AVS Forum banner

26381 - 26400 of 29658 Posts

·
Registered
Joined
·
2,379 Posts
The red line is both subs together. Green is the S3000i and the blue is the S3600i. Why do i get a dip around 70hz when playing both?
Typically such a dip is due to the subs destructively interfering with each other.

You can try flipping the phase/polarity on one of them.
 
  • Like
Reactions: galonzo

·
Registered
Joined
·
28,981 Posts
In your opinion, what is the easiest way to measure a room to find its actual mode frequencies and their corresponding null locations?
Keep in mind that modes have nulls and peaks. If you'll looking for the actual frequency of the 2nd width mode (as opposed to the estimate from a mode calculator), remember that it nulls at the quarter points but peaks at the side walls & midpoint of room width. Place a sub in a corner, sit at the MLP and use a tone generator to play frequencies a few Hz on either side of the estimated 2nd width mode frequency. You'll know when you hit the actual frequency because the peak won't be subtle, and moving your head side to side will make the peak appear & disappear. Once you know the actual frequency, you'll be able to walk across the room and find the nulls much quicker.
I fear that playing a single tone for a prolonged period of time (as opposed to a sweep or playing pink noise) could cause some damage to the sub or speaker.
Not at normal listening levels. It isn't like you're playing it at 130B for several hours.
 

·
Registered
Joined
·
533 Posts
Keep in mind that modes have nulls and peaks. If you'll looking for the actual frequency of the 2nd width mode (as opposed to the estimate from a mode calculator), remember that it nulls at the quarter points but peaks at the side walls & midpoint of room width. Place a sub in a corner, sit at the MLP and use a tone generator to play frequencies a few Hz on either side of the estimated 2nd width mode frequency. You'll know when you hit the actual frequency because the peak won't be subtle, and moving your head side to side will make the peak appear & disappear. Once you know the actual frequency, you'll be able to walk across the room and find the nulls much quicker. Not at normal listening levels. It isn't like you're playing it at 130B for several hours.
Thank you for that feedback Sanjay, much appreciated.
Last night while on my quest to learn more about the room and how it's 6 surfaces are affecting what I hear, I ran across another process suggested here by Bob Golds:
https://www.bobgolds.com/Mode/ETF25Tests/HowToFindModesWithEtf.htm

It's a tedious process but it could help me figure out where the nulls have shifted to if they are not exactly at the predicted locations.
 

·
Registered
Joined
·
28,981 Posts
Last night while on my quest to learn more about the room and how it's 6 surfaces are affecting what I hear...
For a single row of listeners (or multi-row with one important row), I would not give equal priority to all modal axes. With all the listeners being roughly the same ear height AND same distance from the front wall, height mode problems and length mode problem will be consistent across all seats. The biggest inconsistency will be across the width of the room, where seats can end up in peaks & nulls for the same frequency. So, when it comes to subwoofer placement, the main 2 surfaces I'd be worried about are the left & right side walls.
 

·
** Man of Leisure **
Joined
·
22,890 Posts
Always analyze low frequency measurements without any smoothing.
 
  • Like
Reactions: galonzo and IAH

·
Premium Member
Joined
·
4,592 Posts
But does psychoacoustic smoothing give any indication of real world results?
For comparing A/B listening tests or seeking to fit a target curve, I'd say yes. For diagnosing room problem with the bass below 300 Hz, especially below 100 Hz or so with sub placement, I'd agree with Jerry that 1/48th or better yet no smoothing is the way to go.
 
  • Like
Reactions: galonzo and IAH

·
Registered
Joined
·
1,471 Posts
So finally I have made my first measurement after repositioning my speakers and a refreshed Audyssey run:



Any thoughts?
 

·
Registered
Joined
·
1,471 Posts
I've seen that reported a couple of times against macOS 10.14. One user said that it stopped after updating to 10.14.3.


I use REW with the MacBook Pro and I don’t recognize this.
 

·
** Man of Leisure **
Joined
·
22,890 Posts
So finally I have made my first measurement after repositioning my speakers and a refreshed Audyssey run:



Any thoughts?
Both the sub response and the waterfall measurements are best shown 15-300Hz. The response measurements look pretty good.
 

·
Banned
Joined
·
361 Posts
So finally I have made my first measurement after repositioning my speakers and a refreshed Audyssey run:



Any thoughts?
Frequency response looks flat enough, but the waterfall could indicate some serious reflection problems.
Do you like such an extremely sharp sound? Don't prefer x-curve like smoothness watching movies?

Could you please post the ETC and RT60 graphs from the center speaker?

Waterfall: please extend the z-axis (duration) until 1000 ms.
 

·
Registered
Joined
·
1,471 Posts
Frequency response looks flat enough, but the waterfall could indicate some serious reflection problems.

Could you please post the ETC and RT60 graphs from the center speaker?

Waterfall: please extend the z-axis (duration) until 1000 ms.


Thanks for looking at the graphs, you too AustinJerry!

The measurement was done with the CC and the subs (crossover 80hz) together by the way. Do you want to see the center only? If so, I should take another measurement again, which I can do next week.

The other graphs I can look in to tomorrow.
 

·
Registered
Joined
·
1,471 Posts
@Skinfax1:

since you’ve edited your post, this is the way my four Klipsch RP-280F’s sound in my room and I fell in love with the details they reveal! Beautiful! But yes, I’ve raised the subwoofers with 5db overall which gives a sort of ‘house curve’ and a crossover at 100hz. That was done after I posted these screens. Sounds more natural and impactful.
 

·
** Man of Leisure **
Joined
·
22,890 Posts
Thanks for looking at the graphs, you too AustinJerry!

The measurement was done with the CC and the subs (crossover 80hz) together by the way. Do you want to see the center only? If so, I should take another measurement again, which I can do next week.

The other graphs I can look in to tomorrow.
No, I think showing center+subs is a good measurement. It is easier to assess the frequency response for the low frequency region by restricting the horizontal axis to show 15-300Hz, with no smoothing. You can do that for future graphs.

And the waterfall is used to assess bass ringing in the low frequencies, so restricting the measurement 15-300Hz is more appropriate. After all, what does it mean to look at bass resonance at 20,000Hz?

And I completely disagree with @Skinfax1–the water fall is typically displayed with a time window of either 450ms, or 600ms. 1,000ms will mask any ringing issues you might have. If you were kind enough to re-post the waterfall graph 15-300Hz we could provide better feedback for you.
 
  • Like
Reactions: ahblaza

·
Banned
Joined
·
361 Posts
@AustinJerry
:eek:
Even the 4 kHz are totally truncated at 300 ms in that room. It must be extended to see anything useful in that echo chamber.
 

·
Banned
Joined
·
361 Posts
@Skinfax1 :

since you’ve edited your post, this is the way my four Klipsch RP-280F’s sound in my room and I fell in love with the details they reveal! Beautiful!
In rooms with bad acoustics clarity is low and people tend to compensate by boosting the high treble (or they prefer boosted treble, because lower treble and the midrange are a reverberated mess). But that's even more damaging to the ears.
Ofcourse you can do with your ears what you like, but these threads are here to educate people. I'd be careful watching movies with 12 dB louder high treble than intended - maybe even close to reference levels.
What makes it worse: the very long decay times you have in the treble range means a conservation of energy - effectively it covers transients and works like an increase of loudness.


How big is that room?
 
26381 - 26400 of 29658 Posts
Top