most efficient speaker ever?

In 2Pi, 8.7%, JBL 2220H/E130.

The E130 can hit 105dB on axis, but that is due to narrowing pattern (increased directivity).

8.7% is 101.5dB/W/1M in 2Pi.

In a 4560 (short horn) they are about 104dB~105dB in the 200hz~500hz range.

When setting up large sound systems in auditoriums you need to subtract the directivity of the horns to compute how much gain/loss you will require between the HF and LF. With multiple 15's in some of these systems you may have to biamp because the LF will actually be more efficient than the HF.

RCA used autoformers in most of their big crossover networks so you could boost the HF as needed in the double Ubangi stacks. In a small space and nearfield listening it required a different crossver.

These required lowering the HF by 6dB for listening to in a garage at distances around 20 foot, a new network was designed and built using a calibrated mic and analyzer.

most efficient speaker ever?, posted on February 20, 2014 at 20:24:54
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Thanks for the nice photo of horns and directive baffles. From the JBL Pro website: http://www.jblpro.com/pub/obsolete/2220hj.pdf I see its sensitivity rating is actually 101db.

swing, posted on February 21, 2014 at 04:42:37

airairy
Audiophile

Posts: 43
Joined: July 19, 2008

bd desing swing- 115 db

wonderful horn speakers. one of the best out there

http://www.bd-design.nl/contents/en-us/d32.html

http://dagogo.com/2008-rmaf-coverage-13

most efficient speaker ever?, posted on February 21, 2014 at 06:10:21
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Again folks, thanks for the nice photo of horns or directional baffles. May I reiterate the question: What is the most efficient speaker ever made? I mean without a horn or directive baffles.

Community M4, posted on February 21, 2014 at 07:38:08
Zipcord Manufacturer Posts: 707 Location: No. California Joined: December 19, 2002	http://www.cuk-audio.com/uploads/files/Technical%20Papers/M4_WHITE_PAPER_TECH.pdf

most efficient speaker ever?, posted on February 21, 2014 at 10:19:53
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Thanks for the M4 link. I see Community measured the sensitivity on a horn. (Of course; it's a horn driver). Again, I'm asking: What is the most efficient speaker ever made? I mean without a horn or directive baffles. Anything over 104db? Maybe I should define the frequency range of my inquiry; below 200Hz.

Anything over 104db?, posted on February 21, 2014 at 12:32:06
Bill Fitzmaurice Industry Professional Posts: 5371 Location: New England Joined: October 20, 2002	Higher sensitivity is mainly the product of lower Qes, along with lower Mms, and both of those factors also result in less low frequency extension. So the short answer is higher than 104dB along with a range that extends below 200Hz is a combination you're probably not going to find.

Theoretical maximum, posted on February 21, 2014 at 12:57:00

Paul Joppa
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Location: Seattle, WA
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For what it's worth, I believe the theoretical maximum is 25%. That's only possible at one frequency - the high magnet strength reduces output below that frequency, and the directivity reduces power above that frequency. D. B. Keele worked it out more than 20 years ago (see link).

The 2220 mentioned by djk comes close to this target, with fs/Qt=200Hz and ka=1 at about 300Hz. So it may well be the real world practical maximum, within the piston range. Max efficiency happens when the moving mass equals the air load mass - around 15 grams for a 15" speaker. The 2220 has a moving mass of 70-100 grams depending on which cone kit is installed ...

Keele maximum-efficiency paper

RE: most efficient speaker ever?, posted on February 21, 2014 at 13:50:27
Scholl Distributor or Rep Posts: 1358 Joined: March 8, 2001	Google "The Wall of Sound" used by the Grateful Dead in the 70s. Run the numbers on their D130 stacks. I would guess 4, 16 ohm D130s in parallel could be the answer to your question. Might even have a little bass if they were in Onkens.

RE: swing, posted on February 21, 2014 at 13:55:27

tomservo
Manufacturer

Posts: 8206
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He said efficiency not sensitivity though.

100% efficiency would be 106dB 1w 1m. One can measure higher than that on axis but that is because the sound isn't radiated freely as normally assumed.
Over a reasonably wide dispersion angle like 50 by 50 degrees up high, it is VERY hard to get a sensitivity greater than about 100-103dB up at 15-20Khz and if one wants "flat response" that level also sets the maximum broadband sensitivity (as you have to knock down the rest to get to flat).
One can get a higher sensitivity mid-band but a humped response is not good to listen to.

I mean without a horn or directive baffles, posted on February 21, 2014 at 13:57:11
djk Manufacturer Posts: 6135 Joined: June 17, 2000	I own several M4, M200, M282, VHF100, etc. He did specify 'I mean without a horn or directive baffles' however.

RE: Theoretical maximum, posted on February 21, 2014 at 14:00:47
djk Manufacturer Posts: 6135 Joined: June 17, 2000	Yes, with coupling the theoretical limit for direct radiators will be about 25%. This would imply four drivers that were 6% efficent, Altec 515, JBL 2220, etc.

RE: most efficient speaker ever?, posted on February 21, 2014 at 14:09:23
tomservo Manufacturer Posts: 8206 Joined: July 4, 2002	But do you mean efficient at one frequency, one frequency range or what one might call efficient over a broad band?.

My Bad - both you and djk are correct, posted on February 21, 2014 at 14:41:56
Zipcord Manufacturer Posts: 707 Location: No. California Joined: December 19, 2002	Sorry about that - I should learn to read the entire post before replying

JBL graphs, posted on February 21, 2014 at 17:07:11
djk Manufacturer Posts: 6135 Joined: June 17, 2000

8.7%, posted on February 21, 2014 at 19:00:35
djk Manufacturer Posts: 6135 Joined: June 17, 2000	I have never seen a driver higher than No=8.7% (JBL 2220). See my response to BFM to see the JBL graph of the response in a 10 cu ft sealed box, it starts to roll at 200hz (hint: the EBP frequency).

my Avantgarde Duo Omegas are 107dB, posted on February 22, 2014 at 15:14:10
triode Audiophile Posts: 439 Location: south Florida Joined: January 18, 2001	though I don't know at what frequency, and of course the mid horn hands off to its active cone subs at 170Hz. "Your liver suffers dearly now for youthful magic moments...so rock on completely with some brand new components"

most efficient speaker ever?, posted on February 22, 2014 at 17:44:03
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Thank you for the AES article by Keele Jr.. It says the 30" is the most efficient speaker (Sec.4.2.6, pg. 15 and fig. 11, pg. 36). This would be the Electrovoice / University model 30W, correct?

RE: most efficient speaker ever?, posted on February 22, 2014 at 17:55:24
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	below 200 Hz band.

RE: my Avantgarde Duo Omegas are 107dB, posted on February 22, 2014 at 18:06:08
Bill Fitzmaurice Industry Professional Posts: 5371 Location: New England Joined: October 20, 2002	The OP specifically was asking about raw drivers, not that of a horn loaded speaker.

most efficient speaker ever?, posted on February 22, 2014 at 18:19:51

taxslave
Audiophile

Posts: 31
Location: New York
Joined: February 19, 2014

Your Avantgarde Duo Omega's are also horns in the mid and high. I asked: What is the most efficient speaker ever? And then I specified "I mean without horns or directional baffles" and I also specified the band "below 200Hz". I notice Avantgarde is making a big deal of the 18 ohm impedance. I wonder what they would say if they saw a 500 ohm speaker, as was common a ways back. I also notice no mention of how they measured 107 db. I'm sure those two 10' speakers are not anywhere near the sensitivity/efficiency of the Altec 515, the JBL 2220, or the 30W. Why else would they need a 250 Watt amp?

RE: most efficient speaker ever?, posted on February 22, 2014 at 18:23:54

tomservo
Manufacturer

Posts: 8206
Joined: July 4, 2002

If you’re talking about a direct radiator loudspeaker and for low frequencies, be aware that the low corner, box volume and efficiency are all tied together.
For example, if you have a box of volume X and change the driver to one optimal for an octave lower corner, you will lose 9dB in efficiency, period.

So, while box volume, low corner frequency and efficiency are unavoidably tied, there is also a limit to the parameters one can end up with in a driver so usually one gets a little less than the maximum possible.

So, at least here it’s easier than higher up, if you talking about a woofer (below 200Hz), at least the maximum possible efficiency that physics (as opposed to marketing) allows is set when you specify the low corner (-3dB point) and box internal volume.
Best,
Tom

most efficient speaker ever?, posted on February 22, 2014 at 18:26:34
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Thank you for the JBL graphs. It seems the 2220 is very limited by the 10 cu ft. sealed box in the band below 200 Hz. Probably not the best enclosure for that driver. It reaches 100 db only at 200 Hz.

RE: most efficient speaker ever?, posted on February 23, 2014 at 15:24:45
Bill Fitzmaurice Industry Professional Posts: 5371 Location: New England Joined: October 20, 2002	>. It seems the 2220 is very limited by the 10 cu ft. sealed box in the band below 200 Hz. That's not because of the box, it's because of the 0.18 Qes. It's better in a ported box, but still won't deliver more than 96dB below 100Hz, with a 180Hz f3.

RE: most efficient speaker ever?, posted on February 23, 2014 at 18:12:10
hottattoo Audiophile Posts: 141 Location: New York Joined: July 30, 2011	The Altec 515b comes close.

RE: swing, posted on February 24, 2014 at 10:17:26

nl
Audiophile

Posts: 730
Joined: March 18, 2002

I understand that 100-103db or so is about the max when using something like a 1" exit compression driver with constant directivity EQ (i.e. when not using narrowing dispersion to raise the on-axis response of HF). However, is this also true when using something like a super tweeter crossed in around 6Khz or so? It seems to me that you can get super tweeters in the 106-110 db range that have dispersion approximating perhaps 50 degrees.

RE: most efficient speaker ever?, posted on February 24, 2014 at 10:18:29

taxslave
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Posts: 31
Location: New York
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So what about the 30W? It has more surface area than four 15" speakers. Keele says the 30" is the most efficient. Is this correct? I also see many different sensitivity ratings for the 30W: 51 db EIA with 16 ohm coil (in the earliest literature), 54db EIA with 8 ohm coil (a few years later), 93.5 db "in suitable enclosure, at 10' on axis with 1 watt input" (several decades later), and 100db "Pink Noise band-limited from 500hz to 5KHz" (in the latest incarnation as the University 30W). The last sensitivity rating on the 30W makes no sense because the recommended crossover is 100Hz to 200Hz so they did not rate it for the frequency band they recommend using it with.

RE: most efficient speaker ever?, posted on February 24, 2014 at 20:12:03
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	Boxplot, JBL-Pro library, E130 in an "optimized" QB3 alignment (best you can do without equalization in a ported box) is -3dB at ca. 120Hz. Box is 1 cubic foot. Well, that's below 200Hz, but I would hardly call it bass. Face it, the D130/2220 is a 15-inch midrange. I'm actually using a 10" subwoofer with mine.

Fs=16hz, posted on February 25, 2014 at 14:03:29
djk Manufacturer Posts: 6135 Joined: June 17, 2000	I owned the EV version in the late 90's, it came from a Rodgers organ system (along with a LaScala). It had the cone area of four 15's, and so should have had the same coupling effect as four 15's. However, because of its 16hz Fs it wasn't all that efficient IIRC, only about 100dB or so. I'll check my records on an old computer at home if you really want to know.

RE: most efficient speaker ever?, posted on February 25, 2014 at 15:52:02

taxslave
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Posts: 31
Location: New York
Joined: February 19, 2014

One cubic foot internal volume for a JBL 2220 !?!? I think something may be wrong with the JBL box calculator program. I've had occasion to use 2220's and I remember the ported enclosures were about 6 to 8 cu. ft. and they had reasonable bass. Have you ever used the JBL 2123 for a mid range cone driver (101 db 1W 1M and a 250W Continuous pink noise power capacity) ? I have found them to be unbeatable in terms of detail and dynamics.

RE: most efficient speaker ever?, posted on February 25, 2014 at 20:03:52

Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001

Yeah, I have about 3 cubic feet at home and a huge Harlan (I think) with two D130s in a mono setup. The 3CF gets down to 80Hz, with a 300B amp so there's some Q-boosting form the low damping factor. But all of these are misalignments from the maximally-flat target; they have a suckout between the port resonance and the damping rolloff at fs/QT. Boxplot shows a -3dB dip around 125Hz for a 5CF box, tuned to make the peak march the midband. Room acoustics makes this hard to pinpoint so you can usually get away with it.

You think 1.0CF is small? The Butterworth sealed box is 0.5 cubic feet! -3dB at about 150Hz.

RE: most efficient speaker ever?, posted on February 26, 2014 at 13:43:34

Scholl
Distributor or Rep

Posts: 1358
Joined: March 8, 2001

I've heard them in Onkens with SET amps for decent bass. But for BR and sealed the don't do squat on bass.

Your best trade off for any kind of bass is 98 db. Model 19s are a good example. For bass below 30hz in a reasonable box 93-94db is the sweet spot.

If you run the numbers at the link below you'll find the 2123 falls far short of 101DB sens.

Relative Eff..

RE: most efficient speaker ever?, posted on February 26, 2014 at 20:55:52
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Thank you for the link to the nice looking calculator.The JBL professional spec sheet says the 2123H/J "half space reference efficiency shall be 3.5%". The mh-audio website you referenced calculates 3.16%. I'll bet JBL Pro actually measured the parameters but, believe what you will. The 2123 is still articulate and well defined at 120 db SPL and you'll have to get way back to appreciate it.

RE: most efficient speaker ever?, posted on February 27, 2014 at 04:09:41
Scholl Distributor or Rep Posts: 1358 Joined: March 8, 2001	I believe you. 2123s have been on my wish list. I use it's little brother the 2118 in my three way. I tried a bunch but always return to that one.

RE: most efficient speaker ever?, posted on February 27, 2014 at 06:48:55

taxslave
Audiophile

Posts: 31
Location: New York
Joined: February 19, 2014

I was wondering about this 1 Cu. Ft. "best you can do" enclosure for a 2220H, and who might recommend such an enclosure for that speaker when I realized it wasn't going to be JBL Pro.
I see from the JBL PRO Library that JBL uses a 5 Cu. Ft. enclosure and also includes a 25 Sq. Inch port with a 5 Inch duct to chart a representative response curve; I do not see a box plot program in the JBL library. Are you referring to the shareware program from Sparta Sound Co. by Rick Carlson called Boxplot? If so I feel sorry for folks using these online calculators to "design" speaker enclosures. One Cu.Ft. for a 2220h is ridiculous! JBL never used 2220H in such a tiny enclosure. The JBL Pro catalog recommends 6 to 10 Cu. Ft. for the 2220H/J. Although both are 15 inch, I should point out that E130 is a musical instrument speaker, not at all the same as 2220H sound reinforcement speaker.

RE: most efficient speaker ever?, posted on February 27, 2014 at 06:59:07
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Please excuse me; I see you did say D130, not E130 so disregard the comment about the E130 being different than the 2220H. The recommendations for larger enclosure volumes is still true and the 1 Cu. Ft. "best you can do" box volume is still ridiculous.

RE: most efficient speaker ever?, posted on February 27, 2014 at 16:02:04
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Well actually you said D130 AND E130. If you did your box plot on E130 parameters it may be recommending a small box because it's a guitar speaker.

RE: most efficient speaker ever?, posted on February 27, 2014 at 21:33:36

Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001

I have no real arguments with your observations.

The D130, E130, 130A, and 2220 are all very similar in terms of resonance, Q, and moving mass. I happen to have 2220s and D130s myself, and in fact my 2220s were re-coned by the dealer at different times and have different moving masses - 70 and 100 grams. So I don't usually worry too much about getting the parameters precisely correct ... :^)

Yes, the Thiele-Small optimized boxes are pretty silly looking. These drivers were designed before the A. N. Thiele's analysis was available, and much longer before it was widely known in the USA. Since I started this sub-thread to focus on theoretical limitations, I used the more modern analysis. Back in the day, I think JBL relied on experiment and listening, and their focus was on the best you could do with very high efficiency drivers, rather than choosing some optimum response shape and designing a driver to achieve it as is more often done today. There is much to be said for that older approach - it may be off optimum, but it usually sounds musical. Which the old JBL designs do, to my ear.

Do remember that, back in the day, it was quite common to have amplifiers with damping factors as low as 1.0. Some amps have that as a switchable option; my own Heathkit UA-1s are an example. Unity damping doubles the effective Q of the driver, and makes the 5CF boxes much closer to a Thiele-Small optimum 4th order Butterworth response. Theoretically, of course!

Incidentally - and this is speculation on my part - the D130/130A is a very old design, rooted in the era of movie theater sound with horn-loaded drivers. Their high efficiency and very low Q are ideal for horn loading, and many of the early JBL designs were done that way. The ported boxes were a domestic/studio adaptation to allow the use of these drivers in small boxes, back when anything less than 10 cubic feet was "small". Check the pre-1955 catalogs on the Lansing Heritage site to see haw many boxes were horn-loaded in one form or another.

15g moving mass, posted on February 28, 2014 at 06:54:16
Paul Scearce Audiophile Posts: 471 Joined: March 1, 2002	I just tried making a ~15g cone for a 15" driver. I used writing stateniory which is probably a bit heavier than copy paper. By itself, the cone weighed 9g. The paper shrank and warped at the glue seams. After handling the cone, I decided that even if I could keep the sides straight, it would probably not survive long in free air, much less the horn it was intended for.

RE: 15g moving mass, posted on February 28, 2014 at 12:49:15
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	Don't forget the weight of the voice coil! One of the secrets/features of the 2220 family is there is no VC overhang (outside the magnetic gap) so no wasted copper weight.

RE: 15g moving mass, posted on February 28, 2014 at 15:22:09
Paul Scearce Audiophile Posts: 471 Joined: March 1, 2002	The donor drivers for this project were wound with very nearly zero overhang. They used about 4g of 32gauge wire and hit 30Tm according to the impedance curve.

Yowza! (nt), posted on February 28, 2014 at 17:48:21
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	nt

RE: 15g moving mass, posted on March 4, 2014 at 13:39:32
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Isn't underhung is the most efficient because no wasted BL and also much less power compression and isn't the 2220 an underhung coil, as opposed to a hung or overhung coil? I thought by now someone would have mentioned the Aura 1808 and its successors. It was a very efficient LF driver with a 2" pole and a 1 " coil (1" linear excursion), used in the Wilson XS.

RE: 15g moving mass, posted on March 4, 2014 at 17:09:37

Paul Scearce
Audiophile

Posts: 471
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If the coil is under hung, you can use a larger gauge wire to increase the number of turns for your target resistance. This will increase motor strength until you reach evenly hung. At that point, using larger wire to add turns reduced motor strength, since fewer turns of the fatter wire can actually fit in the gap.

I think the main issue with evenly hung coils is that any excursion can cause modulation.

RE: most efficient speaker ever?, posted on March 13, 2014 at 19:48:00

Steve Schell
Manufacturer

Posts: 1440
Location: So. California
Joined: December 16, 2001

I learned about Mr. Frank Massa from Dr. Bruce Edgar, who read and understood the importance of his work, sought him out and interviewed him over lunch many years ago. This genius Massa was working at Victor Talking Machine Co. when RCA bought them out in 1929 to form RCA Victor. Massa worked at RCA on a variety of consumer, motion picture theatre and military loudspeaker projects until leaving them in 1938 to join Brush Development Company. While at RCA he collaborated with Harry F. Olson a great deal, and they co-authored a book, Applied Acoustics. I have long believed that many of the innovations attributed to Olson were at least partly inspired by Massa.

Massa was fascinated by the concept of a highly efficient direct radiator loudspeaker. He spoke about his concepts in various articles, in patent applications, and with Dr. Edgar over lunch. Those interested should carefully read his U.S. Patent #2,445,276 (link below). I am not sure to what extent his musings were theoretical or whether he actually built and tested these things, but I have verified his findings to some extent in my own work.

Elsewhere in his writings (if memory serves) Massa spoke of loudspeaker efficiencies as high as 80%, obtained by horn loading both sides of a compression driver diaphragm.

F. Massa Electrodynamic Loudspeaker

RE: most efficient speaker ever?, posted on March 20, 2014 at 19:31:42

taxslave
Audiophile

Posts: 31
Location: New York
Joined: February 19, 2014

Thank you Steve Schell for the link to the Massa patent, it is fascinating reading. He has a different way of looking at the electrical equivalent circuit than his contemporary, H F Olson. It makes sense, at least for hung or overhung voice coils, if you consider the center pole piece as a core for the voice coil. I calculated voice coil dimensions for his new coil design for one particular example and I doubt he would have been able to get a gap wide enough to accommodate it with a strong enough field strength to do what he says. I'm re-reading it now to see what I missed but may I ask; what of his findings have you verified?

RE: most efficient speaker ever?, posted on March 25, 2014 at 19:08:51
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	So I've re-read it close enough to find the proofreading error in column 6, number 5, where he defines D as the "effective diameter of the voice coil in inches". I'm not sure how his voice coil would stay together especially considering the adhesives available in 1945. Checking his math now. I'm still interested in what you've verified Steve.

RE: most efficient speaker ever?, posted on April 21, 2014 at 11:03:05
stav56 Audiophile Posts: 1 Joined: April 21, 2014	Frazier Model Eleven... 107dB

RE: most efficient speaker ever?, posted on April 21, 2014 at 15:36:15
taxslave Audiophile Posts: 31 Location: New York Joined: February 19, 2014	Frazier has not been truthful. CTS Piezo tweeters are only 94db, and I'm sure the rest of the drivers are close to that or this speaker would sound very dark. There are no 5" mid or 12" woofer direct radiator speakers with a 107 db sensitivity so it doesn't add up. "Believe nothing of what you hear, 10% of what you read, and only 50% of what you see with your own eyes."---Robert Beers.

RE: most efficient speaker ever?, posted on April 30, 2014 at 07:01:30
s4s4s4 Dealer Posts: 8 Joined: March 9, 2008	Magico claim 116db for their Ultimate 3 speakers

High Efficiency Speaker Asylum

most efficient speaker ever?

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