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-   -   Sonotube sub for PA use? (First post) (http://www.diyaudio.com/forums/pa-systems/159121-sonotube-sub-pa-use-first-post.html)

Racket Scientist 20th January 2010 11:12 PM

Sonotube sub for PA use? (First post)
 
In 2 bands, mostly for fun. I've been looking around at adding some subs to the system at some point, and I've become fascinated by sonosubs. Anybody using these for PA? I ran across a guy selling some BFM folded horns (Titans) and have been tempted by that, but was thinking of something I could both use as subs for my stereo (in a large basement) as well as for the PA. I'm also thinking I can do sonosubs cheaper. Thoughts?

By the way - first post here. Thanks for putting up such a cool forum.

jbell 21st January 2010 12:06 AM

Personally I think you should define your requirements first. (how loud, how low, how big) before you define the sub cabinet materials.

Sonotube just happens to be one material of many to build a cabinet.

PA equipment takes a beating, and needs to be stacked/unstacked on a regular basis. Round sonotube and the covering you choose to put on it may not stand up to this.

I have built many sonotubes, but they all are in low impact environments.

Racket Scientist 21st January 2010 05:04 AM

Thats a good point - I hadn't really thought about the durability, just that the sonosubs would be definitely lighter than folded wooden horns. I'm also concerned about use outdoors or for large venues - my understanding is that the horns "throw" better and give more balanced coverage from the front to the back of the audience. In a medium sized room I think sonosubs would work fine. I understand that sonosubs are at an efficiency disadvantage to go loud when compared to horns, just not sure how much. On another forum, the advice has been just to go with a 18" ported cab except for outdoor settings - my thought is that sonosubs with a good 12 or 15" speaker would probably compare well to those in weight and output; probably not so much with durability. As far as how loud, as loud as possible (thats what volume knobs are for). As far as how low, I'd want to go down low enough to be useful with my stereo at home, but be pretty efficient in the 40 to 100 Hz range for PA use. (Anybody use interchangable ports?) As far as how big, the more portable the better, but they could be pretty big to optimize the other factors.

davygrvy 21st January 2010 06:26 AM

A sealed or ported cab, whether sonotube or not, can give excellent results for HT. Bring that same cab to a gymnasium sized room or outdoors and you'll see it just won't make the noise you thought it would. It has to do with pressure confinement and boundary loading.

For PA use, 40Hz and up is all you need. For HT, drop that an octave. If you like the BFM horns, consider a TubaHT with a removable chamber door. Keep the chamber closed at home for the extra drop and remove it for PA to get some extra 60Hz.

But this cab is like f'in huge.

Racket Scientist 21st January 2010 01:06 PM

Could you "bring a wall" with you - have some large flat surfaces to erect a "corner" around a ported cab/sonosub to create some boundary loading?

jbell 21st January 2010 01:23 PM

it's not practical to bring a 40' wall with you...

I would look into 'small' folded horns and use as many of them as you need. (I'll 2nd what davy said: a THT is HUGE)

Davy uses autotuba's with HL10c's, I've built several iterations of dual and single driver mcm FLH's http://www.diyaudio.com/forums/subwo...ml#post1977445

If you want a BFM design, a dual driver T18 (please add 12mh inductor for indoor use for flat response) is really good in the output per cubic inch of cabinet.

Tapped horns have good directionality, so a wall isn't needed, many good threads on good pa TH's. (but most are too big for the living room.)

There are some good threads on very small mcm tapped horns that are only about 40 liters per driver... about 8 of them would be great for outdoor, and just use 1 or 2 for indoor use. At $25 per driver that might be a good modular bet for you.

BTW.. one last concern I have for sonosubs for PA duty. My little brother was using his HSU sonosub for a dance recital in a 250 seat auditorium. They needed someone to sit on the sonosub, because IT was dancing around the concrete floor. Sonosubs weigh very little.

dangus 22nd January 2010 04:45 AM

I've thought about sonotube subs, after hauling dual 18" ported cabinets up stairs to 2nd or 3rd floor lofts or down forest trails for parties. They'd be awkward to pack, wouldn't work as speaker stands, and tubes big enough to hold 15" or 18" woofers weren't easy to find. I bought a hand-truck instead.

Now, sonotube might work for a bandpass sub; it should be easier to locate a port compared to a bass-reflex. This just might give the best thump per pound, if you're pragmatic and tune it for where the kick drum is rather than trying for deep bass.

head_unit 22nd January 2010 10:28 PM

Quote:

Originally Posted by Racket Scientist (Post 2056214)
Could you "bring a wall" with you - have some large flat surfaces to erect a "corner" around a ported cab/sonosub to create some boundary loading?

What jbell means is that the wall you would have to bring would need to be very long and very tall, or it becomes smaller than the bass waves and will not reinforce them.

On the other hand, multiple cabinets will load each other kinda like a wall. That's one reason concert arrays have multiple cabinets.

Look at http://www.billfitzmaurice.com
he wrote some articles for Speaker Builder or maybe it was Audio Xpress (audioXpress - Home) by then. He was designing compact high output folded horns for PA use with quite good results.

In theory, home and PA should be similar, except PA doesn't need to go below 40 as mentioned. But somehow they are different. One big factor is PA will often overload more than home, so usually you want more rugged drivers.

Another difference is that for PA, you don't want drivers in a common cabinet. Otherwise if one blows out, it can unload the other and blow it out as well. The drivers should be in separate cabinets or separate sub-enclosures within the main cabinet.

Similar to both, if you do a ported design, you must be sure the port is huge. Otherwise the airflow will just choke off and you'll lose sound pressure. Interestingly, research at JBL indicated that flaring the ports only helps sound pressure at more moderate SPL levels. At high SPL, the port air just jets in and out due to high speed.


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