Sub sonic limitations

[dem beats 1,223]

I think this will be the best place to post this as I am not ready to buy anything for a bit, but I do want to know what to buy when I am and be better informed.

What I would like to know is what limits us from getting down to verry low Hz in speakers with any real force. I know the basic design doesn't allow us to get to .0000001hz mechanicaly and such but what factors contribute to this and what should someone look for in trying to acheive this?

I don't think I am asking the question correctly because I don't have a strong grasp on the lingo enough to use it properly, but I usualy understand technical jargon when used or I can look it up, so I'll give you the application.

I am looking at building a HT and a car system that will really rumble, and I want to do it myself. I know I can buy pre made set ups, especialy for HT but I want to try my hand at fabricating something on that scale to warm me up for maybe building my own speaker enclosures at some point. I'm also just flat out interested in anything science, sound, turbine-jet engines anything.

So when looking for the perfect drivers to use to pressurize a room at low HZ what are the main things to take into consideration for getting low with flatter responce with higher pressure levels? If you were to go into creating your own suber sub what woudl you look for in a driver/enclosure etc?

[Thumpper 266]

frequencies below 8hz are beyond the potential of a conventional woofer

I have actually experienced a 1hz tone with a low frequency fan set up on

a home theater system..I watched Jurassik Park with 2 of these things hooked up

and it felt like an Earthquake at times

here is a link

http://www.eminent-tech.com/RWbrochure.htm

Edited March 21, 2008 by Thumpper

[dem beats 1,223]

Yeah I know of this rotary fan type woofer. That's a lot of lewt to throw down for it. Doesn't answer my question but it's great info anyway.

I have been into HT for a while and that gets brought up everyoen once and a while. I know some guy made a rotary woofer for his car too. There was a thread somewhere. Made his own baffles and blade and used servos to rotate it... verry cool.

That doesn't really work out for me though because that machine will only play about 0-20 hz well from my understanding. It would be awesome to have don't get me wrong especialy if the SPL can get up there as they claim. I'm sure it could rearrange faces lol.

Edited March 21, 2008 by dem beats

[DevilDriver 28]

Why are you wanting performance slower than the speed of sound?

For infrasonic sound (below 20 Hz), the big thing you need to look for is just raw displacement: move a lot of air. Two ways to increase displacement: better coupling (ie. more surface area) or greater amplitude of oscillation (ie. more throw). To gain surface area, you want a large cone and anything else that will help, including ports, passive radiators, or clever loading techniques. To gain throw, that's a function of the motor and suspension and not always simple or inexpensive.

So assuming we have the drivers and enclosure to do it, you need to make everything else is in place. You'll find a lot of electronics have rolloff in the infrasonic range, especially down below 10 Hz. And once you have all that in place, you have to make sure your room can take it. I can tell you that just a single 15" LMS-Ultra has been brutal on my basement....to the point that I have unhooked it for now.

[JimJ 11]

frequencies below 8hz are beyond the potential of a conventional woofer

Curious as to why that is?

[dem beats 1,223]

frequencies below 8hz are beyond the potential of a conventional woofer

Curious as to why that is?

Agreed, I've been looking for that answer.

[dem beats 1,223]

Why are you wanting performance slower than the speed of sound?

For infrasonic sound (below 20 Hz), the big thing you need to look for is just raw displacement: move a lot of air. Two ways to increase displacement: better coupling (ie. more surface area) or greater amplitude of oscillation (ie. more throw). To gain surface area, you want a large cone and anything else that will help, including ports, passive radiators, or clever loading techniques. To gain throw, that's a function of the motor and suspension and not always simple or inexpensive.

So assuming we have the drivers and enclosure to do it, you need to make everything else is in place. You'll find a lot of electronics have rolloff in the infrasonic range, especially down below 10 Hz. And once you have all that in place, you have to make sure your room can take it. I can tell you that just a single 15" LMS-Ultra has been brutal on my basement....to the point that I have unhooked it for now.

I desperately wanted to scoop up in the LMS before it went away. When I build my HT room, that is when I buy a house (this year hopefully), and either build from scratch or turn a room into my HT room it will be dedicated, and ready for the challeneg of that kind of power.

I have heard the old addage of "there is no replacement for displacement" but I didn't quite know if it was that true, and the more subs you have unless they are all verry linear the more you would have to EQ them correct? And after a certain point, 8 18's in a room per sey, it would be like being in an enclosure instead of an enclosure in a room correct? I really am interested in the SDX15, and figure a big array of those could get my goal, but that could present many problems power being one. I could get a group discount for buying all of them for just myself and trhow on ein the truck too.

Thanks DD for all the input, and if you ever feel that LMS is just collecting dust.....

hehe