- 30.0%Low-Frequency Extension
- 5.0%Std. Dev. @ 70
- 20.0%Std. Dev. @ 80
- 15.0%Std. Dev. @ Max
- 20.0%Max
- 10.0%Dynamic Range Compression
A TV's frequency response is a method used to evaluate the sound quality from a TV by comparing the frequency output by the speakers to a reference target. By measuring the amplitude of sound across a range of frequencies, we can determine how accurately a TV's speakers reproduce sound. We measure the frequency response of TVs from 20Hz to 20KHz, at 70 dB SPL, 80 dB SPL, and Max SPL (i.e., the TV is set to maximum volume). The results are then broken down for evaluation into low-frequency extension, response error @ 70, 80, & Max, dynamic range compression, and maximum loudness. If you're ready to start shopping, check out our picks for the best sounding TVs.
Test Methodology Coverage
Our frequency response test was first added in test bench 1.0, and it really hasn't changed at all since then. We also used to measure the total harmonic distortion as part of our sound quality testing, but that test was dropped in our 2.0 update. Learn more about how our test benches and scoring system work.
| 1.0+ | |
|---|---|
| Frequency Response | ✅ |
When it matters
Frequency response is the most important part of audio reproduction. For the most part, the perceived subjective sound quality of a speaker can be predicted from its frequency response1,2,3,4. It describes how accurately a system reproduces each frequency of audio content in terms of amplitude. A TV with a good sound has an extended bass, a neutral, balanced frequency response for clear dialogue, and it can reproduce the audio content at high-intensity levels without compression or pumping artifacts.
At the end of the day, though, a TV's frequency response only matters if you plan on using your TV's speakers. If you mainly plan on using a connected soundbar or home theater system for your TV's audio, then the quality of the speakers doesn't matter.
Our Tests
We test the TV's frequency response with its factory settings. If the TV comes with a room correction system, we start by running that feature to calibrate the sound prior to the measurements. The TV is placed on a table as close as possible to the back wall, and is connected to a PC via HDMI. We use sine wave test signals that cycle through our range of test frequencies, and record the amplitude of the resulting sound wave produced by the TV's speakers. The test signal for our frequency response measurements is a 16-bit/48KHz 20-second sine wave that sweeps through the frequency range at -6 dB FS (RMS) between 10Hz and 22KHz.
The measurements are recorded using a calibrated Dayton Audio EMM-6 microphone, placed at the optimum viewing distance for each TV's size, and connected to a Focusrite Scarlett 2i2 audio interface. The signal level is calibrated post-compensation (i.e., after being flattened by applying the target response) using a pink noise limited between 500Hz and 2KHz. The resulting sound pressure level (SPL) is measured and calibrated with a GalaxyAudio CM-140 SPL meter, which is set to C-weighting and Slow. Once we've captured the data, the results are calculated automatically and recorded in the review.
Target Response
Once we've recorded the amplitude produced by the TV's speakers at each frequency, we need something to compare it to in order to determine if it's accurate or not. Our reference for the ideal TV frequency response is the loudspeaker. For loudspeakers, it is widely accepted that the ideal response is a flat frequency response measured with a measurement microphone, on-axis, in an anechoic environment. There have also been studies done on the preferred in-room response of loudspeakers, most notably by Harman5,6. It concluded that the preferred in-room loudspeaker response is a smooth curve from 20Hz to 20KHz with about a 9-10 dB downward tilted slope, and that a flat in-room response for a loudspeaker will sound too bright and thin. In general, if a loudspeaker has a flat on-axis response in an anechoic setting, its treble won't need any adjustments, but the interactions between the speaker and the room in the bass range should be dealt with7.
The target for our TV measurements is based on the Harman in-room loudspeaker response and has a 9 dB downward slope from 20Hz to 20KHz. Also, due to the large variance in the shape and size of rooms and their big impact on a TV's in-room response, we believe that all TVs should come with a room correction system. This is why we test the sound of TVs in a regular room and expect the TVs to correct for the modes of our test room. The result of such measurements would better correspond to the actual experience that the consumer would have with their TV, compared to measurements done in an anechoic setting.
Low-frequency Extension
Low-frequency extension (LFE) shows us how deep a TV's bass response can get. It's calculated by determining the lowest frequency where the TV's frequency response reaches -3 dB of our target, using the 80 dB pass, post-compensation. The 70 dB SPL and Max SPL passes are not considered in the LFE calculations in order to reduce the effects of noise floor and compression/pumping on the process.
LFE values of 60Hz and lower should be considered good, especially for a TV, since an extended bass is not needed for producing natural dialogues. A TV with an LFE of 200Hz doesn't produce any bass and will sound quite thin. Extending the LFE down to 120Hz adds significant warmth to the sound, but still no thump or punch. A TV that has an LFE of around 60Hz does have body and punch to its bass, but still lacks thump and rumble, which is produced in the sub-bass region. Also, frequencies below 40Hz, which correspond to thump and rumble, are mostly felt as tactile sensations rather than heard as musical tones.
Std. Dev. @ 70
The standard deviation at 70dB shows us how far a TV's measured frequency response deviates from the target response at a low listening level. This is relevant if you're watching TV in a quiet room, like if you're watching late-night talk shows and don't want to bother anyone else. We calibrate the TV to output 70dB at the recommended viewing distance for the TV's size. Once that's done, we play through our sound sweep and measure the difference between the TV's frequency response and the target curve, calculated between the TV's LFE frequency and 20KHz. However, a perceptual weighting filter is applied prior to the standard deviation calculation, since human hearing is less sensitive to the sub-bass and high-treble regions.
A TV with a low error in its frequency response produces a smooth and relatively flat curve. Typically, TVs don't produce any sub-bass and lack quite a bit of mid-bass. This results in a sound reproduction that doesn't have any thump or rumble and lacks quite a bit of body and punch. Peaks in frequency response between 1 and 4kHz increase the detail and projection of dialogue, and dips can have a noticeable impact on speech clarity.
Std. Dev. @ 80
We repeat the process used for the 70 dB SPL, but this time with the TV calibrated to 80 dB SPL. This represents a more moderate listening level that all TVs can reach comfortably.
Std. Dev. @ Max
Nearly all TVs can hit 80dB SPL below max volume, but above that point, it really depends. On average, TVs can hit up to about 87dB SPL, but some exceed 90dB. Because of this variance, we can't use a fixed volume level for our final data point, and instead simply test each TV at its max volume. This test usually shows more flaws, and the sound profile is usually less balanced, with more variation at different frequencies due to compression artifacts and pumping.
Max SPL
This test records the sound pressure level that the TV can produce at the optimal viewing distance and at maximum volume. The test signal for this measurement is the same as our calibration signal (pink noise, limited to 500Hz or 2kHz). The measurement for this test is performed when the TV is being calibrated for the Max SPL pass. The TV level is calibrated post-compensation (i.e., after being flattened by applying the target response) using a GalaxyAudio CM-140 SPL meter set to C-weighting and Slow.
A TV that gets loud enough for most use cases measures above 88dB SPL at optimum viewing distance for its size. This means dialogue is still easily understandable even in a loud environment (i.e., a relatively noisy office). For use in a quiet room, the majority of TVs should be considered good enough. But for some other use cases, like sports viewing, it's crucial to have a TV that can get quite loud.
Dynamic Range Compression
This test compares the frequency response of the TV at 70dB SPL to its response at Max SPL. The actual value is derived by subtracting the 70dB curve from the Max SPL response and then calculating the standard deviation of the resulting difference curve. Most TVs struggle at max volume due to the size of their speakers, and one of the ways this affects the sound is by producing pumping and compression artifacts. That is, the TV won't be able to produce the same frequency response at Max SPL that it did at 70dB SPL, which shows as a drop in level in the bass and treble region.
Conclusion
If you plan on using your TV's built-in speakers, then getting a TV with a good frequency response is essential. While most TVs lack deep bass, you still want them to produce clear dialogue that's easy to understand, and you want to make sure it gets loud enough for your environment. Our frequency response test aims to answer all of these questions, and shows how a TV's speakers perform at a range of volume levels, ensuring you don't need to enable subtitles on your TV just to understand what's going on.