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Old 11th February 2013, 11:57 PM   #11
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JapanDave,
Something that you need to think about is that others may not appreciate your production of frequencies that low. I have developed some low frequency bass enclosures and one of the comments was that neighbors, and I am using that as a bit of a misnomer, have complained about the low frequency output. What I am talking about is not a direct neighbor but someone actually down the block, not even the same building! You can not stop those wavelengths from emanating over long distances. The US Army at one time had extremely large and powerful bass horns that were used to knock down buildings! No lie you can cause physical damage at such low frequencies. I once had some low frequency horns in a famous nightclub in Los Angeles and when we turned them on 30 plus years of dust high up on exposed ducting came raining down on everyone's head. Everything that could in the room resonated, it was a nice learning experience. I can believe the notion that some may get sick or toss their lunch with such low frequencies. This is not a myth, most times the output is just not sufficient to do that but if you have the db output you will soon find out that you don't want to do that. Very few direct radiator devices can or will do that without self destruction. There are electronic circuits that are designed to have a bass speaker work below it normal resonant frequency but the power requirements to work with them are extreme in themselves to drive a device this low.
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Old 12th February 2013, 02:49 AM   #12
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I don't doubt that some people could be affected by ULF, such as headaches , nausea and disorientation, but bowel control or bladder control that is what I was saying was an old wives tale.

Keeping the thread on track, there certainly are devices that can reproduce ULF in the common home, take the rotary sub for example.

What I am talking about is boosting the lower frequencies to apply a house curve (And goes without saying if the sub/amp is capable doing doing this) . I not looking at playing silly SPL levels as I almost never play a movie at reference, which is probably a big reason why I want to be able to do this.
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Old 12th February 2013, 03:33 AM   #13
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JapanDave,
If you are after just the sensation of ultra low bass like in a movie why not just go with some shakers that could be a simpler solution. Not like your going to hear anything this low, but you do feel the vibration in your body. I see in some of the latest movie theaters here they are putting individual shakers on each seat in the theater. Doesn't take up all the space of a low frequency enclosure either.
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Old 12th February 2013, 03:38 AM   #14
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Quote:
Originally Posted by Kindhornman View Post
JapanDave,
If you are after just the sensation of ultra low bass like in a movie why not just go with some shakers that could be a simpler solution. Not like your going to hear anything this low, but you do feel the vibration in your body. I see in some of the latest movie theaters here they are putting individual shakers on each seat in the theater. Doesn't take up all the space of a low frequency enclosure either.
I have shakers, it is not the same unfortunately. I much prefer the effects of the ULF in a movie.
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Old 12th February 2013, 03:45 AM   #15
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Well then I would be looking at at least an 18" speaker then to move the volume of air your talking about at that low a frequency.
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Old 12th February 2013, 04:24 AM   #16
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Dave,
A dcx, mini-dsp, bassis, dsp-30 or any number of other devices will do a shelf boost. Commonly used to extend the response of sealed systems. You seem to want a tailored house curve with rising response all the way down. This will be difficult to accomplish without dedicated hardware and I would not recommend it. Technically a mini-dsp will do it or a bassis. You will be fighting electronics roll off, and asking for huge amounts of current from the LG's using up a lot of their headroom for very little perceptible gain. Just shelve up the low stuff with a slope that kicks in in the 15-20Hz range. Adjust to taste and let your room acoustics and electronics respond how they do at the bottom without trying to force the response into a nice shape. Adjust a broad range of frequencies mildly instead of notching small ranges aggressively. That's what I do with mine and I only use enough boost or cut to get flat. Getting trustworthy measurements in that range is another big obstacle as well.

This might not be the best place for this discussion btw.
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Old 12th February 2013, 05:11 AM   #17
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Quote:
Originally Posted by Josh Ricci View Post
This might not be the best place for this discussion btw.
I agree.

Consider the topic solved please. Thanks for all the advise and help guys.
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Old 12th February 2013, 01:26 PM   #18
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The Bag End ELF system goes to 8hz, it could easily be made do 5hz if that's what you need.

They have several versions up to a quad 21" woofer model.
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Old 3rd January 2014, 04:57 PM   #19
Mihkus is offline Mihkus  Estonia
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I didnt want to create new thread so I write here...
I need +12dB boost at 28Hz, got 12" subwoofer with 150W amp.
Built a large enclosure tuned to 28Hz but theres smooth drop from 35Hz, I want to fill it up with extra power.

Got lots opamps, caps, resistors... pretty much everything i could need.
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Old 3rd January 2014, 05:27 PM   #20
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Do you need a peak or shelf (flat below 28Hz)? What shape do you need? A narrow peak, or compensation for driver roll off starting much higher?

That's a lot of boost with "only" 150W available. That gets you to about 10W on the rest of the program before you run out of amp at 28 Hz. Probably enough for home use but wanted to make you aware of the issue.

One of the best resources for active filters is Active Filters

Would a Linkwitz transform work for you? It's pretty much the stnadard way fo compensating for a driver's rolloff. Rod Elliot has boards available. Linkwitz Transform Subwoofer Equaliser You might consider not goig with the full boost your anechoic simulation recommends. You'll get some room gain and corner placement gets you a few dB, so if you use the anechoic boost you'll be bass heavy. Less boost also gives you a bit more headroom.

A 12" driver might have a tough time producing significant output down to 28 Hz. If your room is big you may find yourself wishing for more subwoofers. Multiple 12" subs would be nice if you can afford it.
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