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Posted By: axiom_man ? on first reflections - 04/13/07 12:19 PM
Do you also do the first relection points on the 4 QS8 surrounds ?
Or do you want it to reflect
Posted By: dllewel Re: ? on first reflections - 04/13/07 01:54 PM
I would say you want it to reflect. Generally, don't treat the back half of the room, except maybe for the 1st reflection of the front speakers (back wall).
Posted By: SirQuack Re: ? on first reflections - 04/13/07 02:04 PM
I would not worry about it. There are some that treat their front wall as potentially the surrounds could reflect from them.
Posted By: axiom_man Re: ? on first reflections - 04/13/07 02:59 PM
Ok so do the first reflection points for the front three, but do not worry about the rear/side channels.
Posted By: SirQuack Re: ? on first reflections - 04/13/07 03:04 PM
In my opinion it is much more important to treat the corners of your room with "bass traps" first, and then follow up at some point by treating the first reflection points for the highs/mids. But that is just me.
Posted By: Hutzal Re: ? on first reflections - 04/13/07 03:08 PM
Quote:

In my opinion it is much more important to treat the corners of your room with "bass traps" first, and then follow up at some point by treating the first reflection points for the highs/mids. But that is just me.




I agree.

Hopefully I will be able to do some treatments in the next couple months in my room.
Posted By: real80sman Re: ? on first reflections - 04/13/07 03:34 PM
I am seriously thinking on installing the Owens Corning Basement Finishing System

They had a demo room set up at a local home show, and it was amazing how quiet the room was in this noisy arena.

Do you think that the room would be "too" dead with this? Would I end up having to install some hard reflective panels?

I really like the fact that the baseboards just snap on and off, and there is a channel that wires can be ran in. It would make sub placement and re-location very easy.
Posted By: axiom_man Re: ? on first reflections - 04/13/07 08:17 PM
Sir
The corner basstraps, I see them in your room do they really make that much of a diffence ?
how, why would sound go to a corner ?
what are your traps made out of ?
Posted By: jakeman Re: ? on first reflections - 04/13/07 08:17 PM
Thanks for pointing out the first reflections software. Its a nifty way to examine where to place treatments. One of my weekend projects is to rework several panels in my HT.

I came across this recent article which puts another spin on how and whether to treat walls based on the size of the room and how we perceive reverberation. The upshot is that in certain rooms too much treatment at first reflections may not make the sound more pleasant since it can effect reverberation in a negative way.

http://www.audioholics.com/education/aco...ent-perspective
Posted By: Hutzal Re: ? on first reflections - 04/13/07 09:23 PM
Quote:

Sir
The corner basstraps, I see them in your room do they really make that much of a diffence ?
how, why would sound go to a corner ?
what are your traps made out of ?




Bass frequency nodes gather in every corner in the room. When you put up a trap (Owens Corning 703 4" works well) it traps those nodes instead of them bouncing back into the room making a mess of your bass response.

The result is much cleaner sounding bass with more clarity. It helps alot in smaller rooms (mine is 15'10" x 14' 5" x 7'6"). I desperatly need some bass traps in my room. Since I just got the Axiom system (about 2 months ago) I am totally stoked about how they sound now and don't even notice it because it ALL sounds good to me now.

Af.ter I get some treatments I will notice how much it actually cleans up the overall sound.

goto ethanwiner.com for more info on room treatments.

-Hutz
Posted By: Mojo Re: ? on first reflections - 04/13/07 09:39 PM
Real80sman,

Is this finishing system CSA approved?
Posted By: real80sman Re: ? on first reflections - 04/13/07 09:44 PM
Quote:

Real80sman,

Is this finishing system CSA approved?




I'll have to check, but according to the site, the installation is different for Canada than the US.
Posted By: Ready_Acoustics Re: ? on first reflections - 04/14/07 05:05 AM
Just a quick note about reducing bass resonance in a room. Indeed ALL modes terminate in corners, and bass frequencies are dandy little culprits who end up there along with all of the others. The reason for bass trapping at all, is to reduce the resonance of the room, and to "decouple" (if you will) standing waves between parallel surfaces. One of the reasons I ask folks to consider using 4" thickness bass traps on the FRONT walls, is because speakers are often times situated so close to the front wall, (often times called a "boundry") that they help to resonate that wall easily and perhaps create a standing wave between that and another parallel surface such as the rear wall. Bass trapping on that front wall (and throughout the room in general) helps reduce overall resonances of the room. When you reduce the resonane and eliminate standing waves, your auditory senses can hear the clean sound from your sound source (speakers, sub) and not the additional resonance of the room. When the room is allowed to vibrate without treatment, it becomes part of the speaker system, thus creating that "whoom whoom" sound and destroying your sound system's full potential.

Using 4" thickness of rock wool (mineral wool) or mineral fiber (OC703) will go a LONG way to creating a more sound environment and much better sonic experience overall. And you don't need my products or anyone else's to make a HUGE difference. Placement is key as others have pointed out, but the "right" amount of absorption should not be overlooked.

I hope this helps?
Posted By: Ajax Re: ? on first reflections - 04/14/07 01:12 PM
Joel, that's one of the best down-to-earth, layman's explanation of room resonance, and what room treatments can do to help, that I've ever heard. Even I understood it. Bravo, and thank you.
Posted By: Wid Re: ? on first reflections - 04/14/07 01:30 PM

What Jack said, very good indeed. I am now thinking about some corner traps.
Posted By: St_PatGuy Re: ? on first reflections - 04/14/07 02:54 PM
Ditto what Jack and Rick said. Thanks for the input here, Joel--most of the time, I think, people don't spend enough time figuring out proper placement of his/her speakers and it may be the room that's the culprit of bad sound. The best part is that placement tweaking is free and can have the most profound effect on a system. I added some corner triangles to the top corners of my room, and those, too, had a significant impact on bass.
Posted By: Ready_Acoustics Re: ? on first reflections - 04/14/07 03:28 PM
Thanks for your kudos gents. I appreciate them very much. I hope that information helps others as well.

I'll do my best to help however I can.

Thanks again,
Posted By: CV Re: ? on first reflections - 04/14/07 03:36 PM
I want to say thanks, too, Joel. I think we're going to like having you around.
Posted By: alan Re: ? on first reflections - 04/14/07 04:10 PM
Hi Axiom_man and all,

I want to issue a cautionary note here. While I don't advocate long stretches of bare, highly reflective walls to either side of your listening room, I want to point out that first and secondary reflections from the sides of a room, largely produced by the off-axis dispersion of the front left and right main speakers (and, to a lesser degree, the center channel) generate important psycho-acoustic cues that add a sense of spaciousness and breadth to the soundstage, whether it's multi-channel movie soundtrack playback or simple stereo.

Much of Dr. Floyd Toole's early work in speaker measurement and testing (I sat on the listening panels for lots of tests) at the National Research Council Acoustics lab indicated that in typical rectangular living rooms furnished with normal domestic objects--rugs on the floor, bookcases or the like on the wall, upholstered furniture--the smoother and wider the off-axis frequency responses were for a particular speaker, and the closer they reflected the on-axis response measurements (in anechoic measurements), the more "spacious" and "realistic" the soundstage was perceived in double-blind listening tests.

So leave those first and secondary reflections alone, and do NOT overdamp your room. You'll end up with a dead-sounding space. I've seen too many over-"treated" rooms that had a kind of dead, sucked-out quality that was almost akin to listening on headphones to a dry studio recording.
If you add a lot of absorbent panels to dampen and soak up first and secondary reflections, you'll lose much of the desired spacious quality that well-designed speakers like Axioms with wide laterl dispersion generate.

One room I recently visited that was "professionally treated" had exactly those dry, sucked-out qualities. It was almost like listening to music in an anechoic chamber (a room with no echos). Paradoxically, this prominent reviewer's family room, which had no special acoustic treatment delivered a much more satisfying listening experience. And the bass in that room (from one EP500 subwoofer) had greater extension and power than the over-treated listening room, where four subwoofers were operating.

There is a place for bass traps when you have impossible standing wave problems; however, more often than not, the addition of a second subwoofer will greatly smooth out deep bass distribution to multiple listening locations.

Regards,
Posted By: Scott_R_Foster Re: ? on first reflections - 04/14/07 06:13 PM
Alan:

You might find this short article interesting which expounds on another element of Toole's recent work and the importance of NOT over treating small rooms with absorptive elements [specifically as such relates to speech intelligibility and center channels and more generally the inapplicability of paradigms developed for large spaces to small rooms].

http://www.audioholics.com/education/aco...ent-perspective

While I have long understood the importance of the caution to not over treat critical listening spaces with absorptive elements, I would object to the idea that early reflection control and similarly located absorptive placements implemented to diminish SBIR interference are in and of themselves bad ideas. Collaterally I would readily agree that modal resonances and early reflections are not bad things... its all about balance in my opinion, you can have too much early reflection input and garble the stereo image – you can have too much absorption and render the room dull. Neither is best practice.

We have found by that taking a broadband approach to absorptive treatment of small rooms [using absorbers on the order of 4” minimum thickness which work more or less smoothly at all frequencies – lows, mids and highs] one can greatly reduce the surface area of absorptive treatment used overall and in such cases yield a critical listening environment that does incorporate a modest amount of early reflection control but retains a stellar “spaciousness" and a “realistic the soundstage”. This approach also saves money in that you use fewer panels, and can achieve smooth low frequency response with fewer subs.

When properly balanced in a room with rational fixtures and finishes we find that modest early reflection control can enhance the depth and clarity of the illusion of the stereo image, diminish SBIR problems, and make for a larger “sweet spot” without killing the “snap and sparkle” of the room, or causing speech intelligibility problems.

Also, low frequency control through absorption is in our experience not simply a matter of dealing with “impossible standing wave problems”… but rather a means to smooth out the rough responses inherent to all small rooms arising form low modal density at low frequencies and unavoidable SBIR problems. Here is an example:



The above graphic is a series of 13 low frequency response measurements taken in a small room. The first frame is a bare room with no treatment. Each successive frame is the same measurement taken after the addition of a single 4” thick absorption panel. In the thirteenth and final frame a total of 12 panels have been added. Note the significant smoothing… this sort of treatment makes a profound difference in the accuracy of your system low in the band of audible frequencies.

Controlling low frequency distortion and smoothing the system/room responses at low frequencies and diminishing SBIR distortion can greatly enhance the listening experience – and diminishing strong early reflections can greatly sharpen and clarify the stereo image. In my view, the trick is to find ways to accomplish this without making the room exhibit “those dry, sucked-out qualities” you properly caution against.
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