vacumancsm Posted June 6, 2013 Share Posted June 6, 2013 My audio system has 7 Klipsch speakers and a Klipsch Sub. 3 RVX-42s, 1 RCX-4 center channel, and 3 RSX-5s. I've been using a Denon AVR-3803 to drive the system and it sounds great with no problems. I recently got a great deal on a Denon AVR-4806 and hooked it up to the system and soon blew a fuse in the amp. I took it the a Denon Super Center for repairs and when I got back the same thing happened. The tech there told me to check each speaker with digital ohm meter to verify impedance. I was surprised to find not one speaker with more than a 4.8 ohm reading. The center was only 3.8 ohms. These are supposed to be 8 ohm speakers. Just to remove speculation: These readings are accurate (verified with two separate meters). All connections are correct. I know this amp is WAY too powerful to drive 75watt speakers, but I never attempted to really rip it. The speakers have been driven in moderation for their entire life and not abused. The system works fine with the smaller amp. Now for the questions. What would cause all seven of these speakers to change impedance this way? Is there a cost effective fix available? Why does the AVR-3803 work fine and high end AVR-4806 blow fuses? Any knowledgeable input will be appreciated. I'm probably going to just sell the 4806. I've only got about $350 invested in it if anyone is interested. 100% functional with everything included. Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted June 6, 2013 Share Posted June 6, 2013 What would cause all seven of these speakers to change impedance this way? The impedance didn't change. Klipsch plays fast and loose in how they specify them. Sensitivity is inflated as well. They are more current hungry than you would expect, perhaps too thirsty for the AVR-4806's trough to satisfy. (Seems odd to me, but never underestimate the cost cutting measures taken with AVRs.) Is there a cost effective fix available? An impedance matching autoformer? Nah. You just need capable amplification. Has the 4806 been thoroughly checked to make sure it's fully functional? Sounds like you got it used, so you never know. Perhaps this is why it was such a "deal"? If either of your Denons has pre-outs, you could off-load the amplification. Or simply continue to use your old AVR. You mentioned it "sounds great with no problems." Quote Link to comment Share on other sites More sharing options...
willland Posted June 7, 2013 Share Posted June 7, 2013 They are more current hungry than you would expect, perhaps too thirsty for the AVR-4806's trough to satisfy. (Seems odd to me, but never underestimate the cost cutting measures taken with AVRs.) I doubt that is it. I have been driving an RVX-42 system(3 RVX-42's, 2 RSX-4's) with my mid level Onkyo TX-SR705 AVR for over 5 years with no ill effects at all. The Denon AVR-4806 is the 2nd from flagship AVR from around 2007 with a pretty potent amp section. Must be something going on with the 4806 to keep blowing fuses. Bill Quote Link to comment Share on other sites More sharing options...
vacumancsm Posted June 7, 2013 Author Share Posted June 7, 2013 p>The previous owner had the same problem with this receiver. I took it to the factory authorized Denon Supercenter in Carson CA for repairs figuring they could solve the problem, but its still happening. They have it again right now, but the lady at the counter insists its my speakers. I still can't understand why a decent amp like the 3803 works and the audiophile quality 4806 is so finicky. I'm going to try it out on my other system when I get it back and see what happens. Quote Link to comment Share on other sites More sharing options...
Islander Posted June 7, 2013 Share Posted June 7, 2013 Speaker impedance is not the same as resistance. Impedance is a property related to AC current, which speakers use. Resistance, which an ohmmeter measures, relates to DC current. I'm surprised that the Denon tech doesn't seem to know that. As you've noticed, resistance is a static property of any circuit, while impedance varies with the frequency. You can't test for impedance with an ohmmeter or a multi-meter. The ohmmeter is measuring the resistance of the voice coil, not the overall impedance of the speaker, which includes the crossover as well as the drivers. More info here: http://www.learnabout-electronics.org/ac_theory/impedance73.php This will give you an idea of how complex impedance is: http://en.wikipedia.org/wiki/Electrical_impedance Impedance of a speaker can vary widely across the audio band, sometimes varying from a high of 10 ohms to a dip of 2 ohms. This is not unusual. The "nominal impedance" that's marked on the speaker expresses a rough average of the range of impedance. I'm not familiar with the numbers of voice coil resistances of speakers, so someone with more technical knowledge is welcome to chime in. As for how much power your amp has, relative to the speaker's rating, don't worry too much about it. Most speaker manufacturers nowadays recommend using an amp with double the power rating of the speakers, to avoid overworking the amp, which could then send a clipped signal to the speaker and damage it. Use your common sense and don't turn up the volume so high that the speakers are distorting or making other odd noises and you should be okay. Quote Link to comment Share on other sites More sharing options...
garyrc Posted June 7, 2013 Share Posted June 7, 2013 When testing for continuity, I was surprised to find that both of my Klipschorns had a voice coil + crossover + 20 feet of speaker cord resistance of only "3 something" Ohms. If I remember corredtly, it was 3.2. I know this is not the same as impedance, and remember that the old Khorns of decades ago had impedance that rose as high ar 40 ohms at one point, and had a nominal impedance of 16 Ohms, later changed to 8 Ohms. I assume that the 3.2 Ohm resistance will not require too much from the amp, the way impedance dipping to 3.2 Ohms might. Right? Quote Link to comment Share on other sites More sharing options...
pzannucci Posted June 7, 2013 Share Posted June 7, 2013 My audio system has 7 Klipsch speakers and a Klipsch Sub. 3 RVX-42s, 1 RCX-4 center channel, and 3 RSX-5s. I've been using a Denon AVR-3803 to drive the system and it sounds great with no problems. I recently got a great deal on a Denon AVR-4806 and hooked it up to the system and soon blew a fuse in the amp. I took it the a Denon Super Center for repairs and when I got back the same thing happened. The tech there told me to check each speaker with digital ohm meter to verify impedance. I was surprised to find not one speaker with more than a 4.8 ohm reading. The center was only 3.8 ohms. These are supposed to be 8 ohm speakers. Just to remove speculation: These readings are accurate (verified with two separate meters). All connections are correct. I know this amp is WAY too powerful to drive 75watt speakers, but I never attempted to really rip it. The speakers have been driven in moderation for their entire life and not abused. The system works fine with the smaller amp. The RXV-42 is likely considered an 8 ohm speaker because impedance is averaged. Notice the specs don't say 8 ohm but 8 ohm compatible. Most likely if you are running them without crossing over to the sub at a higher frequency than 80hz, they are getting down in the lower reaches, probably 4-5 ohms. Apparently there is a problem with the 4806 or wattage to wattage, your 3803 has better built amplifiers. BTW you didn't say how loud it was running, what the volume setting was and how hot the receiver was. Even if you have good amplifiers, not having good air flow will cause major problems. Many receivers can drive speakers such as this very well in a 5.1 configuration but this one may not be up to the task in 7.1 Personally I would recommend looking for a 4ohm compatible receiver next time. Many good speakers for H/T do require current. Cheap ones like little square cubes with one driver will not. BUT just about anything running 7.1 will need to be kept cool. Quote Link to comment Share on other sites More sharing options...
superedge88 Posted June 9, 2013 Share Posted June 9, 2013 p>The previous owner had the same problem with this receiver. I took it to the factory authorized Denon Supercenter in Carson CA for repairs figuring they could solve the problem, but its still happening. They have it again right now, but the lady at the counter insists its my speakers. I still can't understand why a decent amp like the 3803 works and the audiophile quality 4806 is so finicky. I'm going to try it out on my other system when I get it back and see what happens. The Denon techs have you on a wild goose chase. They can't figure out the problem, so in their eyes it must be your speakers. Quote Link to comment Share on other sites More sharing options...
vacumancsm Posted July 9, 2013 Author Share Posted July 9, 2013 Wild goose chase wins for the best answer! An extra 200 mile trip through LA traffic but they fixed it right this time. It works great now on both systems. This is the best sounding amp I've ever heard. It is currently running with a full time cooling fan on a 7.1 channel Jamo system. An interesting note however---The Jamo speakers have a 4/8 ohm switch. Most read about 7 ohms in the 8 ohm position and very close to 4 in the 4 ohm setting. I doubt the problem was in any of the speakers though. They all sound great and are working fine. Bottom line is I picked up an awesome piece of equipment and a give away price. Denon and Klipsch make a great team. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted July 9, 2013 Share Posted July 9, 2013 It works great now on both systems. Great! problem solved. Quote Link to comment Share on other sites More sharing options...
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