RBH T-30LSE Measurements & Analysis
Measuring such a massive speaker system proved challenging. Rather than risk damaging these speakers and attempting to pull measurements outdoors, I did my best to do a combination of summed and scaled in-room nearfield and listening position measurements. An even greater challenge was determining the proper measurement distance where all of the drivers acoustically converge. This happened somewhere between two meters and the listening position. Unless otherwise stated, all measurements are of 1/12th octave resolution.
Figure 1. Impedance & Phase
The saddle point in the impedance graph lies just below 20Hz. While these speakers represent a relatively benign phase shift of +12 to -30 degrees across the entire audio band, the dip of 3 ohms centered around 90Hz and 2.5 ohms above 6kHz gives concern for driving them with amplifier of modest current output. I suggest using a beefy amp safely rated down to 4 ohms and definitely using an amplifier with a lowish output impedance to minimize frequency response variations. These speakers truly revealed the lackluster performance of the Panasonic SA-XR50 I keep on hand as a reference to poor amplifier performance. With the Panasonic powering these speakers, the natural reverb and ambience in vocals all but disappeared as the soundstage folded and the bass became sloppy and one notey sounding.
Figure 2. Nearfield Summed Bass Response
This plot represents the summed nearfield response of the woofers and the port which was scaled by a correction factor of 20*log10 (4/8) or -6dB to account for difference between the cone diameter and the port diameter. This measurement approximates an anechoic response. Note the -3dB point is around 18Hz. Production units are tuned to 20Hz with slightly more output in the 20-40Hz region. In most rooms, I think I’d prefer the lower tuning of my preproduction units since room modes usually cause additional reinforcement in this region. Slightly limiting the output here will allow for more placement flexibility and less EQ’ing necessary to flatten in room bass response.
Figure 3. ½ meter In Room Ground Plane
Figure 4. Subwoofer Power Compression Tests In Room Listening Position
The T-30LSE subwoofers can really handle the power and punch out some high SPL’s. We couldn’t measure any appreciable compression or power bandwidth loss to the limits of our amplifiers (running 400wpc) above 20Hz on this system!
Figure 5. Full Range Power Compression Tests In Room Listening Position
The top half of the T-30LSE system remained equally composed and willing to pump out insanely loud SPL levels (at the 400 watt limit of our amplifier) with no hint of compression. Don’t try this test with a conventional 2 or 3 way system at these power levels.
Figure 6. 2 meter On/Off Axis Frequency Response
The on/off axis response of these speakers remained very linear, exhibiting excellent dispersion characteristics. The smoothest response was found with just a slight toe in of about 7 degrees. The excessive high frequency roll off is a function of the drivers not fully summing at this distance and is not representative of what the listener will hear at a listening distance greater than a few meters (see Figure 7).
For speaker placement, I suggest starting with no toe in at all and experimenting to find the optimal response based on your room dynamics and listening preferences.
Figure 7. Frequency Response Comparison of T-30LSE & T-1 SE/R @ Listening Position
I found it interesting to note a very similar response curve at my listening position between the T-30LSE and the T-1 SE/R horizontally oriented as a center channel just below the screen. I did extensive listening from the far left and right seat and found this to be a superb center channel over an unusually wide listening area.
