Distance from the cab makes a difference?

Discussion in 'Amps and Cabs' started by glogulus, May 11, 2019.

  1. glogulus

    glogulus Silver Supporting Member

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    I recently bought a wireless system and noticed something that maybe someone can explain why it's happening.

    I normally play at bedroom volumes and noticed that, playing with a lot of gain, standing close to the amp and standing further away really makes a difference in tone. I noticed that when I'm about 2-5ft away it sounds great, but when I starting walking about 15ft or more away it sounds as though the top end starts to disappear leaving a hollow/bassy/muffled kind of sound. If I turn up the presence and treble it starts to sound good again, but then I also have to raise the volume. I'm guessing this is a normal and there's some kind of scientific explanation for this. But, I never realized that distance can make such a difference. I also noticed that clean sounds don't suffer as much at different distances.

    I tried searching for this type of topic but nothing came up and I thought it interesting.
     
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  2. candid_x

    candid_x Supporting Member

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    Forgive me for questioning the obvious: the distance of your ears from the speaker when you are 15' away? Especially at low a volume.

    I always did sound checks from a good distance, as that's closer to what the audience hears.
     
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  3. glogulus

    glogulus Silver Supporting Member

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    Hmm. I wouldn't think 10 extra feet within the line of site to the amp would make such a drastic difference? It's like a bunch of the treble and upper mids disappear. I guess it's normal and you only need to raise the volume or increase the mid, presence, or treble. I guess it's just interesting to me how much difference distance makes. Even 10ft.
     
  4. teemuk

    teemuk Member

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    It is a typical characteristic of large 'midrange' speakers that they disperse higher frequencies to narrower space than lower frequencies. 'Beamyness' as it is called.
    The characteristic is enhanced when horizontal cone area increases. A 4x12" cab can be disturbingly beamy.

    Essentially, at a distance higher frequency response depends a lot on listener's axis in relation to the loudspeaker(s).

    Overdriven tones contain more upper order harmonic (high frequency) content than mere 'clean' tones so they make the characteristic even more evident.
     
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  5. glogulus

    glogulus Silver Supporting Member

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    Thank you for the explanation!
     
  6. guitarman3001

    guitarman3001 Member

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    Even 1 foot can make a big difference.
     
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  7. Thumpalumpacus

    Thumpalumpacus Member

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    Treble soundwaves dissipate quicker because they cycle faster (2-4000 cycles per second vs 100-1000). As treble sounds expend their energy they lose the ability to push neighboring molecules and that means that they project less than bass frequencies, which do not dissipate so much energy flopping back and forth in the soundwave.

    If you're standing 15' away instead of 5', you've tripled the distance those trebles must travel, and at least tripled the dissipation they experience. I'm not sure if they dissipate in direct proportion to the distance, or if there's an inverse-square or other function involved. If the latter, you're dissipating much more than three times.
     
  8. classicplayer

    classicplayer Member

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    Thanks to the OP for raising this phenomenon. I mentioned this issue to my wife at dinner this evening
    and I never guessed that less than two hours later that I'd be reading about this very subject. I've been scratching my head trying to figure out why I have the same issue with my Dark Terror and the PPC112 cab. The cab has a V30 speaker and being closed back has a “beaming” type of projection from it. I
    also think amp and speaker both have plenty of mids.

    When kneeling in front to dial the amp in, it sounds fine with the right amount of top end. I move away 4 feet, sit to the side and it still sounds decent. However after 20-30 minutes of playing, the high end is not there. I've been blaming it on the tubes getting fully warmed to temperature and perhaps the speaker also warming a bit. I re-tweak the amp, but not all of the highs come back. More than one comment I've received in the past claim that I'm experiencing ear fatigue!?


    classicplayer
     
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  9. candid_x

    candid_x Supporting Member

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    Perhaps think of it as ear adjustment, and not the ear only. The acusis acts as the brain's sound processor. It's the inner soundman.
     
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  10. glogulus

    glogulus Silver Supporting Member

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    Bro. This was amazing. Thank you!
     
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  11. classicplayer

    classicplayer Member

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    Based upon this explanation I think that I should be setting the e.q. and then stepping or sitting back say 10' or so to make sure I hear the highs. In my case though, I still hear the highs after setting the e.q. while a foot or two from the speaker while I'm back 10 feet or so. My issue is that after 20 to 30 minutes
    of playing the highs are not there either 10 feet back or even 1 foot back!?


    classicplayer
     
  12. Thumpalumpacus

    Thumpalumpacus Member

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    I couldn't give you an informed answer, bud. My best guess would be ear fatigue but knowing you gig Sabs, I don't think that's a good answer, lol.
     
  13. Thumpalumpacus

    Thumpalumpacus Member

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    I'll be lecturing at Harvard next week, tip your barrista!
     
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  14. glogulus

    glogulus Silver Supporting Member

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    Oh man! I just had an epiphany. I have owned, and sold, a few older Marshall amps in the past and they all were super bright when standing close to them. I bet if I had stood about 15ft away they would have sounded just fine.
     
  15. twotone

    twotone Member

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    If a 412 cabinet is recorded, to my ears it sounds much better if the mic is three to five feet away from the speakers.
     
  16. Ripthorn

    Ripthorn Member

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    While the general theme is correct, the frequency range over which s guitar operates isn't subject to widely differing atmospheric absorption rates. This effect starts to really come in to play above the range of human hearing.

    A loudspeaker doesn't vibrate in one mass, it has portions vibrating at different amplitudes at different places for different frequencies. What this does is create a sound field at and near the speaker that interferes with itself a lot. This effect is called evanescing. Once you move away, the sound field stabilizes and there is no significant effect of evanescence. However, the region for this is super close to the speaker. A similar effect happens with a cab with multiple speakers, but the frequency range if interference is lower due to the larger spacing and larger sound sources.

    High frequencies travel in the original direction much more so than low frequencies. This is called diffraction. You will experience this effect when standing in the room, and will be very noticeable if you go from on the speaker axis to fast off it.

    Another possible effect is simply RF signal degradation. Depending on your setup, your wireless signal might be getting compromised with the increased distance. There could be interference or some parasitic impedance that is more strongly manifested at greater differences.
     
  17. Sirloin

    Sirloin Supporting Member

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    No one mentioned the room yet? What is the room like you are playing in? If it is hardwood floors or tile and a lot of glass and hard surfaces, you may experience much more treble standing away from the amp.

    If you have carpet, tapestries, a bed with linens, these soak up high end quickly.

    Ever sound check a band in an empty room, then see it sounds totally different once the room has a bunch of people in it?
     
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  18. SDR

    SDR Member

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    This is why I enjoy my slant cab. Having the top two speakers slant up slightly gives me a bit more sound and tone across a room. Slightly easier to dial in what I want. Especially versus a one speaker combo sitting on the floor, with the speaker at a 90 degree angle to the ground.
     
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  19. ScioBro

    ScioBro Silver Supporting Member

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    If you can get a long cord, you can check the distance thing w/o wireless. Rule it in or rule it out
     
  20. HotBluePlates

    HotBluePlates Member

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    Another factor for treble vs bass is that bass frequencies have long wavelengths that tend to "wrap around" objects. Higher frequencies with shorter wavelengths tend to be blocked by objects, don't spread out as well, and are directional ("beamy"). Read starting the 4th paragraph here.

    Recording studio engineers know frequencies above 1kHz are most important for positioning a sound in the left-right stereo spread. That's because the wavelength of a 1kHz sound is ~13.4 inches, and a half-cycle is mighty close to the distance between human ears. You're not conscious of it, but your brain detects which ear hears tones above 1kHz first/louder, and translates that to, "The sound's over there!"

    You don't need to have a closed back cab to experience the directionality. If I play one of my open-back combo amps in the living room, the amp tends to be 20 feet away & not pointed directly at me (just because of the layout of the space). The amp sounds definitely darker than when I move closer to the amp & stand on-axis.
     

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