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A bigger trap in the corner

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A bigger trap in the corner

Post by Jim Treanor » Fri Nov 30, 2012 8:54 pm

A few days ago I decided to "steal" a 42"-tall section of the 16" ASC Super Trap stack at the rear of my main listening room (all right, it's the living/dining room) and substitute it for the 11" trap that sat atop the Mc MR77 tuner in the room's right front corner. The "new" look:

Image

Image

(The large circle in the diagram is the 16-incher, the intermediate-sized are 11-inchers, and the smallest are 9-inch traps. The red line inside indicates the orientation of each trap's diffuser section, all but one of which point into the listening area. And, yes, the large trap's mounting is inelegant, but I'll remedy that with a DIY'd oak platform that elevates the trap and provides enough vertical space above the tuner for proper ventilation.)

While the combination of the originally-installed 11" corner trap and the 9" trap ameliorated the reflection problem created by the 40" flat-screen TV to a large extent, I wanted to see if a 16" trap would improve the illusion of soundstage breadth and depth right-of-center. It did more than that, rendering the whole left-to-right soundstage a far more cohesive whole than previously, increasing both its perceived depth (where recordings include that information) and beyond-the-speaker breadth, rendering lower bass more perceptible, tauter, and detailed, and rendering massed instrumental and vocal tuttis more defined and dynamic. Well-miked recordings have a more "walk into and join the performers" feel to them as well.

Needless to say, the 16" trap stays where it is--once I build the platform for it.

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Re: A bigger trap in the corner

Post by admin » Sat Dec 01, 2012 10:13 am

That's one pretty serious trap setup. Have you considered mounting the large 16" trap in the right front to the ceiling? That way you wouldn't have to build a support structure for the bottom portion and it would maximize the area under the trap. I don't know if that is feasible or not with the ceiling but it may be worth looking into.
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Re: A bigger trap in the corner

Post by Jim Treanor » Sat Dec 01, 2012 12:23 pm

While it would be possible to ceiling-mount the trap, I want the flexibility of moveability should the need arise. (Mrs hasn't noticed the change yet. :D )

I'm planning as well to DIY a new equipment console for all the audio and video equipment (including the flat screen) installed in that corner. The cabinet holding the 17LS and MF2500 will be one of the console modules used for other equipment, floor-based and sitting to the left of a taller matching cabinet whose components will include the line stage, amp, and the tuner, which will no longer be sitting exposed in the open. The trap will sit atop that. And the "look" will be more integrated.

Spent a lot of time yesterday listening and continue to be surprised at the degree to which the change in trap size in that corner has virtually negated the reflective liability presented by the flat screen and the two adjacent glass-framed prints as well as improved the delineation of bass and lower midrange. I think the explanation is twofold: lowering the frequency at which trap absorption is effective (from the 11-incher's 90Hz to the 16's 40Hz) has cleared out wall-and-ceiling-corner-generated standing-wave "mud" that obscured (in some cases, buried) midbass-to-lower-midrange detail; and the broadening of trap diffusive-section coverage has increased the randomization of reflections that previously mucked up the perception of recording-embedded information higher up the frequency ladder (from about 400Hz on up). Another benefit is a considerable improvement in dynamic contrasts.

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Re: A bigger trap in the corner

Post by Jim Treanor » Mon Dec 03, 2012 7:09 pm

Here's a better look at what I have to contend with up front. As you can see from the knick-knacks, etc., this room is very "lived in," and the inclusion of what my wife quaintly calls grey-mix "Greek columns" would drive an interior decorator batty. Nonetheless (and though I wish I could extend the leftmost traps to ceiling height), they work surprisingly well in ameliorating the negative effects of the massive reflective surfaces, enough so on well-recorded material to make the speakers "disappear." (The character atop the leftmost trap is a stuffed bear Mrs brought home from Starbucks a couple of days ago. She bought it because she thought it looked like Lieutenant Kije [surprisingly, it's a reasonably close lookalike to the photo'd character gracing the LP jacket cover of Reiner's Living Stereo performance] and would be an appropriate addition to the listening room.)

Image

Image

As noted earlier, I'll build a new equipment console--and in the process will be able to lower the vertical footprint (and its associated reflection) on the right by about 7". At that point I'll substitute a 48"-tall 16" Super Trap for the 42"-high trap there now.

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Re: A bigger trap in the corner

Post by admin » Tue Dec 04, 2012 9:31 am

Definitely can see the acoustic challenges with that room. Let me ask, did you ever consider mounting the flat screen over the fireplace? It may free up some space on the equipment rack and you could move the turntable from in front of the fireplace. The other potential option that the two of you may want to discuss is putting tapestries up on the front wall instead of the glass posters. If you put a tapestry up, you can mount rather large acoustic panels behind it and they would not be visible. Also have you ever tried to put the traps right in the back of the speaker, maybe only an inch or two away as to act as a barrier between the speaker and the front wall. I once saw a setup where somebody put a trap right on the back an electrostatic speaker to stop the back wave. It may help the sound, or ruin it,... difficult to predict but may be interesting to try.

These are just some ideas as it seems like you put a lot of effort in sound dampening. It seems like a very nice room to do some serious listening in but I can see your difficulties with all those hard reflective surfaces. Good luck, keep us informed! :)
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Re: A bigger trap in the corner

Post by Jim Treanor » Tue Dec 04, 2012 12:09 pm

I once mentioned the option of mounting the flat screen over the fireplace. Once. :lol: (Actually, given the proximity of seating to the front wall, the viewing angle would be moderately--read "potentially stiff-neck"--steep.)

The prints stay, though I've considered the possibility of flanking them down the line (that would be a long way off, involving quite a bit of persuasive selling--even then, I'd be pushing my luck) with wall-mounted with 9" or 11" half-traps. I've also tried a number of floor-based trap configurations, including a modified "attack wall" setup which sandwiched the speakers between 9" traps. While that was effective in controlling reflections and improving focus, the current setup provides the overall best sonic balance and most "you are there" illusion with good recordings.

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Re: A bigger trap in the corner

Post by admin » Sun Dec 09, 2012 5:39 pm

I guess another possibility would be to place the TV in front of the fireplace as opposed to mounting it above. From the proximity of the traps on the fireplace lower mantel and location of the turntable I am presuming you don't actually make a fire in there? It's questionable if you would want to cover the fireplace up however as it does look nice.

Last but not least another option is to put the TV on a roller TV stand. I know one person that did this with a modification to a fireplace. In that case it was somewhat unusual in that he had a fireplace he never used. He actually put his stereo equipment into the fireplace and had the TV on a moving stand that had floor rails that would slide off to the side to access the stereo equipment and then slide the TV back center while viewing (and cover up all the equipment). It was an interesting design. I was very surprised that it looked quite nice as he had built the custom sliding cabinet/TV stand and did wire management and lighting inside of the fireplace alcove.
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Re: A bigger trap in the corner

Post by Jim Treanor » Sun Dec 09, 2012 9:11 pm

Actually, the simple addition of a floor-standing three-foot-tall 9" trap to the corner of the intersection between the audio/video equipment cabinet and the right wall has, in combination with the 16" Super Trap earlier substituted higher up, rendered negligible whatever sonic effects I'd attributed to the 40" TV's reflective surface. The right side of the soundstage now integrates totally with the left in terms of the presentation of depth, image focus, instrumental/vocal detail, and placement, and overall spatial perspective. Where the information is embedded in the recording, instruments or voice appear well beyond the outer boundaries of both speakers, as does the perception of appropriate depth of the soundfield. So relocation of the TV is no longer a consideration.

I was surprised at the magnitude of improvement effected with the single 9" trap. But it makes sense, given the proximity of the right speaker to that corner (effectively a standing wave generator) and to the reflective surfaces presented by the line stage, amp, and tuner panels. The "best" trap orientation is with the fully absorptive hemicylinder facing the speaker (in other words, the diffusor/absorptive center faces straight at the intersection of the equipment cabinet and the wall).

Here's how trap placement looks as one faces the front wall:

Image

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Re: A bigger trap in the corner

Post by Mcbrion » Wed Mar 27, 2013 11:13 pm

Hi Jim:
As you are one of the few people with Tube Traps that I know, I have a question for you.

I have, per Peter Moncrieff's original tube trap suggestions, back in '89, set up my traps using his suggestions. See hyperlink below:

http://www.tubetrap.com/bass_traps_articles/iar89.htm

He has the absorptive side facing into the room. Now, perhaps I'm reading your diagram wrong, but you appear to have the reflective side facing into the room. Am I correct on that point?

I have around 40 tube traps, and have had them since 1988. I have 2 -16" full rounds, 2 - 13" full rounds, 11 - 11" full rounds,13 - 9" full rounds, 5 - 16" quarter rounds, 4 - 9" half rounds, and 8 sound planks and 3 tube traps I've broken the internal parts (moving from West Coast to East Coast did it!).

I'm very fascinated that you have the 16" traps behind the speakers - which is the best place. I had to move the 16" trap from that corner behind the speaker because it's where the door opens, and people had to squeeeeeeeeze into the room (if I'd known I was moving back to the house I grew up in, I'd have had the contractor, when we added an addition to the house, move the door to the middle of the room!). As it is, I'm going to move the 13" trap from the entrance (easier to get in) and put it in the corner in the back of the room, where the 16" trap resides, with a 11" one on top of it.
I've also found it best NOT to put two different size traps on top of each other, as it "confuses" the imaging and timbre somewhat, but I do have two locations where it was unavoidable, due to the odd number of traps (I had a LOT more back in San Francisco, around 50 and 9 of them were 16" full rounds!)
Since I have a dedicated music room, I can place the traps wherever I want, but I just found this site 10 minutes ago, and as soon as I finish this entry, I'm going to reverse the placing of the 16" and 13" and see what happens sonically.
Thanks for the photos: it's great to see how traps are actually placed in someone else's room, although I'm pretty comfortable with mine. Have you noticed that moving them down the wall simply by pushing them with your index finger so slightly it appears they haven't moved at all does rather unbelievable things to the sound, particularly low-level detail and transients?

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Re: A bigger trap in the corner

Post by Ian Millar » Sun Jul 07, 2013 3:20 am

IMO none of these room treatment products are worthwhile. You can achieve the best bass trap in the world simply by opening a window or door.

I have achieved near ideal RT60 figures (quite flat 0.4s) in the critical 250Hz to 4kHz band without a single specialised item - just furniture, carpet and curtains.

If you read Floyd Toole's book instead of paying shonky retailers for silly-looking panels etc, you can have a good sounding system in a room that looks like a room instead of a side-show venue.

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Re: A bigger trap in the corner

Post by admin » Sun Jul 14, 2013 9:49 am

Ian Millar wrote:IMO none of these room treatment products are worthwhile. You can achieve the best bass trap in the world simply by opening a window or door.

I have achieved near ideal RT60 figures (quite flat 0.4s) in the critical 250Hz to 4kHz band without a single specialised item - just furniture, carpet and curtains.

If you read Floyd Toole's book instead of paying shonky retailers for silly-looking panels etc, you can have a good sounding system in a room that looks like a room instead of a side-show venue.
Ian,
I think you make some really valid points here. With careful placement of furniture, carpets, curtains, windows/doors open the sonic improvement can be dramatic. It's not that these changes are not worthwhile, rather, often you simply can't do the actual changes due to many other reasons.

For example, in my listening room, I also use the space for watching movies in addition to listening to music. That means I can't move my couch to the left or right, or suddenly I'm watching everything at an angle. Also, moving it back or forward changes my viewing angle, which I currently have optimized to THX recommendations. I have one side door, but if it is open, then I get a massive light leak into the room during the day. I have a set of windows behind my screen and behind a large shelf where I store media so I would literally have to move furniture around if I wanted to open and close these (not to mention I live up North so opening a window during winter is not a viable option anyway). I have put up numerous curtains, a large rug, just as you suggest (but frankly they cost a lot more than my 150 panels of acoustic treatment).

I think if you can get away with changing your home decor, that's great, and that should be the first thing you should try. However, this is sometimes not possible due to the design of the room, other household member opinions, etc... However, You can get rather inexpensive acoustic foam if you look around the larger foam suppliers vs going to the local audiophile shop and that can often significantly help the acoustics of the room as well. Each environment is unique and some will need almost no modification from the start, others may need quite a bit.
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Re: A bigger trap in the corner

Post by Jim Treanor » Mon Jul 22, 2013 8:51 pm

Mcbrion wrote:Hi Jim:

He has the absorptive side facing into the room. Now, perhaps I'm reading your diagram wrong, but you appear to have the reflective side facing into the room. Am I correct on that point?

I have around 40 tube traps, and have had them since 1988. I have 2 -16" full rounds, 2 - 13" full rounds, 11 - 11" full rounds,13 - 9" full rounds, 5 - 16" quarter rounds, 4 - 9" half rounds, and 8 sound planks and 3 tube traps I've broken the internal parts (moving from West Coast to East Coast did it!).

I'm very fascinated that you have the 16" traps behind the speakers - which is the best place. I had to move the 16" trap from that corner behind the speaker because it's where the door opens, and people had to squeeeeeeeeze into the room (if I'd known I was moving back to the house I grew up in, I'd have had the contractor, when we added an addition to the house, move the door to the middle of the room!). As it is, I'm going to move the 13" trap from the entrance (easier to get in) and put it in the corner in the back of the room, where the 16" trap resides, with a 11" one on top of it.
I've also found it best NOT to put two different size traps on top of each other, as it "confuses" the imaging and timbre somewhat, but I do have two locations where it was unavoidable, due to the odd number of traps (I had a LOT more back in San Francisco, around 50 and 9 of them were 16" full rounds!)
Since I have a dedicated music room, I can place the traps wherever I want, but I just found this site 10 minutes ago, and as soon as I finish this entry, I'm going to reverse the placing of the 16" and 13" and see what happens sonically.
Thanks for the photos: it's great to see how traps are actually placed in someone else's room, although I'm pretty comfortable with mine. Have you noticed that moving them down the wall simply by pushing them with your index finger so slightly it appears they haven't moved at all does rather unbelievable things to the sound, particularly low-level detail and transients?
Sorry I haven't responded sooner, but I've been away from here for awhile. Here's the current trap layout (plus a couple of dining-room-table-mounted 2'x2' SRL Acoustics diffusers installed during "serious" listening sessions):

Image

When I had a dedicated room I started with the Moncrieff alignment, but quickly abandoned it because it sucked the life out of the music. In the current crazy-quilt setup, I've set the absorptive/reflective alignment as diagrammed to cope with the varied surfaces that room design and furniture placement give me to work with. It's not ideal, but best-case given the circumstances.

You'll note that the 16-inchers are at room rear, a consequence of space available. I've eliminated multi-diameter stacks for the reasons you mentioned.

Yes on the effect of even slight repositioning.

(There has been one new acquisition as of mid-April--a cat. Even though she's in the room much of the time, she stays clear of the scratching-post-tempting traps because immediately prior to her arrival I sprayed the base of each trap with cat repellent, then sprayed them again once per week for the next two weeks. It worked.)

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Re: A bigger trap in the corner

Post by Ian Millar » Wed Jul 24, 2013 4:37 am

The most effective traps in that layout are the openings into other rooms and there is an horrendous asymmety brought about by the opening at top right which your traps at bottom right do not help since they are "tuned" to absorb different frequencies. The commercial room treatment offerings are nothing but expnesive clutter and are far less effecting than say changing a leather-clad lounge suite for a fabric one. The high-frequency diffuser at mid left (behind the seating position) do nothing more than a bookcase with a few books and ornaments. If it included Floyd Toole's text it would serve you much better.

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Re: A bigger trap in the corner

Post by Jim Treanor » Wed Jul 24, 2013 11:22 am

Ian Millar wrote:The most effective traps in that layout are the openings into other rooms and there is an horrendous asymmety brought about by the opening at top right which your traps at bottom right do not help since they are "tuned" to absorb different frequencies. The commercial room treatment offerings are nothing but expnesive clutter and are far less effecting than say changing a leather-clad lounge suite for a fabric one. The high-frequency diffuser at mid left (behind the seating position) do nothing more than a bookcase with a few books and ornaments. If it included Floyd Toole's text it would serve you much better.
You've heard music reproduced in that room, right?

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Re: A bigger trap in the corner

Post by Ian Millar » Thu Jul 25, 2013 8:11 pm

Nope. I wouldn't need to. Read Toole yet? Run any impulse responses for left and right channels individually or any at all? Done a spatial average? I've done mine. I assure you that room is all over the shop and no absorption "product" that could fit inside the room can fix it.

WIth that opening you basically have the left speaker firing into twice the acoustic space c.f. the right speaker. A way to correct the bass part of it (other than rearranging the room for better symmetry) would be with a stereo low frequency multi-band equalisers (say 8 bands from 25Hz - 125Hz) or DSP. You'd need to knock off 10 or more dB from some of the right speaker bands. For the higher frequency ranges all you need are ordinary objets d'art of varied size and shape to scatter the reflections randomly. Then a fabric covered lounge, rugs, curtains and carpets as absorbers.

That you purchased brand name "producs" does not make for a nice sounding and enveloping space. It seems very random and unscientific indeed.

And what's with this practice of quoting an entire post? Everyone can read it the first time around.

BTW, once you had it corrected, it wouldn't matter too much that you had C-J amps or inexpensive kit amps up front for the basic gain stages.
Last edited by Ian Millar on Thu Jul 25, 2013 8:55 pm, edited 1 time in total.

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Re: A bigger trap in the corner

Post by Jim Treanor » Thu Jul 25, 2013 8:26 pm

Ian Millar wrote:Nope. I wouldn't need to.
That says it all.

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Re: A bigger trap in the corner

Post by Ian Millar » Thu Jul 25, 2013 11:19 pm

I don’t think so. I have plenty more.

Why would you post your floor plan if you considered it meaningless or weren't open to scrutiny? Perhaps you are just trying to be proud.

I have been through the process and can tell you that you are wasting your time and money with commercial bass traps.

Simple downward EQ of selected frequency bands at line level would relieve your power amplifier of the burden of amplifying frequencies that the room is exaggerating. Why waste the acoustic energy to then vainly attempt to absorb it with over-priced commercial "absorber" products that absorb nothing that soft furnishings can't?

In order to balance left and right in that room with that particular speaker layout, the opening at top right in the plan could be closed.

I have a similar asymmetry problem with my upstairs room and am about to add a stereo eight by 1/3 octave band (25 – 125Hz) EQ PCBs to address it. It could also be attempted using JRiver's DSP Studio feature, however there would be no way of verifying that the digital filters actually worked in the room with subsequent impulse response measurements since the filters are not able to be connected to the measurement software.

FYI here is my asymmetrical response as measured from the sweet spot:

Image

Red is right channel. Blue is left. Black is both run simultaneously. As you can see it is all over the shop. And there is nothing that can be done about the 200-300Hz floor bounce suck-out. The left channel 40-60Hz peak can be attenuated at line level, as can the right channel 65Hz peak etc.

If closing your opening is impractical then you can attenuate selected frequency bands. At present since the left and right are mismatched by your room, the right woofer(s) are undergoing unnecessary excursions and the associated distortion is the result. The absorbers do not absorb distortion. This could be corrected to some extent for your right speaker with EQ. Unfortunately, EQ cannot help your left channel low frequency response as "boosting" will cause additional cone movements for no acoustic gain.

Here is what I was able to achieve downstairs:

Image

There are no commercial so-called acoustic treatments in the room and as mentioned before, the decay times are near ideal.

The blue trace had the microphone at an original seating position and the red trace was taken after moving the seat forward to take advantage of a natural 100Hz room node. Every single one of the 8 bands (20-100Hz in this case) had to be tweaked to achieve this outcome.

You cannot do this with bass traps. If you have not run impulse response measurements, then you couldn't possibly know which frequencies to even target.

Your approach is quite random and unscientific and any perceived benefits will be a result of luck or placebo.

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Re: A bigger trap in the corner

Post by Jim Treanor » Fri Jul 26, 2013 5:50 pm

Ian Millar wrote:I don’t think so. I have plenty more.
Perhaps you are just trying to be proud.
No, Ian, I was simply responding with a graphic to Mcbrion's post to indicate the updated setup in a problematic room. Much simpler and more efficient than describing the layout in words. Much as are your frequency graphs.
I have been through the process and can tell you that you are wasting your time and money with commercial bass traps.
I'm glad you're happy with your EQ'd setup. But we differ in our assessment of trapping. For one thing, you refer to "bass traps," and while that's a major function of the ones I use, they also provide a form of "diffusion" above 400Hz that, given their semi-cylindrical limp-mass design, is probably better described as "controlled reflection" or, alternately, dispersion. That capability, and their orientation flexibility in deployment, has proved useful in dealing with specific-location situations where an absorption-only approach would have effected too much deadening manifested as "life sucked out" of the music. So, in my setup, at least, they perform two functions.

For another, you've claimed that traps or other commercial passive acoustic control devices are no more effective than books as acoustic treatment. That's demonstrably wrong in my experience (and in that of a couple of experienced audio dealers who heard the comparison when I had my dedicated room). One of the problems with that assertion is that there is no generic "book." Your have cloth- or buckram-covered hardbounds, some of which are dust-jacketed, and paperbacks. There's also may be spine curvature, particularly in hardbounds to consider. The variations in cover composition and configuration (and consequent reflectivity and/or absorption) do not--say short of filling your bookshelves with nothing but Britannicas--provide a uniform standard with which to control whatever acoustic artifact you're attempting to deal with. Their effective "operating frequency range" is also restricted. Given those limitations, expect to have to deal with comb filtering. While books are better than a bare wall in this situation, I certainly haven't found a filled bookcase at first or second reflection points anywhere near as effective as a "trap" designed for that purpose and whose operating parameters are known. In both my dedicated-room and current-room setups, the most effective function books with their densely-packed paper pages perform is to "stiffen" the wall behind the filled bookcase and in the process reduce the bass-suckout flexure of that wall. So books can certainly be used to advantage, but not as you suggest.

I recognized the room-opening asymmetry issue years before you brought it to my attention. You can disagree all you want and graph your room to death, and that's fine with me, but the trapping (and the noted "controlled reflection" alignments) indicated at the right front and just forward of it (and in conjunction with the front-center trap) solved the left-right lateral, front-to-back, and frequency balance issue presented by the non-reflective, non-cornered room opening. In large part that's because they control the effects of the myriad reflective surfaces (glass, equipment faceplates, a 40" flat screen, fireplace tile) that are necessarily shoehorned or otherwise architecturally "hardwired" into that space and with which the physical, and not simply the frequency, components of sound transmission have to cope.

Call it random, call it unscientific, and treat me like I'm a wet-behind-the-ears kindergartener if that makes your day, but in the end I've made the room work for those who've listened to music in it. If you've done the same in yours, great.

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Re: A bigger trap in the corner

Post by Ian Millar » Fri Jul 26, 2013 8:52 pm

Toole P 266: 'Without your own acoustical measurements, you are "flying blind"'.

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