My Ampeg B100R is making a flabby flapping noise from the ports

Discussion in 'Amps [BG]' started by Bass 45, Jan 1, 2013.


  1. Bass 45

    Bass 45 Supporting Member

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    Jun 23, 2011
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    Tempe, Arizona
    When I play lower notes through my Ampeg B100R, there is an audible flapping noise coming from the air pressure as it exits the rear ports. It is audible at all volume levels.

    The amp sounds fine running an external cab - and the problem remains with a different speaker installed in the combo.

    Everything is original and it sounded fine a couple of weeks ago and I have made no changes since.

    The only thing I can think of at this point is more baffling insulation could help? But why the sudden change?

    Has anyone else experienced this?

    Any input would be appreciated. Thanks
  2. AstroSonic

    AstroSonic Supporting Member

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    Check tor something lose in the speaker enclosure, like a piece of acoustic insulation, a bass port tube or the panel next to the amp. Give each panel making up the speaker enclosure a good rap with your knuckles. It is possible that a glue seam has broken lose.

    Good luck.
  3. JimmyM

    JimmyM Supporting Member

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    Loose piece of insulation inside the cab would be my first guess. That stuff gets to flapping and that can happen. And I don't know what the inside looks like, but it never hurts to have all the walls except the baffle lined. I got some 1" thick Nu-Foam polyfil sheets at the local fabric/crafts store for cheap that does well if you need a recommendation for stuff that works but isn't expensive.
  4. Bass 45

    Bass 45 Supporting Member

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    Thanks for the tips guys. I will get a chance to look at it again tonight.
  5. Lync

    Lync Supporting Member

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    Did you try reaching into the ports to make sure the cardboard port tubes were still attached and not rolling around the bottom of the amp? That happened to me and I had to refit them over the plastic trim on the back of the amp.
  6. Bass 45

    Bass 45 Supporting Member

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    Yes - I had it apart when I tested it with another driver. The cardboard tubes are in securely (possibly glued in).

    I also did the knuckle test around the cab and it seems very solid. I think adding more insulation will be my next move.


    Thanks!
  7. Lync

    Lync Supporting Member

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    I find that when I push mine it gets "warbly" down low. I just attribute that to I am exceeding the limits of the amp.

    I wonder if there is a better speaker for the amp to give it a bit more low end?

    It will be interesting to see if the fill material tightens it up for you.
  8. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    These sort of problems can be difficult to resolve. Like Jimmy, my first thought is that some insulation or the amp itself is loose and is vibrating.

    By changing the driver you narrowed it down to the cabinet. Adding some foam would stiffen the lining, at least for testing. Another possibility is that although the port tubes are glued in place, there might be a resonance. You could try pressing a dowel or something similar against the inside of the tube to see if it dampens any vibrations. Pressing too hard can damage it so it has to be done carefully. If the cabinet wood has dried, it is possible that the amp's mounting screws are loose. If tightening them doesn't help, pulling the amp out and plugging the area of the faceplate with foam would remove it from the equation.
  9. AstroSonic

    AstroSonic Supporting Member

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    Make sure that the speaker wires are not touching the cone. The speaker should be mounted so that the connection terminals are oriented downward, toward the bottom of the enclosure.

    Check the grill frame and grill.

    When one of the port tubes fell off, I glued both on with silicone glue.

    Check that the plastic port tube holders are securely screwed onto the back of the cabinet.

    I found that stuffing the cab with damping material will tighten the bass a little, but take some of the growl out of the tone. I opted to keep the growl.
  10. B-string

    B-string Supporting Member

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    If is also possible with full throw from the broken in speaker that you are getting port chuf. This would be a design short coming on the cab and turning down the bass will help.
  11. bgavin

    bgavin Supporting Member

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    The vent output is excited at the cabinet tuning frequency, which is within the lower note range of most basses.
    Play an octave up, and the problem will disappear because you are away from the resonant frequency.

    At resonance, you have a slug of air oscillating in the port tube(s).
    If you are playing at high volume levels, one cause can be "chuffing".
    This is the audible noise of air moving in the ports at high velocity.
    Play the same note at a much lower volume, and listen for the noise.
    If the noise remains, look for mechanical causes as mentioned above.

    If the noise is gone at low volume, chuffing is the likely cause.
    Chuffing is excessive air velocity in the port(s).
    It is a design problem, where the port area is too small for the velocity in use.
    Keep a minimum of one port diameter (total) distance between the end of the port and any obstruction.

    OP, you mention this is a new noise.
    IMO, the cause being a shift of internal insulation or other component over the last few weeks.
  12. stiles72

    stiles72

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    Does the flapping sound remain when you remove the port flanges and tubes altogether? If you remove both of them and it remains, perhaps you can see where it is coming from. With my B-100R, usually the culprit is a tube fell off and is rolling around blocking the port- but you have eleiminated that possibility. Hopefully it's just some insulation.
  13. Bass 45

    Bass 45 Supporting Member

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    Thank you all for your input.

    I had not heard the "chuffing" term before - but that sounds like what it is I am dealing with.

    I tend to prefer a lower then average eq setting and I mostly play an Ampeg AMUB-1 Scroll Bass which goes a little deeper than your average P-Bass.

    The sound is occurring at low C (E string - 8th fret - not as apparent on the A string) and lower. The cone movement and port tuning don't seem to be in sync at that point.

    I am working on another project today - but when I get a chance I will try it without the port tubes and then with more insulation (the stock insulation is not loose).

    I had already tried blocking the ports (I laid the amp on it's back on my bed) and the noise was gone - but so was the deep low end that I prefer.

    I had owned a B100R around 1999 - 2003 and I did not have this problem. The one I have now is a recent purchase - but it also was made in '99.

    I would like to add that I am satisfied with the low end I get out of my B15R's stock cab and my now sold PF115HE - so I am not going that low:)
  14. 1958Bassman

    1958Bassman

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    Oct 20, 2007
    I would bet that this cabinet isn't designed to be used with a 5 string bass. When you send frequencies to the speaker and the port is tuned higher than the notes, the speaker acts like it's in free air and if you keep doing this, you'll blow the driver. If you remove the ports, the cabinet's response won't even be close to what you want/need for a 5 string bass.

    You didn't have the 5 string when you used the B110R, did you?
  15. AstroSonic

    AstroSonic Supporting Member

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    You may indeed be hearing chuffing (vent turbulence) if you are playing low notes at relatively high spls. The plastic port flanges are flared to minimize chuffing, but the interior port terminations are sharp. Get a pair of 3 inch 'inside' port flares from PE. That will change the port tuning frequency a little, but not significantly. That should put any chuffing to rest.

    "The cone movement and port tuning don't seem to be in sync at that point."

    If I understand you correctly, that's the way it should be. At the port tuning frequency, the port air velocity should be maximum and the driver motion should be minimum.
  16. Bass 45

    Bass 45 Supporting Member

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    Thank you all so much for the great advice.

    I have played through the amp more and have realized I was probably trying to play too loud and low for this combo's capabilities. I had bought this amp just for home and rehearsal use - but I picked up a New Years Eve gig in San Diego and I was asked to bring my smallest amp as the stage would be tiny. The stage was small - it was just big enough for the drums and my B100R with the casters pulled and the front feet hanging off of the front edge. Myself, the guitar player and the banjo player were standing among the crowd which were gradually packed in wall to wall (we were playing with our headstocks pointing up). As the room filled in, we kept turning up and I neglected to compensate by turning down the bass knob.

    The amp actually still sounds quite good to me if I need to go louder while turning the bass knob down to stay within' the combos limits.

    I am interested in trying the inner port flange as Astro suggested and maybe (eventually) an Eminence CA154 driver and then maybe I'll get this combo out of the house more.

    Thanks again all!
  17. JimmyM

    JimmyM Supporting Member

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    I don't think I could deal with a driver that only does 3k on the top end. Pretty sure the tweeter picks up at 4k so that would leave a response hole. I'd go Beta or Delta myself if you're looking for a speaker more tolerant of cranking harder that sounds right in Ampeg cabs and won't break the bank. The speaker in it is apparently rated for 150w thermal, which isn't bad and likely lighter than a replacement, but fartout power handling is likely going to be a little less than the head can deliver cleanly. Will the difference add up to a hill of beans for available volume on a gig? That I couldn't tell you but I wouldn't be looking for miracles.
  18. daveman50

    daveman50 Supporting Member

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    It's not a 5-string bass. It's a 4-banger. See here: http://www.xstrange.com/amb1.html

    He's referring to the C on the E string.
  19. stiles72

    stiles72

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    Location:
    Albany IL
    Rich - Do you use the Ultra Lo and Ultra Mid switches ont he B-100R? When I use my B-100R, I go for a pretty deep sound as well regardless of whichever bass I'm running through it (P-bass, T-bird, Baby Bass) and I run with both the ultra lo and ultra mid engaged, and my bass knob is always at 3:00. Just curious if trying different settings with those switches changes things for you.
  20. Bass 45

    Bass 45 Supporting Member

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    Good point about the frequency range - but I am limited to 4 ohm options to match the original. Also, there is no tweeter in this model - so it is important to get some upper frequency response from the woofer.

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