Kalkmann Audio B.V.

Suddenly, the sound is clear. 

The hearing impaired positive on new speaker. 

• Huib Kalkman founded a company in self-designed speakers.

• By coincidence these speakers have huge success by the hearing impaired.

By Wim Köhler. 

ROTTERDAM. A speaker for the hearing impaired, it seems a contradiction, but Kalkmann Audio located in Breda (the Netherlands) builds them. Several retail stores/ chains selling hearing devices have already integrated the speakers in their collection. 

It started by coincidence when five years ago, Huib Kalkman decided to start up a company. Realising his dream, he started to develop speakers. The first speakers produced received very positive reactions from hi-fi enthusiasts and audiophiles. “A year ago, I was visiting a customer”, Kalkman says. “His wife is hearing impaired and all of a sudden she said, “hey, what’s this? I can hear the sound from that speaker very well” Especially spoken voice and singing were experienced very clear”. 

Acoustic professionals find the Kalkmann speakers to be “respectable”. Acoustic professional doctor Marinus Boone of the Technical University Delft briefly measured the speakers: “the pulse reaction looks very good, but based on that I cannot say how people experience the sound from the speakers”. 

In any case, Kalkman’s speakers are different. The secret is that two identical speaker units – other speakers mostly have speakers units of different size – both receive an identical sound signal which comes directly from the amplifier. In speakers based on conventional technology, an electronic filter is used to direct high frequencies to the one (smaller) speaker unit and the low frequencies to the other speaker unit which is in most cases bigger. “Such an electronic filter – “often the pride of speaker manufacturer”-, says Kalkman “creates distortion of sound”. 

Kalkmann’s identical speaker units are built in chambers that differ in size. Kalkman: “the speaker unit with the smaller resonance space acts as a high tone speaker, while the speaker unit placed in the larger chamber with a bass reflex pipe acts as a low tone speaker. Furthermore, the body walls of the speakers all contribute to the creation of the sound, similar to the sound-box from a violin.”

Manufactures of speakers using conventional technology try to minimize the influence of the speaker’s walls as much as possible. 

Furthermore, the Kalkmann speakers have a mass of granular material in the bottom of each speaker that absorbs the unwanted vibrations. This is also covered in the patent, just as the “linking” of the separate chambers behind the individual speaker units. The chambers are connected by a narrow opening, of which one side is formed by a wedge. “The wedge vibrates with a high resonance figure, creates pressure and propelling the sound.” 

The sound from Kalkman’s speakers attracted a lot of people to his company in Breda. This resulted in several contacts with the Dutch Association of Hearing Impaired (NVVS) and with the Hearing Association (Hoorstichting). Kalkman designed smaller speakers that can be easily connected to, for example, the television. Kalkman: “often married couples come to listen, of which one is hearing impaired. When watching television, one wants to increase the sound level of the television while for the other it is too loud. This leads to conflicts. Or the person that is hearing impaired puts on a headset, which results in difficulties in normal communication and interaction. Here, in our listening room, we observe that there is no need for a headset and that the volume level can be set at an acceptable (low) level for both.” 

Audiologist doctor Jan de Laat of the Leids Academic Medical Center organised a “blind” listening test with ten people that are hearing impaired. Behind a non transparent screen Kalkmann speakers were placed as well as “regular” speakers of the same size. The hearing impaired listened to three musical fragments and a fragment from the television news broadcast. Each person listened to the fragments twice, one time using the Kalkmann speakers and one time using the “regular” speakers. At a form they checked boxes when the fragments were best experienced. The results were positive for the Kalkmann speakers, although not overwhelmingly. In almost two out of all three sound fragments, Kalkmann speakers were preferred. Three out of ten of the hearing impaired listeners constantly checked the boxes for Kalkmann as preferred speaker. Others scored fifty-fifty. 

How’s this possible? Audiologist Jan de Laat: “most listeners had their hearing device turned on at normal level. A lot of hearing devices are produced specifically focussing on audibility of speech. The chromatic spectrum of music is then lost and it becomes very difficult to hear differences that people without hearing impairment do hear. Despite this, I have heard from several patients that with Kalkmann speakers enjoyed sound again. The sound is more round, full and pleasant.”

People without hearing impairment hear a crystal clear sound from the Kalkmann speakers. Acoustic professional Boone: “for a long time we already know that when a speaker provides such a clear sound the audibility is far better.”

Possibly, the solution is simply that the hearing impaired now allow themselves to listen to speakers with clear and undistorted sound for the first time resulting in better audibility.