Does the DTS-10 deserve new test charts & graphs to better represent what its owners actually hear at home?
I certainly think so.
I’ve always wondered why the existing frequency response, spectrogram, waterfall & distortion graphs are so awful, and so different from what I’m experiencing at home, but I finally realized that the DTS-10 was never designed to play outside in the anechoic space of an open field, it’s supposed to be played in the smaller acoustical space typically found within the average home.
I think the problem is that it’s become so widely accepted that the best place to measure a subwoofer or full range speaker is either in an anechoic room or in the great outdoors in order to prevent reflections from contaminating the measurements. This method works well for direct radiator designs (i.e. sealed, infinite baffle or vented designs) but it definitely does not work well for the DTS-10 because the acoustical transformer properties of a horn are greatly affected by the acoustical impedance of the air that they are designed to play in, whereas a direct radiators response is not appreciably affected at all.
Tom Danley has already explained this in post
#430 of this thread. Tom answers multiple questions in that post, but in paragraphs 1, 2, 3 & 5 he explains to "bossobass" how the frequency response of the TH-115’s gets smoothed out when it's operated in a space with higher acoustical radiation resistance, which occurs when either multiple subwoofers are operated close to each other, or when a single sub is operating in a smaller fractional space. (like indoors or close to a wall or corner)
Tom makes it very clear that the DTS-10 was never designed to operate in a free space environment.
Tom’s attached picture at the end of the post (visible
here) shows multiple characteristics affected when operating in a higher acoustical radiation resistance location, notably:
- a flattening of the power response curve.
- extending the low frequency cut-off point.
- increasing efficiency/raising sensitivity.
I think the only fair way of assessing the DTS-10’s true capabilities are to measure them in a small acoustical space that is somehow devoid of reflections, but I don’t know how that can be done. I’d like to hear your opinions/suggestions on possible methods that can achieve that goal.
Previously, reviewers made use of the near-field measurement method when testing subwoofers indoors, where the microphone is placed as close to the sound source as possible in order to reduce room reflection contribution to a minimum. This is the only method I can think of that will provide measurements more closely resembling what I hear in my listening position.
Examples of outdoor versus near-field indoor measurements: (Note: no EQ is used on indoor signals)
Outdoor measurement:
Notice the typical peaky response with a major resonance at 55Hz.
My indoor near-field measurement, positioned in right front corner of room, sub is parallel to and approximately 6" from right wall, mouth is facing wall:
Notice how the peaky response is greatly reduced, and the 55Hz resonance has dropped to 51Hz.
Indoor near-field measurement, right front corner diagonal placement: (sub placed 45° against front and right wall with mouth facing corner)
Notice how the deep bass energy is higher than the upper bass energy now.
Indoor near-field measurement comparison, parallel to diagonal placement differences:
This graph shows just how much deep bass energy is gained without changing the input drive level just by placing the sub diagonally in the corner, also the 51Hz peak has now dropped to 47Hz!
Outdoor spectrogram:
Most of the energy is in the upper bass and isolated to two narrow frequency domains.
Indoor near-field spectrogram:
Notice how the bass energy is more evenly spread out and extends well below 20Hz.
Outdoor waterfall diagram:
Notice the two frequencies that tend to take longer to decay in an outdoor environment.
Indoor waterfall diagram:
Notice how all frequencies take longer to decay when measured inside an enclosed room, but the two previously peaky frequencies are actually lower in amplitude after 300ms then the outdoor measurements indicated.
Six-seat average frequency response, no EQ:
Notice how different this response is compared to the outdoor measurement diagram. The DTS-10 was definitely designed to work in the higher radiation resistance environment of an enclosed room.
Equalizer settings needed to obtain a flatter frequency response:
This image shows the equalization required to create a flat response at the listening position. Notice all gains are set to less than +/-5 dB, and even the large outdoor 10 dB peak at 55Hz now only requires a 2.5 dB cut at 47Hz, all due to the effects of indoor radiation resistance increases.
I think all DTS-10 owners can ignore the wildly fluctuating frequency response graph that was taken in an outdoor environment. The actual frequency response is determined more so by the space it is operating in than it does for direct radiator design subs.