Monster traps #6&7 went into the room last night. I only had time to make one quick measurement. Seems that the mode around 27Hz is broader than before. I plan to run new waterfalls tomorrow with and without these two traps and will post them.
Subjectively, when the wife walked into the room last night, I was playing a Michael McDonald concert DVD. I remarked that the system sounded more natural than ever before. She agreed:unbelievable::bigsmile::yes:
Happy to report that Monster traps #6&7 make a measureable improvement. The green overlay is for 5 traps with the base color being all 7 with the latest two in front of the fireplace, center back wall about a foot in front of the wall. Out further seemed to not be as effective. BFD in ON, sub only, 80Hz crossover.
The only subsonic filter in the system is the one built in the Velodyne sub. It has two settings: 15Hz and 35Hz - it is in the 15Hz position. If you are wondering about the performance below 30Hz, this sub has always had strong output below 20. I have noticed an increase in measured and perceived output below 30 as I added traps.
As stated before, the system has never sounded as grand as it does now. Wish I had put the traps in long ago. Anyone who is on the fence about trapping - do it.
With all that absorption on the rear wall (5 traps) walking back there is psuedo-anechoic. But, I don't have any seats back there, so no problem. I wonder what this has done to the bass FR of the back K'horns - I may have too much absorption in the 100-200Hz range. Should not be that big of a problem for the back surrounds, tho.
I paid particular attention to dialog during last night's viewing. While it is extremely clean and pinpoint focused, it is quite different from what I had before. It almost sounds thin. I suppose I am hearing the lack of "chestiness" that was in the system before.
I was kinda puzzled about how the last two traps performed as I moved them away from the back wall. I expected to see more absorption in the lowest octave as I moved them out. I think I know what is happening. The traps are on stands, sitting on the fireplace hearth. The tops of the traps are pushed against the fireplace mantle, forming a small corner. This may be the reason they work better there.
This morning I am going to adjust the position of the center ceiling trap to bring it down to the top of the last two. This will provide an effective trap area of about 72" x 48."
I need to post a couple of pictures so you can see what this all looks like.
Here are photos of the back of the room (trap city!) and one of the front mains with a 42" custom Monster mounted vertically.
I measured FR of one of the back K'horns - steep, narrow dip at about 60Hz. Likely a room mode, although that is where the Monster trap effectiveness peaks per the lab test on GIK's website. Not really a problem with crossover set at 80Hz.
The K'horns have been in continuous production for 60 years, so that could have been what you heard. I was first introduced to them by a dealer in Starkville, MS in the late 1960s when I was in college. I spent many an afternoon at his house listening to mainly classical music (Copeland's Rodeo was a favorite). He would on occasion allow non-classical music (his wife liked Cat Stevens as I recall.) The first pair (the ones in the rear) were purchased from him in 1978. The front pair along with the Belle center were purchased from Hoopers in Birmingham in 1998.
As stated in another thread, I have decided to treat the suspended ceiling after all. Yesterday I picked up enough ceiling tiles for about half the room (all I could haul) and some heavy brown paper. Black burlap is on order from Joann's on-line store - supposed to be here Friday or Saturday.
The plan is as follows: "face" the ceiling tiles with the brown paper to prevent mid and high freq. absorption. Then, cover the paper with the black burlap. R30 goes on top of the tiles when put into the grid. As of now, I plan to do the whole ceiling (about 35 tiles) this way, but will start at the front of the room since the rear of the room has the most absorption now.
I put the paper on several of the ceiling tiles today. Lessons for others that decide to do this: first, it is nearly impossible to get all the bubbles out from under the paper; I hope that when I stretch the fabric across the tile the paper will be flatter. Second, the Duro spray adhesive does not work as well for this task as the mid level 3M. Third, the adhesive sticks better to the back side of the ceiling tiles. For me it did not matter which side the paper was on since they will be covered with cloth anyway. I have a large quantity of high strength pre-mixed wallpaper adhesive that I may try on the next batch instead of the spray stuff.
I will post graphs as I progress with this so we can compare what difference ceiling treatments make.
Your front speakers are from the year I graduated and the rear speakers you have had since the year I was born. That is quite a coiencedence. Look forward to seeing the new results while you are treating the ceiling.
Must be nice to be young! Our company hired a younger engineer a couple of years ago. He was 36 at the time. I told him that when I started work for this company, he was in diapers. Sad, really sad.
A funny happened about that same timeframe. I was in Best Buy and was walking up to the cashier with a $15 dollar component cable. A salesguy "accosted" me telling me of all the virtues of Monster Cables (at many times the price, of course.) I explained that I am a registered electrical engineer, certainly knew how cables are constructed and how they work, and had been working with audio gear since before he was born. He said "that just can't be." I said, funny, you don't look like you are 45:heehee:
One thing that I would do to find where to place insulation above the tiles was to measure what it was like in an area without a tile. That would help give me an idea how much I needed to put into the area. One thing I would recommend also is that when you place it up there besides a mask I would wear some protection around your ears so the stuff does not get in there because the wax will build up and you may need to clean them out some. It's just something to consider and I'm not sure that is neccessary or not but it might help.
The black burlap from Joann's came in today. The good news is that it did not cost much. The bad news is that it looks like it did not cost much. As I kinda suspected, the brown paper shows thru the burlap.
So, I seem to have two options for plan B: paint the brown paper (can't see how that work out well, what with the bubbles in it I already have) or go back to the black posterboard idea. I think the posterboard with the wallpaper glue will be the next thing I try. Local Target had plenty of the black posterboard earlier this week and it is cheap enough. That under the burlap should look OK.
thewire: I have worked enough with fiberglass insulation over the years to know the precautions. Not that I always take them:bigsmile:
Status update on the ceiling treatments. I took a day off today (crazy Alabama weather - 3 inches of snow Sunday, 70 degrees today:unbelievable and reworked the front 4 rows of ceiilng tiles - to about 8 feet back from the screen/sub wall. Technique used was black posterboard over the acoustic tiles, then the black burlap wrapped around the tiles.
I used 3M spray adhesive to attach the posterboard to the tiles and for securing the burlap to the posterboard. I wrapped the burlap around the edges of the tiles, then used spray adhesive and staples to secure the fabric to the backs of the tiles. Then R30 on top of the tiles after they were put into the grid.
I have not made measurements yet or done any critical listening, but I am well pleased with the appearance - much nicer looking than the painted sheetrock "tiles." The imperfections in the cheap burlap are not that noticeable, although I certainly would not use it for DIY traps or other work that would be more visable.
I tried painting the brown paper that I had put on one of the tiles last weekend - disaster, pucker city:unbelievable:
I doubt that I will do any more ceiling work until next weekend. More later with plots.