What happens when two subs take up a third of the wall? - AVS Forum
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post #1 of 16 Old 03-29-2014, 10:46 AM - Thread Starter
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Almost seems like the setup to a good HT geek joke, and of course the flip answer is "awesomeness" but what I am really asking about is placement.

What happens when two subs take up a third of the wall -- in terms of where to place them?

To optimize evenness across a single row of seats, placement at 1/4 the front wall, and 3/4 the front wall, tends to be a decent rule of thumb.

But subs these days of the high quality internet direct variety in particular are often 24 inches in size (cabinet) and my room is only 12' wide. So depending on which side "counts" I'm placing my subs at 1/4 wall, or darn close to 1/2 wall!

Does one measure from the center of the driver? What if there is a port on the back?

How about a dual driver -- with a driver on each side? Middle of the housing?

I absolutely should measure (REW) what's going on, of course, and tweak and shift based on that. But right now I have temporary subs, but need to make sure I am not constructing my screen wall in a way that precludes the most likely correct position for my future real subs.

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post #2 of 16 Old 03-29-2014, 12:52 PM
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Quote:
Originally Posted by nathan_h View Post

Almost seems like the setup to a good HT geek joke, and of course the flip answer is "awesomeness" but what I am really asking about is placement.

What happens when two subs take up a third of the wall -- in terms of where to place them?

To optimize evenness across a single row of seats, placement at 1/4 the front wall, and 3/4 the front wall, tends to be a decent rule of thumb.

But subs these days of the high quality internet direct variety in particular are often 24 inches in size (cabinet) and my room is only 12' wide. So depending on which side "counts" I'm placing my subs at 1/4 wall, or darn close to 1/2 wall!

Does one measure from the center of the driver? What if there is a port on the back?

How about a dual driver -- with a driver on each side? Middle of the housing?

I absolutely should measure (REW) what's going on, of course, and tweak and shift based on that. But right now I have temporary subs, but need to make sure I am not constructing my screen wall in a way that precludes the most likely correct position for my future real subs.

I would recommend from the center of the driver, from everything I've read --- horizontally AND vertically.

 

I've had a great response in evening out my sub's performance by raising it off of the floor ... And from what I've read, the 1/4 rule of thumb applies to the vertical dimension as well, although in most rooms that's pretty high off the floor ... I've compromised and have my subs on 9" platforms with the center of the drive sitting 17" off the floor (my ceiling is just about 100" ... easy math :-) 

 

At 17% off of the floor, it's not the Ideal 25%, but the aesthetic compromise is working fine for me.

 

Dual drivers ... I'd agree with the middle of the housing ... a pair of duals? Look out !

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post #3 of 16 Old 03-29-2014, 01:13 PM
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The room does not seem that large if it is 12 ft. wide. I guess the real question is how much and how many subs are needed for that size room.

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post #4 of 16 Old 03-29-2014, 02:01 PM
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In most cases you get better results with one sub in the front of the room and one in the back. With both in front both will excite the same reflection null off the wall in the back of the room.

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post #5 of 16 Old 03-29-2014, 04:45 PM
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Bill, if one is in front wall and another in the back wall, does it matter where the driver is firing? I current have my front sub fires toward the back wall where I sit and my rear sub fires toward the front wall. Thanks.
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post #6 of 16 Old 03-29-2014, 05:29 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

In most cases you get better results with one sub in the front of the room and one in the back. With both in front both will excite the same reflection null off the wall in the back of the room.

This is really important to achieve similar response across multiple rows of seating. In my case, I'm optimizing for only one row, and my understanding is that two along the front wall at 1/4 widths will generate consistent response laterally across a single row and let me optimize my EQ (reduce peaks) for all three seats in that row.

If I do the front and back wall locations, I will get less variation between the main row and the second row, from the models I have looked at, but more variation laterally in the main row (than placing both subs in the front of the room).

Am I being steered in the wrong direction?

More important: Where is the point one measures at?

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post #7 of 16 Old 03-29-2014, 05:31 PM - Thread Starter
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Originally Posted by derrickdj1 View Post

The room does not seem that large if it is 12 ft. wide. I guess the real question is how much and how many subs are need for that size room.

From a sheer output standpoint, it's a sealed 12x16' room and could easily be pressurized by a single capable sub.

From a consistency perspective, having two subs will let me get the bass optimized for more than one seat, which is important.

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post #8 of 16 Old 03-29-2014, 05:33 PM - Thread Starter
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Quote:
Originally Posted by TomC1315 View Post

I would recommend from the center of the driver, from everything I've read --- horizontally AND vertically.

I've had a great response in evening out my sub's performance by raising it off of the floor ... And from what I've read, the 1/4 rule of thumb applies to the vertical dimension as well, although in most rooms that's pretty high off the floor ... I've compromised and have my subs on 9" platforms with the center of the drive sitting 17" off the floor (my ceiling is just about 100" ... easy math :-) 

At 17% off of the floor, it's not the Ideal 25%, but the aesthetic compromise is working fine for me.

Dual drivers ... I'd agree with the middle of the housing ... a pair of duals? Look out !

Raising them off the floor is a super interesting idea. I've heard of such things, but now you are putting ideas in my mind that were not there, before.

I have a false wall/screen wall, and if I size the subs just right, I could ALMOST place one or both at any height.....


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post #9 of 16 Old 03-29-2014, 10:10 PM
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I would shoot for a more even response across all the seats. You can always run it a little hot.

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post #10 of 16 Old 03-31-2014, 08:55 AM - Thread Starter
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Originally Posted by derrickdj1 View Post

I would shoot for a more even response across all the seats. You can always run it a little hot.

I appreciate that but the second row is against the back wall and seldom used. It would be a big compromise to get things consistent for that row.

If I can optimize for the main row, that would be great.

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post #11 of 16 Old 04-03-2014, 12:01 AM - Thread Starter
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Quote:
Originally Posted by tvuong View Post

Bill, if one is in front wall and another in the back wall, does it matter where the driver is firing? I current have my front sub fires toward the back wall where I sit and my rear sub fires toward the front wall. Thanks.

No impact.

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post #12 of 16 Old 04-03-2014, 07:11 AM
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Bill, if one is in front wall and another in the back wall, does it matter where the driver is firing? .
The radiation pattern of subwoofers is omni-directional.

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post #13 of 16 Old 04-03-2014, 08:50 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

In most cases you get better results with one sub in the front of the room and one in the back. With both in front both will excite the same reflection null off the wall in the back of the room.

This general rule of thumb and the sub crawl worked for me. And then of course, REW, mini DSP and Audyssey XT32 smile.gif
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post #14 of 16 Old 04-11-2014, 11:08 AM - Thread Starter
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Well, its looking more and more like physical constraints mean the woofer itself needs to be at 1/3 and 2/3 the room width.

Is this just suicide? What am I looking for in the room measurements to tell?

If it's craziness, then my option is to rebuild the screen wall. NOT ideal, but I'll do it if that's what it takes.

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post #15 of 16 Old 04-13-2014, 09:03 AM - Thread Starter
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I decided to do some modeling, to get an idea of what I am looking at, since my second sub has not arrived.

REW now has a great modeling feature that lets you define room size, woofer location, listening location, etc.

I'm trying to optimize for three possible seating locations, all in one row. Sometimes it's two people, sometimes it's one -- and when it's one person, it's in the middle of where the two people seat.

Yes there is a whole second row of guest seating, and I'm not too worried about that.

Here we have the classic "put them in the front corners" approach. Note that the subs are actually about 22" deep, and I just let the software's default handling of them as 1' cubes take over for this first run.



Ugly. Horribly ugly? No, but surely we can do better. It doesn't even have good seat to seat consistency, so correcting is tough.

The advice most people provide, as a rule of thumb, is that 1/4 and 3/4 front wall placement is often a great place to start.



And it's not too bad, as you can see, but also not too great.

A variation on that is, to use 1/4 of the front wall, and 3/4 of the back wall -- though that is an effort to get row-to-row variation minimized, which is not my goal.




So without further ado, let's take a look at what the modeling software said would work best -- both in terms of seat to seat variation for the main listening row AND in terms of not having crazy dips (nulls) that are of course much harder to correct well than a few consistent peaks:

Just like the Harman research, it's mid wall placement, front and rear.



For the front wall, this is not too difficult.

For the rear wall, right now there is seating in that location. Looks like I may need to turn the center seat into a large, rumbling end table!

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post #16 of 16 Old 04-24-2014, 10:26 AM - Thread Starter
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Haven't figured out the seating thing. Will start with them at 1/3 and 2/3 on the front wall and measure that.

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