After reading Andrew's posts I got the itch to install an IB. I had a floor vent in the front of the room which used to be from a wood stove that I no longer use. I mounted a small box under the floor and had a tempest fire up thru the vent. Looks alot like this one I found from the cult of infinitely baffled. http://users.rcn.com/mjrjunk/Sub1.jpg except I only had one side. Previously I was using a 150l sealed. I am definitely keeping the IB. I had a much smoother response and still had plenty of output. I was thinking of adding a second tempest but not sure if I will need it. Only took 3 filters and I had flat eq using the BFD. I will be enlarging the vent once I get a bigger floor grill, but for know I am quite pleased.
Installed IB
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Unless the floor vent is as big as the diameter of the driver it's acting like a bandpass filter not a true IB. That will color the sonic characteristics of the output.
Obviously what's important is that you're happy with the results.
theAudioWorx
Klone-Audio
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson- Bottom
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That's what I figured, so I am making a small manifold that will have the driver on the side of it. The opening for the vent is 4x12 right now. I understand that the opening should be the SD of the driver correct? If that is the case what size should the vent opening be? I can go a little bigger. I figure since it sound so good now anything I do can be an improvement.- Bottom
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If that is the case what size should the vent opening be? I can go a little bigger.
theAudioWorx
Klone-Audio
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson- Bottom
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Originally posted by ThomasWUnless the floor vent is as big as the diameter of the driver it's acting like a bandpass filter not a true IB. That will color the sonic characteristics of the output.
You can model it as a 4th order bandpass box with a huge rear volume, a tiny front volume and a rectangular port. Without knowing the exact dimensions used here, I get a "box tuning" of something like 200Hz so it's probably well above the sub range and not too much of a problem. If it were a problem you could use a BFD filter to knock down the resonance peak and improve the XO blend.
Overall, I don't see it as any more of a problem than the huge manifold and small opening of the 12 Shivas. Obviously that floor opening is far less than 12*Sd. The trick is to keep all the bad stuff above the frequency range where you'll be using the sub.- Bottom
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Yeap my 12 driver IB has a smaller opening (14.5"X14.5") than my 4 driver IB.
Remember other than Nousaine's there weren't any other manifold IB's out there when I built these, so I was sort of the 'beta tester' for the planet .
It was obvious when I fired up the little IB that it's overall SQ was slightly better than the big one. Since the drivers were identical the obvious difference was the size of the outlet.
That's one reason I continuously harp about having people use the largest opening possible, (with-in reason of course)
theAudioWorx
Klone-Audio
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson- Bottom
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Here's a pic that demonstrates the effect with a randomly selected driver
theAudioWorx
Klone-Audio
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson- Bottom
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It was obvious when I fired up the little IB that it's overall SQ was slightly better than the big one. Since the drivers were identical the obvious difference was the size of the outlet.
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Yep, I'd think the depth of the manifold would be as much or more of a factor than the size of the opening. You'd get a 1/4 wave cavity resonance and a 3' deep manifold would be nearly into the sub frequency range. As well, you'd get some time smear from the bottom drivers having a longer path to your ear.- Bottom
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I ask Nousaine about this before building my big IB. His with a ~8' tall (floor to ceiling in basement) manifold has big time cancelation at 71Hz. For him that wasn't an issue because his XO point is 70Hz.
Mine should be above 100Hz, so no major issues there either.
theAudioWorx
Klone-Audio
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson- Bottom
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