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Post by rexxxlo on Oct 10, 2010 8:31:53 GMT -7
i have 4 18' woofers i am planning on doing an ob with
im having a problem
LAYOUT
whats the preferred method? ive seen a bunch of pics and setups everyone has a layout that fits the constraints of the room or aesthetics they have to deal with, but i seem to be missing why any particular design was chosen.does it really matter?
i have a large wall with a 3 thousand cubic foot room next to it for my ob to work in
the wall in question will be on one side and its completely free i can do anything i want to it and any option is reasonable for me,the adjoining room is roughly 20 % bigger in size and primarily empty....well my summer car is parked there its my garage
is there one layout that is better than the other i see 3 generic layouts and a couple variances
1 a tunnel with all 4 woofers mounted to it this would need an 18" square cut out in the wall and 18' protrusion into the wall
2 (2) separate tunnels with 2 woofers mounted front to back on the opposite wall in a cutout 14.5x 18"
3 (4) separate tunnels one for each woofer so i dont have to cut any studs just a 14.5' x 18" hole for each woofer and put a woofer each stud cavity or every other cavity to distribute the bass and help smooth out response
4 cut out a section of the wall horizontally the length of 4 woofers, build a header and make a baffle squeeze the 4 woofers horizontally in a line then need a grill 18"x72"
5 cut one stud cavity the height of 4 woofers make a vertical array 6'tall
6 a variation of #5 cut a cavity 3' tall and put the woofers front to back on opposite baffles
is one layout a better layout that another?
why?
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Post by ThomasW on Oct 10, 2010 11:14:47 GMT -7
Hi, You're talking about an IB not an OB (dipole) design Yes the designs are individual and vary primarily due to the physical limitations inherent in any given installation (ie not everyone can do a manifold centered on each wall on a room) The differences between using manifolds and line arrays are covered in the FAQ and the generic Design/Build/Install pages. When possible I steer people toward manifolds just to decrease the amount of vibration. Tunnel? Not sure what you mean by 'tunnel'. Do you mean manifold? As you've noted separating drivers into individual spaces to cover a wall will smooth out the in-room response to some degree. More is gained by placing the drivers in the center of opposing walls but that's not an option. I assume the horizontal vs horizontal line question is rhetorical given the last phrase in #3. Other than that your examples are just variations on a theme with little difference in performance. BTW your drivers are certainly bizarre looking, should be an interesting project .....   |
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Post by rexxxlo on Oct 10, 2010 14:06:08 GMT -7
well you found my woofers
hahah thats funny
ive been getting back into the reading and pro/con decision making stages as i have a little free time on my hands
yea the one wall is underground (house is on a hill) so no possibility of mounting woofers on that wall
the front is a large door going outside so cant put them there.
above is living space so i cant use the attic style tunnel , i used tunnel whoops i mean manifold, i have read in the faq's that there is phase response issues with that type of setup
back of the room is another room i cant disturb this leaves me with one option, the side wall
i think a horizontal array firing directly into the room will suffer from the wall flexing out of phase with the woofers
a vertical would do the same thing i assume so like you said its kinda rhetorical
this leaves me with an array with the woofers firing @ 90deg to the wall with one side of the cone firing into each room
or individual openings one per woofer again firing at 90 deg from the wall with an opening
id rather not do a horizontal arrangement to avoid suspension sag so vertical seems the most logical
id like the look of individual openings but i can place the array in the first stud cavity near the front of the room to help keep the phase ligned up with the mains
oh the driver is a hybrid built by me
lightning audio neo motors
copper dual 2 0hm round wire coils
dual opposed softer spiders and stitched leads
18" one piece aluminum cones accordion surrounds
if they work well ill keep them if i dont like them ill build something else with them
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Post by ThomasW on Oct 10, 2010 14:27:37 GMT -7
Horizontal arrays flex less then vertical ones since more studs are involved. Any flex decreases the output from the sub. When an attic isn't available and where space permits, I think this is the best way to mount 4 drivers, that being 2-2 driver manifolds  If one can't use 2-2 driver manifold, ignoring the door, this is a good way to put 4 drivers in a single manifold.  |
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Post by rexxxlo on Oct 10, 2010 16:40:09 GMT -7
those were 2 of the ideas i was basing my design on actually the door is kinda clever
that was the design i was most drawn to
many of the links are dead on the website so it makes getting the reasons why people have chosen one layout over another difficult
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Post by ThomasW on Oct 10, 2010 21:37:01 GMT -7
many of the links are dead on the website so it makes getting the reasons why people have chosen one layout over another difficult People usually choose a particular layout because it's the only option that's practical for their room. If I were omnipotent there wouldn't be any dead links. Problem is I can't control if people change ISPs and their website disappears, or they delete pics from a photogallery |
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Post by rexxxlo on Oct 11, 2010 6:31:41 GMT -7
how dare you lol
well this is a cult maybe everyone should drink the coolaid
well all the woofers are ready i should be able to start the build soon, bought some birch ply 77 sheets actually found a great score on craigslist actually some is 3/4" or 1" if i had room to store more i would have bought it
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Post by rexxxlo on Oct 16, 2010 21:26:44 GMT -7
ok im probably just obsessing over placement or that i just dont know or understand enough of the math yet but if i have a 13'7" long wall 9'6" tall how do i find the best location to cut holes in my walls? also the other dimension is 10'7"the manifolds are going to go on the long wall and the room will be setup lengthwise so they will be to my side the thing about this is its so permanent.  i cant just toss a woofer in there and move it around till it sounds good ive been looking for room mode calculators all day trying to decide whats good all i find is that there are modes at certain frequency's but i don't think i understand what to do? at that frequency or where in the room that node or antinode are placed. do i out the manifold openings at the place where there are no modes ? i think that's right  |
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Post by chrisbee on Oct 17, 2010 0:12:20 GMT -7
There are a number of very basic issues here which you should already be aware of: You don't want an IB beside you. Ideally it should be behind, above or under your main speakers. You test for best manifold position(s) with another subwoofer. Or two subs if you are separating two manifolds. You can use your own ears to see if you can hear the best spot for your subs. Or do as most do and use REW (or another frequency response measuring software) to see the results of moving them about. Since your speakers are hybrids I'd test the frequency response long before cutting any holes. As your subs are going in/on a wall you should lift the test sub(s) to the intended level. Use available furniture, workbenches or a stepladder to get them high enough if necessary. Got no existing subs? Then use your manifolds and drivers as sealed box subs. With the open side pointing down onto a board. Or onto a bit of carpet or sponge. You are aware that bass will be just as loud in the room in which the manifolds sits? You should have read the IB Cult FAQs by now and have absorbed all this basic information. |
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Post by legend3215 on Oct 17, 2010 3:28:11 GMT -7
If i understand him, his IB has to go on the "side wall". If that is indeed the case, then a single manifold for all 4 18's closest to the corner of the "front wall". BUT if he can re arrange his listening position such that the side wall becomes the front wall, then stereo IB's would be better. One close to a corner, the other about a third of the way from the opposite corner. OH ! and while I'm here, if anyone doubts the viability of a single IB (mine is in the right front/side corner) I played the channel idenitification tracks from Stereophile test CD2: the fender bass guitar you are about to hear should appear to come from the left loudspeaker only... and it sure does. Note: I cross @ 60. Attachments:
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Post by rexxxlo on Oct 17, 2010 12:32:59 GMT -7
There are a number of very basic issues here which you should already be aware of: You don't want an IB beside you. Ideally it should be behind, above or under your main speakers. i really dont have that option its either on the side or not at all i just have to deal with it unfortunately You test for best manifold position(s) with another subwoofer. Or two subs if you are separating two manifolds. You can use your own ears to see if you can hear the best spot for your subs. Or do as most do and use REW (or another frequency response measuring software) to see the results of moving them about. Since your speakers are hybrids I'd test the frequency response long before cutting any holes. if the response isnt up to par ill buy new woofers As your subs are going in/on a wall you should lift the test sub(s) to the intended level. Use available furniture, workbenches or a stepladder to get them high enough if necessary. Got no existing subs? Then use your manifolds and drivers as sealed box subs. With the open side pointing down onto a board. Or onto a bit of carpet or sponge. thats a great idea ill have to try this i figured that they wouldn't preform correctly like that but i suppose its just a test to see how they work right? You are aware that bass will be just as loud in the room in which the manifolds sits? yea actually i think thats a double whammy i can use the ob when im working in the garage too!!!You should have read the IB Cult FAQs by now and have absorbed all this basic information. ive read it quite a few times but this is a forum and participation is a good thing righ? what if there is some guy out there with my same dilemma but he wont ask ? the faq are for frequently asked questions right? im sure ill come up with some off the wall..... ones lol no pun intended |
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Post by rexxxlo on Oct 17, 2010 12:37:31 GMT -7
If i understand him, his IB has to go on the "side wall". If that is indeed the case, then a single manifold for all 4 18's closest to the corner of the "front wall". BUT if he can re arrange his listening position such that the side wall becomes the front wall, then stereo IB's would be better. One close to a corner, the other about a third of the way from the opposite corner. OH ! and while I'm here, if anyone doubts the viability of a single IB (mine is in the right front/side corner) I played the channel idenitification tracks from Stereophile test CD2: the fender bass guitar you are about to hear should appear to come from the left loudspeaker only... and it sure does. Note: I cross @ 60. i truly wish i could front mount or turn my listening position 90 degrees it would be very odd feeling. so you think that one manifold 2x18s tall with 2 per side like the above picture in the door would be the best idea and mount it as close as possible to the front corner? now that i can do <<<< goes and rethinks design again arghhh hahaha |
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Post by jimcant on Oct 18, 2010 0:08:27 GMT -7
If i understand him, his IB has to go on the "side wall". If that is indeed the case, then a single manifold for all 4 18's closest to the corner of the "front wall". BUT if he can re arrange his listening position such that the side wall becomes the front wall, then stereo IB's would be better. One close to a corner, the other about a third of the way from the opposite corner. OH ! and while I'm here, if anyone doubts the viability of a single IB (mine is in the right front/side corner) I played the channel idenitification tracks from Stereophile test CD2: the fender bass guitar you are about to hear should appear to come from the left loudspeaker only... and it sure does. Note: I cross @ 60. I have to say that this is the option I would choose in your situation, and there was nowhere else to go. I would like the IB as far forward of my sitting position as possible. Chrisbee's IB is in a somewhat similar location, I believe, and it works well for him  It is a fairly straight forward job to do as Chris has suggested and place a standard sub there, and listen/test for yourself, and if it sounds good, it is good, and you have no unwanted holes if it doesn't |
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Post by chrisbee on Oct 18, 2010 4:15:35 GMT -7
While there is absolutely so sense of the bass coming from the side I do suffer from a trough just below 200hz. This is a cancellation effect between the right main speaker and the upper IB drivers in the corner of the left side wall. The crossover point seems to make little difference to this trough.
While a side wall IB does work the position should be tested properly with the speakers running as well before making any holes. REW is a useful tool for this job because so any sweeps can be run in a short time as the test sub is moved about. (along the wall as well as up and down to see if it helps)
Note that any subwoofer would produce the same trough if offset to one side. This is not a fault of IBs in particular except for their relatively fixed position. Which is why I offer the general advice to place any sub somewhere between the main speakers if you have a choice.
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