Comment for JWL on SBIR

0 Members and 1 Guest are viewing this topic. Read 391 times.

Mike in NC

Comment for JWL on SBIR
« on: 12 Jul 2017, 03:05 am »
I enjoyed your recent piece on room acoustics in the GIK newsletter. I didn't find an easy way to comment directly.

You mentioned that SBIR (or Allison effect) problems are typically related to the distance from speaker (woofer) to the front or side wall of the listening room. I would point out that the classic, and a very common, issue is the distance from woofer to the floor. As I understand it, a response dip is expected at the frequency for which this is the 1/4 wavelength distance. I assume this is one reason that many recent floor-standing speakers have multiple woofers at differing distances from the floor.

poseidonsvoice

  • Full Member
  • Posts: 3139
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Comment for JWL on SBIR
« Reply #1 on: 12 Jul 2017, 10:42 am »
I enjoyed your recent piece on room acoustics in the GIK newsletter. I didn't find an easy way to comment directly.

You mentioned that SBIR (or Allison effect) problems are typically related to the distance from speaker (woofer) to the front or side wall of the listening room. I would point out that the classic, and a very common, issue is the distance from woofer to the floor. As I understand it, a response dip is expected at the frequency for which this is the 1/4 wavelength distance. I assume this is one reason that many recent floor-standing speakers have multiple woofers at differing distances from the floor.

Indeed correct. There are many examples of that now. Salk, KEF Blade, Aerial Acoustics model 8, GR Research, Legacy,etc...come to mind. That being said you'll find that it's still not completely eliminated. The effect is minimized which is always good but you still need to treat your corners +/- side wall too unfortunately (nice room pics in your gallery btw!). And...most of these speakers, you need to pull them away from the front wall for best imaging/staging anyway. It's tricky to get right but if you don't have  +/- 10 dB swings that's already a plus.

As an aside, I do recall way back when that the NHT 3.3 was shaped as it was to create a "corner" for the side mounted 1259 woofer in order to minimize the SBIR/Allison effect as much as possible. That being said there is still that "dip" :



https://www.stereophile.com/images/archivesart/N33fig2.jpg

I find that I have to be careful with interpreting the measurements from Sphile and the NRC. The NRC is anechoic so you won't see the effect. With Stereophile I look and see if it was an in room or quasi anechoic measurement. With the in room measurement I can trust if the loudspeaker design minimizes the SBIR effect intrinsically or does not (as long as it was setup right and there aren't large absorbers in the setup). With the quasi anechoic I may not see it at all but it still might be there.

Just a note to myself...I guess there is nothing like having the speakers in my own room and doing the measurements.

And JWL, your Audiogeekery blogs/articles are a treat I quite agree!

Best,
Anand.
« Last Edit: 12 Jul 2017, 02:12 pm by poseidonsvoice »

Mike in NC

Re: Comment for JWL on SBIR
« Reply #2 on: 12 Jul 2017, 01:59 pm »
@poseidonsvoice: Thanks!  A couple of minor comments:

(1) On measuring, I agree. I can calculate room effects until I'm blue in the face, but I'm always surprised when I look at the measurements taken in my room.

(2) When Stereophile shows graphs with comparative measurements (say, in AD's room vs. JA's room), they typically reveal that JA is better at placing speakers than his reviewer. They also suggest that some reviewers don't care much about getting accurate tonal balance. Knowing that helps me put their reviews in perspective.

poseidonsvoice

  • Full Member
  • Posts: 3139
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Comment for JWL on SBIR
« Reply #3 on: 12 Jul 2017, 02:12 pm »
@poseidonsvoice: Thanks!  A couple of minor comments:

(1) On measuring, I agree. I can calculate room effects until I'm blue in the face, but I'm always surprised when I look at the measurements taken in my room.

(2) When Stereophile shows graphs with comparative measurements (say, in AD's room vs. JA's room), they typically reveal that JA is better at placing speakers than his reviewer. They also suggest that some reviewers don't care much about getting accurate tonal balance. Knowing that helps me put their reviews in perspective.

Very wise words. They don't even have 1/2 the room you have! And some are real head scratchers  :scratch:, i.e. AD and HR.

https://www.stereophile.com/content/reviewer-video-profile-herb-reichert

Best,
Anand.

JWL.GIK

  • Industry Participant
  • Posts: 82
    • GIK Acoustics
Re: Comment for JWL on SBIR
« Reply #4 on: 12 Jul 2017, 02:25 pm »
Hi Mike,

Thanks for reading! I appreciate it. I'm glad you found the article interesting and/or useful. Of course you are quite correct that any boundary will produce SBIR.

For those not clear about the article in question, it was this two-parter:
http://www.gikacoustics.com/room-setup-speaker-placement-201-part-one/
http://www.gikacoustics.com/room-setup-speaker-placement-201-part-two-subwoofers/

Also, there is another article on SBIR at the GIK site, I didn't want to go into too much detail in the speaker placement article so it wasn't redundant. :-)
http://www.gikacoustics.com/speaker-boundary-interference-response-sbir/