Dave MacKay Posted March 7, 2022 Share Posted March 7, 2022 I recently tried characterizing the performance of my 1986 La Scalas using a calibrated UMIK-1 microphone and REW. The results surprised me so that I wanted to share them with the forum in the hope of eliciting some comments. TLDR: The La Scala bass performance was much worse than expected. Why? How can that be addressed? Results I took measurements with REW at 3 listening positions (left chair, right chair and in between the chairs; see positioning diagram, below). The measurements were taken with the amplifier set to full range speakers with no signal being directed to LFE for subwoofers. This graph (which uses 1/12 smoothing) shows that the low-end performance of my La Scala drops precipitously below about 200Hz and is pretty much non-existent below 100 Hz. For interest, here is the same data for frequencies below 200 Hz (i.e., zoomed in): Although these charts use a dBFS scale, the ones using an SPL scale are identical (see bottom of post). Clearly. my La Scala speakers perform poorly for frequencies below about 165 Hz (i.e., the lowest 3 octaves): performance drops from around -50 dBFS to around -80 dBFS. Do these results seem reasonable? I expected the La Scala’s bass to be OK until about 50 Hz but I was surprised to see their performance plummet below about 200 Hz. According to discussion on this forum, the La Scala stops acting as a horn below 104Hz (i.e., > 3.3m wavelength) and does not produce much bass below about 51 Hz (i.e., > 6.7m wavelength). However, my results show much poorer performance than that. I am interested in comments from forum members about these results. My system My 1986 La Scalas have new Crites AA networks and @Dave A's SMAHL tweeters and lenses. I laminated 3/8 Baltic Birch plywood to the exterior of the cabinet to improve rigidity. I’m driving the La Scalas with a Yamaha R-N803 100W/channel receiver. Although I have a pair of subwoofers, I turned them off for the test so that I could get a base line with just the La Scalas. I configured the amplifier to use Full Range speakers without subwoofers. The distance to the speakers as per the Yamaha’s YPAO (Yamaha Parametric room Acoustic Optimizer) tool was the same as I measured with my tape measure (roughly 11' to one and 12' to the other). As per YPAO’s recommendation, the Right speaker level was set 1 dB higher than the Left. Positioning This diagram shows my listening room: In the meantime I’ve been trying to blend my 2 THTLP subwoofers with the system, using the DSP features of the SPA250DSP plate amplifiers that power them. I may share the results I’ve achieved (so far) in a separate post. TLDR: music sounds anemic and lacking in bass when I get a flat SPL chart (20 Hz – 20 kHz). TIA for your comments and suggestions. In case you're interested - same charts but with SPL scale Here is the 20 Hz - 20k Hz chart using an SPL scale: Here is the 20 Hz - 200 Hz (i.e., zoomed in) chart using an SPL scale: Quote Link to comment Share on other sites More sharing options...
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