Excess Group delay show in overlay possible or maybe can add in future ?

[user44455555]

Hello

I do ramped levels at nearfield with following method.
make microphone distance 5 cm to Woofer. set volume of each Speaker you want test with REW check Levels in measure tab sp that Level - 6 have 95 db . this is at 1 meter 69 db, and Level 3(L3) so it is not so loud but loud enough to show how much group delay change depend on level.

set sweep length to 1 mb set ramped Levels in measure mode 3 measurement -18 db .. -6 db frequency from 35 to 300 hz
After measure switch to GD choose with mouse right click menu generate minimum phase

L2 is 6 db less (63 db)
L1 is 12 db less (57 db)

the short distance is need, to avoid room influence. Keep in mind you can not use much higher level, because the microphone is so near you can get clipping or damage microphone .
for volume of 84 db at 1 meter you get at 5cm 110 db. thats too high for microphone. so keep silent

I think this is correct and no a problem of room influence. there can see in the results that excess Group delay get larger depend on volume in the bass range and i think everybody can do such tests to see if speaker is good. because in stereo left and right speaker play diffrent waves, the group delay jitter on worse speaker between left and right speaker at same frequency. because interaural time delay is used for audio location in brain this give bad stereo image and mud on low bass(kick drum reverb)

the teststeps

in the mdat are also measures from Kali and HS5. the kali have on low volume much more random changes, i did not think it is problem from room. I always notice when hear kali lp6 very loud sound ok. but i want not hear loud.

 

[Keith_W]

I decided some time ago not to respond to any more of your posts because my patience ran out much earlier than John's. You don't seem to learn and you are asking the same question over and over, but in a different form.

1. Please read John's post here as many times as you need until you understand what he said. In particular, do what he suggested in that thread. Create a simulation of two loudspeakers and examine the phase and group delay characteristics of each simulation. Do this:

- Press the "EQ" button
- In the popup window, press the "EQ filters" button

- Scroll all the way to the right. Create a bandpass filter. Here is a speaker simulation with simulated bass and treble roll-off. Do this twice with different values to simulate two different speakers.
- Under "Filter tasks", click "Generate measurement from filters".

- Result: two loudspeaker simulations for you to play with and compare. Try shifting the position of the impulse (t=0) and see what effect that has on the phase graph and group delay.

2. Group delay is the negative derivative of phase, see REW manual. You can think of it as another way to view the phase graph.

3. You need to understand group delay audibility thresholds. see Liski, Makivirta, Valimaki's paper on Audibility of Loudspeaker Group Delay Characteristics or read Toole.
4. Ported speakers have different group delay characteristics compared to sealed speakers. Without googling exactly what speakers you have, it is impossible to comment.

5. There will be minimal ITD (interaural time difference) if the same speaker is used for left and right channels, unless one speaker is defective.

 

[user44455555]

.1. Please read John's post here as many times as you need until you understand what he said. In particular, do what he suggested in that thread. Create a simulation of two loudspeakers and examine the phase and group delay characteristics of each simulation. Do this:

But the frequency response of 1 speaker is same only it play at diffrent levels L1 L2 L3 and get diffrent excess group delay over 1 ms (1000 µsec) diffrence. how can you explain this ?. you can download the mdat and choose spl align to see the FR of L1 L2 L3 levels measure

Also here is the confirm measure that excess phase is frequency response independent, because lots diffrent FR create with EQ but same excess phase(predictet phase in overlay). try out yourself, mdat are here too

U

Post in thread 'Phase unwrap questions'

Friday at 7:33 PM

thanks to your help and hint with try out filters now i understand what excess phase and predicted phase is, because when i EQ the JBL it have same excess phase as the non EQ version . only kali have very diffrent excess phase
So i assume min phase is the result the frequency response of the speaker have if it is min phase. and when show excess phase REW subtract the min phase from the measures phase, and excess phase is the additional phase of the worseness of speakers ?

REW have no overlay for excess phase button, but predictated phase seem do the same. The version i EQ have the same...

• user44455555

and btw when you look at the clarity results with the 5cm measure you can see the ranking too, the most expensive speaker i have the focal is the worst this test and HS5 the small 5 inch is best

There will be minimal ITD (interaural time difference) if the same speaker is used for left and right channels, unless one speaker is defective.

and how many µsec do you mean with minimal ? .

they test it and found

Smallest perceivable interaural time differences - PubMed

It is well-established that the smallest discrimination thresholds for interaural time differences (ITDs) are near 10 μs for normal hearing listeners. However, little is known about the hearing and training status of the test subjects from past studies. Previous studies also did not explicitly...

pubmed.ncbi.nlm.nih.gov

Smallest perceivable interaural time differences​

The average threshold ITD for this condition at the 75% correct level was 6.9 μs for nine trained listeners and 18.1 μs for 52 un-trained listeners.