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  1. #1

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    Which amp configuration is louder:

    One 100 watt amp combo with a single 1 x12

    Two 50 watt combos each with a 1 x 12

    Assuming the 2 - 50 watt amps are run in stereo with a splitter, and assuming all amps 50 and 100 watt type are something like solid state amps running clean made by the same manufacturer, my guess is that the two 50 watt config is going to sound much louder. I can't buy the amps to just do the experiment and find out for myself, so I'm wondering what others who may know think.

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  3. #2

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    Loudness has a measurable relationship to the number of speakers ( of the same efficiency) pushing a given wattage.
    There's a very useful table on the last page of "how much power do I need?' , a document on the Acoustic Image site.
    It illustrates why the Fender Super Reverb was such a loud 40W amp.

  4. #3
    I found this on the Acoustic Image website:
    There are two ways to get more volume. One is to increase the output power of the amp and keep the speaker the same, the other is to keep the power output the same and add an identical speaker. So if you double the power output of the amp, the result is 3 dB more acoustic output from the speaker and 3 dB higher SPL. If you double the number of speakers, the result is double the sound radiating area and doubling of the pressure level coming from the speakers. Since SPL is proportional to pressure squared, the output of the system is increased by a factor of 4 or 6dB. So, doubling the output power results in 3 dB higher SPL while doubling the
    speaker radiating area results in 6 dB higher SPL.

    As you can see, adding speakers is a much more efficient way to increase volume in an amp/speaker system.
    Source: http://www.acousticimg.com/docs/The%...of%20Power.pdf

    So, in the proposed question (1 - 100 watt combo amp with 1 speaker vs. 2 - 50 watt combo amps each with 1 speaker) at the same time you lower watts for a SINGLE 50 watt amp (3 db lower yield based on power) you also add another 50 watt amp (compensating for 3 db loss based on power). Add to this the additional speaker in the 2-50 watt config and I would think there's just no way that 2 - 50 watt combo amps will not sound louder than the single 100 watt combo.

    Remember too I'm talking about solid state amps, not tube.

    But admittedly, I can't do this experiment and observe with my own ears so I don't know if I'm overlooking something.
    Last edited by Petros; 01-26-2017 at 07:24 AM.

  5. #4

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    The two 50W amps will seem louder (but so will the 100W if you just add an extension cab to it).

  6. #5

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    I think the AI web site is wrong or at least misleading. If all things are equal (e.g., speaker efficiency, cabinet design, room size and materials), two speakers producing 50 watts each will not be "louder" than one speaker producing 100 watts. By "louder" I mean the average volume level in the room. However, two speakers will produce a much different pattern in the room, so as you walk around the volume levels and frequency response may vary quite a bit from that of a single speaker as the relative phase between the two sources changes.

    Two speakers in a single cabinet front facing will be more directional than a single speaker, so will be louder on-axis, but fall off more rapidly off-axis. That's a good approach to increase volume for the audience in a large room without raising stage volume.

    Two speakers in separate cabinets placed somewhat randomly will produce a more complicated combined pattern. I like to use this approach to disperse the sound when I'm playing in a small room or when I'm in a big band and I want both the band and audience to hear me.

    By the way, I think an open back cabinet with a reflecting surface a couple of feet behind has a similar effect to two speakers placed somewhat randomly: increasing stage volume but with a more complex pattern and frequency response.
    Last edited by KirkP; 01-26-2017 at 12:45 PM.

  7. #6

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    Quote Originally Posted by Petros View Post
    Which amp configuration is louder:

    One 100 watt amp combo with a single 1 x12

    Two 50 watt combos each with a 1 x 12

    Assuming the 2 - 50 watt amps are run in stereo with a splitter, and assuming all amps 50 and 100 watt type are something like solid state amps running clean made by the same manufacturer, my guess is that the two 50 watt config is going to sound much louder. I can't buy the amps to just do the experiment and find out for myself, so I'm wondering what others who may know think.
    Either configuration is loud enough to give you tinnitus ...

    All my experimentation has been with multiple tube amps of lower power than this, so perhaps not applicable, but ... My conclusion is it's difficult to say. There are so many differences in timbre between stereo and mono set-ups, and "loudness" is so much a matter of perception as opposed to objective measure that there's no definitive way to answer the question. Also, distortion IME is a huge factor in how loud something seems -- given the same input coming out of two amps with different amounts of distortion at high SPL, the more distorted output feels louder subjectively. Saying something like "running clean" doesn't really help answer the question in the abstract because it depends on which amps you're talking about. Every amp has some amount of harmonic distortion -- the point on the dial where enough kicks in to alter the perceived loudness varies. So under some conditions, the two 50-watt amps would seem louder than the one 100 watt amp, but under other conditions the opposite would be true.

    John

  8. #7

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    Also, the human ear has what you might call a "built-in compression" to allow them to work over wide dynamic range (very soft to very loud). Due this compression, doubling the power of a signal is perceived as much less than a doubling of "loudness".

    So when we perceive major differences between amps rated at 50 watts vs. 100 watts, those differences are mostly due to other factors such as circuit design, EQ, speaker & cabinet design, etc.

    Note that a speakers generally become more nonlinear when pushed hard, so if you tend to play at high volume levels, doubling the power could cause the speaker to start breaking up, which can be perceived as being "louder" even though in theory it's not.

    All that being said, I love playing through twin speaker systems, whether single vs. separate cabinets, separate vs. single amplifier, open vs. closed back. It always gives me the feel of more "muscle" no matter what volume I'm playing.
    Last edited by KirkP; 01-26-2017 at 04:30 PM.

  9. #8

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    Quote Originally Posted by marcwhy View Post
    The two 50W amps will seem louder (but so will the 100W if you just add an extension cab to it).

    This is what I do with my 80 watt Mesa Boogie Mk IV widebody combo.
    For outdoor gigs I add a Mesa Thiele 1x12 ext. speaker to spread the sound.

    Believe me, it is VERY loud.

  10. #9

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    To eliminate the acoustic perception issue, which configuration moves more air in terms of SPL or something?

  11. #10

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    Quote Originally Posted by rpjazzguitar View Post
    To eliminate the acoustic perception issue, which configuration moves more air in terms of SPL or something?
    If each setup is in a single cabinet with the same signal and appropriate speaker ohms, and of the same "match" to the Thiele-Small data of the speakers, the speakers all have the same sensitivity rating in dB, as noted above and measured at 1 meter ... the 2-speaker cabinet will give the higher figures of dB as posted above.

    The two speakers would need half the ohm rating or close to it, and the cabinets (especially if sealed) would need to be similarly sized to the total VAS ratings per cabinet ... so they could likely need to be different sized boxes. Open back cabs are <less> affected by a speaker's VAS rating, but not <unaffected> by it.

    That enough qualifications? ????

    Stumbling fingers still need love ...