Labsub or HLa at 17Hz?

[electroaudio]

I have been asked by a theatregroup to do 17Hz but how well does the labsub do 17Hz and what power can it be fed?
I dont know how the signal is shaped and for how long the signal will be on.
Does anyone have any experience of anything like this?

The other alternative would be JBL HLA subs, but i dont like the idea of frontloaded that low at any serious soundpressure.
http://www.jblpro.com/catalog/support/getfile.aspx?docid=233&doctype=3

 

[jbell]

labsub is a PA sub, aka 40hz and higher. 17hz would require an incredibly long path for a FLH.

By chance are you looking for something like this??

http://home.comcast.net/~jhidley/Subwoofers/index3.html

 

[simon5]

For 17 Hz, I'd recommend huge ported enclosures or a Tapped Horn.

 

[electroaudio]

There wont be any newbuilds for this , so these two are the only alternatives at hand.


From some tests with hornresp. It seems that the labsub can do any frequency limited to 225 watts , but can handle more than that both below and above the 32,5Hz resonance...

Livetests with real amps infront of the theatredirector will be done tomorrow...

So, what power is it possible to run the labsubs on without burning the coil "with almost DC"? Will it handle 400W safely?

 

[jbell]

The problem is a lab sub at 17hz, is basically a small sealed box direct radiator, that just happens to go through a horn path.

If you take any program that can model a small sealed box with a lab12 driver -- that's what you should get. (which is what hornresp shows)


now, if you had some 4x8 sheets of ply, and could add about 8' of length to your labs (following the horn flare) you might have something.

 

[Tom Danley]

Hi
If you find products that have half space measurements, you can compare them to these, some boxes I designed that are usable at 17Hz.
Warning I am the manufacturer but the measurements are real and easily repeatable.
The Imax cinema at Navy pier in Chicago has for of the first boxes for lf.

http://www.danleysoundlabs.com/pdf/TH 50 Spec Sheet.PDF

http://www.danleysoundlabs.com/pdf/DTS 20 Spec Sheet.PDF

http://www.danleysoundlabs.com/pdf/SPUD intro.pdf

Best,
Tom Danley

 

[Don Snyder]

Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?

 

[Don Snyder]

If you need a 17 Hz sine wave sound, the above cabinet can be modified (stretched) to put out 115 dB at 1 meter.

This could be built for less than $300 USD.

 

[electroaudio]

The problem is a lab sub at 17hz, is basically a small sealed box direct radiator, that just happens to go through a horn path.

If you take any program that can model a small sealed box with a lab12 driver -- that's what you should get. (which is what hornresp shows)


now, if you had some 4x8 sheets of ply, and could add about 8' of length to your labs (following the horn flare) you might have something.

(Yes you are correct, it somehow slipped my mind when i was thinking of the HLAs)

If it was possible under these circumstances, i would definately build some extensionflares or better yet start out fresh with a TH.

Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?

Danleys constructions are well known and has been discussed for several years, but they arent aviable over here.

I dont actually know how much i need, the theatredirector dont have a clue...
And since i dont know what kind of material they are going to play so who knows if 17Hz is important at all.
-They just asked for a 17Hz demo tomorrow morning, a few hours from now...

So will it be safe to run that demo with 400W and a narrow notch at 32,5Hz? can i maybe use more than 400W safely?

 

[electroaudio]

If you need a 17 Hz sine wave sound, the above cabinet can be modified (stretched) to put out 115 dB at 1 meter.

This could be built for less than $300 USD.

Thanks Don!
I will save those drawings for the next time.

 

[jbell]

I'm sure power compression is setting in well before 400watts. Play it safe, keep it to 200watts, and FIND A CORNER for your labsub, and face it into it, so that it 'kinda' continues the flare around the corner, or even better find a sheet of ply, and set it up ala K-horn.

A corner is your best friend at 17hz, and your only hope of getting respectable output.

 

[MaVo]

If they demand 17hz and didnt specify the intended material, chances are that they have no clue what 17hz sounds like. There are stories floating around the net, of low tones invoking strange feelings like religious experiences and ghost seeing. I kinda doubt them, since i never experienced such things. From my experience, lower than 20hz is only a very subtle feeling of pressure, hardly recognisable at all - of course that will depend on the spl and i never heard such tones very loud.

Apart from this sceptical attitude, i would say, Toms designs will be the best (most cost effective) solution you can get for this. Either as a diy tapped horn or buying the real thing, which i would do, if i wanted results and no experiments. For diy, Dons lab12 design looks like an easy thing to do, since everything is planned, all you need to do is put the parts together.

Even a corner wont load a lab to 17hz, but still give the eigth space output bonus. For 17hz, a labsub is about as good as the closed volume behind the driver without the horn in front of it, so one could safe alot of space and put the lab12 in a closed box, but that will never be enough spl for 17hz in a big room.

 

[technofreak]

Actually, the task is fairly easy - take those LAB12-s and stick 2 of them in push-pull configuration in a 350 litres ported enclosure tuned to 18 Hz. Build 4 to 8 of these boxes, and you've got your 17 Hz at a reasonable SPL (>120 dB). Use steep high-pass at 16 Hz.

 

[Clarkcr]

Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?

If you need a 17 Hz sine wave sound, the above cabinet can be modified (stretched) to put out 115 dB at 1 meter.

This could be built for less than $300 USD.

Mad props Don! Thanks for the data.

Can these dimensions be stretched and increased proportionately to accomodate a larger transducer? Thereby increasing db and flattening out the response? I find it hard to believe that a cute little 12" transducer would be able to create this level of sound pressure.

What would happen if a 15" or18" was used in this double folded tapped horn? This may be the answer I have been looking for.

Thanks again for posting.

Chris

 

[Don Snyder]

<<Can these dimensions be stretched and increased proportionately...>>

Air doesn't scale, that's why we use Hornresp to simulate these cabinets.

17 Hz and 115 dB at 1 meter is possible, but it's a one trick pony. As simulated,
it would only work at 17 Hz, or above 25 Hz. It would blow up at 15 or 19 Hz.

If you need something a little larger, check-out Tom Danley's Matterhorn.

http://www.youtube.com/watch?v=o36Kp6veJ6c

 

[shyguy]

Tom's DTS is an excellent solution to your problem. The closest
thing that the diyaudio forum has produced is a double folded
tapped horn as designed by MAVO and folded by me. With a total
path length of 5.5 meters, Hornresp says it's down -5dB at 17 Hz.

How much power do you need?

Hi Don

Noob here, I saw a few of your posts about the lab12 & your comments @ Parts-Express, which design did you use & what is your final opinon on the lab12 in a tapped horn configuration?

Thanks

 

[Dr_EM]

The 18Hz tappen horn here should do?:

http://www.cowanaudio.com/