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Bill Fitzmaurice

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Posts posted by Bill Fitzmaurice

  1. On 07/05/2022 at 04:28, Gottastopbuyinggear said:

    somewhere along the chain there’s likely to be some high pass filter capability, which shouldn’t affect keys or guitar detrimentally but will protect speakers from the low bass frequencies.  I’d guess somewhere around 80Hz would be a good starting point?

    IME the best FOH sound men high pass the bass somewhere between 60 and 80Hz, and this is with multi-million dollar pro-touring systems. This does the best job of getting tone through the PA that approximates the tone through the backline. The worst sound men don't high pass, resulting in tone that more closely resembles teenagers $5k subs in their $500 cars than electric bass.

    • Like 3
  2. 7 hours ago, neepheid said:

     When I feel I need a little help, I use the amp's DI to go through the PA we have for a bit of extra coverage, still using the amp for the majority of bass volume.  I'm sure someone will be along soon to tell me what a terrible idea that is.

    It's a very good idea, when done correctly. While the stage rig will cover the room with the lows very effectively the midrange and high frequency dispersion is pretty bad. Put mids and highs in the PA for dispersion, pull back the lows on that PA channel so as not to overdo those. The same applies to the drums, keys, even guitars. The PA should be providing a balanced mix throughout the room. The problem lies with bone headed guitar'd players who think that they need to play loud enough to blow out candles at 30 meters. PA isn't about volume, it's about dispersion. Most guitar players can't even spell dispersion, let alone understand the need for it. 🙄

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    • Haha 5
  3. 5 hours ago, uk_lefty said:

    I am quite certain that for some gigs and venues coming up this will not be enough bass output, so pumping up the amp as I have done in a nice big room, would be intolerable on stage but maybe ok out front.

    It's the rare room where the bass isn't louder out front than it is on stage. On stage there are boundary reflection sourced cancellations, out front there aren't.

    • Like 1
  4. Just to make it more confusing: We loudspeaker engineers don't use watts, we use volts. Power delivered varies with current, current varies with impedance, and the impedance of a speaker isn't constant, it varies with frequency. An average 8 ohm rated speaker will have an actual impedance between 5 and 50 ohms, with the impedance being different at every frequency. At equal volume your amp can be putting out 200W at 50Hz but only 20W at 100Hz. We use volts because they're constant into any impedance load, allowing us to accurately calculate a speaker's mechanical limit. 


    And 1+1 doesn't equal 2. Take a look at Ohm's Law and you'll see why. For instance, 28.3 volts into 8 ohms is 100 watts. You'd thank that 56.6 volts would be 200 watts, but it's actually 400.

    • Like 1
  5. On 12/04/2022 at 16:46, PigBass said:

    There is a conversation to be had about the fact that the amp can potentially deliver the full 500W into an 8 Ohm load using this setting, and the cab has a max handling limit of 400W.

    The more pertinent conversation is the fact that said 400W rating is thermal. The mechanical limit is perhaps half that. The majority of posters in the thread appear to be unaware of thermal versus mechanical capacity. The good news is that it will sound quite awful if you exceed the mechanical limit.

    • Like 2
  6. It indicates that the cab is inadequately braced on the inside, if at all. Aside from being an annoyance the energy expended vibrating the cab walls is energy not creating sound, or worse, it creates unwanted sound. This is an example of a well braced cab:



    You may not be able to retrofit that extent of bracing, but even a single brace that connects the center of opposing panels has the same effect on vibration reduction as doubling the thickness of the panels.



    • Like 5
  7. 3 hours ago, ossyrocks said:

    Does anyone gig a Bassman 50, I’m genuinely interested?

    I did, from 1965-1972. I could see using one today in the studio, or for small club gigs, but that's all. As far as vintage valve gear is concerned the Ampeg V4B is considerably better.

    • Like 3
  8. A watt is a watt. What differs with valves is that they can naturally compress the signal peaks, subjectively making them seem louder. You can accomplish the same thing more or less with SS using a compressor, but since that occurs before the power output stage rather than in the power output stage the effect isn't quite the same.

    • Like 7
  9. 36 minutes ago, Vin Venal said:

    I understand the theory of using a clean boost to drive a tube amp harder, thus getting more distortion without too much more volume.

    That only works if you have a method of attenuating the amp output, with a device like a Power Soak. You wouldn't do that with any SS amp, since the mechanics of how tubes and SS distort are very different. As for the Dark Glass, what's shown inside the dotted lines is in essence a distortion pedal.

    • Like 1
  10. That depends on where it's low passed. I suspect Alex did so fairly high, to eliminate comb filtering. Typically it would be done where the center to center distance of the drivers is one wavelength. With two tens that's in the vicinity of 1.1kHz. If it's done at too low a frequency the lost midrange output could be problematic. It would affect personal monitoring, as the driver that's full range should be as high as possible. The boundary reinforcement off the wall shouldn't be affected.

  11. 4 hours ago, Dad3353 said:


    Always..? o.O




    :lol: :P

    Yes. The dispersion angle in the mids is inversely proportional to the width of the radiating area. As shown that area is twice what it would be when rotated 90 degrees.


    3 hours ago, alexa3020 said:

    I didn't think you were suppose tilt  cabs of the floor - something to do with floor coupling??

    Can someone with technical knowledge enlighten me please?


    Edit - I can see from a bit of googling, I've got that completely the wrong way round!

    Boundary reinforcement from the floor happens when the lowermost driver is less than 1/4 wavelength away. At 200Hz that's 1.4 feet. At 100Hz it's 2.8 feet. There are instances where raising it more than 2 feet or so can be beneficial, as in the case of a boomy cab or stage where you want the lows augmented but not the midbass that produces boom. These rules also apply to boundary reinforcement off the wall behind the cab. Very often what makes for the best sound is the same thing that makes for the best real estate: location, location, and location.

    • Like 2
  12. On 19/04/2022 at 17:37, Downunderwonder said:

    You could always turn the cab up tall.

    You should always turn the cab up tall. It doubles the midrange dispersion angle.

  13. 1 hour ago, BassAdder27 said:

    Yes like that but not tilted back ( head would fall off ) 

    With a bit of ingenuity you can find a method of securing the head. In my case I attached two inch high feet to the front edge of the amp that hang down far enough to hook over the front of the cab. Where hearing what you're doing is concerned, especially on a tight stage, tilt back is even more effective than lifting.

    • Like 1
  14. On 06/04/2022 at 14:17, Smiles said:

    Hi guys has anyone had experience with the Ampeg svt 610 hlf 

    As they’re only a 600 watt cab

    Ampeg is conservative with their power ratings. Where farting out is concerned that happens when the drivers run out of excursion. There are many tens rated at 250w that have no more excursion capability than the 100w rated Ampeg ten.



    I would think that stacking two 2x10 cabs vertically might be a good idea if is all about having something audible at ear level. That would actually be a taller stack than a 6x10 and much more portable, easier to move and take up less space in the car/van.

    +1. The 410 is the poster child of how not to build a bass cab, as neither you nor the audience will hear it anywhere near as well as those same four tens vertically stacked in a pair of 210 cabs.

    • Like 1
  15. 1 hour ago, Al Krow said:

    This is what confuses me: there's a massive "FRFR" thread where bass players swear by a single 12" PA speaker being perfectly adequate as their sole backline without a sub.

    It depends on the twelve. One that will do this job isn't going to be had on the cheap, nor will it deliver good lows when stuffed in a too small enclosure, especially when said enclosure is up on a pole in front of the stage as is required for PA, which means it won't get ground plane or rear wall low frequency reinforcement. That results in as much as a 12dB reduction in low frequency output compared to on or close to the floor and close to the rear wall. 12dB is the difference between one twelve and four twelves. The concept of boundary reinforcement, like Hoffman's Iron Law, should be just as familiar to bass players as are the notes E-A-B-D. 

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