Acoustic preparation of theater room questions. - Page 2 - AVS Forum
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post #31 of 45 Old 06-19-2009, 05:19 AM
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The only furniture which could make a difference would be the seating (sofas, recliners, etc).

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post #32 of 45 Old 06-19-2009, 05:26 AM
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Quote:
Originally Posted by Dennis Erskine View Post
Understand the Welti approach provides consistent bass response in the seating area ... not necessary smooth bass response. I've been using two primary subs in the front of the room and three smaller asymetrically placed smaller subs for the past 15 years. The positioning of the three smaller subs is determined by estimating the interaction of the subs (ala Gerry Lemay's Virtual Subwoofer process) within the planned seating area. Several of those rooms have not required EQ ... Jamin has experience in one of them.
The mid-point solution can be very smooth in both space and frequency domain - because it is virtual the same as subs at the 1/4 corners inside the room which kills off the first three L&W modes. The only problem is when your room is small it pretty much guarantees someone is going to be overwhelmed by one sub or the other. This example is a 19x12x8 - a fine solution for the two seater stereo room planned.

 

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post #33 of 45 Old 06-19-2009, 06:15 AM
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Exactly, the Welti approach (from the paper) provides consistent bass response ... not necessarily smooth bass response. Which is to say, you could have smooth bass response; but, not necessarily.

Your model would indicate a high probability of success in this case providing the impedance of the walls/ceiling match the model's assumptions.

Haven't seen you around for awhile ... you adjusting to the pollen, heat and humidity?

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post #34 of 45 Old 06-19-2009, 08:34 AM
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Quote:
Originally Posted by Dennis Erskine View Post

The only furniture which could make a difference would be the seating (sofas, recliners, etc).

we are either going with two large soft leather sofas and a bar with 4 stools, or with two large soft leather sofas and two soft leather loveseats.

the room is 166" wide, 100" high, and I think about 244-266" deep
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post #35 of 45 Old 06-19-2009, 05:25 PM
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Size difference not as clear cut, but same general behavior.

I forgot to mention the prior example was with triple stack of subs at each midpoint wiping out any height modes. You can accomplish something similar (just not as loud!) by moving your four off the floor as much as you can to diminish that mode sticking out like a sore thumb (or if talented pEQ it out). This is shown in the 2nd plot, essentially the same response as the smaller room - just downshifted in level and frequency.

And of course Dennis is pointing out - a sealed concrete bunker will have a more defined response than floppy tract home walls which might be smoother or might be worse depending on what is behind your walls!

 

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post #36 of 45 Old 06-19-2009, 07:59 PM
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interesting.

Glad I'm going to build four boxes to test with.

With the four at mid wall I will have to deal with the gain from the floor boundry because the front sub will have to be underneath the screen. I could move the other three to the center of each wall however. Would this help or just screw things up?

An acoustically transparent screen is not an option because I am certainly more of a videophile than audiophile.

I will also see what it sounds like to place each sub half way up the wall in each corner.
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post #37 of 45 Old 06-19-2009, 08:33 PM
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Kraz ...
With your toy, here's a challenge. Based upon seating location "1" in your first plot, your 'moderate' zone curves toward the corners. I want it to curve toward the center of the side walls for curved seating. (It's too hot and humid to be in the garden anyway).

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post #38 of 45 Old 06-19-2009, 09:20 PM
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I think you may find that an acoustically transparent screen isn't as expensive as you think. Check out seymour AV. You can find a thread in the screen forum. They sell the material and have plans for frames that are very easy to follow. With a few hours work you could have an AT screen for less than a prefab non AT screen. You can then use 3 identical front speakers with the center behind the screen which is the ideal for acoustics
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post #39 of 45 Old 06-20-2009, 06:11 AM
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Quote:
Originally Posted by edfowler View Post

interesting.

Glad I'm going to build four boxes to test with.

With the four at mid wall I will have to deal with the gain from the floor boundry because the front sub will have to be underneath the screen. I could move the other three to the center of each wall however. Would this help or just screw things up?

An acoustically transparent screen is not an option because I am certainly more of a videophile than audiophile.

I will also see what it sounds like to place each sub half way up the wall in each corner.

The problem with one out of four on the floor is you canceled the height modes with the three halfway up, then bring it right back with the one on the floor - just not as strong as with four on the floor.

The four in the corner I don't like - kills of the odd modes, seriously boosts the even modes. You will have very strong nulls 1/4th from each wall constraining your seating. The thing to remember about Harman's patterns is they assumed parametric EQ to notch out the remaining modes - they are just making spatially symmetric patterns so this EQ can work over a broad area.

No more plots though - Dennis is trying to Tom Sawyer me into doing HIS rooms - I got garden weeds to attend to!
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post #40 of 45 Old 06-20-2009, 12:48 PM
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No more plots though - Dennis is trying to Tom Sawyer me into doing HIS rooms - I got garden weeds to attend to!

But YOU have the lava lamp. Now, as to those weeds ... my uncle (Alan Forbes) wrote a book on gardening "Bugs our Garden Friends". Net out ... the bugs prefer to eat on the weeds, so keep 'em.

With two subs ... one on the floor and one near the ceiling, you can handle the height mode(s) as well; but, not for a DIY unless you have lot's a patience and an easy to figger out PEQ DSP.

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post #41 of 45 Old 06-20-2009, 02:28 PM
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I've got lots of patience and time and I can probably stick another sub near the ceiling.
What's a PEQ DSP?
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post #42 of 45 Old 06-20-2009, 04:32 PM
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Quote:
Originally Posted by edfowler View Post

I've got lots of patience and time and I can probably stick another sub near the ceiling.
What's a PEQ DSP?

Parametric EQualizer in the Digital Signal Processor of your AVR (if it has one--for example, some Yamaha AVRs do so).
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post #43 of 45 Old 06-21-2009, 07:01 AM
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A pEQ allows one to choose the center frequency, gain and bandwith as opposed to a partial octave equalizer where this is fixed. Behringer puts out some cheap ones if your AVR is lacking. In the HAA we prefer the models from QSC, very nice PC GUI but no knobs to twiddle, and you need XLR-RCA adapters.
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post #44 of 45 Old 06-21-2009, 10:42 AM
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The QSC DSP322UA is an excellent piece and provides more capability than you'll typically find in a consumer AVR. (It will also cost you as much as a nice AVR)

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post #45 of 45 Old 06-27-2009, 05:39 PM
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Originally Posted by Suntan View Post

Jeez Dennis, who pissed in your cornflakes this morning? Giving him actual suggestions for good reading on one hand is nice, but taking him behind the woodshed for not knowing about them in the first place is a rather harsh stance. And no, your first post suggesting he just read more was not very helpful.

If you want to help people here and share your knowledge of the subject, that's really great. But the condescending overtones are not needed.

-Suntan

He's just pissed cause he can't fly his Aerostar anymore.

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