henrysnark Posted October 31, 2013 Posted October 31, 2013 (edited) Hey all So I picked up a mic pre/phantom power widget and a calibrated ECM8000 from a kind SNA member and have jumped balls-first into the cold waters of room measurement.. I'm fairly certain I've calibrated things okay (used .frd for mic, did SPLs, didn't do soundcard), and have the volume on my pre up fairly loud. I ran a series of four sweeps, and made sure the various pets/partners/gadgets were all set to silent for the duration of the test. Can anyone help me interpret these graphs? I'm running a pair of Omega XRS 8's which only output from 38hz --> 18kHz, but these results are still..surprising. Are they even possible? For the purposes of the test I removed the Primacoustic panels I usually have at first reflection points and also most of the dodgy Selby foam 'bass traps' I usually have jammed in all corners. I left two stacked in one corner behind a desk (and a thin curtain), as well as my little tile pattern of 8x small primacoustic panels on the rear wall. Will work on a floor plan of my listening space if it would be useful.. EDIT: description of the listening space is: WxLxH: 4m x 6.2m x 2.6m Long-wall speaker placement One short wall has glass doors onto balcony Other short wall is a kitchen (which disappears into a corridor, meaning one corner of front/behind-speaker long wall is 'missing') Thin carpet on floor. Thanks in advance -henrysnark Edited October 31, 2013 by henrysnark
Decky Posted October 31, 2013 Posted October 31, 2013 Q1. What are you trying to do with the measurements? Q2. Where was the mic when the measurement was done? The reason for Q1 is there to put everything in the right perspective - if you are not prepared to do something about the room, speakers, X-over settings or all of the above - there is no point taking the measurements. A bare minimum is adjusting your sitting position. The reason for Q2 is that the most important thing is to distinguish what is the speaker response and what is the room response. If you do not have an anechoic chamber then a standard 1m measurement is required to give you a benchmark. After that you can start thinking what is there to be done (assuming that you do not wish to change the speaker).
henrysnark Posted October 31, 2013 Author Posted October 31, 2013 Thanks for the quick response Decky. Answer to the first is I want to get serious about treatment and want some kind of objective guide to work from. Not keen on changing speakers, and have no crossover to work with. As to the second, the mic was in the listening position pointed upwards per Realtraps guide. Am open to any/all positioning changes. Makes sense re the 1m measurement. Is this a horizontal placement of the mic level with the cone? So I take it the measurements are possible then and it doesn't look like I have made some sort of elementary config stuff up ?
ArthurDent Posted November 1, 2013 Posted November 1, 2013 Entirely possible but you need to take more measurements at various positions around the nominal listening position. Keep the height and mic orientation the same but move 1/2 a metre at a time to the left and right, forwards and backwards etc. so you have a least 9 measurements. Overlay them all and then look at what's common and what's not. 1
Decky Posted November 1, 2013 Posted November 1, 2013 For 1m measurement you do not need to go bellow 200Hz - mic pointed to the centre of the driver. That will give you how the speaker works without (of with minimum amount) of reflections from the room. For bass response follow what Ken suggested 9 (maybe even more) measurements around the seating position for Fs under 200Hz. That average response will give you a good idea what are you really listenning to. If you carefull in recording the data you will capture standing waves in all directions around the "drivers seat". Do couple of measurements of frequencies above 200Hz and compare them to 1m curves - that will indicate any reflections of the side walls, floor or ceiling. It is a lot of work but that is what it is...
almikel Posted January 19, 2014 Posted January 19, 2014 Hi Henry, I'm still learning REW myself, but a couple of resources I found helpful: I'm assuming you've found the Hometheater Shack fourms. Paul Spencers numerous articles: http://redspade-audio.blogspot.com.au/2011/05/quickstart-guide-to-bass-measurements.html http://redspade-audio.blogspot.com.au/2011/05/rew-understanding-decay-and-waterfall.html Plus his Bass integration guide - parts 1-3 http://www.hifizine.com/2011/06/bass-integration-guide-part-1/ links to parts 2 and 3 are included and Nyall Mellor's whitepaper on what to target for 2 channel stereo http://www.hedbackdesignedacoustics.com/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf cheers Mike
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