wireless Posted May 14, 2003 Share Posted May 14, 2003 From the Home theater forum, I posted this but thought it might be better discussed here... ---------------- On 4/30/2003 11:22:25 AM dougdrake wrote: ---------------- On 4/30/2003 9:36:28 AM wireless wrote: BTW, anyone know why the new speakers' sensitivity is rated in volts/meter instead of the old watts/meter? -David ---------------- OOH, OOH, OOH - I know, I know --- The wattage going into a speaker fluctuates with the impedance of the speaker, and the impedance varies depending on the frequency being played. To eliminate that variable, they switched to volts/meter because the voltage can be more explicity controlled and stated. 2.83 volts is equivalent to 1 watt at 8 ohms impedance... DD ---------------- So does that mean when power is calculated for a 4 ohm speaker (or an 8 ohm speaker whose impedance varies down to 4 ohms) with 2.83 volts, that the input wattage is 2 watts? Thus, by using this new method, Klipsch is able to get 3 dB more input at 4 ohms and hence is able to effectively double the sensitivity by simply changing the measuring technique? Quote Link to comment Share on other sites More sharing options...
formica Posted May 14, 2003 Share Posted May 14, 2003 Well that is one way to look at it... another way would be to say that it makes it possible to actually test speakers with "controllable" source... and make it easier to compare speakers of different resistance. Like you mentionned, speakers don't have all the same resistance... but they don't even have the same resistance at different frequencies either. The "8ohms" often quoted is just an average and it is difficult to produce a constant 1W source... unlike the 2.83V. The amp will, in general, also put out double the watts into half the resistance... so your 30W into 8ohm amp will put 60W into 4ohms. Given the above info and two different speakers (one 4ohm and the other 8ohm) rated at the same efficiency from 2.83V*1m... plugged into the same amp and with the volume knob in the same position... they will play at the same volume. seems even more precise than 1W*1m Rob. Quote Link to comment Share on other sites More sharing options...
wireless Posted May 15, 2003 Author Share Posted May 15, 2003 ---------------- On 5/14/2003 3:18:47 PM formica wrote: Given the above info and two different speakers (one 4ohm and the other 8ohm) rated at the same efficiency from 2.83V*1m... plugged into the same amp and with the volume knob in the same position... they will play at the same volume. seems even more precise than 1W*1m Rob. ---------------- [/blockquote> Yes, I agree, but the problem is we're given two different groups of speakers tested with two different methods. On one we have all the RF and earlier speakers tested with the 1w/m method and the recently released RF line (15,25,35) tested with the new method. What will the amp do with the volume in the same position on speakers from both groups with sensitivities that are rated the same? How difficult is it to measure the sensitivity of the Klispch speakers that are in current production using the new method? The current scenario is similar to a car company having some of their cars' horsepower spec in brake horsepower (BHP) and the other half given in horsepower at the crank. An apples to apples comparison would be helpful. Quote Link to comment Share on other sites More sharing options...
JohnA Posted May 15, 2003 Share Posted May 15, 2003 I'm not too familiar with Klipsch testing and rating procedures, but I'll bet 2.83V was used in the old rating, even thought it was labeled 1 watt. The voltage is easily controlled where the current, and therefore power, is not. More than likely, the efficiency of each speaker are the same even though the rating method *appears* to change. Quote Link to comment Share on other sites More sharing options...
Billy2Gunz Posted May 15, 2003 Share Posted May 15, 2003 Yes, but few amps (except for Krells and the like) will put out twice the power into 4 ohms as 8 ohms at their max output. For instance, an amp may be rated at 100W into 8 ohms and 140 into 4 ohms. Sensitivity is really a moot point unless you are running an amp wide open. Typically changing from 1W/1m to 2.83V/1m is a marketing ploy to make 4 ohm speakers look more efficient. Another ploy is to rate speakers into something less than full space, like 1/8th space. This adds the room gain into the efficiency. Look at the way Klipsch rates some of their subs Quote Link to comment Share on other sites More sharing options...
formica Posted May 16, 2003 Share Posted May 16, 2003 ---------------- On 5/15/2003 2:18:52 PM Billy2Gunz wrote: Yes, but few amps (except for Krells and the like) will put out twice the power into 4 ohms as 8 ohms at their max output. ---------------- I believe what happens (correct me if i'm wrong) with some amps is their power supplies are unable to handle the increased current due to the reduced resistance... but it's never a good idea to push an amp (or receiver) to clipping. The theoretical difference between between 140w and 200W represents a fraction over 1.5db. I do prefer the 2.83V*1m for it's improved accuracy... and the market (ie: other brands) is moving towards this voltage based spec... hopefully Klipsch will go back and re-test their existing models for consistancy. Rob. Quote Link to comment Share on other sites More sharing options...
wireless Posted May 16, 2003 Author Share Posted May 16, 2003 I do prefer the 2.83V*1m for it's improved accuracy... and the market (ie: other brands) is moving towards this voltage based spec... hopefully Klipsch will go back and re-test their existing models for consistancy. ---------------- I keep hearing that the v*m method is more accurate but aren't we talking about accurate in terms of the voltage input? What does this have to do with the real world spec for output? All holding the input at 2.83 v means is that the current will have to adjust to whatever the impedance is. In other words, to match the "improved" input metric, the amp had better have a very good current providing ability which as we all know isn't the case for 95% of the amps out there. And of course this is going to vary the input wattage making the output sensitivity spec just as nebulous as the "improved accuracy" input voltage metric. And as far as preciseness goes, what does "8 ohm compatible" mean? Does that really tell you anything? Sure we know the impedance varies with frequency but how much? Why not offer some limits or ranges? If it's dropping down to 1 ohm over a certain frequency range and current is varying all over the place, all this has done is buried the varying factor under the constant voltage and ostensibly make it sound like a more accurate measurement. Quote Link to comment Share on other sites More sharing options...
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