Lynn Olson said:
I don't think that's quite the story. But just because one guy said a bunch of things doesn't mean that he couldn't have made a mistake:
"Titanium does not have the internal damping of aluminum."
I have no idea where this came from. The reference I have is a paper from Pioneer called "New Materials for Loudspeaker Cones and Diaphragms -- An Overview". There is a table that lists the properties of many potential diaphragm materials. Comparing Ti and Al gives the following:
Youngs Modulus (x10^6 N/m^2)
Aluminum = 7.0
Titanium = 10
Density (x10^3kg/m^3)
Aluminum = 2.7
Titanium = 4.5
Specific Modulus (x10^7(m/s)^2)
Aluminum 2.6
Titanium 2.2
Sound Velocity (x10^3m/s)
Aluminum 5.1
Titanium 4.7
Internal Loss (tan delta)
Aluminum = 0.002
Titanium = 0.002
Melting Point (C)
Aluminum = 660
Titanium = 1668
So I think that either Button misspoke or he was referring to an insignificant difference in damping.
The fact that he then says that this leads to "marginally higher distortion levels" is curious. If the diaphragm is operating pistonically, the damping is meaningless and will have no effect whatsoever on distortion. On the other hand if you examine the plots of distortion for metal dome tweeters you will see peaks at sub-harmonics of the break up mode. For example if the tweeter breaks up at 26 kHz with a 10 dB peak, you will see a rise in second harmonic distortion at 13 kHz.
Now if there were a significant difference in internal damping, this would show up as a significant size of the break-up peak. So if Button's assertion were true, an aluminum dome tweeter might only have a 5 dB peak at breakup while a titanium dome tweeter would have a 10 dB peak. But this is simply not the case. Go look at any metal dome tweeters you care to. They all have peaks of roughly 10 dB, regardless of the metal used.
I can buy the rest of what he says, but only if you put it into the proper context.
"The diamond surrounds, while extending frequency response, do so at the expense of transient response."
The only way I can interpret this is that with a large format diaphragm (4"), the response naturally falls off sharply above 10 kHz. This can be "corrected" by adding a resonant element (in this case the surround) that is designed to add resonant energy in the frequency range that would otherwise be rolling off. Apparently they designed the surround to resonate in the 10 to 15 kHz region. And of course any resonating structure will have time smear that will degrade the "transient response". But blaming this on the titanium per se is missing the point entirely.
"Further, due to its lower stiffness, titanium goes into breakup at a lower frequency."
Actually, Ti has *greater* stiffness. It is the extra density that causes the problem, but we are only talking about a 5% to 10% difference at most for the difference in break up frequencies. Elsewhere Button mentions 7 kHz for Al and 4 kHz for Ti. This is clearly in error. I would assume that he simply misspoke and that there was no intention of deliberately misleading anyone.
"The only way I can interpret this is that with a large format diaphragm (4"), the response naturally falls off sharply above 10 kHz. This can be "corrected" by adding a resonant element (in this case the surround) that is designed to add resonant energy in the frequency range that would otherwise be rolling off. Apparently they designed the surround to resonate in the 10 to 15 kHz region. And of course any resonating structure will have time smear that will degrade the "transient response". But blaming this on the titanium per se is missing the point entirely."
Take a look at the original patent that I posted a link too. The original diamond surrounds were aluminum so they both had the "issue" with transient response however the fatigue/reliability differences between aluminum and Ti when used with this surround configuration are why they made the change over. If you want both the extended response and reliability Titanium is the obvious choice.
Rob
Take a look at the original patent that I posted a link too. The original diamond surrounds were aluminum so they both had the "issue" with transient response however the fatigue/reliability differences between aluminum and Ti when used with this surround configuration are why they made the change over. If you want both the extended response and reliability Titanium is the obvious choice.
Rob
Lynn Olson said:
Linkwitz's 3-way Orion+ uses LR4 crossovers at 120Hz and 1440Hz, putting most of human voice on one 8" Seas speaker. I think Orion's wide BW midrange is one of the major reasons for its positive reviews. Using modern speaker and Xover technology to get as much of the 80Hz-1,500Hz vocal range on the midrange in a 3-way gives the best coherence and tone to vocals to my ears.
When Lynn locked-in the RAAL double ribbon, I thought the key challenge would be finding a paper/hemp cone 10" with dipole-suitable T/S which had good SPL dynamics, great vocals, and acceptable off-axis response. It may take another 1,000 posts, but my bet is still on a 10" midrange over any midrange horn.
10" dipole midrange crossed 1300 Hz to double high RAAL
* NdFeB motor small size for optimized rear dipole wave
* BL~18
* Mms ~35g
* Le ~0.03mH
* Fs ~40Hz no cone breakup out to 3Khz
* Qts ~ 0.5
* Re=16 ohms to increase Qts
* underhung motor with 10mm Xmax
* ~95db SPL at 1 watt
* curvelinear paper or hemp cone
* long aluminun phase plug
John_E_Janowitz said:
Complex is how you look at it.
Yes, to compute the actual heat transefer there is a need to consider convection and radiation in the gap and conduction between pole piece and phase plug, etc. But the physics is pretty simple. As you note the phase plug increases thermal mass. This would mean it takes longer to heat up and cool down. More importantly the phase plug will increase the area for heat rejection to the surrounding, as you note, meaning the pole piece whould run cooler for a given power into the VC. It follows that since the pole piece will run cooler that heat can be transfered to the pole piece from the VC and VC former at a higher rate with result that the VC should run cooler, still hotter than the phase plug (on average during operation) but cooler than w/o the phase plug. Obviously we are in agreement. I was just put off by your initial comment.
Talk about going green, loudspeakers are about the most inefficient device man has come up with yet. Can you imaging what the price of gas would be is we only extracted 5% or 10% of the energy from a gallon of gas in our cars.
Magnetar said:
Magnetar, please don`t leave us. I think your input is valuable in this thread (and other threads).
I think this is a great thread, even if not much is beeing made yet.
Yesterday I got a bunch of drivers from Italy to play with
18sound:
Four 18nd930, four 18nd9300 and eight 6nd410.
Lots of things to try, dipoles, horns, sealed, aperiodic, unity horn, etc..etc....
First one up is a crossbreed between a dipole and aperiodic damping, hyper cardoid pattern. I guess it will be fairly inefficient, but good transient performance.
Making sawdust allmost as we speak.
Best regards,
Peter
More History
Here are more articles on compression drivers, horns, and theater loudspeakers:
1928, Western Electric & WJ Farmer, Aluminum Alloys for Diaphragms. Note the photo of the Western Electric 555 diaphragm with a tangential surround, used in the first movie-sound systems. (In 1928, movie-sound was synchronized sound-on-disc, not the optical system that was developed in the early Thirties by WE and RCA.)
1934, Wente & Thuras, Loud Speakers and Microphones. This is a description of the Bell Labs speakers used in the first public demonstration of stereophonic sound, the 3-channel Bell System relay between Symphony Hall in Philadelphia to Constitution Hall in Washington, D.C.
1936, JK Hilliard, Shearer Theater Loudspeaker. The predecessor to the Altec A2 Voice of the Theater, which became the world standard from 1945 to the early Eighties. The A2 removed the folded bass horn, replacing it with a short horn with no folds, and changed the suspension of the 284 compression driver from circumferential/corrugated to the tangential suspension of the 288.
1937, Western Electric & RC Miner, Mirrophonic Speaker System. This is a commercial development (for movie theaters) of the Auditory Perspective system used in the 1934 demonstrations. Note the following article on the merits of stereophonic sound in theaters - remember, this is 1937!
1952, University Sound & AB Cohen, Wide-Angle Dispersion of High-Frequency Sound. This "reverse-flare" horn is apparently the first constant-directivity horn. The flare discontinuities of the Altec Manta-Ray and the JBL Bi-Radial make their first appearance here.
1978, Altec & Henricksen, Radial vs Circumferential Phase Plugs. This is the Altec "Tangerine" phase-plug, a refinement of the earlier Hilliard radial phase plug dating back to the early Forties.
1979, JBL & FM Murray & HM Durbin, 3-Dimensional Diaphragm Suspensions for Compression Drivers. This is the Engineering Report describing the JBL "diamond suspension". Apparently, it was developed as a response to quality-control problems with the tangential suspension in the JBL 2420 compression-driver diaphragm.
1995, Dr. Holland & FJ Fahy & PR Newell, The Sound of Midrange Horns for Studio Monitors. This is the famous (or notorious) study, done in an anechoic chamber at the ISVR with the drivers hidden behind a screen, to discover if a group of 20 recording-industry professionals could reliably distinguish "horn sound". Two groups of horns & drivers emerged: the first had noticeable horn colorations, and the second sounded more like the Audax PR170 used as one of the references.
The only two horns that were never identified as horns by any of the listeners, interestingly enough, were the Altec 1005 multicell and their own AX2 horn. This is also the study that recommended avoiding any kind of discontinuity in the horn flare, and keeping the overall distance between the horn-mouth and diaphragm less than 340mm.
Here are more articles on compression drivers, horns, and theater loudspeakers:
1928, Western Electric & WJ Farmer, Aluminum Alloys for Diaphragms. Note the photo of the Western Electric 555 diaphragm with a tangential surround, used in the first movie-sound systems. (In 1928, movie-sound was synchronized sound-on-disc, not the optical system that was developed in the early Thirties by WE and RCA.)
1934, Wente & Thuras, Loud Speakers and Microphones. This is a description of the Bell Labs speakers used in the first public demonstration of stereophonic sound, the 3-channel Bell System relay between Symphony Hall in Philadelphia to Constitution Hall in Washington, D.C.
1936, JK Hilliard, Shearer Theater Loudspeaker. The predecessor to the Altec A2 Voice of the Theater, which became the world standard from 1945 to the early Eighties. The A2 removed the folded bass horn, replacing it with a short horn with no folds, and changed the suspension of the 284 compression driver from circumferential/corrugated to the tangential suspension of the 288.
1937, Western Electric & RC Miner, Mirrophonic Speaker System. This is a commercial development (for movie theaters) of the Auditory Perspective system used in the 1934 demonstrations. Note the following article on the merits of stereophonic sound in theaters - remember, this is 1937!
1952, University Sound & AB Cohen, Wide-Angle Dispersion of High-Frequency Sound. This "reverse-flare" horn is apparently the first constant-directivity horn. The flare discontinuities of the Altec Manta-Ray and the JBL Bi-Radial make their first appearance here.
1978, Altec & Henricksen, Radial vs Circumferential Phase Plugs. This is the Altec "Tangerine" phase-plug, a refinement of the earlier Hilliard radial phase plug dating back to the early Forties.
1979, JBL & FM Murray & HM Durbin, 3-Dimensional Diaphragm Suspensions for Compression Drivers. This is the Engineering Report describing the JBL "diamond suspension". Apparently, it was developed as a response to quality-control problems with the tangential suspension in the JBL 2420 compression-driver diaphragm.
1995, Dr. Holland & FJ Fahy & PR Newell, The Sound of Midrange Horns for Studio Monitors. This is the famous (or notorious) study, done in an anechoic chamber at the ISVR with the drivers hidden behind a screen, to discover if a group of 20 recording-industry professionals could reliably distinguish "horn sound". Two groups of horns & drivers emerged: the first had noticeable horn colorations, and the second sounded more like the Audax PR170 used as one of the references.
The only two horns that were never identified as horns by any of the listeners, interestingly enough, were the Altec 1005 multicell and their own AX2 horn. This is also the study that recommended avoiding any kind of discontinuity in the horn flare, and keeping the overall distance between the horn-mouth and diaphragm less than 340mm.
Hello Lynn
The 1952 Reverse Flair horn I don't believe is the starting point for the modern CD horn. If I am not mistaken it goes back to 1975 and D.B. Keele's work at Electro Voice.
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1975-05%20AES%20Preprint)%20-%20Whats%20So%20Sacred%20Exp%20Horns.pdf
"This is the Engineering Report describing the JBL "diamond suspension". Apparently, it was developed as a response to quality-control problems with the tangential suspension in the JBL 2420 compression-driver diaphragm."
How did you come to that conclusion?
The actual patent is posted a couple posts back. The reason is to extend the bandwidth. Both the tangential surround and the half roll crash due to a secondary resonance from their suspensions. This type allows you to control where this resonance occurs and allows you to effectively extend the bandwidth of the driver.
"The only two horns that were never identified as horns by any of the listeners,"
That not what it says. There are contradictory statements in the text. Here's an example page 10:
"Only one short horn, sample 11, was ever identified as a horn and then only by one "golden eared" professional sound engineer."
From that statement I would conclude that none of the short horns were identified as horns
I can see why it was infamous. You can interpret it either way. The main thing is to keep the horns short and obstruction free.
Rob
The 1952 Reverse Flair horn I don't believe is the starting point for the modern CD horn. If I am not mistaken it goes back to 1975 and D.B. Keele's work at Electro Voice.
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1975-05%20AES%20Preprint)%20-%20Whats%20So%20Sacred%20Exp%20Horns.pdf
"This is the Engineering Report describing the JBL "diamond suspension". Apparently, it was developed as a response to quality-control problems with the tangential suspension in the JBL 2420 compression-driver diaphragm."
How did you come to that conclusion?
The actual patent is posted a couple posts back. The reason is to extend the bandwidth. Both the tangential surround and the half roll crash due to a secondary resonance from their suspensions. This type allows you to control where this resonance occurs and allows you to effectively extend the bandwidth of the driver.
"The only two horns that were never identified as horns by any of the listeners,"
That not what it says. There are contradictory statements in the text. Here's an example page 10:
"Only one short horn, sample 11, was ever identified as a horn and then only by one "golden eared" professional sound engineer."
From that statement I would conclude that none of the short horns were identified as horns
I can see why it was infamous. You can interpret it either way. The main thing is to keep the horns short and obstruction free.
Rob
so, I make wrong decison with 399 maybe in some next project.
I am very amateur...
"If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe." Capppy- yes, perfect quote for this situation.
I was trying single raal 14-150 with altec biflex and raal is too fast. The blend is not seamless
I have to look for another drivers.
Some advice from DIY friends?
Lynn sorry for disturb Your thraed...
And sorry for me english.
Best
C
maybe in some next project.I am very amateur...
"If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe." Capppy- yes, perfect quote for this situation.
I was trying single raal 14-150 with altec biflex and raal is too fast. The blend is not seamless
I have to look for another drivers.
Some advice from DIY friends?
Lynn sorry for disturb Your thraed...
And sorry for me english.
Best
C
Robh3606 said:
Well, the design goals of the University "Reverse Flare" are similar, although certainly poorly argued, and it does precede Keele's work by 23 years. Just as the AR-1 loudspeaker preceded the publication of Neville Thiele and Richard Small by nearly twenty years, I believe prior art, no matter how crudely realized, needs to be given credit. I believe the tendency in audio to minimize, or simply forget, the past has been extremely destructive to continued forward progress, since it leads to re-inventing the wheel over and over again.
From page 723:
Shifting back to a 200-200 000-Hz range, Fig. 8 shows the motional impedance of a rejected transducer. The second pole is just as high (amplitudewise) as it was in Fig. 6, but now it appears at 22 kHz, where it is swamped by the difference inductance mentioned above. Fig. 9 shows the response and impedance curves of this "bad" transducer. Because the second pole is at a higher frequency, it is unable to participate in lifting the frequency response in the 15-kHz region, and the transducer tends to follow a much more "theoretical" curve based on a simple parallel tank circuit for motional impedance. There is some increased output above 19 kHz, resulting from this high-frequency pole, but it comes too late to be of use at audio frequencies. The response of the "good" transducer is shown for comparison. It is well to note the dimensional differences between these two transducers are of the order of 0.003 mm and cannot be readily determined before the transducer is assembled.
6 A New Transducer
Because the tangential surround is so highly sensitive to small dimensional differences, the diamond-shaped pattern of Fig. 3(b) is incorporated into the 45-mm transducer. This pattern seems to be less sensitive, and uniformity is easier to achieve.
The impedance curves for this new transducer are shown in Fig. 10. This shows a well-defined pole at 16 kHz and some additional activity between 30 and 50 kHz. This additional activity will be investigated at a later date. The audiofrequency response range is illustrated in Fig. 11 and shows smooth response to the 16-kHz second pole.
I've worked in manufacturing at Audionics and Tektronix. The problem with the tangential surround could be described as a quality-control issue, a product that is difficult to manufacture consistently, or a fundamental engineering problem. All are valid points of view. Altec continued to manufacture the tangential surround, JBL changed over to the diamond surround, and Emilar & Radian made plastic surrounds.
The argument in the original paper is a bit of a straw-man argument, since we are never shown measurement data from a "bad", out-of-spec diaphragm using the new technology. Maybe the new diaphragms are all perfect? This seems unlikely in any manufacturing environment - there's always a certain percentage of duds.
We are shown "good" old technology, "bad" old technology, a "good" example of the new technology, and no statistical data on the rejection rate of old and new. The paper would be a little stronger if this had been shown.
"The only two horns that were never identified as horns by any of the listeners,"
That not what it says. There are contradictory statements in the text. Here's an example page 10:
"Only one short horn, sample 11, was ever identified as a horn and then only by one "golden eared" professional sound engineer."
From that statement I would conclude that none of the short horns were identified as horns
I can see why it was infamous. You can interpret it either way. The main thing is to keep the horns short and obstruction free.
Rob
From page 32 of Holland and Newell:
These two hypotheses agree with the observation that of the two horns in the test that produce negligible mouth reflections, samples 8 and 13, neither was ever identified as a horn, and the short horn, sample 8, did not sound like the direct-radiating reference B.
From Appendix 1:
Reference B: Son Audax PR17/HR100/1AK7. Midrange direct-radiating paper-cone loudspeaker of nominal 6 1/2-in (165-mm) diameter.
...
Sample 8: AX2 horn/Emilar EK175 driver. Short axisymmetric horn of glass-fiber construction with rapid flare terminating in a medium-size mouth. Compression driver as sample 1.
...
Sample 13: Altec 806C horn/Emilar EK175 driver. Large multicellular horn with eight individual flares of sheet aluminum construction joined to a single throat via a cast aluminum manifold. Compression driver as sample 1.
I agree this paper is problematic, with the much larger Altec 806 multicell grouped with the much smaller AX2 horn. The Altec is 600mm long yet is never identified as a horn, is claimed (without evidence) that the mouth produces "negligible" reflections, and obviously has internal reflections in the area where the transition from the round-throat compression driver is made to a square-section throat which changes again to the square entrances of the eight smaller sub-horns. On the basis of diffraction alone, that would seem to put the multicell in the worst possible category.
Yet I am forced to agree, at least in purely subjective terms, with the conclusion. I've heard large Altec multicells for myself, and was surprised at how low the horn coloration seemed to be - certainly in a different class than Altec sectorals or JBL Bi-Radials, which to me have a fair amount of horn coloration.
More
1966, JK Hilliard & JA Renkus, Development of Horn-Type Moving Coil Driver Unit. The predecessor of the Emilar and Radian family of aluminum-diaphragm, plastic-surround compression drivers. I am not sure if Altec ever produced this 4-inch diaphragm unit.
2002, Voishvillo, Nonlinearity in Horn Drivers. An interesting mathematical model of the sources of compression-driver distortion, compared against measurements of a real-world driver and horn. Note the 12V input to the test system (page 20) results in 120 dB SPL at one meter - a level high enough to destroy audiophile-efficiency loudspeakers, where it would correspond to a kilowatt (or more) of amplifier power.
1966, JK Hilliard & JA Renkus, Development of Horn-Type Moving Coil Driver Unit. The predecessor of the Emilar and Radian family of aluminum-diaphragm, plastic-surround compression drivers. I am not sure if Altec ever produced this 4-inch diaphragm unit.
2002, Voishvillo, Nonlinearity in Horn Drivers. An interesting mathematical model of the sources of compression-driver distortion, compared against measurements of a real-world driver and horn. Note the 12V input to the test system (page 20) results in 120 dB SPL at one meter - a level high enough to destroy audiophile-efficiency loudspeakers, where it would correspond to a kilowatt (or more) of amplifier power.
caninus80 said:so, I make wrong decison with 399
I was trying single raal 14-150 with altec biflex and raal is too fast. The blend is not seamless. I have to look for another drivers.
Some advice from DIY friends?
Best
C
You can look at the problem of blending the ribbon (any ribbon) with the Altec Biflex in terms of moving masses - never mind the frequency-response data, it's not going to easy to match moving masses that are more than 100X different. The mass of a ribbon is measured in milligrams, and due to its low mass and relatively large area, receives almost all of its damping from the air-load. True ribbon loudspeakers are little more than scaled-up microphones - more elegant control of the shape of the magnetic field in the gap, clever damping patterns on the ribbon, different tensioning systems, etc. etc. but they really are just big microphones.
The inverse is true of a cone driver working at the top of its usable range. The mass is anywhere from 20 to 70 grams for a typical midbass driver, and is strongly decoupled from the voice coil at the highest frequencies. Any damping that is present is a side-effect of losses in the mechanical construction of the diaphragm and details of the surround damping. With the big diaphragm going so many ways all at once, the dispersion pattern is going to be very level and frequency-dependent.
These dissimilarities appear in measurements of the distortion spectrum, energy storage in the CSD, and "clutter" in the tail of the impulse response. These measurements are only indirect indicators of very different acoustic radiators - and the ear is very good at identifying what acoustic radiators are made of. Heavy masses sound heavy, light masses sound light.
In subjective terms, all that comes to mind to blend the woofer and the ribbon are low-mass aluminum-cone drivers, like a 4X, 8X, or 16X array of the small Jordan-Watts (or clones), or (again) a compression driver with a well-behaved horn (and those aren't common). That gets the diaphragm masses down to a few grams, and extends HF respond well into the ribbon's natural territory.
Ideally, the array of little metal-cone drivers, or the compression driver, should have good enough HF response the ribbon isn't really necessary, and is just a nice add-on to give the speaker a bit more "air" and openness at the top of the range.
The Altec Biflex, although a very nice speaker, isn't really full-range. Frankly, neither are Fostex, Lowther, or Feastrex whizzer-cone drivers. Yes, they have output beyond 10 kHz, but the extreme-HF quality isn't there - the whizzer cones are so thoroughly decoupled at those frequencies there is almost no damping at all, and impulse and polar responses are chaotic.
Well, I've never heard the PHY's, so any endorsement of them is cautious at best. On the other hand, Alexander, designer and builder of the RAAL ribbons, has suggested to me (more than once) the PHY midbass drivers, as well as vertical arrays of small metal-cone woofers, so you can take that for what it's worth.
Lynn, I haven't had time to thoroughly read all of the papers you've linked, but it seems they all deal with metal and phenolic diaphrams. Any particular reason you're not mentioning the mylar/polyester diaphrammed units such as the Beyma CP380 and 385? Meant more theoretically than neccessarily relating tho those particular drivers. I have experience with the 380 and I beleive Duke (audiokinesis) uses the 385.
Lynn Olson said:
Lynn,
Gracious thanks for that. I understand your position (and have to agree) that PHY -- and the likes of Supravox, Fertin, PHL etc -- might prove to be nothing more than a "costly experiment" if things do not blend nicely.
In the mean time I established contact Alexander and I'm waiting to get his impressions and experiences with those drivers. We'll see.
Thanks again,
Florian
Midbass + mid alternative to single WB
Lynn,
Did you get a chance to listen to (and measure) the 12NDA520 and 6ND410 you received some time ago ?
Any further thoughts on this XO topology ?
Regards,
Florian
Lynn,
Did you get a chance to listen to (and measure) the 12NDA520 and 6ND410 you received some time ago ?
Any further thoughts on this XO topology ?
Regards,
Florian
caninus80 said:
I was trying single raal 14-150 with altec biflex and raal is too fast. The blend is not seamless
I have to look for another drivers.
Some advice from DIY friends?
Lynn sorry for disturb Your thraed...
And sorry for me english.
Best
C
Try the altec driver inverted and radial, like a "walsh" driver (or DDD bending wave driver).