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Post by rockrover on Mar 25, 2011 18:18:38 GMT -7
Hi guys! Okay, so I've got a specific rear enclosure I'd like to investigate using.
Essentially what I have is a HT that is 14'x14' (1700cf) sealed. Adjacent to the room is a master bath with a walk-in closet. The walk in closet is 202cf. The rest of the master bath is aprox 850cf.
The closet is were I would like to mount the baffle. It is 6.25' x 3.6'x9 which is only 5670 liters .
The baffle would house 4 each opposed 18" Fi's. These drivers require 15240 liters for a 10x Vas.
Now the drivers would be mounted on the short 3.6' wall, and directly adjacent to the proposed mounted baffle is the closet door that opens into the bathroom. The rear of the drivers would only be a few inches (5") from the opening.
Before I invest in the drivers my question is will the closet negate my IB, or does the close proximity of the wide closet door (3'6" x 7') next to the rear of the baffle keep my 10x Vas chill?
I'm hoping your collective knowledge and wisdom can let me know that the closet won't act as an enclosure and the adjacent bathroom will make up my missing liters, and I'm good to go!
The HT room is getting new flooring, so I'll post pics tomorrow if you guys think it will help with your opinions, but I think you should get the general idea.
TTFN! and TIA!
--Doug
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Post by ThomasW on Mar 25, 2011 20:51:41 GMT -7
Hi,
Yes pictures would handy.
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Post by rockrover on Mar 25, 2011 21:23:32 GMT -7
I'll get the pics goin' tomorrow.
Essentially my question is will a IB in a closet, with a large opening to another room cause too much rear-wave, thus canceling the infinite Q?
Thanks so much for the shout!
--D
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Post by rockrover on Mar 27, 2011 16:29:55 GMT -7
Okay gang...Here is the birds eye view of the existing layout. Again I think if the closet door is open, and the back of the closet is filled with R36 batts I should be able to tame the rear-wave no? The closet is 140cf and the main room is 1700.  The idea here is bone crushing lows. I want to wish I had lower headroom!  I might consider 6 each IB385 15"'s. Save money and keep my Vas (with the closet door closed) to 3.7x...Open  The real deal...The manifold will (hopefully) pop out where the wood sample is leaning against the wall:  The closet real view towards the back of the closet were the manifold will (hopefully) be housed:  Thanks in advance! |
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Post by rockrover on Mar 27, 2011 16:35:41 GMT -7
pl.an/mlm3gnThis view will give you dimensions of the room/closet/bath. If it doesn't work then the room is 13x13 and the closet is 3.8 x 6'5" x 9...Opening into a 10 x10 bath. --D
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Post by ThomasW on Mar 27, 2011 20:56:29 GMT -7
Again I think if the closet door is open, and the back of the closet is filled with R36 batts I should be able to tame the rear-wave no? Tame the rearwave? Not a chance the bathroom will roar with the same sound as the listening room. Have you tested the location using an existing sub? If not that must be done. 4-18"s is a waste of money for a room that small. 2-18"s will be more than enough. |
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Post by rockrover on Mar 27, 2011 21:51:17 GMT -7
Thomas,
When you say test the location with an existing sub do you mean putting my existing ported IXL in the approximate location in the main room and check for nulls and/or gain?
I really don't care about the bathroom roaring with the same spl...I *think* what I care more about is back-wave cancellation of in-room response. Right?
Again, please forgive my noobness. I want to do this right, and if that means ditching the project then so be it. If I can at least taste the IB sonic goodness through this configuration then it's worth some drywall IMO.
--D
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Post by chrisbee on Mar 27, 2011 22:47:09 GMT -7
Thomas is referring to the standard practice of testing an IB location with a normal sub. Unless you do this you haven't clue how it will sound or perform. An IB is no different from other subwoofers in this respect. A subwoofer drives the room and all its LF modes. In some positions it will work well. In others it will boom. Some people are more sensitive to offset bass sources than others. Testing in that position with your normal sub will prove whether you can live with any sub in the intended IB position. Regarding the closet and bathroom: With an IB, you aren't trying to cancel anything. Yo are trying to allow the rear wave free and unhindered expansion. The drivers need to think they are in such a vast space that they can feel no compression effects. Nor any near reflections which might cause unwanted or delayed sound to come back through the cones. It is not so much the size of the closet but the nearness of walls which might cause reflections. With the door wide open you are probably safe from compression effects. Lining the closet will kill local reflections and help to absorb sound levels in the bathroom overall. (with the door open) In the bathroom you will hear all of the bass that you can hear in the AV room. In an ideal IB, bass levels will be equal on both sides of the diver cones at the same distance from the cones. I find levels are about equal throughout the rear enclosure. Distance has no effect. This is probably a compression effect. Two Fi 18s will work in your favour because they have relatively low Total Vas. You have limited rear volume even including the entire bathroom. You can't easily line a bathroom with insulation to fool the drivers into thinking that you have a much bigger space available. Two IB3118"s have the same displacement as four of their 15"s. So you should be safe unless you deliberately try to kill the drivers. If you match the IB output level to your main speakers then the speakers will be the limiting loudness factor and not the IB. Even running the IB slightly hot and with a house curve should not affect this by much. Your relatively small AV room should provide some LF gain without you needing to do anything about adding house curves. First things first: Put your present sub where you want to put your IB opening and have a good long listen to music and films. If it doesn't work right there and you still go ahead then only you have to put up with it. Not us.  |
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Post by ThomasW on Mar 28, 2011 6:31:04 GMT -7
Thomas, When you say test the location with an existing sub do you mean putting my existing ported IXL in the approximate location in the main room and check for nulls and/or gain? Yes this is very important and particularity so when the listening room is so small that the listening position is totally a fixed location. You don't want to see a huge null there. Unfortunately having a square room there's a high probability of a significant null, and I see no real estate available to place large bass traps Front/rear wave cancellation is guaranteed as long as the bathroom door is shut. You will probably want to replace the existing door with a solid core unit to decrease how much the door rattles. You'll also need to treat the french doors for rattles with neoprene foam weather-stripping since the IB will easily pressurize the room |
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Post by rockrover on Mar 28, 2011 7:21:28 GMT -7
Awesome response guys! Thank you!
Once the floors are in I'll move my LLT 18 IXL into the position and see what's up. I know there is a massive null in the opposite corner of the room from the corner loaded LLT now. My fear is that with the IB, I'm essentially switching corners, thus potentially putting the null right in my listening position. Then again working with phase might work...I guess I just need to 'do it' and find out eh?
Now the IB3818 sounds like a good option no? I could put 2 of those, keep my Vas ratio w/in 4x and save a little doe-ray-me? Hmmmmm. Maybe I don't need to worry about when Fi is gonna' be back on line.
Again thank you boys for taking the time to help out another noob in search of sonic bliss! When the drivers are available again, and assuming the location is workable, I'll make sure I post up pics of the build, REW sweeps etc.
-D
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Post by rockrover on Mar 29, 2011 21:36:16 GMT -7
So what do you think about the MWF drivers? The price is almost too good to pass up!  At $80/driver there is very little risk and I can go 4x drivers. The vas has my eyes poppin' a little. What say you? --D |
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Post by ThomasW on Mar 29, 2011 21:59:50 GMT -7
I might buy some were I in the market for OB woofers. They're of no interest for an IB sub
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Post by rockrover on Mar 30, 2011 8:50:13 GMT -7
Really!!? Dang it! I knew it was going to be too good to be true!
Thomas, your experience and expertise is greatly appreciated. Guess I'll wait for the Fi's. Mark mentioned the other day he's about 4-6 weeks out...Double that and I won't be too disappointed.
Gotta' do the bass test in the proposed area anyway...Can't do that until the floors are in and that's 2 weeks away. Timing might work out.
--D
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