Relationship Between SPL, Wattage and Volume

Discussion in 'Amps and Cabs [BG]' started by Smallmouth_Bass, Apr 21, 2019.


  1. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    I don't know too much about amplifier and cabinet specifications beyond knowing how to calculate the Ohms an amp head can handle.

    What is the relationship between a cabinet's SPL rating, its wattage rating (RMS) and how much volume it can produce? For example, will two cabinets with the same RMS wattage rating put out the same volume when the SPL rating is different? Or do you need more "juice" to get a lower rated SPL to sound as loud as a higher rated SPL cab? And if so, will the RMS wattage rating limit restrict the overall volume it can produce?
     
  2. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yes.

    But counting on rating methods being consistent from manufacturer to manufacturer is not a particularly good plan, IMO and IME.
     
  3. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    When you say SPL, it depends if you're talking about it's sensitivity rating, or max SPL.

    RMS is usually the wattage that a driver can continuously sustain without frying itself.

    Sensitivity SPL is measured in decibels at 1 watt at 1 meter. It tells you how efficient a cab is.

    Max SPL is measured in decibels at the maximum power level that the cab can handle as a system, and tells you around what you can expect from the cab pushed to it's limits.

    It depends... there are so many variables to consider, especially mechanical limitations that may not necessarily match with RMS ratings.

    What cabs in particular are you comparing? This would be easier with examples. :)
     
    Last edited: Apr 21, 2019
    HolmeBass and Morrighan like this.
  4. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada

    Yes, SPL as a sensitivity rating. More like RMS than a max limit. I am more interested in what the cab/amp can reliably do continuosly and not a peak.
     
  5. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    I added a bit more to my post above - it can be complicated. If you give more details, or just examples to use, it might aid the discussion.
     
  6. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    I don't have specific examples. I was just asking the question for the sake of discussion and more for general circumstances.

    So, I assume higher SPL sensitivity ratings are considered a good thing? Or do cabs with lower SPL rating sound better when pushed harder than a higher rated cab pushed modestly? Or does it not make a difference; you do what you have to do to get the desired volume and ratings are just ratings?
     
  7. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, ChopShopAmps
    Often SPL is sacrificed to extend the low end. As well, vise versa.

    So sensitivity ratings sometimes can seem misleading if you dont know the tradeoffs about bass cabs. A higher SPL can mean it is thin in the low end.
     
    monsterthompson, Kro and Passinwind like this.
  8. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    Higher sensitivity is usually a good thing, but is also doesn't tell the whole story.

    Basically there are just a ton of tradeoffs, as @basscooker alluded to. Just one of the many reasons why finding the perfect amp/cab combination is such a difficult and personal decision.
     
    dralionux likes this.
  9. Unfortunately we are the minority less interested in the biggest number we can buy and more interested in what it can do.
     
    Morrighan likes this.
  10. There has been a bit of a shift in technology available to us. Overall that has given us some less sensitive cabs that can take vastly more power and turn it into more than a little bit more low end from a silly smaller box, at not inconsiderable expense to wallet.
     
    Luther, HolmeBass and Kro like this.
  11. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    So, SPL ratings do not take into account the frequency range that the cabinet is able to put out?
     
  12. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    So worth it. I couldn't care any less about how sensitive my cab is, at least not in and of itself. Watts are cheap these days.

    Being able to shave off over half the weight of my old cabs and still increase maximum performance and tone - that's a real achievement.
     
  13. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    I agree. I love having a manageable weight in a small package. Even if I don't entirely understand how they do it, my ears and back are thankful!
     
    BazzaBass likes this.
  14. That is one way some manufacturers can try to make you think their humdrum cab is some super duper thing. Other manufacturers quote mulitple frequency ranges of sensitivity that tell the savvy what they can expect.
     
    Kro likes this.
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    There are some serious misunderstandings going on here which contributes to the incorrect conclusions.

    Average sensitivity is the SPL or volume that a speaker produces with 1 watt of power input, measured at a distance 1 meter away, on axis.

    Maximum SPL is generally defined by the engineering community as the average sensitivity x the rated average power handling of the cabinet over a specified bandwidth and within a specified radiation space (usually 1/2-space).

    A problem arises when the marketing community changes the definitions used by the engineering community. Marketing liberties might include using the highest point in the response rather than averaging the response over a specified bandwidth, using "program power" or peak power instead of average or "RMS" power, or using 1/4-space instead of 1/2-space.

    All of these can result in erroneous conclusions based on misleading conditions.
     
  16. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    So the only way to realistically compare the specs of speaker cabinets is to ensure that they are based on the same definitions for their ratings?

    Of course, the best way to compare is listening to them in person!
     
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Correct.

    Agreed, this is always the best way because it allows you to see how the tonal profile of each cabinet relates to your own personal tastes and needs. The published specs do not describe in a generally usable way how the overall response (above say 250Hz) might appeal to personal taste and playing style. Everybody hears differently IME.
     
  18. Chad Michael

    Chad Michael Suspended Supporting Member

    Sep 19, 2001
    Pacific Northwest USA
    Two things come to mind, specs aside:

    - there is no substitute for a test drive, and I don't mean trying it out at Guitar Center, I mean using the cab at band practice, or on stage. This can be difficult to facilitate when considering a new cabinet

    - cabinet placement can make or break what you hear. The boundary effect will be alive and well, always. By this, I mean placing the cabinet on the floor, vs. on a stand, vs. near a corner of the room, or a wall
     
    Mingo Sanders likes this.
  19. Smallmouth, their is no enforced consumer regulations nor any industry 'gentleman's agreement' (HAH!) where say, when it comes to bass guitar cabinets (. . . . or most anything else in the industry), there are common tests and test methods that everyone performs, adheres to, and publishes. So without any published, common data, it's impossible on paper to compare the values you've questioned and compare apples to apples.

    I find that the smarter companies with legit products publish realistic test results (Andy's Mesa cabinets, Bag End, and Acme come to mind), as they are rightly proud of the performance of the goods they design and sell. Most others will tout any number of 'Brockmire'-inspired ad-speak that has little to do with how their products perform in the real world. And as Andy properly points out, all of the test results are empirical, versus how we subjectively hear them.

    But . . . . . it's a two way street: LOTS of guys could care less about this sort of thing, and buy based on brand name, looks, what Bubba told them, you name it. It takes a little educatin' to be able to have a grasp of SPL, power handling, speaker efficiency, etc., that just isn't on a lot of guys' radar to-do list. Read TB posts long enough, and we still get the questions about using a guitar cable for a speaker cable, guys wanting to do their own amp repairs who can't change a light bulb, and the 'why can't I hook up 4 2-ohm cabs to my XYZ head', and on and on.

    I will say that if you have a basic understanding of these things ( . . . . I barely get by but I'm learning), it tends to steer you to builders who will share this info so you can make better decisions.
     
    pglaser01 and agedhorse like this.
  20. Smallmouth_Bass

    Smallmouth_Bass

    Dec 29, 2005
    Canada
    I must be mostly checking out manufacturers that post honest and engineering based specs, because I often see SPL with listed with "1 watt of power input, measured at a distance 1 meter away, on axis.".

    When I can't find an RMS rating, I think to myself "what are they trying to hide?".
     
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