It's a standard technique. For example some may even be familiar with it in regard to radio direction finding.
Constructive interference is relatively indistinct between angles but a null is quite specific.
The third and even better option is using a non USB microphone.
Constructive interference is relatively indistinct between angles but a null is quite specific.
You look for one, then you can find the distance geometrically.
The third and even better option is using a non USB microphone.
Well I am making progress on my cabinets and hopefully soon I will be able to finisih the cabinets to the point I can install the drivers and proceed with the recommended testing. Thanks for your guidance and patience 🙂
Im back. OK I am ready to begin measuring actual On Baffle FRD. As I understand it now I do each driver individually. What about pairs. I also do zma at the same time and Also I am aware that the mic is not to move not even a millimeter lol!
Kindly advise thanks all.
Kindly advise thanks all.
Why pairs? Measure everything apart that you can feed apart (as in:can have an own crossover branch). Most Xover sim apps I know accept a lot of individual drivers.
mark, I thought that part of the process was to also find the acoustic centers. Now I wont have a stepped baffle, but I was told that it can be accounted for "in the crossover".
For USB mics only.
That is for non USB mics. Have you decided how you will compensate for that.. does it involve moving the mic?
AllenB: I am using OmniMic with a USB Mic. So it sounds like since I am using a USB Mic I am supposed to test drivers in Pairs? W/M M/T? Its a 3 way speaker. So as long as the mic is relatively in the same position.
Ok there are a number of things that could change if you move the mic, but let's get this straight.
For example, would the woofer change its response if you measure from tweeter height instead of dropping the mic a little, because then it will be a little off axis? Perhaps slightly... but that's not what we're talking about here is it? (....Before I go on, I'm assuming you're not doing polar style multi-angle measurements, correct me if that's not true)
Since USB won't be timing, you'll first take a measurement of each driver separately. You then have REW find the beginning of the impulse for you...
Do not derive minimum phase because that will flatten the diffraction energy. Simply find the start of the impulse so the delay becomes zero.
Convert these to FRD files and put them into your simulator. The next thing is to work out the delay between them, which you will enter manually into your simulator. This is the part where you test both drivers together....
For example, would the woofer change its response if you measure from tweeter height instead of dropping the mic a little, because then it will be a little off axis? Perhaps slightly... but that's not what we're talking about here is it? (....Before I go on, I'm assuming you're not doing polar style multi-angle measurements, correct me if that's not true)
Since USB won't be timing, you'll first take a measurement of each driver separately. You then have REW find the beginning of the impulse for you...
Do not derive minimum phase because that will flatten the diffraction energy. Simply find the start of the impulse so the delay becomes zero.
Convert these to FRD files and put them into your simulator. The next thing is to work out the delay between them, which you will enter manually into your simulator. This is the part where you test both drivers together....
Ok so for me a little knowledge is dangerous. I know just enough to get myself in trouble ha ha. Embedded are my responses.
Can it set the start of your impulse? (this means you see the impulse waveform and it marks the beginning and sets that so phase starts from that point.)
Can it save the result as an frd file?
At what angle will you listen? (Eg: 20-30 degrees off-axis often suits the power of certain speakers. Sometimes it's about turning away from walls... etc.)
@AllenB It turns oout I do have REW on my computer however I never used it. Thats for another discussion after I open it and poke around.
I will take some time with Omnimic to see about the impulse marking.
I have a pretty decent listening room and it is usually just me listening 95% of the time. I am usually just a few degrees off axis as I angle my speakers slightly inward so are you suggesting that I take my off axius measurements at angles that wiull be more representative of my listening? I can do 10 or 20 degrees instead?
I will take some time with Omnimic to see about the impulse marking.
I have a pretty decent listening room and it is usually just me listening 95% of the time. I am usually just a few degrees off axis as I angle my speakers slightly inward so are you suggesting that I take my off axius measurements at angles that wiull be more representative of my listening? I can do 10 or 20 degrees instead?
It's a little more involved than that. What are you planning to do with your multiple measurements? Will you use them together in a simulator or will you have them available to view separately but base your crossover on the on-axis measurement?
PLan on using the frd and zma in a simulator to develop the XO. I was originally using manufacturer frd files (or traced fr graphs). However, for improved accuracy ive been advised to measure the drivers on the baffle and (convert?) to frd and use them instead. I will also measure for zma as well (in a cabinet or free air?) I was going to base the XO using on axis measurements,
Ok. For single axis crossover design, you want to consider the compromise. For power purposes, the 0 degree axis is not very representative of the speaker as a whole.
The other thing is that you might prefer to take phase based on your listening axis, so by all means consider doing your measurements there.
The other thing is that you might prefer to take phase based on your listening axis, so by all means consider doing your measurements there.
I started with zma in cabinet see attached. I also "exported as zma and saved them. Next is .frd
Midrange
Tweeter
Woofer
Midrange
Tweeter
Woofer
trying to interpret the woofer zma. there are 2 major peaks and one small one. The small one is probably from a cabinet issue(?) The first peak is at 17 hz and the next at 60hz. As I understand it one is the woofer at resonance the other is the fb??? I know I probably have it wrong so you assistance in correcting me is welcome. Thanks