Utility is also a requirement.
Patent attorneys use the word "utility" differently than anyone else I know. To consider it a bar to patentability is technically correct, but not consistent with my experience.
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A physics-defying speaker array(?)
- Thread starter Taylor Livingston
- Start date
Patent attorneys use the word "utility" differently than anyone else I know. To consider it a bar to patentability is technically correct, but not consistent with my experience.
Man, I keep forgetting about this - I must get to the bottom of it!
Did anyone read the patent? Does it say anything meaningful? It seems you guys who know about speaker physics wrote this off, but didn't really explain what you concluded based on the patent. Mr. Bromer has not replied to my email about posting some measurements (I'm sure that will come as no surprise to most of you), but if this thing is hooey I would like to know specifically why.
Did anyone read the patent? Does it say anything meaningful? It seems you guys who know about speaker physics wrote this off, but didn't really explain what you concluded based on the patent. Mr. Bromer has not replied to my email about posting some measurements (I'm sure that will come as no surprise to most of you), but if this thing is hooey I would like to know specifically why.
Well, we never got any deeper into this, and I forgot about it, but the guy emailed me this today:
Check this out:
[Invalid or Expired Link Removed]
A Groove is a Terrible Thing to Waste!
What part of this is physics-defying?
The patent number has been posted: 7409071.
The statement that "originality is the only requirement" for a patent is not correct. There are other equally important requirements. However, the patent office does not evaluate any claims of performance - they look at what it IS (for an apparatus) but do not evaluate whether or not it works well.
The first claimed invention which is the legal boundary that defines the invention is attached as a thumbnail.
When you get through this vocabulary quiz, it does not prove to be "physics-defying" (which would fail at least one of the requirements for a patent) or prove anything else related to the performance specs. Instead, it describes a speaker arrangement similar to the one shown in Fig. 2 of the patent, or similar to the picture at this link.
It appears to me that the operating concept is to simply arrange the speakers, in-phase, such that for a given frequency (i.e. wavelength) the pressure waves generated by each individual speaker will coincide, allegedly granting improved bass performance.
Some similar ideas look like these guys:
Link Removed
US Patent 5266751
If I recall correctly, Fender also made an inwardly angled 4x? cabinet but I cannot dig up any pics at the moment.
The statement that "originality is the only requirement" for a patent is not correct. There are other equally important requirements. However, the patent office does not evaluate any claims of performance - they look at what it IS (for an apparatus) but do not evaluate whether or not it works well.
The first claimed invention which is the legal boundary that defines the invention is attached as a thumbnail.
When you get through this vocabulary quiz, it does not prove to be "physics-defying" (which would fail at least one of the requirements for a patent) or prove anything else related to the performance specs. Instead, it describes a speaker arrangement similar to the one shown in Fig. 2 of the patent, or similar to the picture at this link.
It appears to me that the operating concept is to simply arrange the speakers, in-phase, such that for a given frequency (i.e. wavelength) the pressure waves generated by each individual speaker will coincide, allegedly granting improved bass performance.
Some similar ideas look like these guys:
Link Removed
US Patent 5266751
If I recall correctly, Fender also made an inwardly angled 4x? cabinet but I cannot dig up any pics at the moment.
Attachments
Now that's cool....Mongo want.
I wonder what a rack with stack of 4 mounted with the slots vertical would sound like? Hmmm, I also wonder if would it make a difference if it was stacked with the wedges in full contact so the slots formed an arc?
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
That's pretty much what it is. Where the individual drivers are within 1/4 wavelength of each other they couple, where they're further apart the cross-firing scheme minimizes destructive interference and increases dispersion. But from a practical standpoint a vertical array of midrange drivers will give better midrange and high frequency performance, while a well engineered subwoofer will give better bass. The Bose L1 system is the most well known example of this type of system in a small format, unfortunately it's not a well executed design. This is, though the price is just a wee bit out there:
[Invalid or Expired Link Removed]
I haven't looked at the patent, but judging from the picture with the semi-circle of small drivers, it's clear how it's intended to work:
When a direct radiator is small compared to the wavelength, the real part (where the acoustical power is developed) of the radiation impedance is proportional to the frequency squared (f^2). Further on the motional impedance in this frequency range is dominated by the moving mass of the radiator (the speaker is "mass controlled"), and hence the velocity is inversely proportional to the frequency (1/f). The useful acoustical power is then given by
P ~ R * v^2 ~ f^2 * (1/f)^2 = 1
i.e. independent of the frequency. This is the reason the frequency response of any direct radiating system (closed box, bass reflex, etc) is (can be) flat throughout the lowest octaves. The drawback is that the velocity, and hence excursion, gets large for the lowest frequencies, and the efficiency is very low (1 % ballpark). Stated differently, this is a case of severe impedance mismatch. In typical implementations we pay a price w.r.t. power, hundreds of W for concert SPLs are converted to heat, not sound, and we often run into mechanical problems (a.k.a. speaker "farting").
When the radiator is large compared to the wavelength, the real part of the radiation impedance is instead constant, and the magnitude is larger, offering a better impedance matching. However, the system is still mass controlled (still assuming direct radiators; horns can be designed to be resistance controlled for parts of the passband), and the output becomes
P ~ R * v^2 ~ 1 * (1/f)^2 = 1/f^2
corresponding to a 6 dB/octave roll-off (10*log10(1/2^2)= -6). The funny part is (too elaborate to show here) that the directivity index increases by 6 dB/octave, so the output on-axis gets flat for a few more octaves, whereas it drops off off-axis. This phenomenon is the reason smaller drivers are (should be!) used for midrange and treble. The boundary between "acoustically small" and "acoustically large" is, for a circular piston in a baffle, at kr = 1.4, where k = 2*pi/lambda, and r = radius. (For a pulsating sphere the boundary is at kr = 1.)
After this quick introduction to electro-acoustics fundamentals, it's clear that the design is intended to approximate a large radiator (hence his talk about a certain speaker size required for a certain cutoff; that's true if we want to operate in "large radiator mode"), by a number of smaller drivers, that due to "mutual coupling" -- the individual ones will "feel" the presence of the others (radiated sound yields a force on the diaphragms which alters the individual effective radiation impedance) -- for the lowest frequencies acting as one large diaphragm. By this "trick" one can shift the kr = 1.4 point towards lower frequencies (effective r gets large). This effect is seen when stacking multiple subs, and is the reason horn subs are practical at all (otherwise they'd be too big to move): Many smaller horns are combined (together with "virtual ones" -- the mirror sources from floor and nearby walls if present) into one big horn, reaching lower in frequency.
One twist of the proposed design is that the approximation is sparse, i.e. it's not a large surface packed with drivers. This is good, since (as should be clear by now) a real big driver will be very "pointy" (directivity rise by 6 dB/oct).
Summary:
The design (speaking of the "ring" now, not the wave guide thing mentioned later on) could actually work in theory. It remains to be seen how well the approximation works in practice in the LF range, whether the HF dispersion from this array does the trick, and if so, whether this approach has real advantages over other designs such as the one mentioned by BFM.
HTH
Fredrik
Addendum:
It boils down to whether there's any "magic" in the claimed symmetry stuff: If that's not the case, we're just looking at mutual coupling of a bunch of small drivers, whereby the radiating surface is still low. We'll still see LF gain, yes, but the thing will not work as the large speaker claimed. The absence of measured data, is a hint (albeit not proof) there's a problem...
When a direct radiator is small compared to the wavelength, the real part (where the acoustical power is developed) of the radiation impedance is proportional to the frequency squared (f^2). Further on the motional impedance in this frequency range is dominated by the moving mass of the radiator (the speaker is "mass controlled"), and hence the velocity is inversely proportional to the frequency (1/f). The useful acoustical power is then given by
P ~ R * v^2 ~ f^2 * (1/f)^2 = 1
i.e. independent of the frequency. This is the reason the frequency response of any direct radiating system (closed box, bass reflex, etc) is (can be) flat throughout the lowest octaves. The drawback is that the velocity, and hence excursion, gets large for the lowest frequencies, and the efficiency is very low (1 % ballpark). Stated differently, this is a case of severe impedance mismatch. In typical implementations we pay a price w.r.t. power, hundreds of W for concert SPLs are converted to heat, not sound, and we often run into mechanical problems (a.k.a. speaker "farting").
When the radiator is large compared to the wavelength, the real part of the radiation impedance is instead constant, and the magnitude is larger, offering a better impedance matching. However, the system is still mass controlled (still assuming direct radiators; horns can be designed to be resistance controlled for parts of the passband), and the output becomes
P ~ R * v^2 ~ 1 * (1/f)^2 = 1/f^2
corresponding to a 6 dB/octave roll-off (10*log10(1/2^2)= -6). The funny part is (too elaborate to show here) that the directivity index increases by 6 dB/octave, so the output on-axis gets flat for a few more octaves, whereas it drops off off-axis. This phenomenon is the reason smaller drivers are (should be!) used for midrange and treble. The boundary between "acoustically small" and "acoustically large" is, for a circular piston in a baffle, at kr = 1.4, where k = 2*pi/lambda, and r = radius. (For a pulsating sphere the boundary is at kr = 1.)
After this quick introduction to electro-acoustics fundamentals, it's clear that the design is intended to approximate a large radiator (hence his talk about a certain speaker size required for a certain cutoff; that's true if we want to operate in "large radiator mode"), by a number of smaller drivers, that due to "mutual coupling" -- the individual ones will "feel" the presence of the others (radiated sound yields a force on the diaphragms which alters the individual effective radiation impedance) -- for the lowest frequencies acting as one large diaphragm. By this "trick" one can shift the kr = 1.4 point towards lower frequencies (effective r gets large). This effect is seen when stacking multiple subs, and is the reason horn subs are practical at all (otherwise they'd be too big to move): Many smaller horns are combined (together with "virtual ones" -- the mirror sources from floor and nearby walls if present) into one big horn, reaching lower in frequency.
One twist of the proposed design is that the approximation is sparse, i.e. it's not a large surface packed with drivers. This is good, since (as should be clear by now) a real big driver will be very "pointy" (directivity rise by 6 dB/oct).
Summary:
The design (speaking of the "ring" now, not the wave guide thing mentioned later on) could actually work in theory. It remains to be seen how well the approximation works in practice in the LF range, whether the HF dispersion from this array does the trick, and if so, whether this approach has real advantages over other designs such as the one mentioned by BFM.
HTH
Fredrik
Addendum:
It boils down to whether there's any "magic" in the claimed symmetry stuff: If that's not the case, we're just looking at mutual coupling of a bunch of small drivers, whereby the radiating surface is still low. We'll still see LF gain, yes, but the thing will not work as the large speaker claimed. The absence of measured data, is a hint (albeit not proof) there's a problem...
It boils down to whether there's any "magic" in the claimed symmetry stuff: If that's not the case, we're just looking at mutual coupling of a bunch of small drivers, whereby the radiating surface is still low. We'll still see LF gain, yes, but the thing will not work as the large speaker claimed. The absence of measured data, is a hint (albeit not proof) there's a problem...
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
There's no question that the drivers will couple and provide LF gain, but no more so than any grouping of LF drivers. It's the frequency to which they'll couple that's the problem, and by the looks of that rig I'd say no higher than 200 Hz, above which combing will be inevitable. Polar charts would be necessary to see if it's of any value.
As for the youtube vid, he makes it seem like magic when the woofer goes lower when attached to his enclosure than it does in free air. No woofers have any bass in free air.
It just takes some simple measurements to prove this or the new thing is any more efficient or "better" than other existing technology. Simple measurements anybody can do with a PC. AES style. And/or some double blind study. But the bass MI industry is barren of measurements and fruitful of hype.
Where's Bose when you need 'em?
Where's Bose when you need 'em?
There's no question that the drivers will couple and provide LF gain, but no more so than any grouping of LF drivers.
/.../
As for the youtube vid, he makes it seem like magic when the woofer goes lower when attached to his enclosure than it does in free air. No woofers have any bass in free air.
Right, that's where I have my doubts, too! If it really would be that simple, why build many bass horns? Just place one on each side of the stage
Also, since Harry F. Olson didn't build this in the 30:s it's not likely to be of any real benefit
I'd say that this goes for large parts of the Hi-Fi industry, too. Lots of companies and magazines make their living of placebo-syndrome and/or distortion...
Is that "tube" P ~ R * v^2 ~ 1 * (1/f)^2 = 1/f^2 ... or "solid state" P ~ R * v^2 ~ 1 * (1/f)^2 = 1/f^2 ?
I have quite a few specific responses to you, Mr. Nick Bromer, but would like to preface them as follows:
Whenever there is a new development in the acoustic world that could potentially improve our experiences as bass players, naturally you have a captive audience. However, you must understand that there are some very well qualified engineers, musicians, scientists, designers, and sound professionals here. As such, there is a much higher expectation that the proprietor of such a development can back up his/her claims.
I am skeptical as a practicing mechanical engineer with experience in acoustics. I'm also skeptical as a musician, since we've had some fairly wild claims made on these forums in the past. Nevertheless, I make the following inquiries and comments with respect and interest, not malice.
You have a patent pending on your concept. Did you mean to entitle it "Large-Diameter Accurate Speaker"? Just interested in clarity here.
As an alleged patent attorney, you should know that too broad a patent will be open to interpretation and slight modifications to get past infringement. You should also know that you require novelty and utility. The acoustics and physical theory have to back your claims up! So far, you have described the general effect of arrayed drivers. This type of coupling, as billfitzmaurice described, can enhance low frequency extension for correctly spaced, sized, and tuned drivers.
You state that the configuration makes the speakers "bigger", but does not change the SPL or power handling of the cabinet. This is a vague statement. If you are using "bigger" to imply low frequency extension, you MUST be changing the SPL (sound pressure level - let's be clear) at those low frequencies. Otherwise, there will be no audible or measurable improvement. However, I agree that the power handling of your cabinet won't change based on the physical position of the speakers. That depends on the thermal limits of the driver, and the mechanical limits of the driver/enclosure system.
The "bass cutoff" - let's call it frequency response - of a speaker enclosure is controlled by many factors. It is futile to simplify this argument down to a speaker diameter argument. For an extremely oversimplified counter-argument, put in a set of in-ear monitors. These use dynamic or balanced-armature drivers of miniscule size. Yet, in their application, can achieve impressive frequency response. Why not array thousands of these?
The website you cite as a demonstration of bass response cannot possibly convey the desired information. The recorded sound is subject to the entire signal chain between the listener's ears and your speaker enclosure during the recording. You will impress us much more with actual numbers obtained during actual tests. You did do tests and measurements before you spent the money on your patent, right?
Here you state that your circular arrays are not subject to comb filtering. You need to do some research before you make this statement. Comb filtering is applicable to any array of drivers, irrespective of the symmetry of the layout. While the interference pattern will be different for your circular array when compared to a grid-style array, it does not disappear. There are many tools you can use to mathematically model this. Again, if you wish to make the statement you just made, please present evidence such as measurements or analysis.
In another post you stated the following:
You could expect to get better high-frequency extension from smaller drivers as a rule-of-thumb. However, breakup or any other effects are highly dependent on the driver design! Also, you really aren't instilling confidence by saying you "think" the sound is "probably" cleaner, but your "ear is not very good." Have you not tested with any measurement equipment? There is really no objective way to tests these aspects of your design without good computational modeling validated by accurate measurements. Of course it has to sound good subjectively, but we're talking about a scientific concept in Patent Pending mode here. You have to be able to back up your claims, and so far you haven't.
Whenever there is a new development in the acoustic world that could potentially improve our experiences as bass players, naturally you have a captive audience. However, you must understand that there are some very well qualified engineers, musicians, scientists, designers, and sound professionals here. As such, there is a much higher expectation that the proprietor of such a development can back up his/her claims.
I am skeptical as a practicing mechanical engineer with experience in acoustics. I'm also skeptical as a musician, since we've had some fairly wild claims made on these forums in the past. Nevertheless, I make the following inquiries and comments with respect and interest, not malice.
You have a patent pending on your concept. Did you mean to entitle it "Large-Diameter Accurate Speaker"? Just interested in clarity here.
As an alleged patent attorney, you should know that too broad a patent will be open to interpretation and slight modifications to get past infringement. You should also know that you require novelty and utility. The acoustics and physical theory have to back your claims up! So far, you have described the general effect of arrayed drivers. This type of coupling, as billfitzmaurice described, can enhance low frequency extension for correctly spaced, sized, and tuned drivers.
You state that the configuration makes the speakers "bigger", but does not change the SPL or power handling of the cabinet. This is a vague statement. If you are using "bigger" to imply low frequency extension, you MUST be changing the SPL (sound pressure level - let's be clear) at those low frequencies. Otherwise, there will be no audible or measurable improvement. However, I agree that the power handling of your cabinet won't change based on the physical position of the speakers. That depends on the thermal limits of the driver, and the mechanical limits of the driver/enclosure system.
The "bass cutoff" - let's call it frequency response - of a speaker enclosure is controlled by many factors. It is futile to simplify this argument down to a speaker diameter argument. For an extremely oversimplified counter-argument, put in a set of in-ear monitors. These use dynamic or balanced-armature drivers of miniscule size. Yet, in their application, can achieve impressive frequency response. Why not array thousands of these?
The website you cite as a demonstration of bass response cannot possibly convey the desired information. The recorded sound is subject to the entire signal chain between the listener's ears and your speaker enclosure during the recording. You will impress us much more with actual numbers obtained during actual tests. You did do tests and measurements before you spent the money on your patent, right?
Here you state that your circular arrays are not subject to comb filtering. You need to do some research before you make this statement. Comb filtering is applicable to any array of drivers, irrespective of the symmetry of the layout. While the interference pattern will be different for your circular array when compared to a grid-style array, it does not disappear. There are many tools you can use to mathematically model this. Again, if you wish to make the statement you just made, please present evidence such as measurements or analysis.
In another post you stated the following:
You could expect to get better high-frequency extension from smaller drivers as a rule-of-thumb. However, breakup or any other effects are highly dependent on the driver design! Also, you really aren't instilling confidence by saying you "think" the sound is "probably" cleaner, but your "ear is not very good." Have you not tested with any measurement equipment? There is really no objective way to tests these aspects of your design without good computational modeling validated by accurate measurements. Of course it has to sound good subjectively, but we're talking about a scientific concept in Patent Pending mode here. You have to be able to back up your claims, and so far you haven't.
Incorrect statement.
Nick can do whatever he wants.
Most speaker cabinets sold in the US have no published data that is traceable to any standard, and, many that provide data are horribly inaccurate.
I haven't watched the videos and don't care if the thing works as advertised or not.
Props for trying to do something original and by actually coming up with an idea, building a prototype, and getting a patent; it's not an easy or inexpensive thing to do.
Also props to you other guys who design and build stuff regardless of patents.
I agree with you; Nick and anyone else can do whatever they want. That is true of the existing market, and to most people that's just fine. That's no reason to continue in such a way though! The context of my statement, which is missing in the quotation you used, is of technical claims and discussion with the engineers/technical people on this forum. It was also in the context of a patentable concept, where proof of novelty (it hasn't been done before, like other arrays) and utility (it does what he claims) will determine if it ever gets beyond the "pending" stage. Measurements, modeling, and testing go far in demonstrating the utility of the concept. This is different from the basic utility of a speaker enclosure that produces sound in response to an applied electrical potential!
I have a lot of respect for anybody who wants to design and build something new for commercial gain or personal satisfaction. The ones I choose to support aren't usually those with headline-grabbing claims. They are usually the ones whose products demonstrate quality - the kind that can only be had by being an expert in the field. So far, I can't see anything that makes me trust that Bromer Sound are experts in acoustics. I am open to changing my mind if this is demonstrated.
In other words: If they make excellent quality enclosures using arrayed drivers with a distinctive visual layout, the product has merit if it is good! If the manufacturer makes claims such as these with allusions to advanced acoustic phenomena, then I expect that the physics can be demonstrated and discussed at a sufficiently detailed level for this forum. After all, that is required for a patent. As the patent is now pending, disclosure is permitted.
Otherwise, just stand on the merits you do have, such as great sounding (subjective), well-manufactured speaker cabinets.
