8 ohms or 300 watts at 4 ohms. I had previously been using an 8 ohm cab - the Ampeg SVT-15e, which is rated at 200 watts RMS.

    I've been playing in a loud garage band and wanted to up my output, so I traded my cab for an Ampeg SVT 410 HLF, a 4 ohm cab rated at 500 watts RMS.

    I get to practice thinking I won't even have to turn my amp up halfway but once we get going I notice there's no discernable loudness difference from my old cab.

    Am I doing something wrong here? Is there a button or switch on the head that I'm somehow missing? I've attached an image of the back of the B1RE.

    Thanks in advance and sorry for the noob question!
     

    Attached Files:

  2. john m

    john m Supporting Member

    Jan 15, 2006
    Get more speakers.
    2, 8 ohm speakers (or cabinets) = 4 ohms
     
  3. The HLF cabs go extremely low, at the expense of efficiency. You could try turning down the bass, and up the mids. This will give you more volume.
     
  4. neilshane

    neilshane

    Sep 21, 2007
    St. Louis
    I do have the bass turned down a lot or else it just gets overwhelming. I will try turning up the mids. I have the mid knob around 11 a.m. right now.
     
  5. JHAz

    JHAz

    Jun 29, 2011
    Nothing to adjust on a SS amp when you change to different impedance speakers. But critical to how loud a watt sounds is the sensitivity of the speaker. A speaker that is 3 dB more sensitive will be equally loud as another with half the power. Until you reach compression in the speakers double power is 3 dB - - about "one notch." Sounds like your new speaker may be less sensitive. It also may be that its different frequency response makes it seem less loud at the same SPL (our ears are more sensitive in the midrange and fall off pretty fast in the bass). Finally, (as far as things I can think of) the 410 will "beam" much more than the 115. Are you standing off to one side?
     
  6. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    As already mentioned, the 410HLF trades off sensitivity for an ability to provide extra low end. It's just as efficient as the 15e was so you're not getting any more (or less) volume per watt input than you did with the 15e.
     
  7. neilshane

    neilshane

    Sep 21, 2007
    St. Louis
    So in other words even by going to 300 watts at 4 ohms from 175 watts and 8 ohms I'm not gaining anything?

    The 15e is rated as such:
    Frequency Response (-3dB): 50Hz-3kHz
    Usable Low Frequency (-10dB): 33Hz
    Nominal Impedance: 8-Ohms
    Sensitivity: 98dB
    Maximum SPL: 123dB

    The 410 HLF is:
    Frequency Response (-3dB): 48Hz-18kHz
    Usable Low Frequency (-10dB): 28Hz
    Nominal Impedance: 4-Ohms
    Sensitivity: 98dB
    Maximum SPL: 125dB
     
  8. Not the first person to make that mistake.

    Plenty of threads over the years from guys wanting to switch from 8 ohm cabs to 4 ohm cabs so they could get every watt out of their amp, only to find out that there is not that big a difference.

    When trying to get louder, more speakers wins over more watts every time.
     
  9. CnB77

    CnB77

    Jan 7, 2011
    NJ
    The difference between 175 and 300 watts isn't as much as you'd want to believe.

    Speaker sensitivity is much more important than wattage: http://www.colomar.com/Shavano/spl.html

    More wattage is good, but without the right kind of speakers, it's negligible.
     
  10. will33

    will33

    May 22, 2006
    austin,tx
    While Ampeg is more honest than most with their ad specs, there still isn't much to be gleaned from those numbers.

    Freq. Response gives you the lowend and the highend with no mention of what's happening in between.

    SPL is an average. If the speakers response has a peak somewhere, that brings the average up and makes it look louder than it really is.

    Max SPL is calculated, not measured, and does not take into account things like thermal compression or excursion limits.

    Nothing is mentioned of excursion at all. That's how far the cone can move back and forth before it can't make any more bass. You most often run out of that before you reach the "wattage rating", which is really a measurement of how much heat the voice coil can dissipate continuously before it burns up.


    In short, the other folks here are giving you good advice. More, or higher spl, speakers get you louder than more power does. Yes, you need some power to make the speakers move, but after a couple hundred watts, the returns start to diminish fast.

    In your original situation, I'd have likely said, get a 2nd 8ohm 15e to stack with your first one. That would've given a good deal worth of volume capability increase.
     
  11. The old rule of thumb is that you have to double the power (watts) for each 3db of perceived volume increase, and 3db is not a lot.

    Both cabs have the same sensitivity, but the 410 cab should move more air than the single 15, because of the greater speaker area. It may not be a big difference, though. Your tone will probably have more to do with it.

    My recollection of playing through a similar rig with the same cabinet (backline provided at a gig) is that I had to roll off bass and increase mids, even with Barts in my bass (which have quite a bit of mid punch). You are on the right track with turning up your mids. IME that has a HUGE impact on how well you hear yourself, and how well you cut through the mix.
     
  12. You should be gaining some maximum volume, and more deep low end.
     
  13. Fliptrique

    Fliptrique

    Jul 22, 2002
    Szczecin, Poland
    Endorsing Artist: Mayones Guitars&Basses
    Try moving your cab around the rehersal space - the difference in overall tone can be REALLY big, and end up in perceived difference and volume.

    I do not like a lot of low end, so I avoid putting my cab up against a wall - otherwise it gets boomy really fast and ends up in me not hearing myself.

    If you play loud try to avoid standing really close to the drummer - his cymbals WILL kill you and damage your hearing.

    Try to avoid having any other amp directly facing you - this is the sole reason of 99% of the loudness wars in rock bands:

    - dude you`re to loud!
    - no! i can barely hear myself, you`re the one thats too loud!

    etc. etc.

    If you can try not to have your amp directly behind you. Having it a bit on the side helps A LOT.

    By doing some the above I can get away with playing in a LOUD band with my master volume set around 9 o`clock (650 watt head).
     
  14. neilshane

    neilshane

    Sep 21, 2007
    St. Louis
    Thanks a lot for all of these incredibly helpful responses. I wish I'd posted this before I traded my cab! In reality, I like the 410 a lot and I'm hoping that by trying a few of these strategies, like turning up the mids, I can increase my volume a bit.
     
  15. RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    Another option, if you were happy with the 15e, would be a 2nd identical SVT15e. 2 of them would net you a 6 dB increase over the 1 by itself. The 410hlf, while a very good cab, is much more low end focused, and thus, less loud.
     
  16. steve_rolfeca

    steve_rolfeca Supporting Member

    Uh, nope. At least not on the maximum volume.

    The OP and his 300-watt amp can only drive the 600-watt 410HLF to about half power. That would be 3dB down from max output (125dB according to neilshane, 124dB according to the Ampeg website), or about 121-122dB.

    Meanwhile, at 175 watts into 8 ohms, the same amp will drive the 200-watt 115E to within an inch of it's max output (123dB)- call it 122dB.

    That's a dead heat. More importantly, as other people have mentioned, voicing matters more than raw numbers, and the 410HLF is not a middy, cut-through-the-mix cab. The OP's experience to date makes perfect sense, both from a technical and a practical point of view.

    He'd do noticeably better with a pair of 8-ohm 115E's:

    1. With each 115E being driven by about 150 watts, they wouldn't be working as hard, and would last longer.

    2. With double the cone area at work, the stack would be 3dB louder than either the 1*15 or 4*10 rigs (equivalent to doubling his amplifier wattage).

    3. He'd also pick up about 3dB down low, due to coupling between the two cabs. So the E string would sound a little fatter, as well.

    3. The 2*15 stack is taller, so the sound would be closer to his ear, making it easier to hear himself.

    If he wants significantly more volume, these are really his only options: EQ around the 410HLF's voicing, trade for a 2*15 115E stack, get a bigger amp and/or more cabinets, or trade for some other 4*10, 6*10, 8*10 or 2*15 that's more efficient and has more zing in the mids.
     
  17. will33

    will33

    May 22, 2006
    austin,tx
    Good point too up there about how things are positioned in the room. Where speakers are in relation to walls affects the low frequencies a lot, so try setting things up differently and see if things improve or get worse.


    Due to the way the speakers are laid out, 410's are very directional. The upper half of your sound is hitting you in the knees instead of the ears. Can try stivking something under the front of the cab to tilt it back a bit. The same holds true for your guitarist if he plays a 412....even worse in that case. It leads to them cranking up to hear themselves and killing the guy on the other side of the room who is dead center on his speakers. Some room re-arranging can help there too to help keep the volume in check.

    When using stage rigs in a regular, smallish rehearsal room, you can get to a point where the volume just plain over-runs the room. At that point, turning up further only makes it harder to hear things, not easier. Those kind of volume levels also contribute to hearing damage. You only get one pair of ears, they have to last you the duration.
     

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