WhereIsAtlas · Law
The Speaker Lawsuit That Turned on an Ellipse
Bose sued JBL and Infinity over the shape of a loudspeaker port, won $5,676,718.32, and produced a Federal Circuit ruling that patent lawyers still cite for how damages get calculated.
Bose Corporation sued JBL, Inc. and Infinity Systems Corporation in 1998 over US Patent No. 5,714,721, which covered a loudspeaker port whose boundary is defined by an ellipse. The District of Massachusetts found no literal infringement but infringement under the doctrine of equivalents, and awarded $5,676,718.32. The Federal Circuit affirmed on 17 December 2001, holding that Bose's mid-prosecution amendment adding "having a major diameter" did not narrow the claim, because an ellipse inherently has a major diameter.
What a port is, and why its shape matters
A loudspeaker cabinet is usually not sealed. It contains a port — a tube that lets acoustic energy from inside the enclosure radiate outward, which is how a small cabinet produces useful bass [1].
The shape of that tube matters a great deal. A badly designed port creates audible distortion: chuffing, whistling, noise. The specific thing Bose patented was the shape of the boundary around the port opening [1].
Bose owned US Patent No. 5,714,721, titled "Porting." It covered an invention by two Bose employees, Brian Gawronski and Gerald Caron, and its central claim described a port with smoothly flared ends where the boundary "is defined by an ellipse having a major diameter" [1]. In ordinary language: the hole is an ellipse, not a circle.
The suit
Bose sued JBL, Inc. and Infinity Systems Corporation — the court referred to them collectively as "JBL" — alleging that enclosures using the "Linear-A" curve or the "Exponential" curve incorporated the patented port technology [1]. Eleven models were named, among them the N24, N28, ND310, S38, SCS125, ESC300B and ESC350 [1].
The case was heard by Judge Patti B. Saris in the District of Massachusetts. The court granted JBL summary judgment of no literal infringement — the accused ports were not exactly what the claim described — but refused to dismiss the claim under the doctrine of equivalents, which reaches devices that perform substantially the same function in substantially the same way [1].
That distinction is what carried the case. Bose lost on the literal reading of its own patent and won anyway, because the law allows a patent to cover near-variants of what it literally claims.
After a bench trial the court entered judgment for Bose, and damages were set at $5,676,718.32 [1].
The argument about a word
JBL's most interesting appeal ground was prosecution history estoppel.
While Bose's application was pending, an examiner had objected that the claim lacked an antecedent basis for a later reference to "the major diameter of said ellipse." Bose's fix was to amend the claim to read "an ellipse having a major diameter" [1]. JBL argued that this amendment narrowed the claim, and that a narrowing amendment made for reasons of patentability closes off the doctrine of equivalents.
The Federal Circuit rejected that, and the reasoning is the best line in the case. The court noted that the Manual of Patent Examining Procedure recognises that a missing antecedent basis does not always make a claim indefinite, and that "an inherent characteristic of an ellipse is a major diameter." Because the phrase merely made explicit what an ellipse already is, it took nothing away [1].
So the decisive question in a multi-million-dollar patent dispute was whether adding a description of a shape's inherent property changes the shape. It does not.
One detail worth noticing: the court applied the Federal Circuit's en banc decision in Festo Corp. v. Shoketsu, and recorded that the Supreme Court had granted certiorari in that case [1]. Festo became the leading modern authority on prosecution history estoppel. This ruling sits right at the edge of that change.
The reference that was a different curve
JBL also tried to invalidate the patent using a French patent application, the Dehaeze reference. The district court excluded it, having found that Dehaeze disclosed a hyperbola — which differs from an ellipse "in both shape and mathematical formula" [1]. The court observed that it would have weighed the reference differently had it disclosed an ellipse. The Federal Circuit found no abuse of discretion [1].
The whole case therefore turned on telling two conic sections apart. An ellipse is a closed curve; a hyperbola is not. One was patented, the other was prior art, and the difference between them was worth $5.68 million.
Why patent lawyers still cite it
The third appeal ground was about the size of the cheque, and it is the reason the case appears in patent-damages literature.
JBL argued the royalty had been calculated on the entire value of the loudspeaker systems, even though the patented port was a small component of them, and that no real negotiating party would have agreed to that [1].
The Federal Circuit upheld the award under the entire market value rule, which allows damages based on the whole apparatus when the patented feature is the basis for customer demand [1]. The court pointed to findings that the patented port worked inextricably with the other components as a single functioning unit, that it eliminated port noise and improved bass reproduction, and that a JBL marketing executive had acknowledged improved bass performance was a prerequisite for going ahead with certain models [1]. Bose had also shown that it marketed the loudspeakers on the strength of the patented feature, and produced evidence of a sales increase the year after introducing speakers containing it [1].
That is a demanding test, and it is the reason the case is taught: it shows what a patentee must establish to recover the value of a whole product rather than a component.
Counsel, and where the parties ended up
Bose was represented by Fish & Richardson. JBL by David Boies of Boies, Schiller & Flexner, with Jones, Day, Reavis & Pogue [1].
And the two defendants did not stay rivals for long. JBL and Infinity Systems both ended up under the same owner, Harman International — which has been a wholly owned subsidiary of Samsung Electronics since March 2017. So the company that lost this case is, today, part of a group that owns JBL, Infinity, AKG, Lexicon, Mark Levinson, Revel, and since September 2025 Denon, Marantz and Bowers & Wilkins as well.
The part that is easy to get wrong
Two things about this case are routinely confused, and both matter if you are trying to understand who sues whom in audio.
The first is the type of patent. The '721 patent is a utility patent — it claims how something works. That is a different instrument from a design patent, which claims how something looks. Design patents are what get asserted in cases about speakers that resemble each other, and the two are governed by different tests. Mixing them up produces nonsense.
The second is who the giant is. In this case Bose was the plaintiff and Harman's brands were the defendants — but Harman, as part of Samsung, is now vastly the larger company. The pattern in consumer audio is not that one monopolist suppresses everyone else. It is that a small number of large firms hold overlapping patents on similar products, and they sue each other in both directions. Bose won this one. Bose has also been on the receiving end of patent claims.
Which is the honest lesson of the case: in a market where everyone's speakers do roughly the same thing, patent litigation is a cost of doing business rather than a weapon that settles anything permanently.
Entries in this story
Sources
- Bose Corporation v. JBL, Inc. and Infinity Systems Corporation, 274 F.3d 1354 (Fed. Cir. 2001) — Public.Resource.Org (2026-09-19) ↩
- Bose Corporation v. JBL, Inc. and Infinity Systems Corporation — CourtListener (2026-09-19)
- Assessing Patent Infringement Damages — Morgan Lewis (2026-09-19)