I am measuring SB Acoustics TW29R tweeter for a 2 way speaker with Jantzen JA8008 woofer. I am using OmniMic v2 software for measuring and creating the FRD files. I am using OmniMic's built in "Driver FRD capture guide" (a pop-up wizard detailing each step) and it wants me to play the same signal through the woofer and the tweeter at the same time so it can determine Z offset.
I used the full range sweep for the woofer FR in step one of the wizard, but step 2 wants me to play the same signal through woofer and tweeter simultaneously, and I'm worried that full range sweep could damage the tweeter. The otherwise excellent help file doesn't mention this step 2 as it's so simple even I can get confused.
Question: Can I play the full range test sweep through the tweeter if the level is very low? This tweeter is 92dB sensitivity (4R) and will require fraction of 1 watt to make 80dB for the test. It is rated 80W behind a 2nd order filter at 2600Hz.
^ The published FR, 1W, shows the signal as low as 100Hz.
OmniMic has a bass-limited test sweep track which rolls off at 250Hz for -40dB at 100Hz. That would protect the tweeter nicely, but it's not the "same track" that I used on the woofer, as requested by the wizard.
If I shouldn't run the tweeter full range test sweep, then should I run this bass limited test sweep on the woofer and the tweeter simultaneously to make FRDs for the crossover sim?
My guess is that the low frequency signal will not hurt the tweeter as long as voltage is constant through the sweep and does not exceed 1 watt. Excursion will still be the same at 20Hz as it is at 10kHz at the same voltage. I think I already did this to other tweeters in the past before I knew enough to worry about it.
Thanks All!
I used the full range sweep for the woofer FR in step one of the wizard, but step 2 wants me to play the same signal through woofer and tweeter simultaneously, and I'm worried that full range sweep could damage the tweeter. The otherwise excellent help file doesn't mention this step 2 as it's so simple even I can get confused.
Question: Can I play the full range test sweep through the tweeter if the level is very low? This tweeter is 92dB sensitivity (4R) and will require fraction of 1 watt to make 80dB for the test. It is rated 80W behind a 2nd order filter at 2600Hz.
^ The published FR, 1W, shows the signal as low as 100Hz.
OmniMic has a bass-limited test sweep track which rolls off at 250Hz for -40dB at 100Hz. That would protect the tweeter nicely, but it's not the "same track" that I used on the woofer, as requested by the wizard.
If I shouldn't run the tweeter full range test sweep, then should I run this bass limited test sweep on the woofer and the tweeter simultaneously to make FRDs for the crossover sim?
My guess is that the low frequency signal will not hurt the tweeter as long as voltage is constant through the sweep and does not exceed 1 watt. Excursion will still be the same at 20Hz as it is at 10kHz at the same voltage. I think I already did this to other tweeters in the past before I knew enough to worry about it.
Thanks All!
80 decibel full-range sweep on the Tweeter should not hurt it. It would also be acceptable to use the bass limited track that came with the Omni mic software. By the way I could never get the Z offset feature of the software to work for me. I probably just didn't read the instructions correctly. Instead I use the X Sim software
Member
Joined 2003
Hifijim is right, at low level there is little concern of damage for a standard dome tweeter, but do not repeat this process with a ribbon. If you do want to use a bass limited sweep that is okay as well, but you will have to use that sweep consistently for all measurements when determining Z offset.
The process is fairly simple, and can be completed externally with other software as well such as VituixCAD, Xsim, WinPCD, which may be more convenient if you are doing the design work in that software anyway. Essentially you keep the mic at tweeter axis, measure tweeter, then woofer, then both. Load the responses into your software of choice, and the "both" response is overlaid, then offsets adjusted until the sum of the individual measurements matches that of both playing together. It is a roundabout way of determining differences in acoustic distance to the mic due to the fact that you cannot measure the "time of flight" using a single channel system such as Omnimic.
The process is fairly simple, and can be completed externally with other software as well such as VituixCAD, Xsim, WinPCD, which may be more convenient if you are doing the design work in that software anyway. Essentially you keep the mic at tweeter axis, measure tweeter, then woofer, then both. Load the responses into your software of choice, and the "both" response is overlaid, then offsets adjusted until the sum of the individual measurements matches that of both playing together. It is a roundabout way of determining differences in acoustic distance to the mic due to the fact that you cannot measure the "time of flight" using a single channel system such as Omnimic.
Thanks both!
Yes, I am planning to use XSim for xo design anyway. I will try XSim for the offset calc.
I did use OmniMic to measure Z offset once, I think I was just following the help file instructions. I was intimidated going in but as I remember it turned out to be surprisingly easy. It sounds easy to do in XSim also.
Thanks again!
Yes, I am planning to use XSim for xo design anyway. I will try XSim for the offset calc.
I did use OmniMic to measure Z offset once, I think I was just following the help file instructions. I was intimidated going in but as I remember it turned out to be surprisingly easy. It sounds easy to do in XSim also.
Thanks again!
Last edited:
Member
Joined 2003
In Xsim you can use the "get file" option to load in the overlay response, and for best results be sure to disable the smoothing of the driver responses that are enabled by default (options under the curves menu).