Blindfold us.
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Wanted: Proof of multiple subs and sub EQ
- Thread starter Ethan Winer
- Start date
Cover yourself from head to toe in hair gel Bob, works a treat!
Just be mindful not to abuse the power the 'cloak of gel' affords one.
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That's not practical, your just being silly now amirBlindfold us.
Fitzcaraldo215
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No, no. Ostriches have the right idea. He should blindfold himself.Blindfold us.
Ethan, did you see this post from March Audio? Multiple subs producing lower decay:
Post in thread 'Stereo Bass using subwoofers'
https://audiosciencereview.com/foru...tereo-bass-using-subwoofers.11034/post-311190
Post in thread 'Stereo Bass using subwoofers'
https://audiosciencereview.com/foru...tereo-bass-using-subwoofers.11034/post-311190
Thanks for the link. I had overlooked that post. For anyone who hasn't clicked on it yet, the post at the link shows the improvement in both the frequency and time domains in going incrementally from 1 sub to 4 subs.
He needs to show the y graph much lower in level BTW.
I think multiple subwoofers also should be measured at a wider area ideally.
I'll post some graphs later.
Keith_W
Master Contributor
Actually this has been bugging me for a while. How DO you measure bass decay in a room? If you take the measurement from one position, it won't give you a true picture - peaks take longer to decay, and nulls decay almost immediately. You can get REW to "normalise to peak at each frequency" which helps, but it's still not a true picture. Obviously you have to measure over a wider area, but how do you know if those positions are representative? And if you average them, you lose timing information, so you can't view waterfalls or spectrograms any more. @Bjorn I would love to hear your answer.
If you want to look at primarily time of ringing, a burst decay is good to use.
Example with untreated and half way treated.
For resonances, I generally prefer a waterfall. Considering bass is not only heard but also felt I normally measure at feet level, stomach level and at ear height and look at them separately.
It's good to look at the graph for the lower midrange here too. The most audible resonances are really above the sub frequencies, and is one of the reasons why DBA or multiple subwoofer approach doesn't reach the highest level alone. Not many have heard a really well treated room, so they don't know what they are missing out on. I focus more on mid bass, upper bass and low midrange if I have to make compromises in a design.
Example with untreated and half way treated.
For resonances, I generally prefer a waterfall. Considering bass is not only heard but also felt I normally measure at feet level, stomach level and at ear height and look at them separately.
It's good to look at the graph for the lower midrange here too. The most audible resonances are really above the sub frequencies, and is one of the reasons why DBA or multiple subwoofer approach doesn't reach the highest level alone. Not many have heard a really well treated room, so they don't know what they are missing out on. I focus more on mid bass, upper bass and low midrange if I have to make compromises in a design.
Keith_W
Master Contributor
Thanks. Where do you take your measurement from?
REW has a burst decay display, but it looks nothing like yours.
REW has a burst decay display, but it looks nothing like yours.
ernestcarl
Major Contributor
I haven't used this view mode much, and really don't understand why the "smearing" appears to steer over time to the right of the graph. Maybe it's just an artifact from the maths used to draw the graph? I dunno.
Sokel
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Go to the Waterfall tab, it's there, that's the Spectrogram you have here.
ernestcarl
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I sometimes forget the different graph window views can have same named "view modes". Smearing or decay also steers to the right when using the burst decay view mode of the waterfall plot.
Sokel
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Mine too, it must be the chosen view.
ernestcarl
Major Contributor
Bjorn's software plots a completely straight line... Which makes me suspect it's just an artifact of how it's drawn in REW.
I have two subs in my setup, which I run in mono to even the frequency response at the listening position. Here are some plots to show how these subs play separately and together. This was measured with REW at the listening position. I show decay plots, as I think they are slightly more informative than waterfalls.
Frequency response:
Sub1 Decay:
Sub2 Decay:
Sub1 + Sub2 Decay:
Look at the particularly nasty peak at about 45 Hz, which in fact is a degenerate resonance of two separate modes. As you can see, the two subs - which are playing the same signal - are able to bring down this peak.
Note that this is not the final response of my system. I’m using more DSP later in the signal chain to smooth things further. Here I just wanted to show the isolated effect of multiple subs.
Also note that I have verified that this works by listening to burst test tones, so it’s not just about visually appealing plots. The test tones were from this post by @KSTR:
www.audiosciencereview.com
Frequency response:
Sub1 Decay:
Sub2 Decay:
Sub1 + Sub2 Decay:
Look at the particularly nasty peak at about 45 Hz, which in fact is a degenerate resonance of two separate modes. As you can see, the two subs - which are playing the same signal - are able to bring down this peak.
Note that this is not the final response of my system. I’m using more DSP later in the signal chain to smooth things further. Here I just wanted to show the isolated effect of multiple subs.
Also note that I have verified that this works by listening to burst test tones, so it’s not just about visually appealing plots. The test tones were from this post by @KSTR:
Low- and Mid-Frequency Test Signals for Evaluation of Room Modes (and other things)
Hi, Recently, I promised I'll present my trusted test signals for evaluation of room modes, finding best positions for speakers and listener, check for distortion/rattling etc. This was a project I did 20 years ago before EQ'ing was commonplace, let alone full digital "room correction". An...
www.audiosciencereview.com
Sokel
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It could be.
We would only know if we could see Bjorn's parameters, filtering, etc.
ernestcarl
Major Contributor
Indeed, smoothing peaky in-room response seems to be one of the benefits of having multiple LF sources spread out.
Sokel
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It also could be normalized to peak, REW shows similar if the option is on.
I think there are less differences between your plot and Bjorn's second plot than you think. His plot was from ~10/20 Hz to ~120 Hz. vertical scale range is 60 dB, and time scale range is 60 periods.
Yours is 23 - 600 Hz, color scale range 40 dB, and time scale 32 periods.
I think the skewing of the plot to the right is because the time scale is in periods. 30 periods at 600 Hz is the same amount of time as 3 periods at 60 Hz.
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