Member
Joined 2003
Padding requirements is to match voltage sensitivity of driver, not specifically the nominal impedance. Woofer determines system sensitivity, do not pad it down with resistors.
It will dissipate a lot of power as heat, yes. For more information see view -> power dissipation in VituixCAD. Power dissipation will be dependent on location in circuit and part values, in general resistors placed post-filter will dissipate less power as heat.
If you put a resistor on both woofer and tweeter you will consume unnecessary power, it will just be inefficient. Try running one with no resistor and use resistance on the other one so they can be as sensitive (loud) as they can be... as long as you are happy with the shape of their responses.
OK, I have a question regarding setting delay/Z offsets when designing your crossover.
The more I read, the more confused I get.
In my situation when doing my measurements (0 to 180 deg horizontally), I only had my UMIK-1 usb calibrated mic, so I used a quality speaker as an acoustic timing reference. I did all the measurements using REW.
The speakers are TL towers with the woofer 854mm above the floor and the cone "tweeter" 1172mm above the floor.
As the "tweeter" was so high, I located the mic 900mm above the floor and the normal 1000mm from the vertical baffle.
Doing the maths, the distance from mic to the tweeter's acoustic centre was 1063mm (309us); the distance from the mic to the woofer's acoustic centre was 1041mm (303us).
Although I didn't measure the distance from the reference speaker to the mic, I think it was around 1140mm (331us).
REW recorded the tweeter as having a "Delay of -0.3280ms" (-328us); and the woofer as having a "Delay of -0.2734ms" (-273us).
I gated the far field measurements and merged them with my near field measurements.
I then exported the merged measurements as text into VituixCAD.
My problem is what to do next in VituixCAD regarding adding delays, Z offsets, etc.
Have these settings already been taken care of?
Do I have to still add delays, etc. to the drivers, and what would they be?
The more I read, the more confused I get.
In my situation when doing my measurements (0 to 180 deg horizontally), I only had my UMIK-1 usb calibrated mic, so I used a quality speaker as an acoustic timing reference. I did all the measurements using REW.
The speakers are TL towers with the woofer 854mm above the floor and the cone "tweeter" 1172mm above the floor.
As the "tweeter" was so high, I located the mic 900mm above the floor and the normal 1000mm from the vertical baffle.
Doing the maths, the distance from mic to the tweeter's acoustic centre was 1063mm (309us); the distance from the mic to the woofer's acoustic centre was 1041mm (303us).
Although I didn't measure the distance from the reference speaker to the mic, I think it was around 1140mm (331us).
REW recorded the tweeter as having a "Delay of -0.3280ms" (-328us); and the woofer as having a "Delay of -0.2734ms" (-273us).
I gated the far field measurements and merged them with my near field measurements.
I then exported the merged measurements as text into VituixCAD.
My problem is what to do next in VituixCAD regarding adding delays, Z offsets, etc.
Have these settings already been taken care of?
Do I have to still add delays, etc. to the drivers, and what would they be?
If you kept the mic and reference speaker in the same place for all these, and you didn't direct REW to reset them, then it is already taken care of.
The only reason you might want to consider the offset setting is if the mic position distance differences don't correspond to what you calculate (geometrically) that the listening position distance differences will be.
The only reason you might want to consider the offset setting is if the mic position distance differences don't correspond to what you calculate (geometrically) that the listening position distance differences will be.
Hi all,
I am new to Vituixcad and I want to simulate a non-standard configuration.
Since the visualisation is a bit limited (or I haven't found it yet), I cannot be sure I use the correct settings fro what I want to do.
I want to simulate the response of a floor standing speaker, driver mounted at the top surface pointing upward into the ceiling.
The cabinet is cylindrical (but I guess this does not matter) and is 70cm high, the top surface where the driver is mounted is 40cm circular.
The microphone should be 100cm height from the floor, and 100cm distance from the speaker.
I guess this should be configured in the Diffraction Tool, but I do not know what numbers top put in, what goes where.
The driver diameter is 210mm, and the baffle is as mentioned 400mm circular pointing upwards.
When I use this diffraction (provided that it is correctly set up) in combination with the enclosure and TS params to compose the driver, is there anything else I need to do in the rest of the project to get it right? There are params XYZRT for the driver in the room, and I do not know what R and T are.
Thanks in advance.
If you simply give me a RTFM advice, please hint me what pages that are relevant.
And please understand that I have a severe "reading is not necessarily understanding" problem.
bnilsson
I am new to Vituixcad and I want to simulate a non-standard configuration.
Since the visualisation is a bit limited (or I haven't found it yet), I cannot be sure I use the correct settings fro what I want to do.
I want to simulate the response of a floor standing speaker, driver mounted at the top surface pointing upward into the ceiling.
The cabinet is cylindrical (but I guess this does not matter) and is 70cm high, the top surface where the driver is mounted is 40cm circular.
The microphone should be 100cm height from the floor, and 100cm distance from the speaker.
I guess this should be configured in the Diffraction Tool, but I do not know what numbers top put in, what goes where.
The driver diameter is 210mm, and the baffle is as mentioned 400mm circular pointing upwards.
When I use this diffraction (provided that it is correctly set up) in combination with the enclosure and TS params to compose the driver, is there anything else I need to do in the rest of the project to get it right? There are params XYZRT for the driver in the room, and I do not know what R and T are.
Thanks in advance.
If you simply give me a RTFM advice, please hint me what pages that are relevant.
And please understand that I have a severe "reading is not necessarily understanding" problem.
bnilsson
Member
Joined 2003
I'll refer you back to the same thing I told you at the REW forum back in October. It appears you still have some confusion of what a timing reference is and does.
To re-iterate, since you're using an acoustic reference, distance from acoustic reference to mic must remain constant for all measurements. Recommend placing acoustic reference close to the mic for simplicity. When moving the mic to change from measuring tweeter to woofer, etc. acoustic reference has to move as well so be very careful and precise about this operation.
From here, simply follow the VituixCAD measurement guide for REW. Timing (delay) is captured in the measurement data, provided IR window reference time remains constant for all measurements, simply done in REW using "apply window to all" button as described in the guide. For flat baffle, z offset in software remains at 0, only physical offsets are entered, so x,y relations of drivers.
Effort should be made to place mic on axis with the driver being measured. given your description above it appears you are measuring the tweeter 15 degrees off axis.
You workflow description above is not following the guide. Only windowing is done in REW, use VituixCAD merge tool for merging near and far field responses in bulk.
Member
Joined 2003
Regardless of the direction the speaker points in the final design, treat measurement and response processing the same, so it's just a speaker on a baffle and the mic is in front of it. Speaker can be placed on its side with woofer forward facing if it makes measurement process easier. Then just proceed with measurement process following the guide for your favourite software. Round baffle can be made easily in diffraction tool by entering equal width and height and many corners.
R and T is "rotate" (horizontal) and "tilt" (vertical). In your case, when you enter the driver data for crossover simulation, use 90 degree tilt to have it face the ceiling, and enter x,y,z accordingly for relative physical relations to other drivers in the design.
Maybe misunderstanding here, I want to simulate at this stage, not measure.
If I create an enclosure with diffraction o-axis and export the SPL to use in the driver, putting T = 90 makes no difference whatsoever, the SPL curve remains the same.
Member
Joined 2003
Thanks Allen.
Mic didn't move for all far field measurements.
I didn't have a turntable, but I had the angles all marked on a sheet of mdf on the floor, and to the best of my ability the the Y axis on the baffle face did not move.
Thanks again for being patient with your reply.
With all the information out there, it's hard to know whether the delay adjustments (when using REW) carry through when exporting to VituixCAD or whether you have to add them in VituixCAD.
The mic didn't move during all measurements, and neither did the baffle's Y axis (I did horizontal measurements only).
The reason the mic was lower than the tweeter was to try and place the mic closer to listening height. The TL cabinet ended up being a lot higher than I had planned.
The reference speaker had to be adjacent and slightly behind the baffle of the test speaker to prevent any early reflections from it's cabinet.
I followed Kimmo's REW guide as best I could, given that I was using an acoustic reference (he doesn't like USB mics, so doesn't make any reference to using one or using an acoustic reference).
Once I gated the on-axis impulse, I used the "apply window to all". I exported the measurements to VituixCAD and merged and saved all measurement for each driver (both are cones). My baffle is flat and vertical.
Thanks again. I know now that I can proceed with the crossover design with correct settings i.e. dont touch the driver's Delay settings, and Z=0.
Are you planning to have any sort of deflector above the driver?
e.g. a common design similar to yours, has a cone above the driver to create an omni-directional speaker.
Any sort of deflector would have to be taken into account in your simulation and when measuring.
Also how do you intend to protect the driver?
Member
Joined 2003
Listening height can be adjusted easily in crossover design by adjusting y axis dimensions of drivers relative to listening height. But, this powerful feature only works properly when each driver is measured on its own axis.
if you want to have greater confidence in the timing reference, complete a simple comparison.
With mic stationary, measure woofer, tweeter, then both together in parallel. Go to aux -> time align and determine delay value (uncheck MP buttons). You should find value to be zero or near zero.
This can be worked out manually and you can keep your measurements too. I will post formulas if you like, or I can ask you some distances and work it out for you. (you can't just use the Y axis adjustment in a simulator if you didn't measure at driver height, as DcibeL says, but you can adjust for it. )
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Calculate the distance to the baffle at each driver height during the measurement (the baffle is the common element here), and work out the difference between woofer and tweeter. Then we do the same for the listening position.
If there's a difference in acoustic distance between the woofer and tweeter, then it's already in the measurement. We are not presently looking at that... only the difference between the differences in baffle distances between the listening position and the measurement position.
SQR(((900-1172)^2)+(1000^2))
= 1036mm
SQR(((900-854)^2)+(1000^2))
= 1001mm
The difference is 35mm.
>Now, with the listening distance and the listening height we can do the same thing for the listening position and compare the difference.
>Then discuss how to use it.
If there's a difference in acoustic distance between the woofer and tweeter, then it's already in the measurement. We are not presently looking at that... only the difference between the differences in baffle distances between the listening position and the measurement position.
SQR(((900-1172)^2)+(1000^2))
= 1036mm
SQR(((900-854)^2)+(1000^2))
= 1001mm
The difference is 35mm.
>Now, with the listening distance and the listening height we can do the same thing for the listening position and compare the difference.
>Then discuss how to use it.
No reflector planned. My idea was to let the baffle step effect work to my favour instead of being a problem, to make a smoother falloff at low frequencies. The crossover filter will divide at about 240Hz, and the upper range will be a forward directed full range driver. The design is inspired by but a very different implementation of, the Linkwitzlab Pluto.