Old 04-12-2021, 10:44 AM   #81
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I'm surprised clicking "Generate" for waterfall doesn't work when it does for Spectrogram. One thing you might do is click limits (top right) and set the range to 20-20kHz just so you have the full range - most use just for low end but I do like seeing it all.
I'll try doing a full spectrum for each set of speakers, or does that even matter? IOW, both graphs seem to show the same spike.

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You could also go to the "All SPL" tab, uncheck everything but the result you want to look at, controls and smoothing to 1/6 octave. The smoothing is just to get it closer to the average it sounds like to the ears. This graph doesn't take time into account FYI like Spectro and Waterfall do.

That one around 160 hz is ringing for 700 ms FYI.
So I'm guessing 160hz a frequency that's being reinforced by standing waves, and could be tamed with some corner and edge absorption? In the next few weeks when I get my new carpet paid off, I plan to put up some kind of bass traps in the room.

I'll mess with REW some more and see what I can get from it.

Thanks again for all the help and insight.
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Old 04-12-2021, 11:16 AM   #82
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You should only shoot 1 speaker at a time. [Left, then Right]
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Old 04-12-2021, 11:20 AM   #83
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You should only shoot 1 speaker at a time. [Left, then Right]
Woops, too late I finally got it to generate a waterfall with a four pass 20-20000 sweep.
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Old 04-12-2021, 11:33 AM   #84
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Wow, that 160 Hz peak is seriously long. Maybe you could verify it isn't some sort of ambient noise, like HVAC or something. Though I'd expect it to be flatter along the ridge if it were.

The huge dip around 70 Hz suggests cancellation due to a room reflection null node.

For the size & shape of the room it's a good starting point.
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Old 04-12-2021, 12:02 PM   #85
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Woops, too late I finally got it to generate a waterfall with a four pass 20-20000 sweep. The waterfall thing is acting wonky, but I finally got it to create this one.
There are important reasons to shoot only 1 speaker at a time.
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Old 04-12-2021, 12:04 PM   #86
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Wow, that 160 Hz peak is seriously long. Maybe you could verify it isn't some sort of ambient noise, like HVAC or something. Though I'd expect it to be flatter along the ridge if it were.
There was no HVAC or anything else going on and the mic was about 42" from the monitors.

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The huge dip around 70 Hz suggests cancellation due to a room reflection null node.

For the size & shape of the room it's a good starting point.
Now that I sort of know what's going on, I can hear the spots where reinforcement or cancellation is happening. On the room calc page, with my room's dimensions plugged in, I could click some of the low freq problem areas it predicted, and while the tones were playing, I walked the room where I could hear it plain as day.

I gotta get my carpet paid off, but in the next few weeks I will be putting some kind of bass traps in this room and then I'll shoot it again.
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Old 04-12-2021, 12:46 PM   #87
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I would smooth that waterfall down to 1/6 or 1/12th (Controls... on top right). That's a little closer to the way your ears hear it as a whole. You can always put it back but it smooths out some of the unnecessary data noise.

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So I'm guessing 160hz a frequency that's being reinforced by standing waves, and could be tamed with some corner and edge absorption?
If the mode calculator agrees then yes, same thing for dips which are just the inverse aka cancellations. You can usually see those well because you have the main, then another at its harmonic (double), then another at the next harmonic. Meaning, fix one, fix several in one go. Here's an example...

The yellow arrows are likely all related/multiples that agree with the mode calculator and my wall distances, same for the blue. On a side note the orange arrow which sort of shows a curving from 73Hz to 79Hz, that is an artifact of the L/R walls (73Hz) and the F/B walls (79Hz) - I believe it has that twist/curve due to one decaying a little longer than the other.

The main thing I'm getting at is if you have the dimensions et al, you can decipher a lot of information out of the waterfall data and it will tell you where you need the absorption with a lot less guessing - minus any complete misconceptions of my own here.

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Old 04-12-2021, 12:59 PM   #88
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Excellent advice, Karbo
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Old 04-12-2021, 01:20 PM   #89
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I would smooth that waterfall down to 1/6 or 1/12th (Controls... on top right). That's a little closer to the way your ears hear it as a whole. You can always put it back but it smooths out some of the unnecessary data noise.



If the mode calculator agrees then yes, same thing for dips which are just the inverse aka cancellations. You can usually see those well because you have the main, then another at its harmonic (double), then another at the next harmonic. Meaning, fix one, fix several in one go. Here's an example...

The yellow arrows are likely all related/multiples that agree with the mode calculator and my wall distances, same for the blue. On a side note the orange arrow which sort of shows a curving from 73Hz to 79Hz, that is an artifact of the L/R walls (73Hz) and the F/B walls (79Hz) - I believe it has that twist/curve due to one decaying a little longer than the other.

The main thing I'm getting at is if you have the dimensions et al, you can decipher a lot of information out of the waterfall data and it will tell you where you need the absorption with a lot less guessing - minus any complete misconceptions of my own here.
I just started to understand the frequency doubling thing when playing with that room calc site. I'm definitely getting what's going on now. I guess one question would be, can you go too far?

I'm thinking I will get a pack of seven 2'x 4'x 3" Rockwool panels, which is like $180 and sticking them on all the walls, especially in any of the corners I can fit into. That will be like 65 square feet of 3" thick dense 8# Rockwool.
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Old 04-12-2021, 02:12 PM   #90
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I guess one question would be, can you go too far?
Kind of yes...

Assuming your final response is reasonably flat, you can eventually suck all the life out of the room (or end up not reasonably flat and suck out high end disproportionately). In my other house which had a smaller room than the one I'm in now, I crammed 22, yes 22 2'x4' 4", 6" & 8" thick panels in it. When someone entered the room, it was mildly uncomfortable because when you talk, you hear your voice crawling around your face to get to your ears because almost none is reflecting in the room.

Most will advise that this is a terrible idea and it's not the best. My take on it is this, I only have the room I have and my only choice in order to control the low end, was to suck it all out across the board, then add the "room" back in Reaper with an ambient reverb. Believe it or not that worked quite well. Another benefit is it would allow me to mic an amp 6' away and sound like it's close mic'd minus proximity effect. I made some fine recordings and mixes in that room IMHO.

I'm not extolling ^that, just saying yes, you can go too far and suck 90% of the reflections out of the room - when in small rooms like some of us have, we may bend the rules some or get creative to work around things regardless.

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I'm thinking I will get a pack of seven 2'x 4'x 3" Rockwool panels, which is like $180 and sticking them on all the walls, especially in any of the corners I can fit into. That will be like 65 square feet of 3" thick dense 8# Rockwool.
I think you can figure out how many of dB @ some frequency the above rockwool will absorb (dissipate into heat). There may be a datasheet already with a response curve. Just mentioning, you can combine that with the REW info you already have to get an idea of how much reduction in said frequency etc. per ~n thickness of rockwool. Generally, in rooms less than 1500 cubic feet, it takes more than we wish it did.
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Old 04-12-2021, 02:47 PM   #91
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I guess one question would be, can you go too far?
Yes. Especially at 128 kg/m3 and a waterfall plot that's not really correct because you have two speakers (and a sub?) playing.

Do a left waterfall and a right one. Leave the sub out of it. Compare the two and try to "see" the room.
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Old 04-12-2021, 08:24 PM   #92
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Kind of yes...

Assuming your final response is reasonably flat, you can eventually suck all the life out of the room (or end up not reasonably flat and suck out high end disproportionately). In my other house which had a smaller room than the one I'm in now, I crammed 22, yes 22 2'x4' 4", 6" & 8" thick panels in it. When someone entered the room, it was mildly uncomfortable because when you talk, you hear your voice crawling around your face to get to your ears because almost none is reflecting in the room.

Most will advise that this is a terrible idea and it's not the best. My take on it is this, I only have the room I have and my only choice in order to control the low end, was to suck it all out across the board, then add the "room" back in Reaper with an ambient reverb. Believe it or not that worked quite well. Another benefit is it would allow me to mic an amp 6' away and sound like it's close mic'd minus proximity effect. I made some fine recordings and mixes in that room IMHO.
It blows my mind how I have been totally aware of flutter that I can hear, and oblivious to flutter that only shows up as phase cancellation or reinforcement, but now that I'm aware of it can both hear it on test tones in the room, and visualize it in my mind. I totally dig the getting back from the speaker thing, and am going to have to play with that, since my Gretsch speaker cab is in the closet with a mic currently at the edge of the speaker.

The little 20w Orange amp I power it with has a single knob tone that rolls off lows when you turn it towards treble, and it's bumped a bit that way prolly due to the mic being right in the speaker.

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I'm not extolling ^that, just saying yes, you can go too far and suck 90% of the reflections out of the room - when in small rooms like some of us have, we may bend the rules some or get creative to work around things regardless.
I do want to keep my room fun to play in. I just played my acoustic drums along with the entire Pretzel Logic album, and the sound in the room from the drums, with the JBLs at playing drums level, sounds clean and clear. Not blasting. I play drums pretty quiet as far as a lot of drummers go, but also not wimpy on the stuff that needs accentuation.

Anyway, I know I have a problem with fluttery bass that I guess I'm going to try some stuff and see what happens. I'd love to buy a couple traps, hang 'em up and get back to music, but I think it's going to unfortunately be more involved to get my room to a more happy place.

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I think you can figure out how many of dB @ some frequency the above rockwool will absorb (dissipate into heat). There may be a datasheet already with a response curve. Just mentioning, you can combine that with the REW info you already have to get an idea of how much reduction in said frequency etc. per ~n thickness of rockwool. Generally, in rooms less than 1500 cubic feet, it takes more than we wish it did.
In the next few weeks I think I'm just going to get some Rockwool panels, temporarily hang a couple of them and shoot the room, right before and right after. Then, based on what I see either commit or move those panels. Then do the next pair the same way, and so on. I can figure out how to make them look nice once I figger out where they need to go.
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Old 04-12-2021, 08:32 PM   #93
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Yes. Especially at 128 kg/m3 and a waterfall plot that's not really correct because you have two speakers (and a sub?) playing.

Do a left waterfall and a right one. Leave the sub out of it. Compare the two and try to "see" the room.
I did not use a sub on the waterfall plot, as that was done with my larger JBLs, but it was both speakers and I also realized I had my chair where reflections from it could have spoiled the results.

I'm going to have to wait until my wife is out of the house again to do more sweeps, but I'll soon get a plot for each speaker independently and without a chair behind the mic. Just the fact that I understand what is happening, and what might fix it is a giant step in the right direction for me, so I appreciate all you guys taking time for me to "get it".
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Old 04-13-2021, 06:59 AM   #94
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Great!

Take time to let it all sink in and experiment. Move the speaker, move the mic a bit etc.

Once you know how to read a graph, it becomes very simple, really.
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Old 04-13-2021, 09:47 AM   #95
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Great!

Take time to let it all sink in and experiment. Move the speaker, move the mic a bit etc.

Once you know how to read a graph, it becomes very simple, really.
Okay, I think I got a couple plots that might really represent the room. I pulled my chair totally out and put the mic stand where the chair was, and I told REW to smooth at 1/6th. Then I shot each speaker separately and no subwoofer. Here's what I'm getting now.

Also note I am using my vocal mic which is a Rode NT1 (not NT1a) and I don't have a profile for it.

Left side:


Right side:
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Old 04-13-2021, 06:09 PM   #96
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Hi Glennbo.

Not to veer off course but are you still liking that Behringer euphoria interface and the ada8200? I was thinking about buying the same setup because I really don't need a ton of bells and whistles in an interface. I'm hoping to run my new system at 64 samples at 48k.
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Old 04-13-2021, 07:03 PM   #97
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Hi Glennbo.

Not to veer off course but are you still liking that Behringer euphoria interface and the ada8200? I was thinking about buying the same setup because I really don't need a ton of bells and whistles in an interface. I'm hoping to run my new system at 64 samples at 48k.
I've been extremely happy with the UMC1820 since buying it in June 2019, but after recently adding three new Sennheiser drum mics I ran it out of inputs so I added the ADA8200.

I've only had the ADA8200 a few days, but I'm already using it for all my basses with a modeling preamp and plugging my guitars in direct to play around with Guitar Rig and ToneLib. Before the ADA8200 I was having to swap cables around to plug in those things.

I run the UMC1820 48/24 @ 64 samples from my first tracks to the final master, and never ever change it. I do avoid high latency plugins though.
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Old 04-13-2021, 08:39 PM   #98
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Okay, I think I got a couple plots that might really represent the room. I pulled my chair totally out and put the mic stand where the chair was, and I told REW to smooth at 1/6th. Then I shot each speaker separately and no subwoofer. Here's what I'm getting now.

Also note I am using my vocal mic which is a Rode NT1 (not NT1a) and I don't have a profile for it.
Glennbo ... I probably don't need to tell you this ...

But using a 'vocal' mic [likely Cardiod], is NOT the right type of microphone to use to do Room analysis. [regardless if you get a Calibration file for it].

Room analysis mics are OMNI-directional. And they too need a CAL file.

A decent Cal mic [with file] runs about $80. I just had to purchase another one, as my old Cal file is gone.

And believe me ... that CAL file is very important.

To ease the pain ... the CAL mic can also be used for Recording ... even a 'Room' mic
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Old 04-13-2021, 09:05 PM   #99
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Glennbo ... I probably don't need to tell you this ...

But using a 'vocal' mic [likely Cardiod], is NOT the right type of microphone to use to do Room analysis. [regardless if you get a Calibration file for it].

Room analysis mics are OMNI-directional. And they too need a CAL file.

A decent Cal mic [with file] runs about $80. I just had to purchase another one, as my old Cal file is gone.

And believe me ... that CAL file is very important.

To ease the pain ... the CAL mic can also be used for Recording ... even a 'Room' mic
Thanks RJ, yeah I know the mic I used isn't really a calibration worthy mic, and I'll use that as my excuse now for the plots I posted.

At some point I plan to get a mic for room calibration, but I'll more than likely get or build some bass traps before I get a calibration mic. Now that I am understanding and hearing the effects of low end flutter, addressing that will be my main focus.

After I get some bass traps up, I'll get a calibration mic and maybe make some adjustments to all the panels in the room.
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Old 04-14-2021, 12:08 PM   #100
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That's the spirit!

Notice the differences between try 1 and try 2?

How the 160 Hz turned wider?

When you buy a mic, think about the Umik. I just gave away my fourth one to a friend in need who will go insane if he doesn't find anything to do.

I just hope he catches on as fast as you do.
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Old 04-14-2021, 12:51 PM   #101
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That's the spirit!

Notice the differences between try 1 and try 2?

How the 160 Hz turned wider?
Definitely. I also figured out how to put the graph a little more straight on since doing those last plots, where I can see the gaps better.

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When you buy a mic, think about the Umik. I just gave away my fourth one to a friend in need who will go insane if he doesn't find anything to do.
I see those for around $100, which is doable. Do they only make the USB version? Someone had mentioned that they use their calibration mic as a room mic too, but I would only be able to do that if it were XLR and going through my audio interface with the other drum mics.

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I just hope he catches on as fast as you do.
Hehe, it only took me 40 years from building my first garage studio till now to get it. I've always understood the flutter you can hear. Clap my hands, there it is. Put up a bunch of studio foam, now it's gone.

It never occurred to me that low frequency subsonic flutter was still happening, because clapping hands in the room doesn't expose it. Now I just need to figure out what the best placement, size and shape will work in my room.
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Old 04-14-2021, 01:40 PM   #102
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I've been extremely happy with the UMC1820 since buying it in June 2019, but after recently adding three new Sennheiser drum mics I ran it out of inputs so I added the ADA8200.

I've only had the ADA8200 a few days, but I'm already using it for all my basses with a modeling preamp and plugging my guitars in direct to play around with Guitar Rig and ToneLib. Before the ADA8200 I was having to swap cables around to plug in those things.

I run the UMC1820 48/24 @ 64 samples from my first tracks to the final master, and never ever change it. I do avoid high latency plugins though.

Awesome.
Thank you.
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