2x18" IB's v's 4x15" IB's

[ThomasW]

Standard hidden manifolds or 'outies', the drivers operate the same and sound the same

However the drivers are oriented (magnets in or out), and where ever the manifolds are placed (standard hidden manifold or 'outie'), the drivers must be wired so all the cones need to move in and out at the same time.

[Wull]

So am I right in thinking apart from a distance gain of 1" by lining the manifold and then mounting two of the IB's internally, would it work just as well mounting them from the outside with the magnets facing each other in the manifold?

This would be a lot easier way to install the IB's.

[ThomasW]

The amount gained when a driver is reversed is equal to the depth of the cone

[Wull]

Sept 19, 2010 17:32:27 GMT -7 ThomasW said:

The amount gained when a driver is reversed is equal to the depth of the cone

Nicely explained Thomas, now I get it, at last! Thanks.....

[Wull]

I got my IB up and running over the weekend. I managed to line the inside so I could have 2 IB's magnets in, and the other 2 out.

EQ using my 1124 BFD, and from the seated listening position it sounded awesome, so much more upper bass punch than my ultra had.

The problem I have now is the closest corner opposite my installed IB is very bass boomy, this boomy bass also runs the length of my living room wall.
My living room is 13-14' wide, 24' long, everything is fine up till about 10' across the width of my room away form the IB. It's in that last couple of feat that the bass is really pronounced/boomy.
I have been reading up on bass traps, and may get myself some 4" rockwool and position these pannels around my room to see if this will help.
Has anyone else experienced this problem before?

Any ideas??

Cheers

[ThomasW]

In the history of this forum you are the first person to ever use the word 'boomy' when describing the output of their sub.

We need to see some measurements of the output from the IB. Both with and without the 1124 in the circuit.

It's a good idea to do a nearfield measurement for comparison. This is done with the mic at the opening of the manifold and no EQ.

Using a single sub location there will without doubt be peaks and valleys in the room. This can be tamed to some degree with bass traps. Given what you're hearing you should google 'super chuck bass traps' and probably start off with those.

Another way to even out in-room response is to have a sub in the front and one in the back of the room. This means using 2-2 driver manifolds.

[Wull]

Taken at manifold no EQ

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[Wull]

Taken at manifold EQ

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[Wull]

Taken at seatin position. IB eq and main speaker

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[Wull]

My IB

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[Wull]

Outside

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[chrisbee]

Congratulations on your IB build being successfully accomplished.

Your boominess is probably directly related to your room. Provided the effect is not noticeable at the listening position it can be ignored.

Single sheets of insulation wadding applied to the walls will have almost zero effect at low frequencies.

Corner filling, triangular columns have been mentioned here as quite useful for LF absorption. I believe they are effective since they exist at a position of very high acoustic pressure. This is easily confirmed by standing in the corner of a factory or other large workplace. It can be quite nauseating to stand just there in a large, noisy environment. Presumably the corner reinforces well down into the deep infrasonics.

Membrane absorbers are also useful. Consisting of a flexible board backed by insulation contained in a large, shallow box.

[Wull]

Thanks Chrisbee. I haven't had the chance to really try it out yet, but what I have heard/felt is fantastic. I am very happy. The louder bass has not been as bad tonight, so time will tell I guess. In the good seat it really kicks. ;D

Going to have a go at making some super chuck bass traps

[Wull]

another pic

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[Wull]

Head shot

[Wull]

Hi there.

Well If you have been reading this thread you may have quite easily come to the conclusion that I do every thing in a rush, sometimes it works, and some times it doesn't.
Having felt that the bass was louder, more pronounced down one side of my living room than I liked, I decided to cut my losses and move the IB to a more central roll, so now it sits in front of my PJ screen, I would say about 1.5mt rs from both walls, so well out of the corner.

You know I had never noticed this bass problem before, but having given greater time to listen I found that even my main speakers produced similar results, just not as loud. I guess it's never been drawn to my attention before, so I've never noticed it.
Well with the IB manifold in it's new position I can say the bass is no where near as it was before, it's still is slightly louder down one side, but I can live with this, and I shall when I get some free time proceed with some superchunks as Thomas suggested. I have one corners worth already cut, just need to make the frame.

After a very quick set up using my antimode 'for now' got a very good response. So I was finally at last able to give my IB a proper run out last night, watched war of the worlds with the screen down, what can I say WOW this kicks, never did I feel it was strained, or at it's limits, totally awesome, and the screen never budged . I spent the rest of the evening with the misses listening to music, now this clean bass I had kept reading but not fully understanding what was meant by it I sure do now.

I shall post my last pics when my speaker cloth turns up, but the new positioned install has gone well, I just had to shorten the manifold slightly 'pitched roof', and cut out an opening in the black cloth board that I use to help improve my PJ's contrast, but this hides it well.

Thanks Thomas and Chrisbee

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[ThomasW]

Good to hear relocating the sub helped with the problems

[Wull]

I am considering adding another IB manifold later this year, this will be positioned in line with the original front 4 x 15" FI IB manifold, but at the back of the room.
The front manifold is 12 ft away from the seating position, the rear IB would be 6 ft away.
My questions is will it be OK for me to use just 2 x15" FI IB's not four like the front.
Will my Behringer EP4000 be able to take the extra load. My current IB's are 4ohm coils, run as a 4ohm load, these are then connected to the EP4000 in bridged mode quoted at 1 x 4000 watts, so these would have to run of one channel reducing it to the quoted 1,400 watts in to 4 ohms

[rockrover]

Congrats on your IB placement! The EP4000 really only puts out an honest 1.8kw. See AVS forum Amp shoot-out. I would buy another EP and forget about it. Watts are cheap!

I would love to find a few (4ea) Fi's. Were are you buying yours?

--D

[Wull]

I can't get hold of any Fi's either, I'm waiting on the new design. Been told they should start shipping by the end of April hopefully.
Bladeice hope to be able spec the new ones to the old design? I just wanted to check as regards to amplification and amount of drivers etc