Now you get to hear distortion, not just see graphs of harmonic and/or intermodulation distortion.
For those who haven't yet used REW, I'm attached the residuals of these 4" mid-woofers for direct download and listen in your favorite app.
Dayton Audio DA115 vs Wavecor WF120BD04 in free air
playing Queen- Another One Bites the Dust.
In an ideal world- they would be both SILENT (ie. speaker output - original audio = NOTHING)
Come have a listen what your speaker add to the original audio.
Warning: You may not like what you are about to learn
For those who haven't yet used REW, I'm attached the residuals of these 4" mid-woofers for direct download and listen in your favorite app.
Dayton Audio DA115 vs Wavecor WF120BD04 in free air
playing Queen- Another One Bites the Dust.
In an ideal world- they would be both SILENT (ie. speaker output - original audio = NOTHING)
Come have a listen what your speaker add to the original audio.
Warning: You may not like what you are about to learn
both files originally 32bit / 96Khz but too large to diyAudio to handle. converted to -> 16bit / 48Khz
Member
Joined 2003
At least for simple filters, the drop down options on the FSAF measurement window should be fairly straight forward.
Reviewing @JanRSmit measurement, great to see that you're having some success. I do note that you're reaching 1% (-40dBr) from power supply hum at 100Hz, perhaps a different amplifier with cleaner output would be helpful. That noise comes through in the residual quite clearly when listening. I also didn't use a very high end amp for my testing (and with linear power supply), but for comparison I will provide an overlay of your noise floor vs mine. (yours is the red one)
One suggestion that has been made is to use some EQ to compensate for the non-linearity of the driver impedance, for a better apples to apples comparison between drivers. I plan to test this for myself in the next while.
Reviewing @JanRSmit measurement, great to see that you're having some success. I do note that you're reaching 1% (-40dBr) from power supply hum at 100Hz, perhaps a different amplifier with cleaner output would be helpful. That noise comes through in the residual quite clearly when listening. I also didn't use a very high end amp for my testing (and with linear power supply), but for comparison I will provide an overlay of your noise floor vs mine. (yours is the red one)
One suggestion that has been made is to use some EQ to compensate for the non-linearity of the driver impedance, for a better apples to apples comparison between drivers. I plan to test this for myself in the next while.
Member
Joined 2003
Well the drivers were chosen specifically to provide contrast, so that it can be made clear that there is value in the measured result that is easily heard. With two very similar high end drivers, the differences may be a lot harder to pick out, but there is the spectrum chart in REW as a guide, as well running the residual audio through a spectrogram can help as a visual aid.
Thanks @DcibeL , both for the filter option and the mains hum issue. But above all that the test setup indeed works. I have a good amp available so that willl be next mod to the test rig.
What is a good approach to listen to the residual noise? How to increase the level without issues?
The spectrogram i played with, the problem is the interpretation. The mains issue is clearly visible, the issues in the useable range of the tweeter are not so.
I did go through john mulcahy postings on avnirvana , still digesting bits.
What is a good approach to listen to the residual noise? How to increase the level without issues?
The spectrogram i played with, the problem is the interpretation. The mains issue is clearly visible, the issues in the useable range of the tweeter are not so.
I did go through john mulcahy postings on avnirvana , still digesting bits.
Member
Joined 2003
Set default playback device in your OS to be something other than your test equipment. I play back on a good set of headphones. I've been using around 40dB of gain. REW will not allow a gain value that will clip the signal above 0dBFS, so you can just enter a large gain value and see what it says the limit is, dial it back a couple dB for comparison. It's important to compare at same amplitude, which will vary somewhat from driver to driver, especially 4 ohm vs 8 ohm, and make sure input gain on your audio interface remains constant, otherwise the playback level will be thrown off as well.
For initial testing, not requiring direct comparison between measurements, Just crank the gain and let REW play back as loud as it can so you can hear the residual and noise floor clearly.
If you want to take a deep dive into signal analysis, there are options in the measurement window to save the original playback audio (excitation), mic input (electrical input in this case), and LTI response in addition to the residual audio. The residual audio is saved in the MDAT file, however the others are not. If you haven't configured a FSAF folder in REW, these files will end up in REW's temp folder. Files will be named by the measurement UUID, found under measurement info. All the audio is saved as 32bit float data, so you don't have to worry about SNR of the digital format at all.
For initial testing, not requiring direct comparison between measurements, Just crank the gain and let REW play back as loud as it can so you can hear the residual and noise floor clearly.
If you want to take a deep dive into signal analysis, there are options in the measurement window to save the original playback audio (excitation), mic input (electrical input in this case), and LTI response in addition to the residual audio. The residual audio is saved in the MDAT file, however the others are not. If you haven't configured a FSAF folder in REW, these files will end up in REW's temp folder. Files will be named by the measurement UUID, found under measurement info. All the audio is saved as 32bit float data, so you don't have to worry about SNR of the digital format at all.
Want to get it fully working and reproducable results. So when the purifi tweeter arrives here i can test the lot and compare to the sb26adc-03WG ;-)
Member
Joined 2003
What I am finding with this testing, is that drivers obviously have very different suspension systems, so free air testing through bass range and around Fs is not exactly an equal comparison between drivers. Even though the midrange SPL may be equal, they can have very different cone excursions at low frequency which throws off a comparison. The driver either need to be properly loaded in a cabinet for similar FR (for same size of driver), or some EQ applied to ensure equal driver excursion through the bass range, or cut the bass range with LR-48 filter at 100Hz to ensure the result is low excursion, not ideal.
As it is, clear differences between motors can be easily detected, but when drivers are very similar in performance, chances are the one that exhibits lower excursion played free air may appear to be the better driver.
This is doable, but requires some extra steps of measuring TSP for each driver, and model in infinite baffle, and apply EQ for equal excursion. VituixCAD enclosure tool, save driver excursion as overlay, and then use the filter section to design a filter to align the driver excursion.
As it is, clear differences between motors can be easily detected, but when drivers are very similar in performance, chances are the one that exhibits lower excursion played free air may appear to be the better driver.
This is doable, but requires some extra steps of measuring TSP for each driver, and model in infinite baffle, and apply EQ for equal excursion. VituixCAD enclosure tool, save driver excursion as overlay, and then use the filter section to design a filter to align the driver excursion.
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