1. Does REW calculate delay when measurement is done? Prior to this, REW cannot know what the delay is. Or may? If REW itself calculates the delay before or after the measurement, why should the user enter it?REW can estimate the delay using the entry in the graph controls
REW measures the time difference between the mic input and the loopback input for each measurement and includes any timing offset value that has been entered. The time of flight from the speaker to the microphone must still be removed. Estimate IR Delay can estimate that figure and it can be applied as the timing offset. From the help:1. Does REW calculate delay when measurement is done? Prior to this, REW cannot know what the delay is. Or may? If REW itself calculates the delay before or after the measurement, why should the user enter it?
No. Unless the amplifier contains its own digital signal processing it will not have any significant delay, and even if it did that delay would be the same for each measurement. It is the delay from speaker to mic (with or without any amplifier delay depending on where the loopback connection is taken from) that must be found and entered as the timing offset.2. In circuit 1 the signal at the output of the sound card appears at its input without delay. Then REW will consider this moment as the reference point. And the signal transit time through the amplifier + speaker will be considered as the signal transit time only through the speaker. Is that right?
In circuit 2 the signal appears simultaneously at the input of the sound card and at the speaker. Maybe the start of the count of the time will be correct in this case?
Changes by how much?1. I took measurements according to scheme 1. The first measurement gives the delay value. The second measurement and subsequent ones already use the calculated delay. If the measurements are repeated several times, then sometimes the program considers that the delay has changed, although nothing has changed. The microphone did not move, the speaker either, the sound card and amplifier settings did not change.
That would be a bug, though I can't reproduce it. Can you attach the mdat file for an example measurement that shows that, saved at the point you have made the measurement and you see the button is not enabled?2. After the measurement, I want to see the minimum phase. However, the “generate minimum phase' button is not active. It is necessary to note the checkbox 'phase', then the button 'generate minimum phase' becomes active. Even if you check the 'phase' checkbox and immediately remove the checkmark, the 'generate minimum phase' button also becomes active. Is it possible to make the 'generate minimum phase' button immediately active. It is even better to make the minimum phase graph appear along with the frequency response graph automatically.
A measurement exported as text has the measured phase, not the minimum phase. Please attach an example export file where the measurement is smoothed and the phase not smoothed and the measurement mdat file it was exported from.3. If I want to export a measurement to a txt file, I can specify smoothing, for example, 1/6. In this case, the frequency response graph is saved with the specified smoothing, and the minimum phase graph is saved without smoothing.
I found this button and created txt files with minimal phase. Thank you.a button in the All SPL graph controls
I had 4 measurements of 4 speakers. Speakers in a speaker enclosure. The microphone is always in one position. Will the delay offset be different for each measurement? Which tool do i need to use to find and add an offset delay?You should use the tools in REW to find and apply the delay offset for measurements, using the same offset for all measurements will preserve their relative timing.
I'm not sure whether you are using "speakers" to mean individual drive units or complete loudspeakers. If you are measuring 4 different loudspeakers it will be the same if the speakers are the same type and in the same position relative to the microphone. If you are measuring individual drive units in a single enclosure you should use the same offset for all the measurements, assuming your mic is placed where you expect the drivers to acoustically integrate. In that case best using the tweeter measurement to estimate the delay figure.I had 4 measurements of 4 speakers. Speakers in a speaker enclosure. The microphone is always in one position. Will the delay offset be different for each measurement?
The Estimate IR Delay button, as explained in post #9, using the "Shift and update timing offset" button on the result. You can also manually determine a figure using the "Adjust t=0" controls while looking at the effect on the phase response, and enter the adjustment in the timing offset (or add it to any existing offset) afterwards.Which tool do i need to use to find and add an offset delay?
It concerns also my case? When the microphone is in front of tweeter, and its and others speakers measurements make from one position, from one point? Thus the distance from a microphone up to tweeter is not equal to distance from a microphone up to the midrange and up to the others speakers.using the same offset for all measurements will preserve their relative timing
The total variation in the delay figures across all 10 measurements is 2.7 us, to express that as a distance sound travels it is just under 1 mm. You consider that a large variation in a measurement made at 2.5 m? And that is despite some of the measurements being made in the presence of significantly higher background noise than others and all the measurements suffering from high background noise levels at 2.7 kHz and its harmonics. It looks like very good performance to me.Two files contain 10 measurements made under the same conditions after 1 minute. This is about floating delay.
The distances to the drivers will not be the same when you listen either. If you are using 2.5 m as the measurement distance because that is the distance at which he drivers should integrate then make the measurement with the mic so that it aligns with the intended listening position height on the speaker.It concerns also my case? When the microphone is in front of tweeter, and its and others speakers measurements make from one position, from one point? Thus the distance from a microphone up to tweeter is not equal to distance from a microphone up to the midrange and up to the others speakers.