Hi Aleksander. Good points, but I've always defined the 'ideal dipole' as per Linkwitz, which is -1dB at 30deg, -3dB at 45deg, -6dB at 60deg, and at least -25dB at 90deg. See this page and this page for references from his website.
So by that definition, the neo3pdr is very close to ideal.
Personally, errors above 6kHz or so, I worry much less about. This is based on my experience with drivers, and playing with headphones and EQ. I record musician as a hobby, so I do this stuff some.
I've played with room absorption a bit, and don't do it anymore. I find that my room, with enough stuff in it, has satisfactory performance, especially in the treble. I also put a lot of creedence in the findings of Floyd Toole, et al, because he has done uniquely large scale studies of psychoacoustics. One of his findings, and which Linkwitz agrees with, is that sidewall reflections are not something to be particularly concerned with. Toole's studies have found them to be beneficial to the sense of envelopment, which people tend to like. I highly recommend Toole's book, Sound Reproduction, to anyone who hasn't read it - it is the most thorough and modern book on what is important when it comes to acoustics, psychoacoustics, and sound reproductions. No one else had done as large scale studies as he has.
So by that definition, the neo3pdr is very close to ideal.
Personally, errors above 6kHz or so, I worry much less about. This is based on my experience with drivers, and playing with headphones and EQ. I record musician as a hobby, so I do this stuff some.
I've played with room absorption a bit, and don't do it anymore. I find that my room, with enough stuff in it, has satisfactory performance, especially in the treble. I also put a lot of creedence in the findings of Floyd Toole, et al, because he has done uniquely large scale studies of psychoacoustics. One of his findings, and which Linkwitz agrees with, is that sidewall reflections are not something to be particularly concerned with. Toole's studies have found them to be beneficial to the sense of envelopment, which people tend to like. I highly recommend Toole's book, Sound Reproduction, to anyone who hasn't read it - it is the most thorough and modern book on what is important when it comes to acoustics, psychoacoustics, and sound reproductions. No one else had done as large scale studies as he has.
I agree with you - but I would add the the area just below that, from 1kHz to 4kHz, is very very important. Mess with that area, and you will notice it. The issue with dipole tweeters is that most are too large, and cause errors in just this area. Hence this thread, I think...
Goes as cos(theta) so half power's at 60 degrees as cuibono mentioned. The point source dipole model is conceptually useful but since actual drivers are acoustically large directivity's better than what you're describing. Like any driver, peak/dip EQ is needed for the dipole peaks and nulls. Once that's applied the non-PDR Neo3 produces consistent directivity within my measurement limits up to about 8.5kHz. The PDR version's a bit less consistent but it's not bad either.
Hmm, looks like entry level pricing's around USD 2500. That's about USD 1000 more than my entire system so it ain't happening for me; even finding a used 8.5 the upgrade to 10 is 999 Euro. Thanks, though.
Whoa! I'm off by a laaarge margin! Then, very impressive result you have there!
I officially declare the most part of my previous post as **, coming from ignorance and I apologize for being an ****.
Since those are the numbers (thank you), it means that 67 mm wide "baffle" of Neo3PDR will extend the dipole behavior all the way up to at least 6k cleanly.
Now I'm even more interested in the nature of that 9k anomaly.
I strongly suspect the 9k anomaly has mostly to do with Neo3 being bare naked. Can you frame it up somehow, keeping the same overall size, but getting rid of that edge-step and see if it helps? What is that soft, oily, pliable putty that always stays soft and is easily shaped called in English?
I wonder how far it will go, given the size, if the anomaly wasn't there and it makes me wonder how far the dipole ribbon will go, given it's size and pear shape. I thought it won't go far up, but it just might go up enough...I'll do some measurements these days.
You have an interesting observation about 1 to 4k. Most "empty" rooms sound harsh and annoying right there, so having dipole response in that region will certainly help.
Haven't read Toole's book, aside from some papers published in AES Journal, but I know that Linkwitz agrees with side reflections issue.
I tend to agree with that, but only up to an extent, as they tend to smear the focus in the middle of stereo image. I don't know if Toole and Linkwitz specifically mention that, but from my experience, I need to emphasize the importance of having speakers very, very accurately symmetrically positioned, with less than 1cm error between left and right channel. Whatever the distance from side walls, it must be right-left equal, as well as from the back wall. Equally important is the symmetry of furnishing the room. Cabinets, sofas, chairs, tables, anything, wherever it is, especially in region from the wall behind the speakers all the way to the listening position must be symmetrical. Also, move away the table in front of the listener when listening, if it's wide enough to reflect the direct sound towards the listener. Push it all the way to between the speakers, if you can't put it behind you. If you don't, it will force the image down and smear the focus again.
The side wall distance error will easily be heard like sibilants that aren't having the same position in stereo image like the bulk of the vocal. For an inch of positioning error, if the tweeter is about 2 - 2.5 feet from the side wall, the offset is about 4-5 inches in stereo image and it's very annoying.
That is why I consider this 8-9k anomaly very dangerous as it will probably emphasize the positioning error as sibilants are falling right in it.
Omnis are particularly sensitive to symmetry errors in layout, whatever the side wall distance may be, even 6 feet, and you have more of an omni thing going on in sibilants than anything else. (Most people never heard omni speaker accurately positioned in a symmetrically furnished room and attribute the focus smearing to "nature of the omnis". Earl Geddes once dropped in my room at CES with large omnis and didn't like the focus, of course. Neither have I, but he was kinda' deaf to my explanation that because we weren't allowed to move this darn TV cabinet, we had to move both speakers towards right, as well as the listening position, and all symmetry was lost. It still sounded better than having the TV cabinet almost in front of the left speaker. I'll never exhibit anything again at stupid Venetian, BTW).
Dangerous game this is. Many manufacturers when exhibit at shows, place speakers very poorly and furnish the rooms disregarding symmetry. Actually, accurately laid out monopoles will whoop the **** of inaccurately laid out dipoles any day, and you can hear it going on all the time at audio shows.
I know audiophiles spending their entire audiophile "career" listening to poorly laid out rooms and speakers within, spending megabucks on new gear, hoping they'll get lucky, but for some incomprehensive reason to me, fail to listen when you tell them they should play with positioning.
I can't even begin to explain how important the room layout is and how often it's the more decisive factor than the speaker itself.
I officially declare the most part of my previous post as **, coming from ignorance and I apologize for being an ****.
Since those are the numbers (thank you), it means that 67 mm wide "baffle" of Neo3PDR will extend the dipole behavior all the way up to at least 6k cleanly.
Now I'm even more interested in the nature of that 9k anomaly.
I strongly suspect the 9k anomaly has mostly to do with Neo3 being bare naked. Can you frame it up somehow, keeping the same overall size, but getting rid of that edge-step and see if it helps? What is that soft, oily, pliable putty that always stays soft and is easily shaped called in English?
I wonder how far it will go, given the size, if the anomaly wasn't there and it makes me wonder how far the dipole ribbon will go, given it's size and pear shape. I thought it won't go far up, but it just might go up enough...I'll do some measurements these days.
You have an interesting observation about 1 to 4k. Most "empty" rooms sound harsh and annoying right there, so having dipole response in that region will certainly help.
Haven't read Toole's book, aside from some papers published in AES Journal, but I know that Linkwitz agrees with side reflections issue.
I tend to agree with that, but only up to an extent, as they tend to smear the focus in the middle of stereo image. I don't know if Toole and Linkwitz specifically mention that, but from my experience, I need to emphasize the importance of having speakers very, very accurately symmetrically positioned, with less than 1cm error between left and right channel. Whatever the distance from side walls, it must be right-left equal, as well as from the back wall. Equally important is the symmetry of furnishing the room. Cabinets, sofas, chairs, tables, anything, wherever it is, especially in region from the wall behind the speakers all the way to the listening position must be symmetrical. Also, move away the table in front of the listener when listening, if it's wide enough to reflect the direct sound towards the listener. Push it all the way to between the speakers, if you can't put it behind you. If you don't, it will force the image down and smear the focus again.
The side wall distance error will easily be heard like sibilants that aren't having the same position in stereo image like the bulk of the vocal. For an inch of positioning error, if the tweeter is about 2 - 2.5 feet from the side wall, the offset is about 4-5 inches in stereo image and it's very annoying.
That is why I consider this 8-9k anomaly very dangerous as it will probably emphasize the positioning error as sibilants are falling right in it.
Omnis are particularly sensitive to symmetry errors in layout, whatever the side wall distance may be, even 6 feet, and you have more of an omni thing going on in sibilants than anything else. (Most people never heard omni speaker accurately positioned in a symmetrically furnished room and attribute the focus smearing to "nature of the omnis". Earl Geddes once dropped in my room at CES with large omnis and didn't like the focus, of course. Neither have I, but he was kinda' deaf to my explanation that because we weren't allowed to move this darn TV cabinet, we had to move both speakers towards right, as well as the listening position, and all symmetry was lost. It still sounded better than having the TV cabinet almost in front of the left speaker. I'll never exhibit anything again at stupid Venetian, BTW).
Dangerous game this is. Many manufacturers when exhibit at shows, place speakers very poorly and furnish the rooms disregarding symmetry. Actually, accurately laid out monopoles will whoop the **** of inaccurately laid out dipoles any day, and you can hear it going on all the time at audio shows.
I know audiophiles spending their entire audiophile "career" listening to poorly laid out rooms and speakers within, spending megabucks on new gear, hoping they'll get lucky, but for some incomprehensive reason to me, fail to listen when you tell them they should play with positioning.
I can't even begin to explain how important the room layout is and how often it's the more decisive factor than the speaker itself.
Hi, twest820!
Right. Cuibono reminded me of it, too, thanks to both.
Even if I was close to the real-life figures, he was referring to ideal dipole, and because of that my discussion is still grossly off target.
As for Clio, if I were you, I wouldn't think twice about it. Maybe it's just me, but I can't use Clio because of it's handling that annoys the hell out of me. I'm a big fan of Praxis, though.
Wow, thank you for the info! 8k5 !!!! Crazy!
That's about 3.3 times it's cut-off frequency!
So, do you have a dip at 8k?
If not because it's EQ'd flat, what does it say off-axis?
Hi Guys,
happy new year to all of you !
Good discussion ! Below is pretty much a cross section of my thoughts about dipole tweeters. Good to see that I am not alone with that
Oliver
happy new year to all of you !
Good discussion ! Below is pretty much a cross section of my thoughts about dipole tweeters. Good to see that I am not alone with that
But doable. And maybe it only takes some guys of us to accomplish that.
Maybe make that even 5KHz. And it is not only the size of dome tweeters but the inherent behavior/change of radiation (with 1" tweeters anyway) in the freq. area when they start beaming.
Oliver
Well the Neo3 eq'ed flat on axis certainly didn't retain that response off axis for me. I don't see how that could happen as the dipole peal and first null mover higher in frequency as the off axis angle increases. The dipole peak occurs at c/(2d) and the first null at c/d; c= sound speed, d= separation. We usually think of that as applying on axis but it actually applies everywhere in the far field. That is what we have the figure 8 pattern. d = D cos(theta). As theta approaches 45 degrees the peak moves up to 1.414 time the on axis peak, 1/2 octave higher so the response in the lower dipole region is -3dB at 45 degrees, at 60 degrees the peak move sup a full octave hence the response is down 6dB.
I agree with the earlier comment that what is important is most important is not to have a perfect dipole tweeter but to match the polar response at the mid/tweeter crossover and then have the polar pattern either remain constant of monotonically narrow. What we don't want is the typical broadening of the polar response above the crossover point which is typical of dipole speakers using dome tweeter.
The problem I have with the RRAL, or any dipole tweeter, is that I do not know what will be required to make it perform in a manor that I will find useful. At around $50 for the Neo3 I can afford to experiment but at close to $800 I think the manufacture should provide me with the "dipole" format that it is optimal. It then becomes a manor of whether that format suits my needs or not.
That is what makes the dipole format so difficult. For a direct radiator we can look at the IEC or infinite baffle response and we know for the most part that we will get something similar with additional diffraction artifacts on a different baffle. But with a dipole the behavior may be so baffle dependent were can not make a judgment before hand.
*If* I strip the psychoacoustic part off, basically all this discussion is a discussion about diffraction and its alignment - no way around it - seeking after smooth transition of "dipole directivity" up in frequency, everybody will end up with kind of a horn / waveguide / diffraction alignment device to do so.
At least if we want some SPL too
Michael
At least if we want some SPL too
Michael
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Very interesting discussion! (up to post #90 at least )
Since most has been said already, I would like to add two thinks only:
My main reason to go dipole is not the figure 8 pattern. It is the easy way to have a constant directivity along the (almost) complete frequency range. The limiting factor at the top is the sheer mechanical size of the construction. But this has been shrinking at an impressive pace in the last years. Still higher SPL will have to be paid with larger size.
I am under the impression that a high percentage of dipole users has the speakers toed-in to a large degree. In many cases this will effectively move the first side wall reflections into the area of the dipole null. This is the other nice aspect of using a dipole.
RAALs comments about room symmetry rang a bell in me. On occasion I have told people something similar: If they had 7.000 Euro to spend on speakers, they should not buy a pair at 3.500 Euro each. They better should pay an interior designer 5.000 Euro to come up with a suitable symmetric room layout, that pleases the wife, and buy speakers at 1.000 Euro each.
Maybe there is more truth in it than I had originally thought. Of course there is still the option to follow Earl for even higher directivity. But his recommendations for getting the room right call for real money too.
Rudolf
)Since most has been said already, I would like to add two thinks only:
My main reason to go dipole is not the figure 8 pattern. It is the easy way to have a constant directivity along the (almost) complete frequency range. The limiting factor at the top is the sheer mechanical size of the construction. But this has been shrinking at an impressive pace in the last years. Still higher SPL will have to be paid with larger size.
I am under the impression that a high percentage of dipole users has the speakers toed-in to a large degree. In many cases this will effectively move the first side wall reflections into the area of the dipole null. This is the other nice aspect of using a dipole.
RAALs comments about room symmetry rang a bell in me. On occasion I have told people something similar: If they had 7.000 Euro to spend on speakers, they should not buy a pair at 3.500 Euro each. They better should pay an interior designer 5.000 Euro to come up with a suitable symmetric room layout, that pleases the wife, and buy speakers at 1.000 Euro each.
Maybe there is more truth in it than I had originally thought. Of course there is still the option to follow Earl for even higher directivity. But his recommendations for getting the room right call for real money too.
Rudolf
Yup.
The non-PDR Neo3 dipole peak is about 3.45kHz so the first "null" is centered near 6.9kHz, not 8. John K also refers to the null as dipole bloom which, IMO, is a more descriptive term for the displacement of radiated energy from on to off axis.
My basic measurements (indoor, ungated, 1/24 smoothed) and EQ are in this thread; figures 5 and 6 of post 1, figure 2 of post 3. The rise in the off axis curves around 7kHz is probably bloom but the SnR on the data isn't good enough I'm convinced I can declare it statistically significant. An outdoor sonogram at 5 or 10 degree steps would be conclusive but the weather here's unlikely to cooperate until, oh, May or so.
Unfortunately ARTA locks up my laptop. Thanks, though.
Hi John,
You're a highly regarded loudspeaker designer and your work is always thorough, it brought so much useful data to wide audience and it was always discovering the good features of affordable components, giving valuable advice to DIY community.
Surely, you must know what would you like to have, regarding dipole tweeters format. You can't just sit back and let me guess what it is. If you're not happy with current offerings, then please define what optimal is. You may be used to manufacturers that don't listen, but I do listen and try to do my best to serve the needs.
Because of that, I have question to ask you, after I point out one thing.
To the difficulties you noted, I would also add the sensitivity issue, which is disregarded here.
Let's not mix apples and oranges, as 90dB/Watt allows a speaker designer a completely different vantage point than 95dB/Watt.
If your choice of amplifier is, say, 25 Watt Firstwatt J2 or any other 15-25 Watt beauty out there, problems start to jump out of the closet. You'd be aware of the potential, but you wouldn't be able to use it with 90 dB/Watt speaker, and that is very frustrating. You'd want at least 95 dB/Watt speaker to match.
For example, closed 140-15 has 95 dB/Watt (not 2.83V), or more, depending on the foam pads positioning. The dipole version, due to increased air loading mass, has about 1.3 dB less with same response curve.
Experience shows that for a good tone balance of the loudspeaker, they both require about 1.5dB more efficient midrange due to dynamic compression issues on the midrange side and due to wider dispersion on the ribbon side.
The problem is that there aren't much mids out there that are churning out 96.5 or 95 dB/Watt flat responses and the ones that do that, are not small filler drivers, but 8" exotics, like Supravox 215 variety, Seas exotic 8, and such. No planars in the game, either.
The mid will start beaming fairly soon and you can't use a filler driver, because there isn't any variety of 4-5" 95 dB's to choose from.
Just 3dB, let alone 5dB in increased sensitivity demand by the customer, changes the game completely and 50 bucks is not considered a chip any more, due to exponential increase in difficulty of designing and building such a thing. 90 dB/ Watt allows much more liberty and it's easy compared to 95dB/Watt.
So, my question is, if you were to design a dipole 95-96 dB/Watt speaker, having in mind that you'll have to use an 8" midrange, crossing is as low as possible, what would be the tweeter format that you'd like to use?
I think I nailed it pretty close, for what it s intended for, but I'd like to know what would you do, if it ain't a secret.
I'm asking because I may want to provide certain features to the baffle so everybody would be happy.
One possible way to do this is to increase the iron yoke size, but drill a large number of 1/2" to 3/4" holes through it. That way, you can choose which holes to plug and which to leave open, creating different patterns that just might fit any dipole taste, without increasing efficiency.
Hello all,
That is the old fashioned engineering point of view but unfortunately it does not make any psychoacoustical sense. What we really need is monotonically widening dispersion somewhere above 3kHz. To minimise the cross talk artefacts of stereo one needs to spatially homogenise the pinna cues and that is most easiest done by providing very wide dispersion at treble, almost omnidirectional above 3kHz.
Also in the midrange below 1kHz one needs to minimise room reflections to be able to provide stereo ITD cues and that is best done with very narrow dispersion.
Clearly it turns out the ideal loudspeaker directivity is not constant, not narrowing but widening!
This radical view was offered for your pleasure by Elias
That is the old fashioned engineering point of view but unfortunately it does not make any psychoacoustical sense. What we really need is monotonically widening dispersion somewhere above 3kHz. To minimise the cross talk artefacts of stereo one needs to spatially homogenise the pinna cues and that is most easiest done by providing very wide dispersion at treble, almost omnidirectional above 3kHz.
Also in the midrange below 1kHz one needs to minimise room reflections to be able to provide stereo ITD cues and that is best done with very narrow dispersion.
Clearly it turns out the ideal loudspeaker directivity is not constant, not narrowing but widening!
This radical view was offered for your pleasure by Elias
Earlier in the thread Rudolf posted this...
Had anyone implemented yet?
That is indeed an amazing response - but I'd be concerned that it isn't the whole story. The arrangement of the two drivers makes it look like it may have different responses at different angles (horizontal looks great, but what about vertical, and in between?). Looks easy enough to try though - I guess it is a testament to our laziness
.Aleksander - if you could make a driver dedicated to dipoles, that could hit near LR4 at 1kHz, and had a smooth polar response, and good sensitivity/power handling, you would have a winner, and it would be worth the cost, because no driver can do that yet. It would change the way high-end dipoles are designed. Is there a large-enough market? I don't know.
for sure
Those amps are not really suitable for OB to say it loud and clear - at least not if you are seeking SPL plus some headroom - and on top of that passive XO possibly.
OB / nude is sheer waste of power to a considerable degree - a luxurious design attempt in any way ...
Use two of these (Scan-Speak 15M/4624G Discovery) - one above the other - and you are almost there..
https://www.madisound.com/store/product_info.php?products_id=8926
IMO pretty sonics for that bargain price too.
Michael
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Hello all,
That is the old fashioned engineering point of view but unfortunately it does not make any psychoacoustical sense. What we really need is monotonically widening dispersion somewhere above 3kHz. To minimise the cross talk artefacts of stereo one needs to spatially homogenise the pinna cues and that is most easiest done by providing very wide dispersion at treble, almost omnidirectional above 3kHz.
Also in the midrange below 1kHz one needs to minimise room reflections to be able to provide stereo ITD cues and that is best done with very narrow dispersion.
Clearly it turns out the ideal loudspeaker directivity is not constant, not narrowing but widening!
This radical view was offered for your pleasure by Elias
Since I share this view to the last point, that's why I can't really figure out what would be the benefit of having equal dispersion everywhere, as both rooms and our psyche doesn't accept it equally.
As I pointed out before, all rooms have problems in bass, and some rooms have problems in presence region (centered about 2k5). As cuibono pointed out he prefers dipole at least up to 4k, which falls in line with mentioned room problem.
I just want to add that I stand behind the room treatment and prefer omni down to 200 Hz in such case. Rooms must be treated, or they will ruin a lot of our efforts. However, once appropriately treated according to their size and volume, the results are nothing short of astonishing and the sound is in a different class altogether. Nothing like it, if you want to hear the actual size and feel of the instruments, and horns can't touch it, with their "in your face" presentation. The way I like to put it, they have a big sound, but not big instruments.
One of the people from the whole of audio industry that I admire the most is Amar Bose. He went through the trouble of designing excellent 5" whizzer-less FR drivers and stuffed 9 of them in a clever box, with one shooting forward.
That speaker, with it's dedicated EQ box, kicks *** big time in recreating the proper size of the orchestra and all that it contains.
For me, a wide baffle, big midrange (even 12"), OB is the next best thing in untreated rooms.
That is indeed an amazing response - but I'd be concerned that it isn't the whole story. The arrangement of the two drivers makes it look like it may have different responses at different angles (horizontal looks great, but what about vertical, and in between?). Looks easy enough to try though - I guess it is a testament to our laziness
Aleksander - if you could make a driver dedicated to dipoles, that could hit near LR4 at 1kHz, and had a smooth polar response, and good sensitivity/power handling, you would have a winner, and it would be worth the cost, because no driver can do that yet. It would change the way high-end dipoles are designed. Is there a large-enough market? I don't know.
I second that about Rudolf's work! The same goes to twest820!
I could, but you should know that a good cone driver does things better up to 1k5-2k than a ribbon ever could dream of. That is why electrostats and big planars sound wimpy with drums, percussion and piano.
In midrange, parachute effect, or large air loading, needs to be controlled with greater force per surface area than any ribbon, stat or planar can give.
Trust me, you're much better off with cones in midrange.
If you want to get truly remarkable results in midrange, use 3" FR driver in clusters of 2x4, 3x3 or 6 pieces in hexa and one in the middle for total of 7. Do not use line sources, they don't add together well, as top driver doesn't know what bottom driver does and vice versa, meaning that they don't share the load and sound equally wimpy just like one feeble 3" driver, only you can cross it a bit lower. Sharing the air loading is the key, a such 3" FR drivers clusters are the way to go. They get so much authority and slam that it;s not even funny. The main advantage to a comparable surface area of just one cone driver, is that 3" FR will have first cone breakup problems even as high as 11k, so you'll end up having a piston of a large area all the way up.
Choose only ones without Farraday rings and such tricks. Look for saturated pole plate and central pole piece. BTW, very few good driver use a Farraday ring as it wastes the signal current on showing you a nice impedance and they need 150 Watts to get dynamics and start sounding lively. Only a few bright examples exist, made by people that understand the drawback of it.