HOLMImpulse: Measuring Frequency- & Impulse-Response - Page 50 - diyAudio
Go Back   Home > Forums > Design & Build > Software Tools

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th October 2009, 07:47 PM   #491
tms0425 is offline tms0425  United States
diyAudio Member
 
Join Date: Oct 2006
Location: Ft. Wayne, IN
Quote:
Originally Posted by askbojesen View Post
Still a problem?
Works for me
  Reply With Quote
Old 15th October 2009, 08:03 PM   #492
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by askbojesen View Post
How do you smooth?

Please reveal your formulas, so I can implement your method
I average the magnitudes of the frequency bins as a weighting filter is swept through the frequency response data. Its not very efficient and I'd like a better method, but it does work.

I plan to try yours as well.

Last edited by gedlee; 15th October 2009 at 08:06 PM.
  Reply With Quote
Old 15th October 2009, 08:05 PM   #493
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by Key View Post
I just am not sure about a lot of things which people claim are audible. My system seems to be immune to all types of things most experts claim should be audible. But I am still testing so no conclusions on group delay and diffraction effects yet.
I find that most things that the "experts" claim are audible aren't. But then most of their tests for audibility of things aren't sufficiently well controlled to be useful for making any kind of judgement. My tests are all double blind with a lot of subjects.
  Reply With Quote
Old 15th October 2009, 08:24 PM   #494
diyAudio Member
 
Join Date: Mar 2003
Location: Denmark, Copenhagen
Quote:
Originally Posted by gedlee View Post
I average the magnitudes of the frequency bins as a filter is swept through the frequency response data. Its not very efficient and I'd like a better method, but it does work.
I plan to try yours as well.
Isn't this what is called stepped sine method?

What when you measure your polar-patterns using impulse responses from HOLMImpulse?

----------
Well, I do not claim to have the correct smoothing formula. I now have 4 methods:
A. No smoothing, no window
B. Time-window
C. Absolute log-smoothing (I use this for digital room-adaption)
D. Complex log-smoothing <=> Frequency dependent window

Personally I don't see the advantage of D for correcting speakers (this is my goal) or making room-adaption. A lot of other measurement software implement D in a not flexible and transparent way, so I find it nice to see what I'm doing in the time-domain.

I need to make a careful comparison with pink noise power response and stepped sine.
__________________
Follow your first Impulse with HOLMImpulse

Last edited by askbojesen; 15th October 2009 at 08:28 PM.
  Reply With Quote
Old 16th October 2009, 01:23 AM   #495
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by askbojesen View Post
Isn't this what is called stepped sine method?

What when you measure your polar-patterns using impulse responses from HOLMImpulse?

----------
Well, I do not claim to have the correct smoothing formula. I now have 4 methods:
A. No smoothing, no window
B. Time-window
C. Absolute log-smoothing (I use this for digital room-adaption)
D. Complex log-smoothing <=> Frequency dependent window

Personally I don't see the advantage of D for correcting speakers (this is my goal) or making room-adaption. A lot of other measurement software implement D in a not flexible and transparent way, so I find it nice to see what I'm doing in the time-domain.

I need to make a careful comparison with pink noise power response and stepped sine.
No its not stepped sine, thats different.

I take the impulse response and find the FR, normal FFT. Then I go to a set of log spaced frequencies and at each of those find a weighting function that is 1/N wide - I use a gaussian type of shape. The magnitudes at each of the FFT data point is then weighted by this shape and integrated (summed). This procedure has trouble at LF when the frequency spacing of the data is comparable to the smoothing bandwidth, but works good otherwise.

There is no "absolute" correct method - all measurements of loudspeakers are evolving, but its important to understand how and why they all might differ.
  Reply With Quote
Old 16th October 2009, 01:41 AM   #496
diyAudio Member
 
Join Date: Aug 2003
Location: Santa Cruz, California
Quote:
Originally Posted by gedlee View Post
I take the impulse response and find the FR, normal FFT. Then I go to a set of log spaced frequencies and at each of those find a weighting function that is 1/N wide - I use a gaussian type of shape. The magnitudes at each of the FFT data point is then weighted by this shape and integrated (summed). This procedure has trouble at LF when the frequency spacing of the data is comparable to the smoothing bandwidth, but works good otherwise.
Above a few hundred Hz the ear's critical bandwidth is measurable in logarithmic terms such as fractions of an octave, but below this the critical bands approach constant frequency width the lower you go. Karjalainen et al in JAES (Journal of the Audio Engineering Society) Vol 47 No. 1/2 show a filter structure for speaker correction taking this aural characteristic in mind, which shows improved performance in the lower frequencies.
  Reply With Quote
Old 16th October 2009, 09:59 AM   #497
diyAudio Member
 
Join Date: Mar 2003
Location: Denmark, Copenhagen
Question gedlee 1/N smoothing

Quote:
Originally Posted by gedlee View Post
I take the impulse response and find the FR, normal FFT. Then I go to a set of log spaced frequencies and at each of those find a weighting function that is 1/N wide - I use a gaussian type of shape. The magnitudes at each of the FFT data point is then weighted by this shape and integrated (summed). This procedure has trouble at LF when the frequency spacing of the data is comparable to the smoothing bandwidth, but works good otherwise.
1. When you sum the RF - is it then a complex sum? or do you sum the amplitudes?

2. When you use your weighting function - do you multiply with 1/f to compensate for your equidistant frequencies?
__________________
Follow your first Impulse with HOLMImpulse
  Reply With Quote
Old 16th October 2009, 12:15 PM   #498
breez is offline breez  Finland
diyAudio Member
 
Join Date: Jul 2004
Location: Finland
ARTA manual describes the smoothing methods used by ARTA, which may be of interest to this discussion. Section 2.3. ARTA home
  Reply With Quote
Old 16th October 2009, 12:28 PM   #499
diyAudio Member
 
Join Date: Mar 2003
Location: Denmark, Copenhagen
Default ARTA smoothing vs HOLMImpulse

Quote:
Originally Posted by breez View Post
ARTA manual describes the smoothing methods used by ARTA, which may be of interest to this discussion. Section 2.3. ARTA home
Thanks, ARTA "2.3 Frequency Resolution of DFT and Octave-Band Analyzers"
if ARTA window = BLACKMANN3, then this corresponds to HOLMImpulse amplitude smoothing with N = 1, N = 3

The HOLMImpulse FR makes a calculation for all discrete frequencies, not only the ISO-standard-steps. I might implement an ISO-standard-step FR which will show bars and not a curve.
__________________
Follow your first Impulse with HOLMImpulse
  Reply With Quote
Old 16th October 2009, 12:30 PM   #500
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
I've always been curious as to why not just use a rectangular time window and smooth only the portion outside the window? The part outside the window certainly should not have certain frequency content, and thus the maximum slew rate should be less further down the time scale.
__________________
Hear the real thing!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Measuring Frequency Response MCPete Multi-Way 10 10th February 2009 12:36 AM
Measuring Frequency Response furly Planars & Exotics 1 17th March 2006 06:59 AM
Measuring the frequency response of a mic? mr_push_pull Multi-Way 5 30th August 2004 12:26 PM


New To Site? Need Help?

All times are GMT. The time now is 03:04 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2