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10hz- 104.2db
12.5- 108.2

Of course these are 2m ground plane measurements outdoors. Just imagine what it'll be in room! These numbers also follow closely to what I modeled in WinISD. Pretty close to a Gjallarhorn's output in the 25hz and below area and putting out more in the 30hz and above.
My guess, in a 7500^3 room, in my opinion, you're going find the 10Hz and 12.5Hz is going disappear. I find that's where the rumble and roll is; the tactile sensation.

Am I off base with that assessment? My experience is limited to what I've read and learned along the way with REW, three Klipsch subs and a pair of FV15HPs. I don't do DIY. Those FTW 21s will move a lot of air, but will that be enough for 7500^3 in the lower octave?

In room, what are your expectations at 10Hz and 12.5Hz?
 

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I'm not sure what the output at 10hz will be. I would assume though that I would need 4 to hit reference at 10hz. It's really hard to say. I'm not to worried myself about the ULF output as much as I am hitting reference in my room at say 18-20hz. I don't think I'll have a problem with that.
 

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I'm not sure what the output at 10hz will be. I would assume though that I would need 4 to hit reference at 10hz. It's really hard to say. I'm not to worried myself about the ULF output as much as I am hitting reference in my room at say 18-20hz. I don't think I'll have a problem with that.
My reason for worrying about hitting reference in the lower octaves is, when the movie sound tracks are measured, there's a surprising amount of ULF in the recording that's not being reproduced. If one can't hear the difference they sure can feel it as the whole room starts to breath when the pulse wave goes through the room. Yeah baby! :D

Money limited us to about 11Hz and if I had the budget, which we clearly do not, I would be pushing for a pair of Triax subs or JTR Captivator S2s, either of which will easily break the <10Hz barrier. So much money for so little. In the honest end, working with you and your comments, I guess a lot of my desire is ego based, just to say I can go there. Our system will easily do reference at 16Hz and what we have is far better than what one will experience in a theater.

Greed is a terrible sin to waste.

...:p

Good luck with your DIY project and I'll keep my fingers crossed that when finished, you'll get what you want in that big room of yours.
 

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I'm not sure what the output at 10hz will be. I would assume though that I would need 4 to hit reference at 10hz. It's really hard to say. I'm not to worried myself about the ULF output as much as I am hitting reference in my room at say 18-20hz. I don't think I'll have a problem with that.

I agree with you about staying more focused on the 18-20Hz stuff. Most people with strong low frequency output seem to concur that most of the tactile feel/shake/rumble happens 16Hz plus. There are scenes that include plenty of output below 16 Hz, but I think that people are feeling the 16+ and not the 15 and below.

I actually did a single frequency sweep that played tones starting at 1 Hz and going up to 30 Hz. Lots of cone movement starting below 10Hz. At 15 Hz...nada..at 16....boom, all the rumbling started.

Theres a DIY guy on AVS that measured 115 dB at 15 Hz and barely noticed anything...which is why he went with ported subs.
 

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I agree with you about staying more focused on the 18-20Hz stuff. Most people with strong low frequency output seem to concur that most of the tactile feel/shake/rumble happens 16Hz plus.
You leave out the part about "nearfield" placement having a +10dB advantage over subs placed ten feet away.

IIRC, basshead81 has all three of his ported subs placed nearfield.

(once one has gone nearfield, there's no going back)
 
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