Moderators isaac42 Posted June 11, 2015 Moderators Share Posted June 11, 2015 I found a used 4 space rack for sale. Bought it. Today I installed my Peavey T. B. Raxx preamp and a Crown XLS 1500 amp in it. It's smaller, lighter and more powerful than my previous rack system. Instead of 110 watts RMS into 8 ohms (160 into 4), I now have 300 into 8 (525 into 4, 775 into 2). So now I should have squeaky clean power right up to the point that the speaker explodes! And that's just one channel. I could also bridge it and get over 1000 watts into 8 ohms. Or I could use the internal crossover and power a midrange cabinet. I definitely should use the high pass filter to keep subsonics out of the speaker, but I haven't done that yet. Link to comment Share on other sites More sharing options...
Members DeepEnd Posted June 11, 2015 Members Share Posted June 11, 2015 Congratulations and Happy New Rack Day. I've been a fan of Peavey stuff for years and Crown is great gear. Lighter and more powerful. Can't beat that. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 11, 2015 Members Share Posted June 11, 2015 You can biamp a stereo head and use a 2 way electronic crossover to drive two different cabs. If you have say 10's and 15's you can find the specs on those speakers and find a good crossover point between the two and have your mids push the smaller speakers and lows feed the subs. The crossover will act as a tone control to some extent as you sweep the crossover point. between that and the volumes you can get an optimal cab resonance for each cab. Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted June 11, 2015 Author Moderators Share Posted June 11, 2015 As I wrote above, the amp has a built in crossover, and I'm already considering using it and adding a midrange cabinet. Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted June 12, 2015 Author Moderators Share Posted June 12, 2015 More bass than the Pyramid PA1000, which surprised me. I expect power amps to be transparent, unless they're run beyond their limits. Maybe not guitar amps, but PA amps, definitely. A little tweaking with the tone controls and it sounded fine. Sounded great at the gig this evening. Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted June 17, 2015 Author Moderators Share Posted June 17, 2015 Used it again at an outdoor festival gig. Cranked it up. a little too much, as it turned out, and the thermal overload kicked in, shutting down the output momentarily. Turned down a little, and the problem was solved, with hardly any loss in volume. Just as well, as it seems I was a bit too loud, anyway. Wish someone had told me. Sounded awesome, though. Link to comment Share on other sites More sharing options...
Members DeepEnd Posted June 17, 2015 Members Share Posted June 17, 2015 "A bit too loud"? Granted outdoor gigs need a lot of power but if you were pushing a 300 Watt amp hard enough to shut itself down, you must have been pumping out some serious volume. Glad to hear it "sounded awesome" though and glad you're enjoying your new rack. Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted June 17, 2015 Author Moderators Share Posted June 17, 2015 Yeah, a bit. I heard a recording someone made, and the vocals and bass were quite prominent. Both would have been better blended if they were brought down some. Recording was made by Simon Babbs. I think he's the son of Ken Babbs, close friend of Ken Kesey and one of the original Merry Pranksters. Simon plays in the Portland band Woodknot. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 17, 2015 Members Share Posted June 17, 2015 "A bit too loud"? Granted outdoor gigs need a lot of power but if you were pushing a 300 Watt amp hard enough to shut itself down, you must have been pumping out some serious volume. Glad to hear it "sounded awesome" though and glad you're enjoying your new rack. You need many more times the wattage pushing bass speakers to match the DB level of other instruments running lower wattage amps. The DB scale between low frequencies and high run down hill as you go up in frequency. This is partly because of how our hearing works and our ears being most sensitive in the 1~5K ranges so we don't need as high a DB level to hear those frequencies. Its also because bass speakers are heavy duty and less efficient converting signals into sound waves. The speaker coils are stiffer and need more power to move them. The paper is heavier and has more inertia and many of the bass frequencies are below normal hearing ranges. You pump the same DB level of 40hz and 1Khz into a speaker. You can barely hear the 40Hz even with your ear up to the speaker. The 1K hz on the other hand you'd have your hands over your ears being blasted out. Bass is mostly felt. Playing outdoors can be even more challenging for the bassist because there's no reflection. You can easily wind up cranking the bass too high to make up for the lost reflection. The overloading is heat protection. Many power heads are designed to push full frequency sound. When you're pushing only bass you can overheat heads because there's a much higher need for Current to drive the speakers. What I'd so in Isaacs case is mount the head in a rack case and add more fans that can suck air through that Crown. I have one in my PA rack and when its pushed the fans kick on high speed to maintain the temperature. I've never pushed it hard enough to have the thermal protector to kick in but I do know its there. I have thermal protection in my speakers and if I push them too hard the circuit breakers pop on the speakers before they do on the head. Crown makes great heads, they just aren't designed for 100% bass use. They don't have enough heat sinking and enough air to keep the heat sinks cool enough. If you were pushing full frequency sound you'd meet full wattage with little problems because higher frequencies don't require the same current. PA heads self adjust wattage to the impedance and needs of the load. They aren't fixed like instrument amps. Link to comment Share on other sites More sharing options...
Members DeepEnd Posted June 17, 2015 Members Share Posted June 17, 2015 You need many more times the wattage pushing bass speakers to match the DB level of other instruments running lower wattage amps. . . . . . . What I'd so in Isaacs case is mount the head in a rack case and add more fans that can suck air through that Crown. I have one in my PA rack and when its pushed the fans kick on high speed to maintain the temperature. I've never pushed it hard enough to have the thermal protector to kick in but I do know its there. . . . And yet, Isaac, who knows what he's doing, is the first to say the bass was too loud: That said, a fan or two would be a good idea. A couple of computer case fans would cost maybe $20, less for used ones. Link to comment Share on other sites More sharing options...
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