[Housteau]

The best way to find where a trap should go is to play a sine wave at that frequency (45 Hz) while you walk around with an SPL meter. Wherever the level is highest is a good location for a trap.

At 45Hz I found the high concentration in my front right and back left room corners, and even higher on that wall between my speakers at the first reflection point.  The intensity then rises to its max. as I go up that front wall to the cathedral peak and along it back towards the back wall.  The intensity drops quickly about 5 feet from my top front cathedral peak.

I have another dip of a lesser amount that has peak concentrations on the opposite cathedral corner against the back wall.  So, it appears that my original suspicions about my cathedral ceiling were correct.  I will look into designing something substantial for thoes upper corners and my front wall first reflection point.  To trap a frequency that low and to do any good I am assuming it will need to be.  This should be interesting.

[Housteau]

What sort of thickness is required to absorb at 45Hz?

[bpape]

You're probably looking at 8" or so at a minimum.  A bit of a gap behind it would also extend it a little deeper.

Bryan

[McTwins]

What sort of thickness is required to absorb at 45Hz?

Hi
Forget about the thickness, install a Helmholtz resonator. It's the only way.
By the way, nice system you have.

[Housteau]

Forget about the thickness, install a Helmholtz resonator. It's the only way.
By the way, nice system you have.

Thank you.  That was a thought, but fortunately the areas where I measured the build-up to be are places I already have treatment.  So, I will just need to boost those places and be creative on how I will do this.  I have already ordered materials for my plans.  It will be different.  One main reason I want to stick with broadband is that I want other areas of the bass to benefit from this change as well.

[Housteau]

Enough materials have come in for me to get started on my project.  I have been able to complete just over 1/3 of my front wall.  But, before I did that I needed to get a few basics straightened out.

First off I checked the positions of both my low bass towers and my main speakers to achieve the best and smoothest bass response possible, low bass for the towers and mid bass for the upper range sections.  I was not worried about enhancing peaks at this point as I knew I could take care of them later.  My concern was more focused on minimizing the dips in response.  Along with changes in speaker positions came a change in my listening position as well.  My seat was moved back about 6 inches closer to the rear wall, the bass towers were moved 10 inches closer to the front wall, and the mains were brought into the room about 6 inches.

Next came the toe in adjustment done with help from a Chesky test CD for soundstage.  This was a critical step because I didn't want to loose the presentation I had before moving those speakers, and that is always a possibility.  Often to gain one thing you need to sacrifice something else.  Fortunately that was not the case here at all and I actually ended up gaining quite a bit more than I had previously.

The third step delt with the electronics and came in two parts.  First was to check and modify my crossover points and phase adjustments due to the new speaker locations and their interaction with the peaks and nulls.  I did up my crossover point of the low bass to 66 Hz and changed the slope to 18db.  The second part of this was to use the power of that modified digital crossover to notch out any peaks created by either the room or my crossover points.

With the room and equipment set up as good as I could get it, it was time to start modifying my room treatments.  But, before I did that I took benchmark readings charting my room one hertz at a time up to 125 Hz or so.



This image shows the lower foundation of my wall treatment.  It is well anchored to the wall.



Here is about 1/3 of the treatment in place.  It consists of two layers.  The first is 6 inches of 2' x 4' 703.  On top of that creating a semi-wedge is 6 inches of 17" x 4' 703 and wrapped in a batting.  I didn't see any reason to remove it from the box and just cut the box to the shape needed.  The top was left off so it could function as a reflection point absorber as well.



This is the lower decorative cover.  It is an oriental three panel room divider screen found at Target for under $100.



To finish the front wall treatment the 703 will continue solid up that wall to the peak and be surrounded by another screen.  I hope to get to that in another two weeks once I get back into town.



This last picture shows the new positions of the speakers.  Those small changes made a difference.  With only 1/3 of that wall treated I did take a few measurements to see if any progress was made.  The largest bass concentration is up higher on that wall and at the peak, but even so this center wall first reflection point work did start to fill in the dip at 45 Hz.  It is just a start by measurement standards, but my ears tell me that I have already made substantial gains.

[doug s.]

another thing you might wanna try is a second pair of subwoofers.  you could try placing them in the rear of the room, out of phase w/the front pair, for starters.  smoother bass is usually easier to obtain w/more subs at different locations - smooths out room nodes regardless of room treatment...

doug s.

[Housteau]

another thing you might wanna try is a second pair of subwoofers.  you could try placing them in the rear of the room, out of phase w/the front pair, for starters.  smoother bass is usually easier to obtain w/more subs at different locations - smooths out room nodes regardless of room treatment....

Yes.  I know someone that believes strongly in this type of set-up and loves his.  But, my system is far too complicated as it sits right now being tri-amped.  I don't have any peaks to deal with and just a few dips.  One has already been reduced by half just with positional changes.  The other at 45 Hz is already narrower and not as deep.  I could easily live with be happy with what I have now.  I just felt it wouldn't hurt to try take care of the few remaining issues as simply as possible.

The more bass energy that goes into the room at 45 Hz the deeper that dip tends to go.  I have tried to fill it in, but did not get good results until I started to strategically absorb that frequency.

[doug s.]

another thing you might wanna try is a second pair of subwoofers.  you could try placing them in the rear of the room, out of phase w/the front pair, for starters.  smoother bass is usually easier to obtain w/more subs at different locations - smooths out room nodes regardless of room treatment....

Yes.  I know someone that believes strongly in this type of set-up and loves his.  But, my system is far too complicated as it sits right now being tri-amped.  I don't have any peaks to deal with and just a few dips.  One has already been reduced by half just with positional changes.  The other at 45 Hz is already narrower and not as deep.  I could easily live with be happy with what I have now.  I just felt it wouldn't hurt to try take care of the few remaining issues as simply as possible.

The more bass energy that goes into the room at 45 Hz the deeper that dip tends to go.  I have tried to fill it in, but did not get good results until I started to strategically absorb that frequency.

hi housteau,

i am glad you are getting better results by repositioning.  re: present complexity of your present set-up, you could simply connect another pair of subs to the same amps driving your two subs.  if the amps can handle the lower impedance caused by the additional subs, they will actually make more power.   i suspect that adding two subs in the rear of the room will not increase the nulls that you now get by adding more bass energy into the room - the actual bass energy should be the same, (you could reduce the gain of the bass amp to keep the total bass output the same), and having the bass energy coming from four different locations instead of two, should smooth out room response even more than re-positioning the two subs you already have.  if you still have your low-boy sub, (subs?), or if you could borrow a pair to experiment, the results you are wanting may actually be easier to achieve than by adding more room treatment.  just a thought...

doug s.

[Housteau]

  i suspect that adding two subs in the rear of the room will not increase the nulls that you now get by adding more bass energy into the room - the actual bass energy should be the same, (you could reduce the gain of the bass amp to keep the total bass output the same), and having the bass energy coming from four different locations instead of two, should smooth out room response even more than re-positioning the two subs you already have.  if you still have your low-boy sub, (subs?), or if you could borrow a pair to experiment, the results you are wanting may actually be easier to achieve than by adding more room treatment.  just a thought...

And it is a good thought too.  The low-boy sub (a VSS) was just a loaner until the actual towers came in.  A benefit of them is their multiple arrays.  This puts bass into the room at different elevations to achieve in that vertical space what multiple subs, as you suggest, could do in a horizontal one.  When I was working and testing with one channel at a time I was able to use both towers on a single channel to check simultaneous multiple horizontal locations.  Phase issues were much more tricky especially at the crossover overlaps to the  mid-bass sections of the main speakers. 

My room doesn't have any peaks and just a few dips.  I am really a subjective guy when it comes to making audio decisions.  I do value measurements for room acoustics, but they are just a start.  They help to show where problem areas that may effect the sound could be.  This aids in planning corrective measures.  However, just because a graph shows a relatively flat response, that does not mean that the sound will be ok.  There are many important quality factors in there that are not being measured.  Besides, a microphone is not the human ear and solid test tones are not music.  Different speakers and subs that may measure to be very similar in a particular room with test tones can sound night and day from each other when it comes to playing back music. 

[Browntrout]

Thanks for taking the time to post pictures of what you are doing, it gives me some courage to continue with DIY treatments. Thanks.
 Your setup must sound lovely. What music do you play most?

[Housteau]

Thank you.  I look at it like this.  Over the years the members here at The Circle have helped me so much that when I get the chance I like to try and give something back that might be of value to someone else.

I am pretty much across the board when it comes to music.

[fido]

Thank you.  I look at it like this.  Over the years the members here at The Circle have helped me so much that when I get the chance I like to try and give something back that might be of value to someone else.

I am pretty much across the board when it comes to music.

Housteau, your setup is just, well, spectacular looking (and no doubt sounding)! Thanks for the pics & your input to this thread - I wanna visit & stay in your listening room for a week or so! 

[doug s.]

yes, your system & room really look incredible.  i am sure all this talk about getting rid of bass dips is really nit-picking, in the grand scheme of things!   

doug s.

[Housteau]

Thank you, and all are certainly welcome to visit.  It is very rare that I am able to have someone stop by that actually understands my madness.  The nit-picking is just one of the many tragic symptoms for the disease.

[doug s.]

...The nit-picking is just one of the many tragic symptoms for the disease.

really?!?  who on this site woulda ever thunk it?    

doug s.

[woodsyi]

Actually nit-picking is a pain in the arse and I don't think audiophiles know anything about it.    You have to get a very fine comb and scrape the scalp to pick out any nits and comb them out.  None of the chemicals we tried worked so we went with the ancient wisdom of olive oil.  If you oil your hair at night for three weeks and you nit-pick every night, whatever nits you miss that hatch will be suffocated and you will be free of lice. 

Nit-picking is a very necessary activity when you have to do it. 

Rant over.

P.S.  You system looks very nice.   

[Housteau]

Well, I made it back home finally and was able to complete my front wall retreatment.  The entire project went together without any problems and was easy and fairly inexpensive to do.  I was only out a few hours of work, the cost of two boxes of 703 and two oriental room divider screens found at Target Online for $99 each including shipping.

Behind those screens is 12 inches of 703 running their entire length.  The width is 24 inches in the back for 6 inches of the depth, then the top six inches is 17 inches wide.

I am pleased with the new measured performance, but that really doesn't do justice to the change in what I hear.  The numbers may be small, but the overall change in character of my room is much larger that that.  The nice benefit of using broadband treatment is that while you may be targeting  specific frequency issues, many of the others you didn't even realize your were having issues with get helped as well.  I believe this is why I am hearing such a large improvement when my target dip frequency of 45 Hz was only filled in by 3 db. 

I was able to measure one of those side benefits up above 100 Hz.  Between 100 and 125 Hz I had a bit of a saw-toothed pattern, up a few db, down a few db, every few hertz throughout that range.  Well, that is not there anymore.  More than likely I will be able to see this pattern repeated as I continue to chart my new room curve higher in frequency.  I never considered the small bumps and dips of plus, or minus 2-3 db as being problem areas, but I guess I was wrong.

[terry j]

can I compliment you on the looks of the trap?

I can? great.

They look fantastic. well done. (the system doesn't look too shabby either btw)

[oneinthepipe]

Yes, that looks really great.  Very creative way to place/conceal/decorate a very large trap.