2 15" on a baffle against ceiling corner (open ends) - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 5 Old 11-05-07, 01:10 PM Thread Starter
Join Date: Dec 2006
Location: Brooklyn, NY
Posts: 15
Cool 2 15" on a baffle against ceiling corner (open ends)

Hello guys,

I built a nice 12" 8cu.ft MLTL sub 4 years ago that served well both for movies and music. Now i built new OB mains with 15" drivers and they go down to 30Hz and I'm amazed by OB bass and now the TL sub sounds boomy. Plus for movies it's very weak (I now realize that) So i'm on a quest to build a new pair of subs with couple 15-18" drivers. I need something that goes down to 10Hz (mainly for movies, since i'm happy with just mains for music) with authority but does not 'boom' in the room. I don't like ported or radiator ideas, so it's either sealed or OB.
My apartment room is 191sq.ft. , 1750 cu.ft. (not large at all) I listen along the long wall (so the PJ screen can fit). I also have no space on the floor and will be removing my current 'refrigerator' sub. The only available space i have a above the screen along the whole length of the front wall (16.5 ft).

I wanted to know if it's possible to put couple of 15-18" subwoofers on a baffle and mount that baffle at 45 degrees angle between front wall and ceiling and have open ends. It will be like OB/TL mix, but the problem is I don't know how it will behave and how to model that. Since i have 16 ft of space i can make the TL pretty long and have openings facing the listener.

Tell me if this idea is totally crazy (since I haven't seen anyone do that)?
I was also thinking of putting 4 drivers on OB and setting them in the front like Bob in St.Louis did, but they will be at most 1ft from the back wall and will probably not go down that low.

If i want the lowest extension MUST i go with sealed then?

I was thinking of couple RL-p15, RL-p18, CSS SDX15 or Tempest-X 15". If I'm going with the sealed than i'll need the smallest Vas driver. If OB/TL then largest Vas.

Any comments on any of the issues.

Last edited by otmopo3ok; 11-05-07 at 06:57 PM.
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post #2 of 5 Old 11-05-07, 02:59 PM
Join Date: Nov 2006
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Re: 2 15" on a baffle against ceiling corner (open ends)

I can't imagine an apartment where one of any of those drivers wouldn't get you evicted in a heart beat. I just doubt 2 of them are necessary unless you're planning ahead.

I have to ask what room treatment and especially bass traps are you using? Boomy bass can easily be caused by room position alone.

I'm the first one to want overkill. In our 12x20 living room that has an 8' wide opening to the dining room which has an opening to the kitchen a single RL-P 15 is really plenty. We were concerned the neighbors would complain due to the volume that makes it outside.

If it's mainly for movies you could use a ported design to get down that low just fine. For movies imo a ported is fine. In my music system I use a sealed design with a PE RS driver. The bass using these Sound Splinter drivers is **** good. Ive built two, one with 2 drivers for a friend and one with one driver for me.

If I were to build one sub now I'd use the 18".
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post #3 of 5 Old 11-05-07, 05:20 PM
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Re: 2 15" on a baffle against ceiling corner (open ends)


That's an interestig plan you have with the subs mounted in the corners on a 45 degree angle. I'm personally not familar with OB subs, but hopefully someone who knows will chime in with some ideas.
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post #4 of 5 Old 11-05-07, 05:32 PM Thread Starter
Join Date: Dec 2006
Location: Brooklyn, NY
Posts: 15
Re: 2 15" on a baffle against ceiling corner (open ends)

Well, first of all I'm also for overkill and based on my experience with my mains (they both have 15" woofers in OB) and single 12" TL sub I thought 2 drivers would be better.
Secondly since this design (if it works at all ) is kind of open (OB?!?TL!?!) so the drivers will be easier to bottom out and I am going to EQ them flat to at least 15Hz so i will be cutting a lot of SPL in favor of extension and effortlessness.
Thirdly, I have major issues with current sub because it's ONE and in the corner, so I thought 2 subs will improve my in room response some more.
Plus if I move soon then I won't have to build another sub.

Do you think this works? and why nobody uses it?
Another question i had is can you have Infinite Baffle whose back wave opens back into the room eventually (this is in a sense what this is). The are obviously would be cancellations of these two waves somewhere but the question is where?
And if i make it long enough then it will behave like a transmission line if i close one end. Could be really cool easy sounding sub.

PS: Forgot to answer about room treatment. I have no bass traps but i have a huge thick carpet (rug) covering the whole back wall. This improves the sound dramatically since it absorbs all the high frequencies behind me. That is why OB bass amazes me it creates virtually no room modes in my room. I've never heard such clear reproduction of drum kit before.
And as much as i understand that ported is fine for movies (I have ported MLTL now and don't like it after 4 years of growing up - musically) , once I've been spoiled by OB it's really painful to listen to any boxed arrangement. Sealed is bearable.

Last edited by otmopo3ok; 11-05-07 at 05:41 PM.
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post #5 of 5 Old 11-06-07, 05:38 PM Thread Starter
Join Date: Dec 2006
Location: Brooklyn, NY
Posts: 15
Re: 2 15" on a baffle against ceiling corner (open ends)

Thomas from infinite baffle forum corrected me that OB and TL are oxymorons and he is absolutely correct. I only called it TL because it's rather long and if i close one end there will be a standing wave of rather low freq. there.
I imagine it to function somewhere close to Ripoles where driver is sitting in a tight space and is not completely free OB but has some air resistance (due to smaller volume than optimal). Since the air behind the drive gets compressed somewhat due to small volume but the air still escapes it lowers the Fb of the whole system, just like Ripoles do.
The other thing that I think happens in my idea is once the back wave enters the room from both sides it starts canceling with the front wave. So i imagine it would have a 90 degree radiation pattern.

.......... /.......\

Doesn't look like 90* but u get the idea. If you are sitting in the front (and i do) you would get the benefit of whole front wave but closer to the sides and corners they would cancel out. It's JUST my speculation, i really have no idea.

By varying the space behind woofers I can lower Fb.

Also I'm not sure if I should select high Vas drivers (dipole oriented) since it's kind of OB and to get the benefit of compressing them with smaller space.

OR should I get low Vas driver (box oriented) since there is little space behind the woofers. But then to make them 'uncomfortable' (to lower Fb) I have to make the space behind them even smaller.

What do you think? Am i on the right path with these ideas?

W,H,U frames require space around them and do not go as low as Ripoles (which are an evolution of W frame in a sense (evolution towards lower Fb i mean)) . But think about it, all W,H,U baffle does is separate front wave from the back wave a certain distance, same as in my idea. Ripoles compress back wave somewhat to achieve lower Fb, so does decreasing the space behind woofers in my idea will.

PS: I'm using term Fb incorrectly here since it relates to boxed design but i think everybody understands that i mean the -3db point of the whole system.
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2 15 , baffle , ceiling , corner , ends , open

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