Using an extra speaker cab instead of attenuation?

Discussion in 'Amps and Cabs' started by hipfan, Jun 7, 2015.

  1. GCDEF

    GCDEF Supporting Member

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    No, it doesn't. Power comes from the amplifier. A speaker is a passive device that cannot add energy to a system.
     
  2. IM4Tone

    IM4Tone Member

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    Something cheap to try....Turn your amp around backwards, tilted up slightly and bounce the sound off the wall (assuming there is one behind you). Years ago, we did that at one single venue and it helped. Nothing to lose or cost to try this.
     
  3. hipfan

    hipfan Member

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    Thanks for all the responses, guys. Looks like I have a lot of thinking and experimenting to do!
     
  4. thiscalltoarms

    thiscalltoarms more gadgets than Batman. Gold Supporting Member

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    Fryette Power Station is my next attenuator. A lot of dudes that I trust and that I know have legit ears have said it can do transparent or can sweeten things up to balance perfectly as you cut back the volume. Freaking incredible unit from the looks of it. I'll be picking one up soon. Do it.
     
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  5. lousyatit

    lousyatit Supporting Member

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    Does anybody even make a speaker in the 93db range?
     
  6. Jonny G

    Jonny G Member

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    V.O.R. 12@ Alnico; Weber makes some 95dB's which is in the ballpark i guess. Never heard them and don't see a lot of commentary on them which is why I'm curious myself.

    Sure, power comes form the amp, but you get more dB for your buck when multiplying speakers given most of the volume is genrated at the beginning of the power curve. That's why a 2x12 is (3dB) louder than a 1x12 (with identical speakers of course) and a4x12 is (3dB) louder than the 2x12. The best explanation i have seen of all this is here: http://www.dinosaurrockguitar.com/new/kb/cabs-speakers/speakers/role

    For the purpose of this discussion, i will qoute form it: To put it simply, assuming a sameness of cab design and all speakers of the same type, If one speaker produces a cab loudness level of 80 dB then two speakers with produce 83 dB and four of them will produce 86 dB. Every time you double the number of speakers in the cab you up the decibels by three. How much is three decibels to the human ear? My friend Tim at Ear Candy Cabs explains the increase this way. With one decibel being the lowest increase in volume the average human ear can detect, three decibels would be described as slightly louder. So, 2 speakers are slightly louder than 1 speaker and 4 speakers are slightly louder than 2 speakers.
     
  7. GCDEF

    GCDEF Supporting Member

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    Rubbish. Following that 8 speaker produces 89dB, 16 92. If all it took to generate volumee you could power a stadium sized PA with a clock radio just by adding enough speakers. Power comes from amps. Passive devices cannot add energy. This is basic physics. There's a lot of pseudoscience on these forums and a lot of it is wrong, even if it comes from people that supposedly should know better.
     
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  8. amphog

    amphog Silver Supporting Member

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    It it not about adding energy, but different acoustic coupling.
     
  9. Dave_C

    Dave_C Member

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    It absolutely does NOT. The amp power has not changed, so adding another speaker just send half the amp power to one speaker and half to the other speaker. SPL stays the same, unless the speakers are close together, in which case, you will get some phase cancellation in the frequencies we are most sensitive to and REDUCE perceived loudness. :messedup ;)
     
  10. Dave_C

    Dave_C Member

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    One of the best purchases I've ever made.
     
  11. Dave_C

    Dave_C Member

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    This is absolutely incorrect and anyone can confirm this with a dB meter. I have. You get ZERO increase in SPL. There are numerous more scholoarly articles on the subject out there.
     
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  12. Dave_C

    Dave_C Member

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    Exactly. I have an EarCandy cab. Worst sounding cab I've ever owned. Would not trust anything they say. LOL.
     
  13. Silent Sound

    Silent Sound Member

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    It is simple physics. Yes, electrical power comes from the amp. However, you don't hear electrical power. What you're hearing is rapid shifts in air pressure created by the transducer (speaker) that is powered by the amp. Adding a more efficient speaker will produce more volume from the same output power, as we all know. So while a passive device can't add energy to a system, a transducer that translates energy from one form to another can be more or less efficient and transfer more or less of that initial electrical energy into acoustic energy. And yes, it's well accepted that theoretically, you could generate enough sound to fill a stadium with a 1 watt amplifier. The laws of physics don't prevent this from happening. Now, no one has figured out a way to make a speaker efficient enough to actually accomplish this goal, but the principle still holds strong.

    Now while adding a second speaker doesn't change the power output of the amp, it does change the surface area of the speaker. You gain about 3dB's from doubling the speaker's surface area. Also, as mentioned before, when two or more speakers are placed in the same cabinet (especially if it's a sealed enclosure) you get acoustic coupling between the speakers. Now keep in mind that if you add a second speaker, you're are indeed halving the power to that speaker. So it would seem that you're gaining 3dB's from adding a new speaker, and loosing 3 dB's from halving the power, so you're coming out even. However, you're not considering the effects of how speakers react to increased power. See, as you increase the power going into a speaker, you're generating more heat in the speaker's voice coil. This increases the impedance of that speaker and as the impedance increases, the power running through it decreases. So by running two speakers at lower power levels you're decreasing the resistance at the output and allowing the amp to actually output more power. There are other reasons too why adding speakers increases volume.

    But anyway, let's not go too far into the science and math. I know you checked your cabinet with an SPL meter, but I doubt you did than in an anechoic chamber with a properly calibrated SPL meter. I know I haven't, and I'm not going to. And anyone who's done any critical applications involving sound will certainly note the room plays a huge role in what we perceive. So instead, lets use some logic to work our way through this. While it's possible for a single speaker to fill an arena, and it's possible for a 1 watt amp to fill an area with sound, you never see anyone doing that. Why? I've also seen single speakers that are supposed to be able to handle up to 2,000 watts of power. Why not just use one of those speakers for the bass amp instead of those huge 8x10's? The answer is because both increasing power and increasing surface area are ways to increase volume. And it's a lot easier and cheaper to use a multi speaker, high powered amp to produce all of that sound because you're not pushing these technologies to their extremes.
     
  14. GCDEF

    GCDEF Supporting Member

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    I didn't want to get into that level of depth with my response. I realize there are situations where an additional speaker can add more volume. It's a very long way from the post I responded to which was a blanket statement that doubling the number of speakers adds 3dB.
     
  15. Dave_C

    Dave_C Member

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    This doesn't apply to this case because we're assuming th esame speaker is used in both cabs.


    This is NOT well accepted theory. That 1W will divide evenly amongst that stadium full of speakers and will actually produce LESS SPL due to phase cancellation (at the frequencies we're most sensitive to) and perhaps also due to nonlinearities at the EXTREMES of power dissipation for any given speaker. In this case, dividing 1W between 1000 speakers (for example) may noy impart enough energy into any of them to obtain its rated sensitivity, which is usually 1W @ 1m @ 1KHz. So, ALL theory point to the fact that you will get equal or less SPL as you add more speakers.

    This only occurs at the very extreme high and low ends of a speaker's rated dissipation and the effect is quite minimal. At the home, rehearsal and gig levels of 99% of those playing guitar, you will experience the SAME SPL or less, due to phase cancellation. I HAVE MEASURED THIS AND CONFIRMED IT IN 1x12, 2x12 and 4x12 cabs. The 4x12 was actually 1dB quieter with an C-weighted dB meter than the 1x12. Same speakers in all. The 2x12 flickered between the same as the 4x12 and 1dB more.

    And, because of that, you will keep propagating this myth. What you're saying is not theoretically true nor does it occur in the real world. I have made my measurements in three different venues and at various distances form the cabs in question with identical speakers. This is the real world that the OP is operating in. You don't need a chamber to prove what I'm saying. I got the same results every time, as mentioned above. You will never get more SPL by adding speakers. The loudest cabs every time I've run this experiment were the 1x12s...but only by about 1 dB, probably due to the lack of phase cancellation in a 1x12.

    Both bassplayers and guitarists use more speakers to spread out the power dissipation so they don't blow speakers, NOT to increase volume, since that doesn't happen when adding speakers. The original 4x12 cab and full stack were created because the speakers were only 20W and the 100W amps cranked up and driving them could produce 150W or more! So, they needed the 20W * 8 = 160W worth of speakers to keep from blowing them! And, people STILL did. It had NOTHING to do with any assumption that adding speakers increases SPL. It only prevented you from setting fires to the paper voice coils in the original 20W Greenbacks.
     
    Last edited: Jun 10, 2015
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  16. IM4Tone

    IM4Tone Member

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    I realize it's a dangerous practice to accept someone's calculations without fully understanding all assumptions made and the details of the formulae. Having said that, I've given the following link only for the purpose of showing that the designer of this calculator supports the 3db gain by using 2 vs. 1 speaker using common parameters associated with guitar amps and cabs, i.e. 100 db sensitivity, 50 watts, and measured at 3 feet for 1st, one, then 2nd, 2 speakers.
    Check it out: http://myhometheater.homestead.com/splcalculator.html
    What say you to this?
     
  17. GCDEF

    GCDEF Supporting Member

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    Look at what he says though.
    .
    "4. The number of speakers in the system. For stereo, use 2. For multichannel systems, try using 3 (for left, center, and right). This calculation assumes that the speakers are each driven by the same power, have similar efficencies, and are equidistant from the listening position."

    In a multi-channel system, each speaker would get equal power and when you add a speaker you're adding the amp power to drive it. The extra volume would come because the power has doubled. In effect, he's disproving the adding a speaker gives you 3dB, because he's doubling amp power and picking up 3dB as expected. If adding another speaker also gave you 3dB, you'd expect a 6dB increase.
     
    Last edited: Jun 10, 2015
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  18. IM4Tone

    IM4Tone Member

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    Hadn't interpreted it that way, but yes, that's obviously what was meant. If I take the 50 watt amp with one 100 db speaker and compare the results to 25 watts powering each of two 100 db speakers, the SPL is the same. Good catch on your part!
     
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  19. Dave_C

    Dave_C Member

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    Exactly! Been busy and haven't been back here in a day or so. Excellent find and excellent response! Saved me some time. :)

    Once again, the measurements don't lie and they support the actual physics. Taking any single amp at any single output wattage and adding speakers will NOT make your system any louder. It will only change the tone and possibly the dispersion. Speakers only absorb and transmit energy. They cannot multiply it. Only adding another amp can do that...or turning up the amp you have.

    I would also allow for very slight changes in volume due to cab differences (to accomodate different numbers of speakers) and phase cancellation, which may actually lower perceived volume because it produces notches in the mids and highs.
     
    Last edited: Jun 11, 2015
  20. mlj_gear

    mlj_gear Member

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    All of that, and the OP wasn't talking about just adding a speaker... He was talking about adding a speaker and intentionally dampening/isolating it to reduce the volume from the non-isolated speaker.
     
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