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Bill Fitzmaurice

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Everything posted by Bill Fitzmaurice

  1. The wavelengths that a port produces range from 12 to 25 feet. That makes an obstacle some 2.5 feet wide, as in a speaker enclosure, invisible to them. They go around it as if it wasn't there. Where the cone radiation is concerned those wavelengths also go fully around the cab, in the opposite direction, up to where the enclosure baffle is one wavelength in dimension. 2.5 feet is one wavelength at 450Hz. That explains why when you walk behind the cab, or when a drummer is behind the cab, the lows and midbass are still heard, but the mids and highs aren't. If your drummer isn't in front of the cab and wishes to hear your mids and highs and you have two cabs the best placement is to stack the cabs, with the bottom cab aimed at the drummer.
  2. FWIW I use front porting on most of my designs because most people buy with their eyes, not their ears. How a rear firing port works as well as front firing can be better understood if you consider the case of sub woofers, which operate within the same frequency pass band as ports. SOP for those in the know is to aim them at a wall, or a corner. They work better that way than they do facing away from the wall or corner.
  3. Google 'omnidirectional'. Not only is port radiation omnidirectional, cone radiation is as well up to about 200Hz. A port output can be choked off if the port is placed tight to the wall, but even an inch or two of space will eliminate that. Without a doubt you may hear a difference between front and rear ported, but it's not due to the port location.
  4. Port placement doesn't matter, as the radiation pattern from a port is 360 degrees. What does matter is the size of the enclosure. Larger enclosures go lower and louder. In most cases the reason for putting ports on the back is that the enclosure is too small to fit them on the front. Boom is also typical of too small enclosures, and it has nothing to do with port placement either.
  5. In order to find drivers with similar specs to the Aggy drivers one must have the specs of the Aggy drivers. In order to find drivers with different specs that still work well one must have the complete dimensions of the cabinet interior, including the port if there is one. Having a 4 ohm load complicates matters, as you'd have to use either 4 or 16 ohm drivers, which limits driver choices.
  6. Ampeg uses a 24v aircraft bulb. As for the need to replace it, it's either functional or it isn't. In general crackling from a tweeter is caused by insufficient crossover slope, which results in over-excursion of the diaphragm.
  7. Or B&C, 18Sound, Fane, Oberton, Precision Devices. There's no reason to fixate on Celestion, unless it's a vintage Greenback.
  8. The O15 and O15TB are the same speaker, different shape. Ideal T/S specs with a +/- 10% tolerance for the woofer are Fs 40Hz, Qes 0.4, Qms 7.0, Vas 160L, Xmax 8mm or more. The midrange is a 6.5 inch closed back, maximum Fs 400Hz, the HF driver is a 1" throat horn loaded, maximum Fs 2.5kHz.
  9. My cabs suit drivers that have specs that fall within the range the cabs were designed to work with, not a brand. Drivers that have those specs are made by at least 20 manufacturers, Celestion among them. I use and recommend Eminence because most of my customers are in the US, and Eminence is by far the best selling and most readily available driver in the US, and the best priced as well, being assembled in the US. In a practical size 2.5 cu ft cab sensitivity at 38Hz is an unusable 82dB. To get a useful sensitivity, say 90dB at 38Hz, would require an 8 cu ft cab.
  10. I wouldn't use the BN15-400X. The high Qes will give boomy midbass response and weak lows, the 4mm xmax limits usable power to 200w. You can certainly use a Celestion driver in my designs, but as is the case with any driver brand the T/S specs have to be compatible. One of the prime rules of speaker design is don't start with the driver. Start with the intended box size and frequency response, then choose a driver that works in it.
  11. If there's any benefit. Even with guitar with passives you can get the best possible combination of low capacitance and percentage of shielding with cable that's perhaps a pound per meter. Any perceived improvements beyond that price range can be attributed to confirmation bias.
  12. Probably a typo. I do find the reviews to be amusing, especially this bit: The info sheet which is included in the package says that these cables need to be used for some time before their full sound potential is achieved. I found that interesting and I think it makes sense ...Anyone foolish enough to believe that nonsense deserves to pay four times what it's worth. He must be a guitar player. 🙄
  13. In truth an instrument cable can make a difference in the sound with passive pickups. A high capacitance cable will roll off the highs. However, high price doesn't guaranty low capacitance. Some years ago Monster created a very expensive instrument cable that had such high capacitance that it was horrid when used with guitar. They never should have brought it to market at all. But they did anyway, making lemonade out of this lemon by labeling it as a bass specific cable, and then making their usual outrageous claims for it. In this case they said it gave better lows. It might have seemed that way, but in reality it killed the highs. Someone playing flats with buckers might have never noticed. The Ox and Jaco would have, moments before they binned it. The Vovox look OK, but they're ludicrously overpriced.
  14. With only 300w on tap the cable and connector demands with an SVT-CL are minimal. With a 1 meter run 16ga/1.3mm is sufficient. You may use a heavier gauge, but it won't work any better. 1/4" connectors are sufficient as well. Speakon are more secure, but offer no electrical advantage with the relatively low voltage and current that the SVT is capable of. I can't see any advantage to spending more for a cable than you would for a set of strings.
  15. The PXB250 is a 250Hz low pass filter, which you'd be hard pressed to find a use for. That probably explains why he had it kicking about.
  16. Crossovers are optimized (or should be) for use with specific drivers in specific enclosures. You might find someone in need of the PXB250, the other is a pig in a poke.
  17. Get a different doctor. Beer isn't the culprit as much as the food that's usually consumed with it. https://www.npr.org/sections/thesalt/2014/12/31/374187472/if-youre-toasting-for-health-beer-may-be-a-good-bet https://www.brook.health/blood-sugar-and-beer/ All things in moderation. Besides, if you give up all the things that make life enjoyable you don't live any longer. It just seems that way.
  18. Where Canadian brews are concerned I prefer Moosehead, although sometimes the antlers hurt. 🙄
  19. Using the Ric bass as a guide that cab is around 50 inches high, and maybe 40 inches wide. The Bassman 100 4x12 was 40 inches high, 30 inches wide.
  20. It doesn't have the trim that the Traynor did. https://reverb.com/item/6168701-traynor-yc-810-big-b-8x10-cabinet-1971-pickup-only It's also too wide to be an Ampeg V9.
  21. Looks like Fender cabs, but the bottom would have to be a 4x15 to be that large, and Fender never made one. Marshall did, but they didn't look like that.
  22. The Declaration of Independence was declared on July 2. At that point the Continental Congress adjourned to nearby City Tavern, where they proceeded to go on a bender. It wasn't until July 4th that they sobered up enough to approve the final draft, and that's why it says ' IN CONGRESS, July 4, 1776' at the top. After that Congress went out tavern hopping again while 200 copies were printed up for distribution. All of the members didn't actually get around to signing the original until August 2. Then they went out drinking again, mostly rum, all of it smuggled into the country.
  23. Dreadful doesn't begin to describe it. Healing will only begin when those responsible who are still living are brought to justice.
  24. They go north/south as well. For instance, 'Oh Canada' is always played in the key of 'eh'. Hoser.
  25. We haven't drunk tea in Boston since 1773. We drink Sam Adams beer, the colder the better! 😊
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