$199 MMMM Horizontally Oriented Measurements
If you were setting out to
design a speaker with the worst off-axis response possible, you should use a
whole bunch of identical horizontal drivers.
This next center channel speaker does mostly that, with four identical
“full range” 2.5 inch paper drivers, two in the front and two inside to help
load their ported enclosure. It could be
said that this speaker “has no highs, has no lows, must be…”, but because the
front two drivers are oriented at an angle from each other, this speaker
maintains its mediocrity with a fair degree of consistency. This company’s ad copy states that their
design “’locks’ dramatic dialogue to the screen.” If by this they mean that their design
diffuses dialogue across your room, they would be right on.
In the 1/24 octave chart below, you can see severe wave interference in the top three octaves (2.5 to 20 kHz), as well as some trouble in the upper midrange (1.3 to 1.8 kHz). Most of the narrowest spikes are inaudible in practice, so we’ll need to smooth out this data a bit and calculate how much the frequency response varies from the normalized on-axis measurement.
In the 1/6 octave chart below we can see that the wave interference is quite audible around 1.4 kHz and becomes severe above 2.5 kHz. This charts shows that there are angles at which you can get over 10 dB of wave cancellation in the frequencies that are critical for vocal intelligibility. A 10 dB loss of significant portions of the lower treble would be perceived as being half as loud. The biggest problem is that the behavior is not linear or predictable. You can’t just turn the volume up to compensate for the low fidelity sound that the other seats would experience.
Around 20 degrees off-axis of the loudspeaker, one becomes on-axis to one of the angled “full-range” drivers. When you get on-axis with one of these beauties, the high frequency beaming that occurs from trying to make a 2.5 inch driver into a tweeter becomes apparent. There is an audible peak around 11 kHz when you’re directly in front of a driver, which would sound sibilant and tizzy. Combine that harshness with the loss of lower treble and upper midrange that brings presence and intelligibility, and you’ll be undermining the entire experience. Disappointing the spouse won’t help your next request for spending the family budget on “what is it you want now?”
The best way to minimize wave interference is to minimize the frequency range that redundant horizontal drivers reproduce. This MMMM speaker (or is it a FF?) doesn’t relieve the drivers with a crossover, and so we have to calculate and score its variation in horizontal frequency response from 80 Hz to 20 kHz, which comes out at 1.81.
