Not nice of you kids to ridicule us old guys (kidding........... of course).
I went to the NAO website to check out those "very elegant engineering solutions" that shove my face into the mud for not knowing "todays SOTA.😉"
Hey. I found something about "U frames." Now I never heard of that over here in the nursing home (kidding). But, you know, it does sound AWFULLY similar to what I fooled with by removing the backs on Bozak cabinets in the spring of 1968. Perhaps you could explain the theoretical advancement reflected by the "very elegant engineering solutions" of the NAO U-frame over what I (and others) did?
Perhaps you could outline a couple of those other "very elegant engineering solutions". Please don't bother mentioning any not already discussed in Olson, Beranek, or otherwise dating back to those old days.
BTW, I am puzzled why you think a speaker made up from of a couple of Rice-Kellogg (1924?) cones and a really teenee ribbon (???) is "Technology wise it is way ahead of what you have got at home" which happens to be a full-range ESL sealed in SH6 gas, 39 lb matching transformers (yes, each one), and 12 kv bias. I gotta hear your explanation.
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My experience seems to mirror Rudolf's.
The speaker I'm using in my bedroom graphs like this:
on axis:
Graph at my listening position with various levels of absorption:
As far as reverb/decay:
Start:
after treating with absorption:
The only thing I'm not quite sure I'd agree w/ Dave S. and research on is the perceived tonal balance effects of the axial response and reverberation in the high end. The treble before and after absorption treatment is measurably reduced as far as decay is concerned. More importantly less audibly troublesome. However the FR high up is not so different. In fact, that uniform spectrogram/RT60 from 80Hz(ish) up was something I was shooting for in my treatment plan. It may have more to to with what Dr. Toole says about speaker troubles being more obvious in a reverberant room than any thing else. I'd trust real research over my opinion any day of the week if my understanding of what Dave is saying is correct. I'm not too concerned with decay aspect of the low bass. It seems the plain old FR seems most audible and hardly so there to me. More a tactile thing. That bump I have at 45Hz isn't too bad subjectively.😉 The 100-200Hz issues do seem audible and the flatter they've become, the better the sound. Those are definitely room/placement issues.
Dan
The speaker I'm using in my bedroom graphs like this:
on axis:
Graph at my listening position with various levels of absorption:
As far as reverb/decay:
Start:
after treating with absorption:
The only thing I'm not quite sure I'd agree w/ Dave S. and research on is the perceived tonal balance effects of the axial response and reverberation in the high end. The treble before and after absorption treatment is measurably reduced as far as decay is concerned. More importantly less audibly troublesome. However the FR high up is not so different. In fact, that uniform spectrogram/RT60 from 80Hz(ish) up was something I was shooting for in my treatment plan. It may have more to to with what Dr. Toole says about speaker troubles being more obvious in a reverberant room than any thing else. I'd trust real research over my opinion any day of the week if my understanding of what Dave is saying is correct. I'm not too concerned with decay aspect of the low bass. It seems the plain old FR seems most audible and hardly so there to me. More a tactile thing. That bump I have at 45Hz isn't too bad subjectively.😉 The 100-200Hz issues do seem audible and the flatter they've become, the better the sound. Those are definitely room/placement issues.
Dan
Add Briggs & Hartley to that list. Hartley did some of the more advanced work on what we now call a U
dave
I think he was talking about the 4th graph here:
NaO Note Details
Hover your cursor above it to see the difference between Nao Note and typical dipole implementation (like the old nao, Orion, mine 🙂 etc)...
The oldest "How to build loudspeakers" book, that I bought and still posess, is from 1978. Ten years before that I put the first driver into a self-built box. So you have all rights to call me a kid (just kidding too 😛).
I don't like the fine irony that is hovering above much of what you write. Or better said: I would love to answer as sophistic as you write, but all english speaking people I have met in those years where too polite to give me an english training in this style of "conversation". I bitterly regret that I am too much of a dumbhead to answer in an equivalent manner. 🙁
I'd appreciate if you could steer me to any precise and predictable specification of U-frame behaviour WRT loudspeakers before the times of JK, SL or JP. And please don't tell me that this is known from any old organ. Technical science doesn't begin when you first stumble over a peculiar effect, but when you can explain it thoroughly in mathematical terms.
Obviously he has found a way to build a dipole that is not pestered by heavy lobing in the kHz region.
That "teenee" planar belongs - together with some tiny neodymium AMTs - to the first generation of tweeters which allow to expand true dipole behaviour into the tweeter region. It will not have escaped your attention that almost all ESL- and conventional tweeters don't work as true dipoles above 2 kHz - which actually means that they don't work as true dipoles at all. If I am counting right, the Nao Note covers 6-7 octaves (100 Hz - 10kHz) as a true dipole, yours probably no more than 3 (150-1200 Hz?)?
Rudolf
I think we have put the "very elegant solutions" and "technology wise... way ahead" to rest. Readers can judge for themselves the novel "solutions" Rudolf has identified, if any.
The fellow who designed the NAO seems to be very skilled with PhotoShop - those polar responses are, how shall I say it politely, very heavily "averaged".
Of all the "scientific breakthroughs" and mathematically sophisticated advances in acoustics over the years, I can think of nothing more profoundly trivial than an "analysis" of taking a flat baffle and doing minor tricks to the geometry, also known as making a "U-frame" or H-frame or.....
Are there people who think it is certain that music should come from both sides of a cardboard cone, whatever the cone designer may have thought and whatever millions of others believe? It would be rude of me to make a double-meaning joke about "backside sound."
Rudolf certainly emphasizes the exceptional accomplishment of the designer of the teenee ribbon tweeter who, despite monumental pressure otherwise, was able to keep from covering over the backside of the driver and therefore inventing the symmetric dipole ribbon. I thought all ribbons were kind of symmetric? And that making music from the front side only violates some important principle.
Seems revealing when Rudolf uses the term "true dipole." Kind of sounds like "true believer" or "speaker cables."
I rather like OBs. Don't laugh, I just made a giant OB subwoofer and like the way it works with my Hall-of-Fame corner woofer (Klipschorn) playing the same mixed bass signal (below 110 Hz). OB is a good concept. But if I wanted to augment frontside sound with something coming around from behind after bouncing off walls and curtains, the backside sound would have to be very different from the front to properly augment it... once it got around to the front.
Great curves from Dantheman, who I greatly respect. If microphones could speak, I am sure they would reveal their complete satisfaction. How's the sound?
The fellow who designed the NAO seems to be very skilled with PhotoShop - those polar responses are, how shall I say it politely, very heavily "averaged".
Of all the "scientific breakthroughs" and mathematically sophisticated advances in acoustics over the years, I can think of nothing more profoundly trivial than an "analysis" of taking a flat baffle and doing minor tricks to the geometry, also known as making a "U-frame" or H-frame or.....
Are there people who think it is certain that music should come from both sides of a cardboard cone, whatever the cone designer may have thought and whatever millions of others believe? It would be rude of me to make a double-meaning joke about "backside sound."
Rudolf certainly emphasizes the exceptional accomplishment of the designer of the teenee ribbon tweeter who, despite monumental pressure otherwise, was able to keep from covering over the backside of the driver and therefore inventing the symmetric dipole ribbon. I thought all ribbons were kind of symmetric? And that making music from the front side only violates some important principle.
Seems revealing when Rudolf uses the term "true dipole." Kind of sounds like "true believer" or "speaker cables."
I rather like OBs. Don't laugh, I just made a giant OB subwoofer and like the way it works with my Hall-of-Fame corner woofer (Klipschorn) playing the same mixed bass signal (below 110 Hz). OB is a good concept. But if I wanted to augment frontside sound with something coming around from behind after bouncing off walls and curtains, the backside sound would have to be very different from the front to properly augment it... once it got around to the front.
Great curves from Dantheman, who I greatly respect. If microphones could speak, I am sure they would reveal their complete satisfaction. How's the sound?
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Back to the subject gentlemen. Stay away from the personal jibes. This warning is free, others will not be.
Thanks Ben! There are still some big problems in the sound that I will resolve though generally the tonal balance is close to correct and the RT60 of 300ms seems to be my sweet zone for intelligibility and retaining ambiance. The mid bass is weak/unbalanced at times and the treble is still a bit harsh d/t the remaining diffraction I suspect. I think if I get more absorption behind and to the outside of the speakers, that will go away. That's what I did before with them and it worked well. Not having a TV between the speakers is just a relief in many ways. Actually I'm going to move the Mackie monitors back here to the BR. Should be nirvana. Then the B2031P can go back to the living room where one will be a 😱 center channel.
The master BR is the quietest room in the house, so I'll build my practice/performance/recording space there. I'm moving the bedroom for sleeping to another bedroom. Hopefully I'll get that done tomorrow, but I doubt it.
The difference in imaging before and after treatment is remarkable. Best I've heard much to my surprise and should be even better with the Mackie. Still I want to through some diffusion in there on the curved back wall and general back half of the room:
Any treatment suggestions appreciated.
Much work to do yet, but this experiment was a big eye opener. Now I know where I did some things wrong with the HT. That will be the next project.
Dan
The master BR is the quietest room in the house, so I'll build my practice/performance/recording space there. I'm moving the bedroom for sleeping to another bedroom. Hopefully I'll get that done tomorrow, but I doubt it.
The difference in imaging before and after treatment is remarkable. Best I've heard much to my surprise and should be even better with the Mackie. Still I want to through some diffusion in there on the curved back wall and general back half of the room:
Any treatment suggestions appreciated.
Much work to do yet, but this experiment was a big eye opener. Now I know where I did some things wrong with the HT. That will be the next project.
Dan
Dantheman - thanks for analysis.
First thought: check out your big closet!!!
My music room has a large sliding-door closet filled (for another few weeks) with my mushy winter clothing, motorcycle gear, and a ton of bedding stuff. Big effect on some room modes and no effect on others if open or closed.
As far as I'm concerned, dead rooms is good. Endless theological debates about directivity and "flat" would end if we all had fairly dead rooms, spouse permitting.
Then we could get back to the tough question of equal-loudness flatness.
First thought: check out your big closet!!!
My music room has a large sliding-door closet filled (for another few weeks) with my mushy winter clothing, motorcycle gear, and a ton of bedding stuff. Big effect on some room modes and no effect on others if open or closed.
As far as I'm concerned, dead rooms is good. Endless theological debates about directivity and "flat" would end if we all had fairly dead rooms, spouse permitting.
Then we could get back to the tough question of equal-loudness flatness.
Not in the horizonzal plane anyway ;-)
Rudolf, this behavior does not come for free. It costs a deep (around 10dB) sag in the back response around 5KHz and the vertical response is 5dB down if John measures ONLY +5 and -6.75 degrees. But the definition of the term "listening window" goes a little beyond those single digit degrees.
John says "The response is well controlled and never exceed the on axis response."
Well, the range between 2KHz and 3KHz looks different to me.
I am not saying the Note is a bad speaker. I can't since I did not even audition it. But it is certainly not a new way of building dipoles today. It is just another unavoidable compromise with more emphasis on horizontal behavior. But horizontal behavior makes only 50% of the sound power curve, which everybody apparantly agrees, should be flat (unlike the topic of this thread). The rest comes from the vertical behavior.
Oliver
FWIW, the polar plots and the polar surface maps of the NaO II and NaO Note are composed of measurements taken at every 5 degrees using a MSL impulse response and 1/6 octave smoothing. The response at each angle is normalized by the on axis response. There is no "photo shopping applied".
Re the U-frame. You may read a general discussion of the concept here which includes references to earlier works. You may read about the specific application tot he NaO II woofer system here.
With 1/6 octave smoothing, who needs PhotoShop? "Angle" smoothing too?
In the links to U-frame theory, is there anything that merits a patent (which is a pretty easy criterion most of the time)? Anything that wouldn't be intuitively self-evident (even if not mathematically precisely defined) say, 60 years ago?
In the links to U-frame theory, is there anything that merits a patent (which is a pretty easy criterion most of the time)? Anything that wouldn't be intuitively self-evident (even if not mathematically precisely defined) say, 60 years ago?
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You might consider taking out your measurement system and looking at the effect of 1/6 octave smoothing on the frequency response obtained from a reflection free impulse.
There is no angular smoothing. Polar plots are just connect the dots with straight lines. Surface plots are just a "waterfall" of the response measured at each angle.
Arguing about what is or is not suitable for a patent is meaningless.
The design of the note was not intended to be "innovative". It is simply an exercise of setting specific design objectives and then going about attempting to achieve them. As with any design there are trade offs. As with any design the degree to which those objective are met is ultimately irrelevant. The final analysis is how the system sounds. If the performance is as desired then perhaps some emphasis can be placed of the importance of the original objectives.
I (guess that i) understand that "kind of logic" and
i feel very close to it. The interesting point is laying
all the tools and theory aside when finally listening.
A good result sonically - and little else - is supporting
the initial design objectives, given those can be
shown to be met by the final product to some extent
at least.
In this process we can refine our objectives and the
weight of different objectives in relation to each other.
Without refinement of objectives and their
(assumed and proposed, only sometimes well
understood) interrelations there is no advance.
There is also a distincion in what we want to
achieve and how we want to achieve it.
The decisions each designer makes are - if conciously
made - due to his own estimation of importance and
interrelations of certain objectives.
Talking about objectives is more interesting often than
talking about speakers or certain techniques.
And i highly regard, that John is a designer, who can
tie both things - objectives and technique - together and
explain it to others in simple words, in a small formula or
a picture without "illegal" simplification.
Best Regards
Oliver,
I can`t see where I said that. I was simply talking of "some very elegant engineering solutions" that where technology-wise well ahead of Bentoronto's Dayton-Wright ESL.
But I do believe that a dipole driver with a dipole length suited better to the upper limit of its frequency range is an advantage without a downside.
Isn't it in the nature of stereo that horizontal behaviour has to come first and vertical second? I see how this can compromise the power response. I would need to see the combined vertical/horizontal response of the Note and the Orion (just as examples) to decide, whether the compromise has gone too far.
Rudolf
I think it is important to recognize that there is a difference between what happens in the horizontal and vertical directions with a vertical alignment of drivers. There are two issues, the variation of the directional characteristics of the sources and the effect of the crossover on radiated power. In the horizontal plane we are dealing primarily with variation in power as a result of the directional characteristics of the sources. If there is a transition between drivers with different directivity at the crossover there will be a power mismatch owing to that difference. I think that is well understood.
In the vertical direction we still have the source directionality issue but we also have the crossover. This is where I think errors are made. It can not be arbitrarily assumed that because the drivers are non-coincident the vertical lobing resulting from the crossover means an uneven contribution to the radiated power if the sources have the same directionality. It is dependent on the crossover type. For example, a LR type crossover may generate a dip in the power response where as the same sources crossed at the same frequency, with the same separation but with an odd order Butterworth crossover will not. The magnitude of the crossover related dip in the power response is a function of separation for the LR type and can vary from no dip to -3dB. For Butterworth types the power response through the crossover region is flat regardless of separation. Both types will exhibit lobing which will be dependent of the separation.
In the vertical direction we still have the source directionality issue but we also have the crossover. This is where I think errors are made. It can not be arbitrarily assumed that because the drivers are non-coincident the vertical lobing resulting from the crossover means an uneven contribution to the radiated power if the sources have the same directionality. It is dependent on the crossover type. For example, a LR type crossover may generate a dip in the power response where as the same sources crossed at the same frequency, with the same separation but with an odd order Butterworth crossover will not. The magnitude of the crossover related dip in the power response is a function of separation for the LR type and can vary from no dip to -3dB. For Butterworth types the power response through the crossover region is flat regardless of separation. Both types will exhibit lobing which will be dependent of the separation.
Hello John,
A while ago you wrote the following in a very interesting post:
The longer you listen however, the more natural this CD sounds. I am now quite convinced (2 months of listening) this is the way to go.
I would really like to hear your nao note, because it also maintains directivity in the bass mid region, something my system does not, and it keeps me wondering how much more improvement this will bring…
I have been fantasizing if it would be possible to cut large rectangular openings in the side panels of my speakers near the woofers, while leaving the rest of the enclosure intact (filled completely with damping material) As the enclosure are quite deep, my hope would be the back wave is sufficiently damped not to create problems and that the openings would create the acoustic shortcut at the lower frequencies, needed to control the directivity, in the region where the 12” speaker does not bundle on its own…
Could this ever work? What would be the best shape and size for the openings?
A while ago you wrote the following in a very interesting post:
This is exactly what I am experiencing currently (12" Geddes Waveguide, TD12M bass-mid in closed box, and an H-frame sub), and I believe this was also Dr. Geddes problem was while demonstrating his speakers at a show: the initial impression always was that some treble wad missing, especially if you came from a room with a speaker with the typical monopole dome tweeter...
The longer you listen however, the more natural this CD sounds. I am now quite convinced (2 months of listening) this is the way to go.
I would really like to hear your nao note, because it also maintains directivity in the bass mid region, something my system does not, and it keeps me wondering how much more improvement this will bring…
I have been fantasizing if it would be possible to cut large rectangular openings in the side panels of my speakers near the woofers, while leaving the rest of the enclosure intact (filled completely with damping material) As the enclosure are quite deep, my hope would be the back wave is sufficiently damped not to create problems and that the openings would create the acoustic shortcut at the lower frequencies, needed to control the directivity, in the region where the 12” speaker does not bundle on its own…
Could this ever work? What would be the best shape and size for the openings?
Attachments
Thanks Ben. That's what I was thinking; there's a giant bass trap hiding behind sliding doors.... underutilized at present! I just talked about this with a friend earlier in the week and he thought it wasn't such a hot idea. I'm actually looking at buying some giant laundry bags and filling them fiberglass or maybe pillow stuffing. Any suggestions welcome on stuffing and bag material. I'll need some of that space for storage, but the rest will be a trap.
I'm not about dead rooms as in anechoic, but definitely more dead than the rt60 of 500-600ms SL suggests. I'd think that would be over the limit of maximum intelligibility unless the recording was done direct in or in an anechoic environment. I'm finding that 300ms a sweet zone in my HT and again in the BR.
HA HA! The old equal loudness contour. Has there ever been a study on people's preference? I'd bet it would go to the more bass every time in a well set up system.
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