[91clone]

When I got into the office this morning I had these little gems waiting on me! No going back now.

I am sure I will have plenty of questions along the way but I will start with power. I plan on using an inuke6000dsp. First question is where is the best price right now for this amp?

 

[kiwijunglist]

Hehe. I have 4 of these. Going into dual sealed subs with inuke 3000dsp.

I think ib is a good idea bc they are a bit ugly without grills compared other drivers.

 

[LTD02]

congratulations.


not too long ago folks were getting $365 delivered from sam ash and musiciansfriend iirc, but you had to call for best price.


that amp is a decent choice for this app. I'm not sure how those drivers are in free air, so just be careful until you get a sense of power vs. excursion. as you may know, i.b. typically require very little power (relative to smallish cabs) to motivate the driver to (and past) full excursion.

 

[More is Better]

that amp is a decent choice for this app. I'm not sure how those drivers are in free air, so just be careful until you get a sense of power vs. excursion. as you may know, i.b. typically require very little power (relative to smallish cabs) to motivate the driver to (and past) full excursion.

He'll end up with all 8 subs on one channel at 4ohms. 1800/8=225W per sub. Limited to 1750W so it won't clip and with a -3db low shelf filter at 20hz or a 6hz -3db .5q PEQ, excursion won't go over 18mm. Basically a bulletproof setup.

All of them will be in the same manifold so I don't see any need for multiple dsp channels going to these. And the other channel can be used for a sealed 18 somewhere in the room, down the road.

That's a good start 91

 

[91clone]

Thank you! I took a chance on the suggestion of another member on 8 of these vs 4 of the SI 18's. I know they probably aren't the absolute best driver for this application but for the money I had to try. At least with an ib I won't have a ton of money and time in the enclosure!

I will check those sites for that amp, thank you. I haven't ever heard a system capable of ULF so I am thinking if I need to I can HP these before they run into trouble down low and get a little more out of them. Maybe once I experience the ULF I will be hooked?? Who knows

I want to begin designing the manifold. It will be placed between a typical stud cavity in the wall. The width is 14.5" between the studs. Is there any certain volume the inside of the manifold has to be?

 

[LTD02]

as large and as shallow as possible. if it turns into a long tube like structure, it can start to function like a horn and cause a big peak between 100 and 200 hz. that could be mostly fixed with eq, but avoiding the problem in the first place is probably best.


as for eq, you get a 'free' high pass filter around 7hz 1st order in the amp, iirc. so excursion will be aided a little there. 250w is actually quite a bit for that driver in ib. i'd suggest starting a little lower until you are comfortable with how everything is going.


loads of bass for sure.

 

[More is Better]

To keep excursion under control: They can be limited to 900W, or 3db needs to be eq'd out below 20hz.

By using the 3db low end cut 20hz audible frequencies.

 

[91clone]

On the manifold, since they are 15's and the cavity will be 4" deep with the stud and drywall 20" would be about the shallowest I could make it. Height can be whatever. I would think minimum would be around 6'. Would it improve the sound to make it taller and space the woofers farther apart from floor to ceiling? I have about 100" to work with.

I guess I can play around with the limiters and filters on the amp to see what I like best. Like I said, I have only read on here about the sub 20hz stuff so no real world experience with it. I don't think my single 12" tuned to 19hz gave me any of that in the last house.

We are just about done with the sheetrock in the new house so I can get started building the manifold pretty soon. It will be closer to July though before I actually start installing these things.

 

[More is Better]

I want to begin designing the manifold. It will be placed between a typical stud cavity in the wall. The width is 14.5" between the studs. Is there any certain volume the inside of the manifold has to be?

Like LTD said, you want to maximize the area of the "port" entering the room between the studs. You also want to minimize the depth of the manifold so it doesn't act like a real port.

I was thinking that you could use 4 dual opposed manifolds that would have OD's of 14.5"Wx17"Hx(17"+stud depth) 20.5" or 22.5" D each. Made out of 3/4" Ply. Just slide each one between the studs up to the back of the drywall and screw through the studs and plywood. You can use a flush trim router bit to cut out a perfect hole in the wall. If you want to overbuild them, put a 2nd layer of 3/4 ply on the 17x17x14.5 part that is behind the studs. The box size is minimized while the port area entering the room is maximized. There ends up being 210sqin of box opening and 257sqin of cone area for 2 subs.

The drivers have a 6 13/16" mounting depth, and so they can be mounted with both magnets in the box, both cones in the box, or one magnet and one cone in the box (Push Pull style). All 3 ways will cancel out vibrations. For ease of assembly, I would put magnets in the box so that you can just screw the speakers in from the back side of the wall. Wire all 4 voicecoils in each manifold in series to get a 16 ohm load per manifold, then run the 4 pairs of wires to one channel of the sub amp.

With 9' ceilings you can space the 4 manifolds out centered at 13.5", 40.5", 67.5", and 94.5". That should fix any vertical room modes.

 

[Mattcc22]

If you can I would wait until Memorial Day. Should be able to get a good sale price then on the amp.

 

[91clone]

MIB- I had just pictured doing one manifold pretty much centered on the wall. I will think about you idea of the individual manifolds. Whatever I do, I will have to cover it somehow to make it look good.

My initial thoughts are making one big speaker grill cover with a beige colored speaker grill cloth and using magnets to hold it on. If I did the 4 individual manifolds then I would have 4 seperate grills. I am trying to picture in my mind which way would look better??

Matt- Good idea on waiting for a sale. I am in no hurry so i will be sure to keep searching especially around the holiday. If you come across a steal let me know! Thanks

 

[More is Better]

MIB- I had just pictured doing one manifold pretty much centered on the wall. I will think about you idea of the individual manifolds. Whatever I do, I will have to cover it somehow to make it look good.

My initial thoughts are making one big speaker grill cover with a beige colored speaker grill cloth and using magnets to hold it on. If I did the 4 individual manifolds then I would have 4 seperate grills. I am trying to picture in my mind which way would look better??

Matt- Good idea on waiting for a sale. I am in no hurry so i will be sure to keep searching especially around the holiday. If you come across a steal let me know! Thanks

You can still make one big grill either way.

I think you will want them spread out along the wall to excite different room modes

Making an 8 foot tall manifold is another option.

 

[91clone]

Duh! Didn't think about that! It would be easy to do one grill and have the same look.

I had no idea it would smooth out the sound by spacing them apart from floor to ceiling. I need to check in the storage room side to see if there is any duct work in the way up top.

It might be easiest to make one manifold 8' tall like you said. Would be a lot heavier though

 

[LTD02]

room modes form based on wavelength and room dimension.

this arrangement is nearly ideal:

but of course, not always practical.

 

[More is Better]

room modes form based on wavelength and room dimension.

this arrangement is nearly ideal:

but of course, not always practical.

LTD:
Does 1/8 - 1/4 - 1/4 - 1/4 - 1/8 spacing with 4 sources work better than just having 2 sources as 1/4 points 1/4 - 1/2 -1/4 ? Dashes being manifolds.
IE 16 sources in your 2d front wall diagram. 1 manifold in each trough on the 4th order modes graph.

 

[moosifee]

LTD:
Does 1/8 - 1/4 - 1/4 - 1/4 - 1/8 spacing with 4 sources work better than just having 2 sources as 1/4 points 1/4 - 1/2 -1/4 ? Dashes being manifolds.
IE 16 sources in your 2d front wall diagram. 1 manifold in each trough on the 4th order modes graph.

I thought you and I had the same question, but now I think we only have a similar question. I wonder what happens if you only have two sources.

 

[LTD02]

LTD:
Does 1/8 - 1/4 - 1/4 - 1/4 - 1/8 spacing with 4 sources work better than just having 2 sources as 1/4 points 1/4 - 1/2 -1/4 ? Dashes being manifolds.
IE 16 sources in your 2d front wall diagram. 1 manifold in each trough on the 4th order modes graph.

to see how such an arrangement (or any arrangement for that matter) works, just work through each mode picture one at a time.


for your arrangement, first order mode:
the left side and right side 1/8. one is blue, the other is pink, same curve height at both, so they cancel.
the left side and right side 1/4. one is blue, the other is pink, same curve height at both, so they cancel.
the 1/4 in the middle will not excite the first mode because there is neither blue nor pink.
everything either cancels or does not excite the first mode.


second order mode:
the left side and right side 1/8. one is blue, the other is blue also, same curve height at both, so they ADD.
the left side and right side 1/4. both are in neither blue nor pink. no modal excitement from them.
the 1/4 sub in the middle will excite the pink.
so for the second order mode, you have two blue that are at about 70% of full power and one pink that is 100% power, so 2*70 - 140 MINUS the cancellation from the pink 1*100% = 40% net blue mode excitement.


what you will notice is that all symmetrical alignments "balance" all odd-order modes. so with a symmetrical alignment, the modes that matter are the evens. the 4th is further down the priority list than the second. the arrangement at 1/4 distances cancels or does not excite modes 1,2, and 3. it creates some net modal excitement at mode 4, but again, that one tends to be further down the priority list.


the calculations are performed first in the x-axis (width), then in the y-axis (height), then in the z-axis (depth). sine the 1/4 distance spacing is also working in the y-axis, modes 1,2,and 3 get cancelled or not excited there too.


then one has to do something about the depth modes. seating placement, absorption, or even active cancellation are some strategies there.

 

[LTD02]

not sure if this help see how second order modes are not excited by this placement or not.

 

[LTD02]

here is the first order mode. since there is an equal amount of subs in the blue and the pink, those modes will be self cancelling.

in the horizontal axis, subs on the left excite blue at about the 70% amplitude, while the subs on the right excite pink by the same 70%, so they cancel.


same thing in the vertical plane.

 

[LTD02]

of course, all that is for the ideal state, lots of arrangements work just fine.


if you have only one placement though, best not to put it right in the corner (because all modes will be maximally excited) nor put it dead center of a wall (because height and width second order mode will be maximally excited, see post 18 above, all the pink and none of the blue would be excited).