Members dachuckster Posted March 10, 2007 Members Share Posted March 10, 2007 Sounds like dumb question, problem is i have a marshall Mg series practice amp w/ a 12" speaker. It is a four ohm speaker (amp at 4 ohms) and needs replacement. I have several 8 ohm speakers and have heard of car audio installers using caps or resistors on speaker connections to increase or decrease the load an amp sees. Any help will be appreciated. Link to comment Share on other sites More sharing options...
Members !HxC! Posted March 10, 2007 Members Share Posted March 10, 2007 I'm pretty sure you can use a 8 ohm with a 4 ohm load and it wont fry. but an 8 ohm load with a 4 ohm cab...bad news. you can push uphill, but not down. I read that in a GW a while back (I knew they'd come in usefull for something...) Link to comment Share on other sites More sharing options...
Members 496dart Posted March 10, 2007 Members Share Posted March 10, 2007 The output chip in the MG series is vulnerable anyway--i would put a 4 ohm back in it. Resistors are not a reactive load like a speaker. Link to comment Share on other sites More sharing options...
Members ruger270man Posted March 10, 2007 Members Share Posted March 10, 2007 you can use the 8 ohm speaker, but it will be seeing half of the wattage. you're better off getting another 4 ohm speaker Link to comment Share on other sites More sharing options...
Members 496dart Posted March 10, 2007 Members Share Posted March 10, 2007 half the wattage, from 4 to 8 ohms. ? .. man, you are way off bro.goodnight. Link to comment Share on other sites More sharing options...
Members JohnH Posted March 10, 2007 Members Share Posted March 10, 2007 It is safe to use an 8 Ohm speaker on a solid state amp to replace an 4 Ohm. You'll get less output. See how it works with the speaker that you have, you may decide its OK. There's no point in adding resistors in this case. I have a little 10W MG10, which has an 8 Ohm speaker. I often run it through a 16 Ohm cab and its fine - and still loud. The above would not be true if it were a tube amp. Then you'd need to match the Ohms. John Link to comment Share on other sites More sharing options...
Members HKSblade1 Posted March 10, 2007 Members Share Posted March 10, 2007 It's a practice amp so I guess that means NOT loud. You're good with an 8 Link to comment Share on other sites More sharing options...
Members GCDEF Posted March 10, 2007 Members Share Posted March 10, 2007 half the wattage, from 4 to 8 ohms. ? . . man, you are way off bro. goodnight. No he's not. Read up on Ohm's law. Link to comment Share on other sites More sharing options...
Members 496dart Posted March 10, 2007 Members Share Posted March 10, 2007 talkling about the 1/2 the wattage statement. Link to comment Share on other sites More sharing options...
Members JohnH Posted March 10, 2007 Members Share Posted March 10, 2007 The half wattage statement is approximately correct. (the approximate part is due to a few other factors such as teh power supplys ability to deliver current - you may therefore get slightly more than half) The amp can produce a certain voltage output, dependent on not clipping to the power supply levels. Power = voltage x current = voltage x (voltage / resistance) So for a given max voltage swing from the amp, doubling the resistance halves the power. Its only a 3db drop in audible loudness, which is not all that much in practice. here endeth the lesson John Link to comment Share on other sites More sharing options...
Members dachuckster Posted March 11, 2007 Author Members Share Posted March 11, 2007 Thanks fellas!! Did not mean to stir the pot!,...but made me go get a bud light and watch!!!!! Link to comment Share on other sites More sharing options...
Members dachuckster Posted March 11, 2007 Author Members Share Posted March 11, 2007 Thanks guys!!! Did not mean to stir the pot a little!! Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 11, 2007 Members Share Posted March 11, 2007 half the wattage, from 4 to 8 ohms. ? . . man, you are way off bro. goodnight. you're way off. that's why amps are rated at a certain wattage with a certain impedance. if you double the impedance, you half the wattage, and if you half the impedance, you double the wattage.there is a lot of debate about the pros and cons of impedance mismatching. all i can say is, try what you have...if you like it, keep it. if you think it sounds bad, (or worse than before) get an exact replacement.tube amps can take impedance mismatches just as well as solid state...if not a bit better. just make sure that the cab impedance is more than the load selector on the amp...a 16 ohm cab will not harm an amp set to 4 ohms. Link to comment Share on other sites More sharing options...
Members ruger270man Posted March 11, 2007 Members Share Posted March 11, 2007 half the wattage, from 4 to 8 ohms. ? . man, you are way off bro. goodnight. I used to install car audio, I'm pretty sure that doubling the impedance draws half the wattage load. Link to comment Share on other sites More sharing options...
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