SENSITIVITY question.

[InVeNtOr]

i just noticed this. on a RF-7 is says "102dB @ 2.83 volts/1 meter" and on a KLF-20 is says "100dB @ 1watt/1meter."

why the two different scales? which is better/ worse? why? last time i spoke to tech, they said the rating was on the 1 watt/1 meter, so why are the 7's measured different?

sorry if this is a tard question.

[russ69]

I'm a bit at the edge of my knowledge but 102dB @2.83 volts/1 meter assumes an 8 ohm impedance (at 1 watt) and at an unknown frequency. The problem is that speakers vary in impedance at different frequencies and measurements may not relate to relative loudness from speaker to speaker. I always use specs as a rough guide, unless I'm making the measurements myself. The measurement guys may be able to define what the standard practise is better than I can.

The other problem is how do you measure a 3 driver system at 1 meter, sum the output of the 3 drivers, I guess. Then you have bipolar speakers that have equal energy on both front and back, you could just add 3 db but that's not a measurement it's a calculation.

Thanx, Russ

[Rivernuggets]

Doesn't 2.83 volts equal 1 watt? Aren't they just using different terms?

[Colin]

yup. the measuremenmt is standard

[InVeNtOr]

you know if i would have done a google search i would have found that. i didn't even think about it. here's a link to a page describing it.

thanks guys!

[jacksonbart]

2.83 volts into 8ohms equals 1 watt

[Groomlakearea51]

sorry if this is a tard question.

Don't worry!!! It's NOT a tard question. It's a very, very good question, especially when reading the article you referenced. As to why Klipsch decided to use 2.83 V instead of 1 W in the description is related to the last paragraph in the article. Engineers do "engineery" things.....

[dBspl]

The link is correct. The 1 watt specification is basically a misnomer. Because loudspeaker impedance varies widely with frequency, it's almost impossible to establish what 1 watt really is. And even if you could, it really wouldn't be worth very much (it's not exactly sensitivity and it's not exactly efficiency...it's something in between). Amplifers are constant voltage sources, not constant power sources.

dbspl

[garyrc]

Roy Delgado ("bodcaw boy;" Klipsch engineer) provided a long and humorous answer to my question (on this forum) as to how Klipsch speakers are measured for efficiency and sensitivity a few years ago. My original question and his answer are reproduced below.

Early on, PWK recommended that all speakers be placed in a corner, except for the center channel speakers in his "Wide Stage Stereo." Corner placement increases SPL in the bass. For Klipschorns, which must be placed in a corner, it makes little sense to measure them in 1/2 space (see below) --- the trihedral corner is considered part of the design.... so they are measured in a wooden artificial corner in an anechoic chamber, which is close to 1/8 space.

Re: "True" sensitivity of Klipschorns? Garyrc: To Roy "bodcaw boy" ... I talked to you on the phone when I was first setting up my old sound room in, say, 1983 (?). You were very helpful, thanks, and you let me know that "Mr. K doesn't like equalizers." Now that you are on this thread, can you give me your take on why there are discrepancies in the rating of either the sensitivity or efficiency of the Klipschorn, Belle, or La Scala (from 98 dB to 105 dB)? Here is an excerpt from the post in which I first raised the question: Does anyone know why the following minor discrepancies in sensitivity ratings exist? Are they due to Klipsch's later anechoic measures with a revolving door corner matching the industry's very old "midrange only" measures more closely than present day magazine reviewers can get with wide frequency range SPL measures, without a revolving door corner in an anechoic chamber? This is mostly just a matter of curiosity on my part. I wonder if the Khorn at its max continuous 100 watts really puts out SPL equivalent to a typical, 90 dB @ 1w @1m, speaker soaking up 2667 watts continuous, if only it could! Klipsch consistently rated Klipschorns, Belles, and La Scalas at 104 dB @ 1wt @ 4 feet, in the past. Now, as of 2006, the new Khorns and La Scalas are rated at 105 dB @ 1M], yet two European reviews rate them at 98 dB. The old Audio review by Heyser(1986) rated the Khorn at "well over 98 dB." The article states that his tests using free field response used a simulated free field using computer software. He follows his "well over 98 dB" statement with, "This system really will give the rated 104 dB SPL at a distance of 4 feet into a room," but doesn't say whether this was a guess, an enthusiastic expression of faith, or the results of a test. Back when both Klipsch and JBL were including EIA ratings in their specs, both the Khorns and the JBL D-130 (no network) were rated at 54 dB EIA. The two companies agreed fairly closely as to what 54 dB EIA translated to; Klipsch listed it as equivalent to 104 dB, 1wt, 4 feet, and JBL listed it as equivalent to 103 dB, 1wt, 1M. I think, but don't know, that the EIA measurements used a narrower range of frequencies than modern measures. hi garyrc long time no talk! you have asked a straighforward question that unfortunately has a pretty "curved" answer. first we use 2.83v instead of 1 watt because i have yet to see an 8 ohm speaker from 20 hz to 20k hz. next it is sensitivity. what we want to measure is spl, sound pressure level, or a simple way to say this is how loud will it get. now the curved part. take a la scala and place it in your listening room in a corner. applie pink noise across the rated bandwidth of the speaker, adjust the voltage until you read 2.83 volts, get your calibrated spl meter about a meter away and measure the spl. that is the sensitivity of the speaker. now move your meter around and you will notice that it be a little different from location to location. that is because you might be in a null or peak. we usually mesaure at the tweeter axis. taking an average of several readings helps. now lets say your house contractor calls and wants to know where the rest of the money is for building the house. you say what money? the next day, your roof and 2 walls are gone. your la scala is still in the corner and you run the test again. you live out in the country and there are no buildings near your home. this time the spl reading is down. the reason? you have removed room gain. now you are measuring in 1/8 space. now your contractor asks, pay me my money. and you say no, sticking to your conviction (while i at this point am saying, convictions, schvictions). next day, another wall was removed. now you move the la scala to the middle of the wall and run your test. spl drops some more. reason? now you are measuring in 1/4 space. once more, the contractor says, show me the money. and mr conviction says no. the next day all you have is a floor. you move the la scala to the middle of the floor and make the speaker shoot straight up. you run the test and the spl drops some more. reason. you are now measuring in 1/2 space. now you are losing it. you make a platform the width of the la scala back and that is 100 foot tall. you take the la scala and place it on the platform with the horns facing up and run your test. spl drops again. why? you are in full space. you see, depending on the directivity of the speaker and how much air it has to move, spl can vary. that is why aes says, 2.83 volts, 1 meter, pink noise with 6 db peaks, 1/2 space and over the bandwidth of the speaker (loosely paraphrased). for the consumer market we use quasi 1/8 ( more like 1/6 space) with room gain and for a khorn, it is 1/8 space. well hope this helps. berryboy roy in quasi forum