Trace Arithmetic Issue

[eta314]

I am new to REW so I'm sure I am doing something wrong but when I divide my left channel data by a target curve there is no result.

 

[John Mulcahy]

Best attach the mdat file with the measurement and the target. Are you sure the result isn't just above or below the graph limits?

 

[eta314]

Here are the files. Thanks.

 

[eta314]

Here is the .mdat.

 

[John Mulcahy]

The mdat is probably too large to upload, just save the individual measurement you are using in the divide and upload that.

 

[eta314]

Apparently, all I have are mdat files that are about 32mb in size. Not sure how to save the individual measurement. I used |A|/|B| instead of A/B and that worked. What is the difference? Thanks for your help.

 

[John Mulcahy]

Not sure how to save the individual measurement.

Use File - Save measurement with the measurement you want to save selected or click this button:

I used |A|/|B| instead of A/B and that worked. What is the difference?

Magnitude division instead of vector (magnitude + phase) division.

 

[eta314]

I saved the measurement as you indicated but it is still a large mdat file. I click attach files and it goes to 100% but the file is not there. Sorry for all these problems.

 

[eta314]

 

[John Mulcahy]

How large is the file? You can try zipping it and attaching the zip. The Drive link doesn't appear to be public.

 

[eta314]

 

[John Mulcahy]

Your files are huge because you have used an extremely long sweep (4M) and have set the Analysis preferences to keep the full IR (all 174.6 seconds of it). Both are completely unnecessary and will slow the application down considerably. 256k sweeps are plenty long enough for acoustic measurements in domestically sized spaces and truncating the IR after 1.7 s is fine as long as you aren't making measurements in a cathedral.

 

[eta314]

It is about 32mb. i tried zipping but it was reduced by only 3mb. I tried sending a public Drive link.

 

[eta314]

Ok. I was following Serkan Gür's tutorial and that length was recommended. I will try shorter sweeps. Do you think that will solve my trace arithmetic problems?

 

[John Mulcahy]

The main problem is using the "Keep full IR" setting in combination with a very long sweep. Of your 174.6 second IR 174.0 seconds is noise floor, so not terribly efficient. Use the default "Truncate IR after 1.7 s" setting. It doesn't hurt to use a 4M sweep but it is just a huge waste of time in all but a very, very few specialist cases.

The arithmetic problem was caused by an internal protection to prevent the result getting too long and risking out of memory failures, that protection was kicking in when dividing 4M IRs. I have made a change to accept that case for the next build, but all should work OK using a sensible IR length.

Your target level gets very low at the lowest frequencies due to the high pass shape, that causes heavy boosting of LF noise when dividing. To deal with that use regularisation, even 0.1% will work.

 

[eta314]

Thank you so much for spending time on this issue. I will use your suggestions.