Influential Horn Design Patents (for me, at least)...

[D-MAN]

In addition to PWK's patents and published articles, I have found that some of the aspects of the following patents to be of value when solving some horn design problems, although a patent is not exactly expected to be 100% scientifically accurate. However, PWK's "Little Bastard" (1976) patent is an excellent reference for horn design. If you need a single "how-to" horn-reference, THAT'S the one as far as I'm concerned.

Here they are along with an excerpt of my latest (second) design which I have submitted for a patent. You may easily spot the influences... I was intending to come up with a matching rear-channel set to go with my corner-horn mains.

The La Scala and its "djk mods" derived from this forum forms the basis for the design, although the actual performance is expectedly different due to certain aspects of the design which are "new"; the footprint is approx 1/3 smaller, the horn pathway is slightly longer, and uses Huygen reflectors for better mid-and-upper bass response. The throat arrangement is very much the same as my corner horns which were posted here awhile back. The bass bin is roughly the same as the Cornwall in size give and take about an inch here and there.

DM

[D-MAN]

This is the Tattersall (Altec A7-like) bass horn, which uses a "compression area" in the horn throat for increasing and controlling midrange freqeuncy dispersion characteristics. It also looks like an easier-to-build replacement for the VOT-style stressed panel horn, IMO.

In general, this is the first reference that I can find using compressed throat in a bass horn - that technique is used in alot of modern midrange and tweeter horns, but not bass horns.

DM

[Marvel]

And I want to get some built before summer is over.

Did you have attachments here?

[D-MAN]

I'm still posting- hang on, Bruce!

This next patent is the Hook wall-mounted folded horn which uses a ported throat in addition to a front-loaded driver. Intended for against-the-wall-placement (not a corner), it uses a 47 Hz fc for the horn.

DM

[D-MAN]

Of course, the original La Scala from 1965. This sets the standard in small size (24x24" square). The "Lil Bastard" is even smaller (18x18" square), but was never in production as far as I can tell. Designed as a PA cab, pressed into service for Hi-fi as an economical alternative to the Khorn and others (IMO). Also note that the upper frequency horns, drivers, and networks are integral in the bass horn cabinet, for easier portability.

DM

[D-MAN]

PWK complained that too many were just copying him because they lacked the imagination to do their own design. I don't think that this is in any way a copy of his design, although one can easily see its heritage (no pun intended). However, please bear in mind that it is probably more closely related to my corner horn design than a La Scala.

Here is an extract for my second bass horn design along with part of the patent abstract... Please forgive the quality, it gets trashed when converted to a .jpg file for uploading. Looks like I drew it with a felt-tip pen on the back of a used paper napkin!

What do you guys think of the name - appropriate homage or rip-off?

DM

[Marvel]

I have a question about ports. Is it the volume of a port that makes it works correctly? In other words, can you change the dimensions of the port as long as the volume remains the same?

D-man -- love the look of these new ones. I have other questions you haven't answered yet so I'll send an email from home tonight.

[Colin]

sorry, but I have to ask: how is your design legally unique enough to deserve a patent?

[D-MAN]

With regards to ports, the size generally used in relation to the available cone radiating area and is slightly less in area than the cone area, but that depends on the tuning that one wants to achieve.

However, back-porting a front-loaded horn means that one uses the overall mouth area vs. cone (throat) area. The proportion is 2:1 in this case. Tuning is achieved by the length and diameter (hence, the volume) of the port area involved.

The ports can be reflex or ducted. While the port(s) is a cubic volume, and the other square inches, both can be regarded as being square inches in overall area, one will just have greater velocity of air movement than the other.

In theory, for higher output use, the ducted ports can be replaced by a rectangular slot or slots as ducts might tend to "chuff" in extremis. I chose to use ducted ports in the diagrams as they were the easiest to build, and looked the best for domestic use IMO and therefore that was the enclosures' most-preferred form.

The back chamber volume in this case is enlarged as compared to a sealed front-loaded horn, so that the resonant frequency of the volume is low enough to allow the ports to be tuned at about 30Hz, as the driver fr will allow in the larger space. The port tuning is well below the Flc of the horn itself.

The port will be more restrictive (or resistive to air movement) above its tuning and the horn itself will be most effective. As frequency goes lower, the horn will become resistive and the port will be more efficient. The two pathways trade off tranmission efficiency with changes in frequency somewhat like a teeter-totter (can I say that?).

DM

[D-MAN]

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On 6/27/2005 4:04:50 PM Colin wrote:

sorry, but I have to ask: how is your design legally unique enough to deserve a patent?

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do you think that you know how to EXACTLY build one? That is, without having ever seen the picture...

But really, I am not going to reveal the part of the design that I consider essential to its uniqueness and its characteristic feature. That's what a patent is actually for.

{edit} addressing "patentability" is a touchy issue - however, here is a list of what would be considered patentable:

#1) it has to be non-obvious, i.e., painting an invention green would be considered obvious, and would not be patentable. Obviousness is an area of confusion for laymen; take a look at all of the claw-style hammers that have been patented; although each is only slightly or very greatly different, they all do the same thing, which is pound in and remove nails and such.

#2) it cannot be pre-existing or otherwise available to the public prior to the patent application. However, in the case of claw hammers, invented by the Romans, pre-existance is a given, so there must be a new "twist" to the hammer design in question and/or its manufacture to be patentable, i.e., the famous tuning-fork in the handle, etc. In such a case any or all of the following would apply.

#3) it can offer an improvement to a pre-existing invention but the improvement must be clearly outlined and specifically claimed. A change in appearance (a goats-head claw-hammer, for instance) would qualify as an improvement to the art (at the time it was issued). It is non-obvious in that it is an entirely new and recognisable hammer (at the time). Additionally, a fish-head claw-hammer would be different and therefore new (at the time), too. Where this gets messy is if you wanted to do a fish-head and did one suspiciously close to the pre-existing one, except that you closed one fish eye. That would be obvious and not patentable, I would figure. But an entirely (or clearly)different fish-head WOULD be patentable if it improved on the previous fish-head design. This is the part that confuses most.

#4) it can embody materials or processes that are more efficient and/or economical than previous inventions or otherwise be a method of producing said invention such as a set of formulas or techniques new to the art (except food recipes, which are not patentable). However, the patent would not be that which is made, but is for the method or manner in which it is made. Issued patents cannot prevent previous inventions from being made in any case.

#5) it solves a particular problem with the current state of the art (of the invention).

#6) it is a new combination of inventions or parts thereof previously known to the art, but new in configuration (considered an improvement).

#7) most interestingly, it doesn't have to actually perform as stated in the application. It ONLY has to present the reasonable expectation that it will perform as stated. Many strange patents are issued that are scientifically questionable; the patent is intended to apply legal protection for an inventor's invention, and thus promote commerce, not stifle it. Statements concerning the performance of the invention are typically ignored. In particular, loudspeaker frequency curves, and other indications of performance are somewhat meaningless for a patent to be issued, that is, the issuance of a patent is based on the expectation that the invention fills a particular need or otherwise solves a stated problem. Frquency curves are there more for advertising purposes seems to me than proof of performance. Otherwise, PWK could not have upgraded the Khorn to a 15" driver when he patented a 12" one!

DM

[Colin]

guess I will wait, what does your design do better then?

[D-MAN]

It should perform pretty much like an A-7 except has a smaller footprint. The only other folded horn (that I know of) thats smaller would be PWK's "Little Bastard".

DM

[D-MAN]

One consideration was the horn mouth. I went with PWK on this one... sometimes the simple is best.

{edit} the exponential expansion would theoretically reduce distortion - however, the LS seems to be fine in that regard, probably due to the short length of the hyperbolic section, so...

One of the issues of such a short horn is that it has to be a certain large enough size to couple to the atmosphere and not cause reflections backwards into the throat. To prevent fore-shortening PWK used a 120+ expansion rate at the mouth. The Altec A7 uses an 80Hz 14" long horn for the same reason. The hyperbolic mouth section is also 14" long. The LS also uses a 60Hz "rubber throat" (different from the mouth terminal section rate) to give a nominal response of 70Hz fc per PWK's paper.

Like the Altec 825/A-7 cabinet, I chose to lower the frequency response by employing a porting mechanism tuned lower than the Flc of the horn.

The difference of a folded horn of longer length and a different design although it follows the general path layout of a BELLE rather than an LS, but its footprint is smaller than an LS, with a top cabinet, it is also taller, in keeping with my corner horns which I figure is an advantage for multi-channel use.

As far as patents go, the similarities of the Tattersall patent and the Altec 828/A-7 enclosure are easily discerned. At the very least, my design is differentiated from the PWK designs in that it is reflex ported. Few reflex-ported bifurcated folded horns exist, and none look like mine - mine is vertically oriented and folds horizontally. How much more different does it have to be to be "its own thing"?

DM

[DrWho]

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On 6/27/2005 3:56:43 PM Marvel wrote:

I have a question about ports. Is it the volume of a port that makes it works correctly? In other words, can you change the dimensions of the port as long as the volume remains the same?

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Sorta and no

The key concept behind a port is that it traps air, which then causes it to act like a spring inside the port. If you make the cross sectional area of a port larger, you will also need to make the port longer to maintain the same tuning. If you think about it, it makes sense because it's easier to push air through a wider straw (just imagine trying to breathe through a coffee straw that is long enough to be the same volume as a normal drinking straw). So I guess the easiest way to say it is that the port works on how easily the air moves through it (which then determines the springiness and thus the tuning).

If you follow the logic through, one would realize that a port could be made very short with a very small cross-sectional area. However, the problem here is air velocity. Basically, the smaller the cross-sectional area is, the faster the air is moving through the port and thus the louder the port noise. Generally it's best to design ports that keep the velocity under 20ms when the woofer is being pushed hard...anything under 20ms tends to be inaudible, under 10ms is ideal. There are also other issues of power compression and non-linear tunings and blah blah blah so the basic idea is to make a port as large as possible such that it can still fit in the cabinet.

[colterphoto1]

Nice analogy with the straw thing. You have a good way of explaining engineering in layman's terms. This will serve you well, young Skywalker.

Michael

[Deang]

Nice work D-man!

[D-MAN]

Thanks, Dean.

I got the following from the USPTO site. A better and official definition than I gave previously for those interested. Oh, yes, I forgot to add that in legal terms, the internet doesn't count as publishing as used below.

What Can Be Patented

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The patent law specifies the general field of subject matter that can be patented and the conditions under which a patent may be obtained.

In the language of the statute, any person who invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent, subject to the conditions and requirements of the law.

The word "process" is defined by law as a process, act or method, and primarily includes industrial or technical processes. The term "machine" used in the statute needs no explanation. The term "manufacture" refers to articles that are made, and includes all manufactured articles. The term "composition of matter" relates to chemical compositions and may include mixtures of ingredients as well as new chemical compounds. These classes of subject matter taken together include practically everything that is made by man and the processes for making the products.

The Atomic Energy Act of 1954 excludes the patenting of inventions useful solely in the utilization of special nuclear material or atomic energy in an atomic weapon 42 U.S.C. 2181 (a).

The patent law specifies that the subject matter must be "useful". The term "useful" in this connection refers to the condition that the subject matter has a useful purpose and also includes operativeness, that is, a machine which will not operate to perform the intended purpose would not be called useful, and therefore would not be granted a patent.

Interpretations of the statute by the courts have defined the limits of the field of subject matter that can be patented, thus it has been held that the laws of nature, physical phenomena, and abstract ideas are not patentable subject matter.

A patent cannot be obtained upon a mere idea or suggestion. The patent is granted upon the new machine, manufacture, etc., as has been said, and not upon the idea or suggestion of the new machine. A complete description of the actual machine or other subject matter for which a patent is sought is required.

Novelty And Non-Obviousness, Conditions For Obtaining A Patent

===========================================================

In order for an invention to be patentable it must be new as defined in the patent law, which provides that an invention cannot be patented if:

(a) the invention was known or used by others in this country, or patented or described in a printed publication in this or a foreign country, before the invention thereof by the applicant for patent, or

( the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country more than one year prior to the application for patent in the United States . . .

If the invention has been described in a printed publication anywhere in the world, or if it was known or used by others in this country before the date that the applicant made his/her invention, a patent cannot be obtained. If the invention has been described in a printed publication anywhere, or has been in public use or on sale in this country more than one year before the date on which an application for patent is filed in this country, a patent cannot be obtained. In this connection it is immaterial when the invention was made, or whether the printed publication or public use was by the inventor himself/herself or by someone else. If the inventor describes the invention in a printed publication or uses the invention publicly, or places it on sale, he/she must apply for a patent before one year has gone by, otherwise any right to a patent will be lost. The inventor must file on the date of public use or disclosure, however, in order to preserve patent rights in many foreign countries.

Even if the subject matter sought to be patented is not exactly shown by the prior art, and involves one or more differences over the most nearly similar thing already known, a patent may still be refused if the differences would be obvious. The subject matter sought to be patented must be sufficiently different from what has been used or described before that it may be said to be nonobvious to a person having ordinary skill in the area of technology related to the invention. For example, the substitution of one color for another, or changes in size, are ordinarily not patentable.

patent_info.txt