Why Room EQ?
This table lists the main advantages of MathAudio Room EQ over a standard FIR-based (convolver-based) room correction system.
| MathAudio Room EQ | A standard FIR-based (convolver-based) room correction system |
| 1. Supports all sampling rates without resampling, avoiding additional distortion and noise introduced by resamplers. | FIR-based systems natively support only a single sample rate. Other rates are processed via resampling, which introduces measurable noise and distortion. |
| 2. Provides gentle, natural room correction because the sound of Room EQ’s high-order IIR filters matches the character of classical analog RLC filters. | Introduces artifacts specific to FIR filtering. The abrupt end of the impulse response produces a “digital” timbre similar to that associated with MP3 compression algorithms (which are FIR-based). |
| 3. Provides correction over the full duration of the room impulse response. | Corrects only the beginning of the room impulse response (typically 1–2 seconds). Since the full room impulse response is much longer, the FIR convolver corrects the initial part and then abruptly stops, leaving the tail uncorrected. This introduces distortion that is both measurable and audible. |
| 4. Operates without introducing pre-echo. Preserves the natural attack of the sound. Corrects the phase response of the room. | Linear-phase FIR filters introduce pre-echo, which degrades the attack of the sound. Additionally, they do not correct the phase response of the room. |
| 5. Operates with zero latency, making it suitable for real-time applications, live performance, and studio monitoring. Does not introduce audio delay during video playback. | FIR filters delay the audio, preventing use in real-time applications or live performance, and can cause a perceptible shift when watching video. |
| 6. Accurately corrects the low end of the audio spectrum. | FIR filters have substantially lower accuracy and resolution at low frequencies, where the most harmful room resonances typically occur. |
| 7. Gently corrects the high end of the audio spectrum. | FIR filters do not provide uniform resolution across all frequencies. Resolution is too low at low frequencies and excessively high at high frequencies. Excessive resolution can be as detrimental as insufficient resolution, producing a harsh and unpleasant sound. |
Some of the listed disadvantages of FIR-based systems can be partially or even fully mitigated using certain mathematical methods, but not all simultaneously. This is why we do not use FIR filters (convolvers) in our products — we avoid compromises.
How can one tell if a room correction system uses FIR filters? If the system description includes any of these terms — “convolver,” “FIR,” or “linear-phase” — it clearly indicates the use of FIR filters.
Many people misunderstand linear-phase filters, assuming that “linear” automatically means “better.” This is incorrect. Examine the impulse response of MathAudio Room EQ (see below) and compare it with that of a linear-phase room correction system. You will notice the pre-echo (pre-ringing) introduced by the linear-phase FIR filter, which degrades the sound’s attack. Moreover, these filters do not provide phase correction for the room. For high-quality audio, we strongly advise against using linear-phase filters or linear-phase equalizers.
To check for the presence of pre-echo in any room correction system, you can use the following simple method:
1. Download this audio file containing a Kronecker delta function.
2. Process it in your DAW using the room correction plug-in, and save the result as a WAV file.
3. Open the WAV file in a wave editor (e.g., Wavosaur) and stretch the waveform along both horizontal and vertical axes. This will reveal the “pre-reverberation” and “post-reverberation” introduced by the room correction system.
• Post-reverberation is necessary to compensate for the room resonances created by the natural reverberation of your room.
• Pre-reverberation, on the other hand, is an unnatural digital artifact that distorts the sound.
• Using this method, you can visually compare the amount of pre-reverberation across different room correction systems.