Need subs that will do 20hz-40hz

Re: Need subs that will do 20hz-40hz

Eric Cagle said:
Let me know how that goes. I don't have to be flat to 20hz but I do need to get well below 30hz with some juice left. There is a lot of stuff down there in some of the tunes that I just begin to feel where my system runs out of gas. The lower down I can reach the less the guys tend to push the system.
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Josh Ricci’s Gjallerhorn at 2 meter, ground plane, outdoors measures:
10hz 90.2db
12.5hz 105.2db
16hz 118.3db
20hz 122db
25hz 124.9db
31.5hz 125.8db
40hz 128.4db
50hz 127.2db
63hz 130.2db
80hz 130.9db
100hz 131.1db
125hz 123.6db

Add 6 dB to those figures for a one meter equivalency, and a bit more for indoor corner loading.

At 1000HZ, adding 10 dB SPL sounds twice as loud, while at 20 HZ adding only 5 dB SPL sounds twice as loud.
Although Hoffman's iron law prevents most P.A. subs from attempting much below 30-40Hz, if a box is designed for output below that, a little goes a longer way, the Gjallerhorn at 128 dB (one meter) 20Hz is seriously seismic.

As well as SPL, Josh has done distortion and impulse response tests on many LF designs:
Data-Bass

That the Gjallerhorn can do the output listed above with (relative for LF) very low distortion is quite impressive.

Art
 
Re: Need subs that will do 20hz-40hz

OK - someone wanted to know what happened regarding a demo that was held in a church here in St. Petey. The clients from Dallas flew in to check out various things and it seems that they have both large and small niches to fill. For serious subs this Chimera thing really is a contender and it indeed goes well into the 20's. XS-21 Chimera 21" Bass Horn - Ramsdell Pro Audio Products What it needs is the NEO 21 and something like a Crown Xti6002 in mono bridge to power it. It's way more sub than I will ever need but it would be fun to hear 4 of them outside with proper power and NEO's in them.

To give some perspective regarding output - 2 of the standard ceramic types were used for a country concert in a park and it seemed to match up pretty well with 8 full sized Vertecs per side at moderate volume - no other subs were used or needed. They were using a Powersoft to drive them. I wasn't there so this is second hand opinions from 2 different sources.
 
Re: Need subs that will do 20hz-40hz

Ivan Beaver said:
Bring one by the shop and we can listen to the difference as well.
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I'll bring a couple in a few weeks when I bring you the old amp and literature for your display. The QMS's really don't compare to the modern Danley products. They do 50hz really well though. I rented Kemper's TH212's yesterday for a gig and center clustered all 4 (laying flat 2 high with all horn openings together) on a concrete floor butting up to a 4 foot concrete stage in an amphitheater. That was fun. They outran my Fussion rig by a good margin in that configuration with the floor and wall loading.
 
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Re: Need subs that will do 20hz-40hz

Art,
The Gjallerhorn looks like a beast of a sub and actually pretty flat in that 20-40hz octave. I am crossing at 85hz to the mid high cabinets so they would work as my only subs and eliminate the need for extra cabinets and amps for 40-85hz. I would consider having a couple of them built (way beyond what I would attempt) and giving them a try. I am not currently a member of the diyAudio forum but am willing to join. Is that a plan that Josh will share or sell?

Gene and Scott,
I am looking into both af those. I am very familiar with the Ramsdell stuff now that I have researched it a bit. Still have not heard any of the 21" subs but I am planning to go to St Petersburg in the next few weeks when one of my gigs gets me close to there.

Thanks everyone for the input!
-Eric
 
Re: Need subs that will do 20hz-40hz

Aleš - I didn't know this either even though it's been staring us in the face for years in the equal loudness contour plot.

Nevertheless, the problem remains that far more output is required at the lowest frequencies to make humans happy, so the fact that lower increments in SPL achieve a given percentage increase in perceived output doesn't help very much. :)

EqualLoudnessContours.png
 
Re: Need subs that will do 20hz-40hz

Right, it's a question of what intensities you're starting and ending at. A 5 db change from 45 to 50 db should not make a hill of beans difference as they are both below audibility. Down in these frequencies there is a transition between hearing and 'feeling' and I've often wondered how that affects these perception curves. The Fletch-Munson testing has all been done with headphones, right?
 
Re: Need subs that will do 20hz-40hz

Eric Cagle said:
Art,
The Gjallerhorn looks like a beast of a sub and actually pretty flat in that 20-40hz octave. I am crossing at 85hz to the mid high cabinets so they would work as my only subs and eliminate the need for extra cabinets and amps for 40-85hz. I would consider having a couple of them built (way beyond what I would attempt) and giving them a try. I am not currently a member of the diyAudio forum but am willing to join. Is that a plan that Josh will share or sell?

-Eric
Click to expand...
Josh has said in the diyAudio Gjallerhorn thread he will share the detailed plans, though the thread has enough info to build from already. I think Josh is in your area and had a local cabinet builder build his cabinets.
 
Re: Need subs that will do 20hz-40hz

Ales Dravinec said:
Huh, I did not know that (ashamed). ... Thanks Art

w/r
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I learned that at 20 HZ adding only 5 dB SPL sounds twice as loud while reading about wind turbines.

Wind turbines put out ELF, the older designs were worse. Because of differing perception, some people would be "bugged" by the ELF, while others would not perceive it- a 6 dB difference in a person's LF perception would be the same as moving from 1000 meters away from the generator to 500 meters.

One difference in the ELF from a wind generator and a speaker is much of the generator's ELF output is transmitted through the earth, the composition of soil and rocks can make a large difference in the rate of level drop.

Makes me recall an outdoor "Live" show last century, one tune with a fast heavy backbeat got the punters all pogoing in unison. Monty Lee Wilkes was mixing, the bass had been fairly heavy, but now we could feel it !We looked at each other with that "what the fuck" look as the FOH riser started moving with the beat, the rack and console literally were moving about an inch, the feeling was way heavier than standing next to a freight train.

The ground had become saturated by heavy rains over the last week (and day of show), the punter's pogo dance was being hydraulically transmitted from near the stage (near a river) to the house mix about 100 feet back.

Maybe Drew should look into a water bladder over the dance floor covered with plywood with butt shakers attached for sub bass :^).
 
Re: Need subs that will do 20hz-40hz

Art Welter said:
Josh has said in the diyAudio Gjallerhorn thread he will share the detailed plans, though the thread has enough info to build from already. I think Josh is in your area and had a local cabinet builder build his cabinets.
Click to expand...

That is a pretty fascinating design. I had not planned on anymore DIY cabinets but that one has got me thinking. Thanks for the tip.
 
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