Cool Dude Ted

REW software

Recommended Posts

9 minutes ago, PuritéAudio said:

Are you hearing the test tone through the loudspeakers?

Turn up the volume until REW goes green would be my advice, you have set mic as your input and your dac as output?

Keith

 Current setup (revised from day 1);

Analogue mic into mic jack on laptop.

Cable connected from headphone out on laptop to amp; RCA in (DAC now taken out of the loop).

Test tone being heard through speakers OK. Volume level on amp adjusted so that when test tone plays through speakers, the SPL meter on my IPAD shows around 75DB.

Despite this, when hitting “check levels” under “Measurement” tab, REW reports “level is low -43Db”, which I took to mean that the mic was not recording the 75DB signal from the speakers at a sufficiently high enough input level.

Stuart

Share this post


Link to post
Share on other sites
4 minutes ago, MartinC said:

I'll have more time for detailed replies over the weekend but I'll just say you shouldn't feel you're doing badly at all. Pretty much everyone goes through a learning phase as you are. As I hope my posts earlier in this thread suggested I don't think anyone should expect to get a somehow perfect result first time. I certainly didn't.

I'll also just say that so far I'm trying to work out if you actually have the issue with two bass peaks that you think you might. 

Martin

Thank you so much for all your help.

Stuart

Share this post


Link to post
Share on other sites
2 hours ago, Cool Dude Ted said:

 Current setup (revised from day 1);

Analogue mic into mic jack on laptop.

Cable connected from headphone out on laptop to amp; RCA in (DAC now taken out of the loop).

Test tone being heard through speakers OK. Volume level on amp adjusted so that when test tone plays through speakers, the SPL meter on my IPAD shows around 75DB.

Despite this, when hitting “check levels” under “Measurement” tab, REW reports “level is low -43Db”, which I took to mean that the mic was not recording the 75DB signal from the speakers at a sufficiently high enough input level.

Stuart

Bit busy at the moment but will reply in detail later when I have Rew open in front of me.

Firstly don’t just wind up the volume on your amp until the recording level is correct; this could mean that you are running your equipment at too high a level in your room, both for your speakers and your ears.

So, first thing to do is get the volume correct in your room at 75 dB (or thereabouts) using check levels - full range at bottom of REW preferences. Unless you are doing this regularly it is very difficult to judge volume by ear and without an SPL meter, an iPad app should be adequate for the job, which app are you using.

The second thing is to adjust the sensitivity of the mic in settings. Your mic may not be sensitive enough even with input/mic setting at max. If so don’t compensate by winding the volume in your amp up. Many, many, years ago, when playing with test tones I blew a pair of tweeters; I won’t make that mistake again!

I wouldn’t worry about timing loops just yet and if you do at sometime down the line a umik mic will be invaluable.

A umik mic makes life so much easier but that depends on your means and how much use you might get from it. They do seem to be in demand second-hand, so I guess it would be possible to sell on after use.

Don’t worry about taking two steps forward and one back; it isn’t easy and anyone who claims it is has forgotten their time learning, is a genius or doesn’t know what they are talking about!

Pleasure to try and help by the way.

  • Upvote 1

Share this post


Link to post
Share on other sites

Just catching up on this thread...

The first thing I would suggest you do it to take three measurements, straight after each other without changing anything and check that they're all the same. I'm saying this to just rule out major problems with your source/microphone approach at present.

Don't obsess about the 75 dB figure. So long as it's not really loud or really quiet you'll be fine. Ignore the absolute numbers in REW or any warnings it may give and go by your ears. The numbers in REW are only meaningful with a calibration.      

22 hours ago, Cool Dude Ted said:

4 as an aside, but connected issue - even before starting out on this journey, I knew I have never been able to grasp the “Whole Db Thing”. I have always been confused by the seemingly interchangeability (not sure if this is the right word) between plus and minus decibel figures. This has been truly  exacerbated today by the SPL meter on my IPad. The graph, plotted frequency on the X axis and Db on the Y axis, shows sound level as a minus figure on the axis and a higher volume level is represented by a decrease in the negative value. I.E -40Db is louder than -60Db. I still cannot get my head round why these figures are minus. Against this, the figure for overall SPL - showing as DB-A - is a positive figure. If anyone knows of an idiots guide/video to help me sort out this confusion, then I would be delighted to hear. Of course, this is not specific to REW.

First up, whilst this will make no practical difference, note it's 'dB' not 'Db' :)

The key point with all dB scales is that they are relative rather than absolute. Whether a dB value is positive or negative depends if it is above or below a reference value. So -40 dB is louder than -60 dB in the same way -40°C is warmer than -60°C.

When you're comparing different dB scales they'll have different reference values which is why they'll vary in how much they'll tend to be positive or negative. SPLs are relative to a very quiet sound at approximately the threshold of hearing and so all values loud enough to be hear are positive. By contrast, audio signal levels such as output by REW are typically expressed relative to the absolute maximum level possible, and so typical levels will all be negative as they will be below this level.

Share this post


Link to post
Share on other sites
37 minutes ago, MartinC said:

Just catching up on this thread...

The first thing I would suggest you do it to take three measurements, straight after each other without changing anything and check that they're all the same. I'm saying this to just rule out major problems with your source/microphone approach at present.

Don't obsess about the 75 dB figure. So long as it's not really loud or really quiet you'll be fine. Ignore the absolute numbers in REW or any warnings it may give and go by your ears. The numbers in REW are only meaningful with a calibration.      

First up, whilst this will make no practical difference, note it's 'dB' not 'Db' :)

The key point with all dB scales is that they are relative rather than absolute. Whether a dB value is positive or negative depends if it is above or below a reference value. So -40 dB is louder than -60 dB in the same way -40°C is warmer than -60°C.

When you're comparing different dB scales they'll have different reference values which is why they'll vary in how much they'll tend to be positive or negative. SPLs are relative to a very quiet sound at approximately the threshold of hearing and so all values loud enough to be hear are positive. By contrast, audio signal levels such as output by REW are typically expressed relative to the absolute maximum level possible, and so typical levels will all be negative as they will be below this level.

Thanks Martin

1 I think I now understand a bit more about “75dB” and feel reasonably confident that I know how to set my amp’s volume to achieve this sort of figure. I’ll do what you say with three measurements over the weekend.

2 Thanks for the info about dB. So there is no way of ‘converting’ SPLs to dBFS - and more importantly, I should just move on and ignore what is a non-issue? Basically it is what it is and I should stop over thinking?

Final point - and this is still something I can’t get clear in my head - I am still unable to increase the input level of my analogue mic to a point where REW doesn’t report it as “level is low”. The help screen says I should be between -12 and -24 dB? but I am way off (about -40 dB). I simply don’t understand the implications (on the results) of having a mic which is inputting at too low a level.

Incidentally, I am actively investigating the purchase of a USB mic now.

Thank you.

Stuart

Share this post


Link to post
Share on other sites
7 minutes ago, Cool Dude Ted said:

2 Thanks for the info about dB. So there is no way of ‘converting’ SPLs to dBFS

Not in a general sense. What SPL you get in a room for a particular signal level (dBFS) will depend on your amp volume/gain setting, your speakers and your room.

Quote

Final point - and this is still something I can’t get clear in my head - I am still unable to increase the input level of my analogue mic to a point where REW doesn’t report it as “level is low”. The help screen says I should be between -12 and -24 dB? but I am way off (about -40 dB). I simply don’t understand the implications (on the results) of having a mic which is inputting at too low a level.

I'm not sure about this but the point of my proposed repeatability test was to try to assess whether you had a problem or not in a practical way. You could also use the real-time analyser (RTA) to see what the noise level looked like and compare it to your measured signal levels. The issue of low signal level is essentially one of poor signal-to-noise ratio.

Edited by MartinC

Share this post


Link to post
Share on other sites
34 minutes ago, MartinC said:

Not in a general sense. What SPL you get in a room for a particular signal level (dBFS) will depend on your amp volume/gain setting, your speakers and your room.

I'm not sure about this but the point of my proposed repeatability test was to try to assess whether you had a problem or not in a practical way. You could also use the real-time analyser (RTA) to see what the noise level looked like and compare it to your measured signal levels. The issue of low signal level is essentially one of poor signal-to-noise ratio.

Thank you 

Share this post


Link to post
Share on other sites
On 13/01/2021 at 21:44, Cool Dude Ted said:

I took a deep breath and had another go this afternoon. I am not saying that it was a success but I at least arrived at a series of settings which I have been able to input to the PEQ in Moode. I have input 8 settings between 40 Hz and 200 Hz. Have listened for a while but so very difficult to assess if “better” than what went before without A/B listening which I cannot do at present.

If you have strong modes (peaks) in the bass and sub-bass then the EQ should be pretty obvious with kick drums and plucked double-bass.

Edited by tuga

Share this post


Link to post
Share on other sites
On 13/01/2021 at 21:44, Cool Dude Ted said:

1) if I increase ‘smoothing’ of the graphs then the number of frequency settings/changes/reduces. I had to settle on 1/12 smoothing to get a sensible number of parameters

I only EQ below 200Hz and generate the auto filters on a window with 1/12 smoothing and the following settings:

Equiliser:

Generic

Target Settings:

Target - None

Room Curve - LF 200Hz/20Hz/+1dB

Target Level - depends on the measurement level and the curve

Filter Tasks:

20 to 200Hz

Individual max boost - 6dB

Overall max boost - 6dB

Flatness target - 3dB

I allow narrow filters below 200Hz because I use MMM.

---

Click "Match response to target"

On 13/01/2021 at 21:44, Cool Dude Ted said:

2) I am struggling with understanding the reference to ‘target Dbs’ when measuring. 75 DB seems to be the default but I don’t understand why. This could simply be me struggling with the whole concept of decibels rather than being REW specific.

You need to perform the measurement at a sufficient SPL so that the signal is around 35dB above the noise floor in your room. I think that this is where the 75dB level cmoes from (when using calibration).

Perform your measurement then adjust the Target Level of your target curve to fit the measured level.

On 13/01/2021 at 21:44, Cool Dude Ted said:

4) some of the suggested EQ settings are extreme to say the least e.g. a Q of 32 and -50Db. The PEQ within Moode only permits a max Q of 8

How much smoothing are you applying? 1/24 or 1/12 would be

Did you check "Allow narrow filters below 200Hz"?

In my room that gives me a highest attenuation of -7.4dB and a max Q of 5.

On 13/01/2021 at 21:44, Cool Dude Ted said:

5) Moode doesn’t seem to permit the input of separate settings for L & R speakers. Have I missed something here?

If your room is symmetrical and your speakers are symmetrically positioned then a "global" EQ should be fine.

Share this post


Link to post
Share on other sites
On 14/01/2021 at 15:10, Cool Dude Ted said:

Thanks Martin.

the graphs below are with my amp volume control in the "9am" position and then "10am" position. No smoothing.

9am. When I click "set target level" it automatically changes to 77.8Db. This output produces 9 EQ filter settings in the 20-200Hz range. These range from Q settings of 2.1 to 17.1. Interestingly, there are 3 filters at 92.2, 92.3 and 93 Hz with gains ranging from minus 24.2 to plus 18. These are "crazy" figures and impossible to apply.

10am. Click "set target level" button produces a figure of 84.8Db. This output produces 9 Eq filters with Q values ranging from 4.1 to 29.2. With gains from plus 15Db to minus 19.5. The nonsense in the 92 and 93 Hz range does not appear.

Literally, the only difference between these two graphs is that one was produced with a slightly different volume setting on the amp and I am clueless as to why there should be such an enormous variation in the Eq filters suggested. That said, the overall shape of the two graphs is very similar.

I remain grateful to you for any input/clarification but I cannot expect you to keep giving your time to this issue.

My overriding question now is to what extent, if at all, any issues I am seeing would be overcome by me acquiring a calibrated mic without me needing to understand anything more of the intricacies of REW than I do (or don't) now.

Regards

Stuart

9am no smoothing.jpg

10am no smoothing.jpg

Can you upload your measurement files, zipped?

I can generate an EQ filter suggestion if you wish.

.

Also, your vertical scale is too wide, for viewing puposes it should be nor more than 60dB-wide. 50dB is the standard for speaker measurements.

And it is important to view the whole spectrum 20-20,000Hz when EQ'ing to get an idea of the overall balance. I usually alternate between 1/24 and Psychacoustic smoothing to get a better idea of what is happening.

Share this post


Link to post
Share on other sites
On 14/01/2021 at 15:19, Cool Dude Ted said:

I do have a camera tripod which I could somehow attach the mic to if you think that would be a better solution.

If you don't have a mic clip but your tripod uses a pan-and-tilt head then you can strap the mic to the lever with a rubber band.

Share this post


Link to post
Share on other sites
On 15/01/2021 at 11:37, Cool Dude Ted said:

 Current setup (revised from day 1);

Analogue mic into mic jack on laptop.

Cable connected from headphone out on laptop to amp; RCA in (DAC now taken out of the loop).

Test tone being heard through speakers OK. Volume level on amp adjusted so that when test tone plays through speakers, the SPL meter on my IPAD shows around 75DB.

Despite this, when hitting “check levels” under “Measurement” tab, REW reports “level is low -43Db”, which I took to mean that the mic was not recording the 75DB signal from the speakers at a sufficiently high enough input level.

Stuart

I believe that REW is trying to get the signal to a suficient level above the room noise floor.

Are you using the Sub signal or Speaker calibration signal? (you should use the latter because your speakers won't be producing much sound level below 60-70Hz)

Share this post


Link to post
Share on other sites

@tuga

Thank you for all of your helpful comments.

Having spent another 3/4 hours with this today, I am very rapidly approaching the point where I have to say enough is enough and concentrate on others things which are not getting done in the house. Sad as that is, it’s becoming reality.

Today is a case in point. Based on MartinC’s helpful suggestions, I have taken (not 3) but 5 separate measurements within about 2 minutes of each other. The mic was tripod mounted. I then applied 1/6 smoothing (is this too much???), then produced EQ filters. The first 4 readings were close to each other, the 5th was out with it’s suggested filters even though the graph shape looked the same.

When I averaged those 4 readings, I ended up with;

116 Hz  +4.3 dB gain  3.2Q

160 Hz  -8.5 dB  gain  2.0Q

187 Hz  +6.9 dB gain  3.0Q

320 Hz  -9.1 dB gain  2.5Q

434 Hz  -4.8 dB gain  5.0Q

and if I’m honest, I can see a correlation between the -plus and minus gains and the peaks and troughs on the graph.

Earlier readings taken this morning were wildly different from the above but I have no idea why.

So although I think I’m at a point where I’ll try the above figures in my PEQ, I have very little confidence in the consistency of any figures I’m able to produce.

I remain convinced that part of the problem is the fact that I am using an old analogue mic plugged straight into the laptop (no mic amp).

Thnk you again for your kind offer to produce EQ filters.

Until today, I thought that my issues involved standing waves around the 45Hz level. The above figures now throw that into severe doubt, if they are correct.

Kind regards

Stuart

Edited by Cool Dude Ted
Spelling

Share this post


Link to post
Share on other sites

For my check you didn't need to do anything with filters. Just directly compare the 5 measurements. It would have taken minutes. 

Can you post the SPL graph showing the 5 measurements with let's say 1/48 smoothing?

Edited by MartinC

Share this post


Link to post
Share on other sites
38 minutes ago, Cool Dude Ted said:

@tuga

Thank you for all of your helpful comments.

Having spent another 3/4 hours with this today, I am very rapidly approaching the point where I have to say enough is enough and concentrate on others things which are not getting done in the house. Sad as that is, it’s becoming reality.

Today is a case in point. Based on MartinC’s helpful suggestions, I have taken (not 3) but 5 separate measurements within about 2 minutes of each other. The mic was tripod mounted. I then applied 1/6 smoothing (is this too much???), then produced EQ filters. The first 4 readings were close to each other, the 5th was out with it’s suggested filters even though the graph shape looked the same.

When I averaged those 4 readings, I ended up with;

116 Hz  +4.3 dB gain  3.2Q

160 Hz  -8.5 dB  gain  2.0Q

187 Hz  +6.9 dB gain  3.0Q

320 Hz  -9.1 dB gain  2.5Q

434 Hz  -4.8 dB gain  5.0Q

and if I’m honest, I can see a correlation between the -plus and minus gains and the peaks and troughs on the graph.

Earlier readings taken this morning were wildly different from the above but I have no idea why.

So although I think I’m at a point where I’ll try the above figures in my PEQ, I have very little confidence in the consistency of any figures I’m able to produce.

I remain convinced that part of the problem is the fact that I am using an old analogue mic plugged straight into the laptop (no mic amp).

Thnk you again for your kind offer to produce EQ filters.

Until today, I thought that my issues involved standing waves around the 45Hz level. The above figures now throw that into severe doubt, if they are correct.

Kind regards

Stuart

Hi Stuart,

I wouldn't use 1/6. Also, I would take care not to measure over an area wider than 30-40cm.

You can also try testing standing waves using these test tones or those found on youtube and your iPad's SPL meter.

Best,

Ricardo

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.