Wedgwood says: �The Tibia Profunda and Tibia Profundissima are the 16 ft. and 32 ft. pedal extensions of the Tibia Plena.� Irwin, on the other hand, defines it differently: A 32' manual pitch, and, if correct terminology is used, a 64' pedal pitch of the stoppered Tibia Clausa. There is no theoretical or practical reason why this low pedal flue should not prove useful, except, perhaps, slowness of speech. The organ-building world would seem to disagree with Irwin, as there are only two true 64' stops in existence, one being a Contra Trombone (Town Hall, Sydney, Australia), the other being the a Diaphone Profundo (Convention Hall, Atlantic City, New Jersey, USA).