Comparison of Boundary Microphones

Boundary microphones are often chosen for their convenience as they have a low profile and a wide coverage, while requiring minimal setup at the same time. However, not all boundary microphones perform the same and choosing one is difficult as subtle differences in design, polar pattern, and build quality can dramatically affect intelligibility and noise rejection. This article compares several boundary microphones on the lower end of the price range to see how they differ in real-world use. Since there are many tests with repect to drum micing, this article aims at using boundary microphones for the recording of piano and vocals.

Microphones

Six different boundary microphones were included in the test. Table 1 lists all microphones with some technical details as stated by the manufacturers. Figs. 1 and 2 shows the different microphones with cardioid and omnidirectional polar pattern. From these figures it becomes clear that, amongst others, the form factor depends on the pickup pattern of the microphone. Noticable is also the similarity between the Behringer BA 19A and the the t.bone BD 500 Beta.

Fig. 1: Boundary microphones with cardioid pattern

Fig. 2: Boundary microphones with omnidirectional pattern

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Table 1: Overview of the most important specifications of the compared interfaces

Setup and Recording

Two different settings were taken into account for the comparison. First, the microphones were placed within a piano with closed lid. This is a typical case for the use of boundary microphones as the classical way of micing a piano does not work if the lid is closed. Due to the limited space and since all microphones shall be placed at the same location inside the piano, only one microphone was used at a time, resulting in a total of six recordings.

As a second test case, vocals have been recorded. For this, the microphones have been placed on a table in such an arrangement that the distance between the singer and each microphone was about the same. Accordingly, the vocals could be recorded with all microphones at the same time.

Throughout the different recordings, all EQ and attenuation settings were set to neutral as far as the microphones had such options.

Recordings

Comparing the recordings, it becomes clear that the Behringer BA 19A and the the t.bone BD 500 Beta are not only similar in terms of form factor but also in terms of acoustic response. The sounds that both microphones pick up sounds very similar in both recordings. Regarding the piano recordings, these microphones sound slightly aggressive at higher frequencies in comparison to most of the other microphones. This slight aggressiveness is also present in the recording with the AKG Crown PCC160 which, at the same time, contains less low frequencies. The comparison of the frequency spectrum of the recordings in Fig. 3, supports this view. The fourth microphone with a cardioid pickup pattern, the Superlux E303B, is similar to the PCC160 in terms of low frequencies but does not have the aggressiveness at higher frequencies.

In comparison to the microphones with cardioid pattern, the representatives with omnidirectional patterns deliver a sound that sounds fuller. This is not surprising as omnidirectional microphones can transmit lower frequencies as consequence of their physical realization. In direct comparison of the Beyerdynamic Opus 51 and the Superlux E304B, it seems like the latter sounds slightly “in the box”. The sound is not as clear and transparent as the Opus 51.

Similar findings can be made from the vocal recordings. The BA 19A and BD 500 sound very similar while, this time, the noise stands out. To make the recordings comparable, all files have been normalized to the same level. This is especially necessary as the different microphones are different in terms of sensitivity and, therefore, their signal output varies. Comparing the original recordings, the RMS of the BA 19A, BD 500 and Opus 51 is about 10 dB lower than for the other microphones. Both microphones from Superlux have the highest output among the tested models. This is a consequence of the different sensistivities as listed in Table 1 for the different microphones.

In comparison to the microphones from Behringer and t.bone, the Superlux E303B sounds a bit more present. This can also be said about the PCC160, which seems to have the clearest sound of all in the vocal comparison of the cardioid microphones. Further taking the omnidirectionals into account, the Opus 51 from Beyerdynamic sounds similar to the PCC160 with a clear representation of the sibilants.

The frequency spectra from the different microphones for the vocal recordings are shown in Fig 4.

Fig. 3: Frequency Spectrum Piano

Fig. 4: Frequency Spectrum Vocals

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Conclusions

When comparing the different recordings, one thing becomes clear again: the right microphone depends on the specific use case. Different sound sources demand different characteristics in clarity, frequency response, and spatial reproduction while each microphone brings it’s own flavor. Therefore, any rating is subjective when it comes to the actual sound of a recording.

Looking at the cardioid microphones in the comparison, the Superlux E303B stands out as the choice for piano recordings. It delivers a detailed sound that captures the instrument’s dynamics and, especially, does not have the aggressiveness at higher frequencies that other microphones showed.

For vocal recordings, however, the AKG Crown PCC160 takes the lead among the cardioids. Its performance emphasizes vocal presence, providing a focused and natural reproduction that suits spoken word and singing alike.

Overall, the clear winner of the comparison is Beyerdynamic Opus 51. With its exceptionally clear sound and balanced representation of lower frequencies, it offers the most versatile and refined performance across both piano and vocal applications.

Audio Files

The recordings and corresponding plots of the frequency spectra are provided below.