My DIY Traps

[Glenn Kuras]

where did you place the traps? Is there any standard rules to follow?

Thanks,
B.

Here is a layout that might help you get some ideas where to place treatment.

Glenn

 

[Davemcc]

Nice job on the traps, Andrew. I built my own variation on the theme. I used decent wood for the frames, added masonite backs to each frame and painted the frames black. Then I made up smaller frames out of 1x1's that fit inside the larger frames and streched the cloth over these small frames. I inserted the mineral wool and put the cloth frame inside the larger frame, so the cloth is framed like a picture.

I've made arrangements with my next door neighbor with a table saw to rebuild my corner traps. I knew my room was bad, but that SMS-1 drew me a picture of exactly how bad it is.

 

[Alex2507]

Nice job on the traps, Andrew. I built my own variation on the theme. I used decent wood for the frames, added masonite backs to each frame and painted the frames black. Then I made up smaller frames out of 1x1's that fit inside the larger frames and streched the cloth over these small frames. I inserted the mineral wool and put the cloth frame inside the larger frame, so the cloth is framed like a picture.

I've made arrangements with my next door neighbor with a table saw to rebuild my corner traps. I knew my room was bad, but that SMS-1 drew me a picture of exactly how bad it is.

Any chance of some pics?

 

[islanders_rx7]

Cant see any pics

 

[Davemcc]

Cant see any pics

Oooooooh, I can explain. Well, not really. I'm just old, tired and lazy, a real 21st century Oblomov.

I will take pictures right now.

 

[Davemcc]

For starters, here is my bass response after the SMS-1 had done it's auto eq function without the traps. You should notice a slight problem with this graph.

Here is a pic of my front soundstage with the traps installed. I don't have a screen shot of the SMS-1 after, but it is reasonably flat. There does seem to be wide variation in response depending on where in the room the mic is placed, though. That's the PB12-Plus in the left corner and the STF-3 in the right. The graph is better with both subs in the room, and at least there aren't any major nulls.

Here's a closer shot of the right side trap and wall panel. This trap has kind of an uneven edge to it, but I'm OK with that. It doesn't look that bad in person, really. I'm not going around and re-stapling it. Did I mention I'm lazy.

Sorry for the bad shots. I'm no kind of photographer.

 

[gullfo]

nice, clean design and workmanship! congrats!

 

[Davemcc]

After seeing my corner traps in photos, I think I'm going to build a thin black frame around their edges to straighten up the sides a bit. It will probably look a lot better.

 

[treejohnny]

Dave,
Are your corner traps triangle shaped? Are they 2" or 4" thick? How do you hold them in place?

This looks fairly easy to do. I just need to get to it. Has anyone done something to dress it up some, like embroidery?

 

[FguerraG]

It would be nice to see a before and after graph of your EQ

nice job on the panels BTW!

 

[Davemcc]

Dave,
Are your corner traps triangle shaped? Are they 2" or 4" thick? How do you hold them in place?

This looks fairly easy to do. I just need to get to it. Has anyone done something to dress it up some, like embroidery?

I cut all my insulation into 17"x17"x24" triangles. Then I cut two masonite panels 17"x7' high and built them into a corner shaped frame, open on the 24" side. Then I just stacked all the triangles of insulation into the frames to full height. I covered the front with a sheet of cotton batting then speaker cloth. That's it.

They are self-supporting and just stand in the corners by themselves. The reason the edges of mine look rough is because the masonite is not very stiff and tends to bend when you stretch the speaker cloth across the front. If I were to do it again, I would use stronger material for the sides construction. Most of my frame was just built from scrap wood lying around.

FguerraG,
My last subwoofer calibration produced a nearly table flat response to below 20hz. I'll try to get the mic set up again tomorrow and take a pic.

 

[peerlesser]

I've made arrangements with my next door neighbor with a table saw to rebuild my corner traps. I knew my room was bad, but that SMS-1 drew me a picture of exactly how bad it is.

The response shown in SMS-1 is known to be too optimistic. If you measure with Room EQ Wizard or other accurate computer based measurement software, the response will look even worse.

The only thing that worked for me after extensive bass trapping was still this.

http://www.dspeaker.com/en/support/anti-mode-technology/measurements.shtml

It costs 200e and does everything automatically. Much flatter result than that expensive SMS-1. Also the decay times on modes got a lot shorter. Hence the name "Anti-Mode".

 

[Davemcc]

The response shown in SMS-1 is known to be too optimistic. If you measure with Room EQ Wizard or other accurate computer based measurement software, the response will look even worse.

I know what "worse" looks like. When the sub sat in the other corner, I graphed it manually using the Avia disc and spl meter. With an 80db baseline at 80hz, it spiked to 107db at 40hz.

I can't take the pics today guys, sorry. Maybe later tonight or tomorrow.

 

[Davemcc]

Here is my latest SMS-1 picture. Corner traps installed, SVS PB12-Plus in 16hz tune (1 port plugged), peq on sub not used, SMS-1 reset to factory defaults then ran auto-program with manual touch-up afterwards, mic at main listening position.

I hope you see it is much better than before. It sounds a lot better.

 

[peerlesser]

Here is my latest SMS-1 picture. Corner traps installed, SVS PB12-Plus in 16hz tune (1 port plugged), peq on sub not used, SMS-1 reset to factory defaults then ran auto-program with manual touch-up afterwards, mic at main listening position.

I hope you see it is much better than before. It sounds a lot better.

Looks good!

With SMS-1, it is usually takes hand tweaking to obtain best results. You would get even better response if you can use REW or similar. SMS-1 showed quite similar response at my friends house, but there were still quite high narrow peaks when we measured with portable mac and REW with ECM8000. It turned out that the 1Hz resolution in SMS-1 was just not enough for center frequency resolution, so he decided to buy either DCX2496 or automatic 8033AM. I recommended 8033AM since it has 24 filters and included microphone. Only problem with 8033AM is that it does not have tunable lowpass, but my friend uses A/V receivers 80Hz cross-over for the sub anyway. Now that 8033AM is out, that SMS-1 feels kind of pricey.

 

[Davemcc]

Thanks. I can see myself ending up with a different eq process down the road. I haven't been back into the hobby that long and everything I do has a steep learning curve. The best part of the SMS-1 is that it is a simple, pre-packaged solution that gives good results to a novice like me. As I learn more and demand more from my system, I'm sure I'll revisit this issue down the road.

 

[peerlesser]

This was posted in Finnish site, it is probably one of the worst rooms I've seen:

It has a peak of about 20dB at ~47Hz.

This is the version that was corrected by automatic calibration of 8033AM (due to the author)

I guess sometimes you need even more than 12dB attenuation. But bigger problem in SMS-1 is that it's own response graph is heavily smoothed, so that 20dB peak could look like a 10dB peak or so. Best results with it still requires REW with computer setup.

 

[mike c]

peerlesser, why don't you re-measure at a higher volume? say 80db at least. if i'm not mistaken, there are some peaks and valleys that appear and disappear at different SPL levels.

 

[peerlesser]

peerlesser, why don't you re-measure at a higher volume? say 80db at least. if i'm not mistaken, there are some peaks and valleys that appear and disappear at different SPL levels.

I can't since it's not my measurement, but the author wrote that those dB:s are low because of some issue with sound card settings. He had checked that the SNR and volume in measurement was good. Room response looks always the same if the volume is high enough from noise floor, as it measures linear function. If there is deviation in the response with different volumes, there is non-linearity in the system (distortion from subwoofer or resonating window making sounds on its own etc.).

My point is that what small experience I have with SMS-1, I think that it would not be able to do the same even it costs 3 times more than 8033AM.

There are more results in the thread I picked those measurements, but I don't dare to post them. For these particular measurements I asked permission from the author.
The original thread: (in Finnish but the pictures still work OK)
http://www.dvdplaza.fi/forums/showthread.php?t=65581

 

[peerlesser]

Well heres is my one of my own REW measurement with about 70dB volume before and after autocal of 8033AM.

Just for comparison, the same responses with 1/3 octave (over-optimistic) smoothing that SMS-1 uses in it's TV-ouput plots.

It's not possible to make even the manual corrections with that amount of smoothing, so the REW is imperative with SMS-1, thats why i swap it to 8033AM (and the cheaper price).