My GIK Pillar Trap Review

**hjones4841** · **02-18-09, 05:49 AM**

That is what I thought by just eyeballing the two waterfalls. Bet that is enough difference to be audible.

**thewire** · **02-18-09, 11:51 AM**

Yes they help quite alot. I was very impressed with listening to the entire Transformers movie while watching speakers move.

I ordered a case of 6 2" OC 705 and am buying a Rane SSE-35 Home Theater Equalizer. I was not pleased with sound from the front wall with my compressed insulation, and the back of the rooms upper corners sounded like the bass was lacking somewhat, so I want to put the rest of my insulation back there again. I hope that my screen will act similar to having a layer of FSK. I may end up leaving the back of my room without absorption and get some dipole surrounds. The back row is not real concerned about having more treatments, and they are already happy with the improvements thus far and think it is fine how it is. I will listen carefully for slap echos off the back wall again, but I didn't hear it last I checked, and it may have had something to do with how I have changed the riser more recently.

**hjones4841** · **02-18-09, 01:07 PM**

My other two Monsters shipped today, so I should have them tomorrow afternoon (just one night to here from Atlanta). I will make a few measurements this weekend and post them. As stated earlier, I am limited as to where they will fit. Try putting a R30 batt behind the Monsters - Bryan said that might help in the lower freqs.

Not sure what you mean about the screen acting as FSK. Is it vinyl on a frame? If so, it should be reflective to mids/highs and not do much below that.

**thewire** · **02-18-09, 04:13 PM**

Quote:

hjones4841 wrote:

My other two Monsters shipped today, so I should have them tomorrow afternoon (just one night to here from Atlanta). I will make a few measurements this weekend and post them. As stated earlier, I am limited as to where they will fit. Try putting a R30 batt behind the Monsters - Bryan said that might help in the lower freqs.

Not sure what you mean about the screen acting as FSK. Is it vinyl on a frame? If so, it should be reflective to mids/highs and not do much below that.

Good idea. I have more than enough for that area on my stage, and I don't like it compressed, so I will put that behind the Monsters. I actually forgot to try that I was so busy.

The screen is a High Power Da-Lite screen that has a vinyl back on it. I think that I remember reading that FSK was not needed with a screen in front of it, but I don't recall the difference between a vinyl screen and FSK. I'm just hoping it reflects enough back above ear level.

I have been busy today trying to get things setup. It seems easier to hear higher q resonances after adding the Monsters. I'm trying a couple layers of wood (over 3") added to the face of my Helmholtz Resonators and stacking the concrete tiles on the top of it. It sounds like it is helping in the back of the room at least. I'm also going to try various things above the first reflection points to see if I can improve anything with that, and make them more decorative. That's something I have not tried yet so I will give it a try. I hope to have things setup with what I have by the end of the night.

Do you have planned where you are putting the next Monster traps when those arrive?

**hjones4841** · **02-18-09, 06:27 PM**

I will probably start with them in the center rear wall, in front of a brick fireplace on the GIK stands. That is where Bryan initially recommended them for absorption from that wall to the center recliner. They worked well there, but are the ones I mounted horizontally in the rear corners. I can slide them around easily to find the 1/8th wavelength for the 27Hz peak that I have. Don't know what the point of diminishing returns is for my room; I will have 5 Monsters along that 12.5ft wall, counting the ceiling corners and the ceiling center, plus the two up front in the corners.

(Hey, GIK, how's about a quantity discount for thewire and me

)

I sent Glenn an e-mail about a simple mod to the GIK stands. Due to moving the first traps around, the wood blocks that fasten the stands to the traps were coming loose. They are held in place with two short nails. I drilled a small pilot hole between the brads and put in a 1" drywall screw. Sure tightened them up. I had thought about using wood glue, but was out of it. Glenn replied that they will look at using that mod.

**hjones4841** · **02-18-09, 07:04 PM**

thewire: I meant to ask you what brand/color of black paint worked best for you? Folks at AVSforums like Behr Mouse Ears, but say that it badly shows marks. I used a Glidden flat with a Behr color that Home Depot mixed for me. Color is fine, but has a slight sheen where light from the screen hits it.

Before I blacked out the whole ceiling, I covered two rows of tiles closest to the screen with Parts Express black grill cloth - looked great with no reflection or sheen, but too expensive to do the whole room.

**thewire** · **02-18-09, 07:39 PM**

Quote:

hjones4841 wrote:

I will probably start with them in the center rear wall, in front of a brick fireplace on the GIK stands. That is where Bryan initially recommended them for absorption from that wall to the center recliner. They worked well there, but are the ones I mounted horizontally in the rear corners. I can slide them around easily to find the 1/8th wavelength for the 27Hz peak that I have. Don't know what the point of diminishing returns is for my room; I will have 5 Monsters along that 12.5ft wall, counting the ceiling corners and the ceiling center, plus the two up front in the corners.

(Hey, GIK, how's about a quantity discount for thewire and me

)

I sent Glenn an e-mail about a simple mod to the GIK stands. Due to moving the first traps around, the wood blocks that fasten the stands to the traps were coming loose. They are held in place with two short nails. I drilled a small pilot hole between the brads and put in a 1" drywall screw. Sure tightened them up. I had thought about using wood glue, but was out of it. Glenn replied that they will look at using that mod.

There is such thing as to much and there is also to little. The tonal balance and decay is important but there is a an amount that you will have to decide what sounds right. There are recommendations for how many sabins to absorb and also how it placed in the room. Many acousticians have a set of guidelines for how much to use and in what ways. You will want to find what works. It really takes more than one person to complete a room. It is a collabrative effort and I think that Bryan or others will tell you if you have overdone something and I read him telling someone when something is too much.

Some goals of home theater are:

Clear dialog
Precise sound localization
Spacious surround
Smooth sound movement
Even tonal balance
Full dynamics
Transparency
Every seat a good seat

**hjones4841** · **02-19-09, 05:06 AM**

Interesting point that you made about dialog. I would have never believed that bass traps could increase clarity in the center channel, but that is what happened. I originally thought that I had overdone it in mid/high absorption but after listening for a while I think it is just fine.

Dynamics in my system have never been a problem. The speakers are extremely efficient (104db/1watt/1meter) so getting very loud is easy, although at times I wish I had a second sub. I played an old CD of organ music Sunday at high volume and could tell the Velodyne was limiting itself. 99% of the other times it is enough, tho.

The Monsters may have been delayed by Fedex - multiple severe weather events last night between here and Atlanta, including tornadoes. News said that I-20 was shut down both directions about 60 miles east of here; never heard why.

**thewire** · **02-19-09, 05:14 AM**

Quote:

hjones4841 wrote:

thewire: I meant to ask you what brand/color of black paint worked best for you? Folks at AVSforums like Behr Mouse Ears, but say that it badly shows marks. I used a Glidden flat with a Behr color that Home Depot mixed for me. Color is fine, but has a slight sheen where light from the screen hits it.

Before I blacked out the whole ceiling, I covered two rows of tiles closest to the screen with Parts Express black grill cloth - looked great with no reflection or sheen, but too expensive to do the whole room.

I switched to Disney "Lamp Black" because the Home Depot in our area said they did not carry it anymore. I had my previous can for them to match which had been the Behr Mouse Ears. I have to keep the paint on hand to touch up the walls if they get dirty or scratched. I went to a paint store and they said they didn't carry black so I looked at Wal-Mart and Lowes, then Home Depot where I found the Disney Mouse ears. I thought it was best so I went with that. I was not bias because I had not researched it. I figured nobody used black but I had forgotten about ceilings and screen walls then. I had not visited the forums for a few years when we had the HT first built. I had a few weeks to get it done with the framing, electrical, walls, HVAC, and so on with help from the construction crew.

I used a grey primer because the walls sucked up the black very quickly and because they were textured it made it more difficult. I used a black light to find places that I missed. I had to apply three coats of the Mouse Ears after the primer. The extra coat was after someone decided to sweep the room.

It's not reflective much, and not enough to cause a distraction in my room. It sucks up alot of light so I had to get some track lighting in the back of the room. That worked out really well because I can aim it down and watch a movie without the room getting fully lit up, ruining the image, or having to bring a lamp into the room to take photos. The photos really make the room 10X more a mess than it is. I seldom take as much time to clean between projects as I used to.

I removed the face of my Helmholtz Resonators for which I will cover in a fabric frame. I reinforced the left and right walls with very heavy wood on the left wall and some 1 3/4" plywood on the right wall behind the panels. I moved the insulation off my stage to the rear corners inside the now...traps. They are about 1/4 full of insulation each. The insulation behind the Monster Traps helps also for the very low ringing, but the mains response is now very sensitive to the back of the room after reinforcing the walls behind the panels and there isn't enough insulation to fix the dip at around 168 Hz. It's not as bad as it was to start with. The response went up 5dB. I added 3 or filters but I forget. I will get back to that later, but the 40Hz dip is better which I am proud to have accomplished today. This is the one that REW recommended.

I could not buy the Rane eq. During the last 3 hours people started bidding and the price doubled so I woln't be getting that soon. The person selling has been selling many of them lately so I will keep an eye open. I will probobly get something else besides an eq. It would be nice to eq the center channel.

**bpape** · **02-19-09, 06:52 AM**

A comment on the dialog...

That actually is one of the most commone 'symptoms' of a room that has too little bottom end control. It's a lack of clarity in the center. It's also that 'can't hear the dialog so we turn it up - but then the effects are too loud so we turn it down' syndrome.

What's happening is that the bass decay time is out of control and the ringing is masking the dialog. People don't realize that male voice can easily go below 200Hz.

Bryan

**thewire** · **02-19-09, 07:52 AM**

Good analysis. I have tried a matching center channel and I had similar results. I hope treating the front wall helps.

I just noticed that my speaker ports on the bottom were both plugged with foam. That should raise the bottom frequencies some. For some reason my surrounds drivers and mains drivers do not look alike. In bringing the speakers into the room my mains did not match, and I had brought the surround up front thinking by other speaker was a main. I had checked the ports, but I did not check close enough obviously. That could explain the 250Hz ringing in the graphs. With DVE at high levels my speakers did not pass the buzz test at 250Hz. My previous review of the GIK traps still stands as I had that problem prior to plugging the ports, but I will give my impressions of with and without them again.

**hjones4841** · **02-19-09, 12:45 PM**

Fedex delivered the other two Monsters at 9 this morning - not bad since they only left Atlanta around 3 this morning. I will at least put them in the room tonight. Kinda limited on "play" time after work. Wife expects the system to be ready for the evening TV viewing by 7 p.m.

**hjones4841** · **02-19-09, 07:10 PM**

Quote:

bpape wrote:

A comment on the dialog...

That actually is one of the most commone 'symptoms' of a room that has too little bottom end control. It's a lack of clarity in the center. It's also that 'can't hear the dialog so we turn it up - but then the effects are too loud so we turn it down' syndrome.

What's happening is that the bass decay time is out of control and the ringing is masking the dialog. People don't realize that male voice can easily go below 200Hz.

Bryan

This may explain something that happened 10 years ago. I had a Klipsch Academy for center channel that I sold (sure wish I had kept it!) and replaced it with a Belle Klipsch (gussied up La Scala). I expected greater dialog clarity with the Belle but actually the Academy was better. The Academy had been on a stand about 18" or so off the floor.

The Belle is floor standing, putting the bass horn very near the floor. I bet that excites more room modes than the Academy did and could be the reason I am getting better dialog clarity now that I have traps in the room. Interesting.

**thewire** · **02-20-09, 09:30 AM**

I took some new measurements this morning after after taking the foam out of the left and right speakers. I found some in the back left surround also. That fixed the dip around 168Hz for the left and right speakers.

Here is a decay of every channel.

I used a 80dB target by turning down the level in the pre/pro after I calibrated levels with my THX optimizer. The level of the pre/pro after that was -3 for the subs and -3 to -2 for the other channels.

Left channel

Right Channel

Center channel

Right surround

Left surround

**hjones4841** · **02-20-09, 05:31 PM**

What was the purpose of the foam? Were you using it to change port tuning?

**thewire** · **02-20-09, 07:13 PM**

Quote:

hjones4841 wrote:

What was the purpose of the foam? Were you using it to change port tuning?

My surrounds used to be on some steel stands and I could hear more lower bass from the surrounds since the ports were at ear level.

**thewire** · **02-20-09, 07:40 PM**

Here are photos of the new bass traps in the back of the room. I want to add some cherry stained trim. I finished the fabric already but I need to trim off some of the extra.
The holes behind the couches (there are a total of 4 on each) near the subwoofer raised the 40Hz dip and adding insulation to the corners improved the ringing.

Here is how the traps look right now in the front of the room. I need to put some of my leftover carpet, fabric, reflective material, larger carpet and recarpet the whole areas, or something to hide the holes where my other 2" panels were hung. There is some insulation or something on the wall near one of the holes that have a couple of the screw anchors you can see above the traps.

**keelay** · **02-21-09, 11:30 AM**

My jaw drops.

Nice work. Thanks for sharing

**hjones4841** · **02-21-09, 02:20 PM**

thewire: Please help me understand how to interpret the spectral decay plots. Here is mine with center & sub driven. What am I looking at/looking for? Thanks.

**thewire** · **02-21-09, 03:04 PM**

Quote:

keelay wrote:

My jaw drops.

Nice work. Thanks for sharing

Thanks. Action scenes in the HT are starting to be pretty realistic.

Quote:

hjones4841 wrote:

thewire: Please help me understand how to interpret the spectral decay plots. Here is mine with center & sub driven. What am I looking at/looking for? Thanks.

I use spectral decay to look for an even amount of absorption and to compare that with reflections trying to balance the tone. The blue ones at the bottom go up when I treat I null, and they also go can go down when I treat a peak. I study the spectral decay and look for modes nearby when I am treating a null or peak to see how the effectiveness directly related to the nearby modes. When they seperate and the different colors are spaced futher apart then there is less coloration to the sound and it sounds smoother. If there are valleys or peaks that are not falling directly bellow previous ones above that the bass does not feel right as it decays away.

**thewire** · **02-21-09, 03:28 PM**

Here is an example of decay that does not sound smooth, and that does not feel right.

**thewire** · **02-21-09, 07:00 PM**

I picked up four things of R30 unfaced, paneling nails, and trim for the rear traps from Lowes. The trim has a smooth curve to it. The insulation should allow me to get the concrete off the rear traps, and remove the plywood in the ceiling in the back of the room above the center/rear wall, then fill the corner there. I need some around the tri-corners in the back of the room also. I hope that this will improve the surrounds some. If the rear corners are anything like the front corners, it should trap some around 90Hz.

**thewire** · **02-21-09, 11:12 PM**

Here are the new results after putting in the insulation. I had some extra to place above the right subwoofer where there was none.

These were the filters.

The intro to Star Wars EP3 at reference level sounded fantastic but the track lighting was shaking around like a leaf. I will do my best to secure that. We will be replacing the hole in the ceiling where I have taken down the hush box and the projector still is hanging with more Ceilume Ceiling Tiles/Back Panels, and insulation.

The surrounds seem to have improved but it looks like my single 2" 2X2 panel that I forgot was in the corner next to my right surround is helping more than treating above the ceiling helps.

Surround right

Surround left

Center

**robbo266317** · **02-21-09, 11:15 PM**

That is getting very smooth, you must be impressed with the results.

**thewire** · **02-22-09, 01:04 AM**

Quote:

robbo266317 wrote:

That is getting very smooth, you must be impressed with the results.

I think that I must spend at least a few hours in the HT listening to music and it sounds even better than before. The room sounds less bright than it did now since I have completed putting up the fabric on the rear traps.

In an odd note I found my settings in the pre/pro to be different than I setup last time, or at least wat I thought I set them to.

The subwoofer level was -5 and the mains were not adjusted like I had them. This has happened before that I can remember. I will need to check a manual and see if I can figure out the memory button. It could be I made so many adjustments I forgot.

Right now I would give the sound in the room

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