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Sensitivity and SPL

Discussion in 'Amps and Cabs [BG]' started by Stride000, Apr 12, 2006.

  1. Stride000


    Mar 15, 2006
    Hi there,

    Just want to have your opinions on both.

    Manufacturers rave about their cabs sensitivity but not much so on their SPL.

    Now if we look at companies that build great cabinets, their sensitivity si around 104 - 106 dB

    But what is a good SPL??

    I have compared soundwise my BXT-410 wich has a sensitivity of 99dB and SPL of 127dB to an Eden 610XLT that has a sensitivity of 107dB but no info on the SPL.

    The 610 was more responsive and had more punch and didn't test to try and overdrive the drivers but I guess it has a higher SPL than the Ampeg.

    So, once again, what is considered to be a good SPL?

  2. From my layman's understanding, SPL is the measurement unit of sensitivity.. hence they are the same thing. A higher SPL means more sensitivity.

    Also, high sensitivity (i.e., SPL) does not indicate quality or good sound necessarily... it just indicates the 'loudness per watt'. This 'loudness per watt' can be influenced by the frequency at which the measurement was taken, how the measurement was taken (mic placement, etc.). It also can mean that the cab is tuned very high, so that the lack of bass response results in the cab putting out a lot of volume per watt.

    So, the published SPL's should be used as, at most, a general guideline.

    However, I don't find them useless... I do find, in general, given the same input, a cab with an SPL of 96 or 99 is not as loud as a cab with an SPL of 102 or 104.

    Finally, a low SPL can actually be a good indication of a lot of low end extension, since those low fequencies take a lot of watts to reproduce. For example, the Acme cabs have very low SPL ratings because they are designed to produce a lot of low end from a small cabinet... which means... they need a lot of watts, which equates to low SPL.

    My aplogies to the EE TBers, this is definitely a layman's understanding, but I think I'm at least in the ballpark of being correct.

    To answer your specific question... I've found most medium and large cabs have adequate SPL to be driven to very loud levels by around 500 watts... so, it seems most of the popular cabs (Epifani310 and 410UL, Eden410XLT and XST, SWR GoliathIII, Schroeder 410 and 21012, Aguilar410, etc.) all put out similar volume per watt in my experience (and most have SPL ratings between 102 and 104). A little bit less efficient are the Bergantino's and Accugroove stuff, which seem to sound better with higher wattage amps (and seem to have SPL's in the 99-100 range). Finally, the Acme's (and the older EAVL's) need much more wattage to achieve the same volume as the cabs above, but will also put our more low end for their size (and have SPL's listed between 96-99 or so, from my memory anyway). Of course, in general, smaller cabs (110, 210, 112) will have lower SPL than larger cabs.
  3. Stride000


    Mar 15, 2006
    Ok, I guess what threw me off is that the Ampeg sites seems to take both as two seperate things because if you look at the specs it's like:

    Frequency response (-3db): 45hz - 18 hz
    Maximum SPL: 127 dB
    Sensitivity: 99 dB

    So if I understand what your saying Kjung, this cab is less powerful than the Eden ones at 104 dB (hence maybe the relation between their power rating of 600W for the Ampeg against 700W for the Eden 410) and is less efficient in the low range then any other cab who would have a SPL less than 127 db?
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    It doesn't mean a thing if the rating is not given as a curve of sensitivity versus frequency. Otherwise, you have to assume that the value is taken at the most favorable frequency.
  5. I think 'maximum' SPL is a different and relatively useless term.... I think it represents the maximum sound the cab can produce when run at full volume with maximum wattage. However... I'm not sure what that means.

    I know a lot of the more techy guys think the sensitivity ratings are useless, and I understand the variance in measurement, and the imprecision regarding the volume throughout the entire range from bass to treble....

    However... I've found the sensitivity/SPL ratings (not the maximum SPL) to be relatively highly correlated with the volume achieved across a reasonable spectrum of the range of the bass guitar. IN other words, a cab like the Eden rated at 104 SPL probably will sound 'louder' with the same amp and setting as the other cab rated with an SPL of 99.

    Definitely ignore that 'maximum SPL' figure though IMO
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The three greatest lies:
    1. "The check's in the mail."
    2. "Of course I'll respecy you in the morning."
    3. "This speaker has 104dB sensitivity."
  7. As I said... the techy guys scoff... however, it's amazing how virtually every time, a cab with a published SPL of 103 is louder on the gig with the same amp as a cab with a published SPL of 99.

    As an exact measurement.... I'm sure it's useless. As a relative measure, and one of many things you should look at when buying a cab, it seems to have at least some validity in my experience with the many cabs I've purchased over the years, especially if you plan to use a 'non lead sled' amp of modest wattage.
  8. yamaha


    Apr 7, 2006
    Wow, your question is so cool, I actually asked myself the exact same thing last week while shopping for Eden vs SWR cabs, and this is what I found when I looked it up.

    1st, SPL is sound pressure level, or for everyone's understanding, quantity of decibels, volume.

    2nd, Sensivity is the number of decibels produced by the speakers when a 1 watt input is given, and is measured at 1 meter in front of the speakers.

    3rd, Max SPL is as loud as the speaker will go, very probably at max. cabinet wattage.

    4th, As wattage is doubled, decibels increase by 3dB, so a cab with 100dB sensitivity (ie 100dB at 1 watt), will give you 103dB at 2 watts, 106dB at 4 watts, 109dB at 8 watt, 112dB at 16 watts, 115dB at 32 watts, 118dB at 64 watts, 121dB at 128 watts, 124dB at 256watts, 127dB at 512 watts, etc....

    5th, Resistance (ohms) and frequency will change the SPL.

    6th, This adresses sensivity and max SPL, there is also efficiency and frequency witch will change the volume of the cab, depending where you put it, and where you are.

    So I guess sensivity is a good place to start, but nothing will test your cabinets like brigning your head into the store and A-B ing the two cabs side by side.
  9. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The reputable makers probably do their best to publish a believable sensitivity rating. Just dinking around with WinISD, I have noticed that a favorable frequency for rating many speaker designs is the tippy top of the midrange hump. And if that hump is in the right place, it might make the speaker sound pretty loud.

    I am not so much scoffing as asking for more comprehensive data. It would be really cool for a third party to measure some popular bass cabs.
  10. seamonkey


    Aug 6, 2004
    Should that be "This non-horn loaded speaker has 104db sensitivity"?
  11. Nice explanation!
  12. Stride000


    Mar 15, 2006
    Yamaha, you nailed it i think, or is it just too much merlot? lol

    Seriously, by reading all you guys responses, why do compnies keep posting all the specs instead of simply writing: "go to your local retailer and give this cab a run. it's loud and you'll love the sound. if not, you can always try some other line of our fine products 'till your ear is satisfied."

    A little utopic but hey.
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Not necessarily, but sensitivity quotes that aren't referenced to frequency are about as useful as mammary glands on a male bovine. Of one thing you can be sure, any direct radiating speaker that does quote 104dB sensitivity is doing so above 100Hz, and since 75% of the power requirement for electric bass lies below 100Hz it's a pretty specious spec.
  14. I'll again make the point that while these sensitivity figures are probably measured at a specific and relatively high frequency, I've again found them very accurate in a relative sense.... it seems that many cab companies are 'fudging' these figures in the same way. So, again, from my DIRECT EXPERIENCE, the published SPL ratings of similarly configured cabs (i.e., 410's vs. 410', etc.) or similarly sized (i.e., a large 2x12 versus a large 410) can be used as at least one of the pieces of information to evaluate a cab... both in terms of its loudness per watt, and also the relative low end extension of the cab.... i.e, the very low SPL Acme cabs need much more power than a typical cab to come up to similar total volume, but they will do it with more booty below 50 hz, compared to the Eden or Epifani cabs... with the Berg's and Accugrooves falling in the middle of pack regarding volume per watt and more toward the Acme (but not nearly as extreme) regarding low end extension.

    Relative comparisons can be very useful, even if the absolute value of the measurement is suspect.
  15. seamonkey


    Aug 6, 2004
    I agree, and some manufacturers are actually honest.
    I like to see published specs.
    If a manufacturer does fudge the specs, you know another make will call them on it, or these boards will point them out.
  16. Dudaronamous

    Dudaronamous Supporting Member Supporting Member

    Oct 16, 2005
    Bothell, WA
    I recently bought a Schroeder 1212Light, brought it home, and A/B'd vs. my SWR Bigfoot 2x12. I plugged both cabs into my iAMP800 simultaneously, expecting the Schroeder to be louder. I was surprised that my ears perceived the SWR to be louder than the Schroeder. The SWR sounds more "bassy" or "boomy", but nonetheless, it does sound "louder" than the Schroeder. Any thoughts on this? Since it has a higher sensitivity, I really expected the Schroeder to be much louder than the SWR, but the opposite is true.

    Here's the ratings: Schroeder website rating: "102db SPL @ 1W/1M"; The SWR manual states: "Frequency Response & SPL: 95 dB SPL @ 1W1M (-3db @ 40Hz and 15KHz)".

  17. Interesting... most SWR cabs are very efficient and very loud per watt (the 410GIII has a published SPL of 105DB). That 95DB is among the lowest SPL ratings I've ever seen for a large cab.... are you sure that is correct? Again, as Bill and others have pointed out, the published SPL ratings are probably meaningless in an absolute sense, but that extremely low SPL for the SWR seems incorrect. In A/Bing my BergHT210S (published SPL of 99 if I remember correctly) with my Schroeder 1210R (published SPL of 102)... with both cabs being 4ohm versions, I definitely notice the 1210 having more 'volume' with the same amp and settings.

    So... who knows! However, just get that Schroeder on a gig and crank it up, and it will get plenty loud:bassist:
  18. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    One must also know the frequency at which the sensitivity and SPL readings were taken. My guess is that at many speaker companies those readings are taken at far higher frequencies than you would expect for a cabinet designed for bass amplification. Something like 500 or 1k .... rather than say 40, 60.

    On the idea of comparing cabinets in the store; that's half right. By all means compare cabinets. Do it in a band stand environment or purchase from a retailer that will take the cab back in exchange for another AND who offers a decent selection of cabs. Some of the cab's I've heard seem to be designed for a beauty-booty rich bass and shiny top end. A marvelous bed room tone. Get it on stage and the cab disappears in to mud with a little broken glass on top...

    Those ratings would be useful if

    1. They were made in a broad spectrum environment. EG. 30,40,60,80,100,120 on up to about 500 would suffice for me. Basically a plot or curve, rather than a simple number.

    2. There was an independant source (like BassTasters) with the gear to do the measurement.

    We all pretty much agree that there is too much on the line for the manufacturers and that the general testing environment out there is seen as 'corrupt'. Trusting their numbers is foolish. Even those from the companies and guys we like.

    In the end, as usual the simple boring fact is that you have to try the gear out in a meaningful environment and recognize that the cabinet is one part of the system and that what you are testing is the whole system...
  19. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Both figures may be accurate, and both are meaningless. At what frequency was the Schroeder measured? 100Hz? 1000Hz? Is that a peak value or an average value? Only Jorg knows for sure. The SWR may have an average SPL of 95dB, but it may have a response spike inthe midrange where it has 105dB sensitivity. Simplistic SPL ratings such as these are worthless, because there is no uniformity as to how they are measured.
  20. I've put together a new Dell 6400 laptop with Edirol UA-25 interface and a Superlux ECM-999 measurement mic for this purpose. Software is TrueRTA level 4.

    I have a location here for outdoor measuring, but it is currently under water after 5 straight months of rain. If it would EVER stop raining, I can get out and start catching up on my build work, and taking measurements.

    Anybody who wants to make an appointment and bring their cab to Orangevale for inclusion in the database is welcome.

    My initial thoughts are taking all the measurements at 100 watts and 10 meters. This gives a chart comparable to 1w/1m, and more of a real-world indication of how a cab performs.

    I'm more inclined to use 28.3 volts instead of 100 watts. The reason is, a bass amp is a voltage amplifier. The user sets the Volume control to X (a certain voltage) and expects to hear X loudness. A 12-ohm Tuba24 at 28v is less wattage than a 4-ohm 610HLF at the same voltage.

    I want to see the real difference, as that is how it would be heard if the 610HLF was replaced by a T24 without touching the controls. This may/may not be "fair", but I hate that word anyway. I'm looking for "consistent".

    And yes, I will include Schroeders, Accugrooves, and anything else I can get my hands on.

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