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DPM
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Subwoofer placment question.

As I'm about to move from an apartment into a house, this will free me to set up my sub again ( a BIG no, no in apartments). Here's my question. What are the advantages/disadvantages of placing the sub directly behind the listening chair (which will be at least six feet from the rear wall and about fifteen feet from the front wall).

The sub in question is a Velodyn DD 12, and the listening area is 30x19 with a cathedral ceiling. This listening space is open to the kitchen/dining area. In other words, we're talking about a lot of room.

My trane of thought is this: with the subwoofer situated so close to the listening seat, wouldn't many of the room mode problems be lessened to some degree?

Monty
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Re: Subwoofer placment question.

I've read many times that low frequencies are not easy to localize and that sub placement is not critical. I've not found that to be the case with my limited experience using subs. However, if you aren't able to localize the low frequencies with the placement behind your listening position then the only downside is the lengthy cable run which probably won't become an issue.

I would at least try the sub between the front speakers for a little while before placing it behind your listening position, if for no other reason than to satisfy yourself that there isn't any loss in coherency of the soundfield.

RGibran
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Re: Subwoofer placment question.

That's an awesome sub, but with those room dimensions, high ceiling, and open to the kitchen, it's going to need all the help it can get, like corner loading or preferably, a second sub.

Advantage of having it behind the listening seat? The seat will vibrate, if you like that sort of thing.

RG

mrlowry
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Re: Subwoofer placment question.

The first paragraph is a repost that I wrote for another thread. The second is some thoughts to your specific application

How much have you played around with placement? Where is your crossover set? I find that many people set them far too high. I believe that when a sub is properly set up you should never know that it's on, until you turn it off. Where a subwoofer is placed can have a massive effect on it's sound. My favorite placement trick is to hook up the woofer and put it in the sweet spot where you listen. If you have to use a cheap cable to do this go ahead, it's only temporary. Next, put a piece of music on with a bass solo, I find that upright bass in jazz works well. A CD player with an AB repeat is handy for this. Now walk around the room until you find a spot where it sounds the smoothest and most integrated with the music. This is where the sub should go. This is much less painful and quicker than moving the sub all over the room. After you have the proper placement then is the time to start tweaking with feet, etc.

The problem that I see with placing the sub so far away from the main speakers is that the main speakers and the sub will be pressurizing the air in the room from completely different places and you will most likely run into phase issues where you may have tons of bass at some frequencies and none at all at others. The Velodyne that you mention can adjust for room peaks but not phase problems to my knowledge. Also, don't be tempted into trying to boost nulls in the sub response. They are there because of problems in the room's acoustics if you turn the sub up at that frequency the problem will push back even harder. I tried this once and I believe that I ended up having to boost a sub something like 18 db to correct a 3 db dip. This massively overtaxed the amp and sub and was audible.

Jan Vigne
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Re: Subwoofer placment question.

Phase problems are the reason you don't want to place the sub more than a few inches away from the main satellites. Even if you can adjust the phase of the sub by 180 degrees in relation to the main speakers, it will only be correct over a small portion of the frequencies the two cover for any one setting. Either use the placement method described above or, better yet, put "subwoofer placement" into a search engine and read a few different methods for proper location of the subwoofer. Personally, I would suggest getting the sub off the floor, if at all possible. If you have anything to support the sub at about mid-height in the room, I think you get much cleaner response through the low frequencies. Don't forget to spike the sub or somehow afix it to the surface of the floor or shelf to tighten up the bass response.

DPM
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Re: Subwoofer placment question.

Thanks for all of your responses. Here's some additional info. I'll probably be setting the crossover frequency at 60 Hz, and the Velodyne sub does have a variable phase setting.

My front left/right and surround left/right speakers are large Hales towers (Trans Eight's and Revelation Three's) with strong bass response to below 30 Hz. Because of this, the subwoofer will probably be used only for movie soundtracks. With SACD and DVD Audio surround, I'm skipping the sub. Those four towers should be able to generate enough low frequencies for music.

However, during movie playback, I now can see that the size of the room may be a bit much for one 12 inch sub. I'll play it by ear for the first few months after I move in. I don't play movies real loud, so one sub might be enough.

After further consideration I think I will keep the sub up front with the towers. Later, if I find that one sub isn't enough, then I'll add a second on the back wall.

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