The measurements are only based on the far field. It's a MTM, hence no adjustment for the Y. and the woofers are in line with the tweeter, so and and Y are at 0 - and only Z is entered - these values match the blended curve.
I need to pad the values a bit more in Holm Impulse so that they fall in the PCD range.
The measurements are only based on the far field. It's a MTM, hence no adjustment for the Y. and the woofers are in line with the tweeter, so and and Y are at 0 - and only Z is entered - these values match the blended curve.
I need to pad the values a bit more in Holm Impulse so that they fall in the PCD range.
For an MTM you should measure each M individually, then change number of
woofers to "2", then enter the Y offsets into Woofer 1 and Woofer 2.
Load in the FRD and ZMA for the 2nd woofer at the bottom where it says
"2nd woofer FRD/ZMA".
The measurements are only based on the far field. It's a MTM, hence no adjustment for the Y. and the woofers are in line with the tweeter, so and and Y are at 0 - and only Z is entered - these values match the blended curve.
I need to pad the values a bit more in Holm Impulse so that they fall in the PCD range.
For an MTM you should measure each M individually, then change number of
woofers to "2", then enter the Y offsets into Woofer 1 and Woofer 2.
Load in the FRD and ZMA for the 2nd woofer at the bottom where it says
"2nd woofer FRD/ZMA".
I do the summed as one approach for MTMs because I don't need the off axis estimate by PCD and it's a PITA to derive separate ZMAs for the woofer.
You will still get the summed as one response when you attempt to determine the Z, so the offsets are hosed when splitting the woofers.
After a conversation with Jeff Bagby a number of years ago I switched to measuring MTM's with both woofers playing together and ignoring the Y offset. I have been very pleased with my results.
The system response matched very well with only the z axis entered. Anyways, I will try both woofers individually to get a feel of it and contrast with measuring both woofers together.
To continue with the topic of this thread, I would like to understand taking nearfield or mic in box measurements and splice with the far field.
I am putting the XO tweak on hold and just focus on measuring.
Would like to try both method and then maybe try the ground plane method to compare.
So, practical way, or rather what's your way of measuring nearfield or MIB if you have tried it. Like I said I have destroyed woofers in the past by trying to take nearfield measurements, trying to set the mic very close to the cone and the woofer smacked into the mic putting a nice impression into the smooth alu cone.
So how close do I need to be to the cone, and I believe I was trying to measure at the same level as at 1M, but at 0.25" I can turn the amp down way low.
You may want to attempt re-measuring your drivers for simulation as I don't see the best agreement between the simulation and your final measurements. It looks like you are working from just a far field measurement as well for the woofer, merging near and far data can make a world of difference for determining that BSC range to see what's going on from 200-800Hz. Just a couple tips as well, remember to enter in the effective driver diameter to PCD so the off-axis sim is accurate, as well try to load in measurements in the 80-90dB range so they appear in the middle of the plot and the zoom buttons don't shift them off the chart. You also haven't entered any X or Y offsets which is important for accurate simulation.
+1. If your sim doesn't match your measurement something is definitely wrong and you really can't make any conclusions. Ani - just in case you haven't seen them I attached Jeff's two excellent papers on how to take accurate measurements.
Is Jeff's FRD Blender the best tool for merging? Is there any other alternative. The new version of PCD works fine with newer excels, but FRD Blender seems to give some circular reference errors that i am not able to get around.
The measurements are only based on the far field. It's a MTM, hence no adjustment for the Y. and the woofers are in line with the tweeter, so and and Y are at 0 - and only Z is entered - these values match the blended curve.
I need to pad the values a bit more in Holm Impulse so that they fall in the PCD range.
For an MTM you should measure each M individually, then change number of
woofers to "2", then enter the Y offsets into Woofer 1 and Woofer 2.
Load in the FRD and ZMA for the 2nd woofer at the bottom where it says
"2nd woofer FRD/ZMA".
I do the summed as one approach for MTMs because I don't need the off axis estimate by PCD and it's a PITA to derive separate ZMAs for the woofer.
You will still get the summed as one response when you attempt to determine the Z, so the offsets are hosed when splitting the woofers.
I guess I don't understand what is such a PITA to measure a single driver and enter a Y value. You don't even need to load in the 2nd woofer FRD/ZMA data unless there are differences between the two (like if you wanted to apply baffle diffraction individually to the different drivers due to the baffle location). You'd already have the ZMA for a single driver by itself I'm sure, isn't it more work to do another impedance sweep of both drivers in parallel.
I like accurate data, especially off-axis. The power response in PCD also won't be correct loading in the pair of drivers as one.
Is Jeff's FRD Blender the best tool for merging? Is there any other alternative. The new version of PCD works fine with newer excels, but FRD Blender seems to give some circular reference errors that i am not able to get around.
FRD Blender is great, in that it's fairly easy to use and has the baffle diffraction component built in. VituixCAD works well for this as well for something that doesn't need Excel.
You can do the splice using the Omnimic software as well, but you have to apply the baffle diffraction to the nearfield response externally then load the response back in. See the Help file How To section for details on splicing right in the Omnimic software.
Go ahead and read through the documents I posted at the start of this thread, and re-posted by Ed above.
Is Jeff's FRD Blender the best tool for merging? Is there any other alternative. The new version of PCD works fine with newer excels, but FRD Blender seems to give some circular reference errors that i am not able to get around.
FWIW I just loaded this spreadsheet in Excel 2003 as well as Office 365 and it didn't have any issues either way.
Is Jeff's FRD Blender the best tool for merging? Is there any other alternative. The new version of PCD works fine with newer excels, but FRD Blender seems to give some circular reference errors that i am not able to get around.
FWIW I just loaded this spreadsheet in Excel 2003 as well as Office 365 and it didn't have any issues either way.
You can place the mic pretty much anywhere from 1/4" to 1/2" from the driver and get the nearfield data. Yes, you should turn down the volume knob, if your driver is moving more than 1mm you're doing it wrong. At 5mm the mic will see 26dB more volume than it would at 1m, so keep that in mind. Take a few measurements in different locations and see if you get the same response from 20-800Hz or so.
As a rule, the nearfield measurement data accuracy is dependent upon the diameter of the driver being measured. The maximum useful nearfield frequency is determined by fmax = 10950 / D , where D = the diameter of the speaker in centimeters.
You don't need the effective diameter for nearfield measurements. For nearfield remember to turn down the volume and open the gating. Probably best to walk through as you get ready to measure. The near field is the last measurement. This is the only time you get to move the mic and change the volume.
You don't need the effective diameter for nearfield measurements.
Or you can look at simple math to see how much of that nearfield measurement contains useful data As you move into larger drivers, you may want to look at the simple math equation I posted above. The maximum useful frequency for nearfield data decreases, as well the gating of the far field measurements will often be shorter as you have to move the mic further away to get a good far field measurement. The larger the driver, the harder it is to get good full frequency measurements indoors.
Is Jeff's FRD Blender the best tool for merging? Is there any other alternative. The new version of PCD works fine with newer excels, but FRD Blender seems to give some circular reference errors that i am not able to get around.
I get that error message with 32-bit Excel 2010 on 64-bit Windows 10, but ignore it and Blender seems to work fine. I don't get the error with Excel 2003 running 32-bit Win 7 Pro (in a virtual machine).
@4thtry had a nice write up of the sequenced steps on PETT that was easy to follow imo
Thanks, John. Attached is a pdf of my XSim step by step procedure. I didn't bring this up earlier because this discussion seems to be mainly about using other microphones and software. I am using OmniMic, DATS V2, XSim, and the Blender. Sometimes I move over to PCD so that I can run polar simulations. Sometimes I take extra measurement sets and run my polar sims in XSim.
Steps 33 and 34 in my listing are somewhat lame. Step 34 really does not work very well because of weird response anomalies in the 80 to 300Hz region. You can't just smooth the anomalies out like I suggest. I was having trouble getting the blender to work, but I was able to clear up my confusion with Jeff Bagby last year. He set me straight on what I was doing wrong. My step 33 needs to be expanded into a 20-30 step procedure of its own, one that avoids all the pitfalls of using the blender properly.
thanks Bill. to attach a PDF, click on the attach file, and select the file. You will see the file being uploaded. Then drag the file onto the message.
Comments
I need to pad the values a bit more in Holm Impulse so that they fall in the PCD range.
https://drive.google.com/drive/folders/1KpSwd8eiFf5Kb46I_pThX29eCN0Mlbvb?usp=sharing
For an MTM you should measure each M individually, then change number of woofers to "2", then enter the Y offsets into Woofer 1 and Woofer 2. Load in the FRD and ZMA for the 2nd woofer at the bottom where it says "2nd woofer FRD/ZMA".
You will still get the summed as one response when you attempt to determine the Z, so the offsets are hosed when splitting the woofers.
I am putting the XO tweak on hold and just focus on measuring.
Would like to try both method and then maybe try the ground plane method to compare.
So, practical way, or rather what's your way of measuring nearfield or MIB if you have tried it. Like I said I have destroyed woofers in the past by trying to take nearfield measurements, trying to set the mic very close to the cone and the woofer smacked into the mic putting a nice impression into the smooth alu cone.
So how close do I need to be to the cone, and I believe I was trying to measure at the same level as at 1M, but at 0.25" I can turn the amp down way low.
How to Achieve Accurate In-Room Quasi-Anechoic Free-Field Frequency Response Measurements Down to 10 Hz.pdf
Finding the Relative Acoustic Offset in PCD .pdf
FWIW I just loaded this spreadsheet in Excel 2003 as well as Office 365 and it didn't have any issues either way.
Thanks, John. Attached is a pdf of my XSim step by step procedure. I didn't bring this up earlier because this discussion seems to be mainly about using other microphones and software. I am using OmniMic, DATS V2, XSim, and the Blender. Sometimes I move over to PCD so that I can run polar simulations. Sometimes I take extra measurement sets and run my polar sims in XSim.
Steps 33 and 34 in my listing are somewhat lame. Step 34 really does not work very well because of weird response anomalies in the 80 to 300Hz region. You can't just smooth the anomalies out like I suggest. I was having trouble getting the blender to work, but I was able to clear up my confusion with Jeff Bagby last year. He set me straight on what I was doing wrong. My step 33 needs to be expanded into a 20-30 step procedure of its own, one that avoids all the pitfalls of using the blender properly.
How do you get a pdf to attach? Does not look like it worked. Try again:
thanks