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15" Cab Power Rating Question

Discussion in 'Amps and Cabs [BG]' started by jbalou02, May 9, 2010.


  1. jbalou02

    jbalou02

    Mar 8, 2010
    I've been playing a Hartke 5500 and 410xl, and in the new band I'm in, the sound guy has been loaning me a home made 15" cab to run under it. It really helps the sound on stage a ton!

    I don't expect to be able to or want to have to rely on borrowing this 1-15" cab forever, so I'm going to get my own...but I'm not very knowledgeable about power ratings. The 5500 is 500 watts and has 2 - 8 ohm speaker outs on it. The 115xl 1-15" cab has a power handling of 200 watts @ 8 ohms. Am I gonna push that too hard, or is the 410xl going to suck some of the 500 watts? I just don't know the mechanics of this stuff...can anyone give me some tips? Thanks!
     
  2. babebambi

    babebambi

    Jan 7, 2008
    YTZ
    if you can't but that exact same 15" cab which you used and like, then just pair it with another 410xl - using identical cab is the rule of thumb here
     
  3. jbalou02

    jbalou02

    Mar 8, 2010
    Thanks babe, but I guess I'm looking for a bit more than just a "don't ask why just do it" answer.

    I know a lot of people here run 4x10's and a 1x15, or 2x10's and 2x15's or 8x10's like you suggest. I have no clue why. All I know is I like the low end that 15" pulls, I mean I can feel it. Will I get that from another 4x10 cab? Plus, the 1x15 is going to save me a couple hundred bucks...
     
  4. babebambi

    babebambi

    Jan 7, 2008
    YTZ
    No problem, I am glad that you are asking what's actually on your mind.

    Before we get on with your questions, I actually have a few of my own.

    You mentioned you can feel the imcreased low end that the 15" produce. Is that together with the 410 or alone? Have you try to A/B the two cabs individually?

    More cabs usually mean louder, and human ear interpret louder as better, usually. Also, often a lack of mid and high, could give an impression of more perceived low end. Not saying that must be the case, but hard to be sure unless measured by meters.

    The way speakers work is funny like that, if they do not reinforce each other, they cancel each other. And in order for speakers to be able to reinforce each other, they have to work in perfect unison. Rarely will two cabinet of different design work in perfect unison.

    Unless you actually compare a rig of 2x 410 and a rig of 410 &115, there is no way to be sure which one actually works better, for you.

    In the end, my suggestion of 2x the same speaker cab is just a safer bet. May be you like the tonal oddity that "mis-matched" speaker give you. After all, what you described as "more low end" may not be my idea of the description on paper.
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The fact of the matter is that running almost any two cabs together will sound better than either one on its own. There's nothing the least bit magical about using a 4x10 and 1x15; it's actually a mis-match. A 2x10 and 1x15 is a better combination.
    You'll probably get more. The commonly made assumption is that because it uses a larger driver a 1x15 goes lower than a 4x10. That assumption is incorrect; the size of the driver has little bearing on how low it goes. In the vast majority of cases a 4x10 will go just as low as a 1x15, and it will go louder as well. The best addition to a 4x10 is usually another 4x10. If you want something that can give more than what another 4x10 will that would be a 2x15, not a 1x15.
     
  6. Ha ha. Don't anyone answer the question. Just tell him to buy more 10s. Ignore the fact that he likes the sound of the 15.
     
  7. jbalou02

    jbalou02

    Mar 8, 2010
    Thanks for your input all. I'd like to follow up with babe's post, which might help narrow the scope of my question:

    This is together. I have run the 410 alone many times, and with the home made 1x15" a number of times. Occasionally during a performance with this new band the cord to the 1-15" jack will vibrate itself out, so I have a solid "Only A" to "A+B" comparison, but no "Only B". There is a noticeable lack of low end "fullness" on stage between the A vs. A+B. I would guess that would be the case with "Only B" but I can't verify that.

    A+B definitely was louder than A alone at the same amp volume, but more so missing from A alone was a fullness that I could not get from just turning up the amp.

    I have no basis to comment on if they are working in perfect unison, but they definitely aren't canceling each other out. There was a tangible beneficial result from the addition of the second cabinet.

    I won't have this opportunity. It's going to have to be an untested purchase.

    I'm not sure I have an experienced enough ear to distinguish "tonal oddity". I just know it sounds and feels better with the 1x15" there.

    So, what I'm going to do is get the best deal I can on whatever I can get between a 4x10 or a 1x15 (or a 2x15 - which sounds extra evil :ninja:).

    This gets me to my real question I guess. Again, I have a Hartke 5500, which puts out 500w at 4 ohms, but only has 2x 8ohm speaker outputs. One will always be running the 410xl, which is rated to 400W @ 8ohms. What power rating should I be getting for the second cab? If anyone can give me actual numbers, that would be helpful. I'd be interested in what rating I should be looking for for a 4x10, 1x15 and a 2x15.
     
  8. babebambi

    babebambi

    Jan 7, 2008
    YTZ
    It's not entire accurate to call the amp's speaker output jacks as 2x 8 ohm. Those jacks are wired in parallel and will operate down to the rated minimum impedance of the amp (which is 500W at 4 ohm) in various different fashion; you can reach the minimum impedance by just plunging in one 4 ohm cab, or plugging in two 8 ohm cabs.

    If you are using two 8 ohm cabs, each cab will get half the power. So for the second 8 ohm cab, anything that can handle more than 250W should be fine.

    With that said, you have to understand the rating you see on the cab is thermal capacity of the voice coil. Most cab is displacement limited (at low frequency) to quite a bit less than the thermal rating.

    Add on top of that, cab manufacturer tend to be optimistic about their specs.

    So if you ask me, I will get a second cab that handles the same amount of power as your first one.
     
  9. I agree fully with Bill's comment on the two cabinets but why not try running the 4X10 on top of the 1x15 but not plug the 1x15 in. The difference could partially be having the 4x10 closer to your ears and thus being able to hear yourself better.

    Paul
     
  10. Alex1984

    Alex1984

    Jan 16, 2010
    Vancouver
    I believe the OP has tried that, in the scenario where the 1/4" jack rattled out.

    To the OP: like someone has mentioned already, anything 8 ohm cab that can handle 250W should be okay.

    On a side note, a few questions for Bill:
    Someone mentioned speakers working in unison, that is determined by the phase, right? Is 180 degrees phase when the speakers are connected in opposite polarity? Is it possible for speakers to be out of phase by any other amounts?
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    It is. All speakers have a characteristic phase response, and that phase varies throughout their bandwidths. When you mix two speakers in the same bandwidth their differing phase responses will result in their augmenting each other at some frequencies, detracting from each other at other frequencies.
     
  12. jbalou02

    jbalou02

    Mar 8, 2010
    Thanks. From you all and others, I'm learning a ton, and I think I've got the math down...which was the original intent of my question, I just didn't pose it very clearly.

    I took another look at my head. It puts out 333W@8ohms. So since I have the 410xl, which is rated 400W@8ohms, if I'm understanding right, with a second 8ohm cab, I'll be pushing 166W to each cab. Thus, if I go with a 115xl which is rated for 200W@8ohms, I shouldn't be pushing either cab too hard. I think this will do. I don't necessarily want to outdo the 410xl, just enhance it, replicate what I already have experienced as a good mix. I just wanted to make sure I didn't blow the head or the cab up doing it.
     
  13. Alex1984

    Alex1984

    Jan 16, 2010
    Vancouver
    Just one thing, the jacks are wired in parallel, and EACH cab is 8 ohms. 2 x 8 ohms in parallel will result in a equivalent impedance of 4 ohms. Your head pushes 500W @ 4 ohms, so it will be supplying around 250W per cabinet.

    To calculate the effective impedance of cabs wired in parallel, use the formula 1/Z1 + 1/Z2 + ... + 1/Zn = 1/Z effective. So in this case, it's 1/8 + 1/8 = 2/8 = 1/4, so it's effectively a 4 ohm load. Something like that...

    Think of it like pumping water through pipes: if you have 2 pipes of the same size, as long as you got enough water pressure to keep pushing the water down, you get more flow than with just a single pipe. In this case, the voltage drop across the terminals is analogous to the water pressure, the current is the water flow, and the impedance of the speakers are like the resistance to the flow.

    If you introduced a cab with a different impedance, it will end up being like adding a different-sized pipe, and the flow will not longer be distributed exactly 50/50 between the 2. Also keep in mind, speakers are not passive components, and the impedance is different across the spectrum, just something else to keep in mind.
     

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