close to wall

[ross]

I am considering the IB, really want to make it happen. I do have a few concerns :

With the drivers motors on the outside of the manifold (outie?), the motors on the one side are near the wall. Is there any serious issues here? What would the recommended minimum distance from vent for the motor to the wall be?

With a manifold and an Outie, is there a recommended minimum for the manifolds surface area? The drivers will load from the inside of the manifold, so the manifold will be at least an inch more than the depth of the driver. Perhaps there is an equation or ratio for the amount of displacement for the amount off surface area for the manifold?

I noticed OSB is used with plywood. Is there any reason (as far as performance goes ) why 2 layers of plywood aren't used instead of the OSB/Ply combo?

If the manifold has drivers on 2 sides, this is said to balance the forces. In a large manifold ( 8drivers - 2 rows of 4 drivers), is bracing still recommended? If so, for every driver pair, in this case 3 braces?

With a balanced manifold, does the wall the manifold is attached to have vibrations that are audible and hard to tame?

Some drivers, like ShivaX, can get a damp alignment with a small room for the IB. If the room is 8' x 8' x 7', this could be more than Qtc of .5 . Would it be recommended to reduce the IB room until Qtc is .5?

[ross]

Mar 26, 2011 22:21:27 GMT -7 ross said:

I am considering the IB, really want to make it happen. I do have a few concerns :

With the drivers motors on the outside of the manifold (outie?), the motors on the one side are near the wall. Is there any serious issues here? What would the recommended minimum distance from vent for the motor to the wall be?

With a manifold and an Outie, is there a recommended minimum for the manifolds surface area? The drivers will load from the inside of the manifold, so the manifold will be at least an inch more than the depth of the driver. Perhaps there is an equation or ratio for the amount of displacement for the amount off surface area for the manifold?

I noticed OSB is used with plywood. Is there any reason (as far as performance goes ) why 2 layers of plywood aren't used instead of the OSB/Ply combo?

If the manifold has drivers on 2 sides, this is said to balance the forces. In a large manifold ( 8drivers - 2 rows of 4 drivers), is bracing still recommended? If so, for every driver pair, in this case 3 braces?

With a balanced manifold, does the wall the manifold is attached to have vibrations that are audible and hard to tame?

Some drivers, like ShivaX, can get a damp alignment with a small room for the IB. If the room is 8' x 8' x 7', this could be more than Qtc of .5 . Would it be recommended to reduce the IB room until Qtc is .5?

Sorry everyone, I learned that this is not the Outie.

I also just read about how IB's are not recommended if the only placement is in the back of the room. What if the LP filter is 8th order and set low, 40Hz and time aligned? Still a serious issue?

[ThomasW]

I'm not sure why we're revisiting questions that were asked and answered 3yrs ago...

ibsubwoofers.proboards.com/index.cgi?action=display&board=projects&thread=1129&page=1

Mar 26, 2011 22:21:27 GMT -7 ross said:

I am considering the IB, really want to make it happen. I do have a few concerns :

With the drivers motors on the outside of the manifold (outie?), the motors on the one side are near the wall. Is there any serious issues here? What would the recommended minimum distance from vent for the motor to the wall be?

12" min

With a manifold and an Outie, is there a recommended minimum for the manifolds surface area?

Yes see the main FAQ page

Perhaps there is an equation or ratio for the amount of displacement for the amount off surface area for the manifold?

No such thing exists

I noticed OSB is used with plywood. Is there any reason (as far as performance goes ) why 2 layers of plywood aren't used instead of the OSB/Ply combo?

See the Gemeric Design/Build/Install FAQ pages

If the manifold has drivers on 2 sides, this is said to balance the forces. In a large manifold ( 8drivers - 2 rows of 4 drivers), is bracing still recommended? If so, for every driver pair, in this case 3 braces?

Yes big manifolds need stiffening braces

With a balanced manifold, does the wall the manifold is attached to have vibrations that are audible and hard to tame?

Depends on how the wall is constructed

Some drivers, like ShivaX, can get a damp alignment with a small room for the IB. If the room is 8' x 8' x 7', this could be more than Qtc of .5 . Would it be recommended to reduce the IB room until Qtc is .5?

I have no idea what you mean by the question "reduce the IB room...."

A somewhat higher Q would be the least of your problems when the room is virtually a cube, = acoustic nightmare

I also just read about how IB's are not recommended if the only placement is in the back of the room. What if the LP filter is 8th order and set low, 40Hz and time aligned? Still a serious issue?

Should work

[ross]

Thomas,

thanks for that link, I should have looked for that first. Sorry.

By the IB room, I am referring to the space the drivers consider an enclosure. Some people use crawlspaces, attics, spare bedrooms even closets. As for the shape, there is another room right next to this and leaving the door open or off would offer another 6000L and remove a cube possibility. That will have to be tested.

Anyone have experience with a linear motor and an IB with a Qtc that is .5 or lower?

Regarding placement:

"5) Where should I put my IB?

Due to the design most people don't have the luxury of choosing between multiple placement options. If possible, placement should be on the front wall, floor, or ceiling, centered between the main speakers. This allows the greatest flexibility of crossover points, and that guarantees the sub won't smear the stereo image. Frontal side locations work well too. Locations behind or beside the listener are not recommended (see #19 for more info about IBs behind the listening position). The more off axis compared to the main speaker, the lower the crossover point should be."

What about placement of a mono manifold on a sidewall with a 48dB low pass slope at 40Hz and time alignment, could this still blend well with the mains? I realize it isn't ideal, but it seems like my only real option.

[ThomasW]

Mar 27, 2011 7:19:39 GMT -7 ross said:

Anyone have experience with a linear motor and an IB with a Qtc that is .5 or lower?

There are dozens of them, my two included.

Remember we're taking about things that are relative not absolutes

The average person couldn't tell the difference between a sub with a Qtc 0.5 and one with Qtc of 0.69 if their life depended on it.

I don't know if having an open doorway between the rearwave room and an adjacent space will make much difference as far as sound quality is concerned. So this will be your experiment.

What about placement of a mono manifold on a sidewall with a 48dB low pass slope at 40Hz and time alignment, could this still blend well with the mains? I realize it isn't ideal, but it seems like my only real option.

First it was the back of the room now it's the side. How about posting a pic and a floorplan if possible? That will make answering the questions easier

[ross]

Mar 27, 2011 9:43:12 GMT -7 ThomasW said:

Mar 27, 2011 7:19:39 GMT -7 ross said:

Anyone have experience with a linear motor and an IB with a Qtc that is .5 or lower?

There are dozens of them, my two included.

Remember we're taking about things that are relative not absolutes

The average person couldn't tell the difference between a sub with a Qtc 0.5 and one with Qtc of 0.69 if their life depended on it.

I don't know if having an open doorway between the rearwave room and an adjacent space will make much difference as far as sound quality is concerned. So this will be your experiment.

What about placement of a mono manifold on a sidewall with a 48dB low pass slope at 40Hz and time alignment, could this still blend well with the mains? I realize it isn't ideal, but it seems like my only real option.

First it was the back of the room now it's the side. How about posting a pic and a floorplan if possible? That will make answering the questions easier

sorry again. Original idea was back left corner - but the manifold on the left wall, not the back wall. Sorry for lacking in my description . At that location, the motor would be less than the 12" min recommended distance from a wall. I have seen some where the motor looks close to walls, that is why I asked. Time to move on and leave that problem behind.

If I slide the manifold along the wall away from the corner (about 3ft from corner, firing through side wall) to achieve the min clearance , this is another option and it will have clearance. Would this location be suitable with a 40Hz 48dB LP filter and time alignment? I am just filling in the last octave, or perhaps last few octaves

I need to write my posts better for now on. Sorry about this.

[rockrover]

Hey Ross,

Sounds like we have about the same issues. Small room, small manifold enclosure...Door open/closed. I've posted in the general section, and I'll move to the build section if/when 18's (or quality IB 15's) become available again.

Good luck with your build! I honestly think I'm just gonna' "do it" unless Thomas or someone else tells me it's not a good idea at all.

TTFN!

--D (Rockrover)

[ross]

Mar 27, 2011 22:40:00 GMT -7 rockrover said:

Hey Ross,

Sounds like we have about the same issues. Small room, small manifold enclosure...Door open/closed. I've posted in the general section, and I'll move to the build section if/when 18's (or quality IB 15's) become available again.

Good luck with your build! I honestly think I'm just gonna' "do it" unless Thomas or someone else tells me it's not a good idea at all.

Rockover - that is what I was thinking, just do it . Not so easy to do if we dissect every possible issue, but just do it and find out. I have experienced subs crossed higher and with slopes not as steep and it worked well. Those weren't IB though, perhaps IB blends into the system better .

Have you considered Fi18 or TempestX? Why are you set on 18's?

TTFN!

--D (Rockrover)

[rockrover]

Sure I've considered the Fi and the Tempests! ETA on the new stock continues to be a mystery however. Planing around a "maybe next month" delivery is hard for me. Usually when I start a project I like to flow through progress without waiting for inventory...But that's just me.

18's are just a thing with me. When it's two 18's or 3 15's the choice becomes clear. With only a 1.5" increase in radius I eliminate one driver and have more Vd.

Thomas thinks I'm wasting money on my proposed 4ea 18's in my little room. Maybe it is, but what I want is NO excuse, no holds barred, "you're crazy", system that leaves wantin' for nuthin'!

Then again I only want to spend $1200 on drivers MAX. If/when the new drivers hit the scene, and they are $400 shipped...Well, I'm back to two! I started this whole design thinking Fi would ship 4each 18's for $899. I think that deal is long dead and buried.

What ever happens I think I'll have a hole in my drywall!

Make sure you post up your progress and pics. Not too many new projects lately. (maybe that's why there aren't any drivers available!).

--D