Rudy81 Posted October 28, 2002 Share Posted October 28, 2002 I am planning a home theater with a pair of Belle's for Fronts, Heresy for Center and Forte's for rear effects. The Belles are 8 Ohms and the Heresy is 4 Ohms. Any problems running this setup on an A/V apmplifier with 100W rating for each of the 5 channels? Thanks Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 28, 2002 Share Posted October 28, 2002 I think you will not have a problem. But the situation may be different than you've been lead to believe. The ratings of the impedance of speakers are often said to be "nominal" meaning, in name only. All of them get to 4 ohms or so at some point in their operating range, typically in the bass. Most amps will handle a 4 ohm load. You may find that these sensitive speakers will reveal the noise floor of the digital signal processor in the HT amp. That is not really an impedance question though. Gil Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 29, 2002 Author Share Posted October 29, 2002 Gil: What do you mean by the noise floor? Quote Link to comment Share on other sites More sharing options...
jtkinney Posted October 29, 2002 Share Posted October 29, 2002 I thought the Heresy's were 8 ohm nominal impedance. If you do mix speakers with different impedances or sensitvities, most A/V receivers will be able to balance or compensate for the varying sound levels of each channel. When I mixed Heritage mains with Synergy center and Reference rears, I had to set the mains to -10 dB before I could balance all the channels. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 29, 2002 Author Share Posted October 29, 2002 Jim: The pair of Heresey's I have say 4 Ohms?! Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 29, 2002 Share Posted October 29, 2002 I have inadvertenly sown mis-information. Let me correct as best I can right now. On another computer I have a graph of the impedance of a Heresy. It goes down to 10.2 ohms in the bass and 10 ohms at the lowest frequency measured. I'll post it in a day or so. Perhaps there was a later or earlier driver which had a lower impedance. I don't know the impedance curve of the Belle. However, attached is one for the K-Horn from the Audio article reviewing it. You'll see that it is getting down near 4 ohms in the the bass. The image is a bit fuzzy. In the K-Horn impedance, you'll see the effect of the auto tranformer in the crossover circuit for the midrange. The input impedance goes off scale, high, in that range. This goes beyond the question . . . but while I'm being a pedant. Looking at the A, and AA and related cross overs, we see that only the mid is fed through the auto transformer. Look at the curve at about the 400 Hz point. We're seeing two things. The bass crossover circuit is causing on open circuit to keep it from loading the amp, and presents no load to the amp (we don't actually see that, it is absent and is not presenting a load). Also, the high input impedance of the autotransformer is causing the input impedance to rise rapidly. The tweeter cross over circuit turns on at about 6000 Hz and is not fed by the auto transformer. We see the input impedance dip down into the range of 10 ohms or so. It may be that the Belle has a similar curve. It uses the same bass driver and is horn loaded. It uses a similar crossover. You'll see somewhat similar curves for other speakers in magazines. The midrange typically doesn't go that high. But the lesson is that input impedance varies widely across the frequency spectrum. An exception is Al K.'s crossovers where some care is taken to level out the input impedance. But I believe there are variations in the bass with his. The bass crossover circuit is similar to a Klipsch. Al may want to comment, and educate us. He has some Belle's. Again, even when there is a nominal impedance stated, it is not going to be that figure, all across the frequency spectrum. Far from it. No one should get alarmed by this. Amps seem to able to handle the variations with aplumb. Though I think that if you have an amp with a transformer output with taps, you're best off using the 4 ohm tap if there is any question. - - - - I commented on the digital signal processor. Home theater receivers use DSP and our friends here often report a noise problem with sensitive Heritage speakers. I've had the problem too. As you may know, all amps create a bit of noise at the output with no input. Say it is 0.0001 watt. With insensitive speakers, the noise can't be heard. However, with sensitive, or efficient, Klipsch speakers, it can be heard. Therefore you need an HT receiver with amplifiiers have a low noise figure. That is not quite the end of the story. HT receivers sometimes have good, low noise output amps. However, the DSP cirucits are relatively noisy in some. What has been reported is that in normal "stereo" mode, the amps in the receiver do okay. However, when a DSP mode is swithed on, there is a significant amount of noise with no input. This seems to vary from model to model and manufacturer to manufacturer. I was using the term "noise floor" a bit imprecisely. It is used to describe radio receivers. They are essentially "listening" to a radio frequency input signal from the antenna. The radio receiver has inherent noise created by the radio receiver circuitry. So eventually a very weak signal may be below the noise floor created by the circuity itself, and can't be heard. Here we're talking about something similar. You'd like to listen to the DVD with no noise at the quiet passages. Yet it may be there with no input. The speakers are hissing away with the volume all the way down. Annoying. Regards, Gil Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 29, 2002 Author Share Posted October 29, 2002 Thank you for the information. I found it very good to look into this issue. Once my Forte's arrive I will hook up the 5.1 system and see how it all goes together. Thanks Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 30, 2002 Share Posted October 30, 2002 Here, as promised, is a graph of a Heresy impedence. Now you know what I know about Heresy impedance. Gil Quote Link to comment Share on other sites More sharing options...
jtkinney Posted October 30, 2002 Share Posted October 30, 2002 Rudy, I will have to check my Heresy's, I don't remember there being anything on the back about impedance. I checked the Klipsch website and they state 8 ohm for the Heresy II. Gil, Thanks for the impedance curves. I have the article that the K-horn curve came from, but had never seen one for the Heresy. Quote Link to comment Share on other sites More sharing options...
erikjohn Posted October 30, 2002 Share Posted October 30, 2002 William, When you said we should use the 4 ohm taps do you mean if the reciever has ohm switching we should set it to 4 ohm. If so does this hold true for all Heritage speakers? I always just leave mine set at 8 ohm, should I change it? EJ Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 30, 2002 Author Share Posted October 30, 2002 Well, I just checked again to make sure. Just above the terminals, it says "Nominal Impedence 4 Ohms". Ohms of course is in symbol form. Quote Link to comment Share on other sites More sharing options...
jtkinney Posted October 30, 2002 Share Posted October 30, 2002 EJ, I think the switch on the RX-V1 just limits the output power since the 4 ohm speakers will draw more current. I have my Heresy center channel speakers (2) hooked in parallel since I thought they were 8 ohms each. If my Heresy's are 4 ohm, the 2 ohms the amp sees may be a problem. With the efficiency of the Heritage speakers, I don't think the amps will be overworked with the 4 ohm speakers at all but max SPL. Quote Link to comment Share on other sites More sharing options...
dougdrake Posted October 30, 2002 Share Posted October 30, 2002 The rated impedance on several Klipsch speakers has changed over time. My KG4s, for example, say 4 ohm on the back, but the web site says 6 ohms. Don't know if that's due to driver changes or different testing procedures. Quote Link to comment Share on other sites More sharing options...
erikjohn Posted October 30, 2002 Share Posted October 30, 2002 JT, I've got mine hooked up in parallel also on the center. EJ Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 30, 2002 Share Posted October 30, 2002 I have no choice in amp output. My ancient Japanese amps don't give me a choice. However, it makes sense to use the 4 ohm switch if you have one and the speaker impedance dips down to 4 ohms. I've checked the output of one old Sony to see if it dips in output voltage where the impedance of my home made K-Horn heads to 4 ohms. There is little or no dip. On the other hand, I tried driving my Quartets directly off the output from a small Trinitron. This required rewiring. There is a problem. My solution was to use the primary of an RS 70 volt line transformer as an autotransformer. The output from the set goes to common and 16 ohms. The speakers go across common and 4 ohms. The drive level to speaker is constant. Natually I'm losing quite a bit of voltage. But it sounds good. I'd think the same holds true if you have an output transformer on your tube amp, or the few Mac SS with a transformer. The output will have less voltage, but that should cut down on the level of noise from the amp. Gil Quote Link to comment Share on other sites More sharing options...
E3T Posted October 30, 2002 Share Posted October 30, 2002 You said A/V Amplifier...as in Receiver? If you have a mix of 4 & 8 ohm speakers, check and make sure that the amp will handle 4 ohms. Some will do fine with 8 & 16 but will burn up the finals (amp outputs) with 4 ohms (slow going, but it will happen). If it is good at 4 ohms then the only other situation you will run into is the difference in volume. Not much and adjustable. Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 31, 2002 Share Posted October 31, 2002 It is nice to see that the topic drew out a new contributor. Nice to hear from you E3T. Gil Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 31, 2002 Author Share Posted October 31, 2002 E3T: Thanks, I will look into the receiver specs when I get a chance. Quote Link to comment Share on other sites More sharing options...
jtkinney Posted October 31, 2002 Share Posted October 31, 2002 My '78 Heresy's say nothing about the impedance on the back. Since I am not the original owner, I don't have an owners manual, so no help there either. Rudy, what year are yours? Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 31, 2002 Author Share Posted October 31, 2002 Well, the serial numbers are 8623363 and 8623664. So, I gather these are 86 models. I am new to this serial number thing on these speakers. My Belle's are 88's for sure,I am the original owner. Quote Link to comment Share on other sites More sharing options...
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