cab sensitivity and head room

Discussion in 'Amps and Cabs [BG]' started by Andrew Jones, Dec 10, 2001.

  1. Andrew Jones

    Andrew Jones Inactive

    Feb 28, 2001
    Northampton Mass

    Im sick of loggin my heavy amp around (man if you think giigin is alot of hawling try bein a popular bass player at a big music school;)
    Any way Im thinkin about a eden wt400 and a pair of 112 cabs.

    with 800 peak watts and 400 [email protected] oms Im kinda conserned about sensitivity. the specs on these popular 112'sshow a difference in sensitivity of 6 db from readin alot of stuff on these forums that I realley dont understand Ive learned that this is a big deal

    Bergintino sensitivity: 97db • anechoic: 2.83v/1m
    Aguliar Sensitivity: 99db @ 1w-1m

    Epifani Sensitivity: 100 db SPL @1W 1M

    EA cxl 110 (@1m w/2.83 vrms) 103 dB

    I play five string electric at not truley loud but sometimes a little roudy volumes I want a kinda of fat colored not truly flat sound yet if volume could be had from a different head (like the iamp 350 1200 watts peak) I will deffinetly think about it

    I used to own a eden wt500 that I ran into a 212 xlt cab ( 103DB SPL @ 1w 1m)that worked well and sounded great but it was 500 watts into a 400 watt cab ( 103DB SPL @ 1w 1m)and had somethin like 1000 peak

    oh yah and just to mess things up a little more if parts of this rig could be used for a upright at decent volume it wouldnt be terrible thing

    which cab would you get and why

    thanks for your time and input

  2. A 3 dB increase in SPL is clearly audible. 3 dB also equals twice the electrical power.

    A 6 dB increase is close to a doubling of perceived loudness, and equals 4 times the electrical input power.

    So, if one cab has a 6 dB sensitivity advantage over another, you could cut your amp power to a quarter. Or, with the same amp, reach a MUCH higher volume, or have MUCH more headroom.

    The drawback of a higher sensitivity is usually a decreased low end.
  3. Andrew Jones

    Andrew Jones Inactive

    Feb 28, 2001
    Northampton Mass
    thanks Joris

    So theres a huge difference between berg and ea huh?your saying that the EA will be twice as loud as the berg?The epifani will be half again as loud? A pair commin out of a 400 watt head would get 200 watts each at full volume?
    Considering I play five is it fair to say I should be more conserned with headroom?than if I played a four string?
    might the iamp be a better choice only because of the claim of having 1200 watts peak?the only reason I wasnt focasing on that to begin with is I think Ill like the tone of the eden more.But I could allways focus on its ability to aplify a upright well

  4. rcrimm

    rcrimm Commercial User

    Jun 20, 2000
    Meridian, MS USA
    Customer Service, Peavey Electronics
    About 5% of people tested can hear (perceive) a 1 dB increase in spl. About 50% can perceive 2 dB.

    Most everyone can hear a 3 dB increase, and say "it got a little louder". It takes 6 dB for most people to say "it got noticably louder", or "significantly louder".

    For the average person (50%) to feel that the volume is doubled, takes anywhere from a 7 to 10 dB increase. A 10 dB increase requires roughly 10 times the power.

    These numbers are level and frequency sensitive. Higher sound levels do produce lower dB numbers, frequencies below 1 kHz and above 5 kHz produce higher dB numbers. Most of these findings were tested at about 90 dB, 1 kHz.

    IMHO, I wouldn't get too concerned about a 1 or 2 dB difference when comparing specs, the volume difference shouldn't be that much.

    Besides losing some low end, higher sensitivity ratings also can result in lower power handling and reduced reliability.
  5. I was with you until this last sentence. I don't quite get what exactly sensitivity ratings, *in and of themselves*, have to do with frequency response, power handling, or reliability. For instance, an Eden D410XLT is very efficient, takes a ton of power, and (at least from my own anecdotal experience and that of others I've talked to) is pretty reliable too.

    I am sure many sensitive speakers have low power handling, but I'm equally sure that many don't. In any case, I'm not sure how higher sensitivity could "result" in lower power handling.
  6. I'll take a stab at this. Highly sensitive speakers tend to have lower cone masses and more compliant surrounds and spiders. This helps them to produce more SPL with less input power. Of course, the more compliant the speaker is, the less power needed to reach its maximum excursion. Obviously, this isn't the whole story and there are a lot of other factors involved. But speakers with very stiff, massive cones tend to be less efficient but able to take more power than more compliant ones. Meyer's 18's are very compliant, they're pretty efficient but they can't take a whole lot of power. They suggest a 300-400 watt amp to power it. That's not a lot of power for a high end PA sub. Incidentally, the Meyer drivers reach their excursion limits long before they reach their maximum voice coil current. I wouldn't consider the Eden or the Goliath (105 and 106 dB) to be highly efficient cabinets. I deal with PA cabinets that have sensitivities exceeding 115 dB, 1 watt, 1 meter. They're more medium efficiency. There's definately a trade off between efficiency and power handling.
  7. Fair enough, but what you're saying suggests to me not a strict causal relationship, which is what rcrimm seemed to be suggesting, but a set of tendencies that usually but not always are associated.

    For instance, how would you explain the difference between Eden's 410T and 410XLT? The XLT not only handles more power but is more efficient as well (albeit by only 1 dB at 1 W/1 m) and has more low end (though that could be partially or wholly the result of the 2nd port on the XLT). Finally, offhand, I know of no reason to think the XLT is less reliable than the T, though of course it might be.

    True the Eden and the SWR aren't all that efficient compared to the PA cabs you mention, but in the world of bass cabs, they're very efficient. Trust me on this, I own an Acme!!
  8. There's no hard and fast relationship that's for sure. This stuff is really hard to explain in a nice simple nutshell because there are so many parameters. I didn't mean to imply that it was a strict causal relationship, and if I did I don't:D. I wouldn't guess that the XLT is any less reliable than the T. Although, I don't know for sure. The XLT seems to be constructed a bit better, though. They're certainly efficient compared to Acme cabs.:D So I guess it's all realtive.
  9. I think I know what he means.
    Take an old SVT cab. It had 8 CTS 50- or 60 watt drivers with small voice coils. They had a small mass, and moved very efficiently.(Rated ?) They also were in sealed compartments (Restricts cone excursion).They did not reproduce fundamental lows well, but they put out a lot of SPL. (Made for a 300 watt tube amp). I don't know how reliable they were, but if you put these drivers in a ported cab, they surely would be driven past their limits, and fail.

    My point is the cheap speakers were not any more unreliable than expensive JBLs or EVs, if they were used in their proper application.
  10. Hmm ... numbers ... ratings ...VOODOO!

    Obviously the numbers are valid, and I am very impressed by many TB'ers technical knowledge in these areas. Someday I will actually understand this stuff, just not today.

    I can, however, comment on the Bergantino - I love it! I've A/B'ed the Berg with the Epifani and the Aguilar 1x12's, and I found the Berg to sound fantastic, be very flexible, and take low B abuse very well. It has a nicely punchy sound that I preferred over the Epifani's super-silkiness and the Aguilar's boxy sound. I am scheming and scraping to combine a Berg 1x12 with a 2x10 powered by a Mesa Walkabout. Sure, it's $2,100, but it's a hi-fi, punchy, flexible, and portable mini-death rig.

    As always, YMMV.
  11. Andrew Jones

    Andrew Jones Inactive

    Feb 28, 2001
    Northampton Mass
    thanks for the replys guys

    David ,yah mini death rig thats what Im talkin about! why the walkabout I havent heard one yet does it kill? have you heard a Iamp does it compare? or the eden?
    I saw in your profile that you play upright have you tried it though the set up you mentioned
    Did you a/b the berg aguliar and epifani all together?if so could you persieve a difference a volume?
    thanks again
  12. MikeyD


    Sep 9, 2000
    Actually, a 10 dB increase requires *exactly* 10 times the power - using 10*log(P1/P0). You may have meant a 10 dB increase sounds *roughly* twice as loud.
    I don't follow this at all. Human perception of loudness is certainly level- and frequency-sensitive. But I don't understand the rest of your comment.
    - Mike
  13. OK, but the original remark suggested that higher sensitivity had a causal relation to (1) lower power handling and (2) reduced reliability. If true, this would mean one of two things: (1) if the JBLs/EVs were *more* sensitive than, say, those CTSs you mention, they must also *for that reason* have handled less power (which is not true AFAIK) and been less reliable; or (2) if the expensive speakers were *less* sensitive than the CTSs, they must *for that reason* have handled more power and been more reliable. I don't have all the facts here, but somehow this doesn't sound right. Are JBLs, say, *less* efficient than, say, CTSs? I know they handle more power.

    I'm really not trying to be argumentative with anybody. I just like to try to understand things as well as I'm able to, and this just doesn't seem to add up completely. To me, anyway.
  14. I hope this helps!
  15. MikeyD


    Sep 9, 2000
    One can design a motor (which, in this case would be the coil/magnet assembly of a loudspeaker) to handle more power but be less efficient. One can have absurd coil lengths outside the air gap that eat up power (I^2*R) while generating no magnetic force. One can have oversized air gaps that make poor use of the magnetic field. There are *lots* of things that can separately contribute to inefficiency and power handling. So you are right, Richard, these two things aren't necessarily tied to each other. I could design a "quietspeaker" that has a huge coil and completely immersed in an oil bath with concrete walls: it could handle 20,000 watts and have a sensitivity of only 10 dB @1w 1m. Yes, this is a preposterous idea, but I'm trying to make a point! (Where is my pencil sharpener??)(This is what Spacegoat could use to do the THD tests on his SVT!)
    - Mike
  16. rcrimm

    rcrimm Commercial User

    Jun 20, 2000
    Meridian, MS USA
    Customer Service, Peavey Electronics
    You are right, I meant exactly 10X power and "roughly" twice as loud.

    Our hearing is tuned to hear the human voice, mostly midrange. We are much more sensitive to changes in this range. It takes more of a volume change in the higher and lower frequency ranges for us to perceive the difference.
    The starting point makes a difference too. It takes more of an increase in level at 90 dB, than it does at say 60 dB, in order for us to notice the difference. That's what I meant by the rest of it.

    Also, I didn't say that higher efficiency *must* result in lower power handling, only that it can.
    All other factors being equal, increasing efficiency lowers power handling. There is a lot more to this I know, but I didn't want to write a novel here.

    The point is that there are almost always tradeoffs to consider when comparing specs.
  17. MikeyD


    Sep 9, 2000
    Thanks for the clarification.
    - Mike
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