Seeking views on a room acoustic issue that I’ve been experimenting with. “ Why is it so” question!

 

My listening room (9m*5m) has been undergoing a bit of furniture movement last week. Since, installing and placing the Kallax Shelves and CD storage boxes on the side wall (after removing Isobariks, Sonabs and 3Naim amplifiers in boxes) I had to resolve a “ clangy” SQ- a higher frequency rattle. Eventually resolved that with a temporary solution using a polyester batt placed over the plastic cd storage boxes.

 

The more intriguing one has been the impact of 4 stacked polyester batts that I had put centrally between the speakers some time back. Decided to remove them- tidying up- more to get them “out of the way” rather than any acoustic reason. The impact was easily discernible.

I noticed that there was a significant change to the sound presentation. Still very nice - Leaner, crystal clear, sound stage flatter, beautiful tone, but lacking in bass weight and scale that I was used to.

 

Decided to put just one batt back in same orientation/position as per photo to see if I could restore the bass and scale. It did that, but added a bit more bloom ( “thickness”) to voice and instruments that took away a bit from the “without batt” presentation. 

Anyway, decided to change orientation of batt 90 deg as per photo. Wow thepresentation was amazing 3D, bass weight in particular , body and scale and ambience, emotion of voice. It filled the room with sound. Ended up long night of vinyl- Joni Mitchell, Archie Roach (4 LPs!), Bach cantatas and a Chopin Piano Concert Pollini. All the same effect holographic and “visual”. A 1966 recording of a Janet Baker Bach cantata that I’ve played regularly on systems since I purchased it in the 1970s was spell binding. Huge performance stage and presence!

 

Now, assuming it was the effect  of the position and impact ( partial absorption) of that polyester batt and no other coincidental impact, what is happening at that position?

 

I assume, that being a part dipole speaker, that reflections of the back wall/ screen and front (from toed in) speakers are interacting at that point. Anyway would be good to have your postulations!

 

Edited November 16, 20223 yr by vivianbl
Extra informative

On 16/11/2022 at 5:29 PM, vivianbl said:

Now, assuming it was the effect  of the position and impact ( partial absorption) of that polyester batt and no other coincidental impact, what is happening at that position?

very unlikely 1 batt could have that impact - cognitive bias?

10 hours ago, almikel said:

very unlikely 1 batt could have that impact - cognitive bias?

Do you mean I have high expectations about the impact of the batt and had my high expectations realised! So It’s not real, my brain/ thinking is the cause? 😊

 

To be serious, that batt position change is not just one change, but could be seen as an end result of many changes in tuning/ voicing the room. Speaker positioning, isolation, range of room treatments etc. Sometimes small changes in this environment can have a significant impact. 

 

By the way, my wife has the same cognitive bias!😱

I'd tend to agree with Mike regarding the single panel making a difference, and if there is a difference it likely won't be in the bass region as a single 4" (?) panel's orientation laying on the floor shouldn't have much effect on the bass. Any audible difference in the bass region will be easily measurable if you have the means to do so.

But if it sounds good, stick with it

42 minutes ago, jamiebosco said:

I'd tend to agree with Mike regarding the single panel making a difference, and if there is a difference it likely won't be in the bass region as a single 4" (?) panel's orientation laying on the floor shouldn't have much effect on the bass. Any audible difference in the bass region will be easily measurable if you have the means to do so.

But if it sounds good, stick with it

Thanks.

Yes, the polyester batt is about 4”. Not sure of it’s acoustic measurements, but wouldn’t expect to have the bass impact that I’m hearing, hence my query as to what else could be causing it. I’ve discounted “ cognitive bias”  as one of the causes though!😂

 

I haven’t done any room measurements, but have done a lot of trial/ experimentation of room tweaks and have got a sense of how the room works.
I will stick to it as it was a no cost intervention and really enjoying the music, but curious to the reason for the SQ effect. 
 

I’ve been ready hearing lately about the use of multiple subwoofers, not to improve/ augment the bass output from speakers, but to cancel bass nodes in the room!🤷🏽‍♂️

The only way to find out the real effect is to measure the room "as-is" and with the batt in place. That would end the debate quickly

But it would also help to work out what treatments might be used in addition to what you already have.

3 hours ago, vivianbl said:

Thanks.

Yes, the polyester batt is about 4”. Not sure of it’s acoustic measurements, but wouldn’t expect to have the bass impact that I’m hearing, hence my query as to what else could be causing it. I’ve discounted “ cognitive bias”  as one of the causes though!😂

 

 

I’ve been ready hearing lately about the use of multiple subwoofers, not to improve/ augment the bass output from speakers, but to cancel bass nodes in the room!🤷🏽‍♂️

Yeah the 4" thick panel flat on the floor would do little under 400Hz or so

 

Multiple subs is the best way (IMHO) to get a nice smooth bass response

 

Below is a SNA forum members room response, the RED, GREEN and BLUE traces are his 3x  subwoofers measurements around the room, none of them have a great individual response,some are smooth down low,but uneven in the midbass (and vice a versa)...but their time aligned combined response (the top BLACK trace) is pretty smooth even with zero EQ at this point