"True" sensitivity of Klipschorns?

[bodcaw boy]

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 space

[garyrc]

Thanks, Roy!

A straightforward answer, not so curved after all. Your forthcoming communication with us about so many matters reminds me of that of PWK, back in the day.

Since Klipshorns must be used in a corner, it seems reasonable to me that 1/8 space would be a realistic environment in which to test them. The corner, in a sense, can be considered to be part of the Khorn. They still wouldn't have the gain due to the absent two walls and ceiling, which are not "part of" the speaker. From your example, it seems that in a real listening room with the room gain due to the two extra walls and the ceiling, they would be slightly louder, with the same input.

If I'm getting this, if for a garden variety (non-corner) speaker, AES says to test in 1/2 space, then those speakers would also be expected to be a little louder in a room, due to room gain, which may be why some manufacturers (e.g., Paradigm) specify two ratings -- a presumably 1/2 space one, and an "in a room" one that is about 2 dB louder.

Thanks again!

[psg]

So if a KHorn is rated in 1/8 space versus regular speakers in 1/2 space, does that mean that a regular 90 dB/1W/1m speaker goes up to 96 dB when placed in a corner?

Since the La Scala had the same rating, it was also rated with corner placement. Is that fair relative to other manufacturer's speakers?

[Islander]

Based on my newbie experience, measured with a Radio Shack digital SPL meter, here's what I've found: my 1974 La Scalas that I've had for just a month are about 8dBA more sensitive than my Audio Logic 750 speakers.

The AL750 cabinets are 36" tall, 16" wide, 12"deep, and of bass reflex design, each with two 10" mid-bass drivers and two dome tweeters. They were manufactured in the Toronto area around 1980. I'm guessing their sensitivity would be in the typical 89-91 range.

As for location, the left La Scala is 68" from the outside wall and roughly 10' from the back wall, while the right La Scala is 64" from the other outside wall, but only 8" from the rear wall. The room is sort of L-shaped.

To balance the volume at the listening position, about 8' from both of them, 0.5 dB was added to the left speaker. Measured 1' in front of each speaker, the left one is up by 1dB, but at a point 8' in front of both, the output is equal, making me think that the difference between 1/2 space and 1/4 space is not that great. It might be more noticeable if the right speaker was backed right up against the wall.

The attached picture may make it easier to visualize. Beside the right speaker is a Paradigm PW-2100 sub, which seems to work really well with the La Scalas, although I was surprised to find that I got the smoothest response with the sub hi-cut set at 150Hz.

[Islander]

Oops! I should have written "Measured 1' in front of each speaker, the left one is up by 0.5dB,", not 1dB. That makes more sense...

[psg]

Well, about 25 years ago, when I got my La Scala, I installed a Radio Shack SPL meter on a tripod 1 meter (it might have been 4 feet, but I somewhat recall using meters) away from the mid-horn and set the volume so that the 1W LED on my amplifier would light up solidly (no flicker). This was inside, with the speaker back against a wall but no corner.

It read 104 dB.

So I believed it then.

[psg]

Those La Scala's are like that for the measuement only, right? Not for music, right?

[Islander]

Actually, that is where those speakers usually are. To move the right one further right would mean removing the fireplace and its raised deck, and if the left one was further over, I wouldn't be able to get past it into the livingroom.

The livingroom is also my photo studio, so I need space to lay out backdrops when I'm shooting. The square white object near the ceiling is a softbox mounted on a studio flash unit, and there are posing chairs and tables stored along the wall.

Measured center-to-center, the speakers are 5'2" apart, and the sweet spot where I listen is around 8 feet from them, so the sound stage is reasonably wide. I"d like to have them around 7 feet apart, but that would be a total width of 9 feet and I'd have to climb over the left one.

You may notice that they're not parallel. I experimented with four different toe-in settings and got the best sound with the one that has the centerlines crossing about 4 feet behind the listening position.

Pat on the Island

[psg]

Well, for kicks, just once try them elsewhere with a spacing of something like 18 feet. Toe them in at a huge angle (45 degrees simulates Klipschorns) and sit in the crosshairs. You will be amazed at what you hear. They will disappear from the room to leave precisely placed instruments. They image as well as Klipschorns.

[Islander]

Thanks for the tip, Peter! I'll give it a try sometime.

Pat on the Island

[Islander]

Any snow in Rimouski yet? I grew up near Quebec city.

Pat on the Island

[psg]

Any snow in Rimouski yet? I grew up near Quebec city.

Pat on the Island

I also grew up near Quebec City, in Ste-Foy, now absorbed into Quebec City.

No snow yet. No even that close to freezing yet. I haven't winterized the pool yet either.

http://meteo.ec.gc.ca/city/pages/qc-138_metric_e.html

[Islander]

Ste-Foy? What a small world! I lived in Shannon and went to St-Pat's. Did you go there too, or maybe QHS? Seems like everyone headed out from Quebec to seek their fortunes elsewhere.

After spending many years in Toronto, I wound up here in Victoria. With the old buildings and the waterfront, it's a bit like Quebec without the snow. We've got the Empress Hotel instead of the Chateau Frontenac, and we have ferries, but they go to Seattle and Port Angeles instead of Levis.

Pat on the Island

[psg]

Small world indeed. But I actually went to school in french until grad school, so we didn't go to the same schools. I'm now only a 3-hour drive away from Quebec City, so still visit my friends and family often.

Victoria is nice. I should be there in mid-december for a meeting:

http://www.arcticnet-ulaval.ca/index.php?fa=ASM.2006conference

My father was born in Vancouver, so I've got family ties there as well.

[Islander]

Cool! If you get a break from the conference, we could meet, maybe talk about Quebec. And speakers, of course! Last time I was there was in 1998, when I drove there from Toronto. I got to show the place to some in-laws from the West, and it was good to see the place again.

Pat on the Island

[psg]

I'll keep that in mind! Thanks!