Systems List › DIY › TC Sounds LMS Ultra 5400 18 Sealed
NotesThe LMS Ultra sealed system produces an excellent set of measurements starting with a frequency response that fits within a 6dB window from 35-700Hz and exhibits the typical sealed roll off below 35Hz. Additionally the 2.0 volt sensitivity is decent for such a heavy mms long throw 18" coming in at about 90dB above 45Hz and maintains a sensitivity of about 80dB at 20Hz which is one of the better results for this sealed enclosure. Inductance issues are nowhere to be found in either the response or distortion measurements. The response decay is also abrupt and clean in the waterfall and group delay measurements, as to be expected from a sealed enclosure.
An input of 4.1 volts into the system produced 90dB at 50Hz at 2 meters. The long term output compression sweeps are very clean also showing very little shifting of response and only moderate compression during the 130 volt 120dB sweep. Indeed the compression is less than 3dB even at such a brutal input level which corresponds to about 4500w into the minimum impedance of the system. The repeat 90dB measurement immediately after the 130 volt sweep indicates that there is some heat build up in the driver but this is not surprising. The titanium former, aluminum cone, pole vent, motor vents and massive voice coil combine to give the driver better thermal management than most. An even louder sweep was not tried due to running out of driver excursion between 10-20Hz.
CEA-2010 short term burst testing shows very low distortion levels and good maximum peak output for a single sealed driver over most of the range. In the deep bass below 25Hz the LMS Ultra system produces much cleaner bass than the majority of other drivers and as a result records higher output via CEA-2010. Peak output without regard for distortion is still much better than most.
The distortion results for the Ultra system are very good. In fact even during the 130 volt 120dB sweep the THD never exceeds 23%. Most drivers would be near 100% in the deep bass by this point. Above 25Hz the Ultra system never exceeds 8% THD even at this very loud output. The distortion is primarily 3rd harmonic but the rest of the harmonics are very low in level for the most part. This is a very clean system. In fact the limiting factor is often a mechanical over excursion noise rather than greatly distorted sound as with some other drivers.