Beam Blocker vs Foam cutout?

Discussion in 'Amp Central Station' started by scrapyardblue, Jan 27, 2010.

  1. jhundt

    jhundt Doctor of Teleocity

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    the foam apparently does need to be acoustically absorbent, according to the inventor's description. The foam that he specifies is not really a special acoustic foam or an acoustically transparent , it is just a generic soft open-cell foam. I think that you could probably locate something similar at local upholstery or sewing shops.

    here is what he specifies:
    from the McMaster-Carr on-line catalog (http://www.mcmaster.com/#) paste the part number 85735K72 in the search bar

    part no. 85735K72
    (Same as 8643K512)
    Polyurethane Foam Sheet 3/4" Thick, 12" X 12", Charcoal, Firmness Rating 4
    In stock at $5.94 Each

    Material Type - Polyurethane Foam
    Shape - Sheets, Bars, and Strips
    Backing - No Backing
    Thickness - 3/4"
    Thickness Tolerance - ±0.063"
    Length - 12"
    Length Tolerance - ±1/8"
    Width - 12"
    Width Tolerance - ±1/8"
    Temperature Range - -20° to +180° F
    Cut With Scissors, Knife, or Saw
    Tensile Strength -27 psi
    Stretch Limit -115%
    Density - 2 lbs./cu. ft.
    Foam Structure - Open Cell
    Texture Type - Fine Cell
    Foam Firmness - Very Soft
    Firmness, psi - 1.09 (25% Deflection)
    Compression Recovery - Excellent
    Color -Gray
    Finish -Textured
    Tolerance - Standard
    Specifications Met - Underwriters Laboratories (UL)
    UL Specification - UL 94HF1
    Properties - Oil Resistant, Abrasion Resistant, Tear Resistant, Impact Resistant, Weather Resistant, Chemical Resistant, Electrical Resistant
    Notes - Material does not have a skin.
     
  2. Will Chen

    Will Chen Tele-Holic

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    The issue is my amp is shooting at my calves not at my ears so in reality I'm not adjusting the eq from "directly in front". The vast majority of gigs I play are on a small stage typically without PA reinforcement where I'm at an angle to my my amp and I adjust it sound the way I like. Previously I'd have to crank up the treble a bit as the directivity of the Bandit was causing me to hear less highs at the angle at which I was versus the people in the crowd. Since installing the foam, there is a much more even spread of the sound across a wider radius so from the same listening positioning I need less treble to get the same tone and the tone is consistent directly in front of the amp.

    You seem like you don't have an issue the way in which you use your amp so as they say, if it ain't broke...
     
  3. TNO

    TNO Friend of Leo's

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    I've tried beam blockers in several amps and removed them every time. Sound blockers is more like it.
     
  4. Ted M

    Ted M Tele-Afflicted

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    I do notice a difference. The amp seems a little less bright and a little more compressed sounding. I'm hoping it will not be too great a diff, because I like the sound of this amp/speaker, just want to tame it a little.

    I'll post my reaction this weekend after Friday and Sat gigs.
     
  5. robt57

    robt57 Telefied Ad Free Member

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    I wonder if you can dial it in by increasing the diameter of he center hole??
     
  6. doublee

    doublee Tele-Meister

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    I dont believe this 'improves' an amps sound in my experience, it addresses a specific problem: the hot spot or 'beam' produced by some 12's in some situations. It makes the sound more even over a wider angle.

    I dont know about 15's so cant comment on that. Also in my experience 10's dont really need it.
     
  7. slauson slim

    slauson slim Friend of Leo's

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    Duct tape. Looks ratty, but cool. On Princeton and CVR.
     
  8. scrapyardblue

    scrapyardblue Friend of Leo's Silver Supporter

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    No beef against duct tape ever. Patched a hole in a canoe once with it. Sarah Borges uses it as strap locks on her Tele. All good.

    That said, I did just order some foam.
     
  9. Rhomco

    Rhomco Friend of Leo's Gold Supporter

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    I have a few

    Mitchell Foam Donuts for 12" speakers left over from a project....FYI....Just in case............if you are counting them.........or.whatever;)
    Rob
     
  10. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    haha, softest sell ever! ;)
     
  11. Joe-Bob

    Joe-Bob Doctor of Teleocity

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    Have any of you guys considered turning down the treble on the amp? :confused: I hear that it can be very cost-effective. ;)
     
  12. fezz parka

    fezz parka ---------------------------

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    I use a little plexiglass shield I made. Kinda diffuses the projection so I'm not killing the people right in front of me.
     
  13. rangercaster

    rangercaster Friend of Leo's

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    ... as the great inventor Thomas Edison once said, "i would experiment like hell with any materials i could find for free before i spent a dime " ... ok, he didn't really say it, but that was his philosophy !!![​IMG]
     
  14. Bob W.

    Bob W. Tele-Meister

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    I have tried both the Beam Blocker and the Jay Mitchell foam donut in my Fender DRRI. The foam works much better at taming the high end beaminess without adding the coloration due to multiple short reflections (comb filtering effects).

    Here are some measured results, using pink noise and an RTA:

    [​IMG]
    [​IMG]
     
  15. BluesOwl

    BluesOwl Tele-Holic

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    I've tried both.
    Could hear the reflection / comb filter? wierdness to BBs
    Foam did as stated on-axis but I always thought it sounded better w/o the foam

    I'm back to no devices but trying to eliminate beaminess victims with cab. placement.

    Tilting back or amp stand puts the "on-axix" where you want it but can rob bass freq.s

    I'm using a 2x12 cab. now (plenty o' low end) so tilting back still has enough low end retained. And then clock the cab. around so everybody (audience & stage members) is off axis.

    having to choose, I would go with the foam at 1/2" thick and as soft as McMaster-Carr will sell at that thickness.
    Seems that you may be forced to get white vs. charcoal color at some spec. levels...but the white could be dyed
     
  16. strat a various

    strat a various Friend of Leo's

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    I've made my living most of my life playing Fender amps through mostly JBL speakers, so I've dealt with "beamy-ness" and focused projection issues since the 70s ... by tilting the amp back on it's legs. All my Fender amps and cabs have tilt-back legs. I adjust the treble to my ear on the stage, walk out front with long cord or wireless, all is well.
    In thousands of gigs big and small, this has worked fine. High ceilings, low ceilings, "hard rooms, "absorbent rooms", outdoors, doesn't matter.
    In my experience, it's easier for the engineer to mic a speaker with no beam-blocker or doughnut, so I figure a way to tilt whatever I'm playing through. Works for me.
    One thing I've noticed about some of my really old amps, like my little Kamico from the late 40s. The old-style baffle common in vintage amps, with a cut-out composed of several slots (or four quarter circle holes in some cases) make an excellent beam-blocker.
    I like these old fashioned baffled amps for small Jazz clubs where the audience is right in front of you.
     
    Dan Spiffy Neuman likes this.
  17. srolfeca

    srolfeca Tele-Meister

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    Different strokes for different folks...

    I can see using the foam donut if you don’t like your amp’s top end (ie; a stiff, spiky sounding DRRI). It certainly tames the highs.

    But I love the complex harmonics coming off my 5E3, and the filtering effect of the beam blocker seems to preserve them, as well as spreading them over a wide area. I’ve put them into 1x12’s for various people, and they’ve all been happy.

    Never tried them on a multi-driver cab, though. That would be one heck of a complex dispersion pattern, combining the comb filtering effect of the beam blockers with the natural comb filter and beaming effects of a 4x10 or 4x12...
     
  18. Salsg

    Salsg Tele-Meister

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    I've tried the beam blockers, the fizzy lifters and the foam.
    Foam works best for me. It evens out the treble all over the room.
    The other changed the tone which I did not like
     
  19. alnicopu

    alnicopu Friend of Leo's

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    This^^^. Take care of it at the source. Find the right speaker that works best or improve on the overall ciruit. There isn’t always one magic bullet. Took me a while to find the right one, to my ears, for my Princeton Reverb clone. Mine is one from Muchxs so it already had all the circuit deficiencies addressed. All I had to do was roll a few speakers.
     
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