CECAA850 Posted January 9, 2014 Share Posted January 9, 2014 From the Cult. I see all the 4-15" driver IB's in the gallery. I have a single ported 15" sub and it shakes the room. Are you going to recommend 4-15"s for my IB? These are all basically the same question. People need to understand that every IB is a custom design, and a custom installation. Also people have different performance expectations, and no two 3000 cu ft rooms are the identical. That's why there are no formulas for calculating the number of drivers needed for a given volume of space. As explained on the main FAQ page, the output level of any box sub is limited by the thermal heating of the voice coil. IB subs are limited by the excursion limits of the suspension. As a result a single 15" in a ported or seal box can play quite a bit louder (be driven harder) than a single 15" mounted in an IB. So depending on the room, the listener, and other variables, it can take 2 to 4 times more drivers in an IB, to equal the output of a box sub. Also I will always error on the side of recommending too many drivers (= too much displacement). The reason for this is that it basically guarantees no one will be disappointed after they've gone to all the time and trouble to create their IB. Finally having a high amount of displacement, guarantees the workload on the drivers is low, and as a result so is the distortion. But I can't afford 4 drivers, I can only afford buy 2. Because of the relative uncertainly regarding how many drivers are needed/wanted, I recommend designing and building the manifold so it's pre-made to accept additional drivers. This means making the cutouts for the additional drivers, then closing off those holes before installing the manifold. This is extra work up front. But it's much easier to do this in your shop prior to installing the manifold, than it is to do in the attic, basement, or crawl space, after the fact. Mike Keith followed this advice with the manifold he built for his 18" Avalanche drivers. He started with a pair of Ave 18"s, and is now quickly able to add additional drivers should the need arise. Since the pictures are fairly large I put them on THIS webpage. Quote Link to comment Share on other sites More sharing options...
BE36 Posted January 9, 2014 Share Posted January 9, 2014 Cost is getting close but I'm not following the logic. I would understand if one DD15 was equal to the (4) 18's he is considering. My guess is 1-2 of those 18's would best the velodyne No logic trying to learn more, putting two IB in different locations in the room would probably be better than one dd15 and better than two IB in same location? 1 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 9, 2014 Share Posted January 9, 2014 Cost is getting close but I'm not following the logic. I would understand if one DD15 was equal to the (4) 18's he is considering. My guess is 1-2 of those 18's would best the velodyne No logic trying to learn more, putting two IB in different locations in the room would probably be better than one dd15 and better than two IB in same location? Front and rear, centered in the walls would work yes. He's trying to utilize the existing subwoofer opening that the room already has however. Quote Link to comment Share on other sites More sharing options...
BE36 Posted January 9, 2014 Share Posted January 9, 2014 For reference, I sit 14' away from the drivers. The most I thought my house could stand was 110dB @ 10Hz. The measurements were taken at the seated position using the correction table for the Radio Shack meters. Cutting that in half would be around 100 dB@ 10 Hz, roughly 110 dB @ 20 Hz. I'm sure someone could figure out just how loud that is at the drivers but it was crazy in the house. Any doors that were shut were shaking like someone was trying to get in. The windows in the back of the house were bowing visibly, the ceiling fans in the adjacent room were actually turning slowly and that's with the drivers I have. Yours will displace about a liter more (for the set) and have about 3mm more Xmax. For reference, I sit 14' away from the drivers. The most I thought my house could stand was 110dB @ 10Hz. The measurements were taken at the seated position using the correction table for the Radio Shack meters. Cutting that in half would be around 100 dB@ 10 Hz, roughly 110 dB @ 20 Hz. I'm sure someone could figure out just how loud that is at the drivers but it was crazy in the house. Any doors that were shut were shaking like someone was trying to get in. The windows in the back of the house were bowing visibly, the ceiling fans in the adjacent room were actually turning slowly and that's with the drivers I have. Yours will displace about a liter more (for the set) and have about 3mm more Xmax. Iam too old for this thread. . . 1 Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 (edited) CECAA850, Thanks for all the info and help on this one. I spent a lot of time looking through "the cult" site you suggested. You have convinced me to move a small wall to make room for 4 subs. Probably will be installing 2 to start with for cost. Here is what I am thinking I will do: Manifold opening should be 19" wide x 24" tall. I think that is as big as I can go. I can go a couple inches wider to meet driver size requirements. The Manifold size and shape would flare out to match the size of the rack next to it for aesthetics. I could put a grill on it....but why? Obviously not a structural drawing... Edited August 4, 2014 by WakeJunkie Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 Looks great, can't wait to see build pics as you have great skill at construction. One other bit of advice if you will. If you build with 2 drivers now and plan for 2 more down the road, place the 2 drivers on top and bottom, closest to the room. Build a temporary "wall" to close off the section of the manifold that will not be utilized. Remove it (naturally) when you get your second set of drivers. I've never seen a manifold with a flair like that before. Is it necessary due to having to move the manifold away from the room? If not, pull the manifold forward closer to the room and eliminate it. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 I can go a couple inches wider to meet driver size requirements. Bear in mind that your manifold walls will be 1 1/2" thick. Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 (edited) I can definitely see how an empty box end could be an issue. I am thinking about finishing it out inside like a piece of furniture. It would match the surrounding walls. Not a typical IB manifold. If I build a temp wall something like this I should be able to do it without messing up the finish for when I go with 4. Use the driver mounting bolts to secure the temp wall. Temp part is shown in Red for clarity. The side wall in the original pic has no thickness so it is definitely a bit off. I don't have to flare it. That was for looks. Box would be about 6" recessed from the face of the front wall. Looks more like a foot in the pic. I thought making the openings in the wall the same size would look better than a different size hole than the rack. Do you think a few inches will make a difference? Edited August 4, 2014 by WakeJunkie Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 I can go a couple inches wider to meet driver size requirements. Bear in mind that your manifold walls will be 1 1/2" thick. I was measuring for 2" manifold walls so I should be good. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 Do you think a few inches will make a difference? In which plane? If you're talking about recess, I'd get the drivers as close to the opening as possible and the box only as deep as necessary to get the drivers to fit. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 The petition concept is perfect. Just be sure it's sealed. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 Another thought. After adding the 3'rd and 4'th drivers, I'd add a horizontal piece of all thread rod centered in the middle of the box to help prevent wall flex. If you're concerned with aesthetics with no grill, you could add a cover made out of a length of PVC pipe painted black. Dimmable LED's in the back of the chamber would be a cool effect also Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 Do you think a few inches will make a difference? In which plane? If you're talking about recess, I'd get the drivers as close to the opening as possible and the box only as deep as necessary to get the drivers to fit. Recess is correct. That is why I was doing the flair right up against the driver. If the box has a sharp flare out I didn't think it would cause a problem with sound bouncing back into the box. Maybe I am missing something. Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 Another thought. After adding the 3'rd and 4'th drivers, I'd add a horizontal piece of all thread rod centered in the middle of the box to help prevent wall flex. If you're concerned with aesthetics with no grill, you could add a cover made out of a length of PVC pipe painted black. Dimmable LED's in the back of the chamber would be a cool effect also LED's would be very cool. Wall flex was a concern for me as well. I was planning for a 2" wall. I can reinforce from the outside to make the sidewall rigid. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 If the box has a sharp flare out I didn't think it would cause a problem with sound bouncing back into the box. Maybe I am missing something. I wasn't concerned about the sound bouncing back into the box. I was wondering if it would act as a horn and how that would affect things. It may have no effect whatsoever, I have no idea. Quote Link to comment Share on other sites More sharing options...
The Dude Posted January 10, 2014 Share Posted January 10, 2014 Not meaning to hi jack to much on the topic, but how did you come about your components in sketchup. Quote Link to comment Share on other sites More sharing options...
The Dude Posted January 10, 2014 Share Posted January 10, 2014 If the box has a sharp flare out I didn't think it would cause a problem with sound bouncing back into the box. Maybe I am missing something. I wasn't concerned about the sound bouncing back into the box. I was wondering if it would act as a horn and how that would affect things. It may have no effect whatsoever, I have no idea. I was thinking the same thing, this could be good or bad. Quote Link to comment Share on other sites More sharing options...
WakeJunkie Posted January 10, 2014 Author Share Posted January 10, 2014 Not meaning to hi jack to much on the topic, but how did you come about your components in sketchup. I just downloaded components from within sketchup's online library. If the box has a sharp flare out I didn't think it would cause a problem with sound bouncing back into the box. Maybe I am missing something. I wasn't concerned about the sound bouncing back into the box. I was wondering if it would act as a horn and how that would affect things. It may have no effect whatsoever, I have no idea. I was thinking the same thing, this could be good or bad. It we are talking about a couple inches of flare over about a ft. I may just recess the 48"x19" area 2" and square it off so it lines up with the rack. That would leave the manifold edge recessed 2" into the wall instead of the 4-6 originally planned. Looking a bit like a horn was intentional, playing with ideas to make it look nice. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 10, 2014 Share Posted January 10, 2014 It we are talking about a couple inches of flare over about a ft. I may just recess the 48"x19" area 2" and square it off so it lines up with the rack. That would leave the manifold edge recessed 2" into the wall instead of the 4-6 originally planned. I like that better. Quote Link to comment Share on other sites More sharing options...
The Dude Posted January 10, 2014 Share Posted January 10, 2014 One more question in case I missed it. What did you use for the wood paneling on the walls? Quote Link to comment Share on other sites More sharing options...
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