Treating First Reflection Points - Question(s) - AVS Forum
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Old 06-11-2013, 03:47 PM - Thread Starter
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I'm working with an extremely limited budget of <$1000 for treatments.

I attempted to calculate the first reflection points, and I'll follow this up with the mirror-technique, but I came up with a couple questions based on the drawing below:
LL

The couches are micro-fiber material, over-stuffed style, FYI. The sub (not shown) is on the left side wall, 5" from the wall.

The calculated reflection points on the left side of the listener pass through into the adjoining room. Due to budget constraints, I'm wondering if I can "get away with" ignoring this wall (for now), or if some level of treatment here would still be recommended? Got thoughts?

The couch on the right side of the listener is only about 2 inches lower than tweeter level. The calculated reflection points are, therefore, just a few inches above the couch back. Mounting panels here would put the calculated reflection point at the bottom of the panel. Are there any special considerations for this? Moving the couch is not a wife-approved option.

How much higher than tweeter-level should panels extend? Perhaps 2'x2' traps behind the couch would be enough?


I see the tri-corner, super-chunk style of bass trap is very popular - however it's expensive. I can't find the quote now, but I thought there was "minimal" gain when using a full corner trap over a panel positioned across the corner. Using GIK pricing, 4 tri-corner traps, for example, amount to appx $520 (without shipping) whereas 4 bass trap panels would cost only $280. In a tight budget application like mine, what is the biggest bang for the buck here? Should I really "splurge" for those tri-traps (or a similar DIY option)? Can I "get away with" the bass panels straddling the corner?

As usual, any and all comments or suggestions are welcomed.

....
P.S.
Rough rendering of potential placement:
LL
(GIK Panels used for example: Total Cost $550 - shipped)

Right-side: 3-gik-242-wall-panels 24x48x3.5"
Front Corners: 4-gik-244-bass-traps: 24x48x5.5 - stacked 2 per corner
Left-side: nothing
Back-Wall: N/A (open to bar/kitchen area)
Floor: Area rug
Ceiling: nothing

Recommendations?
For an additional $50/panel, I could add "scatter plates".

Pending REW analysis and in-home recommendations from installers, does this seem to be a realistic first-step for acoustic treatment of this space?
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Old 06-13-2013, 11:29 AM
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Kudos, you're definitely on the right track. You don't mention the ceiling, but if I recall correctly from your other thread you are graced with high, sloping ceilings, so they may not create a direct, hard first reflection.

I would maybe consider front right corner placement for the sub, keeping in mind corner sub placement has it's pros and cons. Not sure what sub you have, but particularly if it's sealed, and you're limited to using just one, corner placement may pay greater dividends than the problems it creates.

I would encourage you to get a calibrated mic and REW, or alternatives (but they all cost a bit more) and learn to use it yourself. You'll save a bundle over outsourcing, and grow your brain at the same time!
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Old 06-13-2013, 01:11 PM - Thread Starter
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Thanks Wayne! biggrin.gif

The UMIK-1 mic from Cross-Spectrum Labs is in my future, for sure. It doesn't handle a loop-back feature, but from what I've read it will be quite adequate for my needs. I understand that a certain level of acoustic treatment "can't hurt" - there are adages such as "you can never have too many bass traps". However, as much as I want to "just fix it", I also know I'll feel more comfortable in my investment if I know exactly why I bought what I bought, and what it did for the overall sound. Measurements will give me that, without needing to relay on my ears (or the ears of others).

I've posted before how REW is a bit intimidating with it's graphs and information overload, but it's not so intimidating that I'm willing to blindly throw money at a problem without knowing what I expect to gain, and being able to ensure that I've gained it! I'm resolving myself to slowing down the pace of my projects so that I can take the time to assemble the tools I need.

This doesn't mean I'll build DIY panels, but it does mean that I'll learn more about my room's acoustics before I buy any panels and will expect to see measurable results after I install them.

Speaking about learning more...you - and a consultant I've spoken with - both mention ceiling treatment. Admittedly this is a place I've neglected to think much about, and unfortunately it's not me who has those high sloping ceilings. I have a flat 7'11" ceiling (just shy enough from 8' to cause some custom-needs regarding various floort-to-ceiling corner options).

So that I can clarify my understanding: the location of the ceiling reflection point is 1/2 way between the listening position and the speaker - measured on-axis, correct?

In my example where the listener is 10' from each speaker, I would then measure 5' along the L/R axis and attempt to provide coverage between (and around) the 2 points I mark?

I've gotten some advice that 1 2'x4' panel mounted horizontally on the right side wall could cover both reflection points "well enough" - allowing me to use the 2 additional panels on the ceiling. The reverse might also be true, where the ceiling reflection points are close enough to allow a single panel to be hung as a "cloud" - allowing me to place the other 2 panels wherever. In the GIK packaging, panels come in a box of 3, so I'm trying to use just 3 panels in this initial stage.

I'm also being encouraged to "splurge" for the tri-traps instead of hanging a bass panel so that it straddles the corner. I'm still waffling on that too.

Luckily, I have plenty of "waffle time". biggrin.gif
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Old 06-13-2013, 07:01 PM
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The mirror trick works for he ceiling as well. That's a low ceiling, so treating it will help out, particularly if your speakers don't control vertical directivity inherently. My preference follows the Toole approach in that a little lateral liveliness is beneficial. I'm picturing two (or three) "clouds" and a single horizontal panel on the wall to the right. [edit: one of these days I'll learn to read, I see you're already contemplating that arrangement.]

You're doing it methodically. Assess the problem first, then implement the solutions as needed.

Pics and feedback when your done, or else! And good luck.
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Old 06-20-2013, 11:37 AM
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Measurements first... define the problem before you throw money at it.

What you do next depends on what you want. If you're enamoured by the sound of recording studios, you're on the right track... except no one likes to listen in a recording studio; it's a work environment.

If you want your speakers to disappear into an enveloping sound field, start over. You're on the wrong track to get there.

"Good" sound depends on the listener, so even before you take measurements, figure out what you want out of the room.
- My HT room has a lot of furniture, and I can point to speaker locations in stereo. Multichannel programs are another story.
- My living room has less with no treatment, and "good" speakers disappear.

Figure out what you want, then take data to find out what you need to do to get there.

HAve fun,
Frank
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Old 06-20-2013, 11:48 AM - Thread Starter
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Quote:
Originally Posted by fbov View Post

If you want your speakers to disappear into an enveloping sound field, start over. You're on the wrong track to get there.

Just when I thought I knew what I was doing - here comes Frank. biggrin.gif

I've resisted posting any more because I've spent too much time talking and not enough time doing, I wasn't going to post until after I had some measurements.

But this quote threw me off, and I've gotta know what you mean....
...treatments won't help the speakers disappear?

Like you mention in your HT room, pin pointing speakers with 2-channel sound is expected (and enjoyed), but with multi-channel programming I'm wanting those speakers to disappear.

Wrong track?
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