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Questions about cabinet stats

Discussion in 'Amps and Cabs [BG]' started by blubass, Aug 5, 2007.

  1. blubass


    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    I'm not clear on what everything means when reading the stats. These are the stats of a GK goldline cab, i'm using this just as a reference.

    4 ohms
    800 watts RMS (What does RMS mean? what's the difference between this and something like program handling?)
    55Hz to 5kHz (-3dB) (Why on the frequency response does it say -3dB?)
    128dB max SPL

    Any info would be greatly appreciated, thanks!
  2. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Forget for the most part any bass cab manufacturer's published specs. Those companies who actually don't let their marketing departments create cab specs from thin air tend to use different non-standard measuement practices which make comparison across brands and even product lines from the same company suspect - and some of the specs don't mean much anyway until put into a bass guitar context.

    Getting the specs on the drivers is more likely to aid you, but hearing or trial periods is really the way to go.
  3. pablomigraine

    pablomigraine Commercial User

    Feb 9, 2005
    New York
    VP & Managing Director - Willcox Basses
    First off, the figures are overstated / inaccurate in almost all cases. Notabel exceptions are BERGANTINO, ASHDOWN, AGUILAR ..... and yep thats about it.

    RMS: This is the minimum wattage the cabinet can tolerate continuously. Peak power or "program" power is the wattage the cab will tolerate in short bursts. Now again, amp makers tend to wildly overstate the wattage of their amps, so my rule of thumb is: Consider Amplifier "RMS" to be "Peak" when matching amps to cabs. In other words: if a speaker cabinet states it takes 500 watts RMS and 800 watts Peak, you can safely use an amplifier rated at 800 watts RMS.

    -3db: Frequency response is the "bragging rights" of speaker cabinets. First off you must understand that upping the volume on anything ( amp, television, whatever ) by 3db or decibels literally DOUBLES the volume, and reducing it by 3db cuts it in half. Cabinet makers state their freq. response at -3db in order to state a wider response and make the consumer think that the cabinet "goes deeper" than it actually will in any real world situation. Some makers will even state their response at -10db!!! That means that the frequency at that level is nearly inaudible!
  4. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Highly doubtable, if I'm being diplomatic. And where it gets really laughable is you could get a whole bunch of lists from different people about which companies are accurate and using the same measurement standards.

    The minimum wattage any cab can "tolerate" continuously is none, nada, zip, zero. All day long even. Even for a month. A year. Ad nausem.

    Reputable power amp manufacturers are pretty good about using standard measurement methods and can be counted on to deliver something akin to what is stated. Bass heads and combo power sections however tend to seem a little less nailed down by actual AES guidelines and qualifications, and often seem circumspect. Look for a complete spec and not just a wattage figure that has not been qualified.

    Usually, AND THIS IS FOR CABS AND NOT FOR AMPS, program is 3dB above RMS, and peak is maybe 3dB above that. But unless the manufacturer quantifies their methods, you can't be sure what conditions they consider relevant and it just as well may be marketing chuff.

    It gets more complicated than that unfortunately, with bass frequencies and driver excursion entering into it. Fortunately choosing cab/amp combinations doesn't require perfect match up anyway, but only requires ears and intelligent use of gain structure knobs.

    Oh so wrong. This is another place where misunderstanding specs can make their use either useless or damaging. 3 dB is a noticeable but not largely so difference in percieved acoustic volume, nowhere near TEN dB, which is generally accepted as doubling or halving.

    Wrong. Reputable cab manufacturers actually use PLUS/MINUS 3 dB as a set of boundaries that say defines a frame or window, and the Hz figures listed with that tells you what range falls within that window. If they used a window of +/- ONE dB they would not even be able to show you an octave of response in many or most cases. A +/- 1 dB qualification would be useless. To be real-world useful a window of +/- 3 dB is actually pretty decent for anyone who understands audio and physical environments it takes place in.

    And actually, the way cab manufacturers can make their wares seem better is just to NOT state any qualifications of +/- whatever dB AT ALL, or use measurements at a certain frequency that has little bearing on actual intended use, or do their measurments in a corner or against a wall with the tweeter turned all the way up, or just flat out make their figures up (which some must be doing, because they are way beyond the bounds of physics).

    Wrong. As explained above, 10 dB is usually percieved as half or double the volume. And when expressed properly we would be talking about PLUS/MINUS 10 dB, which is a window of TWENTY dB, which by the way is not related in particular to anything INAUDIBLE. If it was, you wouldn't be able to hear a cab that can handle 100 watts when only 1 watt was put into it.

    Your post is a primer on why specs are dangerous, and where you bolded things immediately drew attention to some real whoppers ; }
  5. blubass


    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    thanks for the info everyone.... i see some difference in opinions on what things mean, but that seems to be a good thing on TB. I always use my ears as a judge, but i just never understood what those things mean. I run over them constantly and like anything you see over and over in your hobby/job, you start to feel like you need to learn a bit more! thanks again everyone.
  6. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Well. I guess it's good it was just about dB and stuff, because if the opinions were so varied about what it takes to safely rig a flying PA system, there'd be a lot of dead people on the arena floor ; }

    I suggest that if you remain genuinely interested you consider your sources. If nothing else, pro audio forums are more likely to have the real info and not just some misunderstood mangling. Better yet, look at some books by widely-accepted experts.
  7. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    This is correct! Everything below is incorrect:

    So all that quoted above should not be taken as accurate advice. However, this is true:

    I'm starting to think that we need some kind of 'talkbass amp forum technical certification' to help separate the wheat from the chaff when it comes to technical matters! ;)

  8. TFunkadelic


    Apr 9, 2006
    Actually, an increase in 3db in volume requires double the amplifier power, and double the driver excursion. This will yield double the amount of sound energy. The 10db figure of "perceived doubling or halving" has always seemed to be a pretty random and bogus figure to me.

    What's with your attitude man? Even if you were right, there's no need for it.
  9. Geoff St. Germaine

    Geoff St. Germaine Commercial User

    A guy over on AVS Forum in the DIY Speakers and Subwoofers section is testing out a bunch of HT and pro amps to see if they meet the published specs. So far he's done a Buttkicker and the Behringer EP2500 and EP1500. The Buttkicker was pitiful (although it isn't really intended for speakers) and the Behringers were actually very close to their published specs (I think 85-90%).
  10. Geoff St. Germaine

    Geoff St. Germaine Commercial User

    No, it's based on the way the human hearing works. Human hearing isn't linear, it is logarithmic.

    I didn't see anything wrong with his post given the person coming in was attempting to speak as an expert and yet had a lot of misinformation.
  11. TFunkadelic


    Apr 9, 2006


    Human hearing isn't logarithmic. Do you understand what the word logarithm means?
  12. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Says the turkey with more attitude yet ; }

    There's certainly more correlation with 10 dB being twice as loud as there is with 3 dB being twice as loud. Considerably. Just because excursion or wattage are double at 3 dB doesn't mean anything about perceived volume. How is one case the same as the other? 3 dB and 10 dB are worlds apart.

    You can look up studies and history on this BTW. Or you can conduct an experiment with a mixer or power amp that is calibrated to dB. Just run some broadband program material through and change the gain 3 dB. Perceptible, but harldy even suggestive of being twice as loud. Some people even consider it to be rather slight. Then do 10 dB. Given losses via driver compression etc, that's still a change to be reckoned with, and most people will agree that's a lot closer than 3 dB change was to doubling or halving what they heard.
  13. Geoff St. Germaine

    Geoff St. Germaine Commercial User

    Certainly, perhaps you don't. You can try to explain it though.

    10 dB is generally accepted to constitute a doubling of the perceived volume. Since this 10 dB would equate to 10 times the sound intensity (10*log(P2/P1), which turns out to be 10 for P2/P1 = 10 since log(10)=1 by definition). Our hearing is proportional to the logarithm of the intensity. Here's another scientist to explain it:

    and another:
  14. TFunkadelic


    Apr 9, 2006
    I'm not arguing that 10db is not considerably louder than 3db in terms of difference. I have equipment that measures in decibels.

    I'm saying that since double or half of a given loudness is subjective to human ears, which are not accurate at all. Because of this, the 3db measurement is practical and tells you a bit about what will be going on in a speaker or amplifier at a given power output level.

    The reason most people will say 10db sounds closer to double the sound pressure level than a 3db increase or decrease is because most people don't know anything about sound reproduction.
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    RMS is the best way to rate both amps and speakers, as it puts all the players on the same field as to how it's calculated. Other terms such as Peak and Program Power are attempts to overinflate figures.

    the -3dB frequency is the half-power point, and gives the most accurate and useful information for comparative purposes. Most manufacturers don't tell you what their supposed low frequency figures refer to. This rating appears to be a reasonably honest one for an 8x10.

    Usually arrived at by adding to the base sensitivity the additional dBs that a full power signal would produce, which assumes that power and output are linear, and unfortunately that's impossible to achieve. For instance, 1000 watts is a theoretical increase of 30dB, so 30 dB added to a base sensitivity of 98dB/watt would equal 128dB. However, the average speaker will at best only work in a more or less linear fashion to perhaps 30% of rated power, and virtually none will put out any more sound at full power than they will at half power.
    It is, and I do.

    A 3dB increase in output does require a doubling of power, but this does not correspond to a doubled excursion. A doubling of excursion occurs with a doubling of voltage, and a doubling of voltage results in a four-fold power increase, ie., 6dB.
    It's neither random nor bogus, and was scientifically quantified at least a half century before you were born.
  16. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Geoff, how's the weather treatin' ya? Read any good books? Gone weasel hunting lately?
  17. pfschim

    pfschim Just a Skeleton with a Jazz bass

    Apr 26, 2006
    SF Bay Area
    FWIW .... literally, RMS stands for Root Mean Square or the square root of the arithmetic mean (average) of the square's set of values. A reasonably accurate method of describing an amplifier's power output.

    I'm just sayin' :cool:

  18. blubass


    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    thanks again for the info, from now on i'll try to keep the questions a little less controversial. So how many strings do basses have? :D

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