Hey all, long time lurker, been using the Skram for about 2 years now and decided it's finally time to post some proper calibrated measurements. I’m an acoustical engineer at QSC, and run my own custom rig as a side hobby. I've only been in acoustics for 2 years, before that I was an amplifier engineer so I'm still learning some of this stuff.
Been meaning to get this info for a while and finally had some outdoor measurements to make for work, so while I had things set up, I thought I would go ahead and get some comprehensive measurements for this build. I’m currently running them with the 21SW152-8, but we’ll be getting our hands on the new cost-effective Celestion TSQ2145 for evaluation soon, at which point I’ll get another indoor groundplane & impedance measurement. I haven’t added fiber fill/acoustic foam to mine yet, so that could be another interesting data point.
Indoor ground plane measurements are done with our 1/4th space calibrated, scaled, & windowed measurement sequence that we use for all product qualification. Also got some measurements of THD and harmonics at 10v. The one downside is that the signal path has >100ms latency for phase response and there are minor reflections even with the windowing of the impulse response. Unfortunately I can’t post pictures of this setup due to product confidentiality. 1w1m looks to be about 94dB SPL. I am a bit surprised how different the "knee" at 30 hz looks compared to previous measurements in this thread, I'm not sure where that difference is coming from...
Earthworks M30 measurement microphone used for all data.
ARTA outdoor setup, 22C, 30%humidity:
RME Fireface UCX
QSC PL-380
Q-SYS Core250i
Outline ET series turntable
Indoor measurement data:
Audio Precision AP2700 for impedance response
Lynx Aurora(n) audio interface
Grace m801mk2 mic preamp
Measured with SoundCheck 15
Outdoor setup has hard walls ~16 meters on either side, so spatial IR responses are windowed to 90mS (2x 16m). Turntable setup to rotate about the physical center of enclosure. Outdoor SPL scaled to match calibrated indoor measurement. I took 2 polar data sets, one with the enclosure vertical, with ports at the bottom, and one on its side, and you can see the slightly asymmetric polar response.
I’ve attached a .vacs file with all of the measurements, and I can provide all of the outdoor .pir files if someone was interested.
This is an amazing subwoofer, many thanks to @Ricci for his work. Hopefully this information will be useful to you, let me know if there’s anything else you would like to see, or clarification, and I’ll do my best to provide.
Skram Data.vacs
