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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Sub integration - please evaluate (SPL graph attached) posted by VynylTap on January 12, 2009 at 19:43:26:
YOU WROTE:
"The blue line is in room at listening position with no sub
The red line is 0-phase w/ 40hz crossover
The green line is 270-phase w/ 40hz crossover"RG
Did you try 180 degrees out of phase?The simple test is listening to a slow sinewave sweep from 20 to 100Hz. that lasts at least 15 seconds. You'll easily hear bass booms and nulls.
Your measurements should be made with sinewave test tones spaced no more than 1/6 octave apart, and even that would result in a rough measurements.
Your current measurements using some test tones 1/3 octave apart are almost certainly NOT capturing the actual SPL peaks and troughs that would be visible with sinewave tones for each frequency: (20Hz. 21Hz. 22Hz. ... 99Hz. 100Hz.)
The test tones should be steady sinewaves. Sinewave warble tones, pink noise and white noise will smooth the measurements by failing to excite room modes much (unlike bass guitar notes and kick drum notes)
YOU WROTE:
"All measurements have been corrected for the errors in the RatShack SPL meter."
RG
The Rat Shack meter needs no correction for the bass frequencies.Most of the so-called "error corrections" are in fact a simple conversion from SPL C-Weighting to a flat SPL weighting (unweighted SPL) that would apply to all sound meters.
Rat Shack meter samples are also not consistent enough to be sure corrections for someone else's Rat Shack meter would be useful for yours.
Most Rat Shack meters read a little low for bass frequencies, so you could add +1dB to all measurements under 100Hz. and most likely inprove the accuracy.
Measurements under 30Hz. are very likely to be too low, but those frequencies are hard to hear with music playing at typical volumes, so the low readings under 30Hz. may actually help the meter correlate better with what you hear/feel at 20Hz.
Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Edits: 01/14/09
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Follow Ups
- Forget the rough graph with too few data points -- listen (to a slow sinewave sweep or bass tone burst test tones) - Richard BassNut Greene 08:28:52 01/13/09 (6)
- I understand - and will try - VynylTap 09:23:57 01/13/09 (5)
- The Rat Shack Meter IS most useful for bass -- most people are clueless about "error corrections" - Richard BassNut Greene 09:11:53 01/14/09 (2)
- so really, the graph should look more like this... - VynylTap 14:29:39 01/14/09 (1)
- Yes. - Richard BassNut Greene 14:49:10 01/14/09 (0)
- Obviously you have a PC - johnvb 18:01:59 01/13/09 (1)
- Thanks - it's downloading as I type (nt) - VynylTap 06:29:10 01/15/09 (0)
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