Note on sensitivity (RP-280F)

[Grizzog]

I know there are plenty of conversations going around whether the reference series is measured accurately or not.

 

Just wanted to share my experience with the RP-280F.  This isn't what you'd call scientific, but a pretty good indication for me.  I tested this with Quartets and RP-280F.

 

Ratings:

Quartets: 97.5db

RP-280F: 98db

 

I hooked up my Quartets to an NAD T758 and matched all speakers to 75db on the test tone with an SPL meter (it actually settled at about 75.6).  They ended up at -8db from the amp settings.

 

I then hooked up the RP-280 and had expected I'd have to re-do all the settings. Played the test tones, and the SPL meter mostly settled on 76.1db without adjusting anything.  Since there is a bit of fluctuation with the test tones, I left all settings the same.

 

What's my point?  It seems the specs are rather accurate based on my tiny bit of testing.  So if the reference series has any inflated specs, so did the Quartets.

Edited March 29, 2016 by Grizzog

[jacksonbart]

Top Notch

[Schu]

I just talked my friend (retired audio engineer for A&M records) into buying a set of 280's... he's never owned Klipsch speakers before. I am sure this will make him happy.

[garyrc]

Naturally, a speaker's rated sensitivity depends on how it is measured.  At one point, Roy answered a post of mine, and gave us some specifics, which varied with the model.  I think I remember Klipschorns were measured in 1/8 space, because they need to be used in corners (real or artificial), period.  This probably was done in Klipsch's revolving door anechoic chamber.  Other Klipsch models were measured differently (not in corners), but, as I recall, not the AES way (1/2 space ).

 

EDIT:  I found my question and Roy's answer:

 

 

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

Edited March 30, 2016 by garyrc

[Grizzog]

Wow! Thank you.  That's the first official response I've seen.

 

Since most of us use our speakers in a room, the sensitivity specs are about what should be expected.  I assume 1/6 space would translate to a wall, floor, and a ceiling/side walls somewhat near by.

It appears that Klipsch speakers can be compared to each other for sensitivity. As far as comparing other brands, it won't make much sense since it isn't specified how they are measured.  I would bet that most brands do an in-room measurement though.  For most purposes, a "full space" measurement wouldn't be too helpful.

 

I'm still going to hold firm that Klipsch are much more sensitive than most other speakers, based on my experiences.

Edited March 30, 2016 by Grizzog

[Grizzog]

Ok, I couldn't help myself and read more.

If it is 1/6 space plus room gain, that could be 9.5-11.5db increase in sensitivity over anechoic. (7.5db increase for 1/6 space and between 2-4db for room)

Some manufacturers rate their speakers anechoic, so if I saw 88db anechoic, is that basically the same as the 280s in-room spec of 98?

[Ski Bum]

Some manufacturers rate their speakers anechoic, so if I saw 88db anechoic, is that basically the same as the 280s in-room spec of 98

 

 

Doubtful, unless those are genuine specs and not massaged for marketing purposes.  The 88 db speakers are likely less than that in reality, physically smaller, and would require some serious drivers ($$) to have even a prayer of keeping up in the dynamic range department, while requiring gobs more power and exhibiting relatively more distortion in the process.  

[garyrc]

Ok, I couldn't help myself and read more.

If it is 1/6 space plus room gain, that could be 9.5-11.5db increase in sensitivity over anechoic. (7.5db increase for 1/6 space and between 2-4db for room)

Some manufacturers rate their speakers anechoic, so if I saw 88db anechoic, is that basically the same as the 280s in-room spec of 98?

 

Well, I don't know.  

 

Given all Roy said, and given that Klipsch has a revolving door anechoic chamber with a wood corner built into it, with a bit of a ceiling (the only one in the world, as far as I know), I would think they would just place whatever speaker they are testing in it, but not pushed back into the corner (except for Khorns).  The mere presence of the corner nearby might provide the room gain Roy is talking about (??).  So, moving from 1/2 space to 1/6 space ("quasi 1/8") would be the room gain, I would think.  

 

If the other raters of the Klipschorn's sensitivity came up with 98 dB (as two of them did), and the other raters used 1/2 space as the AES specs call for (singularly inappropriate for a Khorn), and Klipsch uses 1/8 space to measure Khorns (as Roy said), then moving from 1/8 space to 1/2 space caused a 7 dB decline in rated sensitivity (105 dB - 98 dB = 7 dB).  So, I would guess that the less than full corner loading Klipsch uses for the rest of their consumer line ("more like 1/6 space") would cause less than a 7 dB difference.  

 

I've heard that some speaker manufacturers, instead of using pink noise over the bandwidth of the speaker, use pink noise that is filtered to include only 500 to 2K Hz.  That might give them higher readings.  One dealer suggested that some use just 1K tones, but I find it hard to believe that.

 

We have some Heresy IIs we use for surrounds.  They are rated at 96 dB by Klipsch, and they sound much louder than some Yamahas we have that are rated at 90 dB.  I haven't measured, but the difference sounds like about 6 dB by ear.

Edited April 4, 2016 by garyrc