"True" sensitivity of Klipschorns?

[garyrc]

Perhaps this subject came up during one of the Klipsch Pilgrimages, or maybe one of you did real or simulated anechoic or quasi-anechoic "with a corner" tests.

Does anyone know why the following minor discrepancies in sensitivity ratings exist? Are they due to Klipsch's later, wider frequency range, anechoic measures with a revolving door corner matching the industry's very old "midrange only" measures more closely than magazine reviewers can get with wide frequency range SPL measures, without a revolving door corner in an anechoic chamber" What did you folk get measuring Khorns in your environments? 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 rates Klipschorns, Belles, and La Scalas at 104 dB @ 1wt @1M [or @ 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.

[rcarlton]

Both the K-horn and LaScala II are both rated at 105 dB/meter. For years Klipsch had used 104 dB/meter...turned out with newer measuring techniques it had been actually 105 dB/meter for years. This information came from Mark Kaufman at the Pilgrimage.

[SilverSport]

I received an email from Klipsch when I went to the AK-4 upgrade on my K'Horns...was 105dB all the time, just changed the way it was measured or some such...105dB it is!

Bill

[Al Klappenberger]

For what it's worth, I have a calibrated mike and fancy FFT analyzer. I have made frequency response measurements of actual SPL levels on my modified Belles. I found it to be about 99 dB SPL for 2.82V. I don't think it's my mods because the woofer determins the sensitivity and I have simply adjust the other drivers to match the woofer.

Al K.

[PrestonTom]

It is an interesting question since the numbers do vary. As I understand it, and I am probably missing a couple of details, the measure (and its companion measure "efficiency") are generally done in an anechoic environment. When a speaker is measured in a room there will be a gain due to the room. So what to do about the Klipschorn? It is meant to be in a room by design - specifically in a corner (or 1/8 space, meaning a floor, a wall, and another adjacent wall). So this is what is currently being done. Note, not all speaker builders would perform the measures this way, however it is logical for Klipsch to do it this way, given the design of the speaker. Other cabinets that were designed to get a bass boost by being placed on a floor, would, and should, be measured with a "floor" (1/2 space). But this brings into question how to compare across cabinets (and across measures) if some are anechoic and others allow a simulated room gain? I am interested in what the answer is myself.

A second question is the issue of test signal. I believe a pink noise is typically used (equal energy per octave band). This would mean that a cabinet that had a broader bandwidth would be considered more "efficient" or more "sensitive". Is this a "fair" measure? I am not sure.

Incidentally, "sensitivity" is the SPL (output) produced by a given wattage input (usually 2.8 for an 8 Ohm cabinet or sometimes simply 1 watt). Whereas "efficiency" is the SPL output produced by a given voltage (please note there are also other definitions of efficiency). You can can convert between the two if you know the impedance (which is not really a single number anyway, since it most likely changes with frequency).

Interesting question,

-Tom

[SilverSport]

...thanks guys...I love this place...always something more to learn!

Bill

[Ray Garrison]

"sensitivity" and "efficiency" are not exactly equivalent ways of measuring acoustic output. Efficiency is a measure of how effectively a speaker translates input power into total acoustic power output. Sensitivity is a measure of how high a sound pressure level, measured in dB, a speaker will achieve at a specific point in space given a specific input. While these may sound very similar, that can be misleading.

for example, let's take jacksonbart. If we apply a specific input power, say by prodding him with a lead connected to a 12 volt car battery, he will produce a specific output ("scream"). If we were able to measure the total acoustic output power, it might measure, say, 6/10 of a watt (*VERY* loud). If the input current was 5 amps, thus indicating a 60 watt input signal, this would translate to an overall efficiency of 1%, which is not bad. Meauring the sensitivity would be done by placing a calibrated mic in front of him at some specific distance under some defined circumstances - standing in the corner of a room, standing in the center of an anechoic chamber, standing outside, whatever - and measuring the SPL at that distance. Let's say we stand him in the corner, measure the sound level 1 meter in front of his mouth, and read 97dB. This translates into a sensitivity of about 80dB / 1 meter / 1 watt, roughly. Note that this measurement is specific to the frequency of the output. Now, give him a megaphone, and repeat the same test. The total acoustic power output, or efficiency, is not going to change (assuming he's had sufficient time to recover between trials.) however, using the megaphone will improve the impedence match between his vocal cords and the air in the room, and the apparent sensitivity *WILL* increase, perhaps by as much as 6dB, to 86dB / 1 meter / 1 watt. Efficiency remains the same, sensitivity increases.

In a loudspeaker, the efficiency is determined by the electrical and mechanical characteristics of the crossover and drivers, while the sensitivity can be greatly affected by the enclosure design.

[PrestonTom]

Ray,

You are correct, also.

Unfortunately, there are two definitions of efficiency. The one I am referring to is not used as frequently, but you will still come across it. Since it is directly related to sensitivity (if you know the impedance), it becomes redundant with sensitivity. That is why I stated that there were other definitions also.

-Tom

[D-MAN]

The Klispchorn is a nasty little problem to measure, that's for sure, because the space it's in is required as part of its operation. A room can be measured for its characteristics to null out the response without the speaker, then the speaker is tested and the response adjusted for the room characteristics, etc.

The issue is that the Khorn is measured for sensitivity at 3 meters (due to its configuration), and then is "adjusted" mathematically for the 1 meter response. Add to that the complexity of averaging a bandwidth response.

An easy estimation of its "expected" sensitivity would be the known 96 db for the K33E woofer @ 1 watt (2.84V). Add +8db for the horn loading and corner placement. That gives about 104 db per bass bin, sans other frequencies. There would be some expectation of variances, but that should be a good ballpark figure.

Since the top-end SHOULD be adjusted in operation to be equal or less than the SPL output of the bass bin, they can be safely ignored for the purposes of sensitivity. There would be some losses incurred, of course.

DM

[freddyi]

here's K33E impedance in a K-horn plus an in-room plot (tricky) vs Sentry IV loaded with PYM1298. PYM1298's ebp is less than what old-school horn folks like and K33E is below PYM1298.

I think mass rolloff comes into effect but K-horns folds probably choke things a bit vs a staright horn.. I've used 2220H and K43 in K-horn with tradeoffs vs K33. 2220H's ~3mm xmax can limit output on low end. (IIRC ~8dB less than K33E at 50-??-this was observed in-room with scope and mic on sine)

hey D-Man - what the effective inroom sensitivity of La Scala at 55-60Hz?

[D-MAN]

"hey D-Man - what the effective inroom sensitivity of La Scala at 55-60Hz?"

That is a problem! First, what placement and how far from the walls, etc.? Not as easy to figure (guess) as the Khorn.

I'd GUESS maybe 104db or so in a corner, 101 or so in 1/4 space, and 99 or so in 1/2 space.

DM

[freddyi]

from FH1 outdoors (assuming 104dB in flat passband) might one say ~92dB at 60Hz for K33 type in LS type ?

what might Belle/LS do indoors at 60 on a "good day"?

[Hardhead]

Ray--

Speaking of "sensitivity," I think jacksonbart's output would vary depending on WHERE we attached the leads of the battery.

Also, to make the analogy more, uh, analogous, I suggest we use AC instead of DC, if for no other reason than 12 volts seems so low. Since the signal sent to speakers is AC anyway and since we could get ol' jacksonbart to sing REALLY loud by pushing the voltage way up, AC might be more fun and interesting as well. We could see just how much voltage it would take to set his "voice coil" on fire.

Uh, no offense, jacksonbart.

[jacksonbart]

I am very sensitive, so keep that thing away from my naughty bits. Tito, get me some tissues.

[IndyKlipschFan]

Freddyi and others....

How do those specs on the Peavey FH-1 match up with the La Scala bottoms?

Does the black widow speaker improve or hurt the FH-1? Use a K-33 instead in a FH-1?

Or for that matter, a Black Widow in a La scala bottom?

Some have thought maybe the Peavey Bottom with the La Scala x over and top part (mids and high horns) might make a great speaker? Or maybe a huge horn others are looking at on the jubilie system and the FH-1 bottoms making it a 2 way system too? (FH-1s can be found on the net used on ebay and music stores. The reported specs from long ago on them are very close to the La Scala bottom doghouse if I remember right? Besides, to build a doghouse is hard to do for your "average guy.")

[Jay481985]

Ray--

Speaking of "sensitivity," I think jacksonbart's output would vary depending on WHERE we attached the leads of the battery.

Also, to make the analogy more, uh, analogous, I suggest we use AC instead of DC, if for no other reason than 12 volts seems so low. Since the signal sent to speakers is AC anyway and since we could get ol' jacksonbart to sing REALLY loud by pushing the voltage way up, AC might be more fun and interesting as well. We could see just how much voltage it would take to set his "voice coil" on fire.

Uh, no offense, jacksonbart.

A car battery is only 12 volts but offers like 50 amps unlike A/C which offers 120 volts but maxes at 15 amps (usually 12 when the circuit breaker kicks in) voltage doesn't kill as stun guns emit up to 50000 volts, its amps (current) that really kick you in the nuts or jb's nuts!

BTW a car battery can kill you.

[freddyi]

I think FH1 would be pretty close to La Scala. There could be some tonal differences and K33E has a good deal more xmax available. (1504 looks to be built raound K33 spec) A portable circular saw and guide could do an ok job. FH1 and Belle/LS are like "big midrange" (or small midbass) horns so there may be some psychoacoustic trickery involved with results. I think dustcap peak is audible with 1504 - or at very least its not helping matters.

McBean's hornresp should show the LF picture and Belle/LS may not lose anything to 10 cubic foot FH1. FH1 was well made and its mouth well-braced. They're not pretty for home decor but should be cheap on used market as w-bins seem out of favor for PA (?).

a simple non-bulky wallhorn solution which allows reasonably placement of mid and tweeter horns may be of debate on how to execute. I've seen longer path horns with B&C smaller drivers packed into 8-10 cubic foot.

[sheltie dave]

Indy, John Albright has a set of FH1 Scalas, and notes the FH1s come close to the Scala bass bin output, but at much higher distortion. I've seen the same with the Peavey FH1 stack I have, with Black Widows and the cheesy bloated horns.

Klipsch has a dual use lazy susan speaker pedastal in their aneochic chamber- flat wall on one side and a 1/8 space corner on the flip side, so their measurements are true calibrated values.

[bodcaw boy]

"sensitivity" and "efficiency" are not exactly equivalent ways of measuring acoustic output. Efficiency is a measure of how effectively a speaker translates input power into total acoustic power output. Sensitivity is a measure of how high a sound pressure level, measured in dB, a speaker will achieve at a specific point in space given a specific input. While these may sound very similar, that can be misleading.

for example, let's take jacksonbart. If we apply a specific input power, say by prodding him with a lead connected to a 12 volt car battery, he will produce a specific output ("scream"). If we were able to measure the total acoustic output power, it might measure, say, 6/10 of a watt (*VERY* loud). If the input current was 5 amps, thus indicating a 60 watt input signal, this would translate to an overall efficiency of 1%, which is not bad. Meauring the sensitivity would be done by placing a calibrated mic in front of him at some specific distance under some defined circumstances - standing in the corner of a room, standing in the center of an anechoic chamber, standing outside, whatever - and measuring the SPL at that distance. Let's say we stand him in the corner, measure the sound level 1 meter in front of his mouth, and read 97dB. This translates into a sensitivity of about 80dB / 1 meter / 1 watt, roughly. Note that this measurement is specific to the frequency of the output. Now, give him a megaphone, and repeat the same test. The total acoustic power output, or efficiency, is not going to change (assuming he's had sufficient time to recover between trials.) however, using the megaphone will improve the impedence match between his vocal cords and the air in the room, and the apparent sensitivity *WILL* increase, perhaps by as much as 6dB, to 86dB / 1 meter / 1 watt. Efficiency remains the same, sensitivity increases.

In a loudspeaker, the efficiency is determined by the electrical and mechanical characteristics of the crossover and drivers, while the sensitivity can be greatly affected by the enclosure design.

hi ray,

trying to understand what you wrote. placing a horn over jacksonbart will not increase efficiency.....

by the way, can we make it a 24 volt marine system connected to jacksonbart? i think we should do a max spl test just for the sake of being thorough.

berryboy roy

[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.