t-man Posted January 18, 2012 Share Posted January 18, 2012 I found this tool online today: http://www.allegrosound.com/Power_AllegroSound.html I think it is helpful when discussing how much power you really need to drive efficient speakers in your listening arrangement. Do any of you disagree with it? I'm interested in opinions. My HT has me sitting 11 feet from each main speaker. I'm not even going to account for the center or rear channels or room gain here, but with my conservative calculations: 3.5 meters distance 100dB/Watt (KLF 20) Generous Amp headroom (6 dB) With 100 dB listening volume (not counting the LFE) Provides me with only needing about 50 watts to obtain this rather high level of SPL/Volume. Take into consideration that I crossover at 80 Hz and send the low frequencies to my sub, it seems safe to say that my receiver should never have to go over 50 watts and should have plenty of headroom?? Why would I consider a seperate power amp? Quote Link to comment Share on other sites More sharing options...
StephenM Posted January 18, 2012 Share Posted January 18, 2012 Why would I consider a seperate power amp? If you're satisfied with the performance of your system, you wouldn't. However, lets throw one monkey wrench into your calculations: an impedance dip down to 2.8 ohms (comparable to the RF-7). At 50 watts into 8 ohms, you're talking 20 volts and 2.5 amperes. Entering the 2.8 ohm dip, voltage remains 20V since voltage sensitivity hasn't changed, but amperage climbs to 7.14 and the power jumps to ~143 watts. That's a lot for most receivers, especially if you are conservative and expect mutliple channels to peak at once. Quote Link to comment Share on other sites More sharing options...
GBShade684 Posted January 18, 2012 Share Posted January 18, 2012 Stephen, That's a good point, but witha cross over at 80Hz, would you expect to see an impedance dip that large? Would you expect one at all? Quote Link to comment Share on other sites More sharing options...
SuBXeRo Posted January 18, 2012 Share Posted January 18, 2012 impedance is always dynamic so you will always have dips. The size of the dips should be directly correlated to the frequency of sound being produced as well as the amplitude the sound is produced at. Keep in mind that the rating they give you is a nominal (average rating). Quote Link to comment Share on other sites More sharing options...
StephenM Posted January 18, 2012 Share Posted January 18, 2012 That's a good point, but witha cross over at 80Hz, would you expect to see an impedance dip that large? Would you expect one at all? A crossover at 80Hz only helps if the impedance dip is below 80Hz. There is no guarantee of this, and in fact, from what I've seen of Klipsch speakers, I'd bet against it. http://www.hometheater.com/content/klipsch-reference-rf-83-speaker-system-ht-labs-measures http://www.hometheater.com/content/klipsch-reference-rb-75-ht-labs-measures http://www.hometheater.com/content/klipsch-rb-81-speaker-system-ht-labs-measures http://www.hometheater.com/content/klipsch-reference-rb-61-ii-speaker-system-ht-labs-measures In every one of those speakers measured, (12 in total, 4 mains, 4 centers, 4 surrounds), none of their impedance minimums were below 80Hz, instead being between 100 and 300Hz for the most part. As for how much of an impedance dip I'd expect or whether I'd expect to see one at all, your best bet is to ask Klipsch about your specific model and work from there. Anything else is just a guess. Quote Link to comment Share on other sites More sharing options...
StephenM Posted January 18, 2012 Share Posted January 18, 2012 The size of the dips should be directly correlated to the frequency of sound being produced as well as the amplitude the sound is produced at. Not exactly. This is what an impedance curve looks like: http://www.stereophile.com/images/archivesart/K15FIG1.jpg The subject in question is the RB-15. This curve will not change with relation to amplitude unless thermal compression becomes an issue. While you can tell a few characteristics about a speaker by looking at its impedance curve (ported vs sealed, tuning point of port, etc), I would hesitate to say there is any special correlation between the frequency and impedance. Quote Link to comment Share on other sites More sharing options...
StephenM Posted January 18, 2012 Share Posted January 18, 2012 I would hesitate to say there is any special correlation between the frequency and impedance. Two more for good measure: http://www.soundstagemagazine.com/measurements/ascend_cbm170/impedance.gif http://www.soundstagemagazine.com/measurements/energy_veritas_v24i/impedance.gif Quote Link to comment Share on other sites More sharing options...
SuBXeRo Posted January 18, 2012 Share Posted January 18, 2012 i stand corrected and am just gonna keep my mouth shut Quote Link to comment Share on other sites More sharing options...
cornfedksboy Posted January 18, 2012 Share Posted January 18, 2012 i stand corrected and am just gonna keep my mouth shut Don't do that! Stephen pulls out some some fairly cool graphs. I have found that by disagreeing with Stephen that I learn quite a bit of new info. Quote Link to comment Share on other sites More sharing options...
t-man Posted January 22, 2012 Author Share Posted January 22, 2012 Many know about the RF7 and how they dip low like that. I've never seen any information on the KLF series, though. Looking at the data from the links, it appears that within the given line, the smaller the speaker (center or rear vs mains), the less likely the impedance dips into the extremes. Quote Link to comment Share on other sites More sharing options...
StephenM Posted January 25, 2012 Share Posted January 25, 2012 Looking at the data from the links, it appears that within the given line, the smaller the speaker (center or rear vs mains), the less likely the impedance dips into the extremes. It seems like a fair assumption, although size doesn't necessarily mean much: http://www.stereophile.com/content/klipsch-palladium-p-39f-loudspeaker-measurements http://www.stereophile.com/content/klipsch-palladium-p-17b-loudspeaker-measurements Clearly, the P-39F is considerably larger than the P-17B, yet the impedance dips are fairly comparable. Presumably they figure if you're buying a $4000 pair of speakers, you probably won't be using them with a $300 receiver. Quote Link to comment Share on other sites More sharing options...
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