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Discussion Starter · #1 ·
I'm getting lousy THD results. Has anyone used REW to test receiver THD? If so, how?
 

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What is your current test setup that is not working well:
Audio interface/soundcard?
Receiver Load?
Test Voltage?
 

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Discussion Starter · #3 ·
Setup is fine. Audio sounds fuzzy in the 400 to 800 Hz area even with another set of speakers. My hearing is no longer very good, but I would like to confirm that that's what it is. However, REW's THD results look awful too. I would like to check my Denon's THD and wonder if I can use the REW software somehow.
 

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I see. You are not able to get a clean test signal through your speakers? That is a problem. So it would then be unrelated to THD. That is, it applies to all measurements? Can you post a measurement? There may be a clue there.

Does a loopback cable measurement of your soundcard setup result in a flat SPL line? If not, some detail on your setup is still needed as it is impossible to make any guess with out any information other than you have provided.
 

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Discussion Starter · #5 ·
I would gladly send my data file, but not sure how to do an attachment on this site.
 

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Choose 'Advanced' for your reply and then the click the 'paper clip' in the message header. In the popup window find and upload the file. Close that window. Click the paper clip again for the option to then insert it into your post.
 

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I have no clear answer, but offer some thoughts that I hope will be helpful.

> You are using REW V5.00 and the latest version is REW v5.11. Many bugs and features have been addressed in the newer version. I don't think this a factor in your results, but an update is advised to be safe.

> The measurement info shows you have not specifically identified the soundcard in REW preferences so it is using the Windows default. That is no problem if the Windows default device is the correct one. If you are using a USB audio interface it is best to select it in 'preferences' so there is no confusion. If the internal soundcard is the Windows default it would be used instead. I don't think this is the issue either so it's more just FYI.

> The right input channel is selected as the measurement channel and that is fine.

What is attached to that channel though? There appears to be both a loopback signal and a speaker measurement. So possibly you have both a loopback cable and a mic both feeding the right channel input. The impulse response (IR) chart is the evidence for this. There is a clean IR at 0ms as is expected of loopback cable and then 15ms later what could possibly be a speaker response. 'Possibly' because it does not appear to be a good clean measurement of a speaker. There may still be problem even if a loopback cable is found and removed. Some info on your connections and what you measured here would clarify if this guesswork is founded.

> Confirm that any monitor switch on the soundcard is not active as will also cause problems. Again, I don't think this is the most likely cause, but I am not sure.
 

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Make sure no PC sound effects are turned on, looks a little like artificial room reverb has been added to that signal. Signal level also looks low.

REW V5.10 and later has THD plots.
 

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Discussion Starter · #11 ·
View attachment Home.mdat

View attachment SPL Cal..mdat

View attachment UCA202_cal..mdat

Thanks so much for your kind responses. I'm embarrassed to tell you that I had been using a wrong file. Haven't used the program for about a year and and was intrigued by the THD capability of the new version so just jumped in with both feet!

The attached files are what I should have used although I should probably do a new measurement. The results definitely indicate that the problem I'm having is my 80 year old ears! THD results are generally under 2% which most folks wouldn't notice. However, it is much higher at the low frequencies, probably due to the speaker's internal bass amplifier. System is a Denon 1705 and pair of Infinity Overture 1 bookshelf speakers. This is certainly no audiophile's delight, but makes a decent background system. (For me.)

Thanks again for your response and a great program. It's fun to use and VERY informative!
 
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