suck out fixed. i think.

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
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#1
my room designer designed a whole ceiling bass trap into my room. it was 15" deep and covered the whole 21' x 29' ceiling. except for -6- inset 6' x 8' chambers. these chambers had fabric covered vertical openings with Corning 709 fiberglass in the openings. you can see the chambers in the ceiling of my room pictures. the idea was that this bass trap would control the bass; but clearly in retrospect it was a huge mistake. now 11 years later that mistake has been rectified.....finally.

front-1.jpg

4 years ago I did have a contractor remove the fabric panels from 4 of the 6 chambers and glue and screw 3/4" finished maple plywood over these openings; which did improve the bass response. I thought that fixed my issue. I was wrong.

last May, 14 months ago, my speaker designer was here for 2 days to do the final tweaking to my Evolution Acoustics MM7's. when he measured the room he found a fairly wide -12db suck out at 30hz, one that the room dimensions did not logically predict. he strongly suspected that the remaining openings in those center chambers were the likely cause. since the MM7's are so powerful and adjustable, he was able to minimize the effect of the suck out with adjustments, but at the cost of ultimate performance. he did strongly suggest I get those openings covered. he even gave me two sets of settings sheets for the 4 sets of adjustments (2 sets on each bass tower).......one for the 'compensated' adjustments he made, and another for 'flat' adjustments anticipating my getting those openings sealed up.

since last May I have given a good amount of effort into finding a contractor to do that work, but was not successful.

then this spring I went thru the experience with the fabric treatments that really took things up a few notches. I had quite a few people thru the room and the feedback was very positive. I knew that somehow I needed to do this final thing and hopefully that would allow the bass performance that was already amazing to go to the optimal level. I was fully motivated to get this done with my excitement from the big step forward from the fabric treatments.

I realized if I wanted to get this done i had to do this myself.

finally I was able to convince my son (I bribed him by giving him one of my bicycles) to help me do this nasty job. I spent last week buying -3- 4' x 8' sheets of finished 3/4" maple plywood, another 8 foot step ladder (we would be working at 10'-11'), a good quality circular saw, saw horses, and all the other bits and pieces we would need. my son had a 208 mile one-day STP (Seattle to Portland) bike ride on Saturday and did not get home till late, so Sunday morning a spent 2 hours clearing out the room.....everything to the sides....racks moved, tape decks moved. big job. tarp laid. ladders set up. neither of us are carpenters; could we rip the panels without chipping? could we even cut a straight line?

would it actually make a positive difference?

we did not know exactly how we would remove the fabric panels or how they were attached. would we be able to get them out without removing the trim pieces? we did not posses the skills to properly replace the trim.

he showed up around 10:30am and we first removed the 8 deflector panels with in the chambers and then got to work pulling off the fabric panels, 4 per chamber, 8 total. we were able to get them out with considerable caution and effort without disturbing the trim. then we measured and started ripping the sheets and cutting to size. I had a work commitment mid afternoon for 2 hours, and returned. finally about 9 that night we screwed and glued the final plywood sheet. then he left and I spent 2 hours reassembling the room. I'd had a listening visitor from California the previous day (HiFi Guy) and then the previous night I'd had a work dinner till midnight. I'm not a young guy. I was gassed. I tried to listen. was it boomy sounding? if that 30hz -12db suck out was solved to a significant degree that old set-up would cause the lower bass to be boomy. I thought it was boomy but fell asleep right away. the next morning before work I was not yet recovered enough to listen.

finally after work that night I had recovered enough to listen and went thru my digital listening references and the lower bass was clearly boomy, if not quite a bit more energetic sounding. I had spoken to my speaker designer earlier and he said I should shut off the amps in the bass towers and see if it sounded clean. if it did that indicated that the closing of the openings had not likely caused other issues. I did that, went thru my references again, no problem, sounded very clean. so then I turned the bass towers back on and adjusted both the 'bass level' and the 'bass quality' (Q) halfway to the 'flat' positions and listened to the references again. better, less boomy. much more energy. some magical things happening. then I went 3/4 to the flat positions and again listened. now it was a big WOW! everything was now at a whole new reference level. all up and down the frequency range. a whole new level of coherence and naturalness. vocals were superb sounding. much more holographic. bass impact a couple orders of magnitude better. so I just listened late until early morning Tuesday and again after not much sleep in the morning. I was stoked.

that night I first listened as it was; then found a good cut and moved the 'bass quality' the last little bit to the flat position. clearly better. then I moved the 'bass level' the last little bit to the flat position and it was super clean and right. it sounds perfect to me now; I've been listening for 2 days now to it and I'm just beside myself. as good as it had been; it's not only much better but much different than even Saturday night. what is so crazy to my mind is how much different vocals and the mid range is simply by eliminating a 30hz suck out. it was very interesting hearing how much detail had been covered by those adjustments which were pegged to cover the suck out when taken to flat all that detail jumped out.

the MM7's are now fully unleashed and are something to behold!

how close to absolutely flat is it? don't know. I hope it can get better from here.....but maybe not. is the suck out all the way gone? once I measure it I may or may not post it. we all know how much I love graphs.:eek:

I suppose I have a persecution complex posting about discovering my personal mistakes. I know from time to time that comes back to haunt me when ner-do-wells want to give me some crap. but so what. I feel that these sort of experiences contribute to the collective knowledge. and one has to be open to learning and going farther down the road.

my goal 11 years ago with my efforts was to get the room and system out of the way of the music; I think I've essentially done that finally.

oh and btw, this job cost me about $250 in materials and I did acquire approx. $450 worth of tools and a ladder. I was going to give the bike to my son anyway but he did not know that. so between the fabric and this job about $500-$600 and the effect is off the charts.
 
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jfrech

VIP/Donor
Sep 3, 2012
1,580
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Austin
#3
Mike, I know from my experience, the room is a HUGE deal. So were the chambers above the angled deflectors? And the deflectors stayed I assume...

Congratutions, it's always great when the project is over and you get to relax and love the sound :) !!
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
2
0
Dallas, Texas
#4
Mike,
The null is not the ceiling. It's too close to the seated position and speakers to null at that frequency. Also, boundary nulls (SBIR or Allison effect; all same thing but different names) are always characterized by a sharp phase reversal at null center frequency and narrow Q null. That doesn't sound like what you are describing. It is possible that woofer integration may not be smooth and that could cause a wider Q null more consistent with what you are describing.

But there's no way to really know unless you measure it. You can measure the reflection using the ETC function in REW. You can also look at SPL and phase. If there's no reflection in ETC which matches up with a boundary in your room, then the only other possibility is a woofer integration problem. IME, speaker designers aren't best at diagnosing room issues or even bass integration issues. I mean that for all speaker manufacturers.

It would be much faster and much more certain to measure using REW.
 
Last edited:

rbbert

Active Member
Dec 12, 2010
3,414
3
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Reno, NV
#5
Is the picture above the way your room looks now?
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
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679
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#6
Mike, I know from my experience, the room is a HUGE deal. So were the chambers above the angled deflectors? And the deflectors stayed I assume...

Congratutions, it's always great when the project is over and you get to relax and love the sound :) !!
thanks John. I am very relieved that my efforts were rewarded with the payoff of better sound. it had been on my mind a long time and sometimes you do something on faith. if it would have caused other problems and I would have had to somehow un-do gluing and screwing those panels shut that would have really ruined my day.

and yes; those angled defectors went right back up. you can see in the picture from last week the grey color of the fabric panels which were removed and replaced with the 3/4" maple ply on Sunday. I'm really a little surprised that two amateurs (one smart and handy....not me) were able to do a project like that and have it turn out right and looking good. no injuries or collateral damage.....lots of potential for same.
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
7,576
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#7

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
7,576
679
113
#8
Mike,
The null is not the ceiling. It's too close to the seated position and speakers to null at that frequency. Also, boundary nulls (SBIR or Allison effect; all same thing but different names) are always characterized by a sharp phase reversal at null center frequency and narrow Q null. That doesn't sound like what you are describing. It is possible that woofer integration may not be smooth and that could cause a wider Q null more consistent with what you are describing.

But there's no way to really know unless you measure it. You can measure the reflection using the ETC function in REW. You can also look at SPL and phase. If there's no reflection in ETC which matches up with a boundary in your room, then the only other possibility is a woofer integration problem. IME, speaker designers aren't best at diagnosing room issues or even bass integration issues. I mean that for all speaker manufacturers.

It would be much faster and much more certain to measure using REW.
I'm sure you know better than my speaker designer. and I'm not claiming any specific measured result. only that the audible result of closing the openings in the ceiling bass traps was the deep bass being quite boomey where it had not been so, and added energy to the music. then when I turned the bass tower adjustments to what the speaker designer said was the 'flat' position, the overall performance of the system increased dramatically.

where the openings to that humongous 21' x 29' x 15" bass trap were evidently was not an issue. it was the volume of that trap and it's effect of allowing the suck out. (my SWAG).

according to my room designer the suck out was measurable everywhere in the room; not just at the listening position.
 
Last edited:

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
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679
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#9

PeterA

Well-Known Member
Dec 7, 2011
5,552
447
83
North Shore of Boston
#10
Mike, great read and congratulations on the results. Your enthusiasm comes through in spades. I commend you for getting your hands dirty and trying to solve the problem yourself. Sometimes, it is the only way. And as a father of two, I am sure there was no small feeling of joy in doing this project with your son.

This story is consistent with what I have been discovering myself. Within one's budget, he reaches a point where improvements in sound may mean relatively large expenses in new components. But with sufficient curiosity, effort and motivation, additional gains can be had through fine tune and slight tweaks to the system and room. These gains can be dramatic and cost very little relative to the overall system cost. And they can be extremely rewarding and contribute to a significantly better emotional connection to the music. Member Al M. is experience a similar improvement as described on his system page.

These kinds of threads, and the "One Amigo" thread that Steve just posted, make this forum so enjoyable. Thanks Mike for sharing.
 

RBFC

WBF Founding Member & Super Moderator
Apr 20, 2010
5,127
7
38
Albuquerque, NM
www.fightingconcepts.com
#11
I'm thrilled for you, Mike! Anytime someone with a system at your level can experience a satisfying "leap" in performance, that's worth celebrating. That you did it yourself with your son just adds to the enjoyment.

Lee
 
Jul 22, 2010
386
16
18
SF Bay
#12
Inspiring work. I'm about to take my temporary room and make it full time with some treatment. Just working on layout plans right now. Exciting to have such positive results from your hard work.
 

es347

VIP/Donor & WBF Founding Member
Apr 20, 2010
1,570
1
38
Midwest fly over state..
#14
Mike,
The null is not the ceiling. It's too close to the seated position and speakers to null at that frequency. Also, boundary nulls (SBIR or Allison effect; all same thing but different names) are always characterized by a sharp phase reversal at null center frequency and narrow Q null. That doesn't sound like what you are describing. It is possible that woofer integration may not be smooth and that could cause a wider Q null more consistent with what you are describing.

But there's no way to really know unless you measure it. You can measure the reflection using the ETC function in REW. You can also look at SPL and phase. If there's no reflection in ETC which matches up with a boundary in your room, then the only other possibility is a woofer integration problem. IME, speaker designers aren't best at diagnosing room issues or even bass integration issues. I mean that for all speaker manufacturers.

It would be much faster and much more certain to measure using REW.
..or just pour a single malt and sit in the sweet spot :p
 
#15
Excellent Mike, congrats. And to your son as well on the STP single day effort. I did that one-day ride multiple times many years back, now not fond of rides with too many people of varrying skill levels. One knucklehead can spoil the day for a lot of riders. I haven't done RAMROD, but its on my list. The Hurricane Ridge climb is August 2, if your son isn't aware it would be a good climb to prep for RAMROD.

I'm amazed you've done as much as you have to your room post-construction. Sadly, it says many room designers have gaps/flaws in their knowledge. You went all out originally. Have you dared to re-measure the room, or content with subjective impressions?
 
May 30, 2010
15,313
596
113
Portugal
#16
Mike,

There are no real firm boundaries at 30 Hz in a room as complex as yours, as panels can flex at such low frequencies. Most probably covering the boxes changed the tuning of the wall bass traps somewhere in the front and/or back wall and fortunately improved your room. BTW, nulls due to destructive interference are not forcefully sharp, particularly in complex rooms (we must remember your room was built inside an old barn http://www.positive-feedback.com/Issue16/lavigneroom.htm) .

Congratulations and enjoy!
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
7,576
679
113
#18
Mike,

There are no real firm boundaries at 30 Hz in a room as complex as yours, as panels can flex at such low frequencies. Most probably covering the boxes changed the tuning of the wall bass traps somewhere in the front and/or back wall and fortunately improved your room. BTW, nulls due to destructive interference are not forcefully sharp, particularly in complex rooms (we must remember your room was built inside an old barn http://www.positive-feedback.com/Issue16/lavigneroom.htm) .

Congratulations and enjoy!
Micro,

there are two small remaining bass traps on each side in the rear; all the other bass traps have been removed (4 years ago) and covered with Quietrock 545 sheets and an additional 3/4" ply layer to establish solid room boundaries and to completely eliminate any flexing. the only other trap is the ceiling. it's built and braced very solidly.

I suppose determining whether the change is caused by closing off the openings to the ceiling, or caused by a change in wall flex is a question too complex to even try to worry about. I care about the result. but it's likely you understand it better than I ever will or even care to.
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
2
0
Dallas, Texas
#19
I read "suck out" in the OP to refer to an actual objective phenomenon. Thanks for clarifying that. It gets confusing for me when one uses subjective impressions to describe what is, in fact, an easily measureable objective phenomenon. Anyone could do it. There's no expertise needed.
I'm sure you know better than my speaker designer. and I'm not claiming any specific measured result. only that the audible result of closing the openings in the ceiling bass traps was the deep bass being quite boomey where it had not been so, and added energy to the music. then when I turned the bass tower adjustments to what the speaker designer said was the 'flat' position, the overall performance of the system increased dramatically.

where the openings to that humongous 21' x 29' x 15" bass trap were evidently was not an issue. it was the volume of that trap and it's effect of allowing the suck out. (my SWAG).

according to my room designer the suck out was measurable everywhere in the room; not just at the listening position.
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
7,576
679
113
#20
Excellent Mike, congrats. And to your son as well on the STP single day effort. I did that one-day ride multiple times many years back, now not fond of rides with too many people of varrying skill levels. One knucklehead can spoil the day for a lot of riders. I haven't done RAMROD, but its on my list. The Hurricane Ridge climb is August 2, if your son isn't aware it would be a good climb to prep for RAMROD.

I'm amazed you've done as much as you have to your room post-construction. Sadly, it says many room designers have gaps/flaws in their knowledge. You went all out originally. Have you dared to re-measure the room, or content with subjective impressions?
Bob, thanks.

likely I will re measure the room sometime soon. I would be happy as it is. but with all the adjustability of the speakers it would be silly not to take full advantage and wring out as much goodness as possible. the question is whether I need to pay to fly my speaker designer back up to my home (or whether he would come at all). possibly with some measuring we can accomplish enough without him.

my son is doing the Cascade 100 mountain bike endurance race Saturday morning in Bend, and then the RAMROD next Thursday.

if he can do all three of these rides in two weeks i'll tip my hat to him.
 

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