Members Guitin Better Posted July 23, 2007 Members Share Posted July 23, 2007 Okay, I'm trying to figure out how to put together a poor man's PA system. This weekend a fabbed up some cables to take the 1/4" jacks on my guitar amp to the screw terminals on a pair of stereo speakers that I had laying around. I used standard speaker wire (i.e. no shielding) for the cables. The sound was okay at low volume but when I turned it up at all there was a lot of "crackling" (for lack of a better way to describe it). Am I overdriving the speakers? Are the cables I cobbled together to blame? Is it a problem with the amp? Looking for any idea what the problem might be. Link to comment Share on other sites More sharing options...
Members jwlussow Posted July 23, 2007 Members Share Posted July 23, 2007 You are about to (or already have) blown the speakers. This is one of those posts that I hope is just a joke. If not, you really need to read a little about PA setup and power handling. Did you just cut one end off the cable and attach a 1/4" connector on the other end? Not too easy to screw that up unless you have wires touching that shouldn't. What size drivers in the stereo speakers? Link to comment Share on other sites More sharing options...
Members Guitin Better Posted July 23, 2007 Author Members Share Posted July 23, 2007 Not a joke . . . I soldered some 18 gauge speaker wire to a 1/4" plug to plug into the outputs of my amp. The other end went to the screw terms of the speakers. The amp is a 50 watt guitar amp. The speakers have 8" drivers and are rated for 75 watts. Link to comment Share on other sites More sharing options...
Members jwlussow Posted July 23, 2007 Members Share Posted July 23, 2007 I guess the main difference between "recorded" music and the guitar is the dynamics that take place. No real need for a limiter on a stereo system but you should limit a live system. What kind of condition are the drivers in? Are there rips or fraying on the cone itself? How old are they? Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted July 23, 2007 CMS Author Share Posted July 23, 2007 Home stereo speakers are typically way overrated for power handling. I'd bet those 75w speakers will handle maybe 20 watts. Another problem is that the crossover networks will also fail with any 'real' power applied. Yet more trouble; most are terribly inefficient...where you expect 96dB for a PA speaker, most home stereo models are rated in the 80's, so you need to apply gobs of power (that they can't handle) to get the same output you'd normally expect from a PA. Link to comment Share on other sites More sharing options...
Members Guitin Better Posted July 23, 2007 Author Members Share Posted July 23, 2007 I guess the main difference between "recorded" music and the guitar is the dynamics that take place. No real need for a limiter on a stereo system but you should limit a live system. What kind of condition are the drivers in? Are there rips or fraying on the cone itself? How old are they? The cones are in good shape but they are old (replaced 10 years ago??). One thing I did notice is that I heard the crackling sound mostly when I would strum fairly hard. Link to comment Share on other sites More sharing options...
Members Guitin Better Posted July 23, 2007 Author Members Share Posted July 23, 2007 Another problem is that the crossover networks will also fail with any 'real' power applied. When you say "fail" do you mean permanently or just fail to do the job with the current signal? I'm trying to determine if I have done some real damage or not. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 23, 2007 Members Share Posted July 23, 2007 Most guitar amps are designed to drive a single full range driver and there is a fair amount of high freq. boost in most amp's circuitry. This will sound very harsh and the disrortion will sound particularly crackly and nasty when reproduced by a 2 way speaker... especially one that is "home audio" oriented. Link to comment Share on other sites More sharing options...
Members moody Posted July 23, 2007 Members Share Posted July 23, 2007 Essentially what people are trying to say is that home stereo speakers are not designed to reproduce live music. It is likely that they are already fried even if they still work at low volume. In addition, ratings are way different between the PA world and the home audio world. I have seen computer speakers that plug into a 7.5 volt supply being rated as 1500 watts. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted July 23, 2007 CMS Author Share Posted July 23, 2007 When you say "fail" do you mean permanently or just fail to do the job with the current signal? I'm trying to determine if I have done some real damage or not. I've seen crossover capacitors fail, so the tweets and mids get a full range signal, and they last about a minute after that happens. Link to comment Share on other sites More sharing options...
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