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Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure
They will be, and it will be fantastic.
First floor of a high ranch, no basement due to proximity to the ocean. It currently hits over 130db at 20hz with ridiculously low THD. I hit the limits of my mics trying to measure it. With room gain, I get some monster levels at 10hz too. Problem is, between 15-20hz at high levels, excursion goes nuts. I've had the cones tap the spiders, though it was lightly, that's not good. That was my main motivation to do this build.
Me too! 
I can't wait to get the rest built.
The walls flex pretty good. I built the first floor of this house with the idea in mind that there would be a ridiculous system in it at some point. In hindsight, I should have double-rocked it. The walls still flex a good deal. It's interesting that as I raise the levels I see some room modes disappear or shift frequencies.
I used WinISD for calculating the port length. It doesn't give you much in the way of picking port ends, and since this is a slot port, there aren't really any common flares. It just uses 0.732. There was much discussion about the port before the build. Some were saying they say WinISD off by as much as 25%. I took the safe route and originally made the port 40" and left some space in the bracing so I could lengthen the port if necessary. With a 40" port the tune came in around 17hz. I added 15" and it dropped it to about 14.7hz. You can see a pic of the added port length here. Hard to tell exactly, but that's my best guess based on measurements and watching cone excursion. WinISD says it should be 55" for a 15hz tune and 57.6" for a 14.7hz tune, so it's quite close. If I flared the ends some or if it didn't have a 90' bend it might be more accurate. This box was built as an experiment, to see worst case what would happen. I didn't use any dampening material, I didn't round any port corners or flare any of the port ends. I will be hitting the ports in the front with a router just to make it look not so hideous. Pushing this loud enough to make everything in my garage sound like its going to fall off the walls and the ceiling flexing noticeably, there is no discernable port noise. Putting dampening material inside would affect tuning some, so I left it out as well. Any of the resonances it would help will be far enough out of the bandwidth that this will be used in. It seems the extra work doesn't really pay off, so that's fine by me.
The LCR's are JBL pro cinema gear. 4722N's for the L/R, a 3677 for the C, and 8350s for the surrounds. At the prices and performance there, I couldn't convince myself to build.
I have full info up at http://www.countercultured.net/pics/ht
Well, the filter is actually at 11hz, but you can see in the graph below that it flattens out the room gain some. By 7hz, it's -3db, then completely falls off. A bunch of movies have a good deal of content sometimes down to 3hz. 7hz is my -3db point, so I just tossed that number out there. War of the worlds, during the lightning and pod emergence scenes has some notoriously low frequencies. How to train your dragon as well. As you drop down to these super low frequencies, excursion skyrockets, so some protection is necessary when playback levels are high. Also, adding this in here, some recordings you'll find have subsonics from like, doors closing. I'll notice my drivers move at low frequency and it slams the door to the theater shut. Vinyl playback can be interesting as well. There's content there... but in the end, filters serve two purposes, protection, and taming the ridiculous room gain that made things sound/feel awkward whenever there was low content. Turning on an Xbox 360 for example sweeps upwards from very low, at least 10hz.
This is post-eq with a little bit of bass boost. There's a room mode where I measured this at 80hz, I know I wonder if having these massive cabs in the corners now will affect my response any. I'll definitely be following up on that once I get everything completed and put in place.
Originally posted by Tin_Ears
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Dang... and I thought my six IB 18's are gonna be overkill.
Originally posted by tomzarbo
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You like to play your movies a bit on the loud side?
Awesome setup BTW. Scary, but awesome.
I was hitting 115+ db in room at 20 Hz with my "Beast" setup using four ported 12" Titanics. I never could crank it up to where it gave out because my head felt like it was going to implode. Made the window on the gable end of the attic vibrate 1/2" each way during sweep testing. I turned it down after that. I can't imagine what your setup would do. Where is this at, basement?
TomZ
Awesome setup BTW. Scary, but awesome.
I was hitting 115+ db in room at 20 Hz with my "Beast" setup using four ported 12" Titanics. I never could crank it up to where it gave out because my head felt like it was going to implode. Made the window on the gable end of the attic vibrate 1/2" each way during sweep testing. I turned it down after that. I can't imagine what your setup would do. Where is this at, basement?
TomZ
Originally posted by saabracer23
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I can't wait to get the rest built.
Originally posted by ryanc
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Originally posted by dstmbgh
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The LCR's are JBL pro cinema gear. 4722N's for the L/R, a 3677 for the C, and 8350s for the surrounds. At the prices and performance there, I couldn't convince myself to build.
I have full info up at http://www.countercultured.net/pics/ht
Originally posted by dstmbgh
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This is post-eq with a little bit of bass boost. There's a room mode where I measured this at 80hz, I know
I wonder if having these massive cabs in the corners now will affect my response any. I'll definitely be following up on that once I get everything completed and put in place.
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