Speakerplans.com Homepage
Forum Home Forum Home > General > Advanced Discussion
  New Posts New Posts RSS Feed - Linear Phase without FIR
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Linear Phase without FIR

 Post Reply Post Reply Page  <123
Author
Message
corell View Drop Down
Young Croc
Young Croc
Avatar

Joined: 19 August 2013
Location: Berlin
Status: Offline
Points: 1023
Post Options Post Options   Thanks (0) Thanks(0)   Quote corell Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 8:37am
I was not assuming that the graph shown in post 1 was linear phase, as you said, it only appears to be because the scale is logarithmic. the point where gen0me and i disagree is if actual linear phase is "worse" than constant phase or not.
Back to Top
gen0me View Drop Down
Registered User
Registered User


Joined: 20 February 2016
Location: UK
Status: Offline
Points: 391
Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 11:23am
You can figure out phase from gd. You cant figure out gd from phase due to -2kpi that changes across frequencies. You can only shoot it.

Here is whats really on my mind:
For this top:


So according to:

Originally posted by corell corell wrote:

You then just need a "normal" delay

Leru choose best possible delay for phase measurement - top of bandwitch where gd is constant.
Still interpreting it is impractical...

Edited by gen0me - 14 September 2017 at 11:25am
Back to Top
gen0me View Drop Down
Registered User
Registered User


Joined: 20 February 2016
Location: UK
Status: Offline
Points: 391
Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 4:09pm
Actually. Could you show us 3 seperate impulse responses and than combined one?
Back to Top
Jo bg View Drop Down
Registered User
Registered User


Joined: 08 March 2017
Status: Offline
Points: 31
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 5:38pm
Timo, i am so happy you proved me wrong Smile thanks for your research and the helpful blog; i knew your videos with Linea flat phase crossovers but missed the posts you link here!
can't wait to have some time to try this, i hope my xilica has got enough horse power to  deploy all the all pass filters needed, at least for a 1 Khz crossover.
In your experience, assuming the drivers tolerate a 2nd order crossover at that frequency, would this "linear phase through delay & all pass" be useful also at lower frequencies like 180 hz ?

Back to Top
Timo Beckman View Drop Down
Registered User
Registered User


Joined: 09 August 2011
Location: Netherlands
Status: Offline
Points: 128
Post Options Post Options   Thanks (0) Thanks(0)   Quote Timo Beckman Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 12:10am
I did a experiment where i used a FIR on the highs from +/- 1K2 (i think but do not remember exactly)
and because of the latency on a Powersoft X8 when using FIR (+/- 4ms) i can use that latency to correct or better said alter the phase on the low driver (going down from 1K2 to about 63Hz if i remember correctly).
The result looks kind of OK ;-).


But this was just me "geeking" around to see what would happen on that mic position. I would not go as flat on a system as in the screen shot. (the ofax was a bit jumpy so it needed a "little" more work....;-))

The reason is pretty simple and has to do with subs......They will mess up things every now and then. I would try to go more to a single wrap on the low end around the x-vr and then go more gradually down to  0º. Maybe like this next screen shot from a Fulcrum RM25ac.
(this is a point source system no sub in the screen shot and straight out of the box.)
And here's a combination of 2 x RM25ac 2 x RM28ac 1 x FA28ac in a 5.1 surround set-up.
https://timobeckmangeluid.files.wordpress.com/2017/04/5-1-all-on-small-room.png?w=2000 (there where 5 speakers playing during the screen capture).
Here i had to use some AP2 filters to get the low end to work together. The RM25ac starts at 24Hz (high-pass filter somewhere around there and the RM28ac starts at 40Hz also a high-pass filter but at a different frequency and again the same thing on the FA28ac at 45Hz which was no problem with the RM28ac but was with the RM25ac). 

Also a flat frequency respons might not be what you want when you have to push a 99/105dBa.
2nd the phase flat/zero stuff from Lake and Linea is pretty cool but it doesn't mean you'll get a flat phase system because you still have to deal with the driver's respons.

By the way i'm not trying to prove anything just showing some ways to go about measurements.


Edited by Timo Beckman - 17 September 2017 at 12:02pm
The sound will be as good as the band play's
Back to Top
fatfreddiescat View Drop Down
Registered User
Registered User


Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 457
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 7:37am
Hi Timo, thanks for posting, I have been reading your blog although had also missed the posts about ap filters and really appreciate the work you have put in.
Back to Top
Timo Beckman View Drop Down
Registered User
Registered User


Joined: 09 August 2011
Location: Netherlands
Status: Offline
Points: 128
Post Options Post Options   Thanks (0) Thanks(0)   Quote Timo Beckman Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 12:19pm
If i take a look on the screen shot on the opening post:
From about 300Hz to 100Hz it's about 5ms of group/phase delay on that area.
From about 1K to 300Hz it's about 1.42ms (1.43) of group/phase delay on that area.
From about 5K5 to 1kHz it's about 0.22ms of group/phase delay on that area.

You can calculate the group delay via this formula:
(∆Phase/360º)/(∆Frequency) so for the first range 300Hz to 100Hz
(360º/360º)/(300-100)=1/200=0.005 sec would mean 5ms.
If you add 5ms to the synchronization delay within your analyzer the phase would go flat in the range 300Hz-100Hz somewhere in the middle.
I do not see the specific frequency points so i took easy numbers ......(frequency scaling in decay setting is always a bit of a guess for me. I'ld rather set it to ⅓ oct scaling).

(by the way you have to read the frequency points from right to left)


Edited by Timo Beckman - 17 September 2017 at 12:21pm
The sound will be as good as the band play's
Back to Top
LeruSound View Drop Down
Registered User
Registered User


Joined: 27 August 2015
Status: Offline
Points: 96
Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 20 September 2017 at 10:48pm
Back to Top
 Post Reply Post Reply Page  <123
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 11.10
Copyright ©2001-2017 Web Wiz Ltd.

This page was generated in 0.062 seconds.