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Cab sensitivity issue

Discussion in 'Amps and Cabs [BG]' started by trilobeat, May 6, 2005.

  1. I am thinking about adding a second cab to my Accugroove Tri210L. The sensitivity of it is 103db. I think that when I connect another cab with lower sensitivity, the new cab will not increase the loudness too much, am I right ?
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    In sufficient information. What is the impedance and f3 of your present rig? What is the sensitivity, impedance and f3 of your contemplated addition? Knowing only one factor doesn't tell you enough to make an informed decision. It takes at least these three specs to have a good idea what might happen. Otherwise your options are to either try the new combination or add another speaker identical to what you already have.
  3. ok, I meant the general issue of different sensitivity of two cabs.
    I have Tri210L (2x10", 103 db SPL, 4 or 8 ohm) and I want to add another 2x10" cab with 93 db sensitivity and 8 ohm. Is it a sufficient info ?
  4. what does "f3" mean ?
  5. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    If one cabinet sensitivity is 103 dB/1W and the other is 93 dB/1W, they are very severely mismatched....

    I would expect only about a 1 dB change in volume, max, when adding the 93 dB cabinet to the 103 dB cabinet, assuming they are otherwise equal and have same impedance, and same power going to both of them.

    I would not even bother with that combination, its a waste of effort hauling the second cabinet.

    When using two cabs with an amp, they ought to be "similar" in rated sensitivity, for best results.
  6. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    Sounds like you want to add either an Ampeg Portabass or an Acme Low-B2; if it's the latter PM TomBowlus, he owns both the Tri210L and a pair of Low-B2s and can probably tell you how well they match. My suspicion is that the Accugroove will overpower the Acme unless they're on independent channels. If you can power them separately you can probably get almost as much volume out of the Acme as the Accugroove, particularly if you roll off a little of the very thick fat low end. If it's an Ampeg Portabass, who knows, does anyone own any? ;)

  7. Whappo Grande

    Whappo Grande

    Feb 9, 2002
    Sunnyvale, CA.
    Engineer: AccuGroove Speakers & Amps
  8. The cynic in me asks "at what frequency is the claimed sensitivity?"

    If taken at 1 KHz, who cares, unless you a playing high quitar notes. In most cases, the overly-hyped sensitivity numbers aren't even close at 100 Hz. The measurement technique, or degree of fibbing, varies wildly between manufacturers. Especially so, when the measurement technique is not posted.

    Without actually measuring the specific cabs, I think your best best is adding a 2nd Accugroove. The resulting sound will be more of the same, and balanced between the two cabs.
  9. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Your existing 2x10 has to be one or the other. It can't be both. Let me assume it's 8 Ohms for the sake of argument. The 10 dB difference in sensitivity is a factor of 10 in acoustic power. In other words, you are actually increasing your total acoustic power by 10% when you add the second speaker, at a constant output voltage from your amplifier. That's an 0.4 dB increase in overall sensitivity. But... your amp is now driving 4 Ohms instead of 8 Ohms, and probably with less power per speaker than the 8 Ohm rating. For instance, my power amp puts out 100 W into 8 Ohms but only 150 W into 4 Ohms instead of the 200 W that would be expected if the amp were operating at a constant output voltage. Going from 200 to 150 is a drop of 1.2 dB. You have to look up the rating for your own amp, but you get the idea.

    Bottom line... plugging in that inefficient cabinet will actually make your overall system less efficient -- it is just robbing juice from your power amp.

    Of course all of this is idealized -- the question of "at what frequency" still rears its ugly head. A rating of 103 dB for a 2x10 makes it seem likely that the speaker is rated at a "favorable" frequency. The 93 dB speaker is rather inefficient by bass speaker standards, but it may be a more honest rating too.
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    f3 is the frequncy at which the speaker is down 3dB from average, below which sensitivity drops further. The rate at which it drops depends on the cabinet topology. 103 dB sensitivity sounds high, but if the f3 is 100 Hz it's pretty poor for bass. 93dB sensitivity sounds low, but if the f3 is 35Hz it's quite good for bass. It's possible to draw valid conclusions and make valid comparisons from specs only, but doing so requires both an adequate number of specs and the expertise to understand them.
  11. illidian


    Jul 2, 2004
    The cab doesn't have to be simply four or eight ohms.

    Accugroove's cabinets emply an "AccuSwitch" which will change the impedance of the cabinets between four and eight. So his cabinet is four or eight ohms.

    I think you should do a side-by-side comparison. Basing off the numbers alone, it sounds like adding that second cabinet will bring down your volume. But you don't hear numbers, you hear sound. Listen to them and be the judge.
  12. IvanMike

    IvanMike Player Characters fear me... Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    i' m seconding some of the ideas here. belive it or not (some of you won't) i belive specs to be very important (as long as you have enough of them and they're accurate ;) )

    however, as implied, it's rare that you'll have enough of them and have the savvy to get a good picture of what the final sound will be.

    so i agree with the idea that if you like the tone already, maybe a second of what you have is the best approach. likewise, as inconvenient as it is, sometimes it's best to truck your stuff out and actually try your cab with the other cabs you're thinking of.

    i was just talking to a guy the other day mentioning this and he said he'd flat out refuse to bring his bass, amp and cab out for comparison - too much of a hassle. OK, whatever. Maybe he's the one guy that can compare new stuff to his gear without actually having to have them both in the same room and a/b'ing them back to back, but i doubt that guy really exists. ;)
  13. thanks for help. I would buy the second Tri210L (which is really 4 OR 8 ohm as Illidian pointed out, it has the Accuswitch), but it is a bit expensive for me at the moment. I tried 1x15" by ESH (Czech manufacturer, 4 ohm, Eminence equipped) and I disliked the overall sound with Tri210L. I missed clarity and punch and it didn't help with the loudness too much. And the total impedance of these two cabs was out of recommended limits for my Thunderfunk (below 4 ohm). The another 2x10" I talked about is Acme B-2, but it seems that I will wait few months and buy the second Accugroove, which is really amazing cab (but $$$$).

    thanks again to everybody ;)

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