Passive Time Alignment

[merlin el mago]

Now two loudspeaker (stereo) measured in listening point phase and FR smoothing 1/1 measurements without any driver gated, what about the phase now, it seems OK?

 

[mark100]

Now two loudspeaker (stereo) measured in listening point phase and FR smoothing 1/1 measurements without any driver gated, what about the phase now, it seems OK?

Looking good Merlin !
Way to hang in untill getting successful measurements

 

[merlin el mago]

Thanks Mark, do you think is necessary the passive time alignment?

 

[plasnu]

Thanks Mark, do you think is necessary the passive time alignment?

I have an a along time aligned Altec 604 type speaker (UREI 813). I'm convinced. I think I can find the measurement somewhere.

 

[merlin el mago]

What do you do Physical or Electrical?

 

[plasnu]

What do you do Physical or Electrical?

Network schematics.

http://www.jblproservice.com/pdf/UREI Time Align Series/813C-L,R.pdf

 

[merlin el mago]

I think coaxial driver are time aligned by nature. I didn't say any electrical time alignment in the xover schematic.

 

[GM]

Only if designed this way and historically many aren't, though no experience with modern designs, so maybe times have changed.

GM

 

[merlin el mago]

It's an interesting design.

 

[merlin el mago]

What's the xover part that do the alignment?

 

[merlin el mago]

Looking at the IR of each driver result at 50cm from axis driver withou xover:

Seas Millenium: Starts at 5.896mS
Scan Speak: Starts at 6.167mS
SBA: Starts at 6.083 ms

The driver with more delay is the midwoofer SS so I will take as reference and only delay the tweeter & the woofer.

Seas Millenium: Difference to delay 0.271ms
SBA: Difference to delay 0.084ms

One of the most widely referenced reports of the audibility of group delay is:

Blauert, J. and Laws, P "Group Delay Distortions in Electroacoustical Systems"
Journal of the Acoustical Society of America
Volume 63, Number 5, pp. 1478-1483 (May 1978)

Blauert and Laws report approximately the following thresholds for audibility:

Frequency Threshold of Audibility
8 kHz 2 msec
4 kHz 1.5 msec
2 kHz 1 msec
1 kHz 2 msec
500 Hz 3.2 msec

According to this I don't need to make any kind of phase alignment?

 

[plasnu]

I think coaxial driver are time aligned by nature. I didn't say any electrical time alignment in the xover schematic.

Time alignment is done in crossover as you see the schematics.

 

[merlin el mago]

Time alignment is done in crossover as you see the schematics.

I didn't see any electrical time alignment in the xover schematic, could you point me where is located in the schematic?

 

[Juhazi]

Merlin, what is important is that delay/phase alignment is matched/controlled at and around crossover frequency in a multi-way speaker. This is critical for symmetrical crossovers, but there are other types too

Blauert et al. study doesn't apply to this, group delay is a different thing.

 

[Juhazi]

A nice paper http://users.spa.aalto.fi/mak/PUB/AES124-000056.pdf
but perhaps LR32 is quite extereme, so is 700th order FIR! More conventional LR12 or LR 24 roll phase less, but have greater demand for wide symmetric overlap.

 

[merlin el mago]

Attached sims with Xsim, one whit electrical phase alignment & the other without. What do you think, I guess is better with phase alignment?

N.B. First left whit electrical phase alignment, second right whitout electrical phase alignment.

 

[plasnu]

I didn't see any electrical time alignment in the xover schematic, could you point me where is located in the schematic?

If you separate phase alignment from time alignment, you're correct. It is a phase alignment. I was in the same camp as you before, but now, I do think it's not really meaningful to separate them, although I still feel I can sleep better with precise time alignment 🙂.

 

[plasnu]

Attached sims with Xsim, one whit electrical phase alignment & the other without. What do you think, I guess is better with phase alignment?

N.B. First left whit electrical phase alignment, second right whitout electrical phase alignment.

Please show us the step response. Unless you want to have some kind of vintage alike sound, phase aligned speaker is more versatile for many different kind of music including dense orchestral composition, in my experience.

 

[TNT]

Two things can be phase aligned but not time aligned. But not vice versa.

//

 

[kimmosto]

Here's a good explanation on how to make gated measurements in ARTA and also how to save minimum phase plots:

That paper is trash in this topic because single channel measurement and minimum phase extraction are not able to capture timing and phase differences.