ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Creating FIR filters -- How to for novices?  (Read 2918 times)

Michael Jaspers

  • Newbie
  • *
  • Offline Offline
  • Posts: 11
Creating FIR filters -- How to for novices?
« on: July 17, 2014, 11:58:03 am »

I would like to know if it is possible or even advisable for a novice like me to create and load FIR filters for Renkus Heinz STX6 speakers into a BSS London BLU-*00: so I am posting this for help from the pros:

I have been asked to help out with a problem with the sound in the PAC at the university I attended by a former professor (and now, friend).  I measured the system first and also documented what equipment was deployed. 

Processing is BSS London BLU, Speakers are Three/Cluster RH STX-6/46(non powered version) in LCR configuration (assumed that the contractor rotated the horns), Amplification is Marcotech "i" series.

The STX-6 has a passive crossover in the cabinet at 1500 Hz and there is an active crossover apparently at 500 Hz as well.

It seems to me that the crossover slope is way too high and obviously there needs to be some EQ done, but I got to thinking about the crossover at 500 Hz and if I could maybe get the phase trace to be flatter until the transition to subwoofer.  (System is used for drama, opera, and orchestral music--occasionally for a folk/rock group)

However, The BLU series of processor does not have second-order All Pass filters. So that leaves me with the possibility of either doing an "impulse" alignment at 500 Hz or using FIR crossover at 500 Hz.  I've done a bit of reading and it seems that delay for symmetrical FIR crossovers is (# of filter coefficients(poles?)/2 = sample length delay?) so a 24 dB/oct filter would have a 2 sample delay at 48000 Hz (sampling rate of processor) at 500 Hz?

If the delay is acceptable, FIR seems like a good option, but I do not know how to create a FIR filter.  BSS says that I can upload a CSV file...

Whether I do a regular crossover via matching the phase traces, impulse alignment, or using a FIR filter, I would still like to know how to use FIR tools, so any help is appreciated. 

The attached image is screen shot from the LEFT array:
« Last Edit: July 17, 2014, 02:23:42 pm by Michael Jaspers »
Logged

David Sturzenbecher

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1446
    • Sturz Audio
Re: Creating FIR filters -- How to for novices?
« Reply #1 on: July 18, 2014, 08:26:52 am »

I would like to know if it is possible or even advisable for a novice like me to create and load FIR filters for Renkus Heinz STX6 speakers into a BSS London BLU-*00: so I am posting this for help from the pros:

I have been asked to help out with a problem with the sound in the PAC at the university I attended by a former professor (and now, friend).  I measured the system first and also documented what equipment was deployed. 

Processing is BSS London BLU, Speakers are Three/Cluster RH STX-6/46(non powered version) in LCR configuration (assumed that the contractor rotated the horns), Amplification is Marcotech "i" series.

The STX-6 has a passive crossover in the cabinet at 1500 Hz and there is an active crossover apparently at 500 Hz as well.

It seems to me that the crossover slope is way too high and obviously there needs to be some EQ done, but I got to thinking about the crossover at 500 Hz and if I could maybe get the phase trace to be flatter until the transition to subwoofer.  (System is used for drama, opera, and orchestral music--occasionally for a folk/rock group)

However, The BLU series of processor does not have second-order All Pass filters. So that leaves me with the possibility of either doing an "impulse" alignment at 500 Hz or using FIR crossover at 500 Hz.  I've done a bit of reading and it seems that delay for symmetrical FIR crossovers is (# of filter coefficients(poles?)/2 = sample length delay?) so a 24 dB/oct filter would have a 2 sample delay at 48000 Hz (sampling rate of processor) at 500 Hz?

If the delay is acceptable, FIR seems like a good option, but I do not know how to create a FIR filter.  BSS says that I can upload a CSV file...

Whether I do a regular crossover via matching the phase traces, impulse alignment, or using a FIR filter, I would still like to know how to use FIR tools, so any help is appreciated. 

The attached image is screen shot from the LEFT array:

Are you a member of Syn-Aud-Con?  If not you should be.  And in one of their member blogs there is a "how to" on "practitioner level FIR filters".  Just stepping through it on my own...With a BLU-80 turned on a few lights.
Logged
Audio Systems Design Engineer
Daktronics, Inc.
CTS-D, CTS-I
AES Full Member

David Sturzenbecher

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1446
    • Sturz Audio
Re: Creating FIR filters -- How to for novices?
« Reply #2 on: July 18, 2014, 08:30:13 am »

Only similarly related...The boys (and girls) down in Foothill Ranch know a thing or to about making speakers, and are really good it at.  I can guarantee you that more then a coffee break was spent on the crossovers for these boxes.  That being said, I doubt FIR was an option when they were rolling the tunings for this box.
Logged
Audio Systems Design Engineer
Daktronics, Inc.
CTS-D, CTS-I
AES Full Member

Michael Jaspers

  • Newbie
  • *
  • Offline Offline
  • Posts: 11
Re: Creating FIR filters -- How to for novices?
« Reply #3 on: July 18, 2014, 04:13:46 pm »

Are you a member of Syn-Aud-Con?  If not you should be.  And in one of their member blogs there is a "how to" on "practitioner level FIR filters".  Just stepping through it on my own...With a BLU-80 turned on a few lights.
Thanks, David; I will look into SynAudCon.
Logged
Pages: [1]   Go Up
 


Page created in 0.04 seconds with 22 queries.