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Post by keager on Apr 2, 2012 6:53:44 GMT -7
I'm completely new to IB and was pointed here by the AVS forum. I have two RE Audio xxx 18 drivers (54mm xmax). I'm thinking of using a closet adjacent to my living room as a "box". I'm not really too concerned about below 10hz. Could I essentially make that closet a ported "box" tuned to 10 hz? I'm reading all I can, and it's a little overwhelming. Any advice would be appreciated. Thanks!
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Post by chrisbee on Apr 2, 2012 8:26:52 GMT -7
I'm completely new to IB and was pointed here by the AVS forum. I have two RE Audio xxx 18 drivers (54mm xmax). I'm thinking of using a closet adjacent to my living room as a "box". I'm not really too concerned about below 10hz. Could I essentially make that closet a ported "box" tuned to 10 hz? I'm reading all I can, and it's a little overwhelming. Any advice would be appreciated. Thanks! We don't usually discuss ported boxes here. Except on one rare occasion in the following thread. But only because we couldn't find any way to stop him once he got started. ;D ibsubwoofers.proboards.com/index.cgi?board=projects&action=display&thread=1734Ideally you should read the encyclopaedic IB FAQs. These are in the blue text links at the top of the page. Once you have absorbed all the details you can start a thread in the projects section. Where we will encourage you to a satisfactory completion of an IB. Our beloved Cult leader  (may his name be showered in praises) does not like porting. Since it undoes most of the advantages of IB. ie. Low power requirements and a smooth, well extended response. Without artificial augmentation, colouration or phase issues. |
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Post by keager on Apr 2, 2012 9:45:08 GMT -7
Thankyou very much
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Post by chrisbee on Apr 2, 2012 10:23:48 GMT -7
Don't think we are sending you away. We aren't that bad. Well, I'm not, anyway.  Since you already have two nice, big 18" drivers you are well on your way. If you just want to check whether an IB is in your stars: Find the Vas of your drivers from the manufacturer's T/S parameters. Now multiply Vas by how many drivers you intend to use. This figure is your Total Vas and can be thought of as a volume in litres. Now you need to find the volume of your IB enclosure. (your closet or cupboard in your case) Height x breadth x width for a rectangular box. Convert your enclosure volume in cu.ft. to litres with an online conversion website. Now divide the volume of your potential enclosure by the Total Vas of your drivers. If the result lies above 5 x Total Vas you are in business.  It's mostly all downhill from there. You need to tell us the size of your room. The distance from your seat to the intended subwoofer position. Films or music or both? Whether you like it loud? Some idea of the wall structure of the closet would be helpful. Stud spacing etc. We do not have the power to stop you porting your closet. You may like what you hear. Our opinion is that the sound will be made inferior by converting an IB to a ported box. All that air rushing in and out will probably be audible for a start. A couple of 18"s will move so much air it would be very hard to avoid lots of unwanted noise. Even if you can keep port velocity down you would need to make smooth trumpet flares at least a couple of feet across. This is totally unmarked territory. |
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Post by ThomasW on Apr 2, 2012 10:23:50 GMT -7
I'm completely new to IB and was pointed here by the AVS forum. I have two RE Audio xxx 18 drivers (54mm xmax). I'm thinking of using a closet adjacent to my living room as a "box". I'm not really too concerned about below 10hz. Could I essentially make that closet a ported "box" tuned to 10 hz? I'm reading all I can, and it's a little overwhelming. Any advice would be appreciated. Thanks! You want to port at a infrasonic frequency? Why bother? All 10Hz output does is shake the room (since it's inaudible) and you can do that with higher frequencies and not worry about damaging the drivers. The size of a port for 10Hz tuning is huge and almost always it results in port resonances that limit crossover points to 60Hz Hz or lower to avoid operating the sub near the port resonance. Build the closet as a sealed box (aka IB) . use a manifold to mount the drivers..... |
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Post by keager on Apr 2, 2012 13:51:37 GMT -7
Ok. I will weigh my options and start a. Build thread when i have more info. Theoretically, could one build a ported closet like that and then plug the port to obtain sealed results?
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Post by ThomasW on Apr 2, 2012 16:53:18 GMT -7
If you build it ported the closet must be structurally as stiff as a small portable sub otherwise the port won't function correctly.
If you build it as an IB, standard studwall construction techniques will be adequate.
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Post by keager on Apr 2, 2012 18:01:24 GMT -7
After some research, im leaning to IB. If I like it with two of the drivers, I will sell my other sub and add two more. I'm going to do some measuring so I can get more info from you very generous gentlemen. The more I read about IB, the more I want one. I will have more questions soon! Thanks
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Post by keager on Apr 3, 2012 4:53:30 GMT -7
If I were to use 4 of these drivers, the vas total is 896.8. My Estimation on enllosure size is 225 cu ft, or 6371.290 liters. Dividing the vas by the liters comes up with 7.11? That is supoosed to be 5 times the total vas? Forgive my ignorance, I need guidance  |
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Post by ThomasW on Apr 3, 2012 6:48:59 GMT -7
It's good to have at least 4 times the summed VAS, so 7+ is just fine.
How big is this room? Do you really need the swept volume of 4 drivers?
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Post by keager on Apr 3, 2012 7:09:53 GMT -7
I guess i don't "know" I need four. It is in my living room, open hallways and stairs to the entire house. About 2100 sq ft, 10ft ceilings downstairs. I would like to have ample headroom, because I listen very loud, and if I went IB, I would have another sub to sell, freeing up funds to do so. The area I'm thinking for the manifold looks like there is only about 12 to 14 inches between 2x4 studs, and I could only go about 40 inches high. There is enough room in closet to go over 24 inches deep. Thanks for taking the time to help.
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Post by ThomasW on Apr 3, 2012 7:18:54 GMT -7
13.5" X 40 opening would be large enough for 4 drivers.
I'd build a manifold large enough to house 4 drivers but start off using 2. Block off the unused section of the manifold. If after all is said and done you think you need/want the output from additional drivers all you need to do is open the section of the manifold and bolt in the drivers.
Have you tested the proposed location for the IB using a portable sub? It's important to test location in advance to make sure you don't have problems with any nasty room nulls.
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Post by keager on Apr 3, 2012 7:42:25 GMT -7
Where do I find instructions for testing location? I'm sure I overlooked it. Lots-o-info. Thanks!
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Post by severianb on Apr 3, 2012 8:10:47 GMT -7
Check out my build thread here, I did quite a bit of testing. I used dual subwoofers, but it's pretty much the same as using a single sub. REW is free, and SPL meters are cheap. The only issue is the learning curve, but it's worth it for the peace of mind, IMHO.
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Post by keager on Apr 3, 2012 8:49:08 GMT -7
I will read that. Thanks. I do have rew, mic, spl meter.
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Post by keager on Apr 4, 2012 13:48:48 GMT -7
So far, i have found that the manifold will be about 10ft away on the left hand side. About 10 oclock, pointed directly to the right. The wall the manifold would be pointed at is about 15 ft away. Behind the LP is a kitchen and dining room, all open. The manifold opening is about 12 inches by39 inches. Would be going with four 18 inch drivers. Will be measuring this weekend. Open to suggestions. Oh, probably 50/50 music/movies, like really loud and deep bas.
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Post by keager on Apr 4, 2012 16:21:14 GMT -7
When i test for the placement of my new manifold, I' m going to place my existing 18 inch sub with dual passive raditors in the lustening position. Which direction should the drive be facing? Also, due to the size of the box, its not feasable to bring the height up to the Lp height. Does that make a big difference? Thanks!
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Post by severianb on Apr 4, 2012 17:19:47 GMT -7
That must be one big sub! I'd say get it as close as you can. I noticed changes in response were gradual when I was measuring, so you should be able to get a decent idea.
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Post by keager on Apr 4, 2012 18:49:17 GMT -7
Yes it is a big sub-about 250 lbs. Will be glad to hear my subs and not see them  |
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Post by keager on Apr 5, 2012 18:58:02 GMT -7
It looks like I may have clearance issues due to thisd being under stairs. The slope of the ceiling of the closet may interfere with the motor of the drivers. How bad of a loss of sound quality or mechanical cancelation would there be if the drivers were angled or faceted? I would have for drivers and two on each side. I know you can't say for sure, but don't know if it would be a deal breaker.
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