Hi,
I've taken woofer and tweeter measurements on different axises and imported them to VituixCAD. I also took a measurement with the woofer and tweeter in parallel, with the mic centered between them.
My question is how do I get the VituixCAD measurement / starting point to be close to / equal to the parallel measurement? I want to make sure the software's starting point agrees with reality in terms of Z axis of the drivers, alternatively by adding a delay to one of them. This will be for a digital crossover.
Thank you
edit: Here's the REW response of drivers in parallel (therefore perfectly aligned time wise from a physical install perspective - not from a "is this the correct Z depth alignment for perfect sound" perspective):
How do I get VituixCAD to match the above so the starting point is the same? Is it just switching back and forth between REW and VituixCAD while changing the Z depth of the tweeter until it matches somewhat? Because I can't get a good result doing that...
I've taken woofer and tweeter measurements on different axises and imported them to VituixCAD. I also took a measurement with the woofer and tweeter in parallel, with the mic centered between them.
My question is how do I get the VituixCAD measurement / starting point to be close to / equal to the parallel measurement? I want to make sure the software's starting point agrees with reality in terms of Z axis of the drivers, alternatively by adding a delay to one of them. This will be for a digital crossover.
Thank you
edit: Here's the REW response of drivers in parallel (therefore perfectly aligned time wise from a physical install perspective - not from a "is this the correct Z depth alignment for perfect sound" perspective):
How do I get VituixCAD to match the above so the starting point is the same? Is it just switching back and forth between REW and VituixCAD while changing the Z depth of the tweeter until it matches somewhat? Because I can't get a good result doing that...
Last edited:
Member
Joined 2003
Sounds like you are following single channel / USB mic measurement process. I would suggest reading/following the measurement guide for REW as a starting point. You can find it in the help file under “how to start working with vituixcad”
I read the help file, it says "(...) USB mics are not recommended", it does not say "will not work at all for crossover design", which is why I proceeded.
So, all the data is rubbish, nothing can be done except buying a calibrated analog, mic and pre-amp? edit: What would change in my scenario exactly, if I used the recommended hardware - is my process fine and the data would just line up to match REW, or am I doing something wrong process wise (irrelevant of measurement data accuracy)?
How I would do it. Don't change drive levels nor speaker nor mic position between measurements. Ensure your drive level is ~ 0.5v to protect tweeter from full range sweep
1. Measure tweeter - import as driver 1
2. Measure woofer - import as driver 2
3. measure both tweeter and woofer in parallel - import as driver 3
4. Tell Vituix cad to use derived not measured phase (unsure how)
5. Create a single passive crossover network - with all 3 drivers connected in parallel with the source
6. change Driver #2 (woofer) Z offset in crossover tab until the sum of driver 1 and driver 2 matches driver 3
1. Measure tweeter - import as driver 1
2. Measure woofer - import as driver 2
3. measure both tweeter and woofer in parallel - import as driver 3
4. Tell Vituix cad to use derived not measured phase (unsure how)
5. Create a single passive crossover network - with all 3 drivers connected in parallel with the source
6. change Driver #2 (woofer) Z offset in crossover tab until the sum of driver 1 and driver 2 matches driver 3
oops, time to read VituixCAD manual and relevant measurement guide, best advice is there.
https://kimmosaunisto.net/
When the recommended procedure is mastered, or at least one is comfortable with what one is doing, then some guerilla / shortcut methods might be close enough and yield fine enough results in some cases.
Results are only as good as the data no matter what software. It takes some effort to get there but its worth it, unless performance target is sub par.
https://kimmosaunisto.net/
When the recommended procedure is mastered, or at least one is comfortable with what one is doing, then some guerilla / shortcut methods might be close enough and yield fine enough results in some cases.
Results are only as good as the data no matter what software. It takes some effort to get there but its worth it, unless performance target is sub par.
Last edited:
Member
Joined 2003
If you wish to include off-axis data for power & DI chart, directivity chart for multiple driver systems, dual channel or semi-dual channel system should be a requirement. This is because the "acoustic centre" is a moving target off-axis, a timing reference is important for accurate simulation, as well the whole process is simplified with less potential for error.
With USB mic I will provide some simple steps for single-axis simulation only, you can forget about power & DI, or even simulation at a distance other than where the mic is located.
1. Locate the mic at your listening axis, usually the tweeter axis. Distance at about 1m. Measure tweeter, woofer, and both in parallel.
2. Under Aux - time align load these 3 measurements, uncheck the "MP" boxed and solve for the delay.
3. Measure nearfield of the woofer.
4. Simulate baffle diffaction using the diffraction tool, save the result
4. Splice nearfield with baffle diffraction and far field of the woofer using the merge tool.
5. Load merged response for the woofer to the driver tab, enter delay in the driver tab found in step 2.
6. Load tweeter far field response to the driver tab for the tweeter.
7. Leave driver coordinates at 0,0,0 in the crossover.
Member
Joined 2003
Dave, have a look under the Auxiliary - Time Align, this process is automated for you. Delay can/should be entered directly to the driver tab, offsets in crossover section reserved for physical distance offsets.
thanks. I realise the Z is normally applied on the driver tab, but the manual alignment approach meant you would need to change it on the crossover tab so you could see both drivers aligning to the combined response.
Proper dual channel measurements with an analogue mic is the preferred way, but, if you don't have one you can try using Holm Impulse with the time lock function.
This thread lays out some information relevant to it
https://techtalk.parts-express.com/forum/tech-talk-forum/55182-holm-and-time-locking
There are more threads and guides available with a search.
Member
Joined 2003
That is an extremely fair point you're making there!!!
With windows 10, single channel measurements are a bit a hit or miss.
With using direct ASIO drivers, it might be possible, but only maaaaybe.
In the old days with WinXP we only got some very minor artifacts, which made phase response look rather rugged, but the relative phase difference was still good enough for making filters.
I only use ARTA, so maybe there are also a slight differences.
Member
Joined 2003
Just to clarify, if you use the recommended hardware, you would also follow the measurement guide procedure which does not require any extra steps to determine acoustic offsets/delay between drivers. Timing information will be inherent to the measured data as long as mic distance to baffle remains constant for all measurements.
Got it. I wonder how you don't change the mic distance when going from 0 to 90 degrees in steps of 15, for example. You just measure end of mic to same spot on the speaker?
Member
Joined 2003
If your drivers are centred in the baffle, pivot point is the front centre point of the baffle so you should only have to set the mic distance once. Some people get fancy turntable / lazy suzan contraptions, or you can move the speaker manually, print a polar chart and tape it under the speaker to keep that pivot point. Off centre drivers require off-centre pivot point.
For changing drivers you can either raise/lower the speaker or raise/lower the mic, in both cases take care to re-measure and verify the distance to keep mic as close as possible to the same distance mic to baffle surface.
For changing drivers you can either raise/lower the speaker or raise/lower the mic, in both cases take care to re-measure and verify the distance to keep mic as close as possible to the same distance mic to baffle surface.
It certainly isn't the best way, but once you have it locked properly it will give accurate time referenced measurements. The simple sensible solution is to do things properly with the right equipment but that doesn't seem to be an available option 🙂
Hi
How would a measurement look step by step for a Heco Victa 700?
MTWW design with parallel connected woofers.
With two reflex tubes.
(not exactly the best design for beginners: D)
Thanks in advance.
Member
Joined 2003
As a beginner, best thing you can do is toss the USB mic, get a proper mic and audio interface, follow VituixCAD measurement guide.
For the woofer pair, if each woofer has it's own air space in the cabinet, just measure individually as you would any other driver. If they share the same cabinet air space, for far field measurement, simply disconnect one driver. With only one driver connected, cabinet interaction will be incorrect, but should not be of significance for far field measurement from >200Hz. For near field measurement, measure with both drivers connected so correct cabinet effect is included for low frequency measurement.
In-box impedance can be measured with both drivers in parallel, however for single driver in crossover, scale measured impedance accordingly. Scale by 2 for parallel, scale by 0.5 for series connected drivers.
For the woofer pair, if each woofer has it's own air space in the cabinet, just measure individually as you would any other driver. If they share the same cabinet air space, for far field measurement, simply disconnect one driver. With only one driver connected, cabinet interaction will be incorrect, but should not be of significance for far field measurement from >200Hz. For near field measurement, measure with both drivers connected so correct cabinet effect is included for low frequency measurement.
In-box impedance can be measured with both drivers in parallel, however for single driver in crossover, scale measured impedance accordingly. Scale by 2 for parallel, scale by 0.5 for series connected drivers.
I finally understand impedance measurement. (I combine my knowledge of English with Google Translate, which is not exactly ideal)
For far-field measurements is the microphone in one position throughout? At listening height?
When I have the first measurements, I will come with my further questions. 😀
For far-field measurements is the microphone in one position throughout? At listening height?
When I have the first measurements, I will come with my further questions. 😀
Member
Joined 2003
Hi @wickers , since you’re posting in this thread, it’s not clear if you are using a usb mic or not. “Correct” process would be to use standard mic with loopback timing reference, and measurement data is gathered by measuring on axis with each driver. In this manner, timing information between drivers can be captured by simply keeping a constant distance from mic to baffle surface and using the same window settings for all measurments.
Recommend reading through measurement guides for VituixCAD, found under “how to start working with VituixCAD” here:
https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html#How_to_start_with_VituixCAD
I have also written some information detailing the difference between single and dual channel measurement methods and other useful information here:
https://www.htguide.com/forum/articles/do-it-yourself-diy
Recommend reading through measurement guides for VituixCAD, found under “how to start working with VituixCAD” here:
https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html#How_to_start_with_VituixCAD
I have also written some information detailing the difference between single and dual channel measurement methods and other useful information here:
https://www.htguide.com/forum/articles/do-it-yourself-diy