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In Reply to: RE: Question regarding J Risch tube trap construction posted by tominseattle on July 31, 2007 at 17:45:14
I have built ten, twenty inch diameter, Jon Risch Tube Traps. I used a 1 mil thick plastic wrap on half of the tube as Jon described. It only took a minute or two to add this, so it was no big deal. However, because I used burlap that was sewn in a tube shape, the plastic did make it easier to slide the burlap down the length of the tube over the poly batting.
My room is also 13'X15', with 10' tall corners in the rear and 8' tall corners in the front. This is the smallest listening room I have ever had and I was pretty disappointed in the way it sounded.
I first built two 4 footers and installed one each in the front corners. While there was some level of improvement (bass seemed a little tighter, slightly better imaging), it wasn't quite what I had hoped for given the effort I put into it. Obviously there is a learning curve to building these and the first two were far more difficult than subsequent units. I built the first two completely by myself, but solicited the assistance of my wife or son for the wrapping of the outer layer of fence on the remaining units. Then it got pretty easy to whip these things out.
Next I added two more 4 footers to the front corners to go all the way to the ceiling. This made a profound improvement to the sound. Bass tightened up a lot more and got deeper. The soundstage got wider and much deeper. Very loud passages became much more relaxed in that you didn't clench your teeth and squint when you knew a big crescendo was approaching. They were just as loud and dynamic, in fact more so, but it just seemed the room could handle it better without overloading. Images became more three dimensional with more space between the individual images.
The biggest improvement though was something I didn't really expect to be so dramatic and that was an increase in detail. New things were just popping out of every record I played. My slight disappointment in the performance of just the first two tubetraps was replaced with complete joy with the addition of the third and fourth unit. It seems you really do need at least four in the room to make a substantial impact.
I then added two 4' units to the rear corners and got another significant bump in performance. All of the improvements the third and fourth units brought were enhanced even more except for only a minor improvement to soundstage depth. Next I added two 3' units to the rear corners (7' total height). Again a pretty nice enhancement, but at this point I think I was starting to hit the realm of diminishing returns. Adding the final two 3 footers to reach the ceiling of the rear corners brought even less gains. Noticeable, but not nearly as significant as the others. That said, there is no way I would consider not having all four corners treated from floor to ceiling. My room truly has been transformed.
Through all of this, I have kept the reflective plastic sheet side pointed into the corners. The high frequencies just sound so smooth and natural right now that I haven't wanted to change a thing. However, I am now building the Risch wall panels and have gotten four of them into the room thus far (that point of diminishing returns just faded away). As I add more panels I will experiment with the reflective side of the tubes to see what affect that will have.
Have fun building the rest of your tubes and even more fun listening.
Follow Ups:
Brian,
You said that you built the 20" sizes. Was your inner circle 16"?
I wanted to build them that size but was worried by Risch's statement that they can get rather unwieldy and hard to build at sizes beyond 16" One nice thing about > 16" base is that they will stand up by themselves very nicely, wasnt so sure about anything smaller being so stable. I just used up a whole roll of fiberglass building these four, I think, based on your reports I am going to build at least two 20" soon.
As far as the plastic on half, i have applied it over the outer fencing and then put the high loft polyester batting over that. I am not so certain that my listening skills will allow me to "tune" my room by facing the tubes certain which ways, but at least I have the option of doing so and maybe having a little fun with it.
Sounds like your initial impressions of the Risch tube traps are similiar to my own. I am not easily impressed with most tweaks, went through several for my Rega TT (platter mats, vta adjustor, solid aluminum subplatter) and was totally underwhelmed. Have some cheapo interconnects and some that cost a couple hundred, cannot hear differences between them....mostly. Same with wire. (with the improved resolution maybe that will change too!).
Soooo...I built the first 2 tube traps and almost immediately knew I was onto something. The most pronounced imnprovement is that certain instruments are brought more into the foreground, sounds that had been "masked" by the now tame rogue bass waves are clearly more "there" . To use a Fremerism there is more there there.
It is not just different, it is better.
The second two, which will be done soon, took less than half as long as the first two. The learning curve is quite short.
If you buy your circles precut it might be best to calculate beforehand exactly how many you want to build and buy ALL the circles at once. What was a 16" circle at one Lowes store was only 15.5 at another. And often times there was only particle board circles available instead of plywood. Particle board will work well for the inner circle though if you use larger hammer type staples it will crumble away, or split the wood. Using a staple gun and minimizing any undue forces on the fencing/particle board jointure will do until you can apply the caulking gun glue.
For the inner stabilizing circles (two per Risch advice) I used the cheaper particle board, and simply lodged them into position placing a horizontal band of wire midpoint on the edge of the circle and then applied glue to the outer edges, no nails or staples.
All in all, I do think that the stereotype of the audiophile with the kilobuck amps and wires with the godawful rooms do exist for a reason, they are real.
Why most dont try this is beyond me. I used to think that furniture, drapes, carpet would accomplish the same things....they don't.
Tom
PS The only other tweak that I can vouch for is the recent addition of the PS Audio Duet power center. It made the sound more 3d and lowered the noise floor.
If I can find the charging cord for my digital camera i am gonna post some pictures...
"As far as the plastic on half, i have applied it over the outer fencing and then put the high loft polyester batting over that."
I believe that the plastic film should go over the poly batting
This is to reflect/diffuse the mid/high freqs
Placing it underneath allows the batting to absorb these freqs and defeats the "tunability" of the trap.
Just a thought
Julien
"There's someone in my head, but it's not me"
Tom,
Because the fiberglass I used was only 6.25" thick instead of the 6.5" that was specified in Jon's original plan, I used a 16.5" inner circle to yield roughly the same compressed density.
The 20" units were actually pretty easy to build as long as I had an extra set of hands to help when it came time to wrap the outer layer of fence around the fiberglass. At this diameter they are very stable, even when stacked to 10'. Once you build and install the 20" traps, I would be interested to hear how they perform compared to the 16".
I placed the plastic wrap around the outside of the polyester batting material, just under the burlap. From what I gather, the batting absorbs high frequencies, so placing the plastic outside of the batting would allow the highs to be reflected when the plastic faces the room.
I didn't know pre-cut circles were available when I sarted the project, so I bought a circle cutting jig for my router to cut them. I also used the router and jig to cut out holes in the center of the inner support circles. I uploaded a picture of one of my 3' traps, prior to putting on the fiberglass, that shows the hole.
I certainly agree with you that getting the room under control is one of the most effective things you can do to achieve more satisfying sound.
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